Aromatic pi-pi interaction mediated by a metal atom: structure and ionization of the bis(eta(6)-benzene)chromium-benzene cluster.

Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea.
Physical Chemistry Chemical Physics (Impact Factor: 4.2). 07/2010; 12(27):7648-53. DOI: 10.1039/b923929d
Source: PubMed

ABSTRACT Aromatic pi-pi interaction in the presence of a metal atom has been investigated experimentally and theoretically with the model system of bis(eta(6)-benzene)chromium-benzene cluster (Cr(Bz)(2)-Bz) in which a free solvating benzene is non-covalently attached to the benzene moiety of Cr(Bz)(2). One-photon mass-analyzed threshold ionization (MATI) spectroscopy and first principles calculations are employed to identify the structure of Cr(Bz)(2)-Bz which adopts the parallel-displaced configuration. The decrease in ionization potential for Cr(Bz)(2)-Bz compared with Cr(Bz)(2), resulting from the increase of the cation-pi stabilization energy upon ionization, is consistent with the parallel-displaced structure of the cluster. Theoretical calculations give the detailed cluster structures with associated energetics, thus revealing the nature of pi-pi-metal or pi-pi-cation interactions at the molecular level.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Singly charged aluminum-benzene cation complexes are produced by laser vaporization in a pulsed supersonic expansion. The Al+(benzene)n (n=1-4) ions are mass selected and investigated with infrared laser photodissociation spectroscopy. Density functional theory (DFT) is employed to investigate the structures, energetics and vibrational spectra of these complexes. Spectra in the C-H stretching region exhibit sharp multiplet bands similar to the pattern known for the Fermi triad of the isolated benzene molecule. In the fingerprint region, strong bands are seen corresponding to the ν19 C-C ring motion and the ν11 out-of-plane hydrogen bend. The hydrogen bend is strongly blue shifted compared to this vibration in benzene, whereas the ν19 carbon ring distortion is only slightly shifted to the red. Computed structures and energetics, together with experimental fragmentation and vibrational patterns, indicate a primary coordination of three benzene molecules around the central Al+ cation. The n=4 complex contains one second-sphere solvent molecule.
    The Journal of Physical Chemistry A 03/2014; · 2.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The IR-UV double resonance spectroscopy of phenylacetylene complexes with triazine, pyrazine and pyridine in the acetylene C-H group of phenylacetylene was investigated. These spectra indicate that in the complexes of triazine, pyrazine and pyridine the acetylenic group is minimally perturbed and the predominant interaction is with the π electron density of the phenyl ring of phenylacetylene. Geometries of the complexes optimized at M06-2X/aug-cc-pVDZ and MP2/aug-cc-pVDZ levels, combined with highly accurate energy calculations at the complete basis set (CBS) limit of CCSD(T), indicate the formation of π-stacked complexes in all the three cases. Additionally, a C-H...N hydrogen-bonded complex between pyridine and phenylacetylene was also observed. The present results indicate that N-heterocyclic aromatic rings favor formation of π-stacked complexes.
    Physical Chemistry Chemical Physics 03/2011; 13(13):5514-25. · 4.20 Impact Factor

Full-text (2 Sources)

Available from
Jun 4, 2014