Photochromism of Metal Complexes Composed of Diarylethene Ligands and Zn(II), Mn(II), and Cu(II) Hexafluoroacetylacetonates

Metal complexes composed of bidentate 1,2-bis(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene (1a) and
monodentate 1-(2-methyl-5-phenyl-3-thienyl)-2-(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene (2a) photochromic
ligands and M(hfac)2 (M = Zn(II), Mn(II), and Cu(II)) were prepared, and their photoinduced coordination structural
changes were studied. X-ray crystallographic analyses showed the formation of coordination polymers and discrete
1:2 complexes for bidentate and monodentate ligands, respectively. The complexes underwent reversible photochromic
reactions by alternate irradiation with UV and visible lights in solution as well as in the single-crystalline phase.
Upon photoirradiation with UV and visible light, the ESR spectra of the copper complexes of 1a reversibly changed.
While the open-ring isomer gave an axial-type spectrum, the photogenerated closed-ring isomer showed a rhombic-type spectrum. This indicates that the photoisomerization induced the change in the coordination structure.