Structures of bis(5,5-diphenylhydantoinato)copper(II) complexes with primary amines involving square pyramidal CuN4O chromophores

Copper(II) complexes [CuL2(i-PrNH2)(2) . H2O] (la), [CuL2(i-PrNH2)(2)] (Ib), [CuL2(EtNH2)(2) . H2O] (2a), [CuL2(EtNH2)(2)]. CHCl3 (2b), [CuL2(EtNH2)(2) . H2O]. 2CHCl(3) (2c), and [CuL2(EtNH2)(2) . MeOH] (2d) (L=5,5-diphenylhydantoinate) have been prepared. The crystal structures of la, 2c, and 2d were determined by X-ray analysis. Each CuN4O chromophore is a five-coordinated square-based pyramidal geometry. The axial Cu-O distances are Cu(1)-O(I)(water)=2.362(10) Angstrom, Cu(1)-O(1)(water)=2.436(9) Angstrom, and Cu(1)-O(1)(MeOH)=2.33(1) Angstrom, for complexes la, 2c, and 2d, respectively. Intramolecular hydrogen bonds are formed between the carbonyl oxygens and amino hydrogens (C=O ... H-N) as well as the axial ligand (C=O ... H-O). The latter hydrogen bonds stabilize the axial ligand for coordination. Moreover, double intermorecular hydrogen bonds link the 5,5-diphenylhydantoinate ligands (C=O ... H-N) belonging to be adjacent complex molecules in all three complexes. The electronic spectra of the complexes in the solid state and in chloroform solutions were determined at room temperature, and a considerable change in ligand field bands was observed. The five-coordinated complexes in the chloroform solutions release their axial water ligand and the CuN4O chromophore converts into a distorted tetrahedral CuN4 chromophore.