Studies On Syntheses, Characterization, Luminescent Properties Of Metal Complexes With Bis(imino)pyridine Ligands

Recently, Luminescent coordination compounds with nitrogen-containing ligands have attracted much attention due to their good performance in sensor technologies and electroluminescent devices. The d10 metal complexes with nitrogen-containing ligands have been synthesized and their luminescent behavior studied. The change of center metal ion, the size of π-conjugated system of the ligand and the electronic effect of substituents on the ligand are important factors for modulating its luminescent properties. The frequency and intensity of the luminescence of the complex are modulated via the design of the ligand-modified and center metal, so that luminescent properties are improved based on metal coordination compounds.In recent years, more researches have been done on the syntheses, structures and catalytical properties of meal complexes with bis(imino)pyridyl ligands, while all kinds of bis(imino)pyridine are also good tridentate N-donating ligands with large π-conjugating system, they should be good luminescent compounds. However, no reports on the luminecent properties of these ligands and their complexes hase been found, we are very interested in the luminescent properties of these compounds.Two new Zn (II) complexes of 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyrid-ine(L2), 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine(L3) were synthesized. These two complexes have the formulas Zn(L2)Cl2(Zn2) and Zn(L3)Cl2·CH3CN(Zn3), respectively. Crystal structures of complexes Zn2 and Zn3 were determined by single-crystal X-ray diffraction. Crystallographic studies on Zn2 and Zn3 reveal both complexes to be five-coordinate with geometries that can be best described as distorted trigonal bipyramidal. Complexes Zn2 and Zn3 have blue luminescence at room temperature in solution and the solid state. The blue luminescence of the complexes is due to π*→ π transition centered on the ligands. The Zn (II) centers play a key role in enhancing fluorescent emission of the ligands. Four new Cd (II) complexes of 2,6-bis[(1-phenylimino)ethyl]pyridine (L1), 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (L2), 2,6-bis[1-(2,6-dimethyl-phenylimino)ethyl]pyridine (L3), 2,6-bis[1-(2-methylphenylimino)ethyl]pyridine (L4) were synthesized. These four complexes have the formulas Cd(L1)Cl2·1.5CH3CN (Cd1), Cd(L2)Cl2 (Cd2), Cd(L3)Cl2·CH3CN (Cd3), and Cd(L4)Cl2·CH3CN (Cd4), respectively. The molecular structures of complexes Cd1–Cd4 were determined by single-crystal X-ray diffraction. Crystallographic studies on Cd1–Cd4 reveal all four complexes to be five-coordinate with geometries that can be best described as distorted trigonal bipyramidal. Four complexes are luminescent at room temperature in solution and the solid state. At 298 K in dichloromethane solution, all compounds have fluorescent emissions at ca. 368–409 nm. Fluorescent emission of these compounds originates from π*–π transitions centered on the ligands. The Cd (II) centers play a key role in enhancing fluorescent emission of the ligands. Four new five-coordinated 2,6-bis(imino)pyridyl mercury complexes, [2,6-(ArN=CMe)2C5H3NHgCl2·nCH3CN] (Ar = C6H5, n = 1.5, Hg1; Ar = 2,6-iPr2C6H3, n = 0, Hg2; Ar = 2,6-Me2C6H3, n = 1, Hg3; Ar = 2-MeC6H4, n = 1, Hg4 ), were synthesized in good yield by reactions of the corresponding bis(imino)pyridine ligands with HgCl2 in CH3CN solution. Crystal structures of complexes Hg1–Hg4 were determined by single-crystal X-ray diffraction. In all complexes, the metal center is tridentately chelated by ligand and further coordinated by two chlorine atoms, resulting in a distorted trigonal bipyramidal geometry. All complexes are luminescent in both solution and the solid state. At 293K in CH2Cl2 solution, the fluorescent emission maxima for complexes Hg1–Hg4 are at λ = 395, 400, 407, and 403nm, respectively, which can be attributed to ligand-centered π*–π transitions. The mercury (II) centers play a key role in enhancing fluorescent emission of the ligands. Since Brookhart et al. found that nick...