Jh. Burns et al., SYNTHESIS AND STRUCTURES OF NITROMETHANE COMPLEXES OF FURANOTRIBENZO-21-CROWN-7 AND DIBENZO-21-CROWN-7, Journal of inclusion phenomena and molecular recognition in chemistry, 26(4), 1996, pp. 197-207
Single crystal X-ray diffraction analyses of two nitromethane complexe
s of furanotribenzo-21-crown-7 (1 and 2) and the nitromethane complex
of dibenzo-21-crown-7 (3) are reported. The two nitromethane complexes
1 and 2 are polymorphic in that the macrocyclic ring adopts the 'dent
ist's chair' conformation in both structures, with a single nitrometha
ne molecule coordinating to either the lower, concave (1) or upper, co
nvex (2) face of the crown ether. Complex 3 adopts an entirely differe
nt conformation with a coplanar arrangement of the crown ether oxygen
atoms binding a single nitromethane molecule.