Ab initio study of the hydrogen bond in [H3N-H...NH3]+

Merlet, Peter; Peyerimhoff, Sigrid D.; Buenker, Robert J.

doi:10.1021/ja00779a003

Cited by 73 publications

(22 citation statements)

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“…[27][28][29][30] According to the calculations by Scheiner, 29 using the 4-31G basis set within the Hartree-Fock formalism, one could expect the barrier to vanish at an NÁÁÁN distance of about 2.55 Å . Very similar conclusions can be drawn from the results by Merlet et al 28 and Delpuech et al 27 Although these results cannot be directly transferred to the present work, it seems that in the DMAN Á H cation there is a low barrier hydrogen bonding, and this barrier may be close to kT. Hence at low temperatures the zero point vibrational level is located below the barrier and two peaks of the wavefunction should exist, whereas at elevated temperatures this level can exceed the barrier top.…”

Section: Resultsmentioning

confidence: 99%

“…The energetic levels for such bridges were analysed by Merlet et al 28 From the analysis it follows that the four lowest levels, denoted 0, 1, 2 and 3 (corresponding to notation 0 , 0 À , 1 and 1 À ) depend strongly on the bridge length and barrier. In the case of a very low barrier the 0 →0 À transition is a few hundred cm À1 and the isotopic ratio can reach anomalously high values.…”

Section: Resultsmentioning

confidence: 99%

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Low-temperature (120 K) structure and vibrational spectrum of protonated proton sponge: the adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 4,5- dicyanoimidazole (DCI)

Grech

Malarski

Sawka‐Dobrowolska

et al. 1999

J. Phys. Org. Chem.

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Low-temperature (120 K) studies of the structure of the DMAN Á DCI adduct indicate that in symmetrical [NHN] hydrogen bridge of 2.571 (1) Å length (2.579(2) Å at room temperature) there is a disorder of the H-atom occupying two positions at nitrogen atoms with a distance of 0.94(3) Å . The comparison with the situation at room temperature seems to show a very low barrier for the proton transfer. The low-frequency vibrations with the participation of the whole N(CH 3 ) 2 groups observed in Raman and inelastic incoherent neutron scattering (IINS) spectra of about 100 cm À1 excited at room temperature cause the fundamental level of the protonic mode to penetrate or exceed the barrier. The bending CNC vibrations of about 500 cm À1 are strongly coupled with the protonic mode leading to Evans holes in the band ascribed to the 0 → 0 À transition. This hypothesis is consistent with the literature data relating to theoretical studies on H 3 NHNH 3 , which show that the barrier for the proton transfer disappears at the hydrogen bond length of about 2.55 Å .

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Low-temperature (120 K) structure and vibrational spectrum of protonated proton sponge: the adduct of 1,8-bis(dimethylamino)naphthalene (DMAN) with 4,5- dicyanoimidazole (DCI)

Grech

Malarski

Sawka‐Dobrowolska

et al. 1999

J. Phys. Org. Chem.

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“…Such a dual location for the proton is indeed predicted by ab initio calculation of the [NH 3 -H-NH 3 ] + complex, from which the existence of a double well potential for proton transfer is deduced. 22 Furthermore, a vibrational analysis prediction of this hypothetical species shows infraredactive vibrational mode absorptions at 668 cm -1 for the symmetric N⋅⋅⋅N stretching mode, and at 2798 and 1260 cm -1 for the vibrational anti-symmetric transfer. 22,23 Similar features are indeed observed in the IR vibrational spectra of [Q 2 H] + , where in the low frequency region a continuum threshold appears at 550 cm -1 .…”

Section: Thiourea-halogen Systemmentioning

confidence: 91%

“…22 Furthermore, a vibrational analysis prediction of this hypothetical species shows infraredactive vibrational mode absorptions at 668 cm -1 for the symmetric N⋅⋅⋅N stretching mode, and at 2798 and 1260 cm -1 for the vibrational anti-symmetric transfer. 22,23 Similar features are indeed observed in the IR vibrational spectra of [Q 2 H] + , where in the low frequency region a continuum threshold appears at 550 cm -1 . Another characteristic frequency at 2937 cm -1 has also been observed.…”

Section: Thiourea-halogen Systemmentioning

confidence: 91%

Conductivity Properties of Thiourea- And Urea-Halogen Inclusion Compounds With Diquinuclidinium Cation as Guest

Merchán

Lavayen

Jara

et al. 2008

J. Chil. Chem. Soc.

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Thiourea and urea can modify their typical host properties to form new ternary polymolecular anionic halogen hosts in which the diquinuclidinium cation is included. A comparative study of the proton conductivity properties of this kind of inclusion compounds is presented. The hexagonal binary inclusion compound [quinuclidine] Ionic conductivities of all the compounds in pellets, and of 2 and 3 in large single crystals were measured by electrochemical impedance spectroscopy (EIS). Anisotropic conductivity behaviour in crystals of adequate dimensions of 2 and 3 was detected. The conductivity values of 2 and 3 in the crystals were 2.19x10 -4 and 6.03x10 -6 (S/cm), respectively, in the assumed channel direction, and 2.42x10 -6 and 8.27x10 -9 (S/cm), respectively, in the perpendicular direction to the former, at 298 K. Conductivities at room temperature of the thiourea-halide derivatives in pellets show a changing behaviour from insulator (10 -11 S/cm) for 2, 3 and 4 measured in vacuum, to semiconductor (10 -7 -10 -8 S/cm) for the thiourea-halide derivative measured at atmospheric pressure. For the urea-halide system the highest conductivity value corresponds to derivative 7 (8.66x10-5 S/cm) at atmospheric pressure, and the lowest to derivative 5 (5.48x10 -7 S/cm) measured in vacuum. Comparisons considering structural aspects are also discussed.

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“…Symmetrical N-H-N bonds are uncommon, and an ab initio study (Merlet, Peyerimhoff & Buenker, 1972) of the simplest such system, (H3N)2H ÷, suggested that the central N-H-N unit would be symmetrical only for N... N distances of 2.44 A and below. This is very short and our own semi-empirical calculations, made using the MNDO approximation (Dewar & Thiel, 1977), suggest a rather longer distance, ca 2.52A; MNDO predicts a symmetric N-H-N fragment in the isolated (CH3CsH4N)2H ÷ cation, with an N...N distance of 2.54 A, in reasonable agreement with the solid-state value, 2.61 A, reported here.…”

mentioning

confidence: 99%