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

Abstract

A family of hydrazone-based photochromic derivatives consisting a hydrazone switching and phenyl groups with R1 and R2 (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 (βtot) 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 (ΔEge) and the narrower energy band gap (Egap) of frontier molecular orbital. Furthermore, the push-pull complexes 4 may be potential NLO materials due to the larger βtot values, for example, the βtot values of 4Z and 4E are 1.6 × 104 a.u. and 9.3 × 103 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.