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Roy P, Sardjan AS, Browne WR, Feringa BL, Meech SR. Excited State Dynamics in Unidirectional Photochemical Molecular Motors. J Am Chem Soc 2024; 146:12255-12270. [PMID: 38656968 PMCID: PMC11082934 DOI: 10.1021/jacs.4c01019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 04/05/2024] [Accepted: 04/08/2024] [Indexed: 04/26/2024]
Abstract
Unidirectional photochemically driven molecular motors (PMMs) convert the energy of absorbed light into continuous rotational motion. As such they are key components in the design of molecular machines. The prototypical and most widely employed class of PMMs is the overcrowded alkenes, where rotational motion is driven by successive photoisomerization and thermal helix inversion steps. The efficiency of such PMMs depends upon the speed of rotation, determined by the rate of ground state thermal helix inversion, and the quantum yield of photoisomerization, which is dependent on the excited state energy landscape. The former has been optimized by synthetic modification across three generations of overcrowded alkene PMMs. These improvements have often been at the expense of photoisomerization yield, where there remains room for improvement. In this perspective we review the application of ultrafast spectroscopy to characterize the excited state dynamics in PMMs. These measurements lead to a general mechanism for all generations of PMMs, involving subpicosecond decay of a Franck-Condon excited state to populate a dark excited state which decays within picoseconds via conical intersections with the electronic ground state. The model is discussed in the context of excited state dynamics calculations. Studies of PMM photochemical dynamics as a function of solvent suggest exploitation of intramolecular charge transfer and solvent polarity as a route to controlling photoisomerization yield. A test of these ideas for a first generation motor reveals a high degree of solvent control over isomerization yield. These results suggest a pathway to fine control over the performance of future PMMs.
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Affiliation(s)
- Palas Roy
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
- School
of Basic Sciences, Indian Institute of Technology
Bhubaneswar, Bhubaneswar, Odisha 752050, India
| | - Andy S. Sardjan
- Molecular
Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747AG Groningen, The Netherlands
| | - Wesley R. Browne
- Molecular
Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747AG Groningen, The Netherlands
| | - Ben L. Feringa
- Centre
for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, 9747AG Groningen, The Netherlands
| | - Stephen R. Meech
- School
of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K.
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2
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Wu GY, Zhu HM, Li H, Zhang K, Zhang X, Yan D, Zhang XD, Lin L, Lu Z. The impact of aggregation of AIE and ACQ moiety-integrating material on the excited state dynamics. RSC Adv 2023; 13:33911-33917. [PMID: 38020029 PMCID: PMC10658659 DOI: 10.1039/d3ra06359c] [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: 09/18/2023] [Accepted: 10/21/2023] [Indexed: 12/01/2023] Open
Abstract
The investigation of the properties of aggregate materials is highly interesting because the process of aggregation can result in the disappearance of original properties and the emergence of new ones. Here, a novel fluorescent material (TPEIP), which synergistically combines aggregation-induced emission (AIE) and aggregation caused quenching (ACQ) moieties, was first synthesized by the cyclization reaction of 2,3-diamino-phenazine with 4-tetraphenylenthenealdehyde. We controlled the degree of aggregation of TPEIP to shed light on the impact of the aggregation on the excited state dynamics. TPEIP aggregation realized control over the Intersystem Crossing (ISC) rates and, in turn, the suppression of triplet excited states in MeOH, EtOH or via the simple addition of water to TPEIP solutions in DMSO. From global target analysis, the time scale was 966.2 ps for ISC for TPEIP in DMSO, but it was 860 ps in the case of TPEIP solutions featuring 5% water. The dynamics of TPEIP excited states undergo significant changes as the degree of aggregation increases. Notably, the lifetime of singlet excited states decreases, and there was a gradual diminishment in triplet states.
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Affiliation(s)
- Gui-Yuan Wu
- Anhui Province Key Laboratory of Optoelectronic Material Science and Technology, School of Physics and Electronic Information, Anhui Normal University Wuhu 241002 China
| | - Hui-Min Zhu
- Anhui Province Key Laboratory of Optoelectronic Material Science and Technology, School of Physics and Electronic Information, Anhui Normal University Wuhu 241002 China
| | - Hao Li
- Anhui Province Key Laboratory of Optoelectronic Material Science and Technology, School of Physics and Electronic Information, Anhui Normal University Wuhu 241002 China
| | - Kai Zhang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University Jinan 250014 China
| | - Xianyi Zhang
- Anhui Province Key Laboratory of Optoelectronic Material Science and Technology, School of Physics and Electronic Information, Anhui Normal University Wuhu 241002 China
| | - Dong Yan
- Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science, Anhui Normal University Wuhu 241002 China
| | - Xiu-Du Zhang
- Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science, Anhui Normal University Wuhu 241002 China
| | - Lili Lin
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University Jinan 250014 China
| | - Zhou Lu
- Anhui Province Key Laboratory of Optoelectronic Material Science and Technology, School of Physics and Electronic Information, Anhui Normal University Wuhu 241002 China
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3
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Chen Q, Denisov SA, Dobrovolskii D, Mostafavi M. Observation of Nanoconfinement Effect on the Kinetics of Hydrated Electron in the Nanoscale Water Pools of Water-AOT-Cyclohexane Microemulsions by Picosecond Pulse Radiolysis. J Phys Chem B 2023; 127:7974-7982. [PMID: 37681575 DOI: 10.1021/acs.jpcb.3c04302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
The decay kinetics of the hydrated electron (eaq-) in aerosol OT (AOT)-based ternary microemulsions with pool sizes ranging from 0.34 to 4.85 nm were studied using picosecond pulse radiolysis coupled with transient absorption UV-vis spectroscopy. Electron transfer from oil to water and the subsequent solvation occurred within a time resolution of 7 ps. The decay kinetics of eaq- were accurately modeled using a double-exponential decay model, revealing the occurrence of two types of reactions, i.e., the recombination reaction at the water-oil interface and the radical-radical reactions in the water pools. The apparent lifetimes of both types of decays decreased significantly as the size of water pools decreased, indicating the influence of nanoconfinement effects. Moreover, the importance of the water-oil interface increased with decreasing water content, regardless of the presence or absence of NO3- as an electron scavenger in the water pools. Our findings provide a comprehensive understanding on the kinetics of the radiation reaction in AOT-based microemulsions.
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Affiliation(s)
- Qingde Chen
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay, 91405 Orsay, Cedex, France
- Beijing National Laboratory for Molecular Sciences, Fundamental Science on Radiochemistry and Radiation Chemistry Laboratory, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Sergey A Denisov
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay, 91405 Orsay, Cedex, France
| | - Denis Dobrovolskii
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay, 91405 Orsay, Cedex, France
| | - Mehran Mostafavi
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay, 91405 Orsay, Cedex, France
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4
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Yang J, Gelin MF, Chen L, Šanda F, Thyrhaug E, Hauer J. Two-dimensional fluorescence excitation spectroscopy: A novel technique for monitoring excited-state photophysics of molecular species with high time and frequency resolution. J Chem Phys 2023; 159:074201. [PMID: 37581414 DOI: 10.1063/5.0156297] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/27/2023] [Indexed: 08/16/2023] Open
Abstract
We propose a novel UV/Vis femtosecond spectroscopic technique, two-dimensional fluorescence-excitation (2D-FLEX) spectroscopy, which combines spectral resolution during the excitation process with exclusive monitoring of the excited-state system dynamics at high time and frequency resolution. We discuss the experimental feasibility and realizability of 2D-FLEX, develop the necessary theoretical framework, and demonstrate the high information content of this technique by simulating the 2D-FLEX spectra of a model four-level system and the Fenna-Matthews-Olson antenna complex. We show that the evolution of 2D-FLEX spectra with population time directly monitors energy transfer dynamics and can thus yield direct qualitative insight into the investigated system. This makes 2D-FLEX a highly efficient instrument for real-time monitoring of photophysical processes in polyatomic molecules and molecular aggregates.
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Affiliation(s)
- Jianmin Yang
- School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Maxim F Gelin
- School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China
| | | | - František Šanda
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, 12116 Prague, Czech Republic
| | - Erling Thyrhaug
- Department of Chemistry, Technical University of Munich, D-85747 Garching, Germany
| | - Jürgen Hauer
- Department of Chemistry, Technical University of Munich, D-85747 Garching, Germany
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Boeije Y, Olivucci M. From a one-mode to a multi-mode understanding of conical intersection mediated ultrafast organic photochemical reactions. Chem Soc Rev 2023; 52:2643-2687. [PMID: 36970950 DOI: 10.1039/d2cs00719c] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
This review discusses how ultrafast organic photochemical reactions are controlled by conical intersections, highlighting that decay to the ground-state at multiple points of the intersection space results in their multi-mode character.
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Affiliation(s)
- Yorrick Boeije
- Van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Massimo Olivucci
- Chemistry Department, University of Siena, Via Aldo Moro n. 2, 53100 Siena, Italy
- Chemistry Department, Bowling Green State University, Overman Hall, Bowling Green, Ohio 43403, USA
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Ramamurthy V, Sen P, Elles CG. Ultrafast Excited State Dynamics of Spatially Confined Organic Molecules. J Phys Chem A 2022; 126:4681-4699. [PMID: 35786917 DOI: 10.1021/acs.jpca.2c03276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This Feature Article highlights the role of spatial confinement in controlling the fundamental behavior of molecules. Select examples illustrate the value of using space as a tool to control and understand excited-state dynamics through a combination of ultrafast spectroscopy and conventional steady-state methods. Molecules of interest were confined within a closed molecular capsule, derived from a cavitand known as octa acid (OA), whose internal void space is sufficient to accommodate molecules as long as tetracene and as wide as pyrene. The free space, i.e., the space that is left following the occupation of the guest within the host, is shown to play a significant role in altering the behavior of guest molecules in the excited state. The results reported here suggest that in addition to weak interactions that are commonly emphasized in supramolecular chemistry, the extent of empty space (i.e., the remaining void space within the capsule) is important in controlling the excited-state behavior of confined molecules on ultrafast time scales. For example, the role of free space in controlling the excited-state dynamics of guest molecules is highlighted by probing the cis-trans isomerization of stilbenes and azobenzenes within the OA capsule. Isomerization of both types of molecule are slowed when they are confined within a small space, with encapsulated azobenzenes taking a different reaction pathway compared to that in solution upon excitation to S2. In addition to steric constraints, confinement of reactive molecules in a small space helps to override the need for diffusion to bring the reactants together, thus enabling the measurement of processes that occur faster than the time scale for diffusion. The advantages of reducing free space and confining reactive molecules are illustrated by recording unprecedented excimer emission from anthracene and by measuring ultrafast electron transfer rates across the organic molecular wall. By monitoring the translational motion of anthracene pairs in a restricted space, it has been possible to document the pathway undertaken by excited anthracene from inception to the formation of the excimer on the excited-state surface. Similarly, ultrafast electron transfer experiments pursued here have established that the process is not hindered by a molecular wall. Apparently, the electron can cross the OA capsule wall provided the donor and acceptor are in close proximity. Measurements on the ultrafast time scale provide crucial insights for each of the examples presented here, emphasizing the value of both "space" and "time" in controlling and understanding the dynamics of excited molecules.
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Affiliation(s)
| | - Pratik Sen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, UP 208 016, India
| | - Christopher G Elles
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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