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Abstract
Photochemical reactions are increasingly being used for chemical and materials synthesis, for example, in photoredox catalysis, and generally involve photoexcitation of molecular chromophores dissolved in a liquid solvent. The choice of solvent influences the outcomes of the photochemistry because solute-solvent interactions modify the energies of and crossings between electronic states of the chromophores, and they affect the evolving structures of the photoexcited molecules. Ultrafast laser spectroscopy methods with femtosecond to picosecond time resolution can resolve the dynamics of these photoexcited molecules as they undergo structural and electronic changes, relax back to the ground state, dissipate their excess internal energy to the surrounding solvent, or undergo photochemical reactions. In this Account, we illustrate how experimental studies using ultrafast lasers can reveal the influences that different solvents or cosolutes exert on the photoinduced nonadiabatic dynamics of internal conversion and intersystem crossing in nonradiative relaxation pathways. Although the environment surrounding a solute molecule is rapidly changing, with fluctuations in the coordination to neighboring solvent molecules occurring on femtosecond or picosecond time scales, we show that it is possible to photoexcite selectively only those molecular chromophores transiently experiencing specific solute-solvent interactions such as intermolecular hydrogen bonding.The effects of different solvation environments on the photodynamics are illustrated using four selected examples of photochemical processes in which the solvent has a marked effect on the outcomes. We first consider two aromatic carbonyl compounds, benzophenone and acetophenone, which are known to undergo fast intersystem crossing to populate the first excited triplet state on time scales of a few picoseconds. We show that the nonadiabatic excited-state dynamics are modified by transient hydrogen bonding of the carbonyl group to a protic solvent or by coordination to a metal cation cosolute. We then examine how different solvents modify the competition between two alternative relaxation pathways in a photoexcited UVA-sunscreen molecule, diethylamino hydroxybenzoyl hexyl benzoate (DHHB). This relaxation back to the ground electronic state is an essential part of the effective operation of the sunscreen compound, but the dynamics are sensitive to the surrounding environment. Finally, we consider how solvents of different polarity affect the energies and lifetimes of excited states with locally excited or charge-transfer character in heterocyclic organic compounds used as excited-state electron donors for photoredox catalysis. With these and other examples, we seek to develop a molecular level understanding of how the choice of solution environment might be used to control the outcomes of photochemical reactions.
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Affiliation(s)
- Ravi Kumar Venkatraman
- 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
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Robertson PA, Bishop HM, Orr-Ewing AJ. Tuning the Excited-State Dynamics of Acetophenone Using Metal Ions in Solution. J Phys Chem Lett 2021; 12:5473-5478. [PMID: 34085833 DOI: 10.1021/acs.jpclett.1c01466] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The effects of dissolved metal salts on the excited-state dynamics of acetophenone in solution have been explored by using ultrafast transient absorption spectroscopy at two UV excitation wavelengths. In the absence of metal ions, the S1(nπ*) transition of acetophenone is excited at 320 nm, with intersystem crossing (ISC) occurring with a time constant τISC = 5.95 ± 0.47 ps in acetonitrile solution. Excitation at 280 nm accesses the S2(ππ*) state, which internally converts (<0.2 ps) to S1 before undergoing ISC with τISC = 4.36 ± 0.14 ps. Coordination to Mg2+ ions makes the S2 state accessible to excitation at 320 nm, with the rate of S2 → S1 internal conversion reducing 3-fold but the ISC rate increasing. These changes to the excited-state energies and dynamics of this model photosensitizer indicate that dissolved metal salts could modify the photochemistry of synthetically useful homogeneous photocatalytic systems.
