Coplanar recognition by a Rebek cleft is provided by cooperative structural effects involving a combination of O-H...O, O-H...N, and C-H...O forces.
Reaction of 2,7-di-tert-butyl-9,9-dimethyl-4,5-xanthenedicarboxylic acid (1), a Rebek cleft, with 1,2-trans-bis(2-pyridyl)ethylene (2) yields a three-component organic assembly, 2(1).2 (3), of nanoscale dimensions that is held together by 10 cooperative O-H.N, O-H.O, and C-H.O hydrogen bonds. The cleft adopts a planar conformation, by forming an intramolecular O-H.O hydrogen bond, which enables the host to recognize the guest in a coplanar orientation that facilitates the cooperativity displayed by the multiple forces.
MacGillivray
L R
LR
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242-1294, USA.
Siebke
M M
MM
Reid
J L
JL