Synthesis, crystal structure, redox property and theoretical studies of a pyrrole containing cobalt(III) Schiff base compound
A new mononuclear cobalt(III) complex with a pentadentate Schiff base ligand derived from the condensation of N-(3-aminopropyl)-propane-1,3-diamine with pyrrole-2-aldehyde has been synthesized and structurally characterized by X-ray crystallography. Structural analysis shows that the geometry of cobalt(III) ion is a distorted octahedron in which triamine part of the pentadentate ligand occupies the meridional positions, while two pyrrole nitrogen atoms are in cis disposition. Despite the potentially interesting similarities of pyrrole-based ligands to porphyrin systems, the present complex is inactive towards the oxidation of o-aminophenol, while analogous systems with pyridine containing ligands have proven to be efficient functional models for phenoxazinone synthase. Although the electrospray ionization mass spectral study clearly indicates the formation of a complex-substrate aggregate, the inability towards oxidation of o-aminophenol by the present complex can be explained electrochemically, where strong electron donating ability of the deprotonated pyrrole moiety reduces the possibility of reduction of cobalt(III) to cobalt(II).
Coordination chemistry, Schiff bases, Pyrrole ligands, Cobalt, X-ray crystal structures, Density functional calculations, Cyclic voltammetry, Mass spectroscopy
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