2H NMR Study on Phase Transitions and Crystal Dynamics of p-Chloro- and p-Bromobenzyl Alcohols

2002 ◽  
Vol 57 (6-7) ◽  
pp. 388-394 ◽  
Author(s):  
Motohiro Mizuno ◽  
Masanori Hamada ◽  
Tomonori Ida ◽  
Masahiko Suhara ◽  
Masao Hashimoto
Keyword(s):  
Relaxation Time ◽  
Phase Transitions ◽  
Nmr Spectra ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Hydrogen Atoms ◽  
Potential Wells ◽  
H Nmr ◽  
Nmr Study ◽  
Crystal Dynamics

Two phase transitions of 4-chlorobenzyl alcohol (pCBA) and 4-bromobenzyl alcohol (pBBA), from the low-temperature phase (LTP) to the intermediate-temperature phase (ITP) and from ITP to the room-temperature phase (RTP), were investigated by 2H NMR and differential scanning calorimetry (DSC). The crystal dynamics in each phase were studied using the 2H NMR spectra, the spin-lattice relaxation time (T1) and the relaxation time of quadrupole order (T1Q) for the samples, where the hydrogen of the -OH group was selectively deutrated. The 2H NMR 1 of both crystals in the RTP were dominated by the fluctuation of the electric field gradient at 2H nucleus caused by vibrational motions of the -CH2OH group. In the LTP of both crystals, the fast jump of hydrogen atoms between the two sites corresponding approximately to the positions of the hydroxyl hydrogen atoms in the RTP and LTP were found from 2H NMR spectra. The results of T1 and T1Q in the LTP revealed that the jump of hydrogen atoms occurs in asymmetric potential wells and that these potential wells gradually approach symmetric ones with increasing temperature on the high-temperature side in the LTP

Nuclear magnetic resonance studies of the methylammonium hexahalotellurates

1992 ◽  
Vol 70 (3) ◽  
pp. 849-855 ◽  
Author(s):  
Mark R. MacIntosh ◽  
Marco L. H. Gruwel ◽  
Katherine N. Robertson ◽  
Roderick E. Wasylishen
Keyword(s):  
Line Shape ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Solid Phase ◽  
Variable Temperature ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
H Nmr ◽  
Nmr Study ◽  
Correlated Motion

A 2H and 14N NMR study of the solid methylammonium hexahalotellurates, (MA)2TeX6 (MA = CH3ND3+ or CD3NH3+, X = Cl, Br, and I), has been undertaken to characterize the dynamics of the methylammonium (MA) ion as a function of temperature. At room temperature, the MA ion in the hexachlorotellurate (solid II) is confined to C3 jumps about the C—N axis while a small angle libration of the C—N axis is occurring. In the room temperature phase, solid I, of (MA)2TeBr6 and (MA)2TeI6 the MA ions are performing overall reorientations on the ps time scale, averaging the 2H nuclear quadrupolar interactions to zero. Variable temperature 2H NMR spin-lattice relaxation times, T1, indicate an activation energy, EA, for "isotropic" reorientations of the CH3ND3+ ion of 5.2 ± 0.5 and 2.6 ± 0.3 kJ mol−1 for X = Br and I, respectively. Deuterium T1 values for C-deuterated MA ion in the hexaiodotellurate indicate an EA for whole-ion reorientation of 3.1 ± 0.3 kJ mol−1. At any given temperature, the correlation time, τc, derived from the T1 results was found to be the same for the two deuterium-labelled hexaiodotellurates. The similarity of both the EA and the τc values implies correlated motion of the methyl and ammonium groups. The 14N T1 results for solid I of (MA)2TeI6 indicate that C—N axis motions, with an EA = 5.6 ± 0.6 kJ mol−1, are more hindered than N—D or C—D bond dynamics. The 2H NMR spectra for (MA)2TeI6 (solid II) and (MA)2TeBr6 (solids II, III, and IV) are characterized by a Pake doublet line shape. The measured peak-to-peak splittings are less than what is predicted by C3 motion about the molecular symmetry axis. It is possible to model these line shapes by postulating that C3 rotations of the methyl and ammonium groups occur as the C—N axis librates in an effective cone about the position of the static molecular axis. For (CH3ND3)2TeBr6 and (CD3NH3)3TeBr6 the peak-to-peak splittings in the 2H NMR spectra were measured as a function of temperature in solid phases II, III, and IV and were found to be similar. Finally, the 2H NMR line shape relaxation for (MA)2TeBr6 (solid III) displays an orientation dependence indicating that rotations about the C—N axis are discrete rather than diffusive in nature. For solid phase II of (MA)2TeCl6, the line shape is observed to relax isotropically, implying that continuous C3 rotations are taking place. Keywords: 2H and 14N NMR, methylammonium hexahalotellurates, molecular motion.

