Thermodynamic and structural behaviour of equimolar POPC/CnE4 (n=8, 12, 16) mixtures by sorption gravimetry, 2H NMR spectroscopy and X-ray diffraction

Bent-core liquid crystals showing a nematic phase stable at low temperatures are very attractive for applicative purposes in view of the inherent biaxial nature of the nematic phase. In this work, a typical five-ring bent-core mesogen was investigated by means of 2H NMR spectroscopy and X-ray diffraction (XRD) methods. These techniques provide complementary information on the structural properties of the nematic phase and the average mesogen conformation: small-angle XRD reveals the presence of short-range positional order in the form of skewed cybotaxis, while a comparison of the orientational order parameters measured by wide-angle XRD and NMR provides an estimate of the molecule bend angle. In addition, 2H NMR puts in evidence the occurrence of an unexpected transition to a low-temperature tilted phase, having a crystalline or smectic-like character. The results were compared with those of previous 13C NMR investigations.

Download Full-text

Phase Separation in Binary Mixtures of Bipolar and Monopolar Lipid Dispersions Revealed by 2H NMR Spectroscopy, Small Angle X-Ray Scattering, and Molecular Theory

Biophysical Journal ◽

10.1016/j.bpj.2009.06.058 ◽

2009 ◽

Vol 97 (10) ◽

pp. 2700-2709 ◽

Cited By ~ 16

Author(s):

David P. Brownholland ◽

Gabriel S. Longo ◽

Andrey V. Struts ◽

Matthew J. Justice ◽

Igal Szleifer ◽

...

Keyword(s):

Phase Separation ◽

Nmr Spectroscopy ◽

Binary Mixtures ◽

Small Angle ◽

Molecular Theory ◽

2H Nmr ◽

X Ray ◽

2H Nmr Spectroscopy ◽

X Ray Scattering ◽

Ray Scattering

Download Full-text

An unusual reaction of a bridged triterpenoid α-diketone with acetic anhydride

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19912917 ◽

1991 ◽

Vol 56 (12) ◽

pp. 2917-2935 ◽

Cited By ~ 1

Author(s):

Eva Klinotová ◽

Václav Křeček ◽

Jiří Klinot ◽

Miloš Buděšínský ◽

Jaroslav Podlaha ◽

...

Keyword(s):

Acetic Acid ◽

Nmr Spectroscopy ◽

Acetic Anhydride ◽

Spectral Methods ◽

X Ray Diffraction ◽

X Ray ◽

Mild Conditions ◽

Condensation Products ◽

Unsaturated Lactones ◽

C Nmr

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.

Download Full-text

Unusual Rearrangement of Naphthalene in the Synthesis of a Novel B8-B8-Bridged Derivative in the [(1,2-C2B9H11)2-3-Co]- Series. X-Ray Structure and 11B NMR Spectra of [8,8'-μ-(CH2-C9H6)-(1,2-C2B9H10)2-3-Co]- (CH3)4N+

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19970746 ◽

1997 ◽

Vol 62 (5) ◽

pp. 746-751 ◽

Cited By ~ 7

Author(s):

Andreas Franken ◽

Jaromír Plešek ◽

Christiane Nachtigal

Keyword(s):

Nmr Spectroscopy ◽

Single Crystal ◽

Nucleophilic Substitution ◽

Nmr Spectra ◽

X Ray Diffraction ◽

X Ray ◽

Unusual Rearrangement ◽

Multinuclear Nmr Spectroscopy ◽

11B Nmr ◽

Isolated Compound

On treatment of the [(1,2-C2B9H11)2Co]- ion with naphthalene in presence of AlCl3 a remarkably bridged [8,8'-μ-(CH2-C9H6)-(1,2-C2B9H10)2-3-Co]- ion is obtained as a single isolated compound. The triatomic -CH2-C9H6- bridge is derived from the rearranged naphthalene nucleus. The mechanism of this reaction is obscure but it does resemble the "Electrophile-Induced Nucleophilic Substitution" reported earlier. The structure of the compound was established by multinuclear NMR spectroscopy and by single crystal X-ray diffraction.

Download Full-text

Ten-Vertex Polyhedral Monocarbaborane Chemistry. The Novel High-Yield Formation of the Ten-Vertex closo Compound [6-(PMe2Ph)-closo-1-CB9H9] from the Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11]

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19932924 ◽

1993 ◽

Vol 58 (12) ◽

pp. 2924-2935 ◽

Cited By ~ 8

Author(s):

Jane H. Jones ◽

Bohumil Štíbr ◽

John D. Kennedy ◽

Mark Thornton-Pett

Keyword(s):

Nmr Spectroscopy ◽

Diffraction Analysis ◽

High Yield ◽

Monoclinic Space Group ◽

The Novel ◽

X Ray Diffraction ◽

Metal Centre ◽

X Ray ◽

Yield Formation ◽

Boiling Toluene

Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.

Download Full-text

Wideline 2H -NMR Spectroscopy and Imaging of Solids

Zeitschrift für Naturforschung A ◽

10.1515/zna-1994-1-206 ◽

1994 ◽

Vol 49 (1-2) ◽

pp. 19-26 ◽

Cited By ~ 4

Author(s):

B. Blümich

Keyword(s):

Nmr Spectroscopy ◽

Excitation Power ◽

Magic Angle Spinning ◽

Magic Angle ◽

2H Nmr ◽

Stochastic Excitation ◽

2H Nmr Spectroscopy ◽

Spatially Inhomogeneous ◽

Recent Developments ◽

Angle Spinning

Abstract Recent developments, focussing on reduction of the rf excitation power by stochastic excitation, on improvements in sensitivity and excitation bandwidth by magic angle spinning, and on combining wideline spectroscopy with spatial resolution for investigations o f spatially inhomogeneous objects are reviewed.

Download Full-text