Binary and ternary complexes of copper(II) with some dihydroxycoumarins

The complexation behaviour of copper(II) with a series of selected dihydroxycoumarins has been studied. Copper(II) binary complexes with esculetin, daphnetin and their 4-methyl and 4-phenyl derivatives and ternary complexes having a secondary ligand, ammonia or pyridine have bean synthesized. The general composition of binary complexes has bean found to be Cu (H₂O)₂ (HL)₂] and that of ternary complexes as Cu (L) (X)₄] (where X = NH₃ or C₅H₅N). The magnetic studies indicate all the complexes to be monomeric in nature. IR studies show that one of the two phenolic hydroxyl groups present in the ligand is lost during complexation. It is concluded that of the four ligands attached to the copper atom dihydroxycoumarin is bound most firmly.