1
|
Whitaker W, Ghosh D, Malakar P, Karras G, Orr-Ewing AJ. Femtosecond to Microsecond Observation of Photochemical Pathways in Nitroaromatic Phototriggers Using Transient Absorption Spectroscopy. J Phys Chem A 2024; 128:5892-5905. [PMID: 38988292 DOI: 10.1021/acs.jpca.4c02482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/12/2024]
Abstract
The synthetic accessibility and tolerance to structural modification of phototriggered compounds (PTs) based on the ortho- nitrobenzene (ONB) protecting group have encouraged a myriad of applications including optimization of biological activity, and supramolecular polymerization. Here, a combination of ultrafast transient absorption spectroscopy techniques is used to study the multistep photochemistry of two nitroaromatic phototriggers based on the ONB chromophore, O-(4,5-dimethoxy-2-nitrobenzyl)-l-serine (DMNB-Ser) and O-[(2-nitrophenyl)methyl]-l-tyrosine hydrochloride (NB-Tyr), in DMSO solutions on femtosecond to microsecond time scales following the absorption of UV light. From a common nitro-S1 excited state, the PTs can either undergo excited state intramolecular hydrogen transfer (ESIHT) to an aci-S1 isomer within the singlet state manifold, leading to direct S1 → S0 internal conversion through a conical intersection, or competitive intersystem crossing (ISC) to access the triplet state manifold on time scales of (1.93 ± 0.03) ps and (13.9 ± 1.2) ps for DMNB-Ser and NB-Tyr, respectively. Deprotonation of aci-T1 species to yield triplet anions is proposed to occur in both PTs, with an illustrative time constant of (9.4 ± 0.7) ns for DMNB-Ser. More than 75% of the photoexcited molecules return to their electronic ground states within 8 μs, either by direct S1 → S0 relaxation or anion reprotonation. Hence, upper limits to the quantum yields of photoproduct formation are estimated to be in the range of 13-25%. Mixed DMSO/H2O solvents show the influence of the environment on the observed photochemistry, for example, revealing two nitro-S1 lifetimes for DMNB-Ser in a 10:1 DMSO/H2O mixture of 1.95 ps and (10.1 ± 1.2) ps, which are attributed to different microsolvation environments.
Collapse
Affiliation(s)
- William Whitaker
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Deborin Ghosh
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Partha Malakar
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Gabriel Karras
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| |
Collapse
|
2
|
Lau N, Ghosh D, Bourne-Worster S, Kumar R, Whitaker WA, Heitland J, Davies JA, Karras G, Clark IP, Greetham GM, Worth GA, Orr-Ewing AJ, Fielding HH. Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution. J Am Chem Soc 2024; 146:10407-10417. [PMID: 38572973 PMCID: PMC11027148 DOI: 10.1021/jacs.3c13826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 03/09/2024] [Accepted: 03/11/2024] [Indexed: 04/05/2024]
Abstract
Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of brown carbon include biomass burning, forest fires, and residential burning of biofuels, and an important secondary source is photochemistry in aqueous cloud and fog droplets. Nitrobenzene is the smallest nitroaromatic molecule and a model for the photochemical behavior of larger nitroaromatic compounds. Despite the obvious importance of its droplet photochemistry to the atmospheric environment, there have not been any detailed studies of the ultrafast photochemical dynamics of nitrobenzene in aqueous solution. Here, we combine femtosecond transient absorption spectroscopy, time-resolved infrared spectroscopy, and quantum chemistry calculations to investigate the primary steps following the near-UV (λ ≥ 340 nm) photoexcitation of aqueous nitrobenzene. To understand the role of the surrounding water molecules in the photochemical dynamics of nitrobenzene, we compare the results of these investigations with analogous measurements in solutions of methanol, acetonitrile, and cyclohexane. We find that vibrational energy transfer to the aqueous environment quenches internal excitation, and therefore, unlike the gas phase, we do not observe any evidence for formation of photoproducts on timescales up to 500 ns. We also find that hydrogen bonding between nitrobenzene and surrounding water molecules slows the S1/S0 internal conversion process.
Collapse
Affiliation(s)
- Nicholas
A. Lau
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Deborin Ghosh
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | | | - Rhea Kumar
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - William A. Whitaker
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Jonas Heitland
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Julia A. Davies
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Gabriel Karras
- Central
Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Ian P. Clark
- Central
Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Gregory M. Greetham
- Central
Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Graham A. Worth
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Helen H. Fielding
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| |
Collapse
|
3
|
He Y, Collado JT, Iuliano JN, Woroniecka HA, Hall CR, Gil AA, Laptenok SP, Greetham GM, Illarionov B, Bacher A, Fischer M, French JB, Lukacs A, Meech SR, Tonge PJ. Elucidating the Signal Transduction Mechanism of the Blue-Light-Regulated Photoreceptor YtvA: From Photoactivation to Downstream Regulation. ACS Chem Biol 2024; 19:696-706. [PMID: 38385342 PMCID: PMC10949197 DOI: 10.1021/acschembio.3c00722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/25/2024] [Accepted: 02/12/2024] [Indexed: 02/23/2024]
Abstract
The blue-light photoreceptor YtvA from Bacillus subtilis has an N-terminal flavin mononucleotide (FMN)-binding light-oxygen-voltage (LOV) domain that is fused to a C-terminal sulfate transporter and anti-σ factor antagonist (STAS) output domain. To interrogate the signal transduction pathway that leads to photoactivation, the STAS domain was replaced with a histidine kinase, so that photoexcitation of the flavin could be directly correlated with biological activity. N94, a conserved Asn that is hydrogen bonded to the FMN C2═O group, was replaced with Ala, Asp, and Ser residues to explore the role of this residue in triggering the structural dynamics that activate the output domain. Femtosecond to millisecond time-resolved multiple probe spectroscopy coupled with a fluorescence polarization assay revealed that the loss of the hydrogen bond between N94 and the C2═O group decoupled changes in the protein structure from photoexcitation. In addition, alterations in N94 also decreased the stability of the Cys-FMN adduct formed in the light-activated state by up to a factor of ∼25. Collectively, these studies shed light on the role of the hydrogen bonding network in the LOV β-scaffold in signal transduction.
Collapse
Affiliation(s)
- YongLe He
- Department
of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
| | | | - James N. Iuliano
- Department
of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
| | - Helena A. Woroniecka
- Department
of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
| | - Christopher R. Hall
- Central
Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0QX, U.K.
| | - Agnieszka A. Gil
- Department
of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
| | | | - Gregory M. Greetham
- Central
Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0QX, U.K.
| | - Boris Illarionov
- Institut
für Biochemie und Lebensmittelchemie, Universität Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
| | - Adelbert Bacher
- Institut
für Biochemie und Lebensmittelchemie, Universität Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
- TUM School
of Natural Sciences, Technical University
of Munich, 85747 Garching, Germany
| | - Markus Fischer
- Institut
für Biochemie und Lebensmittelchemie, Universität Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
| | - Jarrod B. French
- Department
of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
- The
Hormel Institute, University of Minnesota, Austin, Minnesota 55912, United States
| | - Andras Lukacs
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
- Department
of Biophysics, Medical School, University
of Pecs, Szigeti ut 12, 7624 Pecs, Hungary
| | - Stephen R. Meech
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
| | - Peter J. Tonge
- Department
of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
| |
Collapse
|
4
|
Smith HE, Mackenzie AM, Seddon C, Mould R, Kalampouka I, Malakar P, Needham SR, Beis K, Bell JD, Nunn A, Botchway SW. The use of NADH anisotropy to investigate mitochondrial cristae alignment. Sci Rep 2024; 14:5980. [PMID: 38472304 DOI: 10.1038/s41598-024-55780-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 02/26/2024] [Indexed: 03/14/2024] Open
Abstract
Life may be expressed as the flow of electrons, protons, and other ions, resulting in large potential difference. It is also highly photo-sensitive, as a large proportion of the redox capable molecules it relies on are chromophoric. It is thus suggestive that a key organelle in eukaryotes, the mitochondrion, constantly adapt their morphology as part of the homeostatic process. Studying unstained in vivo nano-scale structure in live cells is technically very challenging. One option is to study a central electron carrier in metabolism, reduced nicotinamide adenine dinucleotide (NADH), which is fluorescent and mostly located within mitochondria. Using one and two-photon absorption (340-360 nm and 730 nm, respectively), fluorescence lifetime imaging and anisotropy spectroscopy of NADH in solution and in live cells, we show that mitochondria do indeed appear to be aligned and exhibit high anisotropy (asymmetric directionality). Aqueous solution of NADH showed an anisotropy of ~ 0.20 compared to fluorescein or coumarin of < 0.1 and 0.04 in water respectively and as expected for small organic molecules. The anisotropy of NADH also increased further to 0.30 in the presence of proteins and 0.42 in glycerol (restricted environment) following two-photon excitation, suggesting more ordered structures. Two-photon NADH fluorescence imaging of Michigan Cancer Foundation-7 (MCF7) also showed strong anisotropy of 0.25 to 0.45. NADH has a quantum yield of fluorescence of 2% compared to more than 40% for photoionisation (electron generation), when exposed to light at 360 nm and below. The consequence of such highly ordered and directional NADH patterns with respect to electron ejection upon ultra-violet (UV) excitation could be very informative-especially in relation to ascertaining the extent of quantum effects in biology, including electron and photonic cascade, communication and modulation of effects such as spin and tunnelling.
Collapse
Affiliation(s)
- Holly E Smith
- UKRI, STFC, Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK
| | - Alasdair M Mackenzie
- UKRI, STFC, Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK
| | - Chloe Seddon
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
- Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Rhys Mould
- School of Life Sciences, Research Centre for Optimal Health, University of Westminster, London, W1W 6UW, UK
| | - Ifi Kalampouka
- School of Life Sciences, Research Centre for Optimal Health, University of Westminster, London, W1W 6UW, UK
| | - Partha Malakar
- UKRI, STFC, Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK
| | - Sarah R Needham
- UKRI, STFC, Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK
| | - Konstantinos Beis
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
- Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxfordshire, OX11 0FA, UK
| | - Jimmy D Bell
- School of Life Sciences, Research Centre for Optimal Health, University of Westminster, London, W1W 6UW, UK
| | - Alistair Nunn
- School of Life Sciences, Research Centre for Optimal Health, University of Westminster, London, W1W 6UW, UK
| | - Stanley W Botchway
- UKRI, STFC, Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, UK.
| |
Collapse
|
5
|
Jonušas M, Bournet Q, Bonvalet A, Natile M, Guichard F, Zaouter Y, Georges P, Druon F, Hanna M, Joffre M. Chirped pulse upconversion for femtosecond mid-infrared spectroscopy at 100 kHz. OPTICS EXPRESS 2024; 32:8020-8029. [PMID: 38439469 DOI: 10.1364/oe.515291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 02/06/2024] [Indexed: 03/06/2024]
Abstract
We demonstrate that chirped pulse up-conversion (CPU), a method routinely used with systems based on 1-kHz Titanium:Sapphire lasers, can be extended to a repetition rate of 100 kHz with an Ytterbium diode-pumped femtosecond amplifier. Individual mid-infrared spectra can thus be measured directly in the near infrared using a fast CMOS linescan camera. After an appropriate Fourier processing, a spectral resolution of 1.1 cm-1 is reported, currently limited by our spectrometer. Additionally, we demonstrate the application of CPU to a pump-probe measurement of the vibrational relaxation in carboxy-hemoglobin, and we show that the combination of fast scanning and fast acquisition enables a straightforward removal of pump scattering interference.
Collapse
|
6
|
Hunt NT. Biomolecular infrared spectroscopy: making time for dynamics. Chem Sci 2024; 15:414-430. [PMID: 38179520 PMCID: PMC10763549 DOI: 10.1039/d3sc05223k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 11/24/2023] [Indexed: 01/06/2024] Open
Abstract
Time resolved infrared spectroscopy of biological molecules has provided a wealth of information relating to structural dynamics, conformational changes, solvation and intermolecular interactions. Challenges still exist however arising from the wide range of timescales over which biological processes occur, stretching from picoseconds to minutes or hours. Experimental methods are often limited by vibrational lifetimes of probe groups, which are typically on the order of picoseconds, while measuring an evolving system continuously over some 18 orders of magnitude in time presents a raft of technological hurdles. In this Perspective, a series of recent advances which allow biological molecules and processes to be studied over an increasing range of timescales, while maintaining ultrafast time resolution, will be reviewed, showing that the potential for real-time observation of biomolecular function draws ever closer, while offering a new set of challenges to be overcome.
Collapse
Affiliation(s)
- Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute, University of York Heslington York YO10 5DD UK
| |
Collapse
|
7
|
Whitaker W, Sazanovich IV, Kwon Y, Jeon W, Kwon MS, Orr-Ewing AJ. Characterization of the Reversible Intersystem Crossing Dynamics of Organic Photocatalysts Using Transient Absorption Spectroscopy and Time-Resolved Fluorescence Spectroscopy. J Phys Chem A 2023; 127:10775-10788. [PMID: 38096377 PMCID: PMC10758116 DOI: 10.1021/acs.jpca.3c04780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 12/01/2023] [Accepted: 12/01/2023] [Indexed: 12/29/2023]
Abstract
Thermally activated delayed fluorescence (TADF) emitters are molecules of interest as homogeneous organic photocatalysts (OPCs) for photoredox chemistry. Here, three classes of OPC candidates are studied in dichloromethane (DCM) or N,N-dimethylformamide (DMF) solutions, using transient absorption spectroscopy and time-resolved fluorescence spectroscopy. These OPCs are benzophenones with either carbazole (2Cz-BP and 2tCz-BP) or phenoxazine/phenothiazine (2PXZ-BP and 2PTZ-BP) appended groups and the dicyanobenzene derivative 4DP-IPN. Dual lifetimes of the S1 state populations are observed, consistent with reverse intersystem crossing (RISC) and TADF emission. Example fluorescence lifetimes in DCM are (5.18 ± 0.01) ns and (6.22 ± 1.27) μs for 2Cz-BP, (1.38 ± 0.01) ns and (0.32 ± 0.01) μs for 2PXZ-BP, and (2.97 ± 0.01) ns and (62.0 ± 5.8) μs for 4DP-IPN. From ground state bleach recoveries and time-correlated single photon counting measurements, triplet quantum yields in DCM are estimated to be 0.62 ± 0.16, 0.04 ± 0.01, and 0.83 ± 0.02 for 2Cz-BP, 2PXZ-BP, and 4DP-IPN, respectively. 4DP-IPN displays similar photophysical behavior to the previously studied OPC 4Cz-IPN. Independent of the choice of solvent, 4DP-IPN, 2Cz-BP, and 2tCz-BP are shown to be TADF emitters, whereas emission by 2PXZ-BP and 2PTZ-BP depends on the molecular environment, with TADF emission enhanced in aggregates compared to monomers. Behavior of this type is representative of aggregation-induced emission luminogens (AIEgens).
Collapse
Affiliation(s)
- William Whitaker
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Igor V. Sazanovich
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Yonghwan Kwon
- Department
of Materials Science and Engineering, Seoul
National University, Seoul 08826, Republic
of Korea
| | - Woojin Jeon
- Department
of Materials Science and Engineering, Seoul
National University, Seoul 08826, Republic
of Korea
| | - Min Sang Kwon
- Department
of Materials Science and Engineering, Seoul
National University, Seoul 08826, Republic
of Korea
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| |
Collapse
|
8
|
Thiré N, Chatterjee G, Pertot Y, Albert O, Karras G, Zhang Y, Wyatt AS, Towrie M, Springate E, Greetham GM, Forget N. A versatile high-average-power ultrafast infrared driver tailored for high-harmonic generation and vibrational spectroscopy. Sci Rep 2023; 13:18874. [PMID: 37914852 PMCID: PMC10620204 DOI: 10.1038/s41598-023-46325-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 10/30/2023] [Indexed: 11/03/2023] Open
Abstract
We report on an ultrafast infrared optical parametric chirped-pulse amplifier (OPCPA), pumped by a 200-W thin-disk Yb-based regenerative amplifier at a repetition rate of 100 kHz. The OPCPA is tunable in the spectral range 1.4-3.9 [Formula: see text]m, generating up to 23 W of < 100-fs signal and 13 W of < 200-fs idler pulses for infrared spectroscopy, with additional spectral filtering capabilities for Raman spectroscopy. The OPCPA can also yield 19 W of 49-fs 1.75-[Formula: see text]m signal or 5 W of 62-fs 2.8-[Formula: see text]m idler pulses with active carrier-to-envelope-phase (CEP) stabilisation for high-harmonic generation (HHG). We illustrate the versatility of the laser design, catering to various experimental requirements for probing ultrafast science.
Collapse
Affiliation(s)
- Nicolas Thiré
- Fastlite, 165 route des cistes, 06600, Antibes, France.
| | - Gourab Chatterjee
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK.
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
| | - Yoann Pertot
- Fastlite, 165 route des cistes, 06600, Antibes, France
| | | | - Gabriel Karras
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - Yu Zhang
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Adam S Wyatt
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Michael Towrie
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Emma Springate
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Gregory M Greetham
- STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Nicolas Forget
- Fastlite, 165 route des cistes, 06600, Antibes, France
- CNRS UMR7010 INPHYNI, 1361 route des Lucioles, 06560, Valbonne, France
| |
Collapse
|
9
|
Donaldson PM, Greetham GM, Middleton CT, Luther BM, Zanni MT, Hamm P, Krummel AT. Breaking Barriers in Ultrafast Spectroscopy and Imaging Using 100 kHz Amplified Yb-Laser Systems. Acc Chem Res 2023; 56:2062-2071. [PMID: 37429010 PMCID: PMC10809409 DOI: 10.1021/acs.accounts.3c00152] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Indexed: 07/12/2023]
Abstract
ConspectusUltrafast spectroscopy and imaging have become tools utilized by a broad range of scientists involved in materials, energy, biological, and chemical sciences. Commercialization of ultrafast spectrometers including transient absorption spectrometers, vibrational sum frequency generation spectrometers, and even multidimensional spectrometers have put these advanced spectroscopy measurements into the hands of practitioners originally outside the field of ultrafast spectroscopy. There is now a technology shift occurring in ultrafast spectroscopy, made possible by new Yb-based lasers, that is opening exciting new experiments in the chemical and physical sciences. Amplified Yb-based lasers are not only more compact and efficient than their predecessors but also, most importantly, operate at many times the repetition rate with improved noise characteristics in comparison to the previous generation of Ti:sapphire amplifier technologies. Taken together, these attributes are enabling new experiments, generating improvements to long-standing techniques, and affording the transformation of spectroscopies to microscopies. This Account aims to show that the shift to 100 kHz lasers is a transformative step in nonlinear spectroscopy and imaging, much like the dramatic expansion that occurred with the commercialization of Ti:sapphire laser systems in the 1990s. The impact of this technology will be felt across a great swath of scientific communities. We first describe the technology landscape of amplified Yb-based laser systems used in conjunction with 100 kHz spectrometers operating with shot-to-shot pulse shaping and detection. We also identify the range of different parametric conversion and supercontinuum techniques which now provide a path to making pulses of light optimal for ultrafast spectroscopy. Second, we describe specific instances from our laboratories of how the amplified Yb-based light sources and spectrometers are transformative. For multiple probe time-resolved infrared and transient 2D IR spectroscopy, the gain in temporal span and signal-to-noise enables dynamical spectroscopy measurements from femtoseconds to seconds. These gains widen the applicability of time-resolved infrared techniques across a range of topics in photochemistry, photocatalysis, and photobiology as well as lower the technical barriers to implementation in a laboratory. For 2D visible spectroscopy and microscopy with white light, as well as 2D IR imaging, the high repetition rates of these new Yb-based light sources allow one to spatially map 2D spectra while maintaining high signal-to-noise in the data. To illustrate the gains, we provide examples of imaging applications in the study of photovoltaic materials and spectroelectrochemistry.
Collapse
Affiliation(s)
- Paul M. Donaldson
- Central
Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, United Kingdom
| | - Greg M. Greetham
- Central
Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, United Kingdom
| | - Chris T. Middleton
- PhaseTech
Spectroscopy, Inc., 4916
East Broadway, Suite 125, Madison, Wisconsin 53716, United States
| | - Bradley M. Luther
- Colorado
State University, Department of Chemistry, 200 W. Lake Street, Fort Collins, Colorado 80523, United States
| | - Martin T. Zanni
- University
of Wisconsin, Department of Chemistry, Room 8361, 1101 University Ave., Madison, Wisconsin 53706, United States
| | - Peter Hamm
- University
of Zurich, Department of Chemistry, Winterthurerstrasse 190, Zurich CH-8057, Switzerland
| | - Amber T. Krummel
- Colorado
State University, Department of Chemistry, 200 W. Lake Street, Fort Collins, Colorado 80523, United States
| |
Collapse
|
10
|
Helbing J, Hamm P. Versatile Femtosecond Laser Synchronization for Multiple-Timescale Transient Infrared Spectroscopy. J Phys Chem A 2023. [PMID: 37478282 DOI: 10.1021/acs.jpca.3c03526] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Several ways to electronically synchronize different types of amplified femtosecond laser systems are presented based on a single freely programmable electronics hardware: arbitrary-detuning asynchronous optical sampling (ADASOPS), as well as actively locking two femtosecond laser oscillators, albeit not necessarily to the same round-trip frequency. They allow us to rapidly probe a very wide range of timescales, from picoseconds to potentially seconds, in a single transient absorption experiment without the need to move any delay stage. Experiments become possible that address a largely unexplored aspect of many photochemical reactions, in particular in the context of photo-catalysis as well as photoactive proteins, where an initial femtosecond trigger very often initiates a long-lasting cascade of follow-up processes. The approach is very versatile and allows us to synchronize very different lasers, such as a Ti:Sa amplifier and a 100 kHz Yb-laser system. The jitter of the synchronization, and therewith the time-resolution in the transient experiment, lies in the range from 1 to 3 ps, depending on the method. For illustration, transient IR measurements of the excited state solvation and decay of a metal carbonyl complex as well as the full reaction cycle of bacteriorhodopsin are shown. The pros and cons of the various methods are discussed, with regard to the scientific question one might want to address, and also with regard to the laser systems that might be already existent in a laser lab.
