A polymeric cobalt(II) complex derived from citric acid (H₄cit) and 2,6-diaminopurine (dap): {[Co₄(cit)₂(dap)₄(H₂O)₄]·6.35H₂O}_n

Abstract

Poly[[tetraaquadi-μ4-citrato-tetrakis(2,6-diaminopurine)tetracobalt(II)] 6.35-hydrate], {[Co4(C6H4O7)2(C5H6N6)4(H2O)4]·6.35H2O}n, presents three different types of Co(II) cations in the asymmetric unit, two of them lying on symmetry elements (one on an inversion centre and the other on a twofold axis). The main fragment is further composed of one fully deprotonated citrate (cit) tetraanion, two 2,6-diaminopurine (dap) molecules and two aqua ligands. The structure is completed by a mixture of fully occupied and disordered solvent water molecules. The two independent dap ligands are neutral and the cit tetraanion provides for charge balance, compensating the 4+ cationic charge. There are two well defined coordination geometries in the structure. The simplest is mononuclear, with the Co(II) cation arranged in a regular centrosymmetric octahedral array, coordinated by two aqua ligands, two dap ligands and two O atoms from the β-carboxylate groups of the bridging cit tetraanions. The second, more complex, group is trinuclear, bisected by a twofold axis, with the metal centres coordinated by two cit tetraanions through their α- and β-carboxylate and α-hydroxy groups, and by two dap ligands bridging through one of their pyridine and one of their imidazole N atoms. The resulting coordination geometry around each metal centre is distorted octahedral. Both groups are linked alternately to each other, defining parallel chains along [201], laterally interleaved and well connected via hydrogen bonding to form a strongly coupled three-dimensional network. The compound presents a novel μ4-κ(5)O:O,O':O',O'',O''':O'''' mode of coordination of the cit tetraanion.

Synthesis, crystal structure and magnetic properties of diaquabis(2,6-diamino-7H-purin-1-ium-κN9)bis(4,4′-oxydibenzoato-κO)cobalt(II) dihydrate

“…The choice of 2,6-diaminopurine (DAP) as the aromatic amine came after many successful synthetic experiences we have had in the past (Atria et al, 2009(Atria et al, , 2011(Atria et al, , 2013, which confirmed that the ligand (usually in its cationic HDAP + form) can provide a powerful stabilization effect through its ability ISSN 2053ISSN -2296 # 2018 International Union of Crystallography to promote noncovalent interactions, such asand hydrogen bridges.…”

Solid and solution study of tetranuclear zinc citrates with N-donor chelates

“…Carboxylate-rich polydentate ligands have been used as precursors to assemble Zn(II) ions into aggregates with relevance in bioinorganic chemistry [12]. Citric acid, an α-hydroxytricarboxylic acid, is abundant in physiological fluids and has versatility toward transition metal ions [13,14]. This molecule can give mononuclear, dinuclear, and polynuclear compounds of quite different natures through its binding to metal ions via hydroxy, α-carboxy, and/or one or two β-carboxy groups [15][16][17][18][19][20][21][22][23][24].…”