Photochromic DTE-Substituted-1,3-di(2-pyridyl)benzene Platinum(II) Complexes: Photomodulation of Luminescence and Second-Order Nonlinear Optical Properties

We disclose a new family of photochromic cyclometalated platinum(II) complexes (PtDTE1 and PtDTE2), where a dithienylethene (DTE) unit is connected at the para-position of the central phenyl ring of (N boolean AND C boolean AND N) cyclometalated ligand, through two different linkages. Their syntheses are presented along with the X-ray characterizations of both the open and closed isomers of PtDTE1. The investigation of their photophysical properties is made, including absorption, photochromism, emission, and second-order nonlinear properties. We report a quantitative photoisomerization for both PtDTE1 and PtDTE2, irrespective of the nature of the connecting mode between the DTE unit and the platinum(II) moiety. The efficient photochromism allows a significant NLO photomodulation, both in solution and in thin films. In addition, we show that the photoluminescence of the PtDTE1 and PtDTE2 can be controlled by the open/closed isomerization of the DTE unit.