An aqueous solution of the ix,w-dicarboxylic acid octanedioic acid (odaH2) reacts with [Cui(µ-O2CCH3MH2O)i] in the presence of an excess of pyridine (py) to give the crystalline copper(II) complex {Cui(ry 1ry 1µrodah(pyMH2O)2}" (1). The structure of 1, as determined by X-ray crystallography, consists of polymeric chains in which bridging oda2 - anions link two crystallographically identical copper atoms. The copper atoms are also ligated by two transoidal pyridine nitrogens and an oxygen atom from an apical water molecule, giving the metals an overall N203 square-pyramidal geometry. If the blue solid 1 is gently heated, or if it is left to stand in its mother liquor for prolonged periods, it loses one molecule of pyridine and half a molecule of water and the green complex { Cu (oda)(py)(H2O)05}n (2) is formed. Spectroscopic and magnetic data for both complexes are given, together with the electrochemical and thermogravimetric measurements for 1.