The sodium perchlorate complex of cis-syn-cis dicyclohexano-24-crown-8 ether. X-ray crystal structure and solution conformations as studied by variable temperature 13C NMR spectroscopy at 125 MHz. An example of eight-coordinate sodium

1992 ◽  
Vol 70 (6) ◽  
pp. 1688-1695 ◽  
Author(s):  
G. W. Buchanan ◽  
Y. Lear ◽  
C. Bensimon
Keyword(s):  
Crystal Structure ◽  
Variable Temperature ◽  
Sodium Perchlorate ◽  
13C Nmr Spectroscopy ◽  
Ring Inversion ◽  
X Ray ◽  
Free Energy Of Activation ◽  
Perchlorate Complex ◽  
C Nmr ◽  
Coalescence Temperature

The major isomer obtained by hydrogenation of dibenzo-24-crown-8 ether is shown to have the cis-syn-cis configuration as determined from the crystal structure of its sodium perchlorate complex. This material possesses eight-coordinate sodium with Na—O distances ranging from 2.54 to 2.78 Å. The complex is shown to exist in a single asymmetric conformation below 240 K as determined by 13C NMR at 125 MHz. From NMR coalescence temperature measurement, the free energy of activation for cyclohexane ring inversion in this complex has been determined to be 51.0 ± 0.6 kJ/mol.

The hydroxonium perchlorate complex of cis-syn-cis-dicyclohexano 18-crown-6 ether: conformational analysis in the solid state and in solution at low temperature as studied via 13C NMR methods

1991 ◽  
Vol 69 (12) ◽  
pp. 1964-1969 ◽  
Author(s):  
G. W. Buchanan ◽  
C. Morat ◽  
R. A. Kirby ◽  
J. S. Tse
Keyword(s):  
Solid State ◽  
Title Complex ◽  
Torsional Angle ◽  
Free Energy Barrier ◽  
Inversion Process ◽  
Ring Inversion ◽  
Nmr Methods ◽  
Perchlorate Complex ◽  
C Nmr ◽  
Coalescence Temperature

From 100.6-MHz 13C NMR coalescence temperature measurements, the title complex is shown to undergo a single degenerate ring inversion process with a free energy barrier of [Formula: see text]. This is ca. 5 kJ/mol higher than the barrier in the free crown. The solid state 13C CPMAS spectrum is indicative of a totally unsymmetrical conformation and the shift trends in the solid are analyzed in terms of local torsional angle variations. Comparisons of experimental vs. calculated (GIAO) 13C chemical shift ranges for the CH2O carbons in the solid are made and satisfactory agreement with respect to the overall range and magnitude of the 13C shielding differences is obtained. Key words: crown ethers, stereochemistry, NMR.

Negative hyperconjugation in hexachloro-3-cyclopentenylaminosulphenyl halides: Preparation and X-ray structure of C5Cl6NSBr and synthesis of C5Cl6NS+AsF6−

1991 ◽  
Vol 69 (6) ◽  
pp. 1022-1027 ◽  
Author(s):  
Allen Apblett ◽  
Tristram Chivers ◽  
James F. Fait ◽  
Rainer Vollmerhaus
Keyword(s):  
Crystal Structure ◽  
Key Words ◽  
Good Yield ◽  
Variable Temperature ◽  
Triclinic Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Compound C ◽  
Negative Hyperconjugation ◽  
C Nmr

The reaction of hexachlorocyclopentadiene with (NSCl)3 at 65 °C in the absence of a solvent produced hexachloro-3-cyclopentenylidenaminosulfenyl chloride, C5Cl6NSCl, in good yield. The derivatives C5Cl6NSX(X = Br, I, C5Cl6N, NPr2i, Ph) were prepared by treatment of C5Cl6NSCl with Me3SiBr, Me3SiI, Ph3Sb, iPr2NH, and Ph2Hg, respectively. The crystal structure of C5Cl6NSBr was determined by X-ray crystallography. Crystals of C5Cl6NSBr are triclinic, space group [Formula: see text] with a = 9.626(2), b = 9.810(2), c = 13.736(2) Å, α = 79.68(1), β = 88.62(1), γ = 74.73(1)°, Z = 4, final R and Rw values were0.075 and 0.063, respectively, for 4850 unique observed reflections. The > C=NSBr moiety adopts a syn conformation and there are two different molecules of C5Cl6NSBr in the asymmetric units. The bond lengths are d(C=N) = 1.278(8) and 1.253(8), d(N—S) = 1.560(6) and 1.569(6), and d(S—Br) = 2.229(2) and2.235(2) Å. The bond angles at nitrogen are 146.7(4) and 148.6(4) and those at sulfur are 116.8(2) and 116.5(2)°. The unusual geometry of the < C=NSBr moiety is explained in terms of negative hyperconjugation (nN → σSBr*). A variable temperature 13C NMR of C5Cl6NSCl provides evidence for a fiuxional process (ΔG*298 = 68.1 ± 1.2 kJ mol−1) in solution. The dark purple compound C5Cl6NS+AsF6− was synthesized from the reaction of C5Cl6NSCl and AgAsF6 in SO2. Key words: hexachloro-3-cyclopentenylidenamino sulfides, crystal structure, hexachloro-3-cyclopentenylidenaminosulfenyl bromide.

