Molecular engineering. 8. Kinetic and conformational studies of resorcin [4]arene-based C4 tetraoxatetrathiahemicarceplexes: carceroisomerism and twistomerism.

New C4v tetraoxatetrathiahemicarcerands and their six hemicarceplexes containing DMF, DMA, DMSO, or NMP were synthesized and characterized. Their conformations, kinetic properties, carceroisomerism, and twistomerism were studied by VT, 2D COSY, NOESY, and ROESY 1H NMR experiments. The decomplexation rates of DMF or DMA were very slow with high activation energy barriers (73 and 104 kJ mol-1, respectively) and the complexed guests feel more constriction than their free liquid state. The largest isomerization energy barrier of carceroisomers was 15.4 kcal mol-1, and the isomerization energy barriers of twistomers are significantly larger than those of carceroisomers.