Quantitative Analysis of the Self-Assembly Process of Hexagonal Pt^II Macrocyclic Complexes: Effect of the Solvent and...

The self-assembly process of three Pt^II -linked hexagonal macrocycles consisting of dinuclear Pt^II 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 Pt^II centers of the dinuclear Pt^II 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.