Switchable second-order nonlinear optical response of platinum-sensitized dithienylethenes

The electronic structure and the nonlinear optical (NLO) properties of a series of platinum-sensitized dithienylethenes (DTEs) were investigated by using the density functional theory (DFT) method. DFT calculations reveal that the second-order NLO properties of complexes significantly increase with the DTE ligand being directly linked with terpyridine-Pt(II) complexes. Due to the good pi-conjugated characteristics, closed-ring complexes possess much larger second-order NLO properties than the corresponding open-ring complexes. The computational beta(tot) values are in the order of 3c (894.8 x 10(-30) esu) > 3o (174.4 x 10(-30) esu) > 4c (27.2 x 10(-30) esu) approximate to 4o (27.2 x 10(-30) esu) > 1 (19.9 x 10(-30) esu) > 2c (9.4 x 10(-30) esu) > 2o (3.1 x 10(-30) esu). Among all calculated platinum-sensitized dithienylethenes, 3c has the largest second-order NLO properties. The 4c and 4o have almost the same beta(tot) values and the beta(tot) value of 4o is slightly larger than that of 2o because the ether bonds can significantly prevent charge transfer within the complexes.