Using Complementary Ligand Denticity to Direct Metallosupramolecular Structure about Metal Ions with Square-Planar Geometry

An understanding of methods to control the structure of self-assembled architectures is central to the efforts of chemists interested in self-assembly synthesis. Metal ions with square-planar geometry are a favorite of metallosupramolecular chemists, as there are only a limited number of possible ligand arrangements around the metal ion. Two such arrangements, firstly four monodentate donor sites (1,1,1,1), and secondly two monodentate donors and one bidentate donor (1,1,2) exemplify the symmetry interaction and ligand directed approaches, respectively. Symmetry interaction approaches using two bidentate sites (2,2) or a monodentate and tridentate site (1,3) have not received the same level of attention. In these arrangements, two complementary sites combine at the metal ion(s). This Minireview seeks to detail strategies employed to direct structure in systems with these arrangements, and is illustrated with key exemplars from the field.