Showing papers by "Blanca R. Manzano published in 2015"

Robust 2D Coordination Networks from a Two-Step Assembly Process with Predesigned Silver Cyclic Dimers and Hexamethylenetetramine

Abstract: A two-step self-assembly methodology has been used to obtain 2D coordination polymers with an egg-crate structure of trigonal symmetry and space group R3m. The polymers have the molecular formula [Ag3(L1)3(hmt)]X3 (L1 = bis(pyrazol-1-yl)(pyridin-4-yl)methane; hmt = hexamethylenetetramine; X = BF4, ClO4, PF6). In the first step, the previously reported box-like cyclic dimers [Ag L1]2X2, in which the ligands L1 are in a head-to-tail disposition, were obtained and these were subsequently reacted with the base hexamethylenetetramine to form Ag–N(hmt) bonds. The dimers act as linear connectors and the bases as triconnected nodes to give slightly undulating hexagons that form honeycomb sheets. The sheets follow an ABCABC stacking arrangement along [001] so that between them two types of large cavities arise which are occupied by disordered solvent, e.g., DMF inherited from synthesis. The anions, which participate in the formation of the cavities, interact with the sheets through hydrogen bonds. The polymers ca...

One- and Two-Step Self-Assembly Processes in Zn(II) Supramolecular Frameworks with Ditopic Bis(pyrazolyl)methane Ligands. Chiral Recognition and Formation of Cyclic Helicates

Abstract: The new ligands bis(pyrazol-1-yl)(pyridine-3-yl)methane (bpzm3py, 1) and bis(3,5-dimethylpyrazol-1-yl)(pyridine-3-yl)methane (bpz*m3py, 2) have been synthesized. Box-like cyclic dimers have been obtained by reaction of the ligands with Zn(NO3)2, namely, [Zn(NO3)2L]2 (L = 1, complex 3; L = 2, complex 4), after the self-assembly of two metal centers and two ligands in a head-to-tail fashion. In 3 and 4 the pyridine rings exhibit planar chirality and the two pR,pR and pS,pS enantiomers coexist in the crystal. A two-step self-assembly process using 3 as an SBU and sodium 1,4-benzenedicarboxylate (Na2BDC) as a linker leads to the formation of hexanuclear cyclic helicates with a distorted trigonal prism form [Zn2(BDC)(1)2(H2O)4]3(BDC)3 (5) constituted by cyclic dimers and μ2,κ2-BDC connectors that are oriented diagonally. The chiral recognition that is observed means that the three dimers of the helicate have the same chirality. In the 3-D structure, chains of helicates of the same chirality are formed and thes...

Formation of Mono-, Di- and Trinuclear Species in the Self-Assembly of Bis(pyraz­olyl)(pyridin-3-yl)methane Ligands and ­Metals with Different Coordination Geometries

Abstract: The self-assembly of ligands bis(pyrazol-1-yl)(pyridin-3-yl)methane (bpzm3py, L1) and bis(3,5-dimethylpyrazol-1-yl)(pyridin-3-yl)methane (bpz*m3py, L2), with metals of different geometries has been investigated. The use of [PdCl2(PhCN)2] led to the formation of trinuclear species of the type [PdCl2(μ-L)PdCl2(μ-L)PdCl2] with two types of palladium centre. The use of Ni(NO3)2 led to the formation of cyclic dimers [Ni(μ-L)(NO3)2]2, in which the ligands L adopt a head-to-tail disposition, whereas the reaction with CoCl2 led to mononuclear species [CoCl2(L)] with an uncoordinated pyridine ring. The reaction with silver salts gave, in all cases, cyclic dimers with tetracoordinate metal ions. In the cases of AgClO4 and AgCF3SO3, the products were [Ag(μ-L)(X)]2 with the anions coordinated to the metal ions. In the case of AgBF4, the anion remained uncoordinated and the resulting species, [Ag(μ-L)(S)2]2(BF4)2, contained coordinated crystallisation solvents (S = MeOH, acetone). The asymmetry in the ligands created by the 3-substituent in the pyridine ring led to the generation of chirality in the case of the nickel and silver cyclic dimers. The supramolecular structures were analysed and a comparison was made with the structures of complexes that contain the related ligands bis(pyrazol-1-yl)(pyridin-4-yl)methane and bis(3,5-dimethylpyrazol-1-yl)(pyridin-4-yl)methane. A “pyrazolyl embrace” was observed in a silver complex with the non-methylated ligand L1.