Axial Coordination Reaction Research Articles

Kinetic studies on axial coordination reactions of para-substituted tetraphenylporphinatoiron(III) chlorides

A series of para-substituted tetraphenylporphinatoiron(III) chlorides [( p-X)TPPFeCl] (XCl, H, CH 3, OCH 3) have been synthesized. Kinetic studies are reported for the reactions of ( p-X)TPPFeCl+ nL→ ( p-X)TPPFeL n]+Cl − (L=imidazole, 2-methylimidazole and 2-ethyl-4-methyl-imidazole) in acetone at several temperatures. The reaction rates are second order dependent on Im and MeIm with n=2, but first order on EMIm with n=1; the reaction rates increase with temperature in both cases. The mechanisms of reactions for various ligands have been proposed. The effects of various ligands and para-substituents on the phenyl rings for these reactions have been investigated.

Thermodynamics of axial coordination reaction of para-substituted tetraphenylporphinatoiron(III) chloride

The thermodynamics of axial coordination reactions of para-substituted tetraphenylporphinatoiron(III) chloride, ( p-X)TPPFeCl, with various ligands (L = Im (imidazole), MeIm (2-methylimidazole), EMIm (2-ethyl-4-methylimidazole) in dichloromethane solvent have been studied. ▪ The steric and electronic effects of the three axial ligands are compared, and the effect of para-substituents on the phenyl rings is also discussed. Some linear relationships can be derived theoretically if Hammett relationships, isokinetic and isoequilibrium relationships show up in the system of similar reactions. These linear relationships have been verified by our experiments.

Electron Transfer and Axial Coordination Reactions of Cobalt Tetra(Aminophenyl)Porphyrins Covalently Bonded to Carbon Electrodes

Electrochemistry of tetra(aminophenyl)porphyrin covalently attached to glassy carbon and then cobalt‐metallated, was investigated in DMSO and solvents in the presence of pyridine. Shifts in formal potential were used to measure complex stability constants and coordination number for the pyridine complexes of the immobilized metalloporphyrin. Unusually slow electrochemistry of the Co(III/II) reaction was also studied by cyclic voltammetry and by reflectance spectroelectrochemistry. It is proposed that coordination of cobalt by surface carboxylate groups causes extraordinarily slow electron transfer for the Co (III/II) step.