Collapse
Affiliation(s)
- Jan Helbing
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| |
Collapse
|
11
|
Buhrke D, Lahav Y, Rao A, Ruf J, Schapiro I, Hamm P. Transient 2D IR Spectroscopy and Multiscale Simulations Reveal Vibrational Couplings in the Cyanobacteriochrome Slr1393-g3. J Am Chem Soc 2023. [PMID: 37450891 DOI: 10.1021/jacs.3c00896] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
Cyanobacteriochromes are bistable photoreceptor proteins with desirable photochemical properties for biotechnological applications, such as optogenetics or fluorescence microscopy. Here, we investigate Slr1393-g3, a cyanobacteriochrome that reversibly photoswitches between a red-absorbing (Pr) and green-absorbing (Pg) form. We applied advanced IR spectroscopic methods to track the sequence of intermediates during the photocycle over many orders of magnitude in time. In the conversion from Pg to Pr, we have revealed a new intermediate with distinct spectroscopic features in the IR, which precedes Pr formation using transient IR spectroscopy. In addition, stationary and transient 2D IR experiments measured the vibrational couplings between different groups of the chromophore and the protein in these intermediate states, as well as their structural disorder. Anharmonic QM/MM calculations predict spectra in good agreement with experimental 2D IR spectra of the initial and final states of the photocycle. They facilitate the assignment of the IR spectra that serve as a basis for the interpretation of the spectroscopic results and suggest structural changes of the intermediates along the photocycle.
Collapse
Affiliation(s)
- David Buhrke
- Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland
- Institute of Biology, Humboldt University Berlin, 10115 Berlin, Germany
| | - Yigal Lahav
- Fritz Haber Center for Molecular Dynamics, Hebrew University of Jerusalem, 9190401 Jerusalem, Israel
- MIGAL - Galilee Research Institute, 1101602 Kiryat Shmona, Israel
| | - Aditya Rao
- Fritz Haber Center for Molecular Dynamics, Hebrew University of Jerusalem, 9190401 Jerusalem, Israel
| | - Jeannette Ruf
- Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Igor Schapiro
- Fritz Haber Center for Molecular Dynamics, Hebrew University of Jerusalem, 9190401 Jerusalem, Israel
| | - Peter Hamm
- Department of Chemistry, University of Zurich, 8057 Zurich, Switzerland
| |
Collapse
|
12
|
Sneha M, Thornton GL, Lewis-Borrell L, Ryder ASH, Espley SG, Clark IP, Cresswell AJ, Grayson MN, Orr-Ewing AJ. Photoredox-HAT Catalysis for Primary Amine α-C-H Alkylation: Mechanistic Insight with Transient Absorption Spectroscopy. ACS Catal 2023; 13:8004-8013. [PMID: 37342833 PMCID: PMC10278065 DOI: 10.1021/acscatal.3c01474] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/17/2023] [Indexed: 06/23/2023]
Abstract
The synergistic use of (organo)photoredox catalysts with hydrogen-atom transfer (HAT) cocatalysts has emerged as a powerful strategy for innate C(sp3)-H bond functionalization, particularly for C-H bonds α- to nitrogen. Azide ion (N3-) was recently identified as an effective HAT catalyst for the challenging α-C-H alkylation of unprotected, primary alkylamines, in combination with dicyanoarene photocatalysts such as 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN). Here, time-resolved transient absorption spectroscopy over sub-picosecond to microsecond timescales provides kinetic and mechanistic details of the photoredox catalytic cycle in acetonitrile solution. Direct observation of the electron transfer from N3- to photoexcited 4CzIPN reveals the participation of the S1 excited electronic state of the organic photocatalyst as an electron acceptor, but the N3• radical product of this reaction is not observed. Instead, both time-resolved infrared and UV-visible spectroscopic measurements implicate rapid association of N3• with N3- (a favorable process in acetonitrile) to form the N6•- radical anion. Electronic structure calculations indicate that N3• is the active participant in the HAT reaction, suggesting a role for N6•- as a reservoir that regulates the concentration of N3•.
Collapse
Affiliation(s)
- Mahima Sneha
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
- Department
of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Georgia L. Thornton
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Luke Lewis-Borrell
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| | - Alison S. H. Ryder
- Centre
for Sustainable Chemical Technologies, University
of Bath, 1 South, Claverton Down, Bath BA2 7AY, U.K.
| | - Samuel G. Espley
- Department
of Chemistry, University of Bath, 1 South, Claverton Down, Bath BA2 7AY, U.K.
| | - Ian P. Clark
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton
Laboratory, Harwell Oxford, Didcot OX11 0QX, U.K.
| | - Alexander J. Cresswell
- Department
of Chemistry, University of Bath, 1 South, Claverton Down, Bath BA2 7AY, U.K.
| | - Matthew N. Grayson
- Department
of Chemistry, University of Bath, 1 South, Claverton Down, Bath BA2 7AY, U.K.
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K.
| |
Collapse
|
13
|
Jansonas G, Budriūnas R, Valiulis G, Varanavičius A. Polarization-based idler elimination: enhancing the efficiency of optical parametric amplification. OPTICS EXPRESS 2023; 31:19794-19803. [PMID: 37381387 DOI: 10.1364/oe.488760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/08/2023] [Indexed: 06/30/2023]
Abstract
This study presents a novel way to increase the energy conversion efficiency of optical parametric amplification by eliminating the idler wave from the interaction using consecutive type-I and type-II amplification processes. By using the aforementioned straightforward approach the wavelength tunable narrow-bandwidth amplification with exceptionally high 40% peak pump-to-signal conversion efficiency and 68% peak pump depletion was achieved in the short-pulse regime, while preserving the beam quality factor of less than 1.4. The same optical layout can also serve as an enhanced idler amplification scheme.
Collapse
|
14
|
Abstract
Optimization of pump-probe signal requires a complete understanding of how signal scales with experimental factors. In simple systems, signal scales quadratically with molar absorptivity, and linearly with fluence, concentration, and path length. In practice, scaling factors weaken beyond certain thresholds (e.g., OD > 0.1) due to asymptotic limits related to optical density, fluence and path length. While computational models can accurately account for subdued scaling, quantitative explanations often appear quite technical in the literature. This Perspective aims to present a simpler understanding of the subject with concise formulas for estimating absolute magnitudes of signal under both ordinary and asymptotic scaling conditions. This formulation may be more appealing for spectroscopists seeking rough estimates of signal or relative comparisons. We identify scaling dependencies of signal with respect to experimental parameters and discuss applications for improving signal under broad conditions. We also review other signal enhancement methods, such as local-oscillator attenuation and plasmonic enhancement, and discuss respective benefits and challenges regarding asymptotic limits that signal cannot exceed.
Collapse
Affiliation(s)
- Kevin C Robben
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA
| | | |
Collapse
|
15
|
Burden TJ, Fernandez KPR, Kagoro M, Eastwood JB, Tanner TFN, Whitwood AC, Clark IP, Towrie M, Krieger J, Lynam JM, Fairlamb IJS. Coumarin C-H Functionalization by Mn(I) Carbonyls: Mechanistic Insight by Ultra-Fast IR Spectroscopic Analysis. Chemistry 2023; 29:e202203038. [PMID: 36625067 PMCID: PMC10947090 DOI: 10.1002/chem.202203038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/11/2023]
Abstract
Mn(I) C-H functionalization of coumarins provides a versatile and practical method for the rapid assembly of fused polycyclic pyridinium-containing coumarins in a regioselective manner. The synthetic strategy enables application of bench-stable organomanganese reagents in both photochemical- and thermal-promoted reactions. The cyclomanganated intermediates, and global reaction system, provide an ideal testing ground for structural characterization of the active Mn(I) carbonyl-containing species, including transient species observable by ultra-fast time-resolved spectroscopic methods. The thermodynamic reductive elimination product, solely encountered from reaction between alkynes and air-stable organometallic cyclomanganated coumarins, has enabled characterization of a critical seven-membered Mn(I) intermediate, detected by time-resolved infrared spectroscopy, enabling the elucidation of the temporal profile of key steps in the reductive elimination pathway. Quantitative data are provided. Manganated polycyclic products are readily decomplexed by AgBF4 , opening-up an efficient route to the formation of π-extended hybrid coumarin-pyridinium compounds.
Collapse
Affiliation(s)
- Thomas J. Burden
- Department of ChemistryUniversity of York HeslingtonYorkYO10 5DDUK
| | | | - Mary Kagoro
- Department of ChemistryUniversity of York HeslingtonYorkYO10 5DDUK
| | | | | | | | - Ian P. Clark
- Central Laser FacilityResearch Complex at Harwell STFC Rutherford Appleton Laboratory Harwell Campus DidcotOxfordshireOX11 0QXUK
| | - Michael Towrie
- Central Laser FacilityResearch Complex at Harwell STFC Rutherford Appleton Laboratory Harwell Campus DidcotOxfordshireOX11 0QXUK
| | | | - Jason M. Lynam
- Department of ChemistryUniversity of York HeslingtonYorkYO10 5DDUK
| | | |
Collapse
|
16
|
Eastwood JB, Hammarback LA, Burden TJ, Clark IP, Towrie M, Robinson A, Fairlamb IJS, Lynam JM. Understanding Precatalyst Activation and Speciation in Manganese-Catalyzed C–H Bond Functionalization Reactions. Organometallics 2023. [PMID: 37502314 PMCID: PMC10369674 DOI: 10.1021/acs.organomet.3c00004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
An investigation into species formed following precatalyst activation in Mn-catalyzed C-H bond functionalization reactions is reported. Time-resolved infrared spectroscopy demonstrates that light-induced CO dissociation from precatalysts [Mn(C^N)(CO)4] (C^N = cyclometalated 2-phenylpyridine (1a), cyclometalated 1,1-bis(4-methoxyphenyl)methanimine (1b)) in a toluene solution of 2-phenylpyridine (2a) or 1,1-bis(4-methoxyphenyl)methanimine (2b) results in the initial formation of solvent complexes fac-[Mn(C^N)(CO)3(toluene)]. Subsequent solvent substitution on a nanosecond time scale then yields fac-[Mn(C^N)(CO)3(κ1-(N)-2a)] and fac-[Mn(C^N)(CO)3(κ1-(N)-2b)], respectively. When the experiments are performed in the presence of phenylacetylene, the initial formation of fac-[Mn(C^N)(CO)3(toluene)] is followed by a competitive substitution reaction to give fac-[Mn(C^N)(CO)3(2)] and fac-[Mn(C^N)(CO)3(η2-PhC2H)]. The fate of the reaction mixture depends on the nature of the nitrogen-containing substrate used. In the case of 2-phenylpyridine, migratory insertion of the alkyne into the Mn-C bond occurs, and fac-[Mn(C^N)(CO)3(κ1-(N)-2a)] remains unchanged. In contrast, when 2b is used, substitution of the η2-bound phenylacetylene by 2b occurs on a microsecond time scale, and fac-[Mn(C^N)(CO)3(κ1-(N)-2b)] is the sole product from the reaction. Calculations with density functional theory indicate that this difference in behavior may be correlated with the different affinities of 2a and 2b for the manganese. This study therefore demonstrates that speciation immediately following precatalyst activation is a kinetically controlled event. The most dominant species in the reaction mixture (the solvent) initially binds to the metal. The subsequent substitution of the metal-bound solvent is also kinetically controlled (on a ns time scale) prior to the thermodynamic distribution of products being obtained.
