3,4,5,6-Tetrafluoro-1,2,7,8-tetrakis(trifluoromethyl)phenanthrene and 3,4,7,8-Tetrafluoro-1,2,5,6-tetrakis(trifluoromethyl)anthracene

A photocyclization reaction produces two isomers of C₁₈H₂F₁₆. Crystal structures show the major product to be 3,4,5,6-tetrafluoro-1,2,7,8-tetrakis(trifluoromethyl)phenanthrene, (1), and the minor product to be 3,4,7,8-tetrafluoro-1,2,5,6-tetrakis(trifluoromethyl)anthracene, (2). The phenanthrene skeleton in (1) is distorted from planarity by steric interaction between the 4- and 7-F atoms. Compound (2) is centered on an inversion center; the anthracene skeleton is nearly planar, with the trifluoromethyl atoms displaced on either side of the molecular plane.