Spectral and electro-chemical characterization of transition metal complexes of a modified [N6] macrocycle. A mimic to cyclic hexapeptide

Abstract

The 16-membered modified [N 6 ] macrocylic ligand (L), a mimic to cyclic, hexapeptide is reacted with MCl 2 and MCl 3 resulting in complexes with stoichiometrices [MLCl 2 ] (M = Cr, Mn, Co, Ni, Cu), [MLCl 3 ] (M = Pt, Pd) and [MLCl 2 ]Cl (M = Fe, Ru). Its reactions with the precursors [M(Ph 3 P) 2 Cl 2 ] (M = Co, Ni, Pt, Pd) follow a ligand displacement path affording the final products which do not contain coordinated Ph 3 P. Complexes have been characterized from results of elemental analyses, conductometric, magnetic susceptibility, i.r. and u.v.-vis (ligand field) spectral studies. Magnetic susceptibility and ligand field spectral data are consistent with a hexacoordinate geometry for Cr 2+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ and Cu 2+ and four coordinate square-planar geometry for Pt 2+ and Pd 2+ . Molecular orbital computations using CSChem ultra MOPAC software for an optimized minimum energy plot of the structure shows that the ligand binds metal ions as a tetradentate (N,N,N,N) chelating agent. Cyclic voltammetric studies indicate formation of stable reversible or quasi-reversible redox couples in solutions, which corroborates a kinetic stability of these complexes in their variable oxidation states.

Spectral, thermal and electrochemical characterization of novel homo-dinuclear complexes [M2(H3DTPA)(H2O)6]Cl2·xH2O (M=Cr2+, Mn2+, Co2+, Ni2+ or Cu2+)

“…However, the homo-dinuclear complexes (2-4) could not provide a well-defined cyclic voltammogram at all the three scan rates, probably due to a fast electrochemical disproportionation [32] of the species formed in the solution.…”

Synthesis and Electrochemical Studies of Hexamethyldibenzotetraaza N4-Macrocyclic Complexes of Ni(II) and Cu(II) Metal ions

“…Electrochemical studies have been carried out by cyclic voltammetry. The formation of reversible and quasi-irreversible redox couple is responsible for kinetic stability of redox couple [12,13].…”