Collapse
Affiliation(s)
- Jonathan B. Eastwood
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - L. Anders Hammarback
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Thomas J. Burden
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Ian P. Clark
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Michael Towrie
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Alan Robinson
- Syngenta Crop Protection AG Schaffhauserstrasse, 4332 Stein, Switzerland
| | - Ian J. S. Fairlamb
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Jason M. Lynam
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| |
Collapse
|
17
|
Keane PM, Zehe C, Poynton FE, Bright SA, Estayalo-Adrián S, Devereux SJ, Donaldson PM, Sazanovich IV, Towrie M, Botchway SW, Cardin CJ, Williams DC, Gunnlaugsson T, Long C, Kelly JM, Quinn SJ. Time-resolved infra-red studies of photo-excited porphyrins in the presence of nucleic acids and in HeLa tumour cells: insights into binding site and electron transfer dynamics. Phys Chem Chem Phys 2022; 24:27524-27531. [PMID: 36345709 DOI: 10.1039/d2cp04604k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/19/2023]
Abstract
Cationic porphyrins based on the 5,10,15,20-meso-(tetrakis-4-N-methylpyridyl) core (TMPyP4) have been studied extensively over many years due to their strong interactions with a variety of nucleic acid structures, and their potential use as photodynamic therapeutic agents and telomerase inhibitors. In this paper, the interactions of metal-free TMPyP4 and Pt(II)TMPyP4 with guanine-containing nucleic acids are studied for the first time using time-resolved infrared spectroscopy (TRIR). In D2O solution (where the metal-free form exists as D2TMPyP4) both compounds yielded similar TRIR spectra (between 1450-1750 cm-1) following pulsed laser excitation in their Soret B-absorption bands. Density functional theory calculations reveal that vibrations centred on the methylpyridinium groups are responsible for the dominant feature at ca. 1640 cm-1. TRIR spectra of D2TMPyP4 or PtTMPyP4 in the presence of guanosine 5'-monophosphate (GMP), double-stranded {d(GC)5}2 or {d(CGCAAATTTGCG)}2 contain negative-going signals, 'bleaches', indicative of binding close to guanine. TRIR signals for D2TMPyP4 or PtTMPyP bound to the quadruplex-forming cMYC sequence {d(TAGGGAGGG)}2T indicate that binding occurs on the stacked guanines. For D2TMPyP4 bound to guanine-containing systems, the TRIR signal at ca. 1640 cm-1 decays on the picosecond timescale, consistent with electron transfer from guanine to the singlet excited state of D2TMPyP4, although IR marker bands for the reduced porphyrin/oxidised guanine were not observed. When PtTMPyP is incorporated into HeLa tumour cells, TRIR studies show protein binding with time-dependent ps/ns changes in the amide absorptions demonstrating TRIR's potential for studying light-activated molecular processes not only with nucleic acids in solution but also in biological cells.
Collapse
Affiliation(s)
- Páraic M Keane
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
- School of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK
| | - Clara Zehe
- School of Chemistry, University College Dublin, Dublin 4, Ireland.
| | - Fergus E Poynton
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
- Trinity Biomedical Sciences Institute, The University of Dublin, Pearse St., Dublin 2, Ireland
| | - Sandra A Bright
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
- Trinity Biomedical Sciences Institute, The University of Dublin, Pearse St., Dublin 2, Ireland
| | - Sandra Estayalo-Adrián
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
- Trinity Biomedical Sciences Institute, The University of Dublin, Pearse St., Dublin 2, Ireland
| | | | - Paul M Donaldson
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - Igor V Sazanovich
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - Stanley W Botchway
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - Christine J Cardin
- School of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK
| | - D Clive Williams
- Trinity Biomedical Sciences Institute, The University of Dublin, Pearse St., Dublin 2, Ireland
| | - Thorfinnur Gunnlaugsson
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
- Trinity Biomedical Sciences Institute, The University of Dublin, Pearse St., Dublin 2, Ireland
| | - Conor Long
- School of Chemical Sciences, Dublin City University, Dublin 9, Ireland.
| | - John M Kelly
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
| | - Susan J Quinn
- School of Chemistry, University College Dublin, Dublin 4, Ireland.
| |
Collapse
|
18
|
Younesi AT, Ulbricht R. Broadband transient absorption spectroscopy using an incoherent white-light source as probe. OPTICS EXPRESS 2022; 30:38896-38906. [PMID: 36258443 DOI: 10.1364/oe.467483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 08/31/2022] [Indexed: 06/16/2023]
Abstract
Time-resolved spectroscopy and, in particular, transient absorption methods have been widely employed to study the dynamics of materials, usually achieving time resolution down to femtoseconds with measurement windows up to a few nanoseconds. Various techniques have been developed to extend the measurement duration up to milliseconds and beyond to permit probing slower dynamics. However, most of these either demand complicated and expensive equipment or do not provide broadband spectral coverage. This paper proposes a transient absorption technique in which an ultra-short pulse laser and a broadband incoherent continuous-wave light source are employed as pump and probe, respectively. Detection of the transient probe transmission is performed in a time-resolved fashion with a fast photodiode after a monochromator and the data is recorded with an oscilloscope. The time resolution is determined by the electronic bandwidth of the detection and acquisition devices and is ∼1 ns, with a measurement duration window of up to milliseconds and a spectral resolution of <2 nm covering from 0.4 to 2 µm. In addition, the setup can be employed to measure time- and spectrally-resolved photoluminescence.
Collapse
|
19
|
Kao MH, Orr-Ewing AJ. Charge-Separated Reactive Intermediates from the UV Photodissociation of Chlorobenzene in Solution. J Phys Chem A 2022; 126:6934-6943. [PMID: 36148486 PMCID: PMC9549464 DOI: 10.1021/acs.jpca.2c05327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Although ultraviolet
(UV)-induced photochemical cleavage of carbon–halogen
bonds in gaseous halocarbons is mostly homolytic, the photolysis of
chlorobenzene in solution has been proposed to produce a phenyl cation,
c-C6H5+, which is a highly reactive
intermediate of potential use in chemical synthesis and N2 activation. Any evidence for such a route to phenyl cations is indirect,
with uncertainty remaining about the possible mechanism. Here, ultrafast
transient absorption spectroscopy of UV-excited (λ = 240 and
270 nm) chlorobenzene solutions in fluorinated (perfluorohexane) and
protic (ethanol and 2,2,2-trifluoroethanol) solvents reveals a broad
electronic absorption band centered at 540 nm that is assigned to
an isomer of chlorobenzene with both charge-separated and triplet-spin
carbene character. This spectroscopic feature is weaker, or absent,
when experiments are conducted in cyclohexane. The intermediate isomer
of chlorobenzene has a solvent-dependent lifetime of 30–110
ps, determined by reaction with the solvent or quenching to a lower-lying
singlet state. Evidence is presented for dissociation to ortho-benzyne, but the intermediate could also be a precursor to phenyl
cation formation.
Collapse
Affiliation(s)
- Min-Hsien Kao
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| |
Collapse
|
20
|
Ma J, Miao TJ, Tang J. Charge carrier dynamics and reaction intermediates in heterogeneous photocatalysis by time-resolved spectroscopies. Chem Soc Rev 2022; 51:5777-5794. [PMID: 35770623 DOI: 10.1039/d1cs01164b] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sunlight as the most abundant renewable energy holds the promise to make our society sustainable. However, due to its low power density and intermittence, efficient conversion and storage of solar energy as a clean fuel are crucial. Apart from solar fuel synthesis, sunlight can also be used to drive other reactions including organic conversion and air/water purification. Given such potential of photocatalysis, the past few decades have seen a surge in the discovery of photocatalysts. However, the current photocatalytic efficiency is still very moderate. To address this challenge, it is important to understand fundamental factors that dominate the efficiency of a photocatalytic process to enable the rational design and development of photocatalytic systems. Many recent studies highlighted transient absorption spectroscopy (TAS) and time-resolved infrared (TRIR) spectroscopy as powerful approaches to characterise charge carrier dynamics and reaction pathways to elucidate the reasons behind low photocatalytic efficiencies, and to rationalise photocatalytic activities exhibited by closely related materials. Accordingly, as a fast-moving area, the past decade has witnessed an explosion in reports on charge carrier dynamics and reaction mechanisms on a wide range of photocatalytic materials. This critical review will discuss the application of TAS and TRIR in a wide range of heterogeneous photocatalytic systems, demonstrating the variety of ways in which these techniques can be used to understand the correlation between materials design, charge carrier behaviour, and photocatalytic activity. Finally, it provides a comprehensive outlook for potential developments in the area of time-resolved spectroscopies with an aim to provide design strategies for photocatalysts.
Collapse
Affiliation(s)
- Jiani Ma
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, and the Energy and Catalysis Hub, College of Chemistry and Materials Science, Northwest University, Xi'an, P. R. China
| | - Tina Jingyan Miao
- Department of Chemical Engineering, University College London (UCL), WC1E 7JE, London, UK.,Department of Chemistry, University College London (UCL), WC1H 0AJ, London, UK.
| | - Junwang Tang
- Department of Chemical Engineering, University College London (UCL), WC1E 7JE, London, UK
| |
Collapse
|
21
|
Schubert L, Langner P, Ehrenberg D, Lorenz-Fonfria VA, Heberle J. Protein conformational changes and protonation dynamics probed by a single shot using quantum-cascade-laser-based IR spectroscopy. J Chem Phys 2022; 156:204201. [PMID: 35649857 DOI: 10.1063/5.0088526] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mid-IR spectroscopy is a powerful and label-free technique to investigate protein reactions. In this study, we use quantum-cascade-laser-based dual-comb spectroscopy to probe protein conformational changes and protonation events by a single-shot experiment. By using a well-characterized membrane protein, bacteriorhodopsin, we provide a comparison between dual-comb spectroscopy and our homebuilt tunable quantum cascade laser (QCL)-based scanning spectrometer as tools to monitor irreversible reactions with high time resolution. In conclusion, QCL-based infrared spectroscopy is demonstrated to be feasible for tracing functionally relevant protein structural changes and proton translocations by single-shot experiments. Thus, we envisage a bright future for applications of this technology for monitoring the kinetics of irreversible reactions as in (bio-)chemical transformations.
Collapse
Affiliation(s)
- Luiz Schubert
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Pit Langner
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - David Ehrenberg
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Victor A Lorenz-Fonfria
- Institute of Molecular Science, Universitat de Valencia, Catedrático José Beltrán Martínez, No. 2, 46980 Paterna, Spain
| | - Joachim Heberle
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| |
Collapse
|
22
|
Rutherford SH, Greetham GM, Towrie M, Parker AW, Kharratian S, Krauss TF, Nordon A, Baker MJ, Hunt NT. Detection of paracetamol binding to albumin in blood serum using 2D-IR spectroscopy. Analyst 2022; 147:3464-3469. [DOI: 10.1039/d2an00978a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-Dimensional Infrared (2D-IR) spectroscopy is used to detect binding of paracetamol with proteins in blood serum. Quantitative peak patterns are observed indicating structural changes of the albumins' secondary structure when paracetamol bound.
