Solvatochromic effect on UV–vis absorption and fluorescence emission spectra, second- and third-order nonlinear optical properties of dicyanovinyl-substituted thienylpyrroles: DFT and TDDFT study

Abstract

The nonlinear optical properties of dicyanovinyl-thienylpyrroles 1–6 compounds were investigated by the determining of the first-order molecular static hyperpolarizability (β) and the second-order molecular static hyperpolarizability (γ) in the ground state by using the HSEh1PBE/6-311G(d,p) level of density functional theory (DFT). The photophysical behavior of compounds 1 and 5 in polar and non-polar solvents was studied by using UV–vis absorption and fluorescence emission spectroscopies. In order to investigate the effects of these solvents, the time-dependent density functional theory (TD-DFT) calculations with the polarizable continuum model (PCM) in the excited state were performed. The UV–Vis absorption and fluorescence emission spectra for compound 5 were also simulated using TD-HSEh1PBE/6-311G(d,p) level, and the major contributions to the electronic transitions for compounds 1–6 were obtained. The β0 value (18.74×10−30esu) calculated by using HSEh1PBE/6-311G(d,p) for compound 2 is 1.49 times lower than the experimental value (28×10−30esu), and 2.34 times greater than pNA value (8×10−30esu). The β and γ parameters for compound 2 is lower than 1 and 3–6 due to electron donating pyrrole ring and electron accepting dicyanovinyl group. Moreover, we used the hybrid DFT methods (B3LYP, M062X, CAM-B3LYP and BHandHLYP) to show the accuracy for first static hyperpolarizability values for compounds 1–6. The β0 parameter for compound 5 in both polar and non-polar solvents was examined by using two level model.