Synthesis, spectroscopic, and magnetic studies of copper(II) with N-protected amino acids: crystal and molecular structure of diaquatetrakis(µ-N-benzoyl-α-alaninato)-dicopper(II)

Abstract

Eighteen complexes of copper(II) having the general formula CuL₂·nH₂O (n= 1–4) with N-protected amino acids (HL) have been prepared and characterized by spectroscopic methods and magnetic susceptibility measurements. These complexes belong to three types: binuclear species having bridging bidentate co-ordination through the carboxylate group, mononuclear species having symmetrical chelating bidentate co-ordination or bridging bidentate co-ordination with no Cu–Cu interaction, and mononuclear species having highly unsymmetrical chelating bidentate or non-chelating unidentate co-ordination through the carboxylate group. The complex [{Cu(Bz-α-AlaO)₂(H₂O)}₂] crystallizes in the triclinic system with space group P, and unit-ceil parameters a= 9.421 (2), b= 9.549(2), c= 12.618(3)Å,α= 74.31(2), β= 79.21(2), γ= 88.69(2)°, and Z= 1. Full-matrix least-squares refinement using 2 842 independent reflections converged to a final R= 0.038 and R′= 0.052. The complex has a typical copper(II) acetate monohydrate type structure with mean Cu–O(carboxylate), Cu–O(water), and Cu–Cu distances of 1.968(3), 2.138(4), and 2.664(1)Å, respectively.