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Affiliation(s)
- Patrick A Robertson
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Hannah M Bishop
- 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
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Jessop IA, Bravo D, Durán E, Rodríguez‐González FE, Tagle LH, Coll D, Ortiz P, Mirabal Y, Aguilar‐Vega M, Martin‐Trasanco R, Terraza CA, Tundidor‐Camba A. Synthesis and characterization of new spirobisindane‐based poly(imide)s: Structure effects on solubility, thermal behavior, and gas transport properties. J Appl Polym Sci 2020. [DOI: 10.1002/app.48944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- I. A. Jessop
- Faculty of Chemistry, Organic and Polymeric Materials Research LaboratoryUniversidad de Tarapacá P.O. Box 7‐D Arica Chile
| | - D. Bravo
- Research Laboratory for Organic Polymers (RLOP), Department of Organic ChemistryPontificia Universidad Católica de Chile Santiago Chile
| | - E. Durán
- Research Laboratory for Organic Polymers (RLOP), Department of Organic ChemistryPontificia Universidad Católica de Chile Santiago Chile
| | - F. E. Rodríguez‐González
- Research Laboratory for Organic Polymers (RLOP), Department of Organic ChemistryPontificia Universidad Católica de Chile Santiago Chile
| | - L. H. Tagle
- Research Laboratory for Organic Polymers (RLOP), Department of Organic ChemistryPontificia Universidad Católica de Chile Santiago Chile
| | - D. Coll
- Núcleo de Química y BioquímicaFacultad de Ciencias, Universidad Mayor Santiago Chile
| | - P. Ortiz
- Núcleo de Química y BioquímicaFacultad de Ciencias, Universidad Mayor Santiago Chile
| | - Y. Mirabal
- Faculty of EngineeringUniversidad Autónoma de Chile, Institute of Applied Chemisty Talca Chile
| | - M. Aguilar‐Vega
- Laboratorio de Membranas, Unidad de MaterialesCentro de Investigación Científica de Yucatán A.C., Chuburna de Hidalgo Mérida Yucatán Mexico
| | - R. Martin‐Trasanco
- Departamento de Química, Universidad Tecnológica MetropolitanaJ. P. Alessandri 1242 Santiago Chile
| | - C. A. Terraza
- Research Laboratory for Organic Polymers (RLOP), Department of Organic ChemistryPontificia Universidad Católica de Chile Santiago Chile
- UC Energy Research Center, Pontificia Universidad Católica de Chile
| | - A. Tundidor‐Camba
- Research Laboratory for Organic Polymers (RLOP), Department of Organic ChemistryPontificia Universidad Católica de Chile Santiago Chile
- UC Energy Research Center, Pontificia Universidad Católica de Chile
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Affiliation(s)
- Teresa L. Mako
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, Rhode Island 02881, United States
| | - Joan M. Racicot
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, Rhode Island 02881, United States
| | - Mindy Levine
- Department of Chemistry, University of Rhode Island, 140 Flagg Road, Kingston, Rhode Island 02881, United States
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Sekiya R, Kuroda R. Controlling stereoselectivity of solid-state photoreactions by co-crystal formation. Chem Commun (Camb) 2011; 47:10097-9. [DOI: 10.1039/c1cc13484a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Tsukamoto D, Shiraishi Y, Hirai T. Highly Efficient Methyl Ketone Synthesis with Photoactivated Acetone and Olefins Assisted by Mg(II)-Exchanged Zeolite Y. J Org Chem 2010; 75:1450-7. [DOI: 10.1021/jo902321f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daijiro Tsukamoto
- Research Center for Solar Energy Chemistry and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Yasuhiro Shiraishi
- Research Center for Solar Energy Chemistry and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Takayuki Hirai
- Research Center for Solar Energy Chemistry and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
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Sivasubramanian K, Kaanumalle LS, Uppili S, Ramamurthy V. Value of zeolites in asymmetric induction during photocyclization of pyridones, cyclohexadienones and naphthalenones. Org Biomol Chem 2007; 5:1569-76. [PMID: 17571186 DOI: 10.1039/b702572f] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two strategies, namely chiral inductor and chiral auxiliary approaches, have been examined within zeolites with the aim of achieving asymmetric induction during the photocyclization of cyclohexadienone, naphthalenone and pyridone derivatives. Within zeolites, enantioselectivity as high as 55% and diastereoselectivity as high as 88% have been obtained. The observed stereoselectivities are significant given the fact that these reactions gave very little stereoselectivities in isotropic solution media. The results obtained on the photocyclization of dienones, naphthalenones and N-alkyl pyridones within zeolites compliment our earlier investigations on the photocyclization of tropolone derivatives, the geometric isomerization of 1,2-diphenylcyclopropanes and 2,3-diphenyl-1-benzoyl cyclopropanes, and the Norrish type II reaction of alpha-oxoamides, phenyl adamantyl ketones, phenyl norbornyl ketones and phenyl cyclohexyl ketones. With the help of these examples, we have established the importance of zeolite and its charge compensating cations in effecting asymmetric induction in photochemical reactions.
