Linear and circular helicates: A brief review

Abstract: Helical self-assembled coordination complexes are broadly classified under linear and circular helicates. While the number of strands of the ligand units in a molecule of the linear helicates is used for further classifications such as single-stranded, double-stranded and so on, the circular helicates are not classified further. The compositions of helicates are considered as M xL y where the terms x and y stand for the number of metal ion(s) and ligand strands, respectively. However, more than one type of metal centers/ligand in helicates are also known. The linear helicates of a given number of strands are further classified under the number of metal centers such as binuclear, trinuclear and so on. Representative examples are included to exemplify the varieties of helicates. Graphical abstract: Synopsis: Helical self-assembled coordination complexes are broadly classified under linear and circular helicates. While the number of strands of the ligand units in the linear helicates is used for further classifications, the circular helicates are put all under one category. Representative examples are included to exemplify the varieties of helicates. Pictogram:[Figure not available: see fulltext.].