摘要:

The crystal and molecular structures of α,ω-bis [4-(4′-hexyloxybenzylideneiminophenyl)]octane (6O.8.O6) and the homologue α,ω-bis [4-(4′-heptyloxybenzylideneiminophenyl)]octane (7O.8.O7) have been determined by direct methods at room temperature. The crystals of both compounds belong to the monoclinic system with space group P 21/a and two molecules per unit cell which are placed on centers of symmetry. For 6O.8.O6: a = 10.613(4), b = 8.7596(10), c = 22.149(7) Å, β = 100.02(2)°; for 7O.8.O7: a = 5.909(4), b = 7.412(3), c = 47.174(27) Å, β = 91.15(3)°. The structures were refined by full-matrix least-squares calculations against F to R = 0.078 for 4993/(3596 unique) collected reflections for 6O.8.O6 and to R = 0.077 for 1772/(1548 unique) reflections for 7O.8.O7.

ISSN:1058-725X    

DOI:10.1080/10587250008024810

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The infrared spectra of variousp-n-alkoxybenzoic acids are reported. The carbonyl stretching region of these materials is surprisingly sensitive to packing within the various crystal forms, a consequence of the sensitivity of these modes to hydrogen bonding and transition dipole coupling. The isotypic crystal form found in those acids with n>6 are characterized by a splitting in the carboxyl C=O stretching region, a consequence of interactions between the disordered arrangement of carboxyl groups from layer to layer. This splitting is not observed in those alkoxybenzoic acids where n<7. The infrared spectra also show that there is a solid state transformation from the crystalline state to conformationally disordered or ``condis” crystals as intermediates between the crystalline and liquid crystalline forms.

ISSN:1058-725X    

DOI:10.1080/10587250008024811

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Electron magnetic resonance (EMR) studies of intercalation ferromagnet 2,2′-bipyridine-MnPS3(Tc= 40 K) in the temperature range 300 – 14 K have revealed many interesting features across the (magnetic) order ← → disorder transition. The exchange narrowed line in the paramagnetic phase exhibited sudden reduction in its intensity concomitant with a g-shift to lower values (line shifted to higher fields) and increased line width. These changes took place in the 40–25 K range. In the 25–22K range of temperature, the paramagnetic line disappeared and the FMR signal appeared at lower fields. It is significant that two closely lying FMR signals appeared in the magnetically ordered regime, suggesting the possibility of existence of two different Mn-sites having different g-values, in this state. This may be responsible for the reported magnetic moments values of less than 5.98 BM from bulk magnetisation studies.

ISSN:1058-725X    

DOI:10.1080/10587250008024812

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The crystal and molecular structures of (A) 3,5-Diacetyl-2,6-dimethyl-4-(3′-nitrophenyl)-1,4-dihydropyridine, (B) 3,5-Dibenzoyl-2,6-dimethyl-4-(3′-nitrophenyl)-1,4-di hydropyridine and (C) 3,5-Dicarbomethoxy-2,6-dimethyl-4-(4′-methylthiophenyl)-1,4-dihydropyridine derivatives were determined by X-ray diffraction methods.

ISSN:1058-725X    

DOI:10.1080/10587250008024813

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The crystal and molecular structures of 1-Methyl-2-Isopropyl-5-Nitroimidazole (A) and 1-Methyl-2(Thiophenyl)-Methyl-5-Nitroimidazole (B) derivatives were determined by X-ray diffraction methods.

ISSN:1058-725X    

DOI:10.1080/10587250008024814

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587250008024815

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587250008024816

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587250008024817

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587250008024818

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587250008024819

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor