Redox and spectroscopic properties of heterobinuclear complexes of cobalt(III) Schiff bases and chloronitrosyl molybdenum fragments

Abstract

A series of new heterobinuclear complexes obtained by the reaction of [Mo(NO){HB(dmpz)3 } Cl2 ]; [HB(dmpz)3 = tris(3,5-dimethylpyrazolyl)borate] with Cobalt(III) Schi -base complexes derived by condensation of 1mol equiv. of 2,4-dihydroxylbenzaldehyde and salicylaldehyde with Į,Ȧ-diamines [NH2 (CH2 ) nNH2 ,n = 2-4, 1,2-C6H4 (NH2 ) 2 ] were synthesized. !e complexes were studied by electrochemistry and UV/VIS/NIR spectroelectrochemistry in DCM and MeCN to evaluate how the Schi base donors a ect the properties of the complexes. !e coordination of the Schi base appeared to occur through the two azomethine nitrogens and the two o-OH groups, while the molybdenum complex coordinated through the terminal m-OH of the Schi bases. From cyclic and di erential pulse voltammetric data it was shown that the E1/2 values for monometallic Co(III)/(II) redox couple shifted to less cathodic values as the ethylene backbone increased. !e corresponding bimetallic complexes had two reduction waves associated with the cobalt(III)/(II) and Mo (NO) (III)/ (II) redox couples. A comparison of the reduction peak potentials of these complexes in DCM and MeCN solvents revealed that the potentials in dichloromethane DCM are more cathodic than in MeCN suggesting that the type of solvent used has a signi"cant e ect on the electron distribution of the two metal centres.