Incommensurability and Domain Structure of K2SbF5

2002 ◽  
Vol 57 (6-7) ◽  
pp. 456-460
Author(s):  
A. M. Panich ◽  
L. A. Zemnukhova ◽  
R. L. Davidovich
Keyword(s):  
Relaxation Time ◽  
Phase Transitions ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Spin Lattice ◽  
Relaxation Measurements ◽  
Increasing Temperature

Phase transitions and incommensurability in K2SbF5 have been studied by means of 123Sb NQR spectra and spin-lattice relaxation measurements. The phase transitions occur at 117, 135 and 260 K. The line shape and temperature dependence of the spin-lattice relaxation time T1 at 135 to 260 K are characteristic for an incommensurate state with a plane wave modulation regime. At 117 to 135 K a distinct fine structure of the NQR spectra has been observed. The X-ray diffraction pattern of this phase is interpreted as a coexistence of two modulation waves along the a and b axis with wave vectors (a*/6 + b*/6) and (a*/2 + b*/2), respectively. The best interpretation that fits our NQR data is a coexistence of two domains, the structures of which are modulated with different periods in such a manner that each domain exhibits only one of the aforementioned modulation waves. Redistribution of line intensities with the variation of temperature shows that one of the domains becomes energetically preferable on cooling and is transformed into the low temperature phase at 117 K. The 123SbNQR measurements in K2SbF5 show unusually short values of T1, which become close to the spin-spin relaxation time T2 with increasing temperature. - Pacs: 61.44.Fw, 64.60, 64.70, 64.70.Rh, 76.60

NMR · NQR and DTA · DSC Studies of Phase Transitions in Pyridinium Tetrachloropalladate(II) and Pyridinium Tetrachloroplatinate(II)

1998 ◽  
Vol 53 (6-7) ◽  
pp. 419-426 ◽  
Author(s):  
Tetsuo Asaji ◽  
Keizo Horiuchi ◽  
Takehiko Chiba ◽  
Takashige Shimizu ◽  
Ryuichi Ikeda
Keyword(s):  
Phase Transitions ◽  
Low Temperatures ◽  
Structural Phase ◽  
Orientational Order ◽  
Second Order ◽  
Order Transition ◽  
Spin Lattice Relaxation ◽  
Potential Wells ◽  
H Nmr ◽  
Second Order Transition

Abstract From the measurements of DTA • DSC and the temperature dependences of 35Cl NQR frequencies, phase transitions were detected at 150 K, 168 K, and 172 K for (pyH)2 [PtCl4], and at 241 K for (PyH)2 [PdCl4]. In order to elucidate the motional state of the constituent ions in the crystals in connection with the structural phase transitions, the 35Cl NQR and 1H NMR spin-lattice relaxation times and the second moment of the 1H NMR line were measured as functions of temperature. For both compounds, the potential wells for the cationic reorientation are suggested to be highly nonequivalent at low temperatures. Above 168 K, the pyridinium ions in (pyH)2[PtCl4] are expected to reorient between almost equivalent potential wells. As for (pyH)2[PdCl4], it is expected that the orientational order of the cation still remains even above the second order transition at 241 K. A change of the potential curve from two-unequal to three-unequal wells is proposed as a possible mechanism of the second order transition. The activation energies for the cationic motion in the respective model potential are derived for both compounds at high and low temperatures.

H NMR Study of Ionic Motions in High Temperature Solid Phases of (CH3NH3)2ZnCl4

2000 ◽  
Vol 55 (3-4) ◽  
pp. 412-414 ◽  
Author(s):  
Hiroyuki Ishida
Keyword(s):  
Activation Energy ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

Abstract The reorientation of the tetrahedral complex anion ZnCl42- and the self-diffusion of the cation in (CH3NH3)2ZnCl4 were studied by 1H NMR spin-lattice relaxation time (1H T1) experiments. In the second highest-temperature phase, the temperature dependence of 1H T1 observed at 8.5 MHz could be explained by a magnetic dipolar-electric quadrupolar cross relaxation between 1H and chlorine nuclei, and the activation energy of the anion motion was determined to be 105 kJ mol -1 . In the highest-temperature phase, the activation energy of the self-diffusion of the cation was determined to be 58 kJ mol -1 from the temperature and frequency dependence of 1H T1

NMR Study of Cation Motions in Ferroic [C(NH2)3]3Bi2Br9

2000 ◽  
Vol 55 (6-7) ◽  
pp. 570-574 ◽  
Author(s):  
M. Grottel ◽  
Z. Paja̡ka ◽  
R. Jakubasb
Keyword(s):  
Relaxation Time ◽  
Phase Transitions ◽  
Wide Temperature Range ◽  
Proton Nmr ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Potential Barriers ◽  
Spin Lattice ◽  
Nmr Study

The proton NMR second moment and spin-lattice relaxation time of polycrystalline [C(NH2)3]3Bi2Br9 were studied in a wide-temperature range. Dynamical inequivalence of two crystallographically different guanidinium cations has been revealed . The C3 reorientation of the two types of cations was found to be hindered by different potential barriers (25.1 kJ/mol and 34.7 kJ/mol). At higher temperatures an overall reorientation of the cations was revealed. The existence and order-disorder character of the phase transitions at 333, 350, 415, and 425 K have been confirmed.

