Solvent dependence of electronic transition intensities

We have investigated the solvent-dependence of structural changes along with intersystem crossing of a thermally activated delayed fluorescence (TADF) molecule, 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (o-3CzBN), in toluene, tetrahydrofuran, and acetonitrile solutions using time-resolved infrared (TR-IR) spectroscopy and DFT calculations. We found that the geometries of the S1 and T1 states are very similar in all solvents though the photophysical properties mostly depend on the solvent. In addition, the time-dependent DFT calculations based on these geometries suggested that the thermally activated delayed fluorescence process of o-3CzBN is governed more by the higher-lying excited states than by the structural changes in the excited states.<br>

Download Full-text

A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

10.26434/chemrxiv.8028134.v1 ◽

2019 ◽

Author(s):

Anshuman Kumar ◽

Reinhard Schweitzer-Stenner ◽

Bryan Wong

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Cd Spectra ◽

Functional Theory ◽

Polyproline Ii ◽

Solvent Dependence ◽

Explicit Consideration ◽

New Interpretation ◽

Implicit And Explicit ◽

Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

Download Full-text

A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

10.26434/chemrxiv.8028134 ◽

2019 ◽

Author(s):

Anshuman Kumar ◽

Reinhard Schweitzer-Stenner ◽

Bryan Wong

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Cd Spectra ◽

Functional Theory ◽

Polyproline Ii ◽

Solvent Dependence ◽

Explicit Consideration ◽

New Interpretation ◽

Implicit And Explicit ◽

Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

Download Full-text