scholarly journals Gearing motion in cogwheel pairs of molecular rotors: weak-coupling limit

CrystEngComm ◽  
2015 ◽  
Vol 17 (41) ◽  
pp. 7829-7834 ◽  
Author(s):  
Jiří Kaleta ◽  
Josef Michl ◽  
Cécile Mézière ◽  
Sergey Simonov ◽  
Leokadiya Zorina ◽  
...  
Keyword(s):  
Weak Coupling ◽  
Lattice Relaxation ◽  
Rotor Dynamics ◽  
Weak Coupling Limit ◽  
Molecular Rotors ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spin Lattice ◽  
Dft Modelling

Investigation of the rotor dynamics by X-ray diffraction, spin–lattice relaxation, and DFT modelling of the two rotational barriers in arrays of rod-like molecules with 1,3-bis(ethynyl)bicyclo[1.1.1]pentane rotators conclude to gearing motion between two rotors in a pair.

Molecular Reorientation in the Plastic Crystalline Phase of Tris

1979 ◽  
Vol 32 (4) ◽  
pp. 905 ◽  
Author(s):  
RE Wasylishen ◽  
PF Barron ◽  
DM Doddrell
Keyword(s):  
Phase Transition ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Molecular Reorientation ◽  
Liquid Phase Transition ◽  
X Ray ◽  
Spin Lattice

Carbon-13 N.M.R. spectra of tris(hydroxymethyl)aminomethane (Tris) have been measured between 407 and 461 K. Proton-decoupled 13C N.M.R. spectra of solid Tris between 407 K and its melting point are relatively sharp (v� < 30 Hz) indicating rapid overall molecular reorientation in this temperature range. It was not possible to detect a 13C N.M.R, signal for Tris below 407 K. The observed 13C N.M.R. spin-lattice relaxation times appear continuous across the solid ↔ liquid phase transition. From the temperature dependence of T1, a rotational activation energy of 51.6 � 6 kJ mol-1 is calculated, which indicates that the molecules must expend considerable energy in reorienting. The N.M.R. results are discussed in relation to previous differential scanning calorimetry and X-ray diffraction data which indicate that Tris undergoes a solid ↔ solid transition at 407 K.

Molecular Motions in Halogen-Bridged One-Dimensional Pt Complexes, [PtII(en)2][PtIVX2(en)2](ClO4)4 (X = Cl, Br) Studied by 2H and 1H NMR

2002 ◽  
Vol 57 (6-7) ◽  
pp. 413-418 ◽  
Author(s):  
Noriyoshi Kimura ◽  
Toru Hachisuka ◽  
Yukitaka Nakano ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Energy Difference ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Potential Wells ◽  
One Dimensional ◽  
X Ray ◽  
Spin Lattice ◽  
H Nmr

2H and 1H NMR measurements were performed on crystalline [Pt(en)2][PtX2(en)2](ClO4)4 (X = Cl, Br), where the protonated and partially deuterated ethylenediamines (en’s), NH2(CH2)2NH2, NH2(CD2)2NH2 and ND2(CH2)2ND2 were used as ligands. Measurements of 2H and 1H NMR spin-lattice relaxation times showed the presence of motions of en chelate rings at the temperatures near the phase transitions, whereas broad 2H NMR spectra and the reported X-ray diffraction data showed no marked motions. These results were consistently explained by introducing the en puckering motion between highly asymmetric potential wells with an energy difference of 10 - 13 kJ mol-1. This difference was shown to be much larger than 2 - 5 kJ mol-1, reported for the iodo-complex, [Pt(en)2][PtI2(en)2](ClO4)4

A study of molecular motion in tetramethylphosphonium halides by proton magnetic resonance

1976 ◽  
Vol 54 (12) ◽  
pp. 1985-1990 ◽  
Author(s):  
T. T. Ang ◽  
B. A. Dunell
Keyword(s):  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Hexagonal Crystal ◽  
Methyl Group ◽  
X Ray ◽  
Spin Lattice ◽  
Second Moments

Spin–lattice relaxation times of tetramethylphosphonium chloride, bromide, and iodide were measured between 100 and 500 K and the two minima in T1 found for each compound have been assigned to methyl group reorientation and whole cation tumbling. The second moments also indicate that the cations are tumbling isotropically at nmr frequencies in the upper half of this temperature range, and suggest that librational oscillation of the whole cation occurs at frequencies at least of the order of 105 s−1 near 150 K. The energy barriers for both methyl group reorientation and isotropic tumbling decrease from chloride to bromide but increase when one goes from bromide to iodide. Powder photograph X-ray diffraction analysis indicates that the chloride and bromide have hexagonal crystal structures (a and c measured), but that the iodide has lower, undetermined symmetry.

scholarly journals 35Cl NQR, 1H NMR, and X-Ray Diffraction Studies in a Hydrogen Bonded Complex Na2PtCl6 · 6H2O

1998 ◽  
Vol 53 (6-7) ◽  
pp. 603-607 ◽  
Author(s):  
Hiroshi Miyoshi ◽  
Keizo Horiuchi ◽  
Narumi Sakagami ◽  
Kenichi Okamoto ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Time ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spin Lattice ◽  
Temperature Dependences

Abstract The 35Cl NQR frequencies, spin-lattice relaxation time and 1H NMR relaxation time were measured on crystalline Na2PtCl6 • 6H2O at 77-350 K. The presence of three nonequivalent chlorine sites found by X-ray diffraction measurement is in agreement with the observed three NQR lines, which have different temperature dependences attributable to differences in the direction of H-bonding with water molecules. The three NQR lines correspond to three kinds of chlorines with different Pt-Cl distances and H-bond directions.

