Metal complexes of carboxylates

In recent years, great efforts have been devoted to the rational design and synthesis of polynuclear and polymeric coordination compounds composed of transition metal ions and organic ligands. Complexes of carboxylic acids have attracted particular attention, not only because of their intrinsic chemical interest (they include a variety of crystalline compounds with fascinating structural and functional properties, including structures with extraordinarily large pores), but also because of their potential applications as catalysts, molecular adsorbants, or optical, electronic or magnetic materials.
α-Hydroxycarboxylic acids (X) are particularly useful as starting compounds for the synthesis of such materials, since the simultaneous presence of the carboxyl and hydroxyl groups allows their complexes with divalent transition metal ions to exhibit a huge variety of coordination modes (XI-XVIII), and the opportunities they offer for hydrogen bonding allows many of these complexes to form 2D or 3D networks in the solid state.