Difference in guest-inclusion abilities of anti- and syn-rotamers

Guest inclusion abilities of two rotamers, anti- and syn-N,N'-bis-(2-tert-butylphenyl)naphthalene-1,4,5,8-tetracarboxylic diimides 1 and 2, were investigated. Rotamers 1 and 2 were synthesised from 2-tert-butylaniline and naphthalene-1,4,5,8-tetracarboxylic dianhydride and separated by conventional column chromatography on silica gel. Recrystallisation of 1 from chloroform in the presence of a guest molecule (3 mole equivalents) was performed, and 15 guest molecules were included with a variety of host:guest ratios, 1:1 (chloroform, pyridine, 4-picoline, benzene, quinoline, diphenylacetylene, naphthalene, and p-toluidine), 1:2 (phenol, 3-ethylphenol, 4-methoxyphenol, indole, 5-methylindole, and tetrathiafulvalene), and 1:4 (benzothiazole). In contrast, 2 showed no inclusion of guest molecules under the same conditions as those applied to 1. In order to investigate the intermolecular interaction in the crystalline state of 1, 2 and 1.(indole)(2), X-ray diffraction of single crystals was measured and these structures were compared.