Nuria Fernández-Hermida

From copper(II) carboxylate to copper(II) 4-pyridylsulfonate coordination polymers as a consequence of the copper(II)-assisted oxidative cleavage of the 4,4′-dipyridyldisulfide ligand

Five coordination polymers 1 {[Cu4(HCO2)6(OH)2(4dpds)2]·2CH2Cl2}n, 2 {[Cu4(CH3CO2)6(OH)2(4dpds)2]}n, 3 {[Cu(4dpds)2(H2O)2](4pySO3)2·2H2O}n, 4 {[Cu(4pySO3)2(4dpds)2]·2H2O}n and 5 {[Cu(4pySO3)2(dmso)2]·2H2O}n (where 4dpds = 4,4′-dipyridyldisulfide, 4pySO3 = 4-pyridylsulfonate) have been obtained during a study into the reactivity of basic copper(II) salts (formate and acetate) with 4,4′-dipyridyldisulfide (4dpds). The coordination polymers 1 and 2 consist of a repeated rhomboid structure in which analogous Cu4(RCO2)6(OH)2 cores are joined by two 4,4′-dipyridyldisulfide bridging ligands to generate two different chain topologies: planar ribbon in 1 and ruffled ribbon in 2. 4-Pyridylsulfonate ions appear as ligands or counterions in the coordination polymers 3, 4 and 5 due to oxidative cleavage of the 4,4′-dipyridyldisulfide under mild conditions. The coordination polymer 3 has been isolated repeatedly in several direct reactions of the copper(II) carboxylates with 4,4′-dipyridyldisulfide. However, the coordination polymers 4 and 5 have been obtained from 1 and 2, respectively, by recrystallization from DMF and DMSO. In compound 4, as in 3, the 4,4′-dipyridyldisulfide has only been partially oxidized to 4-pyridylsulfonate and a proportion of these units remain in the structure as disulfide. However, in 5 the oxidation is complete. The structural analysis of these coordination polymers reveals that, in all cases, weak interactions such as classical and non-classical hydrogen bonds, as well as CH⋯π, S⋯π and S⋯O interactions, join the polymeric chains to generate three-dimensional networks.

Metallosupramolecular compounds based on Cu(II)/oxalate/twisted NSSN ligands showing a new in situ S–C bond cleavage

Four new complexes, [Cu2(C2O4)2(SCS)]·3H2O (1), [Cu2(C2O4)3(SCSH)2]·H2O (2), [Cu(C2O4)(SS)2]·3H2O (3) and [Cu(C2O4)(SS)]·6H2O (4) [where SCS = bis(4-pyridylthio)methane and SS = 4,4′-dipyridyldisulfide], have been synthesized by the reaction of the SS and SCS ligands with the corresponding copper(II) oxalate salt. The different synthetic conditions allowed control of the preparation of a 3D open metal–organic framework in 1, a dinuclear zwitterionic molecular compound in 2 and one- and two-dimensional (1D and 2D) coordination polymers in 3 and 4, respectively. Compound 4 was also obtained by in situ transformation of the dithioether ligand (SCS) to the disulfide ligand (SS) under hydrothermal conditions at 150 °C. The topology of the structures has been studied and 1 is a new 3D MOF with a binodal 4-connected node in a scarcely known network topology. Different numbers and topologies of water molecules are hosted in the crystal lattices of the compounds. The integrity of the frameworks after dehydration has been validated and discussed. The magnetic properties of compounds 1, 2 and 4 have also been investigated. Strong antiferromagnetic behaviour was found in 1 and weak antiferromagnetic coupling was observed in 2 and 4. The magneto-structural correlations that govern these interactions are discussed in detail.

Mononuclear discrete complexes and coordination polymers based on metal(II) chelidonate complexes with aromatic N,N-chelating ligands†

The versatile coordination chemistry of the anion chelidonate (chelidonic acid, H2chel, 4-oxo-4H-pyran-2,6-dicarboxylic acid) allowed for the synthesis of different mixed-ligand complexes with the N,N′-chelating ligands 2,2′-bipyridine and 1,10-phenanthroline. We describe here the synthesis and structural characterization of a series of compounds that illustrate the structural diversity of which 4-oxo-4H-pyran-2,6-dicarboxylate ligands are capable: the 2D coordination polymer [Cu(chel)(bipy)] (1), the 1D coordination polymer [Zn(chel)(bipy)(OH2)]·1/2H2O (2), the discrete neutral mononuclear compounds [Zn(chel)(phen)(OH2)2] (3) and [M(chel)(phen)(OH2)3]·nH2O, M = Zn and n = 1 (4), M = Ni and n = 2 (5), and the discrete mononuclear cationic complex [Zn(OH2)2(phen)2]chel·3.3H2O (6). The effects of the weak interactions on the crystal packing were also analyzed. The thermal behaviour of the hydrated compounds was investigated. The study of the magnetic properties of 1 revealed weak antiferromagnetic coupling between the copper(II) centres.