摘要:

In crystallization processes from solution, parameters like crystal habit, grain size, grain size distribution, concentration and type of impurities/dopants can be controlled by addition of admixtures.

ISSN:1058-725X    

DOI:10.1080/10587259808044265

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A variety of 1: 1 charge-transfer (CT) crystals were prepared by using mainly dinitrobenzoic acids (as the acceptor) and carbazoles (as the donor). Most of the CT crystals prepared from 3,5-dinitrobenzoic acid (3) and a series of N-alkylcarbazoles (1a−1h)underwent photoredox reactions initiated by the excited nitro group, leading to α-oxidation of N-alkyl groups (13−15). The reactions were much more efficient in the solid state than in solution. These solid-state photoreactivities could be, on the whole, correlated with the C···O distances between the carbazole N-α-carbon atom and the nitro oxygen atoms nearby.

ISSN:1058-725X    

DOI:10.1080/10587259808044266

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A p-dimethylaminobenzenesulfonate (MSE) polycrystalline powder is converted to the zwitterion p-trimethylammoniumbenzenesulfonate (ZWT) by chemical thermally induced reaction at T = 55,5°C. This reaction is associated to a first order ferroelastic phase transition in partially reacted MSE crystals. A13C-NMR study made during the in situ transformation MSE → ZWT shows that the reaction is of first order. A strong change appears in the low frequency Raman and Brillouin spectra of MSE monocrystals when passing the transition, but only a continuous evolution in the intensity of the high frequency modes is observed. Birefringence observations permit to specify the evolution of the optical axes position during the chemical reaction. The importance of stress induced by the reaction is discussed in relation to the phase transition.

ISSN:1058-725X    

DOI:10.1080/10587259808044267

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

2H NMR techniques are employed to study the structure and dynamics of guest molecules in Cyclophosphazene inclusion compounds. A detailed analysis of the variable temperature NMR experiments provides quantitative information about the molecular mobility of the guest components within the Cyclophosphazene channels. It is shown that the guest species are highly mobile displaying internal conformational motions and overall reorientational processes along with a considerable amount of dynamic disorder. For the overall motions a strong influence by the actual structure (or symmetry) of the organic guest molecules is registered.

ISSN:1058-725X    

DOI:10.1080/10587259808044268

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We discuss the general peculiarities of low temperature co-condensates and influence of the sample preparation conditions on the chemical reactions in co-condensates. Hydrohalogenation of olefins and explosive reactions in solid co-condensates Mg-dichloroethan, acetylchlorid-diethy-lamin are condidered. The scheme of influence of mechanical stresses in growing films on the chemical reactions is suggested.

ISSN:1058-725X    

DOI:10.1080/10587259808044269

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Origins of the bond length anomalies observed for the X-ray structures of a series of organic compounds are discussed in terms of molecular motion and reactions in crystals.

ISSN:1058-725X    

DOI:10.1080/10587259808044270

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Steroidal acids and their derivatives form inclusion compounds with a variety of organic substances. Over one thousand derivatives are candidates for hosts of the compounds. The study on steroidal inclusion compounds provides systematic data for considering relationships between molecular structures and molecular assemblies, indicating that combinatorial chemistry can be applied to inclusion chemistry.

ISSN:1058-725X    

DOI:10.1080/10587259808044271

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Inclusion complex formation of thiocoumarin with optically active host compound in the solid state was followed by continuous measurement of CD spectra in Nujol mull. Enantioselective photodimerization reaction of thiocoumarin in the inclusion complex was also followed successfully by using the CD spectroscopy in the solid state.

ISSN:1058-725X    

DOI:10.1080/10587259808044272

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Host1, 2,5-bis(9-hydroxyfluoren-9-yl)thieno[2,3-b]thiophene, showed no guest selectivity in enclathration ofn−PrOH andi−PrOH, forming (1)(i−PrOH)x(n−PrOH)2-x(X=0∼2). The X-ray crystal analyses of (1)(n−PrOH)2, (1)(i−PrOH)2, (1)(n−PrOH)14(i−PrOH)0.6, and (1)(n−PrOH)0.4(i−PrOH)1.6revealed that all of these host lattices arc isostructural and constitute a channel-type of inclusion lattice, in which one site is preferentially occupied by the major guest, while the other site is shared with two guest components. Upon exposure of (1)(i−PrOH)2crystals ton−PrOH vapor the guest molecules are exchanged by the gaseous guest to give the 1:1:1 ternary clathrate crystal (1)(n−PrOH)(i−PrOH), in which cach ofn−PrOH andi−PrOH molecules is embedded at its preferential site respectively. This guest exchange by gaseous guest is interpreted in terms of kinetic site-selectivity in guest migration in the channel, not involving the reorganization of the three-component molecules on the crystal surface.

ISSN:1058-725X    

DOI:10.1080/10587259808044273

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Irradiation of α-cinnamic acid crystals at their absorption tail at 365 and 405 nm and with filtered daylight gives surface features due to long-range molecular movements and phase rebuilding similar to the features in the shorter wavelength irradiations. AFM measurements indicate that the molecular migrations are guided by the crystal structure. Features such as walls, fences and trenches all follow the direction of the cleavage planes at 39° to thec−axis. Volcano-like features also require upward molecular transport. The visibly detectable disintegration of the crystals at low conversions in all cases is studied in some detail. A topotactic reaction is not observed.

ISSN:1058-725X    

DOI:10.1080/10587259808044274

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor