A mononuclear Dy(iii) complex incorporating the dithienylethene unit: crystalline-phase photochromism, magnetic and luminescent properties

Abstract

A new dithienylethene compound 2-(4-diethylphosphonophenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (dbi) has been synthesized and applied for the coordination-assembly generation of a mononuclear complex [Dy(hfac)₃(dbi)₂]·CH₃OH (1) (hfac = hexafluoroacetylacetonate), in which dbi ligands coordinate to Dy(III) ion through phosphoryl oxygen atoms. In the crystal structure of dbi, each molecule shows a parallel conformation, and neighboring molecules are linked into an interesting helical chain through hydrogen bonds. In contrast, each dbi ligand in 1 exhibits a photoactive antiparallel conformation, thus resulting in crystalline-phase photochromism (CPP) behavior of 1. Before and after CPP reaction, 1 shows different magnetic and luminescence properties. After irradiation with 365 nm light, the shape of the χ_MT vs. T plot revealed drastic changes, and field-induced χ_M′′ peaks were observed. Compound 1 exhibits ligand- and Dy(III)-centered fluorescence emissions. The irradiation with 365 nm light resulted in the red shift of dbi-centered emissions, and the decrease in intensity of Dy(III)-centered emission.