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A relation between the quadrupole coupling constant e2Qqzz and asymmetry parameter η has been found for a series of meta-substituted iodobenzene derivatives. The relationships e2Qqzz(η) for electrondonor and electron-acceptor substituents have the same form but different numerical values of parameters. The average time of full electron transfer via tunneling has been evaluated.

The dependence between quadrupole coupling constants and 59Co asymmetry parameters at 77 K was established in the series (π-C5H4X)Co[π-(3)-1,2-B9H8(8-Z)C2HY]. It was shown that a region of the dynamic Opic-Pryce effect can be determined for these compounds.

A coupling equation relating the quadrupole coupling constant (e2 Qq zz ) to the asymmetry parameter (η) of the electric field gradient for a series of cobaltocenium derivatives (59Co NQR) is derived. The estimates of the correlation times of “slow” modulations of electron motions by tunneling processes lie in the range from 10−12 to 10−14 s. This corresponds to the interval of the characteristic times of nuclear motions.

The 35Cl NQR frequencies of (Cl3C)3SiCl at 77 K are interrelated with the inverse spin-lattice relaxation times. This interrelation is in the general form described by a hyperbola equation. It is shown that the “crystal effect” can be resolved into long-and short-range environment contributions, and the 35Cl NQR frequency for the C-Cl bonds can be extrapolated to the gaseous state.

Solutions to secular equations for the spins 5/2, 7/2, and 9/2 were found. The results allowed the quadrupole interaction constant e2Qqzz and asymmetry parameter η to be calculated from experimental NQR frequencies. An equation for determining the dEi/dη value necessary in experiments with applied electric fields was obtained.

The parameters of the equation relating the quadrupole coupling constant (e 2 Qq zz ) to the asymmetry parameter (η) of 59Co in the series of compounds R1R2R3SnCo(CO)4 and in the series of reference compounds R1R2R3GeCo(CO)4 and [(π-C5H5-n Men)Co(CO)2]2 are determined. The mean correlation times are determined for the complete electron tunneling in the dispersion region of electron-nuclear motions (η0 ± Δη).

A coupling equation that relates 35Cl NQR frequencies to reciprocal times of spin-lattice relaxation, which allowed us to isolate the contributions to the NQR frequency with respect to short- and longrange orders of the neighborhood of a resonant chlorine atom, was found for three (C2H5)SiCl3 crystalline phases. The value of 35Cl NQR frequency for an isolated molecule was estimated. The changes in the intensity of local electric fields stipulated by the crystal field were determined.

Regularities of transmission of the effect of equatorial and axial substituents were established for a number of chlorine-containing organic compounds of pentatalent phosphorus using35Cl NQR spectra. The field constants of35Cl NQR frequencies of the chlorine atoms participating in the P−Cl bond were estimated for a series of tetrahedral phosphorus ions. The35Cl NQR frequencies of chlorine atoms in tetracoordinated ions of pentavalent phosphorus and in analogous isoelectronic silicon compounds are related by a linear dependence.

The behavior of 35Cl NQR spectra in Cl5M · OPCl3 complexes is affected by the nature of the metal center and the distortion of its surrounding geometry. In all cases considered, the 35Cl NQR frequencies in the OPCl3 fragment shift toward higher frequencies upon complex formation, whereas the frequencies of axial chlorine atoms in the Cl5M group in the phosphorus and antimony complexes lie below those for the equatorial atoms, and in the niobium and tantalum complexes, the frequencies of the axial atoms are higher than those of the equatorial ones.

The coordination of chlorobenzene to Cr(CO)3 and ClC6H5Cr+ fragments is shown to result in a considerable rise in the NQR frequency of chlorine atoms. The field constant in (chlorobenzene)chromium tricarbonyl was found to grow markedly, relative to pure chlorobenzene.

For the crystallographically Inequivalent positions of the bromine atoms in CBr4, there exists an equation that relates the frequencies v of 79Br NQR to their field constants α = dv/dEz. This equation can be used to determine the strength of the local electric fields.

The changes in strength of local electric fields at bromine atoms in the BrCH 2 R series of compounds have been determined from a hyperbolic equation of the relationship between the 79 Br NQR frequency and its derivative with respect to electric field strength. The full range of electron-acceptor and electron-donor substituents is shown to be described by the same equations with different parameters.

The field constant of the NQR frequency of a chlorine atom (35Cl) in a series of arsenic derivatives [R1R2R3AsCl]+M− was estimated from correlations. The field frequency is ∼41.5±3.5 Hz cm kV−1, which is nearly twice as much as that in analogous phosphorus compounds.

The full127I NQR spectra of a series of iodo-substituted phenols and phenylmercury phenoxides have been studied. The quadrupole coupling constants and asymmetry parameters have been determined. The character of the OH...Hal hydrogen bond has been found to depend on the nature of substituents in the ring. Correlation dependences of the asymmetry parameters on the sum of the substituents resonance constants have been found for both coordinated as well as for non-coordinated iodine atoms.

