A CH/pi interaction at a highly solvated macrocycle in the solid state - the p-tert-butylcalix[8]arene-chloroform 1 : 8 clathrate

The crystal structure of the p-tert-butylcalix[8]arene-chloroform 1.8 clath rate (C88H112O8 . 8 CHCl3: P1, a=13.886(2)Angstrom, b=21.891(4)Angstrom, c= 21.930(4)Angstrom, alpha = 64.00(2)degrees, beta = 78.97(2)degrees, gamma = 88.75(2)degrees, Z = 2) features a strong CH/pi interaction of one chlorof orm molecule with the pi system of one phenol ring of the calix[8]arene moi ety; the seven other chloroform molecules occupy interstitial places in the crystal lattice of a highly solvated macrocyclic system (c = 0.566 mol dm( -3)). A thermogravimetric analysis also shows that one solvent molecule is bound more tightly than the others. The observed binding motif is presumabl y based on a subtle interplay between favourable interactions (CH/pi and to some extent Cl/pi) and induced fit between host and guest.