title: Dipeptides containing the alpha-aminoisobutyric residue (Aib) as ligands: preparation, spectroscopic studies and crystal structures of copper(II) complexes with H-Aib-X-OH (X=Gly, L-Leu, L-Phe).
abstract: Synthetic procedures are described that allow access to new copper(II) complexes with dipeptides containing the alpha-aminoisobutyric residue (Aib) as ligands. The solid complexes [Cu(H(-1)L(A))](n).nH(2)O (1) (L(A)H=H-Aib-Gly-OH), [Cu(H(-1)L(B))(MeOH)](n).nMeOH (2) (L(B)H=H-Aib-L-Leu-OH) and [Cu(H(-1)L(C))](n) (3) (L(C)H=H-Aib-L-Phe-OH) have been isolated and characterized by single-crystal X-ray crystallography, solid-state IR spectra and UV-Vis spectroscopy in solution (H(-1)L(2-) is the dianionic form of the corresponding dipeptide). Complexes 1 and 3 are three-dimensional coordination polymers with similar structures. The doubly deprotonated dipeptide behaves as a N(amino), N(peptide), O(carboxylate), O'(carboxylate), O(peptide) mu(3) ligand and binds to one Cu(II) atom at its amino and peptide nitrogens and at one carboxylate oxygen, to a second metal at the other carboxylate oxygen, while a third Cu(II) atom is attached to the peptide oxygen. The geometry around copper(II) is distorted square pyramidal with the peptide oxygen at the apex of the pyramid. The structure of 2 consists of zigzag polymeric chains, where the doubly deprotonated dipeptide behaves as a N(amino), N(peptide), O(carboxylate), O'(carboxylate) mu(2) ligand. The geometry at copper(II) is square pyramidal with the methanol oxygen at the apex. The IR data are discussed in terms of the nature of bonding and known structures. The UV-Vis spectra show that the solid-state structures of 1, 2 and 3 do not persist in H(2)O.
authors.affiliation: Department of Pharmacy, University of Patras, GR 265 04 Patras, Greece.
authors.forename: Manolis
authors.initials: M
authors.lastname: Tiliakos
authors.forename: Eugenia
authors.initials: E
authors.lastname: Katsoulakou
authors.forename: Vassilios
authors.initials: V
authors.lastname: Nastopoulos
authors.forename: Aris
authors.initials: A
authors.lastname: Terzis
authors.forename: Catherine
authors.initials: C
authors.lastname: Raptopoulou
authors.forename: Paul
authors.initials: P
authors.lastname: Cordopatis
authors.forename: Evy
authors.initials: E
authors.lastname: Manessi-Zoupa
mesh_terms: D000621:Aminoisobutyric Acids / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004151:Dipeptides / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D013055:Spectrophotometry, Infrared
chemical_list: D000621:Aminoisobutyric Acids; D004151:Dipeptides; D008024:Ligands; D009942:Organometallic Compounds; D003300:Copper