M. Pietraszkiewicz et al., X-ray diffraction and C-13 solid-state NMR studies of the dimethylformamide solvate of tetra(C-undecyl)calix[4]resorcinarene, J PHYS CH B, 104(9), 2000, pp. 1921-1926
Lipophilic tetra(C-undecyl)calix [4] resorcinarene obtained from resorcinol
and lauryl aldehyde forms solvates with many organic solvents. Particularl
y good quality crystals are obtained from dimethylformamide. Single-crystal
X-ray diffraction (XRD) analysis of the solvate shows that the calix[4]res
orcinarene molecules form centrosymmetric dimers held by van der Waals inte
ractions of the C-undecyl aliphatic chains. The dimers are associated into
layers with hydroxyl groups at the surfaces. Three types of solvent molecul
es are embedded in the crystal lattice: disordered isolated molecules locat
ed just above the cavities formed by the resorcinol units, clusters of four
DMF molecules located between the calixarene layers, and single DMF molecu
les located inside: the layers close to the alkyl chains. The solvent molec
ules 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.