Formation of supramolecular complex between imidazole and dichloro(5,10,15,20-tetraphenylporphinato)zirconium(IV)

By the reaction of 5,10,15,20-tetraphenyl-21H,23H-porphin (H₂TPP) with zirconium tetrachloride in boiling benzonitrile a complex was obtained, dichloro(5,10,15,20-tetraphenylporphinato)zirconium(IV), (Cl)₂ZrTPP. The equilibrium and reaction rate of stepwise reactions of (Cl)₂ZrTPP with imidazole (Im) in toluene were investigated by spectrophotometry. It was established that the three steps of the complex formation include reversible processes of coordination of Im molecule and substitution of 2Cl⁻ by the second and third Im molecules. The products of the first and second stages of the reaction, (Cl)₂(Im)ZrTPP and (Cl)(Im)₂ZrTPP]⁺Cl⁻, respectively, are unstable and dissociate slowly at one Zr-Cl bond. By the analysis of the numerical values of the reactions parameters with accounting for the existence of definite spectral response to the presence of an organic base was shown a better prospect of application of (Cl)₂ZrTPP in sensor systems than those of metallophtalocyianines and doubly charged cation complexes with porphyrins.