The 55 Mn and 187 Re NQR spectral parameters for cyclopentadienyl tricarbonyl complexes of these metals at 77 K are presented. An analytical dependence between e 2 Qq zz and η has been shown to exist. Such dependence may be associated with slow mutual electron-nuclear motions in these complexes.

Equations relating e 2 Qq zz to η have been obtained. The equations are based on 12 Sb and halogen NQR spectra of the series of complexes RNO 2 ·SbCl 5 , where R = Alk and p -XC 6 H 4 . The temperature dependence of the parameters of the equations has been studied.

35Cl and 121Sb NQR spectra of RCN · SbCl5 complexes with R = Et, n-Pr, i-Pr, n-Bu, n-C5H11 , Cl(CH2)2, C6H4CH2, Ph, Cl, Me, CCl3 were measured and /or refined at 77 K. Redistribution of the "transferred charge" in the SbCl5 fragment of the complexes under study was investigated. The existence of a specific region of dispersion of the electron-nuclear motions (DENM) in RCN · SbCl5 complexes was established.

Local magnetic fields, experimentally determined in the oxides of nontransitional elements of group V, are related by exponential dependence to the atomic number of the central atom.

Complete 121,123Sb NQR spectra of crystalline rate earth antimonites Ln3Sb5O12 (Ln = La, Nd, Er, Lu) were recorded at 77 K. The quadrupole coupling constants and asymmetry parameters of the electric field gradient were measured. A “lanthanide compression” effect on the antimony NQR was observed. Using relations found for the antimonites under study, the Sb spectral parameters of other lanthanide compounds can be predicted.

The 35Cl and 79,81Br NQR spectra of (C5H5)2M Hal2 (M = Ti, Mo, W, Zr, Hf; Hal = Cl, Br) are similar. They are quadruplets with splittings ranging from 2 to 7%. The averaged frequencies of chlorine and bromine are related by a linear dependence. The temperature dependence of 81Br in Cp2HfBr2 (in the range of 77 ≑ 224 K.) is of conventional character with frequencies slowly changing with temperature; phase transitions have not been observed.

An equation relating 35Cl NQR frequencies toinverse spin-lattice relaxation times was found for HGeCl3 crystalline phases. The equation was used to identify shortand long-range order contributions to the NQR frequency in the environment of the resonance chlorine atom. Changes in the strength of local electric fields caused by the crystal field were determined.

We have studied the complete127I spectra and obtained the values of the quadrupole coupling constants e2Qqzz and the asymmetry parameters η in a series of substituted α-iodothiophenes. Using an additive scheme, we have calculated e2Qqzz and determined the substituent increments.

A dependence between the quadrupole coupling constants (e2Qqzz) and the asymmetry parameters of the electric field gradient (η) for the antimony atoms in the complex [SbF5]2− anions of M2SbF5 pentafluoroantimonites (M=Na, K, Rb, Cs, NH4, Ti, and Et2NH2) was revealed from the123Sb NQR spectra at 77 K.

The magnitude and direction of the local magnetic field strength ( H loc ) at the atomic nuclei of the resonant atom ( 121 Sb and 123 Sb NQR in senarmonite, Sb 2 O 3 ) for the ( 1 2 – 3 2 ) transition has been determined using spin-echo ‘beats’. We suggest criteria which permit the differentiation of the effect of spin-spin interactions from the H loc effect.

Nuclear quadrupole resonance (NQR) allows evaluation of small modifications of electron density on resonant atoms in different molecules. NQR study at 77 K shows that CF 2 BrCF 2 Br does not form any charge-transfer complexes with DMSO, PhCOMe and Me 2 CO: 79 Br NQR frequencies (ν Br ) are 306.40, 306.62, 306.50 and 306.42 MHz respectively. The insertion of an electron- withdrawing CF 3 -group onto alkyl bromide molecules CF 3 (CH 2 ) n Br ( I , n =1,2,3) leads to increasing ν Br values and consequently to decreasing electron density on the bromine. Lengthening of the hydrocarbon chain between the CF 3 and Br in I lowers the ν Br value from 289.10 ( n =1) to 267.77 ( n =2) and 256.36 ( n =3) MHz. Important information may be received from NQR reduced frequencies U p =ν obs /ν at , where ν obs is the observed halogen NQR frequency and ν at is the uncharged halogen NQR frequency in the X 2 molecule. The sign of the value of U p −1 corresponds to the sign of the total charge on the halogen atom in the molecule. The data in the table show that negative charges on Cl and Br remain in primary, secondary and tertiary perfluoroalkyl derivatives. Only iodine in tertiary perfluoroalkyl iodides may be charged positively. U p −1 U p −1 U p −1 CF 3 Cl −0.306 CF 3 Br −0.215 CF 3 I −0.098 (CF 3 ) 2 CFCl −0.249 (CF 3 ) 2 CFI −0.046 (CF 3 ) 3 CCl −0.224 (NO 2 ) 3 CCl −0.217 (NO 2 ) 3 CBr −0.066 (NO 2 ) 3 CI +0.145 Cl 2 0 Br 2 0 I 2 0 FCl +0.288 ICl +0.329 These results bring into question the reported mechanism of ‘halogenophilic’ reactions which consist of nucleophilic attack on positively charged halogen atoms.

