Clathration of properly functionalized calix[4]arenes: C-13 CP-MAS NMR spectroscopy and X-ray crystallography

The clathrate formation of a series of differently upper-rim-functionalized tetrapropoxycalix[4]arenes has been investigated. In the cases of 5,17-dinitro-, 3, and 5,17-diphthalimidocalix[4]arene, 5, clathrates were obtained with benzene, toluene, p-xylene, and anisole, and for 3 also with o- and m-xylene, mesitylene, chlorobenzene, and nitrobenzene. The clathrate formation of 3 with toluene and p-xylene has been studied with ¹³C CP-MAS NMR spectroscopy. In the latter case X-Ray analys is at 173 K revealed that the p-xylene is located between the calix[4 ]arenes in channels. X-Ray analysis at 173 K and ¹³C CP-MAS spectroscopy of the clathrate of tetra-tert-butylcalix[4]arene, 12, and acetonitrile showed that the guest is located in the cavity of the calix[4]arene. In the case of calix[4]arene tetracarbonate, 13, a 1:2 clathrate with acetonitrile was obtained with one guest molecule in- and one out side the cavity.