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Wang PY, Hsu YC, Chen PH, Chen GY, Liao YK, Cheng PY. Solvent-polarity dependence of ultrafast excited-state dynamics of trans-4-nitrostilbene. Phys Chem Chem Phys 2024; 26:788-807. [PMID: 38088777 DOI: 10.1039/d3cp05245a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Ultrafast excited-state dynamics of the simplest nitrostilbenes, namely trans-4-nitrostilbene (t-NSB), was studied in solvents of various polarities with ultrafast broadband time-resolved fluorescence and transient absorption spectroscopies, and by quantum-chemical computations. The results revealed that the initially excited S1(ππ*) state deactivation dynamics is strongly influenced by the solvent polarity. Specifically, the t-NSB S1-state lifetime decreases by three orders of magnitude from ∼60 ps in high-polarity solvents to ∼60 fs in nonpolar solvents. The strong solvent-polarity dependence arises from the differences in dipole moments among the S1 and relevant states, including the major intersystem crossing (ISC) receiver triplet states, and therefore, the solvent polarity can modulate their relative energies and ISC rates. In nonpolar solvents, the sub-100 fs lifetime is due to a combination of efficient ISC and internal conversion. In medium-polarity solvents, the S1-state population decays via a competing ISC relaxation mechanism in a biphasic manner, and the ISC rates are found to obey the inverse energy gap law of the strong coupling case. In high-polarity solvents, the S1 state is stabilized to a much lower energy such that ISC becomes energetically infeasible, and the S1 state decays via barrier crossing along the torsion angle of the central ethylenic bond to the nonfluorescent perpendicular configuration. Regardless of the initial S1-state deactivation pathways in various solvents, the excited-state population is ultimately trapped in the metastable T1-state perpendicular configuration, at which a slower ISC occurs to bring the system to the ground state and bifurcate into either trans or cis form of NSB.
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Affiliation(s)
- Peng-Yun Wang
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, 30043, Republic of China.
| | - Yu-Cheng Hsu
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, 30043, Republic of China.
| | - Pin-Hsun Chen
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, 30043, Republic of China.
| | - Guan-Yu Chen
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, 30043, Republic of China.
| | - Yi-Kai Liao
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, 30043, Republic of China.
| | - Po-Yuan Cheng
- Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, 30043, Republic of China.
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Feskov SV, Malykhin RE, Ivanov AI. The Efficiency of Photoinduced Intramolecular Charge Separation from the Second Excited State: What Factors Can Control It? J Phys Chem B 2020; 124:10442-10455. [PMID: 33172263 DOI: 10.1021/acs.jpcb.0c07978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The efficiency of photoinduced charge separation (CS) in electron donor-acceptor compounds is commonly limited due to fast deactivation processes, such as the excited-state internal conversion and ultrafast hot reverse electron transfer to the acceptor, charge recombination (CR). A traditional way to avoid undesired energy losses due to CR is to put the reverse electron transfer into the Marcus inverted region, thus effectively suppressing it. This method, however, is not generally applicable when considering CS from the second locally excited state because the driving force of CR to the first excited state is small, and thus charge recombination is ultrafast and efficient. In this paper, we study the kinetic features of CS/CR from the second locally excited state of the donor using a semiclassical stochastic model of electron transfer. Particular attention is paid to the CS efficiency as well as the influence of the polar environment and intramolecular high-frequency vibrational modes on the kinetics of the charge-separated state. The influence of a number of model parameters on the CS yield and the energy efficiency has been analyzed using the results of numerical simulations. Several simple practical recipes for creating molecular compounds with high CS yields have been suggested. Simulations have also revealed a strong and non-monotonous (double-humped) dependence of both the yield and energy efficiency of CS on the driving force.
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Affiliation(s)
- Serguei V Feskov
- Volgograd State University, University Avenue 100, Volgograd 400062, Russia
| | - Roman E Malykhin
- Volgograd State University, University Avenue 100, Volgograd 400062, Russia
| | - Anatoly I Ivanov
- Volgograd State University, University Avenue 100, Volgograd 400062, Russia
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Gong T, Sui Q, Li P, Meng XF, Zhou LJ, Chen J, Xu J, Wang L, Gao EQ. Versatile and Switchable Responsive Properties of a Lanthanide-Viologen Metal-Organic Framework. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1803468. [PMID: 30624027 DOI: 10.1002/smll.201803468] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Revised: 10/15/2018] [Indexed: 06/09/2023]
Abstract
Metal-organic frameworks (MOFs) provide intriguing platforms for the design of responsive materials. It is challenging to mobilize as many components as possible of a MOF to collaboratively accomplish multiple responsive properties. Here, reversible photochromism, piezochromism, hydrochromism, ionochromism, and luminescence modulation of an ionic Eu(III) MOF is reported furnished by cationic electron-deficient viologen units and exchangeable guest anions. Mechanistically, the extraordinarily versatile responsive properties are owed to electron transfer (ET), charge transfer (CT), and energy transfer, involving viologen as electron acceptor, anion as electron donor, luminescing Eu(III) as energy donor, and anion-viologen CT complex or ET-generated radical as energy acceptor (luminescence quencher). Moreover, guest anions and waters provide flexible handles to control the ET-based responsive properties. Water release/reuptake or exchange with organic solvents can switch on/off the response to light, while reversible anion exchange can disenable or awaken the responses to pressure, light, and water release/reuptake. The impacts of water and anions on ET are justified by the high polarity and hydrogen-bonding capability of water, the different electron donor strength of anions, and the strong I- -viologen CT interactions. The rich responsive behaviors have great implications for applications such as pressure sensors, iodide detection, and chemical logic gates.
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Affiliation(s)
- Teng Gong
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Qi Sui
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Peng Li
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Xian-Fu Meng
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Li-Jiao Zhou
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Jianhua Xu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China
| | - Lin Wang
- Center for High Pressure Science and Technology Advanced Research, Shanghai, 201203, China
| | - En-Qing Gao
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
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Rumble CA, Vauthey E. Structural dynamics of an excited donor–acceptor complex from ultrafast polarized infrared spectroscopy, molecular dynamics simulations, and quantum chemical calculations. Phys Chem Chem Phys 2019; 21:11797-11809. [DOI: 10.1039/c9cp00795d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Infrared anisotropy experiments and mixed quantum/classical computations demonstrate large scale reorientation following excitation of a donor/acceptor complex.
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Affiliation(s)
| | - Eric Vauthey
- Department of Physical Chemistry
- University of Geneva
- CH-1211 Geneva 4
- Switzerland
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