Crystal structure and charge density of 4-methylpyridine (C6H7N) at 120 K

Ohms, U.; Guth, Hans P.; Treutmann, W.; Dannöhl, H.; Schweig, Armin; Heger, G.

doi:10.1063/1.449820

Cited by 33 publications

(18 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…angles, all other distances and angles were kept constant in the refinement processes ( Table 1). The calculated distances agree with those found in the parent compounds (Ü lkü et al, 1971;Chiang, 1974;Ohms et al, 1985;Vorontsov, 2002;Fillaux et al, 2003), with the N-O distance of 1.39 Å typical of a very limited -bond character (Ü lkü et al, 1971). The molecular thermal motions of the rigid body and of the satellite methyl group were refined by means of the appropriate molecular displacement tensors, the TLS matrices (Schomaker & Trueblood, 1968).…”

Section: Methodssupporting

confidence: 80%

Synchrotron and neutron diffraction study of 4-methylpyridine-N-oxide at low temperature

Damay¹,

Carretero-Genevrier²,

Cousson³

et al. 2006

Acta Crystallogr Sect B

View full text Add to dashboard Cite

The structure of 4-methylpyridine-N-oxide has been determined at 250, 100 and 10 K by combined synchrotron (C(6)H(7)NO) and neutron (C(6)D(7)NO) powder diffraction experiments. At 250 K the space group is I4(1)/amd and the tetragonal unit cell [a = b = 7.941 (2), c = 19.600 (5) A] contains eight equivalent molecules. At 100 K the structure is orthorhombic, with space group Fddd, a = 12.138 (2), b = 10.237 (2) and c = 19.568 (3) A. The 16 equivalent molecules are rotated by about 8 degrees around the c axis with respect to positions at high temperature. At 10 K the best structural model corresponds to a tetragonal unit cell with the space group P4(1), a = b = 15.410 (2) A and c = 19.680 (3) A. The 32 molecules (eight molecules in the asymmetric unit) show complex reorientations around the three cell axes. Whereas at 250 and 100 K the deuterated methyl groups are largely disordered, at 10 K they are ordered in-phase along infinite chains parallel to a and b. Face-to-face methyl groups along c are in an eclipsed configuration. The structure at 10 K suggests that the manifold of rotational tunnelling transitions could be due to inequivalent lattice sites for crystallographically independent methyl groups.

show abstract

Section: Methodssupporting

confidence: 80%

Synchrotron and neutron diffraction study of 4-methylpyridine-N-oxide at low temperature

Damay¹,

Carretero-Genevrier²,

Cousson³

et al. 2006

Acta Crystallogr Sect B

View full text Add to dashboard Cite

show abstract

“…2 and Tables I-IV͒. [13][14][15] All molecules are 13 paired methyl groups should be twisted by Ϯ60°with respect to each other and perform combined rotation. However, this is not consistent with the C 2 site symmetry.…”

Section: Crystal Structure: Experiments and Resultsmentioning

confidence: 99%

“…II͒. [13][14][15] The crystal symmetry discards coupling between equivalent chains parallel to either a or b axis. To the best of our knowledge, this structure is unique to observing collective quantum rotation in one dimension.…”

Section: Introductionmentioning

confidence: 99%

Collective rotational tunneling of methyl groups and quantum solitons in 4-methylpyridine: Neutron scattering studies of single crystals

et al. 2003

View full text Add to dashboard Cite

The structure of the 4-methylpyridine crystal has been determined at 10 and 260 K with the single-crystal neutron-diffraction technique. The space-group symmetries are I4 1 /a and I4 1 /amd, respectively. In both cases, there are eight molecular entities in the unit cell. The rotational axes of the methyl groups are aligned along the c axis. The shortest intermolecular distances occur between face-to-face methyl groups. The next shortest distances correspond to infinite chains of rotors parallel to the orthogonal axes a and b. The angular probability densities of the methyl groups are clear evidence of orientational disorder. The incoherent scattering function S(Q a ,Q b ,) has been measured with the inelastic neutron scattering technique at 1.7 K. The energytransfer ranges, បϭϮ(500Ϯ60)eV, encompass transitions due to rotational tunneling. The anisotropy in Q is distinctive of dynamics in one dimension. These are represented with the quantum sine-Gordon equation that is an approximation to the Hamiltonian for an infinite chain of coupled rotors. Spots of intensity observed for neutron-energy loss at ͉Q a ͉ or ͉Q b ͉Ϸ1.55 Å Ϫ1 are distinctive of stationary states for breathers. Weaker peaks at ͉Q a ͉ or ͉Q b ͉Ϸ1.0 Å Ϫ1 reveal collective tunneling. This is a thermally activated process arising from rather heavy pseudoparticles composed of large numbers ͑from 22 to 25͒ of kinks or antikinks. Quantization of the kinetic momentum arises from the chain discreteness and from conservation of the angular momentum. Traveling states are stationary when the kinetic energy is within the tunneling energy band. In the ground state, the chain dynamics are represented with a single collective angular coordinate. The incoherent scattering function for neutron-energy-gain reveals bound excited states with lifetimes of several days.

show abstract

“…Data at hand as discussed by Vorontsov et al [19] identify local configurations where two molecules adopt a T configuration that is having the molecular planes normal to each other, as able to explain such features as well as the presence of crossing (isosbestic) points in the density dependence of the atom-atom functions. In fact, such local configurations are found in the crystal structure of the positional isomer 4-methyl-pyridine [20,21] which shows at low temperatures a tetragonal I4 1 / a with eight molecules per unit cell having the rotational axis of the methyl groups aligned along the crystal c axis.…”

Section: A Liquid Structurementioning

confidence: 96%

Unconventional density dependence of the stochastic dynamics in an organic liquid

et al. 2004

View full text Add to dashboard Cite

The density dependence of the diffusive rotational and center-of-mass dynamics of 2-methyl-pyridine is investigated by means of the concurrent use of quasielastic neutron scattering and molecular dynamics simulations. The dependence of both translation and rotational diffusion coefficients shows a distinctive change of slope with increasing density taking place about rho=0.975 g/cm3. Such a change in the dynamics can be related to observations made in other liquids composed of oblate-spheroidal particles.

show abstract

Crystal structure and charge density of 4-methylpyridine (C6H7N) at 120 K

Cited by 33 publications

References 14 publications

Synchrotron and neutron diffraction study of 4-methylpyridine-N-oxide at low temperature

Synchrotron and neutron diffraction study of 4-methylpyridine-N-oxide at low temperature

Collective rotational tunneling of methyl groups and quantum solitons in 4-methylpyridine: Neutron scattering studies of single crystals

Unconventional density dependence of the stochastic dynamics in an organic liquid

Contact Info

Product

Resources

About