Acta Crystallographica Section B

Structural Science

Volume 55, Part 3 (June 1999)

research papers

Acta Cryst. (1999). B55, 410-423 [ doi:10.1107/S0108768198016140 ]

The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state. Structures of a planar organic cation with various monovalent and divalent anions

F. C. Krebs, B. W. Laursen, I. Johannsen, A. Faldt, K. Bechgaard, C. S. Jacobsen, N. Thorup and K. Boubekeur

Abstract: The geometry of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state was established by X-ray structural resolution of the salts formed between the cation and various anions. The geometry was found to be planar for the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium and 2,6,10-tri(tert-butyl)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium cations with the monovalent anions I^-, BF, PF, AsF, HNO₃.NO and CF₃SO, and the divalent anions S₂O $_6^{2-}$ and Mo₆Cl $_{14}^{2-}$ . The salts were found to crystallize in distinct space groups following a characteristic pattern. Mixed cation-anion stacking resulted in space groups with high symmetry: Pbca in three cases and R3c in one; a temperature study of the latter was made at ten different temperatures. The formation of dimers of anions and cations resulted in lower-symmetry space groups, mainly monoclinic (P2₁/n, P2₁/c and C2/c), but also P1.