title: Supramolecular architectures of novel chromium(III) oxalate complexes: steric effects of the ligand size and building-blocks approach.
abstract: Five new oxalate complexes of chromium(III), [Hphen][Cr(phen)(C(2)O(4))(2)]·2H(2)O (1), [Cr(phen)(2)(C(2)O(4))][Cr(phen)(C(2)O(4))(2)]·3H(2)O (2), [Cr(phen)(2)(C(2)O(4))]NO(3)·H(2)C(2)O(4)·H(2)O (3), [Cr(bpy)(2)(C(2)O(4))][Cr(bpy)(C(2)O(4))(2)]·3H(2)O (4) and [Cr(bpy)(2)(C(2)O(4))]NO(3)·1/2H(2)C(2)O(4)·4H(2)O (5) (phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine), were prepared by using an (oxalato)tantalate(V) solution as a source of oxalate ligands. The compounds contain either the discrete mononuclear [Cr(L)(2)(C(2)O(4))](+) cation [L = phen (3); L = bpy (5)] or the discrete mononuclear [Cr(L)(C(2)O(4))(2)](-) anion [L = phen (1)], or both types of mononuclear ions [L = phen (2); L = bpy (4)]. The crystal structures are dominated by the hydrogen-bonding and π···π-stacking interactions that give rise to the overall two- (compounds 1, 2, 4, 5) or three-dimensional (compound 3) architectures. Compounds 2 and 4 represent a borderline case between isostructurality and non-isostructurality; they exhibit an analogous packing of the cation and the anion units, but the crystallization water molecules occupy different positions - due to a difference in size between the phen and bpy ligands. The influence of steric factors is evident also in the case of 3 and 5, which, despite very similar chemical formulae, exert a completely different packing of the constituents. By the self-assembling of 1 and 4, used as building blocks in the reaction with calcium(II) cations, the heterobimetallic polymeric compounds {[CaCr(2)(phen)(2)(C(2)O(4))(4)]·5H(2)O}(n) (6) and {[CaCr(2)(bpy)(2)(C(2)O(4))(4)]·0.83H(2)O}(n) (7) were obtained. The crystal structure of 7 is reported: the [Cr(bpy)(C(2)O(4))(2)](-) unit, through the two oxalate groups, acts as a chelating ligand towards Ca cations, resulting in heterometallic one-dimensional double zigzag chains, formed of diamond-shaped units. The characterization of the compounds obtained was accomplished by the spectroscopy and thermal analysis methods.
authors.affiliation: Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia.
authors.forename: Lidija
authors.initials: L
authors.lastname: Androš
authors.forename: Marijana
authors.initials: M
authors.lastname: Jurić
authors.forename: Krešimir
authors.initials: K
authors.lastname: Molčanov
authors.forename: Pavica
authors.initials: P
authors.lastname: Planinić
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry; D002857:Chromium / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008024:Ligands; D008968:Molecular Conformation; D010070:Oxalates / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D010070:Oxalates; D010618:Phenanthrolines; D002857:Chromium; D015082:2,2'-Dipyridyl; C025205:1,10-phenanthroline