NMR study of complexation of crown ethers with [60]- and [70]fullerenes

[60]- and [70]fullerenes have been shown to form 1:1 molecular complexes with a series of crown ethers, namely, (i) 4'-nitrobenzo-15-crown-5 (1), (ii) dibenzo-24-crown-8 (2), (iii) dibenzo-30-crown-10 (3), (iv) benzo-15-crown-5 (4), and N,N'-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (5) in CCl4 medium by the NMR spectrometric method. Formation constants (K) of the complexes have been determined from the systematic variation of NMR chemical shifts of specific protons of the crown ethers in the presence of [60]fullerene and [70]fullerene. The magnitudes of K indicate that the crown ethers 2 and 3 form inclusion complexes with [60]fullerene but not with [70]fullerene.