Photophysical properties and fluorosolvatochromism of D–p–A thiophene based derivatives
Ahmed M.M. Alazaly; Hussain A. Z. Sabek; Dina Salah; Hesham S. Abdel-Samad,; Mohamed A. Ismail; Ayman A. Abdel-Shafi;
Abstract
Solvation-dependent photophysical properties of two push–pull thiophene-based compounds with
donor–p–acceptor (D–p–A) structures were investigated using absorption, fluorescence emission and
time resolved spectroscopy, and supported by different solvation models. Intramolecular charge transfer
characteristics of the structurally similar 2-fluoro-4-(5-(4-methoxyphenyl)thiophen-2-yl)benzonitrile
(MOT) and 4-(5-(4-(dimethylamino)phenyl)thiophen-2-yl)-2-fluorobenzonitrile (DMAT) were
investigated. Significant enhancement of intramolecular charge transfer strength has been observed
through molecular structure modification of the electron donating group from a methoxy to
dimethylamine group. Ground state absorption spectra show a small red shift of about 10 nm and 18 nm
while the fluorescence emission spectra show a large red shift of about 66 nm and 162 nm on changing
from the nonpolar cyclohexane to the aprotic polar DMSO for MOT and DMAT, respectively. Dipole
moment change from the ground state to the charge transfer excited state is calculated to be 6.6 D in
MOT and 9.0 D in DMAT. The fluorescence quantum yield, fluorescence lifetime and the derived
radiative and non-radiative rate constants were found to be better correlated to the emission energy
rather than any of the solvent properties. Three multi-parametric relationships were used in the
interpretation of the specific versus non-specific solute–solvent interactions, namely, Kamlet–Taft,
Catal´an and Laurence et al. models. The findings of these approaches are used to extract useful
information about different aspects of solvent effects on the photophysical properties of the two studied
compounds. Kamlet–Taft solvatochromic model indicates that non-specific interactions are dominant in
controlling the photophysical properties. Catal´an's solvent dipolarity/polarizability parameter is found to
play a significant role in solvatochromic behaviour which is also designated by the Laurence model
donor–p–acceptor (D–p–A) structures were investigated using absorption, fluorescence emission and
time resolved spectroscopy, and supported by different solvation models. Intramolecular charge transfer
characteristics of the structurally similar 2-fluoro-4-(5-(4-methoxyphenyl)thiophen-2-yl)benzonitrile
(MOT) and 4-(5-(4-(dimethylamino)phenyl)thiophen-2-yl)-2-fluorobenzonitrile (DMAT) were
investigated. Significant enhancement of intramolecular charge transfer strength has been observed
through molecular structure modification of the electron donating group from a methoxy to
dimethylamine group. Ground state absorption spectra show a small red shift of about 10 nm and 18 nm
while the fluorescence emission spectra show a large red shift of about 66 nm and 162 nm on changing
from the nonpolar cyclohexane to the aprotic polar DMSO for MOT and DMAT, respectively. Dipole
moment change from the ground state to the charge transfer excited state is calculated to be 6.6 D in
MOT and 9.0 D in DMAT. The fluorescence quantum yield, fluorescence lifetime and the derived
radiative and non-radiative rate constants were found to be better correlated to the emission energy
rather than any of the solvent properties. Three multi-parametric relationships were used in the
interpretation of the specific versus non-specific solute–solvent interactions, namely, Kamlet–Taft,
Catal´an and Laurence et al. models. The findings of these approaches are used to extract useful
information about different aspects of solvent effects on the photophysical properties of the two studied
compounds. Kamlet–Taft solvatochromic model indicates that non-specific interactions are dominant in
controlling the photophysical properties. Catal´an's solvent dipolarity/polarizability parameter is found to
play a significant role in solvatochromic behaviour which is also designated by the Laurence model
Other data
Title | Photophysical properties and fluorosolvatochromism of D–p–A thiophene based derivatives | Authors | Ahmed M.M. Alazaly ; Hussain A. Z. Sabek; Dina Salah; Hesham S. Abdel-Samad,; Mohamed A. Ismail; Ayman A. Abdel-Shafi | Issue Date | 24-Nov-2020 | Publisher | The Royal Society of Chemistry | Journal | RSC Advances | Volume | 10 | Issue | 71 | Start page | 43459 | End page | 43471 | DOI | https://doi.org/10.1039/D0RA08433F |
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