The structure of quinuclidine (1-azabicyclo(2.2.2.) octane) as determined by gas phase electron diffraction

Schei, H.; Shen, Quang; Hilderbrandt, R. L.

doi:10.1016/0022-2860(80)85204-5

Cited by 12 publications

(6 citation statements)

References 8 publications

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“…S1, † the least-squares correlation matrix is in Table S3 † and the Cartesian coordinates for the final structure are in Table S4. † The newly refined structure is similar to that determined by Schei et al 10 The average C-C distance [1.552(2) A ˚] from the earlier refinement lies almost midway between the two experimental values determined here and the C-N distance [1.469(3) A ˚] in the original report lies within 0.006 A ˚of that presented here. Although three studies of the crystalline structure of 1 have been reported, none of these describes the molecular structure of the disordered compound.…”

Section: Ged Refinementssupporting

confidence: 87%

“…In the context of vapour deposition techniques, in which these thermally robust compounds may be applied, it is particularly important to have a thorough understanding of the structures of both the quinuclidine adducts and quinuclidine itself in the gas phase. A gas-phase electron diffraction (GED) study of quinuclidine was published more than 25 years ago, 10 but various assumptions were made to enable the refinements to proceed: all C-C distances were assumed to be equal, as were the C-H distances. The planes describing the H-C-H angles of the methylene groups were assumed to be the perpendicular bisectors of the X-C-C (X = C, N) valence angles, and the H-C-N and C-C-H angles were constrained to values previously obtained for triethylenediamine and bicyclo[2.2.2]octane.…”

Section: Introductionmentioning

confidence: 99%

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Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations

et al. 2007

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The structure of quinuclidine, HC(CH(2)CH(2))(3)N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (r(h1)) for the gaseous molecule. The structures of two adducts of quinuclidine with group 13 trihydride molecules, MH(3) (M=B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.

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Section: Ged Refinementssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations

et al. 2007

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“…Ab initio calculations of the geometry of the ground state of ABCO at the B3LYP/6-311G* level lead to the geometrical parameters reported in Table . The experimental structure of ABCO in the gas phase has been investigated by using rotational spectroscopy and electron diffraction . The results from the detailed microwave study of Hirota and Suenaga 36 are most consistent with the experimentally determined structure of the closely related diamine 1,4-diazabicyclo[2.2.2]octane (DABCO).…”

Section: Resultsmentioning

confidence: 58%

The Lowest Excited Singlet States of 1-Azaadamantane and 1-Azabicyclo[2.2.2]octane: Fluorescence Excitation Spectroscopy and Density Functional Calculations

et al. 1997

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The lowest excited singlet states of the structurally rigid amines 1-azaadamantane and 1-azabicyclo[2.2.2]octane have been investigated by using fluorescence excitation spectroscopy on samples seeded in supersonic expansions. Based upon the notion that in both species the lowest excited singlet state is a Rydberg state with the ground state of the radical cation as its ionic core, excitation spectra have been analyzed by employing density functional calculations of the equilibrium geometries and force fields of the ground state of the neutral species and its radical cation. A good agreement is obtained between experimentally observed and theoretically predicted frequencies and intensities of vibronic transitions. Subsequent refinements of the geometry of the lowest excited singlet state are shown to account adequately for the minor differences between experiment and the computational results obtained by using the radical cation as a model for the lowest excited singlet state. From our analysis it also becomes apparent that the excited state is in both molecules subject to vibronic coupling with higher-lying excited states, as exemplified by the presence of transitions to non-totally symmetric vibrational levels. The results of the present study enable the determination of mode-specific reorganization energies accompanying ionization of 1-azaadamantane, which are shown to correspond qualitatively well with those determined in resonance Raman studies on the charge transfer transition in the electron donor−acceptor system 1, which contains 1-azaadamantane as the electron donor unit.

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“…The MP2/BC calculations showed that the C 3 structure with a NCCC dihedral angle of 13.58 was more stable than the C 3v conformer by 0.17 kcal/mol, compared with the experimental value of 0.10 kcal/mol. 66 The MM4 calculations also show that this molecule has C 3 symmetry, with a NCCC torsion angle of 14.18.…”

Section: Quinuclidinementioning

confidence: 92%

“…The average CÀ ÀN and CÀ ÀC bond lengths for quinuclidine (1-azabicyclo[2.2.2]octane) were determined from electron diffraction studies 66 to be 1.469(3) and 1.552(2) Å (Supplementary Table S12). MM4 gives similar bond lengths, 1.467 and 1.553 Å .…”

Section: Quinuclidinementioning

confidence: 99%

Molecular mechanics (MM4) study of amines

et al. 2007

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The MM4 force field has been extended to include aliphatic amines. About 20 amines have been examined to obtain a set of useful molecular mechanics parameters for this class. The vibrational spectra of seven amines (172 frequencies) calculated by MM4 have an overall rms error of 27 cm(-1), compared with corresponding MM4 value of 24 cm(-1) for alkanes. The rms and signed average errors of the moments of inertia of nine simple amines compared with the experimental data were 0.18% and -0.004%, respectively. The heats of formation of 30 amines were also studied. The MM4 weighted standard deviation is 0.41 kcal/mol, compared with experiment. Electronegativity effects occur in the hydrocarbon portion of an amine from the nitrogen, and are accounted for by including electronegativity induced changes in bond lengths and angles, and induced dipole-dipole interactions in the molecule. Negative hyperconjugation results from the presence of the lone pair of electrons on nitrogen, and leads to the Bohlmann bands in the infrared, and also to strong and unusual geometric changes in the molecules (Bohlmann effect), all of which are fairly well accounted for. The conformational energies in amines appear to be less straightforward than those for most other classes of molecules, apparently because of the Bohlmann effect, and these are probably not yet completely understood. In general, the agreement between the MM4 calculated results and the available data is reasonably good.

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The structure of quinuclidine (1-azabicyclo(2.2.2.) octane) as determined by gas phase electron diffraction

Cited by 12 publications

References 8 publications

Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations

Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations

The Lowest Excited Singlet States of 1-Azaadamantane and 1-Azabicyclo[2.2.2]octane: Fluorescence Excitation Spectroscopy and Density Functional Calculations

Molecular mechanics (MM4) study of amines

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