Computational Studies of Inclusion Phenomena and Synthesis of a Novel and Selective Molecular Receptor for 1,4-Disubstituted Benzenes and 4,4‘-Disubstituted Biphenyls

• Published in: Journal of organic chemistry 2000-04, Vol.65 (7), p.2083-2089
• Main Authors: Macias, Alba T, Kumar, Kaipenchery A, Marchand, Alan P, Evanseck, Jeffrey D
• Format: Article
• Language: English
• Subjects: AROMATICS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MATHEMATICAL MODELS; RECEPTORS; SYNTHESIS
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo991669v

A new tetracationic molecular receptor has been synthesized and studied by semiempirical molecular orbital theory. This novel macrocycle, 1 4+, derived from pentacyclo[5.0.0.0.2,60.3,1005,9]undecane-8,11-dione (PCU-8,11-dione), structurally resembles cyclobis(paraquat-p-phenylene), 2 4+, in which a xylyl group has been replaced by a PCU unit. This derivatization effectively increases the size and flexibility of 1 4+ and changes its electronic, dynamical, and binding properties. A conformational search using Osawa's corner flapping technique and the PM3 semiempirical method identifies eight unique and low-energy 1 4+ conformers. The principal regions of structural variation occur in the bipyridinium torsion and in the ethylene bridges between PCU and the tetracationic unit. The inclusion complexes of 1 4+ with 1,4-disubstituted benzenes and 4,4‘-disubstituted biphenyls have been studied by PM3. The first shell of solvation is approximated by the explicit inclusion of 12 acetonitriles in the computed supramolecular complexes. Binding of 1,4-disubstituted benzenes and 4,4‘-biphenol is shifted from the 1 4+ geometric center. From the computations, host 1 4+ is predicted to have an enhanced binding preference for benzidine over 4,4‘-biphenol, as compared to 2 4+. For all guests computed, 1 4+ binds more strongly than 2 4+. These properties can be exploited in the future design of supramolecular systems with potential applications as nanoscale devices.