摘要:

Chiral detergents derived from the acylation of naturally occuring amino acids have been synthesised. These detergents have been used as chiral dopants with the achiral host potassium laurate (KDD). A correspondence has been found between the molecular stereochemistry in the micelle surface and the resulting bulk chirality. The chiral dopants potassium hexadecanoyl-L-proline (L-KHDP) and potassium hexadecanoyl-L-thiaproline (L-KHDTP) with the host achiral KDD were found to cause inversions in the sense of the twist, abnormal to the general case. These inversions in sense of twist were interpreted as originating from the compensation averaging of the cis-trans molecular conformations, derived from the rotation of the consituents about the C-N peptide bond. NMR evidence is presented to support this assertion.

ISSN:1058-725X    

DOI:10.1080/10587259508030999

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It is shown that the sensitivity of a system of triplet excitons in organic crystals to microwave radiation under conditions that give rise to the development of a annihilational bistability significantly increases. A possibility to change intensity of crystal phosphorescence by an order of magnitude by applying microwave field resonant to the transitions between spin sublevels of trapped excitons has been demonstrated.

ISSN:1058-725X    

DOI:10.1080/10587259508031000

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The experimental binary phase diagram between the pure components 2-methyl-2-nitro-1-propanol(MNP) and 2-hydroxymethyl-2-methyl-1,3-propanediol(PG) has been established from 273 K to the liquid state, using thermal analysis and X-ray powder diffraction at several temperatures.

ISSN:1058-725X    

DOI:10.1080/10587259508031001

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The oxidation of 4:4′-bi(2,6-diphenyl-1-selenopyranylidene)2 with iodine leads to a radical cation iodide salt of stoichiometry ≊ 1:2. The structure was established by X-ray crystallography and compared to that of the corresponding sulfur compound. In addition to the Bragg reflections, diffuse streak on rotation photographs indicate disordered lattices incommensurate alongcwith a repeat ofc′ ' 10.95 Å. The Raman spectra of this radical cation iodide salt shows two kinds of iodide speciesI−3andI−5with a relative concentration of 3.4, corresponding to a stoichiometry of 2-I2.03. TheIRand Raman spectra [1000–1700 cm−1range of some 4:4′-bi(chalcogenopyranylidenes) are described and compared with the 2-I2.03spectra.

ISSN:1058-725X    

DOI:10.1080/10587259508031002

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The reaction of lithio derivatives of TTF (tetrathiafulvalene) derived from TTF 1 and LDA in ether solution with 4-oxo-TEMPO (2,2,6,6-tetramethylpiperidine-N-oxy)gave 4-hydroxy-TEMPO-substituted TTF derivative 2. The magnetic susceptibility and magnetization data on polycrystalline samples of 2 as well as their CT complexes withI2, DDQ or TCNQF4revealed only weak intra- or intermolecular antiferromagnetic interactions between unpaired electrons. The decrease of magnetic susceptibility by CT formation together with their solid ESR data showing the decrease of absorption intensity suggested antiparallel spin formation between unpaired electrons in CT complexes.

ISSN:1058-725X    

DOI:10.1080/10587259508031003

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The thermal expansion of tetrakis (alkylthio) tetrathiafulvalenes (abbreviated to TTCn-TTFs. (n' 1–11)) having alkyl chains withncarbon atoms has been investigated from room temperature down to about 100 K by means of the four-circle X-ray diffraction technique. A linear thermal expansion parameter δl(' δl/δT) is suggested for correlating intermolecular interaction of TTCn-TTF crystals. For the compounds with largern,n⩾ 8, the linear thermal expansion along thec-axis, δc, is smallest, while δb, is larger and δaintermediate. This is consistent with the intermolecular interaction analyses for the crystal structure of TTCa-TTF compounds. The molecular fastener effect is also found in the thermal expansion measurements. The contributions of the molecular fastener effect and the packing effect of the end C-atoms in the alkyl chains of TTCn-TTF (n'8–11) to the thermal expansion are discussed.

ISSN:1058-725X    

DOI:10.1080/10587259508031004

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Some molecules of unusual shape and apparently non-linear geometry, with three mesogenic arms tied directly to a central unit have been investigated for liquid-crystalline behaviour. They showed smectic liquid-crystalline mesophases, which were characterised by DSC, optical microscopy and X-ray diffraction. The temperature ranges of the fluid mesophases for the monotropic compounds were below 87.6°C and for the thermotropic compound was above 142.1°C. The phase for 1 appears to be smectic A.

ISSN:1058-725X    

DOI:10.1080/10587259508031005

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The functionalization of amphiphilic quaternary ammonium salts with properly chosen interacting endgroups constitutes an easy way to produce novel liquid crystal-line materials with diversified physical properties.1Additional cyano endgroups introduce dipole-dipole interactions susceptible to strongly affect the liquid crystalline behaviour. Thus, the dialkyldimethylammonium bromides were found to produce smectic mesophases in which, because of the strong coulombic interactions between the ionic species, the lateral packing of the molecules within the layers is ordered and tetragonal in symmetry.2Introduction of a cyano endgroup attached to one of the alkyl chains, namely a propyl chain, was found to immediately transform the ordered smectic into a disordered smecticAstructure.3This is due to the fact that the cyano group induces supramolecular dimerization through its dipolar interactions. We thought it of interest to extend this study by taking quaternary alkyl(hexadecyldimethylammonium) bromides carrying a variety of endgroupsX. This paper describes some preliminary, but encouraging, results along this line.

ISSN:1058-725X    

DOI:10.1080/10587259508031006

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Structure Correlation. Edited by Hans-Beat Bürgi and Jack D. Dunitz. pp. XXIV + 888 (2 volumes). Weinheim: VCH Verlagsgesellschaft, 1994; ISBN 3-527-29042-7; 398 DM.

ISSN:1058-725X    

DOI:10.1080/10587259508031007

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:1058-725X    

DOI:10.1080/10587259508030988

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor