title: Ortho-rhom-bic polymorph of (2E)-2-(2,3-dihydro-1H-inden-1-yl-idene)-2,3-di-hydro-1H-inden-1-one.
abstract: The title compound, C(18)H(14)O, is polymorphic at 123 K. The ortho-rhom-bic form reported herein has two independent mol-ecules in the asymmetric unit, with mol-ecular volume 313.5 Å(3). The previously reported triclinic (P-1) form [Raston & Scott (2000 ▶). Green Chem., 2, 49-52] has mol-ecular volume 309.6 Å(3) at the same temperature. All three mol-ecules deviate significantly and systematically from the putative C(s) symmetry (δ(r.m.s.) = 0.0265, 0.0256, 0.0497 Å). Comparison of the two molecules in the orthorhombic polymorph shows that 16 of the 19 equivalent pairs of framework atoms have a mirror-image pattern of deviations (above/below plane), suggesting that the two are quasi-enanti-omorphs. The pattern of deviations in the triclinic form is nearly the same (13 of 19 atom pairs) as the ortho-rhom-bic form.
authors.affiliation: Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804,  USA.
authors.forename: Hairong
authors.initials: H
authors.lastname: Li
authors.forename: Frank R
authors.initials: FR
authors.lastname: Fronczek
authors.forename: Steven F
authors.initials: SF
authors.lastname: Watkins