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Grosso V, Previtali C, Chesta CA, Vera DMA, Pierini AB. An experimental and theoretical study on the electrostatic effect of an appended cationic group on electronic properties of aromatic systems. Phys Chem Chem Phys 2007; 9:5988-96. [DOI: 10.1039/b709751d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Thomas JK. Physical Aspects of Radiation-Induced Processes on SiO2, γ-Al2O3, Zeolites, and Clays. Chem Rev 2005; 105:1683-734. [PMID: 15884787 DOI: 10.1021/cr020378a] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- J K Thomas
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA.
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Jockusch S, Sivaguru J, Turro NJ, Ramamurthy V. Direct measurement of the singlet oxygen lifetime in zeolites by near-IR phosphorescence. Photochem Photobiol Sci 2005; 4:403-5. [PMID: 15875071 DOI: 10.1039/b501701g] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Time-resolved near-IR phosphorescence spectroscopy was employed to determine the lifetime of singlet oxygen in Y-zeolites and porous silica and it was found to depend strongly on the alumina content of the zeolite.
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Affiliation(s)
- Steffen Jockusch
- Department of Chemistry, Columbia University, 3000 Broadway, New York, NY 10027, USA
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Ma C, Zuo P, Kwok WM, Chan WS, Kan JTW, Toy PH, Phillips DL. Time-Resolved Resonance Raman Study of the Triplet States of p-Hydroxyacetophenone and the p-Hydroxyphenacyl Diethyl Phosphate Phototrigger Compound. J Org Chem 2004; 69:6641-57. [PMID: 15387586 DOI: 10.1021/jo049331a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pico- and nanosecond time-resolved resonance Raman (TR3) spectroscopy have been utilized to study the dynamics and structure of p-hydroxyacetophenone (HA) and the p-hydroxyphenacyl-caged phototrigger compound p-hydroxyphenacyl diethyl phosphate (HPDP) in acetonitrile solution. Transient intermediates were detected and attributed to the triplet states of HA and HPDP. Nanosecond-TR3 measurements were done for two isotopically substituted HA molecules to help better assign the triplet state carbonyl C=O stretching and the ring related vibrational modes. The dynamics of formation and the spectral characteristics for the triplet states were found to be similar for the HA and HPDP. The temporal evolution at very early picosecond time scale indicates there is rapid intersystem crossing (ISC) conversion and subsequent relaxation of the excess energy of the initially produced energetic triplet state. B3LYP/6-311G** density functional theory (DFT) calculations were done to determine the structures and vibrational frequencies for both the triplet and ground states of HA and HPDP. The calculated spectra reproduce the experimental spectra and the observed isotopic shifts reasonably well and were used to make tentative assignments to all the experimentally observed features. The triplet states were found to have extensive conjugated pipi* nature with a single-bond-like carbonyl CO bond. We briefly compare the triplet structure and formation dynamics of HA and HPDP as well as the conformational changes upon going from the ground state to the triplet state. We discuss our present results in relation to the initial pathway for the p-hydroxyphenacyl photodeprotection process. We also compare and discuss the properties of the HA pipi* triplet state relative to the published results of other aromatic carbonyl compounds.
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Affiliation(s)
- Chensheng Ma
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P. R. China
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Yuasa J, Ohkubo K, Guldi DM, Fukuzumi S. Drastic Changes in the Lifetime and Electron Transfer and Energy Transfer Reactivity of the Triplet Excited State of p-Benzoquinone by Complex Formation with Scandium Ion Salts. J Phys Chem A 2004. [DOI: 10.1021/jp047748e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Junpei Yuasa
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, CREST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan, and Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556
| | - Kei Ohkubo
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, CREST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan, and Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556
| | - Dirk M. Guldi
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, CREST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan, and Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556
| | - Shunichi Fukuzumi
- Department of Material and Life Science, Graduate School of Engineering, Osaka University, CREST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan, and Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556
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Pitchumani K, Warrier M, Kaanumalle LS, Ramamurthy V. Triplet photochemistry within zeolites through heavy atom effect, sensitization and light atom effect. Tetrahedron 2003. [DOI: 10.1016/s0040-4020(03)00865-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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