Effect of Substituents on TICT Rate in Thioflavin T-Based Fluorescent Molecular Rotors

Electronically-excited states characterized by intramolecular charge-transfer play an essential role in many biological processes and optical devices. The ability to make quantitative ab initio predictions of the relative energetics involved is a challenging yet desirable goal, especially for large molecules in solution. In this work we present a data set of 61 experimental measurements of absorption and emission processes, both in the gas phase and solvents representing a broad range of polarities, which involve intramolecular charge-transfer mediated by a non-zero, “twisted” dihedral angle between one or more donor and acceptor subunits. Among a variety of density functionals investigated within the framework of linear-response theory, the “optimally tuned” LRC-ωPBE functional, which utilizes a system-specific yet non-empirical procedure to specify the range-separation parameter, emerges as the preferred choice. For the entire set of excitation energies, involving changes in dipole moment ranging from 4 to >20 Debye, the mean signed and absolute errors are 0.02 and 0.18 eV, respectively (compared, e.g., to -0.30 and 0.30 for PBE0, 0.44 and 0.47 for LRC-ωPBEh, 0.83 and 0.83 for ωB97X-V). The performance of polarizable continuum solvation models for these charge-transfer excited states is closely examined, and clear trends emerge when measurements corresponding to the four small DMABN-like molecules and a charged species are excluded. We make the case that the large errors found only for small molecules in the gas phase and weak solvents cannot be expected to improve via the optimal tuning procedure, which enforces a condition that is exact only in the wellseparated donor-acceptor limit, and present empirical evidence implicating the outsized importance for small donor-acceptor systems of relaxation effects that cannot be accounted for by linear-response TDDFT within the adiabatic approximation. Finally, we demonstrate the utility of the optimally tuned density functional approach by targeting the charge-transfer states of a large biomimetic model system for light-harvesting structures in Photosystem II.

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Photochemistry of Intramolecular Charge Transfer Excited States in Donor-Acceptor-Substituted Diamines

The Journal of Physical Chemistry ◽

10.1021/j100018a019 ◽

1995 ◽

Vol 99 (18) ◽

pp. 6876-6888 ◽

Cited By ~ 9

Author(s):

Yingsheng Wang ◽

Kirk S. Schanze

Keyword(s):

Charge Transfer ◽

Excited States ◽

Intramolecular Charge Transfer ◽

Donor Acceptor

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A TWO-FORM DESCRIPTION OF PUSH-PULL MOLECULES: CORRELATIONS BETWEEN STRUCTURE, INTRAMOLECULAR CHARGE TRANSFER AND (HYPER) POLARIZABILITIES

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s0218863596000532 ◽

1996 ◽

Vol 05 (04) ◽

pp. 757-765 ◽

Cited By ~ 5

Author(s):

M. BARZOUKAS ◽

A. FORT ◽

M. BLANCHARD-DESCE

Keyword(s):

Charge Transfer ◽

Excited States ◽

Intramolecular Charge Transfer ◽

Ground States ◽

Solvent Polarity ◽

Reaction Field ◽

Donor Acceptor ◽

Semi Empirical ◽

Relevant Factors ◽

Acceptor Molecules

We present a quantum two-form two-state description of donor-acceptor molecules. We single out relevant factors that are characteristic of the molecule and its environment. In addition, we define a parameter which rules the geometry of both ground and excited states. Also, this parameter is proportional to the change in dipole between excited and ground states. We show that correlations between (hyper)polarizabilities and this parameter reproduce remarkably well semi-empirical predictions. We extend this model in order to account for the solvent reaction field. This model helps in the understanding of the dependencies of (hyper)polarizabilities on solvent polarity.

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Predicting Excitation Energies of Twisted Intramolecular Charge-Transfer States with Time-Dependent Density Functional Theory: Comparison with Experimental Measurements in the Gas-Phase and Solvents Ranging from Hexanes to Acetonitrile

10.26434/chemrxiv.12522233 ◽

2020 ◽

Author(s):

James Shee ◽

Martin Head-Gordon

Keyword(s):

Charge Transfer ◽

Gas Phase ◽

Excited States ◽

Linear Response ◽

Density Functional ◽

Intramolecular Charge Transfer ◽

Experimental Measurements ◽

Excitation Energies ◽

Donor And Acceptor ◽

Donor Acceptor

Electronically-excited states characterized by intramolecular charge-transfer play an essential role in many biological processes and optical devices. The ability to make quantitative ab initio predictions of the relative energetics involved is a challenging yet desirable goal, especially for large molecules in solution. In this work we present a data set of 61 experimental measurements of absorption and emission processes, both in the gas phase and solvents representing a broad range of polarities, which involve intramolecular charge-transfer mediated by a non-zero, “twisted” dihedral angle between one or more donor and acceptor subunits. Among a variety of density functionals investigated within the framework of linear-response theory, the “optimally tuned” LRC-ωPBE functional, which utilizes a system-specific yet non-empirical procedure to specify the range-separation parameter, emerges as the preferred choice. For the entire set of excitation energies, involving changes in dipole moment ranging from 4 to >20 Debye, the mean signed and absolute errors are 0.02 and 0.18 eV, respectively (compared, e.g., to -0.30 and 0.30 for PBE0, 0.44 and 0.47 for LRC-ωPBEh, 0.83 and 0.83 for ωB97X-V). The performance of polarizable continuum solvation models for these charge-transfer excited states is closely examined, and clear trends emerge when measurements corresponding to the four small DMABN-like molecules and a charged species are excluded. We make the case that the large errors found only for small molecules in the gas phase and weak solvents cannot be expected to improve via the optimal tuning procedure, which enforces a condition that is exact only in the wellseparated donor-acceptor limit, and present empirical evidence implicating the outsized importance for small donor-acceptor systems of relaxation effects that cannot be accounted for by linear-response TDDFT within the adiabatic approximation. Finally, we demonstrate the utility of the optimally tuned density functional approach by targeting the charge-transfer states of a large biomimetic model system for light-harvesting structures in Photosystem II.

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