A novel class of complexes of the type [M(H₂O)₆](optp)₂ (where M = Mg, Ni, Zn, and optp = 1-oxopyridinium-2-thiopropionate) were prepared hydrothermally from metal acetates and 1-oxopyridinium-2-thiopropionic acid (Hoptp), and structurally characterized by X-ray diffraction. Complexes [Mg(H₂O)₆](optp)₂ (1), [Ni(H₂O)₆](optp)₂ (2) and [Zn(H₂O)₆](optp)₂ (3) have isomorphic structures, consisting of one [M(H₂O)₆]²⁺ cation and two anions of Hoptp, which are linked through hydrogen bonding to form extended networks. In each case, the metal cation sits on a crystallographic centre of inversion and binds to six water molecules. The organic anions form a one-dimensional chain with the hexaaquametal(II) moieties via hydrogen bonds.

A convenient and clean procedure for esterification is reported. Direct condensation of formylphenoxyaliphatic acids with low to high boiling alcohols catalysed by potash alum gave moderate to good yields. This catalyst could be recovered and reused without substantial loss in its catalytic activity and the methodology could be used for a range of closely related substrates.