Structural Phase Transitions and Cationic Motions in Pvridinium Dichloroiodate(I) as Studied by 1H NMR, Differential Thermal Analysis, and Powder X-Ray Diffraction

1989 ◽  
Vol 44 (11) ◽  
pp. 1111-1115 ◽  
Author(s):  
Reiko Watanabe ◽  
Tetsuo Asaji ◽  
Yoshihiro Furukawa ◽  
Daiyu Nakamura ◽  
Ryuichi Ikeda
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Phase Transitions ◽  
Room Temperature ◽  
Structural Phase ◽  
Spin Lattice Relaxation ◽  
Growth Time ◽  
Stable Phase ◽  
Temperature Phase ◽  
H Nmr

For crystals of pyridinium dichloroiodate (I), (pyH)ICl2, the temperature dependences of the 1H NMR spin-lattice relaxation time T1 and the 1H second moment M2 were determined. M2 was found to be small (~ 1 G2) above room temperature, indicating that the cations perform rapid reorientational motion about their pseudohexad axis perpendicular to the cationic plane. 1H T1 at its minimum was unusually long, indicating this motion occurring in the low symmetry local environments. Phase transitions between stable solid phases were revealed at 282 and 373 K by the 1H NMR measurements and differential thermal analysis. The highest-temperature phase was easily supercooled and transformed reversibly into another metastable phase and back on cooling and warming at almost the same temperature of 138 K. The kinetics of the phase transition from the supercooled to the stable phase at room temperature was analyzed using an Avrami type relation. The growth time of the stable phase was estimated to be about 14 h at room temperature

An 1H NMR Study on the Cationic Motion in Solid tert-Butylammonium Chloride and Bromide

1991 ◽  
Vol 46 (3) ◽  
pp. 265-268 ◽  
Author(s):  
Hiroyuki Ishida ◽  
Syuichi Inada ◽  
Naomi Hayama ◽  
Daiyu Nakamura ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Time ◽  
1H Nmr ◽  
Room Temperature ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
X Ray ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

AbstractThe 1H spin-lattice relaxation time (T1) in solid (CD3)3CNH3Cl and (CD3)3CNH3Br was measured above room temperature and the motional parameters for the reorientation of the NH3+ groups were determined. The 1H NMR absorptions measured in the same temperature range for (CH3)3CNH3Cl and (CH3)3CNH3Br indicate the presence of superimposed several cationic motions commonly taking place in both compounds. From X-ray powder patterns taken at room temperature, the bromide was found to be isomorphous with the chloride

A Proton NMR Study of n-Decylammonium Chain Dynamics in the Perovskite-type Layered Compound (C10H21NH3)2CdCl4

1993 ◽  
Vol 48 (4) ◽  
pp. 563-569 ◽  
Author(s):  
Stefan Jurga ◽  
Kazimierz Jurga ◽  
Eduard C. Reynhardt ◽  
Piotr Katowski
Keyword(s):  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
High Temperature Phase ◽  
Spin Lattice Relaxation ◽  
Layered Compound ◽  
Temperature Phase ◽  
Potential Wells ◽  
Spin Lattice ◽  
Compound C ◽  
Nmr Study

Abstract A detailed proton second moment and spin-lattice relaxation time investigation of the bilayered compound (C10H21NH3)2 CdCl4 is reported. In the low temperature phase the methyl group exe-cutes a classical threefold reorientation, while the NH3 group is involved in a similar reorientation in an asymmetric potential well. Evidence for defect chain motions in this phase has been found, and infomation regarding the potential wells associated with these motions has been extracted from the data. In the high temperature phase, slow chain defect motions and fast fourfold reorientations of chains about their long axes, parallel to the normal to the bilayer, have been observed.

An NMR study on the mechanisms of freezing and melting of water confined in spherically mesoporous silicas SBA-16

2016 ◽  
Vol 18 (27) ◽  
pp. 18555-18562 ◽  
Author(s):  
Tatsuya Miyatou ◽  
Ryutaro Ohashi ◽  
Tomonori Ida ◽  
Shigeharu Kittaka ◽  
Motohiro Mizuno
Keyword(s):  
Relaxation Time ◽  
Nmr Spectroscopy ◽  
Dynamic Properties ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Mesoporous Silicas ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

Thermodynamic and dynamic properties of water confined in mesoporous silica glass SBA-16 were investigated by DSC and 1,2H NMR spectroscopy and 2H NMR spin–lattice relaxation time as a function of pore size.

A 15N, 13C, and 1H NMR study of reaction products from arylguanidines and chloroformate esters

1991 ◽  
Vol 56 (7) ◽  
pp. 1505-1511 ◽  
Author(s):  
Antonín Lyčka ◽  
Karel Palát
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Reaction Products ◽  
H Nmr ◽  
Nmr Study

The 15N, 13C, and 1H NMR spectra of the reaction products from arylguanidines with two mols of chloroformate esters have been measured. With application of the corresponding 15N isotopomer it has been proved that the reaction products have the structures IIIa-IIIc.

Sign in / Sign up

Export Citation Format

Share Document