No abstract

Based on two new bisthienylethenes containing N,O-donor binding sites, 2-(2-hydroxy-5-bromo-phenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (BrLH) and 2-(2-hydroxy-5-diethylphosphono-phenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (PLH), multifunctional mononuclear complexes Co(BrL)2·3CH3OH (1) and Co(PL)2·2CH3OH (2) have been synthesized and characterized by crystallographic analysis. In the molecular structures of 1 and 2, the Co(II) ion adopts a distorted tetrahedral coordination geometry, and is coordinated by two nonequivalent bisthienylethene molecules (BrL− in 1, PL− in 2), showing non-photoactive parallel and photoactive antiparallel conformations, respectively. Compounds 1 and 2 show a distinct distortion of Co(II) coordination geometry, with bond angles of N–Co–N = 112.71(12)° and O–Co–O = 99.87(11)° for 1 and N–Co–N = 119.93(12)° and O–Co–O = 107.31(13)° for 2. Thus, 1 and 2 revealed different magnetic behaviors, which are demonstrated by the χMT vs. T plots, and the frequency dependence of the χ′M and χ′′M signals at low temperature. Besides the field-induced slow magnetic relaxation, both 1 and 2 also showed photochromic behavior. Upon irradiation with 360 nm light for 1 and 343 nm light for 2, their CH2Cl2–CH3CN solutions could change color from being nearly colorless to blue purple. It was demonstrated that the substituent groups of Br atom and –PO(OEt)2 in 1 and 2, respectively, could significantly influence their crystal structures, magnetic relaxations and photochromic properties.

Bisthienylethene hnbdtiH and its heteroleptic complexes [Ir(dfppy)2(hnbdti)]·2CH3OH (1) and [Ir(ppy)2(hnbdti)]·CH3OH (2) were synthesized and characterized by crystal structures. Aggregation-induced phosphorescence emission was observed in 1.

A new dithienylethene compound 2-(4-diethylphosphonophenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1Himidazole (dbi) has been synthesized and applied for the coordination-assembly generation of a mononuclear complex [Dy(hfac) 3 (dbi) 2 ]$CH 3 OH (1) (hfac ¼ 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 c M T vs. T plot revealed drastic changes, and field-induced c M 00 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.