Exogenous bridging and nonbridging in Cu(II) complexes of Mannich base ligands: Synthesis and physical properties

Preparation of pentadentate ligands L-1, L-2, L-3 and L-4, where L-1 4-chlo ro-3-methyl-2[(prolin-1-yl)methyl]-6-[N-phenyl piperazin-1-yl)methyl]phenol , L-2 = 4-ethyl-2-[(prolin-1-yl)methyl]-6-[(N-phenyl piperazin-1-yl)methyl] phenol, L-3 = 4-chloro-3-methyl-2-[(prolin-1-yl)methyl]-6-[N-methyl piperaz in-1-yl]methyl phenol, L-4 = 4-methoxy-2-[(prolin-1-yl)methyl]-6-[(N-phenyl piperazin-1-yl)methyl]phenol is described together with that of the corres ponding Cu(II) complexes with various bridging motifs like OH, OAc and NO2. The complexes are characterized by elemental analysis, electrochemical and electron paramagnetic spectral studies. Redox properties of the complexes in acetonitrile are highly quasireversible due to the chemical or/and stere ochemical changes subsequent to electron transfer. The complexes show resol ved copper hyperfine EPR at room temperature, indicating the presence of we ak antiferromagnetic coupling between the copper atoms. Strengths of the an tiferromagnetic interactions are in the order NO2 > OAc > OH.