Metal self-recognition: a pathway to control the formation of dihelicates and mesocates

Abstract

We have studied the factors that affect the formation of different metallosupramolecular architectures by metal direct self-assembly. A synthetic route has been developed to obtain mesocates or dihelicates selectively. For this purpose a series of five bisthiosemicarbazone ligands derived from 1,3-diacetylbenzene were designed and synthesised. Namely H₂L^Me, H₂L^Et, H₂L^Ph, H₂L^PhN and H₂L^PhOMe with different substituents on the 4-N terminal position of the thiosemicarbazone strands. The Co(II), Zn(II) and Cd(II) complexes of these ligands were prepared by an electrochemical procedure. Crystallographic studies revealed the formation of mesocates for Co(II) and Zn(II) metal ions whereas the Cd(II) complexes gave a bishelical supramolecular structure. Therefore these bisthiosemicarbazone ligands enable the selective isolation of mesocate or dihelicate complexes by using a specific metal ion.