D-π-A-π-D coumarin hybrids derived from arylamine donors: DFT and Z-scan studies

Abstract

Four new D-π-A-π-D hybrid dyes containing coumarin as a major donor (4a-b and 5a-b) together with carbazole and triphenylamine as auxiliary donor having dicyanovinylene as a common acceptor are synthesized and studied in terms of photophysical, charge transfer, and non-linear optical properties. Optical properties of hybrid dyes considerably shifted towards red to NIR region upon increasing the solvent polarity. Highest emission solvatochromism is observed for dye 5b (∼137 nm) from nonpolar to polar solvent. Charge transfer is well established using solvatochromism, natural bond orbital analysis, and HOMO-LUMO energy gap. Two photon absorption is calculated using the theoretical model and dye 4b shows high σ2PA in the range 186–464 GM. Non-linear optical properties were investigated using solvatochromic two-level model, computationally using two global hybrid functionls (B3LYP and BHHLYP) and four range separated hybrid functionals (CAM-B3LYP, ωB97, ωB97× and ωB97XD) and Z-scan technique. The computed values of the second order hyperpolarizability (γ0) and first order hyperpolarizability (β0) are high in the range of 993–5473 × 10−36 esu and 240-806 × 10−30 esu respectively for these dyes compared to urea. Z-scan results reveal saturable kind of behavior for 4a and 4b, whereas 5a and 5b show reverse saturable kind of behavior in acetone and ethanol and hence give optical limiting values. Thus, from the experimental and theoretical data, these dyes can be considered as promising candidates for NLO application in material science.