New Mononuclear Cobalt(Iii) And Manganese(Iii) Complexes Containing A Hexadentate Schiff Base Ligand

Two new mononuclear complexes [MnL](ClO4) (1) and [CoL](NO3)center dot 2CH(3)OH (2) containing N,N'-bis[(2-hydroxybenzilideneamino)propyl]-piperazine (H2L) have been synthesized and structurally characterized. Complex 1 crystallizes in the monoclinic space group P2(1)/c, with cell dimensions a = 11.5180(6), b = 15.7885(8), c = 13.2207(7) angstrom,beta = 90.162(4)degrees, complex 2 in the trigonal space group, with cell dimensions a = 17.4723(3), b = 17.4723(3), c = 47.655(1) angstrom, gamma = 120 degrees. X-ray structure determinations of 1 and 2 revealed that both compounds consist of mononuclear complex cations containing trivalent metal centers, Mn-III or Co-III. The metal ions are coordinated in a distorted octahedral fashion by the N-4 donor set of the ligand in basal and the two phenoxo oxygen atoms in apical positions. Spectral properties are consistent with the crystallographic results. The electrochemical properties of the complexes have been investigated by cyclic voltammetry. The reversible behavior of the Mn system was slightly affected by the changes in the coordination environment during the overall redox process, while the Co-III/Co-III system exhibited an irreversible behavior.