Orange-Red Fluorescent (Partially Rigidified) Donor-π-(rigidified)-Acceptor System - Computational Studies

D-π-A chromophore derived coumarins are studied using "DFT and TD-DFT" to compute vertical excitation as well as NLO properties using "global hybrid" (GH) functionals B3LYP and BHandHLYP and "range separated hybrid" (RSH) functionals CAM B3LY', wB97, wB97X, and wB97XD with basis set 6-311++G(d,p) and "correlation consistence polarized valence double and triple zeta" cc-pVDZ and cc-pVTZ respectively in the gas phase and two solvents, N,N-Dimethylformamide (DMF) and ethyl acetate (EA). The trends in absorption and emission values calculated by TD-DFT using all the above mentioned functional and basis sets were studied and it was observed that the trends seen in the computed parameters using B3LYP, BHandHLYP and CAM B3LYP are in good agreement with the trends in experimental values. DFT calculations were performed to determine "static dipole moment" (μ), "linear polarizability" (α), "first order hyperpolarizability" (β₀), "second order hyperpolarizability" (γ). We have calculated the mean average errors in dipole moment, linear polarizability, first and second hyperpolarizability and vertical excitation. We have observed large values of 'first order hyperpolarizability' (301-938 × 10^-30 e.s.u) and 'second order hyperpolarizability' (684-2498 × 10^-34) and they can act as good nonlinear optical materials. Also, vibrational contribution indicates the red shifted absorption and emission in 2c. They show higher values of electrophilicity index which indicates the stability and reactivity of molecules.