title: Structure and dynamics of [3.3]paracyclophane as studied by nuclear magnetic resonance and density functional theory calculations.
abstract: Strained cyclophanes with small (-CH(2)-)(n) bridges connecting two benzene rings are interesting objects of basic research, mostly because of the nonplanarity of the rings and of interference of π-electrons of the latter. For title [3.3]paracyclophane, in solutions occurring in two interconverting cis and trans conformers, the published nuclear magnetic resonance (NMR) data are incomplete and involve its partially deuterated isotopomers. In this paper, variable-temperature NMR studies of its perprotio isotopomer combined with DFT quantum chemical calculations provide a complete characterization of the solution structure, NMR parameters, and interconversion of the cis and trans isomers of the title compound. Using advanced methods of spectral analysis, total quantitative interpretation of its proton NMR spectra in both the static and dynamic regimes is conducted. In particular, not only the geminal but also all of the vicinal J(HH) values for the bridge protons are determined, and for the first time, complete Arrhenius data for the interconversion process are reported. The experimental proton and carbon chemical shifts and the (n)J(HH), (1)J(CH), and (1)J(CC) coupling constants are satisfactorily reproduced theoretically by the values obtained from the density functional theory calculations.
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Kasprzaka 44/52, Poland. dodziuk@ichf.edu.pl
authors.forename: Helena
authors.initials: H
authors.lastname: Dodziuk
authors.forename: Sławomir
authors.initials: S
authors.lastname: Szymański
authors.forename: Jarosław
authors.initials: J
authors.lastname: Jaźwiński
authors.forename: Maciej E
authors.initials: ME
authors.lastname: Marchwiany
authors.forename: Henning
authors.initials: H
authors.lastname: Hopf
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D001952:Bridged-Ring Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D001372:Aza Compounds; D001952:Bridged-Ring Compounds