title: Molecular recognition modes between adenine or adeniniun(1+) ion and binary M(II)(pdc) chelates (MCoZn; pdc=pyridine-2,6-dicarboxylate(2-) ion).
abstract: Mixed ligand M(II)-complexes (MCoZn) with pyridine-2,6-dicarboxylate(2-) chelator (pdc) and adenine (Hade) have been synthesized and studied by X-ray diffraction and other spectral and thermal methods: [Cu(pdc)(H(N9)ade)(H2O)] (1), [Cu2(pdc)2(H2O)2(μ2-N3,N7-H(N9)ade)]·3H2O (2), trans-[M(pdc)(H(N9)ade)(H2O)2]·nH2O for MCo (3-L, 3-M, 3-H) or Zn (4-L, 4-H), where n is 0, 1 or 3 for the 'lowest' (L), 'medium' (M) and 'highest' (H) hydrated forms, and the salt trans-[Ni(pdc)(H2(N1,N9)ade)(H2O)2]Cl·2H2O (5). In all the nine compounds, both neutral and cationic adenine exist as their most stable tautomer and the molecular recognition pattern between the metal-pdc chelates and the adenine or adeninium(1+) ligands involves the MN7 bond in cooperation with an intra-molecular N6H⋯O(coordinated carboxylate) interligand interaction. In addition the dinuclear copper(II) compound (2) has the CuN3 bond and the N9H⋯O(coord. carboxylate) interaction. The structures of mononuclear ternary complexes proved that the molecular recognition pattern is the same irrespective of (a) the coordination geometry of the complex molecule, (b) the different hydrated forms of crystals with Co or Zn, and (c) the neutral of cationic form of the adenine ligand. These features are related to the mer-NO2 chelating ligand conformation (imposed by the planar rigidity of pdc) as a driving force for the observed metal binding mode.
authors.affiliation: Department of Inorganic Chemistry, Faculty of Pharmacy, University of Granada, 18071 Granada, Spain. Electronic address: pbrandi@ugr.es.
authors.forename: María
authors.initials: M
authors.lastname: Del Pilar Brandi-Blanco
authors.forename: Duane
authors.initials: D
authors.lastname: Choquesillo-Lazarte
authors.forename: Alicia
authors.initials: A
authors.lastname: Domínguez-Martín
authors.forename: Antonio
authors.initials: A
authors.lastname: Matilla-Hernández
authors.forename: Josefa María
authors.initials: JM
authors.lastname: González-Pérez
authors.forename: Alfonso
authors.initials: A
authors.lastname: Castiñeiras
authors.forename: Juan
authors.initials: J
authors.lastname: Niclós-Gutiérrez
mesh_terms: D000225:Adenine / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D007477:Ions; D008024:Ligands; D008958:Models, Molecular; D011725:Pyridines / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D002614:Chelating Agents; D056831:Coordination Complexes; D007477:Ions; D008024:Ligands; D011725:Pyridines; D003035:Cobalt; D015032:Zinc; D000225:Adenine
keywords: Adenine; Crystal structure; Mixed-ligand metal complexes; Molecular recognition; Pyridine-2,6-dicarboxylate ligand; Transition metal(II) ions