Synthesis and characterization of new copper(II) and nickel(II) complexes of 3-(2′-hydroxyphenyl)-1,2,4-triazine derivatives

The copper(II) and nickel(II) complexes of 5,6-diphenyl-3-(2′-hydroxyphenyl)-1,2,4-triazine, noted HLH, and 5,6-bis (4-methoxyphenyl)-3-(2′-hydroxyphenyl)-1,2,4-triazine, noted HLOMe, have been synthesized from copper(II) acetate in CH2Cl2 and nickel(II) nitrate in acetone with an excess of previously deprotonated triazine. The new complexes [Cu(LH)2]·H2O (1), [Cu(LOMe)2]·2H2O (2), Na[Ni(LH)3]·2H2O·(CH3)2CO (3), and Na[Ni(LOMe)3]·2H2O (4) were isolated as pure solids and characterized by IR, UV–Vis, elemental analysis and mass spectra. Copper(II) complexes 1 and 2 were studied by EPR, in frozen solutions. In accordance with the spectroscopic data obtained by UV–Vis, the stoichiometry of the complexes was found to be 1:2 for Cu2+:LH,OMe with a square planar environment for the metal centre. Crystals of HLOMe and 3 were obtained and studied by single crystal X-ray diffraction. The structure of HLOMe exhibits a strong deviation from planarity of the two p-methoxyphenyl rings with respect to the triazine ring while the 2-hydroxyphenyl fragment is almost coplanar. Intramolecular hydrogen bonding between one of the N atoms of the triazine ring and the phenol can explain this restraint. For 3, three LH bidentate triazines are coordinated to the nickel ion in a distorted octahedral manner.