2,2'-Bipyridyl-3,3'-dicaxboxylic acid (H2BDC) spontaneously resolves on crystallization from water, giving monohydrated crystals of the space group P2(1)2(1)2(1). In any individual crystal, all the atropisomeric-skewed molecules are of one hand; however, on dissolution in water, optical activity is lost. Strong hydrogen bonding leads to a helical structure, via O-H...N links, and 3 further strong bonds between water and carboxylate groups produce a framework structure. The pK(a) values measured for H2BDC (3.18 +/- 0.04 and 4.59 +/- 0.02 at 20 +/- 1 degreesC, in dilute aqueous solution) agree with the zwitterionic form. The reaction of H2BDC with potassium tetrachloroplatinate(II) in water gives Pt(H2BDC)Cl-2.H2O. The complex was characterized by elemental analysis and spectroscopic techniques.