A Computational Strategy for the Design of Photochromic Derivatives Based on Diarylethene and Nickel Dithiolene with Large Contrast in Nonlinear Optical Properties
Aggelos Avramopoulos, Robert Zaleśny, Heribert Reis, Μάνθος Γ. Παπαδόπουλος
Abstract
We designed a series of photochromic derivatives by employing density functional method (CAM-B3LYP/6-31G*). These compounds are based on DAE (diarylethenes), both sides of which are bonded with benzene and NiBDT (bis(ethylene-1,2-dithiolato)Ni). These substituents and, in particular, the NiBDT moiety are known to exhibit very large second hyperpolarizability. The objective of this work was to develop, by employing a DFT methodology, a set of rules for designing photochromic materials presenting the following: (i) a large contrast between a series of physical properties—the hyperpolarizabilities (first and second), the IR absorption and the two-photon absorption (TPA) strength—of the “open” and the “closed” isomers and (ii) extremely large nonlinear optical properties. This large contrast may be attained by a light-induced transformation of the “open” to the “closed” isomer, combined with substituents involving an extensive π-electron network and/or strong donor/acceptor pairs.