title: Stacking interactions between nitrogen-containing six-membered heterocyclic aromatic rings and substituted benzene: studies in solution and in the solid state.
abstract: The stacking interactions between an aromatic ring and a pyridine or a pyrimidine ring are studied by using a series of triptycene-derived scaffolds. The indicative ratios of the syn and anti conformers were determined by variable-temperature NMR spectroscopy. The syn conformer aligns the attached aromatic ring and the heterocycle in a parallel-displaced orientation while the anti conformer sets the two rings apart from each other. Comparing to the corresponding control compounds where a benzene ring is in the position of the heterocycle, higher attractive interactions are observed as indicated by the higher syn/anti ratios. In general, the attractive interactions are much less sensitive to the substituent effects than the corresponding nonheterocycles. The greatest attractive interactions were observed between a pyrimidine ring and a N,N-dimethylaminobenzene, consistent with a predominant donor-acceptor interaction. The interactions between a pyridine ring and a substituted benzene ring show that the pyridine is comparable to that of a NO2- or a CN-substituted benzene ring except for the unpredictable substituent effects.
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: Francis
authors.initials: F
authors.lastname: Wekesa
authors.forename: Charles L
authors.initials: CL
authors.lastname: Barnes
mesh_terms: D001554:Benzene / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry*; D012996:Solutions
chemical_list: D006571:Heterocyclic Compounds; D012996:Solutions; D001554:Benzene; D009584:Nitrogen