catena-Poly[[bis( pyridine-kappa N) zinc]-mu-5carboxybenzene-1,3-dicarboxylato-kappa(2) O-1 : O-3]

The title one-dimensional coordination polymer, [Zn(C9H4O6)(C5H5N)(2)](n) or [Zn(HBTC)(py)(2)](n), (I), where BTC is benzene-1,3,5-tricarboxylate and py is pyridine, is a solvent-free polymorph of [Zn(HBTC)(py)(2)]. 2C(2)H(5)OH [Yaghi et al. (1997). Chem. Mater. 9, 1074-1076]. Differences in the spatial arrangements and supramolecular packing of the [Zn(HBTC)(py)(2)](n) chains in the two structures are described. The chain in (I) extends parallel to [100] and is severely puckered, with a Zn.. . .Zn distance of 8.3599 (3) (A) over circle and a Zn. . . Zn. . .Zn angle of 107.516 (3) (A) over circle, as a result of hydrogenbonding interactions of the types O-H. . .O and C-H. . .O. There is no evidence for pi-pi interactions in (I). The differences between the solvent- free and solvent-containing structures can be accounted for by the absence of the ethanol solvent molecule and the use of the converging pair of O atoms in the bis-monodentate bridging HBTC2(-) ligand in (I).