1. The intramolecular contribution to the splitting of the NQR frequencies in the 2,6-dihalo-4-X-derivatives of phenol has been separated out. The strength of the intramolecular hydrogen bond is substantially dependent on the nature of the substituants in position 4. The splittings in the NQR spectra are reduced upon passing from electron-accepting substituents to electron-donating substituents. 2. The intramolecular coordination interactions of mercury atoms with halogen atoms leads to a reduction and splitting of the NQR frequencies of the halogen atoms in positions 2 and 6 and they are only slightly dependent on the substituent in position 4.

A theoretical description of the shape of the spin—echo envelope obtained upon applying a pulsed external electric field to a powder specimen is given. The existence of the maximum shift direction for a quadrupole system has been established theoretically and shown experimentally. A new pulsed technique for studying the electric effects in nuclear quadrupole resonance (NQR) is proposed.

On montre comment la spectroscopie de resonance quadripole nucleaire du chlore 35 peut contribuer a la determination de la structure du polychloral

The microstructures of some chloroprene rubbers, chloroprene-styrene copolymer and chloroprene-dichlorobutadiene copolymer, have been examined by nuclear quadrupole resonance (NQR). Molecular motions in the chloroprene rubber “nairit NP” have also been studied by NQR. It is shown that above 150 K the temperature-dependence of NQR frequencies differs for oriented and non-oriented samples. Molecular motions during unfreezing processes in the temperature range of polymer brittleness are manifested in NQR spectra by decrease of the frequency temperature coefficient.

It has been found that, when low temperature polyesterification is carried out, favourable conditions are created for the realization of block sequences of particular isomeric forms of the o , o ′-disubstituted bisphenol residue. The nature of the reaction medium and of the tertiary amine considerably affect the number and quantitative ratio of the signals in the NQR-Cl 35 spectrum of the polyarylate formed from dichlordiane and terephthalic acid. The presence of stable rotational isomers in polyarylate macromolecules considerably affects their physical and chemical properties.

The temperature dependence of the position and relative integrated intensities of the I127 NQR spectrum line of KIO3 (±1/2⟷ ±3/2) has been investigated from 4.2 to 370 K. The behaviour of the NQR spectrum line half-widths was studied over the same temperature range. It is shown that below 65 K the structure of KIO3 is statically ordered. In the temperature range 65 to 114 K the number of nonequivalent positions of iodine atoms in the KIO3 structure varies. Above 114 K the symmetry of IO ions and their nearest neighbours varies with no change in the symmetry of the crystal as a whole. At 342 K an abrupt disappearance of multiplicity in the NQR spectrum is found, which agrees with an anomaly of the dielectrie constant of KIO3 at 345.5 K and an abrupt jump of the spontaneous ferroelectrie polarization of the KIO3 crystal at 344 K. The values of the reorientation barriers of IO ion librational vibrations are estimated. [Russian Text Ignored.]

1. For a series of iodonium compounds of the Ar2IX type, it has been found that the127I NQR parameters — the quadrupole coupling constant e2Qqzz, the asymmetry parameter η, and the frequency field constant ϖv/ϖEz -vary regularly with the nature of the cation and the character of substitution in the ring. 2. Strengthening of the coordination interactions leads to a sharp jump in the frequency field constant ∂v/∂Ez and a significant change in the asymmetry parameter η. 3. For this series of compounds, a linear, correlation has been established between the values of e2Qqzz and η.

1. The NQR185Re,187Re,55Mn, and127I spectra of a number of derivatives of manganese and rhenium cyclopentadienyltricarbonyls were investigated. 2. The change in the quadrupole coupling constant on the metal atom is due to a greater degree to conjugation characteristics of the substituents than to induction characteristics; moreover, in rhenium derivatives this sensitivity is approximately an order of magnitude higher than in manganese derivatives. 3. The higher NQR127I frequencies in (CO)3ReC5H4I than in (CO)3MnC6H4I permit us to consider the (CO3)ReC5H4— group as a stronger electron acceptor than (CO)3MnC5H4-.

A study has been made of the NQR frequency field constants for the chlorine, bromine, and iodine atoms. It has been shown that the degree to which the field constants are characteristic decreases in the series Cl-Br-I.

