Spectroscopic studies of hydrogen-bond structures and dynamics of partially methylated p-tert-butylcalix[6]arenes

Abstract

Hydrogen-bond structures of partially methylated p-tert-butylcalix[6]arenes were investigated both in solution and the solid state by Fourier transform infrared spectroscopy (FTIR). The hydrogen bonds in these macrocycles are preferentially of the three-centred and cooperative types. The dynamic behaviour of these calix[6]arenes is characterized by fast rearrangement of the methoxy groups in the calix[6]arene annulus and was investigated by means of 2D NMR spectroscopy. The conformational behaviour is primarily dominated by an interplay of favourable hydrogen-bond formation and the tendency of ‘selfinclusion’ of the methoxy groups.