Dynamics of Radiationless Transitions:  Effects of Displacement−Distortion−Rotation of Potential Energy Surfaces on Internal Conversion Decay Rate Constants<sup>,</sup>

Islampour, Reza; Miralinaghi, Mahsasadat

doi:10.1021/jp073280e

Cited by 22 publications

(33 citation statements)

References 43 publications

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“…Extensive tests on the S 1 ↝ T 1 transitions in thymine, flavone, phenalenone, and free‐base porphyrin have shown that the calculated ISC rates depend only slightly on the particular width of the damping function as long as the VDOS is sufficiently high 136. Along the same lines, general expressions for IC rate constants in the time domain have been derived and applied to various molecular systems 137–140…”

Section: Intersystem Crossing Ratesmentioning

confidence: 97%

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Spin–orbit coupling and intersystem crossing in molecules

Marian

2011

WIREs Comput Mol Sci

723

799

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Many light‐induced molecular processes involve a change in spin state and are formally forbidden in non‐relativistic quantum theory. To make them happen, spin–orbit coupling (SOC) has to be invoked. Intersystem crossing (ISC), the nonradiative transition between two electronic states of different multiplicity, plays a key role in photochemistry and photophysics with a broad range of applications including molecular photonics, biological photosensors, photodynamic therapy, and materials science. Quantum chemistry has become a valuable tool for gaining detailed insight into the mechanisms of ISC. After a short introduction highlighting the importance of ISC and a brief description of the relativistic origins of SOC, this article focusses on approximate SOC operators for practical use in molecular applications and reviews state‐of‐the‐art theoretical methods for evaluating ISC rates. Finally, a few sample applications are discussed that underline the necessity of studying the mechanisms of ISC processes beyond qualitative rules such as the El‐Sayed rules and the energy gap law. © 2011 John Wiley & Sons, Ltd. This article is categorized under: Structure and Mechanism > Molecular Structures

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Section: Intersystem Crossing Ratesmentioning

confidence: 97%

“…Temperature effects are expected to be particularly large for pairs of states with small singlet‐triplet energy gap 14. In the investigation of (spin‐allowed) radiationless transitions, typically a Boltzmann distribution has been assumed in the excited state 108,138,141,142…”

Section: Intersystem Crossing Ratesmentioning

confidence: 99%

Spin–orbit coupling and intersystem crossing in molecules

Marian

2011

WIREs Comput Mol Sci

723

799

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“…TD-FGR has been used to calculate rate constants in quantum processes such as ISC [25,28] and IC [29][30][31][32] and calculated values are known to be in agreement with experiment. However, it has only been applied for unimolecular reactions so far.…”

Section: Adapting Td-fgr For Bimolecular Energy Transfermentioning

confidence: 79%

Quantum effects in photosensitization: The case of singlet oxygen generation by thiothymines

Manae

Hazra

2022

Preprint

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Photosensitization is the indirect electronic excitation of a molecule with the aid of a photosensitizer and is a bimolecular nonradiative energy transfer. In this study, we have attempted to elucidate its mechanism, and we do this by calculating rate constants of photosensitization of oxygen by thiothymines (2-thiothymine, 4-thiothymine and 2,4 dithiothymine). The rate constants have been calculated using two approaches: (a) a classical limit of Fermi's Golden Rule (FGR), and (b) a time-dependent variant of FGR, where the treatment is purely quantum mechanical. The former approach has previously been developed for bimolecular systems and has been applied to the photosensitization reactions studied here. The latter approach, however, has so far only been used for unimolecular reactions, and in this work, we describe how it can be adapted for bimolecular reactions. Experimentally, all three thiothymines are known to have significant singlet oxygen yields, which are indicative of similar rates. Rate constants calculated using the time-dependent variant of FGR are comparable across all three thiothymines and with experiment. While the classical approximation gives reasonable rate constants for 2-thiothymine, it severely underestimates them for 4-thiothymine and 2,4 dithiothymine, by several orders of magnitude. This work indicates the importance of quantum effects in driving photosensitization.

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“…[24] Islampour and Miralinaghi also obtained similar formalism by employing generation function independently in the same year. [47] In 2008, applying TVCF approach, Niu and Shuai further got a more general analytical formalism via abandoning the promoting-mode approximation, [26] and starting from second-order perturbation, Peng et al derived an analytical formalism combining spin-orbit coupling and nonadiabatic coupling for nonradiative decay rate constant between triplet and singlet states. [25] Marian et al investigated the effect of spin-vibronic coupling on the intersystem crossing rate.…”

Section: Hindrance Of Nonradiative Channels In Aggregates the Quantitative Calculation Of Quantum Luminescence Yieldmentioning

confidence: 99%

Molecular mechanism of aggregation‐induced emission

2021

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Deep understanding of the inherent luminescence mechanism is essential for the development of aggregation-induced emission (AIE) materials and applications. We first note that the intermolecular excitonic coupling is much weaker in strength than the intramolecular electron-vibration coupling for a majority of newly termed AIEgens, which leads to the emission peak position insensitive to excitonic coupling, hence the conventional excitonic model for J-aggregation cannot effectively explain their AIE phenomena. Then, using multiscale computational approach coupled with our self-developed thermal vibration correlation function rate formalism and transition-state theory, we quantitatively investigate the aggregation effect on both the radiative and the nonradiative decays of molecular excited states. For radiative decay processes, we propose that the lowest excited state could convert from a transition dipole-forbidden "dark" state to a dipole-allowed "bright" state upon aggregation. For the radiationless processes, we demonstrate the blockage of nonradiative decay via vibration relaxation (BNR-VR) in harmonic region or the removal of nonradiative decay via isomerization (RNR-ISO) or minimum energy crossing point (RNR-MECP) beyond harmonic region in a variety of AIE aggregates. Our theoretical work not only justifies a plethora of experimental results but also makes reliable predictions on molecular design and mechanism that can be experimentally verified. Looking forward, we believe this review will benefit the deep understanding about the universality of AIE phenomenon and further extending the scope of AIE systems with novel applications.

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Dynamics of Radiationless Transitions: Effects of Displacement−Distortion−Rotation of Potential Energy Surfaces on Internal Conversion Decay Rate Constants^,

Cited by 22 publications

References 43 publications

Spin–orbit coupling and intersystem crossing in molecules

Spin–orbit coupling and intersystem crossing in molecules

Quantum effects in photosensitization: The case of singlet oxygen generation by thiothymines

Molecular mechanism of aggregation‐induced emission

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Dynamics of Radiationless Transitions: Effects of Displacement−Distortion−Rotation of Potential Energy Surfaces on Internal Conversion Decay Rate Constants,

Cited by 22 publications

References 43 publications

Spin–orbit coupling and intersystem crossing in molecules

Spin–orbit coupling and intersystem crossing in molecules

Quantum effects in photosensitization: The case of singlet oxygen generation by thiothymines

Molecular mechanism of aggregation‐induced emission

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Product

Resources

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Dynamics of Radiationless Transitions: Effects of Displacement−Distortion−Rotation of Potential Energy Surfaces on Internal Conversion Decay Rate Constants^,