A study has been made of molecular motion in oriented and nonoriented specimens of chloroprene rubber by methods of nuclear quadrupole resonance and radiothermoluminescence, as well as by a dynamic mechanical method using a torsion pendulum. The ductile-to-brittle transition and glass transition temperatures have been determined. The influence of orientation on molecular motion in a polymer in the forced elastic state is revealed. The radiothermoluminescence intensity differs for the oriented and nonoriented specimens.

35 Cl NQR spectra of pentafluorophenylchloromethanes C 6 F 5 CH(R)Cl (R = H, CH 3 , Cl, COOC 2 H 5 , C 6 F 5 ) have been studied to obtain information on the electronic influence of the C 6 F 5 group. On the basis of the data thus obtained and literature data, the electronic influence of the C 6 F 5 group is discussed.

Conformation de polyarylate regulier obtenu par polyesterification de chlorure de teraphtaloyle par des bis-phenols substitues

NQR spectra of 35 Cl, 79 Br, 93 Nb and 181 Ta in the series of niobium and tantalum pentahalides have been studied. There has been made a correlation between the carefully studied spectra and X-ray data. It has been shown that NQR spectra of TaBr 5 , TaCl 5 and NbF 5 entirely correspond to their crystal structures. The nature of the chemical bond in the dimeric molecules of M 2 Hal 10 has been discussed.

NQR spectra of 35 Cl, 81 Br and 127 I in cyclopentadienyltitanium halides Cp n TiHal 4- n have been studied. Quadrupole coupling constants of the halogen atoms regularly increase with the increasing number of Cp rings in the molecule, which is apparently connected with the decreasing multiplicity of the TiHal bond. A sharp increase in the asymmetry parameters of the iodine atom on introduction of the Cp rings is evidence for an essential desymmetrization of the electron density in the molecule caused by this operation.

1. The NQR spectra of Cl35 in etherates of di-, tri-, and tetrachlorides of elements of group IVB were studied. 2. Trichlorogermane etherate 2(C2H5)2O·HGeCl3 (just like the etherate oftetrachlorostannane 2(C2H5)2O ·SnCl4) has a donor-acceptor nature and is characterized by a change in the coordination number of the central atom, nonequivalence of the chlorine atoms, and an increase in the degree of ionic character of the Ge-Cl(Sn-Cl) bonds.

1. Four types of telomer homologs, corresponding to cleavage of the C-H and C-Cl bonds in the telogen during chain transfer and the formation of the radicals ĊCl3- and ĊHCl2-, carrying the kinetic chain, were identified in the products of radical telomerization of propylene with CHCl3 by the methods of gas-liquid chromatography, mass, IR, NQR, and PMR spectroscopy. 2. The addition of the radicals CCl3[CH2CH(ĊH3)]n with n≥2to propylene proceeds with some stereoregularity and obeys close stereochemical principles with chain transfer by these radicals to CCl4.

The mutual effect of atomic groups in acid chlorides of threeand four-coordination phosphorus was investigated by the nuclear quadrupole resonance of Cl35 (NQR Cl35) and Raman spectroscopy methods. On the basis of the NQR data it is suggested that in the ground state the interaction of unshared pairs of chlorine with the d orbitals of phosphorus is displayed weakly and the interaction of the indicated atoms is accomplished predominantly by an inductive mechanism. The integral intensities of the Raman lines of vibrations of the P-Cl and P=Cl bonds were measured. The Raman scattering data and the results of quantummechanical calculations by the molecular orbital method indicate some additional multiplicity of the P-Cl bond.

Two linear relationships exist between the nuclear quadrupole resonance frequencies of Cl35 in dichlorides of certain phosphorus acids and the σφ constants of substituents at the phosphorus atom; one of them is formed by alkyldichlorophosphonates, while the other is given by compounds in which conjugation is possible between the substituent and the d-orbitals of phosphorus-alkyldichlorophosphates, aryl- and vinyldichlorophosphonates.

F19 NMR chemical shifts δF are reported for fluoronitroalkanes, which are found to show a nearly linear relation to the NQR shifts δ for the chlorine and bromine analogs. The spin-spin coupling constant JF-N also indicates that the Hal-C-N angles vary little in the series HalnC(NO2)4-n. The empirical relation can be used to predict the properties of new halonitromethanes. The observed trends in δF and δCl when H is replaced by X (with X=Cl, F, or NO2) for the halonitromethanes indicate the sequence NO2, F, Cl as regards shift δF towards weaker fields, but the sequence F, Cl, NO2 as regards shift δCl towards higher NQR frequencies. The deviations from a linear relation for mixed halonitromethanes containing electron-donor groups indicate either that the distortion of the tetrahedral angle varies with the halogen or that conjugation effects for F19 NMR are different from those for Cl35 and Br79 NQR.