Structural diversity of anthraquinone substituted p-tert-butylthiacalix[4]arene in the partial cone conformation upon external stimuli

Abstract

Crystallisation of anthraquinone substituted p-tert-butylthiacalix[4]arene in the partial cone conformation from a range of solvents led to the isolation of two solvates, containing a mixture of chloroform and acetonitrile (PC1a) or toluene (PC1d) molecules, the structures of which were uncovered by SCXRD studies. Upon heating, the former solvate undergoes a single-crystal-to-single-crystal transformation, leading to removal of the acetonitrile molecules from the host and repositioning of the chloroform molecules (PC1b). This is connected with rearrangements of the non-covalent interactions, nicely reflected by a change in the hydrogen bond acceptor of the weak C–H⋯O hydrogen bonds. The transformation process is reversible, as confirmed by exposure of the crystal to acetonitrile vapour. Furthermore, the guest free phase of PC1 was obtained by melt crystallisation (PC1c).