Zinc-ligand interactions solvent

The metalloporphyrins as macrocyclic compounds have a few sites for specific and universal solvation and are able to axial coordination of some ligands. At the present time chemical modification of macrocycle is a main way of increasing of selectivity of molecular complex formation. The data obtained earlier [1,2] show that the selectivity may be increased due to specific %-% interactions of the metalloporphyrins with aromatic molecules. Aromatic molecules coplanar to the macrocycle will rise geometrical requirements to axial coordinating ligands. In particular, the results of the thermodynamic study of the axial coordination of n-propylamine by zinc(II) porphyrins in benzene have demonstrated the formation of the complexes of the metalloporphyrin containing both w-propylamine and benzene [2], The aim of this work is to study the molecular complexes of zinc (II) porphyrins prepared by slow crystallization from saturated solutions in benzene, w-propylamine and mixed solvent benzene - -propylamine. 

Intermetallic distances are in the range of 3.63 - 3.69 A. The nickel and copper complexes have square planar coordination as can be expected for salen and salophen type tetradentate ligands [ref 10]. In the case of zinc a square pyrimidal coordination was found with the salophen unit forming the ground-plane and a DMF molecule at the apical position. The hard cation interacts with all oxygens of the polyether cavity and the coordination sphere is completed by counter anions and/or solvent molecules. In an analogous way the dinuclear complexes 7 with two (alkylated) oxime bonds were synthesized in 55-82% yield [ref 11]. 

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