Synthesis and characterization of bis-acylhydrazone derivatives as tetradentate ligands and their dinuclear metal(II) complexes

Two novel bis-acylhydrazone where as 1,4-diacetylbenzene bis(4-hydroxy benzoyl hydrazone) H2L1 and 1,4-diacetylbenzene bis(4-nitrobenzoyl hydrazone) H2L2 ligands bearing two hydrazone side groups and their metal(H) complexes have been synthesized and characterized by H-1-NMR13 C-NMR, elemental analysis, FT-IR infrared spectra, magnetic susceptibility measurements and UV-vis electronic absorption spectra. The L1H2,L2H2) ligands were synthesized by reacting 4-hydroxybenzohydrazide and 4-nitrobenzohydrazide with 1,4-diacetylbenzene, respectively. The ligands H2L1, L2H2) react with metal(H) chlorides anhydrous to form polymeric dinuclear metal(II) complexes with general formula [(M-2(L-x)(2)}(n)] with a metal to ligand ratio of 1:1 when [x = 1, 2; M = Ni(II), Co(H), Cu(II), Zn(II) and Cu(II)]. In the complexes, the ligands act as dianionic tetradentate and coordination takes place in the enol tautomeric form with the enolic oxygen and azomethine nitrogen atoms while the phenolic hydroxyl and nitro groups of dihyrazone moiety do not participate in coordination.