3-(3',5'-DINITROPHENYL)-4-(2',5'-DIMETHOXYPHENYL)CYCLOBUTANE-1,2-DICARBOXYLIC ACID - ENGINEERED TOPOCHEMICAL SYNTHESIS AND MOLECULAR AND SUPRAMOLECULAR PROPERTIES

The title compound (1b), synthesized using the principles of crystal engineering, exhibits interesting molecular and supramolecular properties. Diacid 1b crystallizes in the triclinic space group P1BAR, a = 8.150(1), b = 8.927(2), c = 17.894(4) angstrom; alpha = 98.91(1), beta = 97.60(1), gamma = 110.62(2)-degrees, and the structure was solved and refined to an R factor of 0.063 on 2910 nonzero reflections. Intramolecular charge transfer in 1b was studied spectroscopically. Through-bond coupling (TBC) and the resultant C-C bond elongation are observed in lb to a moderate extent. A more general Cambridge Structural Database (CSD) study on 1,2-diphenylethanes provides clear evidence for the molecular attributes required for TBC. Diacid 1b forms a host-guest complex with toluene in which the orientation of the guest molecule is perfectly tuned to the steric and electronic requirements of the host. The toluene guest molecule induces a convergent supramolecular cage, while another divergent supermolecule results because of the zigzag hydrogen-bonded chains of carboxyl groups. A water molecule, seemingly inadvertently trapped in the carboxyl channels, is not involved in hydrogen bonding but is a mere space filler. A general analysis of the solvation properties of benzene, toluene, and water is presented.