Optical properties of organic nonlinear optical crystal--a combined experimental and theoretical study.

The optical properties of the synthesized imidazole derivative, 1-(4-methoxyphenyl)-4,5-diphenyl-2-styryl-1H-imidazole, has been studied both experimentally and theoretically. Fluorescence enhancement have been found in the presence of transition metal ions and this may result from the suppression of radiationless transitions from the n-π* state in the chemosensors. Quantum chemical calculations of heat of formation, optimized geometry, NLO, HOMO-LUMO, MEP and NBO analysis of 1-(4-methoxyphenyl)-4,5-diphenyl-2-styryl-1H-imidazole (mpdsi) have been carried out by using density functional theory (DFT/B3LYP) method with 6-31G(d,p) as basis set. This chromophore possess more appropriate ratio of off-diagonal versus diagonal β tensorial component (r=β(xyy)/β(xxx)=-0.002) which reflects the inplane non-linearity anisotropy. Since they have largest μβ(0) value, the reported imidazole can be used as potential NLO material. The solvent effect on the absorption and fluorescence has been analyzed simultaneously.