Quantitative Analysis of the Self-Assembly Process of Hexagonal PtII Macrocyclic Complexes: Effect of the Solvent and the Components.

Abstract

The self-assembly process of three PtII -linked hexagonal macrocycles consisting of dinuclear PtII complexes and organic ditopic ligands was investigated in polar and less polar solvents by a recently developed approach: quantitative analysis of the self-assembly process (QASAP). In polar CD3 NO2 , for all the three macrocycles, an ML2 complex was the dominant intermediate during self-assembly, as a result of high positive allosteric cooperativity for the ligand exchange on the PtII centers of the dinuclear PtII complexes. On the other hand, in less polar CD2 Cl2 , the self-assembly process was affected by the components. For two of the three macrocycles, the chainlike oligomers that contain fewer metals and ligands than the corresponding macrocycles grew with time and the type of the chainlike intermediates formed correlated with the allostericity of the two binding sites in the organic ditopic ligands. In every case, no long oligomers containing more components than the macrocycles themselves were produced during the self-assembly even though free rotation around single bonds in the chainlike oligomers allows them to adopt various conformations that do not facilitate the cyclization. This result suggests that electrostatic and/or steric factors besides rigidity of the components make the cyclization advantageous not only thermodynamically but also kinetically.