The second-order nonlinear optical property of hydrazones-based photochromic complexes: A DFT study

A family of hydrazone-based photochromic derivatives consisting a hydrazone switching and phenyl groups with R-1 and R-2 (R = H, -NO2 and -NMe2) can be induced by light to form two isomers (Z-type and E-type). In this paper, we discussed detailedly the impacts of structural change on UV-Vis absorption spectra, electronic transition properties and the first hyperpolarizability (beta(tot)) by using density functional theory (DFT) methods. The calculation results showed that second-order NLO responses of Z-type complexes are stronger than that of corresponding E-type complexes due to the red-shift of absorption spectra, the smaller electronic transition energy (Delta E-ge) and the narrower energy band gap (E-gap) of frontier molecular orbital. Furthermore, the push-pull complexes 4 may be potential NLO materials due to the larger beta(tot) values, for example, the beta(tot) values of 4Z and 4E are 1.6 x 10(4) a.u. and 9.3 x 10(3) a.u., respectively. It is that the donor (D) and acceptor (A) groups are dominated by the interaction of D and A group via intramolecular charge transition (CT). We hope that this research will introduce a new relation between the structure and the photochromic nonlinear optical activity. (C) 2020 Elsevier B.V. All rights reserved.