1-Iodotriptycene

The title compound, C20H13I, is a halogenated derivative of triptycene. The molecule shows crystallographic as well as non-crystallographic C 3 symmetry. The asymmetric unit comprises one third of the molecule. Dispersive I⋯I contacts [I⋯I = 3.6389 (3) Å] connect the molecules into dimers. The shortest centroid–centroid distance between two π-systems is 3.8403 (12) Å.

The title compound, C 20 H 13 I, is a halogenated derivative of triptycene. The molecule shows crystallographic as well as non-crystallographic C 3 symmetry. The asymmetric unit comprises one third of the molecule. Dispersive IÁ Á ÁI contacts [IÁ Á ÁI = 3.6389 (3) Å ] connect the molecules into dimers. The shortest centroid-centroid distance between two -systems is 3.8403 (12) Å .

Comment
The chemistry of molecules featuring double and triple bonds involving elements from the third row of the periodic system of the elements (or below) is affected by the marked tendency of oligo-and polymerization. The introduction of sterically demanding, "bulky" protective groups in proximity to such bonding systems allowed the isolation and characterization of respective compounds on grounds of steric shielding and, as a consequence, markedly decreased rate of polymerization. It seemed of interest for us to study whether the presence of such aforementioned bonding systems has an influence on the metrical parameters of the applied protection groups as well. Therefore, we determined the crystal structure of the title compound. So far, the molecular and crystal stuctures of 1-bromotriptycene (Palmer & Templeton, 1968), 9,10-dibromotriptycene (Abergel & Dinca, 2004) as well as 10-bromo-9-triptycyl iodoformate (de Wet et al., 1978) are the only examples of structurally characterized triptycene compounds bearing a halogenido substituent on the bridgehead carbon atom present in the literature.
Halogenation took place on one of the bridgehead carbon atoms of the triptycene molecule ( Figure 1). The least-squares planes defined by the atoms of the three aromatic moieties enclose angles of 60.03 (4) ° and 60.03 (7), respectively.
In the molecules, dispersive I···I contacts whose range falls by more than 0.3 Å below the sum of van der Waals radii can be observed (Figure 2). These connect two molecules to dimeric units whose I···I vector is pointing along the crystallographic c axis. The aromatic moieties of one molecule in such a dimer adopt a staggered conformation towards the aromatic moieties in the other molecule when projected along the I···I axis. The closest intercentroid distance between two π-systems was measured at 3.8403 (12) Å.

Experimental
The compound was formed through the thermolysis of 9-triptycyl iodoformate according to a published procedure (Bartel et al., 1971).

Refinement
Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic carbon atoms, C-H 1.00 Å for the bridgehead carbon atom) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C).