The conformational behaviour of thiacalix[4]arenes: the pinched cone–pinched cone transition

This work is focused on the dynamics and thermodynamics of the pinched cone ↔ pinched cone interconversion of calix[4]arenes. The behaviour of methylene bridged non-substituted tetraalkoxycalix[4]arene and its tetraalkoxythiacalix[4]arene analogue is compared. Energetic and structural changes during this interconversion have been closely studied by HF and DFT quantum chemistry methods in combination with temperature -dependent 1H NMR spectroscopy. The most important stationary points—minima and transition states—on the potential energy surface have been identified and their symmetry and other structural properties have been determined.