SYNTHESIS AND STRUCTURES OF NITROMETHANE COMPLEXES OF FURANOTRIBENZO-21-CROWN-7 AND DIBENZO-21-CROWN-7

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.