Synthesis, spectral, magnetic and electrochemical properties of new binuclear unsymmetrical aminoacid ligands and their Cu(II) complexes with bridging and non bridging motifs
The synthesis, spectral, magnetic and electrochemical properties of a series of binuclear Cu(II) complexes of new unsymmetrical binucleating ligands (H2L1, H2L2) are described where H2L1=4-methyl-2-[N-methyl piperazin-1-yl) methyl]-6-[(prolin-1-yl)-methyl] phenol and H2L2=4-bromo-2-[N-methyl piperazin-1-yl)methyl]-6-[(prolin-1-yl)]-methyl] phenol. The exogenous ligands were incorporated into the complexes: hydroxo [Cu2 L(OH)(H2O)2] ClO4·H2O (L1=1a, L2=1b), acetato, [Cu2L(OAc)2]·H2O (L1=2a, L2=2b), nitrito, [Cu2(L(NO2)2(H2O)2] (L1=3a, L2=3b), azido, [CuL(N3)2]·3H2O (L1=4a, L2=4b). Complexes 1a, 1b and 2a, 2b contain bridging exogenous groups, while 3a, 3b and 4a, 4b possess only openμ-phenolato structures. Both, the ligands and complexes were characterised by spectral studies. The magnetic susceptibility of the complexes have been measured in the temperature range (77–300K) and the exchange coupling parameter (2J) was determined from least square fitting of the data. The strength of the antiferromagnetic interaction is in the order NO2=N3>OAc>OH. The redox behaviour of these complexes in acetonitrile reveal highly quasi reversible behaviour due to chemical or/ and stereochemical changes subsequent to electron transfer. The first reduction potential is sensitive to electronic effects of the substituents at the aromatic ring of the ligand system, shifting to positive potentials when the substituents are replaced by more electrophilic groups.
Volume 134, 2022
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