catena-Poly[[bis­(pyridine-κN)zinc]-μ-5-carb­oxy­benzene-1,3-di­carboxyl­ato-κ(2) O (1):O (3)]

The title one-dimensional coordination polymer, [Zn(C(9)H(4)O(6))(C(5)H(5)N)(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) Å and a Zn⋯Zn⋯Zn angle of 107.516 (3)°, as a result of hydrogen-bonding inter­actions of the types O—H⋯O and C—H⋯O. There is no evidence for π–π 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 HBTC(2−) ligand in (I).