5,10-Dihydroindeno[2,1-a]indene

13,13'-Bi(dibenzo[a,i]fluorenyl-idene)

The asymmetric unit of the title compound, C42H24, contains two almost identical mol-ecules. The mol-ecules have approximate D 2 symmetry. They show a largely twisted double bond, the mol-ecular halves enclosing dihedral angles of 62.86 (4) and 61.22 (3)°. The crystal studied was twinned by non-merohedry.

The head-to-head photodimer of indeno-indene

Irradiation of 1-(1-benzo-cyclo-butenyl-idene)benzo-cyclo-butene gives indeno-indene and its head-to-head photodimer nona-cyclo-[9.7.7.72,10.01,11.02,10.03,8.012,17.019,24.026,31]dotriaconta-3,5,7,12,14,16,19,21,23,26,28,30-dodeca-ene, C32H24. The mol-ecule is built from four essentially planar indane units attached to an elongated cyclo-butane ring. In the crystal, C-H⋯π inter-actions connect mol-ecules into layers parallel to the bc plane.