Synthesis of copper(II) and nickel(II) complexes using compartmental ligands: X-ray, electrochemical and magnetic studies

Abstract

Acyclic dicompartmental ligands suitable for the complexation of transition-metal ions which can form mononuclear, homo- or heterodinuclear complexes have been synthesised. The mononuclear complexes ML 1 (M=Cu, Ni) where L 1= N, N′-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-methylbenzyl]alkyldiimine (alkyl=ethylene, L 1a; propylene, L 1b; butylene, L 1c; triethylenetetraamine, L 1d); ML 2 (M=Cu, Ni) where L 2= N, N′-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-methylbenzyl]alkyldiamine (alkyl=ethylene, L 2a; propylene, L 2b); and ML 3 (M=Cu, Ni) where L 3= N, N′-bis[2-hydroxy-3-(morpholino-1-ylmethyl)-5-bromobenzyl]alkyldiimine (alkyl=ethylene, L 3a; propylene, L 3b; butylene, L 3c) have been synthesised and characterised by C, H, N analysis, IR, electronic and ESR spectra. The complexes CuH 2L 1a ( 1), CuH 2L 2a ( 4), NiH 2L 1a ( 9) and NiH 2L 1d ( 12) have been analysed by X-ray crystallography. Complexes 1 and 4 have square pyramidal geometry. The coordination geometry around the metal ion in complex 9 is square planar and in complex 12 it is octahedral. Electrochemical studies of the complexes show a single quasi-reversible electron transfer process at the negative potential region. For copper complexes ( 1– 8) E pc=−1.10 to −0.70 V, for nickel complexes ( 9–12) E pc=−1.0 to −0.85 V. Copper complexes show a magnetic moment value of μ eff=1.70–1.75 BM. The square planar nickel complexes are diamagnetic whereas the nickel complex ( 12) with octahedral structure has a magnetic moment value of 3.12 BM.