Collapse
Affiliation(s)
- Samantha H. Rutherford
- WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow, G1 1RD, UK
| | - Gregory M. Greetham
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Anthony W. Parker
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Soheila Kharratian
- Department of Chemistry and York Biomedical Institute, University of York, Heslington, York, YO10 5DD, UK
- School of Physics, Engineering and Technology and York Biomedical Research Institute, University of York, Heslington, York, YO10 5DD, UK
| | - Thomas F. Krauss
- School of Physics, Engineering and Technology and York Biomedical Research Institute, University of York, Heslington, York, YO10 5DD, UK
| | - Alison Nordon
- WestCHEM, Department of Pure and Applied Chemistry and CPACT, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, UK
| | - Matthew J. Baker
- WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Technology and Innovation Centre, 99 George Street, Glasgow, G1 1RD, UK
- Dxcover Ltd, Suite RC534, 204 George Street, Glasgow, G1 1XL, UK
| | - Neil T. Hunt
- Department of Chemistry and York Biomedical Institute, University of York, Heslington, York, YO10 5DD, UK
| |
Collapse
|
23
|
Hammarback LA, Eastwood JB, Burden TJ, Pearce CJ, Clark IP, Towrie M, Robinson A, Fairlamb IJS, Lynam JM. A comprehensive understanding of carbon-carbon bond formation by alkyne migratory insertion into manganacycles. Chem Sci 2022; 13:9902-9913. [PMID: 36199635 PMCID: PMC9431456 DOI: 10.1039/d2sc02562k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 07/08/2022] [Indexed: 11/25/2022] Open
Abstract
Migratory insertion (MI) is one of the most important processes underpinning the transition metal-catalysed formation of C–C and C–X bonds. In this work, a comprehensive model of MI is presented, based on the direct observation of the states involved in the coupling of alkynes with cyclometallated ligands, augmented with insight from computational chemistry. Time-resolved spectroscopy demonstrates that photolysis of complexes [Mn(C^N)(CO)4] (C^N = cyclometalated ligand) results in ultra-fast dissociation of a CO ligand. Performing the experiment in a toluene solution of an alkyne results in the initial formation of a solvent complex fac-[Mn(C^N)(toluene)(CO)3]. Solvent substitution gives an η2-alkyne complex fac-[Mn(C^N)(η2-R1C2R2)(CO)3] which undergoes MI of the unsaturated ligand into the Mn–C bond. These data allowed for the dependence of second order rate constants for solvent substitution and first order rate constants for C–C bond formation to be determined. A systematic investigation into the influence of the alkyne and C^N ligand on this process is reported. The experimental data enabled the development of a computational model for the MI reaction which demonstrated that a synergic interaction between the metal and the nascent C–C bond controls both the rate and regiochemical outcome of the reaction. The time-resolved spectroscopic method enabled the observation of a multi-step reaction occurring over 8 orders of magnitude in time, including the formation of solvent complexes, ligand substitution and two sequential C–C bond formation steps. Time-resolved spectroscopy and computational chemistry have informed a unified model of alkyne migratory insertion, an important processes underpinning the transition metal-catalysed formation of C–C and C–X bonds.![]()
Collapse
Affiliation(s)
| | | | - Thomas J Burden
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Callum J Pearce
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus Didcot Oxfordshire OX11 0QX UK
| | - Michael Towrie
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Campus Didcot Oxfordshire OX11 0QX UK
| | - Alan Robinson
- Syngenta Crop Protection AG Münchwilen Breitenloh 5,4333 Switzerland
| | - Ian J S Fairlamb
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Jason M Lynam
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| |
Collapse
|
24
|
Blackburn TJ, Tyler SM, Pemberton JE. Optical Spectroscopy of Surfaces, Interfaces, and Thin Films. Anal Chem 2022; 94:515-558. [DOI: 10.1021/acs.analchem.1c05323] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Thomas J. Blackburn
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - Sarah M. Tyler
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - Jeanne E. Pemberton
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| |
Collapse
|
25
|
Pospíšil P, Cwiklik L, Sýkora J, Hof M, Greetham GM, Towrie M, Vlček A. Solvent-Dependent Excited-State Evolution of Prodan Dyes. J Phys Chem B 2021; 125:13858-13867. [PMID: 34914398 DOI: 10.1021/acs.jpcb.1c09030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Excited-state character and dynamics of two 6-(dimethylamino)-2-acylnaphthalene dyes (Prodan and Badan-SCH2CH2OH) were studied by picosecond time-resolved IR spectroscopy (TRIR) in solvents of different polarity and relaxation times: hexane, CD3OD, and glycerol-d8. In all these solvents, near-UV excitation initially produced the same S1(ππ*) excited state characterized by a broad TRIR signal. A very fast decay (3, ∼100 ps) followed in hexane, whereas conversion to a distinct IR spectrum with a ν(C═O) band downshifted by 76 cm-1 occurred in polar/H-bonding solvents, slowing down on going from CD3OD (1, 23 ps) to glycerol-d8 (5.5, 51, 330 ps). The final relaxed excited state was assigned as planar Me2N → C═O intramolecular charge transfer S1(ICT) by comparing experimental and TDDFT-calculated spectra. TRIR conversion kinetics are comparable to those of early stages of multiexponential fluorescence decay and dynamic fluorescence red-shift. This work presents a strong evidence that Prodan-type dyes undergo solvation-driven charge separation in their S1 state, which is responsible for the dynamic fluorescence Stokes shift observed in polar/H-bonding solvents. The time evolution of the optically prepared S1(ππ*) state to the S1(ICT) final state reflects environment relaxation and solvation dynamics. This finding rationalizes the widespread use of Prodan-type dyes as probes of environment dynamics and polarity.
Collapse
Affiliation(s)
- Petr Pospíšil
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague, Czech Republic
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague, Czech Republic
| | - Jan Sýkora
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague, Czech Republic
| | - Gregory M Greetham
- Central Laser Facility, Research Complex at Harwell, STFC, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Michael Towrie
- Central Laser Facility, Research Complex at Harwell, STFC, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Antonín Vlček
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, CZ-18223 Prague, Czech Republic.,Department of Chemistry, Queen Mary University of London, E1 4NS London, United Kingdom
| |
Collapse
|
26
|
Bozovic O, Jankovic B, Hamm P. Using azobenzene photocontrol to set proteins in motion. Nat Rev Chem 2021; 6:112-124. [PMID: 37117294 DOI: 10.1038/s41570-021-00338-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2021] [Indexed: 02/06/2023]
Abstract
Controlling the activity of proteins with azobenzene photoswitches is a potent tool for manipulating their biological function. With the help of light, it is possible to change binding affinities, control allostery or manipulate complex biological processes, for example. Additionally, owing to their intrinsically fast photoisomerization, azobenzene photoswitches can serve as triggers that initiate out-of-equilibrium processes. Such switching of the activity initiates a cascade of conformational events that can be accessed with time-resolved methods. In this Review, we show how the potency of azobenzene photoswitching can be combined with transient spectroscopic techniques to disclose the order of events and experimentally observe biomolecular interactions in real time. This strategy will further our understanding of how a protein can accommodate, adapt and readjust its structure to answer an incoming signal, revealing more of the dynamical character of proteins.
Collapse
|
27
|
Buhrke D, Ruf J, Heckmeier P, Hamm P. A stop-flow sample delivery system for transient spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:123001. [PMID: 34972444 DOI: 10.1063/5.0068227] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 11/06/2021] [Indexed: 06/14/2023]
Abstract
A stop-flow sample delivery system for transient spectroscopy is presented, which is, in particular, suited for laser-based instruments (quantum-cascade lasers or amplified femtosecond lasers) with excitation pulse repetition rates in the range 10-100 Hz. Two pulsing micro-valves are mounted onto a flow cuvette designed for transient IR spectroscopy, which is integrated into a flow cycle driven by a peristaltic pump. The performance of the system is demonstrated with transient IR experiments of the trans-to-cis photoisomerization of a water-soluble azobenzene derivative. The sample stands still when the micro-valves are closed and is pushed out from the probe beam focus on a 1 ms timescale when opening the micro-valves. The setup is extremely sample efficient. It needs only small sample volumes, and at the same time, it enables excitation of a large fraction of molecules in solution.
Collapse
Affiliation(s)
- David Buhrke
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Jeannette Ruf
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Philipp Heckmeier
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| |
Collapse
|
28
|
Lewis-Borrell L, Sneha M, Clark IP, Fasano V, Noble A, Aggarwal VK, Orr-Ewing AJ. Direct Observation of Reactive Intermediates by Time-Resolved Spectroscopy Unravels the Mechanism of a Radical-Induced 1,2-Metalate Rearrangement. J Am Chem Soc 2021; 143:17191-17199. [PMID: 34614354 DOI: 10.1021/jacs.1c07964] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Radical-induced 1,2-metalate rearrangements of boronate complexes are an emerging and promising class of reactions that allow multiple new bonds to be formed in a single, tunable reaction step. These reactions involve the addition of an alkyl radical, typically generated from an alkyl iodide under photochemical activation, to a boronate complex to produce an α-boryl radical intermediate. From this α-boryl radical, there are two plausible reaction pathways that can trigger the product forming 1,2-metalate rearrangement: iodine atom transfer (IAT) or single electron transfer (SET). Previous steady-state techniques have struggled to differentiate these pathways. Here we apply state-of-the-art time-resolved infrared absorption spectroscopy to resolve all the steps in the reaction cycle by mapping production and consumption of the reactive intermediates over picosecond to millisecond time scales. We apply this technique to a recently reported reaction involving the addition of an electron-deficient alkyl radical to the strained σ-bond of a bicyclo[1.1.0]butyl boronate complex to form a cyclobutyl boronic ester. We show that the previously proposed SET mechanism does not adequately account for the observed spectral and kinetic data. Instead, we demonstrate that IAT is the preferred pathway for this reaction and is likely to be operative for other reactions of this type.
Collapse
Affiliation(s)
- Luke Lewis-Borrell
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Mahima Sneha
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Valerio Fasano
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Adam Noble
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Varinder K Aggarwal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| |
Collapse
|
29
|
Baptista FA, Krizsan D, Stitch M, Sazanovich IV, Clark IP, Towrie M, Long C, Martinez-Fernandez L, Improta R, Kane-Maguire NAP, Kelly JM, Quinn SJ. Adenine Radical Cation Formation by a Ligand-Centered Excited State of an Intercalated Chromium Polypyridyl Complex Leads to Enhanced DNA Photo-oxidation. J Am Chem Soc 2021; 143:14766-14779. [PMID: 34464120 PMCID: PMC8447253 DOI: 10.1021/jacs.1c06658] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
Assessment of the
DNA photo-oxidation and synthetic photocatalytic
activity of chromium polypyridyl complexes is dominated by consideration
of their long-lived metal-centered excited states. Here we report
the participation of the excited states of [Cr(TMP)2dppz]3+ (1) (TMP = 3,4,7,8-tetramethyl-1,10-phenanthroline;
dppz = dipyrido[3,2-a:2′,3′-c]phenazine) in DNA photoreactions. The interactions of
enantiomers of 1 with natural DNA or with oligodeoxynucleotides
with varying AT content (0–100%) have been studied by steady
state UV/visible absorption and luminescence spectroscopic methods,
and the emission of 1 is found to be quenched in all
systems. The time-resolved infrared (TRIR) and visible absorption
spectra (TA) of 1 following excitation in the region
between 350 to 400 nm reveal the presence of relatively long-lived
dppz-centered states which eventually yield the emissive metal-centered
state. The dppz-localized states are fully quenched when bound by
GC base pairs and partially so in the presence of an AT base-pair
system to generate purine radical cations. The sensitized formation
of the adenine radical cation species (A•+T) is identified by assigning the TRIR spectra with help of
DFT calculations. In natural DNA and oligodeoxynucleotides containing
a mixture of AT and GC of base pairs, the observed time-resolved spectra
are consistent with eventual photo-oxidation occurring predominantly
at guanine through hole migration between base pairs. The combined
targeting of purines leads to enhanced photo-oxidation of guanine.
