title: Bis(6'-carb-oxy-2,2'-bipyridine-6-carboxyl-ato-κN,N',O)nickel(II) tetra-hydrate.
abstract: In the title compound, [Ni(C(12)H(7)N(2)O(4))(2)]·4H(2)O, the Ni atom is located at the centre of a distorted octa-hedron, formed by four N atoms and two O atoms from the same two tridentating chelated 6-carb-oxy-2,2'-bipyridine-6'-carboxyl-ate (L) ligands. Face-to-face π-stacking inter-actions between inversion-related pyridine rings with centroid-centroid distances of 3.548 (3) and 3.662 (3) Å (perpendicular distances between the respective rings are 3.314 and 3.438 Å) are found. Inter-molecular O-H⋯O hydrogen bonds between water mol-ecules and L ligands form R(5) (3)(10), R(6) (5)(14) and R(5) (5)(12) rings and also a centrosymmetric cage-like unit of water mol-ecules, which link eight adjacent Ni(II) centers, forming a three-dimensional framework.
authors.affiliation: School of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, People's Republic of China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Wang
authors.forename: Haiquan
authors.initials: H
authors.lastname: Su
authors.forename: Jinjin
authors.initials: J
authors.lastname: Xu
authors.forename: Fenghua
authors.initials: F
authors.lastname: Bai
authors.forename: Ya
authors.initials: Y
authors.lastname: Gao