NUCLEAR MAGNETIC RESONANCE STUDY OF 205Tl IN MULTIPHASE Tl-Ba-Ca-Cu OXIDE SUPERCONDUCTORS

1988 ◽  
Vol 02 (05) ◽  
pp. 1227-1234 ◽  
Author(s):  
L. Mihály ◽  
K. Tompa ◽  
I. Bakonyi ◽  
P. Bánki ◽  
É. Zsoldos ◽  
...  
Keyword(s):  
Room Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Nuclear Magnetic Resonance Study ◽  
Spin Lattice Relaxation ◽  
Oxide Superconductors ◽  
X Ray Diffraction ◽  
Magnetic Resonance Study ◽  
X Ray ◽  
Spin Lattice

Several batches of T l- Ba - Ca - Cu oxide superconductors have been synthesized and characterized by resistivity, magnetic susceptibility and X-ray diffraction measurements. The 205 T l NMR line snifts (K), the spin-lattice and spin-spin relaxation times have been measured at room temperature. The temperature dependence of the spin-lattice relaxation rate is also reported. The resonance around K = 0.25 % has a composite line shape indicating the presence of two T l sites. The two sites are tentatively assigned to thallium atoms in the (2223) and (2212) T l- Ba - Ca - Cu phases.

Crystal Structure and Cationic Motion of o-Toluidinium Chloranilate and m-Toluidinium Chloranilate Studied by X-ray Diffraction and 1H NMR

2003 ◽  
Vol 58 (11) ◽  
pp. 631-637 ◽  
Author(s):  
Takeo Fukunaga ◽  
Naoki Kumagae ◽  
Hiroyuki Ishida
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Molecular Orbital Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spin Lattice

The crystal structure of o-toluidinium chloranilate and m-toluidinium chloranilate, 2CH3C6H4-NH3+ · C6O4Cl22−, was determined by single crystal X-ray diffraction at room temperature. It was found that o-toluidinium chloranilate (I) is monoclinic, P21/n (#14), Z = 2, a = 5.2184(14), b = 7.825(2), c = 22.840(5) Å , and β = 92.015(19)°, and m-toluidinium chloranilate (II) is monoclinic, P21/c (#14), Z = 2, a = 11.214(2), b = 5.4844(10), c = 16.379(6) Å, and β = 105.21(2)°. In these salts, the cations are connected with the anions by N-H... O hydrogen bonds to form 2:1 units of 2CH3C6H4NH3+ · C6O4Cl22− that are located on inversion centers. The 2CH3C6H4NH3+ · C6O4Cl22− units in both salts are connected by other N-H... O hydrogen bonds to build a three-dimensional hydrogen-bond network. Motions of the toluidinium ions in solid (I) and (II) were studied by 1H NMR spin-lattice relaxation time measurements. Reorientations of the NH3+ group about the C-N bond axis and the CH3 group about the C-C bond axis were observed, and their motional parameters were evaluated. The internal rotational barriers of the NH3+ and CH3 groups of an isolated o-toluidinium ion were estimated from ab initio molecular orbital calculations at HF/6-31G(d,p), MP2/6-31G(d,p), and B3LYP/6-31G(d,p) levels of theory.

scholarly journals Methyl and t-butyl group rotation in a molecular solid: 1H NMR spin-lattice relaxation and X-ray diffraction

2016 ◽  
Vol 18 (3) ◽  
pp. 1720-1726 ◽  
Author(s):  
Peter A. Beckmann ◽  
Curtis E. Moore ◽  
Arnold L. Rheingold
Keyword(s):  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spin Lattice ◽  
Butyl Group ◽  
Relaxation Experiments ◽  
Group Rotation ◽  
Resonance Spin ◽  
Molecular Solid

We report solid state 1H nuclear magnetic resonance spin-lattice relaxation experiments and X-ray diffractometry in 2-t-butyldimethylsilyloxy-6-bromonaphthalene.

35Cl NQR and Crystal Structure Studies of Salts of Chlorodifluoro- and Dichloroacetic Acid

1992 ◽  
Vol 47 (1-2) ◽  
pp. 241-253 ◽  
Author(s):  
Reha Basaran ◽  
Shi-qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Dichloroacetic Acid ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Spin Lattice ◽  
Chlorodifluoroacetic Acid ◽  
Reorientation Motion ◽  
Guanidinium Salt

AbstractThe 35Cl NQR spectra of several chlorodifluoroacetates were studied as a function of temperature, including the acid ClF2CCOOH. The cations were: Ammonium, guanidinium, paramethylanilinium. Also some acid salts M⊕ClF2CCOO⊖ • n - ClF2CCOOH ( n > l ) were studied by 35Cl NQR. The bleaching temperatures of the NQR signals were determined. In the para-methylanilinium salt and in the guanidinium salt a phase transition has been observed. The crystal structure of guanidinium chlorodifluoroacetate has been determined at room temperature (a = 1089 pm, 6 = 845 pm, c = 832 pm, space group Pnma, Z = 4). For comparison, guanidinium dichloroacetate was studied by 35Cl NQR and by X-ray diffraction, too: P21/c, Z = 4 , a = 804pm, b = 1202 pm, c = 1080 pm, ß = 131.58°. For guanidinium chlorodifluoroacetate and chlorodifluoroacetic acid, the 35Cl spin lattice relaxation time T1 and the line width have been followed up as a function of temperature. Therefrom, the activation energies of the reorientation motion of the group -CF2C1 have been determined to be 14 kJ • mol-1 (from T1) and 12.5 kJ • mol- 1 (from Δv) for the pure acid and 9.2 kJ • mol-1 and 8.8 kJ • mol-1 , respectively, for the guanidinium salt.

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