Multitopic metal–organic carboxylates available as supramolecular building units
Nobuto Yoshinari, Takumi Konno
Abstract
Organic polycarboxylates that exhibit high designability and stability are fundamental building units for constructing coordination and hydrogen-bonded frameworks in supramolecular chemistry. Recently, discrete metal complexes with noncoordinating carboxy moieties (Metal-Organic Carboxylates or Metal-Organic Carboxylic acids; MOCs) have attracted increasing attention as alternatives to organic carboxylates because of their simple synthetic procedures and structural diversity, as well as the ease of installing transition metal centers to provide molecular functionalities. This review provides an overview of multitopic MOCs with six or more noncoordinating carboxy groups, which are constructed via coordination of organic ligands with carboxylates to appropriate metal ions. The MOCs are classified by the type of donating elements present in the organic ligands employed, and their synthetic approaches and molecular and supramolecular structures are described. Of more than 100 multitopic MOCs described herein, 27 MOCs were used as the pre-prepared metalloligand for constructing metal–organic frameworks or coordination polymers. Such MOCs are stable in solution due to the chelate effect of the ligand motifs or the large ligand field stabilization energy of specific metal ions. Moreover, due to their high hydrophilicity, multitopic MOCs are available for biological applications and adsorption of hydrophilic molecules.