Self-Assembly of Water-Soluble Platinum(II)-Based Metallacalixarenes and Tuning Their Conformational Interconversion via Synergistic Effects between Solvents and Anions.

The aqueous self-assembly of the flexible ligand L bis(1H-benz[d]imidazole-1-yl)methane and cis-coordinated PtII precursors [(en)Pt2+ , (tmeda)Pt2+ , en=ethylenediamine, tmeda=N,N,N',N'-tetramethylethylenediamine)] led to the formation of the metallacalixarenes with full alternative conformations (e.g., two novel water-soluble metallacalixarenes [M2 L2 ]4+ and [M3 L3 ]6+ with D2 and D3 symmetry, respectively). Their molecular structures were determined by single crystal X-ray analyses in solid state. The two metallacalixarenes present different cavity sizes and the [M3 L3 ]6+ cavity encapsulates one NO3 - . NOESY NMR revealed that the conformational interconversion between 1,3-alternate conformer in methanol and cone conformer in DMSO was tuned via the synergistic effect between solvent and anion. Guest encapsulation is also discussed.