The Cr(III) and Ca(II) complexes (dmpH)[Cr(pydc) 2 ]·H 2 O (1) and [Ca 2 (pydc) 2 (H 2 O) 6 ].2pydcH 2 (2) were synthesized by reaction of 2,9-dimethyl-1,10-phenanthroline (dmp) and pyridine-2,6-dicarboxylic acid (pydcH 2 ) with Cr(NO 3 ) 3 and Ca(NO 3 ) 2 , respectively, and characterized using IR spectroscopy, single crystal X-ray diffraction method and solution studies. The space group and crystal system of these two compounds are P2 1 /c and monoclinic. The crystal dimensions are a = 9.785(3) Å, b = 25.671(4) Å, c = 9.3402(16) Å, ȕ = 90.790(17)° for (1) and a = 9.1319(4) Å, b = 14.8430(8) Å, c = 12.2449(7) Å, ȕ = 98.227(5)° for (2). In complex (1), a water molecule presents in the crystal packing, linking the anionic and cationic fragments together by hydrogen bonding and thus increases the stabilization of crystal lattices. In complex (2), the coordinated water molecules relate each dimer to adjacent dimers forming infinite molecular ribbons by strong hydrogen bondings. Hydrogen bonding and ion pairing play an important role in stabilizing these crystals. The complexation reactions of pydc, dmp and pydc+dmp with Cr 3+ and Ca 2+ ions in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed were evaluated.

The homonuclear water-soluble and air stable compounds (dmpH) (H 5 O 2 ) [M(pydc) 2 ].0.5H 2 O (M = Ni(II) (1), Cu(II) (2), Zn(II) (3); pydcH 2 = pyridine-2,6-dicarboxylic acid, dipicolinic acid, dmp = 2,9-dimethyl-1,10-phenanthroline) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, 1 H NMR, 13 C NMR, elemental analysis and X-ray diffraction single crystal analyses for 1, 2 and 3. The complexes 1-3 represent the isostructural features. Extensive hydrogen bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the complex units by linking them to form three dimensional polymeric networks. The stoichiometry and stability of the all three complexes in aqueous solution were investigated by potentiometric pH titration.

The centrosymmetric title compound, [Zn(C14H8N2O8)2(H2O)2], shows a distorted octahedral coordination. The four donor atoms of the two coplanar 3‐carboxypyridine‐2‐carboxylate or (2,3‐pydcH)− anions form a square‐planar arrangement around the ZnII centre. This crystal structure has an infinite three‐dimensional framework. The stabilizing interactions existing in the crystal structure are intermolecular O—H...O and very strong intramolecular O—H...O hydrogen bonds. H atoms of coordinated water molecules participate in hydrogen‐bonded chains described by C22(12) and C11(8) graph‐set descriptors.

No abstract

In the title compound, (C14H13N2)[V(C7H3NO4)O2]·H2O, the VV atom has a distorted trigonal–bipyramidal coordination environment formed by one pyridyl N atom and two O atoms of the [VO2]+ group occupying the equatorial plane, and two carboxylate O atoms occupying the axial positions. O—H...O, N—H...O, O—H...N and C—H...O hydrogen bonds, together with π–π stacking interactions [average centroid‐to‐centroid distance 3.644 (12) Å], seem to be effective in the stabilization of the crystal structure, resulting in the formation of a three‐dimensional supramolecular structure.