New complexes of nickel(ii), copper(ii), and cobalt(ii) derived from bidentate coordinating heteroscorpionate ligands, (4-carboxyphenyl)bis(3,5- dimethylpyrazolyl)methane, (L4c) and (3-carboxyphenyl)bis(3,5-dimethylpyrazolyl) methane, (L3c) have been synthesized and characterized by X-ray diffraction, IR, elemental analysis and UV-vis spectroscopy. By adjusting the reaction conditions the coordination modes of the ligands can be controlled. Solid-state interactions utilizing the strong hydrogen bonding capabilities of protonated and uncoordinated carboxylate groups can be the result of these changed reaction conditions. Finally the different orientation of the carboxylate groups in the ligands L3c and L4c also affect the overall coordination modes and the nature of the solid-state interactions in these systems. © 2008 The Royal Society of Chemistry.