Molecular recognition modes between adenine or adeniniun(1+) ion and binary MII(pdc) chelates (MCoZn; pdc=pyridine-2,6-dicarboxylate(2-) ion)

The Copper(II)-Thiodiacetate (tda) Chelate as Efficient Receptor of N9-(2-Hydroxyethyl)Adenine (9heade): Synthesis, Molecular and Crystal Structures, Physical Properties and DFT Calculations of [Cu(tda)(9heade)(H2O)]·2H2O

Considering that Cu(tda) chelate (tda: dithioacetate) is a receptor for adenine and related 6-aminopurines, this study reports on the synthesis, molecular and crystal structures, thermal stability, spectral properties and DFT calculations related to [Cu(tda)(9heade)(H2O)]·2H2O (1) [9heade: N9-(2-hydroxyethyl)adenine]. Concerning the molecular recognition of (metal chelate)-(adenine synthetic nucleoside), 1 represents an unprecedented metal binding pattern (MBP) for 9heade. However, unprecedentedly, the Cu(tda)-9heade molecular recognition in 1 is essentially featured in the Cu-N1(9heade) bond, without any N6-H⋯O(carboxyl tda) interligand interaction. Nevertheless, N1 being the most basic donor for N9-substituted adenines, this Cu-N1 bond is now assisted by an O2-water-mediated interaction (N6-H⋯O2 and O2⋯Cu weak contact). Also, in the crystal packing, the O-H(ol) of 9heade interacts with its own adenine moiety as a result of an O3-water-mediated interaction (O(ol)-H⋯O3 plus O3-H36⋯π(adenine moiety)). Both water-mediated interactions seem to be responsible for serious alterations in the physical properties of crystalline or grounded samples. Density functional theory calculations were used to evaluate the interactions energetically. Moreover, the quantum theory of atoms-in-molecules (QTAIM), in combination with the noncovalent interaction plot (NCIPlot), was used to analyze the interactions and rationalize the existence and relative importance of hydrogen bonding, chalcogen bonding and π-stacking interactions. The novelty of this work resides in the discovery of a novel binding mode for N9-(2-hydroxyethyl)adenine. Moreover, the investigation of the important role of water in the solid state of 1 is also relevant, along with the chalcogen bonding interactions demonstrated by the density functional theory (DFT) study.

Molecular and supramolecular recognition patterns in ternary copper(II) or zinc(II) complexes with selected rigid-planar chelators and a synthetic adenine-nucleoside

Four ternary metal-complexes with Cu(II) or Zn(II), 2,6-pyridine-dicarboxylate (pdc) or glycyl-glycinate (GG) and the synthetic nucleoside 9-(2-hydroxyethyl)adenine (9heade) have been synthesized and studied by single-crystal X-ray diffraction and other physical methods. Relevant supramolecular assemblies found in the solid state structures have been further studied using density functional theory (DFT) calculations. In addition, the energetic features of the non-covalent interactions as well as the cooperativity effects have been calculated and characterized using the non-covalent interaction plot computational tool. Compounds trans-[Cu(pdc)(9heade)(H₂O)₂]·3H₂O (1a) and [Cu(pdc)(9heade)(H₂O)]·H₂O (1b), trans-[Zn(pdc)(9heade)(H₂O)₂] (2), share the same molecular recognition pattern consisting in the cooperation of the metal-N7(9heade) bond and an interligand (9heade)N6-H···O(pdc) interaction, regardless of the nature of the metal, the coordination environment and the water content. At a supramolecular level, these compounds exhibit pairs of complex molecules linked by H-bonds and interesting anion-π/π-π/π-anion assemblies (in 1a and 1b) or the unprecedented π-π interactions (in 2), involving the purine moieties or the exocyclic -⁶NH₂ purine groups, respectively. Compound 3, {[Cu(GG)(9heade)(H₂O)·Cu(GG)(μ₂-9heade)]·8H₂O}_n, consists in asymmetric dinuclear complex units (Cu···Cu 7.83 Å) that connect with adjacent ones by pairs of very weak Cu-O(carboxylate) bonds (Cu···Cu 3.81 Å) building a polymeric chain. The supramolecular transition from a single molecule to dinuclear units and finally a polymeric chain is also observed in the electron paramagnetic resonance spectra and discussed from a structural point of view as well as by DFT calculations. The unprecedented N7 and μ-N7,O(ol) metal binding patterns of 9heade differs from that recently reported (μ-N1,N7) in a Cd(II) polymer.

Constructing two 1D coordination polymers and one mononuclear complex by pyrazine- and pyridinedicarboxylic acids under mild and sonochemical conditions: magnetic and CSD studies

Two 1D coordination polymers and one mononuclear complex were synthesized. Nanostructures of the CPs were prepared by a sonochemical method.

Molecular recognition between adenine or 2,6-diaminopurine and copper(II) chelates with N,O2,S-tripodal tetradentate chelators having thioether or disulfide donor groups

Five novel ternary copper(II) complexes with the N,O2,S-tripodal tetradentate chelators N,N-bis(carboxymethyl)-S-benzylcysteaminate(2-) ion (BCBC) or N,N,N',N'-tetrakis(carboxymethyl)cystaminate(4-) ion (TCC) and adenine (Hade), 2,6-diaminopurine (Hdap), 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) as co-ligand were synthesized and characterized by X-ray diffraction and other physical methods: [Cu2(BCBC)2(μ2-N3,N7-H(N9)ade)(H2O)2]·H2O (1), [Cu2(BCBC)2(μ2-N7,N9-H(N3)dap)(H2O)2]·4H2O (2), [Cu2(μ2-TCC)(H(N9)ade)2(H2O)2]·10H2O (3), [Cu2(μ2-TCC)(bpy)2]·15H2O (4) and [Cu2(μ2-TCC)(phen)2]·14H2O (5). The crystal structure of H4TCC·3H2O was also determined. All ternary Cu(II) complexes have molecular structures. The N-(2-mercaptoethyl)-iminodiacetate moieties of BCBC or TCC ligands play a NO2+S-tripodal tetradentate role, with the S-(thioether or disulfide) atom as the apical/distal donor of the copper(II) center. In 1-3, the iminodiacetate moiety exhibits a mer-NO2 conformation (two nearly coplanar chelate rings) while in 4 and 5 (with bpy or phen as coligand) it displays a fac-NO+O (apical/distal) conformation. We conclude that the formation of the Cu-S(thioether or disulfide) bonds is strongly favored by the N-branched topology of the S-ligands in the reported compounds.