Darstellung, 11B-, 13C-, 29Si-NMR- und Schwingungsspektren von Trimethylsilylmethyl-hexahydro-closo-hexaborat, [B6H6(CH2Si(CH3)3)]- sowie Kristallstruktur von [P(C6H5)4][B6H6(CH2Si(CH3)3)] / Preparation, 11B, 13C, 29Si NMR and Vibrational Spectra of Trimethylsilylmethyl-hexahydro-clo-hexaborate, [B6H6(CH2Si(CH 3)3)]-and the Crystal Structure of [P(C6H5)4] [B6H6(CH2Si(CH3)3)]

1995 ◽  
Vol 50 (7) ◽  
pp. 1025-1029 ◽  
Author(s):  
J. Baurmeister ◽  
A. Franken ◽  
W. Preetz
Keyword(s):  
Crystal Structure ◽  
Monoclinic Space Group ◽  
29Si Nmr ◽  
X Ray Diffraction ◽  
Nmr Spectrum ◽  
X Ray ◽  
Quadrupole Coupling ◽  
Stretching Vibration ◽  
Ir And Raman ◽  
C Nmr

By reaction of [N(C4H9 )4]2 [B6H6] with iodomethyl-trimethylsilane in acetonitrile a solution with trimethylsilylm ethyl-closo-hexaborate(1-)anions, [B6H6 (CH2Si(CH3)3)]-, is formed. The crystal structure of [P(C6H5 )4][B6H6(CH2Si(CH3)3)] has been determined by single crystal X-ray diffraction analysis; monoclinic, space group P21/n with a = 16.140(2), b = 11.646(8), c = 16.731(3) Å, β 109.664(11)°. The 11B NMR spectrum reveals features of a mono hetero substituted octahedral B6 cage. The 13C NMR spectrum exhibits a quartet at +0.18 ppm with 1J(C,H) = 118 Hz for the three methyl groups and a weak multiplet at -0.65 ppm for the methylene bridge due to quadrupole coupling with the boron atoms. In the 29Si NMR spectrum a decet at +2.25 ppm with 2J(C,H ) = 6.9 Hz is observed. The B -C stretching vibration is observed at 1155 cm-1 in the IR and Raman spectrum.

scholarly journals Powder study of 3-azabicyclo[3.3.1]nonane-2,4-dione form 2

2006 ◽  
Vol 62 (7) ◽  
pp. o3046-o3048 ◽  
Author(s):  
Ashley T Hulme ◽  
Philippe Fernandes ◽  
Alastair Florence ◽  
Andrea Johnston ◽  
Kenneth Shankland
Keyword(s):  
Crystal Structure ◽  
Simulated Annealing ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Title Compound ◽  
Variable Temperature ◽  
Polycrystalline Sample ◽  
Asymmetric Unit ◽  
X Ray ◽  
Compound C

A polycrystalline sample of a new polymorph of the title compound, C8H11NO2, was produced during a variable-temperature X-ray powder diffraction study. The crystal structure was solved at 1.67 Å resolution by simulated annealing from laboratory powder data collected at 250 K. Subsequent Rietveld refinement yielded an R wp of 0.070 to 1.54 Å resolution. The structure contains two molecules in the asymmetric unit, which form a C 2 2(8) chain motif via N—H...O hydrogen bonds.

scholarly journals Investigation of Solvatomorphism and Its Photophysical Implications for Archetypal Trinuclear Au3(1-Methylimidazolate)3

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4404
Author(s):  
Shengyang Guan ◽  
David C. Mayer ◽  
Christian Jandl ◽  
Sebastian J. Weishäupl ◽  
Angela Casini ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Density Functional ◽  
Bulk Material ◽  
Variable Temperature ◽  
Active Phase ◽  
Solvent Free ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aurophilic Interactions

