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

New C-4v, tetraoxatetrathiahemicarcerands and their six hemicarceplexes con taining DMF, DMA, DMSO, or NMP were synthesized and characterized. Their co nformations, kinetic properties, carceroisomerism, and twistomerism were st udied by VT, 2D COSY, NOESY, and ROESY H-1 NMR experiments. The decomplexat ion 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 c onstriction than their free liquid state. The largest isomerization energy barrier of carceroisomers was 15.4 kcal mol(-1), and the isomerization ener gy barriers of twistomers are significantly larger than those of carceroiso mers.