These results show that DNA photo-oxidation by the intercalated 1, which locates the dppz in contact with the target purines,
is dominated by the LC centered excited state. This work has implications
for future phototherapeutics and photocatalysis.
Collapse
Affiliation(s)
| | - Dorottya Krizsan
- School of Chemistry, University College Dublin, Dublin 4, Ireland
| | - Mark Stitch
- School of Chemistry, University College Dublin, Dublin 4, Ireland
| | - Igor V Sazanovich
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, U.K
| | - Ian P Clark
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, U.K
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, U.K
| | - Conor Long
- The School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
| | - Lara Martinez-Fernandez
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemistry(IADCHEM) Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Roberto Improta
- Consiglio Nazionale delle Ricerche, Istituto di Biostrutture e Bioimmagini, 80136 Naples, Italy
| | - Noel A P Kane-Maguire
- Department of Chemistry, Furman University, 3300 Poinsett Highway, Greenville, South Carolina 29613-1120, United States
| | - John M Kelly
- School of Chemistry, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - Susan J Quinn
- School of Chemistry, University College Dublin, Dublin 4, Ireland
| |
Collapse
|
30
|
Sneha M, Bhattacherjee A, Lewis-Borrell L, Clark IP, Orr-Ewing AJ. Structure-Dependent Electron Transfer Rates for Dihydrophenazine, Phenoxazine, and Phenothiazine Photoredox Catalysts Employed in Atom Transfer Radical Polymerization. J Phys Chem B 2021; 125:7840-7854. [PMID: 34237215 DOI: 10.1021/acs.jpcb.1c05069] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Organic photocatalysts (PCs) are gaining popularity in applications of photoredox catalysis, but few studies have explored their modus operandi. We report a detailed mechanistic investigation of the electron transfer activation step of organocatalyzed atom transfer radical polymerization (O-ATRP) involving electronically excited organic PCs and a radical initiator, methyl 2-bromopropionate (MBP). This study compares nine N-aryl modified PCs possessing dihydrophenazine, phenoxazine, or phenothiazine core chromophores. Transient electronic and vibrational absorption spectroscopies over subpicosecond to nanosecond and microsecond time intervals, respectively, track spectroscopic signatures of both the reactants and products of photoinduced electron transfer in N,N-dimethylformamide, dichloromethane, and toluene solutions. The rate coefficients for electron transfer exhibit a range of values up to ∼1010 M-1 s-1 influenced systematically by the PC structures. These rate coefficients are an order of magnitude smaller for catalysts with charge transfer character in their first excited singlet (S1) or triplet (T1) states than for photocatalysts with locally excited character. The latter species show nearly diffusion-limited rate coefficients for the electron transfer to MBP. The derived kinetic parameters are used to model the contributions to electron transfer from the S1 state of each PC for different concentrations of MBP. Comparisons of singlet and triplet reactivity for one of the phenoxazine PCs reveal that the rate coefficient kET(T1) = (2.7 ± 0.3) × 107 M-1 s-1 for electron transfer from the T1 state is 2 orders of magnitude lower than that from the S1 state, kET(S1) = (2.6 ± 0.4) × 109 M-1 s-1. The trends in bimolecular electron transfer rate coefficients are accounted for using a modified Marcus theory for dissociative electron transfer.
Collapse
Affiliation(s)
- Mahima Sneha
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Aditi Bhattacherjee
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Luke Lewis-Borrell
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0QX, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| |
Collapse
|
31
|
Jankovic B, Ruf J, Zanobini C, Bozovic O, Buhrke D, Hamm P. Sequence of Events during Peptide Unbinding from RNase S: A Complete Experimental Description. J Phys Chem Lett 2021; 12:5201-5207. [PMID: 34038133 DOI: 10.1021/acs.jpclett.1c01155] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The phototriggered unbinding of the intrinsically disordered S-peptide from the RNase S complex is studied with the help of transient IR spectroscopy, covering a wide range of time scales from 100 ps to 10 ms. To that end, an azobenzene moiety has been linked to the S-peptide in a way that its helicity is disrupted by light, thereby initiating its complete unbinding. The full sequence of events is observed, starting from unfolding of the helical structure of the S-peptide on a 20 ns time scale while still being in the binding pocket of the S-protein, S-peptide unbinding after 300 μs, and the structural response of the S-protein after 3 ms. With regard to the S-peptide dynamics, the binding mechanism can be classified as an induced fit, while the structural response of the S-protein is better described as conformational selection.
Collapse
Affiliation(s)
- Brankica Jankovic
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Jeannette Ruf
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Claudio Zanobini
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Olga Bozovic
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - David Buhrke
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| |
Collapse
|
32
|
Affiliation(s)
- Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
| |
Collapse
|
33
|
Bhattacherjee A, Sneha M, Lewis-Borrell L, Amoruso G, Oliver TAA, Tyler J, Clark IP, Orr-Ewing AJ. Singlet and Triplet Contributions to the Excited-State Activities of Dihydrophenazine, Phenoxazine, and Phenothiazine Organocatalysts Used in Atom Transfer Radical Polymerization. J Am Chem Soc 2021; 143:3613-3627. [PMID: 33629835 DOI: 10.1021/jacs.1c00279] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The photochemical dynamics of three classes of organic photoredox catalysts employed in organocatalyzed atom-transfer radical polymerization (O-ATRP) are studied using time-resolved optical transient absorption and fluorescence spectroscopy. The nine catalysts selected for study are examples of N-aryl and core-substituted dihydrophenazine, phenoxazine and phenothiazine compounds with varying propensities for control of polymerization outcomes. Excited singlet-state lifetimes extracted from the spectroscopic measurements are reported in N,N-dimethylformamide (DMF), dichloromethane (DCM), and toluene. Ultrafast (<200 fs to 3 ps) electronic relaxation of the photocatalysts after photoexcitation at near-UV wavelengths (318-390 nm) populates the first singlet excited state (S1). The S1-state lifetimes range from 130 ps to 40 ns with a considerable dependence on the photocatalyst structure and the solvent. The competition between ground electronic state recovery and intersystem crossing controls triplet state populations and is a minor pathway in the dihydrophenazine derivatives but is of greater importance for phenoxazine and phenothiazine catalysts. A comparison of our results with previously reported O-ATRP performances of the various photoredox catalysts shows that high triplet-state quantum yields are not a prerequisite for controlling polymer dispersity. For example, the photocatalyst 5,10-bis(4-cyanophenyl)-5,10-dihydrophenazine, shown previously to exert good polymerization control, possesses the shortest S1-state lifetime (135 ps in DMF and 180 ps in N,N-dimethylacetamide) among the nine examples reported here and a negligible triplet-state quantum yield. The results call for a re-evaluation of the excited-state properties of most significance in governing the photocatalytic behavior of organic photoredox catalysts in O-ATRP reactions.
Collapse
Affiliation(s)
- Aditi Bhattacherjee
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Mahima Sneha
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Luke Lewis-Borrell
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Giordano Amoruso
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Thomas A A Oliver
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Jasper Tyler
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| |
Collapse
|
34
|
Hammarback LA, Aucott BJ, Bray JTW, Clark IP, Towrie M, Robinson A, Fairlamb IJS, Lynam JM. Direct Observation of the Microscopic Reverse of the Ubiquitous Concerted Metalation Deprotonation Step in C-H Bond Activation Catalysis. J Am Chem Soc 2021; 143:1356-1364. [PMID: 33428402 DOI: 10.1021/jacs.0c10409] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ability of carboxylate groups to promote the direct functionalization of C-H bonds in organic compounds is unquestionably one of the most important discoveries in modern chemical synthesis. Extensive computational studies have indicated that this process proceeds through the deprotonation of a metal-coordinated C-H bond by the basic carboxylate, yet experimental validation of these predicted mechanistic pathways is limited and fraught with difficulty, mainly as rapid proton transfer is frequently obscured in ensemble measures in multistep reactions (i.e., a catalytic cycle consisting of several steps). In this paper, we describe a strategy to experimentally observe the microscopic reverse of the key C-H bond activation step underpinning functionalization processes (viz. M-C bond protonation). This has been achieved by utilizing photochemical activation of the thermally robust precursor [Mn(ppy)(CO)4] (ppy = metalated 2-phenylpyridine) in neat acetic acid. Time-resolved infrared spectroscopy on the picosecond-millisecond time scale allows direct observation of the states involved in the proton transfer from the acetic acid to the cyclometalated ligand, providing direct experimental evidence for the computationally predicted reaction pathways. The power of this approach to probe the mechanistic pathways in transition-metal-catalyzed reactions is demonstrated through experiments performed in toluene solution in the presence of PhC2H and HOAc. These allowed for the observation of sequential displacement of the metal-bound solvent by the alkyne, C-C bond formation though insertion in the Mn-C bond, and a slower protonation step by HOAc to generate the product of a Mn(I)-catalyzed C-H bond functionalization reaction.
Collapse
Affiliation(s)
| | - Benjamin J Aucott
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K
| | - Joshua T W Bray
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K
| | - Ian P Clark
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, U.K
| | - Michael Towrie
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, U.K
| | - Alan Robinson
- Syngenta Crop Protection AG, Breitenloh 5, Münchwilen 433, Switzerland
| | - Ian J S Fairlamb
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K
| | - Jason M Lynam
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K
| |
Collapse
|
35
|
Devereux SJ, Poynton FE, Baptista FR, Gunnlaugsson T, Cardin CJ, Sazanovich IV, Towrie M, Kelly JM, Quinn SJ. Caught in the Loop: Binding of the [Ru(phen) 2 (dppz)] 2+ Light-Switch Compound to Quadruplex DNA in Solution Informed by Time-Resolved Infrared Spectroscopy. Chemistry 2020; 26:17103-17109. [PMID: 32725823 DOI: 10.1002/chem.202002165] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Indexed: 01/05/2023]
Abstract
Ultrafast time-resolved infrared (TRIR) is used to report on the binding site of the [Ru(phen)2 (dppz)]2+ "light-switch" complex with both bimolecular (Oxytricha nova telomere) and intramolecular (human telomere) guanine-quadruplex structures in both K+ and Na+ containing solutions. TRIR permits the simultaneous monitoring both of the "dark" and "bright" states of the complex and of the quadruplex nucleobase bases, the latter via a Stark effect induced by the excited state of the complex. These data are used to establish the contribution of guanine base stacking and loop interactions to the binding site of this biologically relevant DNA structure in solution. A particularly striking observation is the strong thymine signal observed for the Na+ form of the human telomere sequence, which is expected to be in the anti-parallel conformation.