A new solvatomorph of [Au3(1-Methylimidazolate)3] (Au3(MeIm)3)—the simplest congener of imidazolate-based Au(I) cyclic trinuclear complexes (CTCs)—has been identified and structurally characterized. Single-crystal X-ray diffraction revealed a dichloromethane solvate exhibiting remarkably short intermolecular Au⋯Au distances (3.2190(7) Å). This goes along with a dimer formation in the solid state, which is not observed in a previously reported solvent-free crystal structure. Hirshfeld analysis, in combination with density functional theory (DFT) calculations, indicates that the dimerization is generally driven by attractive aurophilic interactions, which are commonly associated with the luminescence properties of CTCs. Since Au3(MeIm)3 has previously been reported to be emissive in the solid-state, we conducted a thorough photophysical study combined with phase analysis by means of powder X-ray diffraction (PXRD), to correctly attribute the photophysically active phase of the bulk material. Interestingly, all investigated powder samples accessed via different preparation methods can be assigned to the pristine solvent-free crystal structure, showing no aurophilic interactions. Finally, the observed strong thermochromism of the solid-state material was investigated by means of variable-temperature PXRD, ruling out a significant phase transition being responsible for the drastic change of the emission properties (hypsochromic shift from 710 nm to 510 nm) when lowering the temperature down to 77 K.

Triazene derivatives of (1,x-)diazacycloalkanes. Part VI. 3-({5,5-Dimethyl-3-[2-aryl-1-diazenyl]-1-imidazolidinyl}methyl)-4,4-dimethyl-1-[2-aryl-1-diazenyl]imidazolidines — Synthesis, characterization, and X-ray crystal structure

2006 ◽  
Vol 84 (10) ◽  
pp. 1294-1300 ◽  
Author(s):  
Keith Vaughan ◽  
Shasta Lee Moser ◽  
Reid Tingley ◽  
M Brad Peori ◽  
Valerio Bertolasi
Keyword(s):  
Crystal Structure ◽  
Significant Degree ◽  
Ion Trapping ◽  
Published Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diazonium Ion ◽  
Derivatives Of ◽  
C Nmr

Reaction of a series of diazonium salts with a mixture of formaldehyde and 1,2-diamino-2-methylpropane affords the 3-({5,5-dimethyl-3-[2-aryl-1-diazenyl]-1-imidazolidinyl}methyl)-4,4-dimethyl-1-[2-aryl-1-diazenyl]imidazolidines (1a–1f) in excellent yield. The products have been characterized by IR and NMR spectroscopic analysis, elemental analysis, and X-ray crystallography. The X-ray crystal structure of the p-methoxycarbonyl derivative (1c) establishes without question the connectivity of these novel molecules, which can be described as linear bicyclic oligomers with two imidazolidinyl groups linked together by a one-carbon spacer. This is indeed a rare molecular building block. The molecular structure is corroborated by 1H and 13C NMR data, which correlates with the previously published data of compounds of types 5 and 6 derived from 1,3-propanediamine. The triazene moieties in the crystal of 1c display significant π conjugation, which gives the N—N bond a significant degree of double-bond character. This in turn causes restricted rotation around the N—N bond, which leads to considerable broadening of signals in both the 1H and 13C NMR spectra. The molecular ion of the p-cyanophenyl derivative (1b) was observed using electrospray mass spectrometry (ES + Na). The mechanism of formation of molecules of type 1 is proposed to involve diazonium ion trapping of the previously unreported bisimidazolidinyl methane (13).Key words: triazene, bistriazene, imidazolidine, synthesis, X-ray crystallography, NMR spectroscopy.

Solid state stereochemistry of crown ethers: X-ray crystal structure and 13C NMR studies of the LiNCS complex of 1,4,7,11-tetraoxacyclotetradecane

2000 ◽  
Vol 78 (3) ◽  
pp. 316-321
Author(s):  
G W Buchanan ◽  
A B Driega ◽  
G PA Yap
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crown Ether ◽  
13C Nmr ◽  
Title Complex ◽  
Nmr Studies ◽  
Nmr Spectrum ◽  
X Ray ◽  
Large Amplitude Motion ◽  
C Nmr

The title complex is asymmetric in the crystal due to the spatial orientation of the NCS function. The space group has been determined to be P21 with a = 9.496(3), b = 8.736(3), c = 9.676(3) Å, β = 117.859(5)°, and Z = 2. The solid state 13C NMR spectrum is consistent with the lack of symmetry in the crystal and there is little evidence for large amplitude motion in the macrocycle as determined from the dipolar dephased spectrum.Key words: macrocyclic crown ether, lithium complex.

Lipophilic cage ligands containing two tightly connected 1,7-dioxa-4,10-diazacyclododecane rings: synthesis and x-ray structure of a sodium perchlorate complex

1988 ◽  
Vol 53 (22) ◽  
pp. 5292-5298 ◽  
Author(s):  
Pier Lucio Anelli ◽  
Fernando Montanari ◽  
Silvio Quici ◽  
Gianfranco Ciani ◽  
Angelo Sironi
Keyword(s):  
Sodium Perchlorate ◽  
X Ray ◽  
Perchlorate Complex
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