Through-space interactions between face-to-face, center-to-edge oriented arenes: importance of polar-pi effects.
Two series of conformationally restricted polycyclic compounds (1-3 and 4-7) have been synthesized as model systems for studying the through-space interactions between face-to-face, center-to-edge (parallel-offset) oriented arenes. These compounds feature different X substituents on one of the interacting rings. By monitoring the variation of the delta Gz for the rotation around the aryl-aryl bond in 1-7 as a function of X by 2D [1H,1H] EXSY NMR spectroscopy, it was found that the barriers increase on passing from electron-donating to electron-withdrawing substituted derivatives. Quantum mechanical calculations [MP2/DVZ (2d,p)//B3LYP/DVZ(2d,p)] gave barrier values and variations in agreement with the experimental data. The results are consistent with a repulsive arene-arene interaction dominated by electrostatic effects.
Cozzi
Franco
F
CNR-ISTM, Dipartimento di Chimica Organica e Industriale, Universita' di Milano, via Golgi, 19-20133 Milano, Italy.
Annunziata
Rita
R
Benaglia
Maurizio
M
Cinquini
Mauro
M
Raimondi
Laura
L
Baldridge
Kim K
KK
Siegel
Jay S
JS