Deuterium Nuclear Quadrupole Coupling Constants Research Articles

Laboratory rotational spectrum of acrylic acid and its isotopologues in the 6–18.5 GHz and 52–74.4 GHz frequency ranges

In order to facilitate the detection of acrylic acid in space, for which a possible mechanism of formation is proposed, we extended the measurements of the rotational spectrum of this molecule to the 6–18.5GHz (time domain Fourier transform) and 52–74.4GHz (frequency domain) ranges in supersonic expansions. 77 new lines were assigned to the s-cis conformer and 83 new lines to the s-trans conformer. In addition, the rotational spectra of the three single 13C isotopologues have been measured in natural abundance for both conformers. High resolution measurements of the carboxylic deuterated isotopologues allowed for the determination of the deuterium nuclear quadrupole coupling constants. All the spectroscopic experimental parameters were compared to the ones obtained with quantum chemical methods at the MP2(fc)/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels of calculation.

Neutron powder diffraction, and solid-state deuterium NMR analyses of Yb 2RuD 6 and spectroscopic vibrational analysis of Yb 2RuD 6 and Yb 2RuH 6

The crystal structure of Yb 2RuD 6 has been determined by neutron powder diffraction and the results were consistent with the Fm3m (#225) space group, a=7.2352(18) Å, with the atoms arranged according to the well-known K 2PtCl 6 structure. No structural phase transition was observed in going from room temperature to 4 K. Raman spectra were not available due to fluorescence, but all fundamental bands and combination bands were assigned from FTIR and PAIR spectra only following previous studies for other alkaline earth and europium ruthenium ternary metal hydrides and deuterides. The deuterium nuclear quadrupole coupling constant, 40.9 kHz, leads to an ionic character of the Ru–D bond of 82%.

Microwave spectra of O2–HF and O2–DF: Hyperfine interactions and global fitting with infrared data

Spectra of the open shell complexes O(2)-HF and O(2)-DF were recorded using Fourier transform microwave spectroscopy. A complete analysis of the hyperfine structure and a global fit including microwave and infrared frequencies [W. M. Fawzy, C. M. Lovejoy, D. J. Nesbitt, and J. T. Hougen, J. Chem. Phys. 117, 693 (2002)] are reported. The Fermi contact interaction between the electron and nuclear spins, the electron spin-nuclear spin dipolar interaction, the nuclear spin-nuclear spin dipolar interaction, and the nuclear electric quadrupole interaction (for O(2)-DF) were considered in the analysis. The correspondence between the magnetic hyperfine constants and the two nuclei of the H(D)F is unambiguously established. In both O(2)-HF and O(2)-DF, the Fermi contact parameter is larger for the fluorine than for the hydrogen, while for the nuclear spin-electron spin dipolar hyperfine constants, the reverse is true. The effective angle between the HF bond and the a axis of the complex, determined from the nuclear spin-nuclear spin interaction constant, is 38(4) degrees. The same angle for the DF complex, derived from the deuterium nuclear quadrupole coupling constant, is 31(4) degrees.

Neutron powder diffraction and solid-state deuterium NMR studies of Ca 2RuD 6 and the stability of transition metal hexahydride salts

The crystal structure of Ca 2RuD 6 has been determined by neutron powder diffraction: space group Fm3 m, K 2PtCl 6 structure, as found for other hexahydride salts of group 8 metals with alkaline earth or lanthanide counter ions. No structural phase transition was observed between 340 K and 50 K. The deuterium nuclear quadrupole coupling constant, 54.7 kHz, leads to an ionic character of the Ru–D bond of 76%. The known trends in the behaviour of A 2MH 6 salts are interpreted in terms of the ionization energies of the cation and the central metal atom.

Structural and Torsional Properties of o-Cresol and o-Cresol-OD as Obtained from Microwave Spectroscopy and ab Initio Calculations

The microwave spectra of o-cresol and of o-cresol-OD were assigned using molecular beam Fourier transform microwave (MB-FTMW) spectrometers in the frequency range of 3–40 GHz. Two conformers of o-cresol were measured where the hydroxy group is syn with respect to the methyl group in one case and anti in the other. The transitions of both conformers were split due to internal rotation of the methyl group. For syn- o-cresol we found the rotational constants A=3249.45242(18) MHz, B=2202.02546(18) MHz, C=1323.66277(16) MHz, and the barrier to internal rotation of the methyl group V 3=7.912(46) kJ mol −1. In the case of anti- o-cresol A=3273.80084(18) MHz, B=2196.26747(18) MHz, C=1325.36424(22) MHz, and V 3=4.4256(14) kJ mol −1 was obtained. Moreover we were able to determine the quartic centrifugal distortion constants, the angle between the internal rotor axes, and the inertial a axes, and, for the deuterated species, additionally the deuterium nuclear quadrupole coupling constants.

Electron distribution and molecular motion in crystalline benzene: an accurate experimental study combining CCD X-ray data on C6H6 with multitemperature neutron-diffraction results on C6D6.

The electronic properties of the benzene molecule, for example its quadrupole moment and the electric field gradients (EFG's) at the H nuclei, are of fundamental importance in theoretical and experimental chemistry. With this in mind, single-crystal X-ray diffraction data on C(6)H(6) were collected with a charge-coupled device detector at T approximately 110 K. As accurate modelling of the thermal motion in the crystal was regarded as vital, especially for the hydrogen atoms, anisotropic-displacement parameters (ADP's) for the C and H atoms in C(6)H(6) were derived in a straightforward fashion from analysis of the temperature dependence of ADP's for the C and D atoms in C(6)D(6) at 15 K and 123 K obtained by neutron diffraction. Agreement between C-atom ADP's derived from thermal-motion analysis of neutron data and those obtained from multipole refinement by using the X-ray data is extraordinarily good; this gives confidence in the modelling of vibrational motion for the H atoms. The molecular quadrupole moment derived from the total charge density of the molecule in the crystal is (-29.7+/-2.4)x10(-40) C m(2), in excellent agreement with measurements made in the gas phase and in solution. The average deuterium nuclear quadrupole coupling constant (DQCC) derived from EFG tensors at H atoms is 182+/-17 kHz, also in excellent agreement with independent measurements. The strategy employed in this work may be of more general applicability for future accurate electron density studies.

The nuclear quadrupole coupling constants of methanol in mixtures with CCl4 by molecular dynamics and ab initio calculations

The deuterium nuclear quadrupole coupling constant (QCC) has recently been measured for the hydroxy-D in methanol-CCl4 mixtures of various compositions. The QCC which is strongly sensitive to the local environment of a molecule can also be calculated. For this purpose we have performed a series of molecular dynamics simulations (MD) of liquid mixtures of methanol and carbon tetrachloride and have extracted configurations small enough to perform ab initio calculations on them. Two sets of potentials, partly from the literature based on flexible molecules and partly from ab initio calculations, have been used in the simulations. The computed QCC-values are about 2–20 % higher than the experimental ones but show a similar decrease with increasing methanol mole fraction. The experimental finding of a maximum of the QCC at a methanol mole fraction 0.1 could, however, not be reproduced.

Trifluoroacetic Acid; r0 -Structure, Partial Substitution Structure and Deuterium Nuclear Quadrupole Coupling Studied by Molecular Beam Microwave Fourier Transform Spectroscopy and by ab initio Calculations

We report the assignment and analysis of all stable monosubstituted isotopomers of trifluoroacetic acid. The 13C and 18O isotopomers were observed in natural abundance. The rotational constants and quartic centrifugal constants are presented. The rotational constants are used to derive a partial substitution structure and a complete ro structure for future comparison with the corresponding values in hydrogen bridged bimolecules containing trifluoroacetic acid as a subunit. The deuterium nuclear quadrupole coupling constants are derived from the hfs-splittings of low-J rotational transitions of the CF3COOD isotopomer. The results of ab initio quantum chemical calculations are presented, which were carried out to assist in the assignment of the rotational spectra of the isotopomers and for comparison with the experimental molecular parameters.

B3LYP Calculation of Deuterium Quadrupole Coupling Constants in Molecules

The B3LYP/6-31G(df,3p) model for the calculation of deuterium nuclear quadrupole coupling constants (nqcc's) is shown to yield results as accurate as calculations previously performed at the MP4 level of theory. For 25 molecules, ranging from HD and DF to pyridine and fluorobenzene, the rms difference between the B3LYP nqcc's and the experimental nqcc's is 3.2 kHz (2.7%). For benzene, our calculations suggest that the experimental χbband χccof S. Jans-Bürli, M. Oldani, and A. Bauder, 1989.Mol. Phys.,68, 1111–1123) have been incorrectly assigned with respect to inertia axes and should be reversed. For borane carbonyl and nitric acid, it is shown that nqcc calculations using hydrogen bond lengths given by MP2/6-311 + G(d,p) optimizations in combination with the heavy atom experimental structures significantly improve agreement with the experimental nqcc's.

Microwave spectrum, structure, barrier to internal rotation, dipole moment, and deuterium quadupole coupling constants of the ethylene–sulfur dioxide complex

The microwave spectra of the complex between ethylene and sulfur dioxide and nine of its isotopic species have been observed in a Fourier transform microwave spectrometer. The spectra exhibit a and c dipole selection rules; transitions of the normal species and several of the isotopically substituted species occur as tunneling doublets. The complex has a stacked structure with Cs symmetry; the C2H4 and SO2 moieties both straddle the mirror plane with the C2 axis of SO2 crossed at 90 ° to the carbon–carbon bond axis (i.e., only the S atom lies in the symmetry plane). The distance between the centers of mass (Rcm) of C2H4 and SO2 is 3.504(1) Å and the deviation of their planes from perpendicular to Rcm is 21(2) ° and 12(2) °, respectively. The tunneling splittings arise from a rotation of the ethylene subunit in its molecular plane. The barrier to internal rotation is 30(2) cm−1. The dipole moment of the complex is 1.650(3)D. The deuterium nuclear quadrupole coupling constants for C2H3D⋅SO2 are χaa=−0.119(1) MHz, χbb=0.010(1) MHz, and χcc=0.109(1) MHz. The binding energy is estimated to be 490 cm−1 from the pseudo-diatomic approximation. A distributed multipole electrostatic model is explored to rationalize the structure and binding energies.

Deuterium Quadrupole Coupling Constants of Deuterohalogenoacetylens

Abstract Employing the high resolution of microwave Fourier transform spectroscopy, we investigated the lowest rotational transitions of fluoro-, bromo-, and iodoacetylene-d. Along with the rotational, centrifugal distortion, halogen nuclear quadrupole, and halogen spin-rotation coupling constants, we determined the deuterium quadrupole coupling constants of bromo-and iodoacetylene-d. For fluoroacetylene-d, we redetermined the deuterium nuclear quadrupole coupling constants with higher accuracy.

Nuclear quadrupole resonance of 14N and 2H in pyrimidines, purines, and their nucleosides

Using nuclear quadrupole double-resonance techniques, nitrogen-14 and deuterium nuclear quadrupole coupling constants and asymmetry parameters have been measured in uracil, 5-bromouracil, cytosine, adenine, xanthine, hypoxanthine, their nucleosides, 2-aminopyrimidine, and benzimidazole. Zeeman studies and the detection of the simultaneous transitions of neighboring nuclei allowed in many cases a complete assignment of the observed spectral lines to particular 14N and 2D sites.

Microwave and millimetre wave spectra of diazirine-d2: Rotational and hyperfine structure analysis and molecular structure

The rotational spectrum of diazirine-d2, [Formula: see text], has been recorded in the ranges 8–40 and 100–400 GHz. The hyperfine structure of the measured rotational lines has been analyzed. The analysis required the treatment of two pairs of equivalent nuclei, which is discussed in detail. The deduced deuterium nuclear-quadrupole coupling constants are[Formula: see text]The quadrupole coupling constants of the nitrogen nuclei[Formula: see text]are taken from the parent species, and the spin-rotation coupling constants are[Formula: see text]The rotational and centrifugal distortion constants have been obtained for the ground vibrational state from the analysis of the unperturbed line positions. The complete rs structure of diazirine has been determined using the rotational constants of all available isotopomers of diazirine. The internuclear distances are rs(C—N) = 148.13(24) pm, rs(C—H) = 108.03(29) pm, and rs(N—N) = 122.80(25) pm, and the bond angles are [Formula: see text] and [Formula: see text], with the HCH plane perpendicular to the NCN plane.

Deuterium nuclear quadrupole coupling constants in vibrationally excited C2HD: Evidence for electron reorganization

The l-doubling spectra of monodeuteroacetylene have been obtained in the ν4=1 (C–D bend) and ν5=1 (C–H bend) states of the molecule with resolution sufficient to determine the deuterium nuclear quadrupole coupling constants. The spectroscopic constants obtained from the J=1 rotational level are UFRULE2 ν4=1 ν5=1 UFRULE1 eqQDaa (kHz) 207.(6) 221.(2) eqQDbb−eqQD cc (kHz) −31.(22) −6.(4) CD (kHz) −6.(2) −1.5(3) CH (kHz) ⋅⋅⋅ −20.0(5) μ (D) 0.023 59(11) 0.056 24(3) q (MHz) 133.050 6(9) 105.699 3(1) UFRULE2 These results are interpreted in terms of the electron distribution surrounding the deuterium nucleus and are shown to be inconsistent with the assumption of a cylindrical distribution about the C–D bond axis in these states. This deviation from the symmetry appropriate for the molecule at equilibrium is shown to arise from a distortion in the cross section of the electron distribution that is unaccompanied by changes along the bond axis.

Deuterium nuclear quadrupole coupling in the hydrogen-bound systems ethylene—D 35CI and acetylene—D 35CI

The deuterium nuclear quadrupole coupling constants in the T-shaped π-complexes ethylene—D 35Cl and acetylene—D 35Cl have been measured to be x aa D = 171.1 (71) kHz for ethylene—DCl and x aa D = 146.3(35) kHz for acetylene—DCL. The values of x aa D differ from those expected from projecting the free DCl monomer values. Rotational and centrifugal distortion constants are obtained for acetylene—D 35Cl confirming the structure given previously for acetylene—HCl.

The rotational spectrum, H, 19F nuclear spin–nuclear spin coupling, D nuclear quadrupole coupling, and molecular geometry of a weakly bound dimer of carbon monoxide and hydrogen fluoride

A dimer formed between carbon monoxide and hydrogen fluoride has been detected and identified in the gas phase through its rotational spectrum by using a pulsed Fourier transform microwave spectrometer equipped with a pulsed nozzle source of the dimers and a Fabry-Perot cavity. Rotational constants B0, centrifugal distortion constants DJ, deuterium nuclear quadrupole coupling constants χD, and the nuclear spin–nuclear spin coupling constants SHF and SDF for the vibrational ground state of each of the five isotopic species investigated are as follows (the errors in B0 and DJ are discussed in the text): These spectroscopic constants have been interpreted in terms of a linear equilbrium geometry in which the atoms are in the order OC⋅⋅⋅HF and in which the weak binding is therefore through a hydrogen bond to the carbon atom. Various quantities characterizing the intermolecular interaction potential have also been estimated from the above constants and are used with those similarly determined to make comparison both within the series OC⋅⋅⋅HX (X = F, Cl, and Br) and among the different series B⋅⋅⋅HX (B = Ar, Kr, OC; X = F, Cl, and Br).

The molecular Zeeman effect in HCP, HCN, and HCCBr and a comparison with similar molecules

The molecular Zeeman effect has been observed in the J = 0 → 1 ΔM = 0, and ± 1 transitions in H12CP, D12CP, H12C15N, H12C12C79Br, and H12C12C81 Br giving the molecular g-values, magnetic susceptibility anisotropies, and corresponding molecular quadrupole moments. The results are g⊥(HCP) = −0.0430 ± 0.0010, g⊥(DCP) = −0.0353 ± 0.0010, x⊥ - x| = (8.4 ± 0.9) × 10−6 erg/G2 mole and Q|(HCP) = (4.4 ± 1.2) × 10−26 esu; g⊥(HC15N) = −0.0904 ± 0.0003, x⊥ - x| = (7.2 ± 0.4) × 10−6 erg/G2 mole, and Q|(HC15N) = (3.1 ± 0.6) × 10−26 esu; g⊥(HCC79Br) = −0.00395 ± 0.00032, g⊥(HCC81Br) = −0.00388 ± 0.00014, x⊥ - x| = (9.5 ± 0.9) × 10−6 erg/G2 mole, and Q| = (8.5 ± 1.1) × 10−26 esu. The results in HCN agree very well with an earlier prediction of the magnetic properties. The new results presented here are compared to other members in the acetylene and cyanide series of molecules and we conclude that the sign of the g-value in acetylene should be positive.The deuterium nuclear quadrupole coupling constant was also determined in DCP to be xD = 233 ± 40 kHz.

Deuterium Nuclear Quadrupole Interaction in FC≡CD, CH3C≡CD, and ClC≡CD

The deuterium nuclear quadrupole coupling constants of CH3–C≡C–D, Cl–C≡C–D, and F–C≡C–D have been determined in order to investigate the effect of substitution on the electron distribution in the C—D bond. The results along the C—D bond yield χD=208±10 kc/sec for CH3–C≡C–D, χD=212±10 kc/sec for F–C≡C–D, and χD=225±18 kc/sec for Cl–C≡C–D. The results show equal deuteron field gradients within experimental error and therefore show that the C—D bond is relatively insensitive to the substitution at the other end of the acetylenic bond.