35Cl Nuclear Quadrupole Resonance Frequencies Research Articles

A nuclear quadrupole resonance study of the solids 2,3,6-trichloroanisole, 2,4,6-trichloroanisole and p-chloroanisole

The temperature dependence of the 35Cl nuclear quadrupole resonance frequencies nu Q of the solids 2,3,6-trichloroanisole, 2,4,6-trichloroanisole and p-chloroanisole are reported. The experimental measurements are analysed by means of the Bayer-Kushida theory. It appears that only low-frequency lattice modes contribute to the temperature dependence of nu Q(T). A comprehensive study of the frequency data allows the authors qualitatively to identify the motion responsible for the electric field gradient averaging mechanism at the resonant sites. Additionally, an unreported phase was found in p-chloroanisole, which turns out to be that corresponding to the stable phase.

Crystal Structure and Nuclear Quadrupole Resonance. The Bond Length C — Cl and 35Cl NQR

AbstractThe intramolecular distances dC—Cl for chlorine bound to sp2 carbon and to sp3 carbon, respectively, and the 35Cl NQR frequencies assigned to the corresponding Cl atoms correlate quite well according to the theory: v(35Cl) ∼ (dC—Cl)−3. The relation is v(35Cl) = (4 ± 6) MHz + (166 ± 31) · 106 · (dC—Cl)−3 · MHz · pm3 for {sp2‐C}‐Cl and v(35Cl) = (21 ± 5) MHz + (101 ± 25) · 106 · (dC—Cl)−3 · MHz · pm3 for {sp3‐C}‐Cl. — The crystal structures and chemical bonds of 1 (4‐methyl‐4‐trichloromethyl‐2,5‐cyclohexadiene‐1‐one), 2 (2‐chloro‐4,5‐dimethyl‐4‐trichloromethyl‐2,5‐cyclohexadiene‐1‐one), 3 (4,5‐dichloro‐1‐phenyl‐pyridazine‐6‐one), and 4 (2,2,4,5‐tetrachloro‐cyclo‐pentene‐1,3‐dione) were studied by single crystal X‐ray diffraction and 35Cl nuclear quadrupole resonance (NQR). 1 crystallizes with the space group D152h‐Pbca, Z = 8. The lattice constants are a = 1206.0(3) pm, b = 1341.3(3) pm, and c = 1178.8(3) pm. 2 crystallizes monoclinic, space group C52h‐P21/c, Z = 4, a = 696.3(3) pm, b = 1404.0(5) pm, c = 1151.4(5) pm, and β = 100.23(1)°. 3 crystallizes in the orthorhombic space group D4h‐P212121, Z = 4, a = 4303(1) pm, b = 586.8(2) pm, and c = 390.5(1) pm. 4 crystallizes cubic, space group T4h‐Fd3, with 48 molecules in the unit cell, a = 2181.5(5) pm. The 35Cl NQR spectra were observed for the two 2,5‐cyclohexadiene‐1‐ones, 1 and 2 in the temperature range 77 < T/K < melting point. For 3, the 35Cl NQR spectra was determined at T = 77 K and T = 295 K. No phase transition has been found for the three compounds in the temperature range in which the 35Cl NQR spectroscopy was performed.

35Cl nuclear quadrupole resonance spectra of paradichlorobenzene as a guest molecule in clathrates formed by the werner complexes M (II)(L 4)X 2

The 35Cl nuclear quadrupole resonance (NQR) spectra of paradichlorobenzene included in the Werner complexes M (II) (L 4)X 2 (L=4-picoline, 4-ethylpyridine, 4-vinylpyridine or 4-acetylpyridine; M (II)=Mn, Fe, Co or Ni; X − =SCN − or SeCN −) are reported. In all these complexes only one 35Cl resonance is exhibited, thus showing that there is only one type of inclusion site and that the symmetry of the site preserves the equivalence of the two chlorine atoms in PDCB. The temperature dependence of the 35Cl NQR frequency provides a measure of the degree of mobility of the guest molecule and shows that this mobility increases in the order Ni> Co> Fe> Mn and in the order 4-vinylpyridine>4-ethylpyridine>4-methylpyridine. In general, a change of anion from SCN − to SeCN − also increases the guest mobility. An independent check on the space available to the guest molecule has been obtained by measuring the unit-cell dimensions for a number of these complexes.

Structural and motional study of pyridinium tetrahalogenoantimonates(III) by means of nuclear quadrupole resonance spectroscopy

The temperature dependences of 35Cl and 81Br nuclear quadrupole resonance (n.q.r.) frequencies, 35Cl nuclear quadrupolar spin–lattice relaxation time T1, and the 1H n.m.r. second moment were observed for [C5H5NH][SbCl4], [C5H5NH][SbBr4], and their N-deuteriated analogues. The β phase of the chloride exhibited a second-order transition at 232 K similar to the phase transition of the bromide at 253 K. The phase transition points of the deuteriated compounds are lower by ca. 4 K for the chloride and ca. 5 K for the bromide. A minimum in 35Cl T1 was observed at about 125 K for the chloride and its deuteriated compound. This minimum is responsible for the reorientation of the pyridinium cation.

A nuclear quadrupole resonance study of the solid 2,6-dichloroaniline

The temperature dependence of both the 35Cl nuclear quadrupole resonance (NQR) frequency nu Q, and the spin-lattice relaxation time, T1, of the solid 2,6-dichloroaniline are reported. Two resonance lines are observed in this compound. The data analysis shows that the 35Cl spin-lattice relaxation is probably due to the thermal activation of a motion, internal to the amino group, via quadrupolar coupling. The corresponding activation energy is 12.7 kcal mol-1. From Bayer's theory (1951) it appears that only low-frequency modes contribute to the temperature dependence of the 35Cl NQR frequency.

Effect of hydrostatic pressure on the structural phase transition in K2OsCl6:a35Cl nuclear quadrupole resonance

The 35Cl nuclear quadrupole resonance frequency is reported in K2OsCl6 at temperatures in the vicinity of the structural phase transition for three externally applied hydrostatic pressures. The phase-transition temperature, Tc, decreases linearly with pressure, and the pressure coefficient, (dTc/dP), is measured to be −(2.2 ± 0.3) × 10−2 K∙MPa−1. This value is compared with that measured for K2ReCl6 and is consistent with the prediction of a calculation based on a modified rigid-sphere model. Measurements of (∂v/∂P)T show precursor behaviour as Tc is approached from the high-temperature cubic phase.

Nuclear quadrupole resonance studies of hydrogen bonding in trans-dichlorobis(ethylenediamine)cobalt(III) diaquahydrogen chloride

The temperature dependences of the 59Co and ligand 35Cl nuclear quadrupole resonance frequencies were measured for trans-[CoCl 2(D 2NC 2H 4ND 2) 2][D 5O 2]Cl 2. The chlorine frequency at 294 K increased by 38.5 kHz over the frequency of the undeuterated complex and only a slight temperature dependence was observed. The increase in the cobalt quadrupole coupling constant over that of the undeuterated complex was 15 kHz at 344 K and reached 252 kHz at 77 K. A weakening of the hydrogen bonds on deuteration is consistent with the shift in the 35Cl NQR frequencies.

ChemInform Abstract: Temperature Dependence of 35Cl Nuclear Quadrupole Resonance Frequencies and Hydrogen Bonding in Some Metal(II) Hexachlorostannate(IV) Hexahydrates.

Chemischer InformationsdienstVolume 17, Issue 50 Physical Inorganic Chemistry ChemInform Abstract: Temperature Dependence of 35Cl Nuclear Quadrupole Resonance Frequencies and Hydrogen Bonding in Some Metal(II) Hexachlorostannate(IV) Hexahydrates. K. HORIUCHI, K. HORIUCHISearch for more papers by this authorA. SASANE, A. SASANESearch for more papers by this authorY. MORI, Y. MORISearch for more papers by this authorT. ASAJI, T. ASAJISearch for more papers by this authorD. NAKAMURA, D. NAKAMURASearch for more papers by this author K. HORIUCHI, K. HORIUCHISearch for more papers by this authorA. SASANE, A. SASANESearch for more papers by this authorY. MORI, Y. MORISearch for more papers by this authorT. ASAJI, T. ASAJISearch for more papers by this authorD. NAKAMURA, D. NAKAMURASearch for more papers by this author First published: December 16, 1986 https://doi.org/10.1002/chin.198650009Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue50December 16, 1986 RelatedInformation

Molecular Motion in GeCl4 as Studied by 35Cl Nuclear Quadrupole Resonance

Abstract Temperature dependence of 35Cl nuclear quadrupole resonance frequencies and quadrupole relaxation time was measured of GeCl4 in the metastable phase. Above 160 K, molecular reorientation is seen active; its activation energy is 63.5 kJ mol−1. This energy probably prevents GeCl4 from undergoing a rotational phase transition.

Temperature behaviour of35Cl NQR frequencies and spin-lattice relaxation in solid p-bromobenzene sulphony chloride

A semi-rigid molecule model is used to explain both the temperature dependence of the 35Cl nuclear quadrupole resonance (NQR) frequency nu Q(T) and the spin-lattice relaxation time T1(T) in p-bromobenzene sulphonyl chloride. This paper reports measurements of T1(T) over the temperature range 80 to 285K which reflect the appearance of thermally activated semi-external modes (SEM) of the SO2Cl group, giving a strong spin-lattice relaxation for temperatures greater than 160K. The measured temperature dependence of nu Q(T) is explained by assuming the existence of two thermally activated SEM.

Influence of semi-external molecular motions on35Cl NQR frequencies and relaxation in solid benzenesulphonyl chloride

Measurements of the temperature dependence of the 35Cl nuclear quadrupole resonance frequency, nu Q(T), in the gamma phase of benzenesulphonyl chloride and the spin-lattice relaxation time, T1(T), for the three crystalline phases of the same compound were used to study the influence of different crystalline structures on the triggering of semiexternal molecular modes. From a comparative analysis of the effects that the semi-external modes (SEM) have upon nu Q(T) and T1(T) it is possible to deduce that there is a weak influence of the crystalline structure on the triggering temperature of SEMs. Furthermore, some properties of molecular torsional and semi-external modes, for each crystalline structure of benzenesulphonyl chloride, are deduced.

Chlorine NQR in 3-amino-2-chloropyridine and 2-chloro-5-nitropyridine

Temperature dependence of 35Cl nuclear quadrupole resonance (NQR) frequencies has been studied in 3-amino-2-chloropyridine and 2-chloro-5-nitropyridine from 77 to 298 K. The data were analysed and the torsional frequencies regarding internal motions in the molecules evaluated in the above temperature range using Bayer's theory and Brown's method.

35Cl Nuclear quadrupole resonance spectra of 3(5)-aryl-5 (3)-chloro-1,2,4-triazole

The 35Cl nuclear quadrupole resonance (NQR) spectra of a number of 3(5)-aryl-5(3)-chloro-1,2,4-triazoles were studied. The energically most favorable tautomeric forms of the molecules were established, and a correlation between the 35Cl NQR frequencies and the σm and σ0 reaction constants of the substituents in the aromatic ring was found.

A chlorine-35 nuclear quadrupole resonance study of some nitrogen mustard compounds

A linear relationship has been established between the 35Cl nuclear quadrupole resonance frequency and the sum of the Hammet δ parameters for several aromatic nitrogen mustard compounds. This relationship is given by f q =1.024 ∑ i=1 n where f q is the quadrupole resonance frequency in megahertz, δ 1 is the Hammett δ parameter for the ith ring substituent, and n is the number of ring substituents. This implies that the effect of the substituents is additive. Also, the change in the 35Cl NQR frequency is characteristic for a given substituent in this class of compounds.

Study of the temperature dependence of chlorine-35 nuclear quadrupole resonance in ClF5

The 35Cl nuclear quadrupole resonance frequency νq has been studied as a function of temperature between 4.2 and 135 °K. No break is seen on either the νq(T) curve or its derivative in spite of a phase change observed in the fluorine NMR at 117 °K. The quadrupole coupling constant observed is discussed in terms of the occupancy of the 3p orbitals on chlorine as determined by molecular orbital calculations and compared to the value found by microwave spectroscopy. The temperature dependence of νq(T) is interpreted in the light of Bayer’s theory and a value of the lowest libration frequency is obtained (νl?30 cm−1) which is also found consistent with the value of the relaxation time, T1, of 35Cl nuclei.

Nuclear quadrupole resonance and stereochemistry. Part 4.—Chlorocyclopropanes

The 35Cl nuclear quadrupole resonance frequencies of 22 chlorocyclopropanes show that the frequencies of 1-chlorocyclopropanes are increased in a stereodependent manner by a further chlorine substituent in the 2-position, the difference between the shifts produced by cis or trans substituents being approximately 0.8 MHz. No such effect occurs for alkyl substituents.

ChemInform Abstract: NUCLEAR QUADRUPOLE RESONANCE STUDY OF PHASE TRANSITION IN TETRACHLORO‐P‐BENZOQUINONE (CHLORANIL)

The phase transition in chloranil crystal has been studied by measurements of the 35Cl nuclear quadrupole resonance frequency and the spin‐lattice relaxation time. The splitting of the resonance line in the low temperature phase was shown to behave as an order parameter of the phase transition. The experimental order parameter and the anomalous behavior of the transition probability (1/T1) near the transition point were interpreted satisfactorily in terms of the librational soft‐mode theory which assumes anharmonic coupling between molecular librational modes in the crystal.

Nuclear quadrupole resonance study of phase transition in tetrachloro-p -benzoquinone (chloranil)

The phase transition in chloranil crystal has been studied by measurements of the 35Cl nuclear quadrupole resonance frequency and the spin-lattice relaxation time. The splitting of the resonance line in the low temperature phase was shown to behave as an order parameter of the phase transition. The experimental order parameter and the anomalous behavior of the transition probability (1/T1) near the transition point were interpreted satisfactorily in terms of the librational soft-mode theory which assumes anharmonic coupling between molecular librational modes in the crystal.

Étude par résonance quadripolaire des composés du type p-ClC 6H 4MMe 3 (M = C, Si, Ge, Sn)

The 35Cl nuclear quadrupole resonance frequencies at 77°K of the series of compounds p-ClC 6H 4MMe 3 are reported (M = C, Si, Ge, Sn). The measurements are analysed in terms of the π character of the CCl bond. The closeness of the experimental values suggests similar structures for the CCl bond throughout the series.

Investigation of the Rotary Lattice Mode in R2PtCl6 Compounds. I. From Measurements of the 35Cl Nuclear Quadrupole Resonance Frequency

Measurements of the temperature and pressure variation of the 35Cl nuclear quadrupole resonance (NQR) frequency in Rb2PtCl6 and Cs2PtCl6 are reported. The resonance frequency is measured at atmospheric pressure for temperatures from 4 to 500 K and at four temperatures between 290 and 380 K for pressures to 5000 kg cm−2. Previously published data for K2PtCl6 are also included in the analysis. Static lattice NQR frequencies are deduced. The differences between the static lattice frequencies are compared with the calculations of Smith and Stoessiger. Thermal averaging of the electric field gradient at a chlorine site is assumed to be dominated by the Q3, Q4, Q5, and Q6 internal modes of the PtCl6 octahedra and by the rotary lattice mode. The rotary mode frequencies are deduced; they are of similar magnitude and increase in the same sequence as the frequencies deduced from infrared and Raman data. An analysis of the pressure dependence of the NQR frequencies leads to pressure coefficients for the rotary mode frequencies. The influence of the cage of R atoms surrounding a PtCl6 octahedron is shown to increase through the series K2PtCl6, Rb2PtCl6, Cs2PtCl6. Finally, a thermodynamic analysis of the NQR data is presented which shows the importance of taking specific volume effects into account.