Investigation of photophysical, structural aspects and nonlinear optical properties of Foron blue SR analogs using Density Functional Theory (DFT)

Analogs of 2-[(2Z)-2-[[4-(dihexylamino)-2-methylphenyl]methylidene]-1,1-dioxo-1-benzothiophen-3-ylidene]propanedinitrile (Foron blue SR, Disperse Blue 354) are studied in terms of photophysical, structural aspects and its nonlinear optical properties evaluated by using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT). The structures were optimized by using function B3LYP and basis set used was 6-31G(d). Polarizability (), first and second order hyperpolarizability ( and ) was determined by three density functionals B3LYP, CAM-B3LYP and BHandHLYP. B3LYP functional and the basis set 6-311+G(d,p) shows high values of , and . The B3LYP functional gives the highest first order hyperpolarizability value for (Z)-2-(2-(4-(dimethylamino)benzylidene)-1,1-dioxidobenzo[b]thiophen-3(2H)-ylidene)malononitrile (3a) is 373.31x10-30 e.s.u and 486.32x10-30 e.s.u in ethylacetate and dimethylformamide respectively. Effect of bond length alteration (BLA) and bond order alteration (BOA) on first order hyperpolarizability was evaluated. Intrinsic hyperpolarizability shows the compound (Z)-2-(4-(dimethylamino)benzylidene)benzo[b]thiophen-3(2H)-one 1,1-dioxide (1a) intrinsically good. Perturbation potential is found to decrease as absorption energy deceases and hyperpolarizability increases.Graphic Abstract: Analogs of Foron blue SR which is also known as Disperse Blue 354 are studied in terms of photophysical, structural aspects and its nonlinear optical properties evaluated by using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT). The structures were optimized by using the functional, B3LYP and the basis set used was 6-31G(d). Polarizability (), first and second order hyperpolarizability ( and ) were determined by three density functionals B3LYP, CAM-B3LYP and BHandHLYP. B3LYP and the basis set 6-311+G(d,p) shows high values of , and . The B3LYP functional gives the highest first order hyperpolarizability for (Z)-2-(2-(4-(dimethylamino)benzylidene)-1,1-dioxidobenzo[b]thiophen-3(2H)-ylidene)malononitrile (3a), 373.31x10-30 e.s.u and 486.32x10-30 e.s.u in ethylacetate and dimethylformamide respectively. Effect of bond length alteration (BLA) and bond order alteration (BOA) on first order hyperpolarizability was evaluated. Intrinsic hyperpolarizability shows that the compound (Z)-2-(4-(dimethylamino)benzylidene)benzo[b]thiophen-3(2H)-one 1,1-dioxide (1a) intrinsically good. Perturbation potential is found to decrease as absorption energy deceases and hyperpolarizability increases.