Four new 5-aminoisophthalates of cobalt and nickel have been prepared employing hydro/solvothermal methods: [Co-2(C8H5NO4)(2)(C4H4N2)(H2O)(2)]center dot 3H(2)O (1), [Ni-2(C8H5NO4)(2)(C4H4N2)(H2O)(2)]center dot 3H(2)O (II), [Co-2(H2O)(mu(3)-OH)(2)-(C8H5NO4)] (III), and [Ni-2(H2O)(mu(3)-OH)(2)(C8H5NO4)] (IV), Compounds I and II are isostructural, having anion-deficient CdCl2 related layers bridged by a pyrazine ligand, giving rise to a bilayer arrangement. Compounds III and IV have one-dimensional M-O(H)-M chains connected by the 5-aminoisophthalate units forming a three-dimensional structure The coordinated as well as the lattice water molecules of I and II could be removed and inserted by simple heating-cooling cycles under the atmospheric conditions The removal of the coordinated water molecule is accompanied by changes in the coordination environment around the M2+ (M = Co, Ni) and color of the samples (purple to blue, Co; green to dark yellow, Ni). This change has been examined by a variety of techniques that include in situ single crystal to single crystal transformation studies and in situ IR and UV-vis spectroscopic studies. Magnetic studies indicate antiferromagnetic behavior in I and II, a field-induced magnetism in III, and a canted antiferromagnetic behavior in IV.