Received 16 May 2010
In the title centrosymmetric dimeric CdII complex, [Cd2(C7H5O4)4(C12H8N2)2(H2O)2], the CdII cation is coordinated by a bidentate phenanthroline (phen) ligand, three dihydroxybenzoate (dhba) anions and one water molecule in a distorted CdN2O4 octahedral geometry. Among the dhba anions, two anions bridge two CdII cations to form the dimeric complex with significant different Cd-O bond distances of 2.2215 (19) and 2.406 (2) Å. The centroid-centroid distance of 3.4615 (19) Å between two nearly parallel benzene rings of the dhba and phen ligands coordinating to the same CdII cation indicates the existence of intramolecular - stacking in the complex. Extensive O-HO hydrogen bonding and intermolecular weak C-HO hydrogen bonding help to stabilize the crystal structure. One hydroxy group of the monodentate dhba ligand is disordered over two sites with a site-occupancy ratio of 0.9:0.1.
For the correlation between - stacking and electron-transfer processes in some biological systems, see: Deisenhofer & Michel (1989). For general background to - stacking, see: Li et al. (2005). For - stacking involving a dihydroxybenzoate ligand in an Ni complex, see: Yang et al. (2006). Intramolecular - stacking was previously observed in a Sr complex with a hydroxybenzoate ligand, see: Su et al. (2005).
Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NG2775 ).
The project was supported by the ZIJIN project of Zhjiang University, China.
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