catena-Poly[[diaquabis(isoquinoline-κN)cobalt(II)]-μ-succinato-κ2 O 1:O 4]

In the title compound, [Co(C4H4O4)(C9H7N)2(H2O)2]n, the CoII cation, located on an inversion center, is coordinated by two succinate anions, two isoquinoline ligands and two water molecules in a distorted octahedral geometry. The succinate anion, located across another inversion center, bridges the Co cations, forming polymeric chains running along the b axis. The partially overlapped arrangement of parallel isoquinoline ring systems of adjacent polymeric chains and the shorter face-to-face distance of 3.402 (6) Å indicates the existence of weak π–π stacking in the crystal structure. Classical intra- and intermolecular O—H⋯O hydrogen bonding and weak non-classical intermolecular C—H⋯O hydrogen bonding help to stabilize the crystal structure.

In the title compound, [Co(C 4 H 4 O 4 )(C 9 H 7 N) 2 (H 2 O) 2 ] n , the Co II cation, located on an inversion center, is coordinated by two succinate anions, two isoquinoline ligands and two water molecules in a distorted octahedral geometry. The succinate anion, located across another inversion center, bridges the Co cations, forming polymeric chains running along the b axis. The partially overlapped arrangement of parallel isoquinoline ring systems of adjacent polymeric chains and the shorter faceto-face distance of 3.402 (6) Å indicates the existence of weak stacking in the crystal structure. Classical intra-and intermolecular O-HÁ Á ÁO hydrogen bonding and weak nonclassical intermolecular C-HÁ Á ÁO hydrogen bonding help to stabilize the crystal structure.

Comment
The π···π stacking between aromatic rings is an important non-covalent interaction and correlated with the electron transfer process in some biological systems (Deisenhofer & Michel, 1989). As part of our ongoing investigation on the nature of π···π stacking (Su & Xu, 2004;Xu et al., 2007), the title complex incorporating isoquinoline ligand has recently been prepared in the laboratory and its crystal structure is reported here.
A part of the polymeric molecular structure is shown in Fig. 1. The Co II cation located on an inversion center is coordinated by two succinate anions, two isoqiunoline ligands and two water moleculaes with a distorted octahedral geometry. The succinate anion is located across another inversion center, and bridges Co cations to form the one-dimensional polymeric chains running along the crystallographic b axis, similar to that found in a Ni II complex bridged by siccinate anions (Liu et al., 2003). The carboxyl group is oriented with respect to the carbon skeleton of succinate anion at a dihedral angle of 28.4 (2)°.
The partially overlapped arrangement of parallel isoqiunoline ring systems of adjacent polymeric chains related by a symmetry operation of (1-x, 1-y, -z) and shorter face-to-face distance of 3.402 (6)Å indicate the existence of weak π···π stacking in the crystal structure. Classical intra-and intermolecualr O-H···O hydrogen bonding and weak non-classical intermolecular C-H···O hydrogen bonding help to stabilize the crystal structure (Table 1).

Refinement
Water H atoms were located in a difference Fourier map and refined as-riding in as-found relative positions with U iso (H) = 1.2U eq (O). Other H atoms were placed in calculated positions with C-H = 0.93Å (aromatic) and 0.97Å (methylene), and refined in riding mode with U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures   Fig. 1. A part of the polymeric molecular structure of the title compound with atom numbering scheme. Displacement ellipsoids are drawn at 50% probability level. H atoms are presented as a small spheres of arbitrary radius. Symmetry codes: (i) 1-x, -y, 1-z; (ii) 1-x, 1-y, 1-z.