(N-benzoyl-DL-alaninate)copper(II) complexes: effect of amines on the amino-acid co-ordination

Abstract

Reaction of amines with the complex [Cu(Bz-AlaO)₂]·H₂O (Bz-AlaO =N-benzoyl-DL-alaninato) gives adducts of the type [Cu(Bz-AlaO)₂]·B_n[n= 1,B = piperazine(ppz), 3-methylpyridine(3Me-py), 4Me-py, 2,2′-bipyridine (2,2′-bipy), 4,4′-bipy, and 1.10-phenanthroline (phen); n= 2, B = Meppz, piperidine (pip), morpholine (morp), py, and 4Me-py] and [Cu(en)₂(Bz-AlaO)₂]. Each complex has been characterized by elemental analysis, solid and solution spectroscopy, and magnetic moment. The complexes may be divided into three types from the point of view of their stereochemistry. Type (1) contains complexes having a copper(II) acetate monohydrate type co-ordination such as [{Cu(Bz-AlaO)₂B}₂][B = H₂O, 3Me-py, 4Me-py, and py (only in solution)], type (2) contains complexes having a square-planar or strongly distorted tetragonal environment with a CuN₂O₂ chromophore such as [Cu(Bz-AlaO)₂]·B_n(B = Meppz, pip, py, 4Me-py, 2,2′-bipy, and 4,4′-bipy) or a CuN₄ chromophore such as [Cu(en)₂(Bz-AlaO)₂](the solution complexes of the Meppz, pip, mor, and 4Me-py adducts, which show a concentration-dependent colour change, are also discussed), and type (3) contains medium tetragonally distorted complexes, as the presence of two d–d bands supports, in the solid [Cu(mor)₂(Bz-AlaO)₂], solid and solution [Cu(Bz-AlaO)₂]·phen, and in the presence of excess of amine, [CuB₂(Bz-α-AlaO)₂](B = Meppz, pip, mor, 3-Me-py, and 4-Me-py). For the phen adduct a cis-octahedral co-ordination with a CuN₂O₄ chromophore is proposed. while for the solution complexes in the presence of an excess of amine the CuN₄O₂ chromophore is suggested.