Fluorescent 7-Substituted Coumarin Dyes: Solvatochromism and NLO Studies.

The effect of three substituents N,N-diethylamine, carbazole and diphenylamine at the 7 position of coumarin on linear and nonlinear optical properties are studied using absorption and emission solvatochromism, and DFT. By varying the substituent 53 nm red shift is achieved in emission. The polarity plots with regression close to unity revealed good charge transfer in the system. Solvent polarizability and dipolarity are mainly responsible for solvatochromic shift as proved by multilinear regression analysis. General Mulliken Hush analysis shows diphenylamine substituent leads to more charge separation in compound 6c. The hyperpolarizabilities are evaluated by quantum mechanical calculations. Structure of the compounds are optimized at B3LYP/6-31G(d) level and NLO computations are done using range separated hybrid functionals with large basis sets. Second order hyperpolarizability (γ) found 589.27 × 10-36, 841.29 × 10-36 and 1043.00 × 10-36 e.s.u for the compounds 6a, 6b and 6c respectively.