Solvatochromic behavior of D-π-A bithiophene carbonitrile derivatives

Abstract

Photophysical properties of 5-(5-(4-methoxyphenyl)thiophen-2-yl)thiophene-2-carbonitrile (MTTC) and 5-(5-(3,5-dimethoxyphenyl)thiophen-2-yl)thiophene-2-carbonitrile (DMTTC) were investigated in different solvents. The photophysical properties of MTTC and DMTTC were correlated with the solvent polarity parameters viz., ETN and reaction field factor Δf. Dependence of the photophysical properties on Δf and ETN was best studied when the solvents are classified to protic and aprotic solvents. Dipole moment changes, Δμ, were determined using Lippert–Mataga and Reichardt-Ravi equation in protic and aprotic solvents. Multiple linear regression analysis of solvent dependent photophysical parameters using Kamlet-Taft, Catalán and Laurence et al. have shown that specific hydrogen bonding interactions and non-specific dipolar interaction play important roles in determining the photophysical properties of MTTC and DMTTC. Kamlet-Taft and Catalán treatments have shown that the non-specific interactions have high impact on the emission energy, νf, and the non-radiative rate constants, knr, while the specific interactions dominate the absorption energy, νa, Stokes shift, Δν, and the radiative rate constants, kr. Laurence treatment shows that the specific interactions have the important contribution only on the absorption energy, νa, while the dispersion and induction interactions, DI, and ES parameter have high impact on the emission energy, νf, the Stokes shift, Δν, radiative, kr, and non-radiative rate constants, knr.