Collapse
Affiliation(s)
| | - Fergus E Poynton
- School of Chemistry, Trinity College Dublin, Dublin, 2, Ireland.,Trinity Biomedical Sciences Institute (TBSI), Trinity College Dublin, Dublin, 2, Ireland
| | | | - Thorfinnur Gunnlaugsson
- School of Chemistry, Trinity College Dublin, Dublin, 2, Ireland.,Trinity Biomedical Sciences Institute (TBSI), Trinity College Dublin, Dublin, 2, Ireland
| | - Christine J Cardin
- Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK
| | | | - Michael Towrie
- Rutherford Appleton Laboratory, STFC, Harwell Campus, OX11 0FA, UK
| | - John M Kelly
- School of Chemistry, Trinity College Dublin, Dublin, 2, Ireland
| | - Susan J Quinn
- School of Chemistry, University College Dublin, Dublin, 4, Ireland
| |
Collapse
|
36
|
Farrell KM, Ostrander JS, Jones AC, Yakami BR, Dicke SS, Middleton CT, Hamm P, Zanni MT. Shot-to-shot 2D IR spectroscopy at 100 kHz using a Yb laser and custom-designed electronics. OPTICS EXPRESS 2020; 28:33584-33602. [PMID: 33115018 PMCID: PMC7679191 DOI: 10.1364/oe.409360] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/08/2020] [Accepted: 10/08/2020] [Indexed: 05/29/2023]
Abstract
The majority of 2D IR spectrometers operate at 1-10 kHz using Ti:Sapphire laser technology. We report a 2D IR spectrometer designed around Yb:KGW laser technology that operates shot-to-shot at 100 kHz. It includes a home-built OPA, a mid-IR pulse shaper, and custom-designed electronics with optional on-chip processing. We report a direct comparison between Yb:KGW and Ti:Sapphire based 2D IR spectrometers. Even though the mid-IR pulse energy is much lower for the Yb:KGW driven system, there is an 8x improvement in signal-to-noise over the 1 kHz Ti:Sapphire driven spectrometer to which it is compared. Experimental data is shown for sub-millimolar concentrations of amides. Advantages and disadvantages of the design are discussed, including thermal background that arises at high repetition rates. This fundamental spectrometer design takes advantage of newly available Yb laser technology in a new way, providing a straightforward means of enhancing sensitivity.
Collapse
Affiliation(s)
- Kieran M. Farrell
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Josh S. Ostrander
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Currently with the Department of Chemistry, Indiana Wesleyan University, Marion, Indiana 46953, USA
| | - Andrew C. Jones
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Currently with the Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Albuquerque, New Mexico 87185, USA
| | - Baichhabi R. Yakami
- PhaseTech Spectroscopy, 2810 Crossroads Drive, Suite 4000 Madison, Wisconsin 53718, USA
| | - Sidney S. Dicke
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Chris T. Middleton
- PhaseTech Spectroscopy, 2810 Crossroads Drive, Suite 4000 Madison, Wisconsin 53718, USA
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Martin T. Zanni
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| |
Collapse
|
37
|
Donaldson PM. Photon echoes and two dimensional spectra of the amide I band of proteins measured by femtosecond IR - Raman spectroscopy. Chem Sci 2020; 11:8862-8874. [PMID: 34123140 PMCID: PMC8163424 DOI: 10.1039/d0sc02978e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Infrared (IR) and Raman spectroscopy are fundamental techniques in chemistry, allowing the convenient determination of bond specific chemical composition and structure. Over the last decades, ultrafast multidimensional IR approaches using sequences of femtosecond IR pulses have begun to provide a new means of gaining additional information on molecular vibrational couplings, distributions of molecular structures and ultrafast molecular structural dynamics. In this contribution, new approaches to measuring multidimensional spectra involving IR and Raman processes are presented and applied to the study of the amide I band of proteins. Rephasing of the amide I band is observed using dispersed IR-Raman photon echoes and frequency domain 2D-IR-Raman spectra are measured by use of a mid-IR pulse shaper or over a broader spectral range using a tuneable picosecond laser. A simple pulse shaping approach to performing heterodyned time-domain Fourier Transform 2D-IR-Raman spectroscopy is introduced, revealing that the 2D-IR-Raman spectra distinguish homogeneous and inhomogeneous broadening in the same way as the well-established methods of 2D-IR spectroscopy. Across all datasets, the unique dependence of the amide I data on the IR and Raman strengths, vibrational anharmonicities and inhomogeneous broadening provides a fascinating spectroscopic view of the amide I band. New ultrafast 2D-IR-Raman photon echo spectroscopy techniques are introduced and applied to the structural analysis of proteins.![]()
Collapse
Affiliation(s)
- Paul M Donaldson
- Central Laser Facility, RCaH, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus Didcot OX11 0QX UK
| |
Collapse
|
38
|
Sneha M, Lewis-Borrell L, Shchepanovska D, Bhattacherjee A, Tyler J, Orr-Ewing AJ. Solvent-dependent photochemical dynamics of a phenoxazine-based photoredox catalyst. ACTA ACUST UNITED AC 2020. [DOI: 10.1515/zpch-2020-1624] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
Organic substitutes for ruthenium and iridium complexes are increasingly finding applications in chemical syntheses involving photoredox catalysis. However, the performance of these organic compounds as electron-transfer photocatalysts depends on their accessible photochemical pathways and excited state lifetimes. Here, the UV-induced dynamics of N-phenyl phenoxazine, chosen as a prototypical N-aryl phenoxazine organic photoredox catalyst, are explored in three solvents, N,N-dimethyl formamide, dichloromethane and toluene, using ultrafast transient absorption spectroscopy. Quantum chemistry calculations reveal the locally excited or charge-transfer electronic character of the excited states, and are used to assign the transient electronic and vibrational bands observed. In toluene-d8, complete ground-state recovery is (31 ± 3) % by internal conversion (IC) from the photo-excited state (or from S1 after IC but before complete vibrational relaxation), (13 ± 2) % via direct decay from vibrationally relaxed S1 (most likely radiative decay, with an estimated radiative lifetime of 13 ns) and (56 ± 3) % via the T1 state (with intersystem crossing (ISC) rate coefficient k
ISC = (3.3 ± 0.2) × 108 s−1). In dichloromethane, we find evidence for excited state N-phenyl phenoxazine reaction with the solvent. Excited state lifetimes, ISC rates, and ground-state recovery show only modest variation with changes to the solvent environment because of the locally excited character of the S1 and T1 states.
Collapse
Affiliation(s)
- Mahima Sneha
- School of Chemistry , University of Bristol , Cantock’s Close , BS8 1TS , Bristol , UK
| | - Luke Lewis-Borrell
- School of Chemistry , University of Bristol , Cantock’s Close , BS8 1TS , Bristol , UK
| | - Darya Shchepanovska
- School of Chemistry , University of Bristol , Cantock’s Close , BS8 1TS , Bristol , UK
| | - Aditi Bhattacherjee
- School of Chemistry , University of Bristol , Cantock’s Close , BS8 1TS , Bristol , UK
| | - Jasper Tyler
- School of Chemistry , University of Bristol , Cantock’s Close , BS8 1TS , Bristol , UK
| | - Andrew J. Orr-Ewing
- School of Chemistry , University of Bristol , Cantock’s Close , BS8 1TS , Bristol , UK
| |
Collapse
|
39
|
Antonucci L, Solinas X, Bonvalet A, Joffre M. Electronic measurement of femtosecond time delays for arbitrary-detuning asynchronous optical sampling. OPTICS EXPRESS 2020; 28:18251-18260. [PMID: 32680025 DOI: 10.1364/oe.393887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
Arbitrary-Detuning ASynchronous OPtical Sampling (ADASOPS) is a pump-probe technique which relies on the stability of femtosecond oscillators. It provides access to a multiscale time window ranging up to millisecond, combined with a sub-picosecond time resolution. In contrast with the first ADASOPS demonstration based on the interferometric detection of coincidences between optical pulses, we show here that the optical setup can now be reduced to a mere pair of photodetectors embedded in a specially-designed electronic system. In analogy with super-resolution methods used in optical microscopy for localizing single emitters beyond the diffraction limit, we demonstrate that purely electronic means allow the determination of time delays between each pump-probe pulse pair with a standard deviation as small as 200 fs. The new method is shown to be simpler, more versatile and more accurate than the coincidence-based approach.
Collapse
|
40
|
Greetham GM, Clark IP, Young B, Fritsch R, Minnes L, Hunt NT, Towrie M. Time-Resolved Temperature-Jump Infrared Spectroscopy at a High Repetition Rate. APPLIED SPECTROSCOPY 2020; 74:720-727. [PMID: 32114769 DOI: 10.1177/0003702820913636] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Time-resolved temperature-jump infrared absorption spectroscopy at a 0.5 to 1 kHz repetition rate is presented. A 1 kHz neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pumping an optical parametric oscillator provided >70 µJ, 3.75 µm pump pulses, which delivered a temperature jump via excitation of the O-D stretch of a D2O solution. A 10 kHz train of mid-infrared probe pulses was used to monitor spectral changes following the temperature jump. Calibration with trifluoroacetic acid solution showed that a temperature jump of 10 K lasting for tens of microseconds was achieved, sufficient to observe fast processes in functionally relevant biomolecular mechanisms. Modeling of heating profiles across ≤10 µm path length cells and subsequent cooling dynamics are used to describe the initial <100 ns cooling at the window surface and subsequent, >10 µs cooling dynamics of the bulk solution.
Collapse
Affiliation(s)
- Gregory M Greetham
- Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, UK
| | - Ian P Clark
- Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, UK
| | - Benjamin Young
- Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, UK
| | - Robby Fritsch
- Department of Physics, SUPA, University of Strathclyde, Glasgow, UK
| | - Lucy Minnes
- Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, UK
- Department of Physics, SUPA, University of Strathclyde, Glasgow, UK
| | - Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute, University of York, Heslington, York, UK
| | - Mike Towrie
- Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, UK
| |
Collapse
|
41
|
Eastwood JB, Hammarback LA, McRobie MT, Clark IP, Towrie M, Fairlamb IJS, Lynam JM. Time-resolved infra-red spectroscopy reveals competitive water and dinitrogen coordination to a manganese(i) carbonyl complex. Dalton Trans 2020; 49:5463-5470. [PMID: 32255172 DOI: 10.1039/c9dt04878b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Time-resolved infra-red (TRIR) spectroscopy has been used to demonstrate that photolysis of [Mn(C^N)(CO)4] (C^N = bis-(4-methoxyphenyl)methanimine) in heptane solution results in ultra-fast CO dissociation and ultimate formation of a rare Mn-containing dinitrogen complex fac-[Mn(C^N)(CO)3(N2)] with a diagnostic stretching mode for a terminal-bound N[triple bond, length as m-dash]N ligand at 2249 cm-1. An isotopic shift to 2174 cm-1 was observed when the reaction was performed under 15N2 and the band was not present when the experiment was undertaken under an atmosphere of argon, reinforcing this assignment. An intermediate solvent complex fac-[Mn(C^N)(CO)3(heptane)] was identified which is formed in less than 2 ps, indicating that CO-release occurs on an ultra-fast timescale. The heptane ligand is labile and is readily displaced by both N2 and water to give fac-[Mn(C^N)(CO)3(N2)] and fac-[Mn(C^N)(CO)3(OH2)] respectively. The fac-[Mn(C^N)(CO)3(heptane)] framework showed a significant affinity for N2, as performing the reaction under air produced significant amounts of fac-[Mn(C^N)(CO)3(N2)]. Kinetic analysis reveals that the substitution of heptane by N2 (k = (1.028 ± 0.004) × 109 mol-1 dm3 s-1), and H2O is competitive on fast (<1 μs) time scales. The binding of water is reversible and, under an atmosphere of N2, some fac-[Mn(C^N)(CO)3(OH2)] converts to fac-[Mn(C^N)(CO)3(N2)].
