title: The strength of parallel-displaced arene-arene interactions in chloroform.
abstract: [reaction: see text] Triptycene-derived compounds have been prepared to serve as conformational equilibrium reporters for direct measurements of arene-arene interactions in the parallel-displaced orientation. A series of such compounds bearing arenes with different substituents were synthesized, and the ratios of the syn and anti conformers were determined by variable-temperature NMR spectroscopy. The syn conformer allows attached arenes to interact with each other while the anti conformer does not. The free energies derived from the syn/anti ratios in chloroform range from slightly positive (0.2 kcal/mol) to considerably negative (-0.98 kcal mol) values. The interactions between the arenes bearing electron-donating groups (EDG) are either negligible or slightly repulsive, while the interactions between arenes bearing electron-withdrawing groups (EWG) are attractive. Intermediate free energy values are obtained for those compounds bearing arenes with one EDG and one EWG.
authors.affiliation: Department of Chemistry & Biochemistry, Miami University, Oxford, Ohio 45056, USA. gungbw@muohio.edu
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Gung
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Xue
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Reich