Evaluating the Extent of Intramolecular Charge Transfer in the Excited States of Rhenium(I) Donor–Acceptor Complexes with Time-Resolved Vibrational Spectroscopy

2013 ◽  
Vol 117 (49) ◽  
pp. 15903-15916 ◽  
Author(s):  
Yuankai Yue ◽  
Tod Grusenmeyer ◽  
Zheng Ma ◽  
Peng Zhang ◽  
Tri Tat Pham ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Vibrational Spectroscopy ◽  
Intramolecular Charge Transfer ◽  
Time Resolved ◽  
Donor Acceptor

scholarly journals 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

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.

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

1996 ◽  
Vol 05 (04) ◽  
pp. 757-765 ◽  
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.

scholarly journals 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

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.

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

2019 ◽  
Vol 18 (03n04) ◽  
pp. 1940046
Author(s):  
V. I. Stsiapura ◽  
S. D. Gogoleva ◽  
A. A. Maskevich ◽  
O. V. Buganov ◽  
S. A. Tikhomirov ◽  
...  
Keyword(s):  
Excited States ◽  
Intramolecular Charge Transfer ◽  
Thioflavin T ◽  
Molecular Rotors ◽  
Molecular Fragments ◽  
Time Resolved ◽  
Fluorescent Molecular Rotors ◽  
Methoxy Groups ◽  
Donor Acceptor ◽  
Mutual Rotation

New fluorescent molecular rotors (FMRs) were developed by modification of the Thioflavin T (ThT) structure via introduction of methyl and methoxy groups. Effects of the substituents on fluorescence properties and twisted intramolecular charge transfer (TICT) rate in the excited state of the molecules were studied using steady-state fluorescence and time-resolved absorption spectroscopy. Quantum chemical calculations of the molecules in the ground and excited states were carried out to aid interpretation of the experimental results. Only cationic forms of ThT derivatives have FMR properties and exhibit viscosity-dependent fluorescence. The TICT rate was found to be affected by the size of the molecular fragments, which experience mutual rotation, dihedral angle [Formula: see text] between the fragments in the ground state as well as their donor/acceptor properties.

scholarly journals Rational Design of TADF Polymers Using a Donor-Acceptor Monomer with Enhanced TADF Efficiency Induced by the Energy Alignment of Charge Transfer and Local Triplet Excited States

2016 ◽  
Vol 4 (4) ◽  
pp. 597-607 ◽  
Author(s):  
Roberto S. Nobuyasu ◽  
Zhongjie Ren ◽  
Gareth C. Griffiths ◽  
Andrei S. Batsanov ◽  
Przemyslaw Data ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Rational Design ◽  
Donor Acceptor ◽  
Triplet Excited States

scholarly journals Tuning of Hyperpolarizability, One- and Two-Photon Absorption of D-A and D-A-A Type Intramolecular Charge Transfer Based Sensors

2019 ◽  
Author(s):  
Pralok K. Samanta ◽  
Md Mehboob Alam ◽  
Ramprasad Misra ◽  
Swapan K. Pati
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Photon Absorption ◽  
First Hyperpolarizability ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Nlo Response ◽  
Donor Acceptor

Solvents play an important role in shaping the intramolecular charge transfer (ICT) properties of π-conjugated molecules, which in turn can affect their one-photon absorption (OPA) and two-photon absorption (TPA) as well as the static (hyper)polarizabilities. Here, we study the effect of solvent and donor-acceptor arrangement on linear and nonlinear optical (NLO) response properties of two novel ICT-based fluorescent sensors, one consisting of hemicyanine and dimethylaniline as electron withdrawing and donating groups (molecule 1), respectively and its boron-dipyrromethene (BODIPY, molecule 2)-fused counterpart (molecule 3). Density functional theoretical (DFT) calculations using long-range corrected CAM-B3LYP and M06-2X functionals, suitable for studying properties of ICT molecules, are employed to calculate the desired properties. The dipole moment (µ) as well as the total first hyperpolarizability (β<sub>total</sub>) of the studied molecules in the gas phase is dominantly dictated by the component in the direction of charge transfer. The ratios of vector component of first hyperpolarizability (β<sub>vec</sub>) to β<sub>total</sub> also reveal unidirectional charge transfer process. The properties of the medium significantly affect the OPA, hyperpolarizability and TPA properties of the studied molecules. Time dependent DFT (TDDFT) calculations suggest interchanging between two lowest excited states of molecule 3 from the gas phase to salvation. The direction of charge polarization and dominant transitions among molecular orbitals involved in the OPA and TPA processes are studied. The results presented are expected to be useful in tuning the NLO response of many ICT-based chromophores, especially those with BODIPY acceptors.<br>

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