Collapse
Affiliation(s)
- Jonathan B Eastwood
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
| | | | | | | | | | | | | |
Collapse
|
42
|
Lewis-Borrell L, Sneha M, Bhattacherjee A, Clark IP, Orr-Ewing AJ. Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates. Chem Sci 2020; 11:4475-4481. [PMID: 34122905 PMCID: PMC8159429 DOI: 10.1039/d0sc01194k] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/16/2020] [Indexed: 12/12/2022] Open
Abstract
The rapid development of new applications of photoredox catalysis has so far outpaced the mechanistic studies important for rational design of new classes of catalysts. Here, we report the use of ultrafast transient absorption spectroscopic methods to reveal both mechanistic and kinetic details of multiple sequential steps involved in an organocatalyzed atom transfer radical polymerization reaction. The polymerization system studied involves a N,N-diaryl dihydrophenazine photocatalyst, a radical initiator (methyl 2-bromopropionate) and a monomer (isoprene). Time-resolved spectroscopic measurements spanning sub-picosecond to microseconds (i.e., almost 8 orders of magnitude of time) track the formation and loss of key reactive intermediates. These measurements identify both the excited state of the photocatalyst responsible for electron transfer and the radical intermediates participating in propagation reactions, as well as quantifying their lifetimes. The outcomes connect the properties of N,N-diaryl dihydrophenazine organic photocatalysts with the rates of sequential steps in the catalytic cycle.
Collapse
Affiliation(s)
- Luke Lewis-Borrell
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| | - Mahima Sneha
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| | - Aditi Bhattacherjee
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory Harwell Oxford, Didcot Oxfordshire OX11 0QX UK
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| |
Collapse
|
43
|
Abstract
Infrared difference spectroscopy probes vibrational changes of proteins upon their perturbation. Compared with other spectroscopic methods, it stands out by its sensitivity to the protonation state, H-bonding, and the conformation of different groups in proteins, including the peptide backbone, amino acid side chains, internal water molecules, or cofactors. In particular, the detection of protonation and H-bonding changes in a time-resolved manner, not easily obtained by other techniques, is one of the most successful applications of IR difference spectroscopy. The present review deals with the use of perturbations designed to specifically change the protein between two (or more) functionally relevant states, a strategy often referred to as reaction-induced IR difference spectroscopy. In the first half of this contribution, I review the technique of reaction-induced IR difference spectroscopy of proteins, with special emphasis given to the preparation of suitable samples and their characterization, strategies for the perturbation of proteins, and methodologies for time-resolved measurements (from nanoseconds to minutes). The second half of this contribution focuses on the spectral interpretation. It starts by reviewing how changes in H-bonding, medium polarity, and vibrational coupling affect vibrational frequencies, intensities, and bandwidths. It is followed by band assignments, a crucial aspect mostly performed with the help of isotopic labeling and site-directed mutagenesis, and complemented by integration and interpretation of the results in the context of the studied protein, an aspect increasingly supported by spectral calculations. Selected examples from the literature, predominately but not exclusively from retinal proteins, are used to illustrate the topics covered in this review.
Collapse
|
44
|
Robben KC, Cheatum CM. Edge-pixel referencing suppresses correlated baseline noise in heterodyned spectroscopies. J Chem Phys 2020; 152:094201. [PMID: 33480715 DOI: 10.1063/1.5134987] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Referencing schemes are commonly used in heterodyned spectroscopies to mitigate correlated baseline noise arising from shot-to-shot fluctuations of the local oscillator. Although successful, these methods rely on careful pixel-to-pixel matching between the two spectrographs. A recent scheme introduced by Feng et al. [Opt. Express 27(15), 20323-20346 (2019)] employed a correlation matrix to allow free mapping between dissimilar spectrographs, leading to the first demonstration of floor noise limited detection on a multichannel array used in heterodyned spectroscopy. In addition to their primary results using a second reference spectrometer, Feng et al. briefly demonstrated the flexibility of their method by referencing to same-array pixels at the two spectral edges (i.e., edge-pixel referencing). We present a comprehensive study of this approach, which we term edge-pixel referencing, including optimization of the approach, assessment of the performance, and determination of the effects of background responses. We show that, within some limitations, the distortions due to background signals will not affect the 2D IR line shape or amplitude and can be mitigated by band narrowing of the pump beams. We also show that the performance of edge-pixel referencing is comparable to that of referencing to a second spectrometer in terms of noise suppression and that the line shapes and amplitudes of the spectral features are, within the measurement error, identical. Altogether, these results demonstrate that edge-pixel referencing is a powerful approach for noise suppression in heterodyned spectroscopies, which requires no new hardware and, so, can be implemented as a software solution for anyone performing heterodyned spectroscopy with multichannel array detectors already.
Collapse
Affiliation(s)
- Kevin C Robben
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA
| | | |
Collapse
|
45
|
Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights. Nat Commun 2019; 10:5152. [PMID: 31723133 PMCID: PMC6853971 DOI: 10.1038/s41467-019-13154-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 10/24/2019] [Indexed: 01/19/2023] Open
Abstract
The photochemical decarboxylation of carboxylic acids is a versatile route to free radical intermediates for chemical synthesis. However, the sequential nature of this multi-step reaction renders the mechanism challenging to probe. Here, we employ a 100 kHz mid-infrared probe in a transient absorption spectroscopy experiment to track the decarboxylation of cyclohexanecarboxylic acid in acetonitrile-d3 over picosecond to millisecond timescales using a photooxidant pair (phenanthrene and 1,4-dicyanobenzene). Selective excitation of phenanthrene at 256 nm enables a diffusion-limited photoinduced electron transfer to 1,4-dicyanobenzene. A measured time offset in the rise of the CO2 byproduct reports on the lifetime (520 ± 120 ns) of a reactive carboxyl radical in solution, and spectroscopic observation of the carboxyl radical confirm its formation as a reaction intermediate. Precise clocking of the lifetimes of radicals generated in situ by an activated C-C bond fission will pave the way for improving the photocatalytic selectivity and turnover.
Collapse
|
46
|
Fritzsch R, Greetham GM, Clark IP, Minnes L, Towrie M, Parker AW, Hunt NT. Monitoring Base-Specific Dynamics during Melting of DNA-Ligand Complexes Using Temperature-Jump Time-Resolved Infrared Spectroscopy. J Phys Chem B 2019; 123:6188-6199. [PMID: 31268327 DOI: 10.1021/acs.jpcb.9b04354] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Ultrafast time-resolved infrared spectroscopy employing nanosecond temperature-jump initiation has been used to study the melting of double-stranded (ds)DNA oligomers in the presence and absence of minor groove-binding ligand Hoechst 33258. Ligand binding to ds(5'-GCAAATTTCC-3'), which binds Hoechst 33258 in the central A-tract region with nanomolar affinity, causes a dramatic increase in the timescales for strand melting from 30 to ∼250 μs. Ligand binding also suppresses premelting disruption of the dsDNA structure, which takes place on 100 ns timescales and includes end-fraying. In contrast, ligand binding to the ds(5'-GCATATATCC-3') sequence, which exhibits an order of magnitude lower affinity for Hoechst 33258 than the A-tract motif, leads to an increase by only a factor of 5 in melting timescales and reduced suppression of premelting sequence perturbation and end-fraying. These results demonstrate a dynamic impact of the minor groove ligand on the dsDNA structure that correlates with binding strength and thermodynamic stabilization of the duplex. Moreover, the ability of the ligand to influence base pairs distant from the binding site has potential implications for allosteric communication mechanisms in dsDNA.
Collapse
Affiliation(s)
- Robby Fritzsch
- Department of Physics, SUPA , University of Strathclyde , Glasgow G4 0NG , U.K
| | - Gregory M Greetham
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus, Didcot OX11 0QX , U.K
| | - Ian P Clark
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus, Didcot OX11 0QX , U.K
| | - Lucy Minnes
- Department of Physics, SUPA , University of Strathclyde , Glasgow G4 0NG , U.K
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus, Didcot OX11 0QX , U.K
| | - Anthony W Parker
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus, Didcot OX11 0QX , U.K
| | - Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute , University of York , Heslington, York YO10 5DD , U.K
| |
Collapse
|
47
|
Orr-Ewing AJ. Perspective: How can ultrafast laser spectroscopy inform the design of new organic photoredox catalysts for chemical and materials synthesis? STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2019; 6:010901. [PMID: 30868082 PMCID: PMC6404927 DOI: 10.1063/1.5082620] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 01/07/2019] [Indexed: 06/09/2023]
Abstract
Photoredox catalysis of chemical reactions, using light-activated molecules which serve as electron donors or acceptors to initiate chemical transformations under mild conditions, is finding widespread use in the synthesis of organic compounds and materials. The transition-metal-centred complexes first developed for these photoredox-catalysed applications are steadily being superseded by more sustainable and lower toxicity organic photocatalysts. While the diversity of possible structures for photoredox-active organic molecules brings benefits of design flexibility, it also presents considerable challenges for optimization of the photocatalyst molecular architecture. Transient absorption spectroscopy over timescales from the femtosecond to microsecond domains can explore the detailed mechanisms of activation and reaction of these organic photocatalysts in solution and, by linking their dynamical properties to their structures, has the potential to establish reliable design principles for future development of improved photocatalysts.
Collapse
Affiliation(s)
- Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| |
Collapse
|
48
|
Aucott BJ, Eastwood JB, Anders Hammarback L, Clark IP, Sazanovich IV, Towrie M, Fairlamb IJS, Lynam JM. Insight into the mechanism of CO-release from trypto-CORM using ultra-fast spectroscopy and computational chemistry. Dalton Trans 2019; 48:16426-16436. [DOI: 10.1039/c9dt03343b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Photolysis of trypto-CORM results in ultra-fast CO-dissociation and formation of a 16-e triplet followed by solvation.
Collapse
Affiliation(s)
| | | | | | - Ian P. Clark
- Central Laser Facility
- STFC Rutherford Appleton Laboratory
- Didcot
- UK
| | | | - Michael Towrie
- Central Laser Facility
- STFC Rutherford Appleton Laboratory
- Didcot
- UK
| | | | | |
Collapse
|
49
|
Chergui M. Ultrafast photophysics and photochemistry of iron hexacyanides in solution: Infrared to X-ray spectroscopic studies. Coord Chem Rev 2018. [DOI: 10.1016/j.ccr.2018.05.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
50
|
|