X-ray diffraction and 13C solid-state NMR studies of the dimethylformamide solvate of tetra(C-undecyl)calix[4]resorcinarene

Lipophilic tetra(C-undecyl)calix [4] resorcinarene obtained from resorcinol and lauryl aldehyde forms solvates with many organic solvents. Particularly good quality crystals are obtained from dimethylformamide. Single-crystal X-ray diffraction (XRD) analysis of the solvate shows that the calix[4]resorcinarene molecules form centrosymmetric dimers held by van der Waals interactions of the C-undecyl aliphatic chains. The dimers are associated into layers with hydroxyl groups at the surfaces. Three types of solvent molecules are embedded in the crystal lattice: disordered isolated molecules located just above the cavities formed by the resorcinol units, clusters of four DMF molecules located between the calixarene layers, and single DMF molecules located inside: the layers close to the alkyl chains. The solvent molecules join the layers of calix[4]resorcinarenes by means of various hydrogen bonds. The C-13 CP/MAS spectra are in agreement with the XRD results.