Photochromic Alkynes as Versatile Building Blocks for Metal Alkynyl Systems: Design, Synthesis, and Photochromic Studies of Diarylethene-Containing Platinum(II) Phosphine Alkynyl Complexes

The synthesis of newly designed photochromic dithienylethene-containing ethynylthiophene and ethynylthieno[3,2-b]thiophene has been described, and their incorporation as versatile ligands into the platinum(II) phosphine system was demonstrated. All platinum(II) complexes have been successfully characterized by ¹H and ³¹P NMR spectroscopies, positive fast atom bombardment (FAB) mass spectrometry, as well as elemental analysis. One of the complexes has been characterized by X-ray crystallography. Their photophysical, photochromic, and electrochemical properties have been studied. Upon photoexcitation, all the photochromic diarylethene-containing alkynes and platinum(II) complexes exhibited reversible photochromism. The thermal bleaching kinetic of complex 6 was studied in toluene at 298 and 313 K. Complexes 1, 3, and 4, which contained the labile chloro- ligand, represent a new class of versatile building blocks for photoswitchable functional materials.