Dinuclear copper(II) complexes of a macrocyclic compartmental ligand in two isomeric forms. Exogenous ion effect upon ligand isomerism

A dinucleating compartmental ligand derived from the cyclic [2:1:1] condensation of 2,6-diformyl-4-methylphenol, 1,3-propanediamine, and diethylenetriamine (dien) assumes two isomeric forms in the dinuclear copper(II) complexes, [Cu-2(L-a)](ClO4)(2)center dot 2H(2)O (1) and [Cu-2(L-b)(AcO)]BPh4 (2). Complex 1 has the ligand in the usual condensation with a trimethylene chain (-(CH2)(3-)) and a 3-azapentamethylene chain (-(CH2)(2)NH(CH2)(2)-) between two azomethine nitrogen atoms; the nitrogen atom of the 3-azapentamethylene chain is free from coordination. Complex 2 has the ligand in an unusual condensation with dien: The central amino nitrogen of then is further involved in the condensation with one C=N linkage to form an imidazolidine ring. An acetate ion bridges two copper ions to form a mu-acetato-di (mu-phenol ato) dinuclear core with a saddle-like shape. The origin for the unusual condensation in 2 is considered and the physicochemical properties of 1 and 2 are examined.