Exploring Second-Order Nonlinear Optical Properties and Switching Ability of a Series of Dithienylethene-Containing, Cyclometalated Platinum Complexes: A Theoretical Investigation

The second-order nonlinear optical (NLO) properties of a series of dithienylethene- (DTE-) containing Pt­(II) complexes have been investigated by density functional theory calculations. The first hyperpolarizabilities β of studied systems can be greatly enhanced by simple ligand substitutions. Because of the nature of DTE units, the β values also can be varied by the use of lights in the studied systems. The highest β difference between photoisomers can over 1000 × 10^–30 esu, with the contrast around five times. Thus, the studied systems can act as effective photoswitchable second-order NLO materials. The time-dependent density functional theory calculations revealed that the charge transfer patterns of studied systems have special characters compared to other reported DTE-containing NLO switched chromogens, the DTE units mainly act as electron-donors in studied systems, and the variation of β can be viewed as alternation of donor abilities of DTE units; thus, our work also proposed a new mechanism for designing photoswitched NLO multifunctional materials.