1. Bond Compression in Triptycene-Containing In-Cyclophanes
Robert A. Pascal, Jr., Department of Chemistry, Tulane University, New Orleans, LA 70118
An In-Ketocyclophane
The effect of modest conformational restrictions on molecular geometry is dramatically illustrated by the X-ray
structures of benzophenone-containing cyclophanes 1 and 2. In compound 1, the carbonyl group is essentially
parallel to the basal aromatic ring. However, oxidation of the thioethers of 1 to the sulfones of 2 causes the
molecule to a adopt a C2-symmetric conformation with the carbonyl pointed directly toward the basal ring. The
in-ketone oxygen is 2.91 Å from the center of the basal ring, and its infrared stretching frequency (1658 cm-1) is
enhanced by 5 cm-1 when compared to that of 1 (1653 cm-1), an indicator of modest steric compression. 1 2