摘要:

A semi-empirical AMl study of hydrogen bonding and protonation in water has been carried out to illustrate the two different O-H vibrational frequencies present in the protonated water dimer, H5O2+. Using the MOPAC quantum mechanical program, it is shown that the optimized geometry for this species is C2h, with an O-H bond distance of 1.20Å, and the fifteen normal frequencies have been determined. Results predict the two O-H vibrational frequencies at 553 and 3300 cm−1, with the former being the H-bond stretching mode. A grid calculation illustrating how the potential energy surface of water varies with the H-O-H angle and the O-H bond distance is also presented.

ISSN:0038-7010    

DOI:10.1080/00387019909350029

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The solid complexes of Mn2+, FE3+, Co2+, Ni2+and Cu2+with six azo compounds based on 8-arylazo-6,7-dihydroxy-4-methylcoumarin have been synthesized and characterizd by elemental and thermal analysis, magnetic susceptibility, molar conductance as well as IR spectroscopy, where it is found that metal ions are surrounded by coordinated water molecules and one ligand molecule bonded in a bidentate O and N fashion in the case of ligand 1 and in tridentate ONO fashion in the case of all the remaining ligands forming a coordination number of six in all cases. The potentiality of the prepared azo componds as new chromophoric reagents for the spectrophotometric determination of the metal ions is studied by extensive investigation of the optimum conditions favouring the formation of coloured complexes in solution.

ISSN:0038-7010    

DOI:10.1080/00387019909350030

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Fragments of the ancient wall painting (c.550 - 580 AD) from the archaeological site of Wanzhang (Heibei, China) were analyzed by Raman Microscopy. The pigments with different colors were identified by Raman Microscopy, which are respectively cinnabar, goethite, carbon black and calcite doped with other metal atoms.

ISSN:0038-7010    

DOI:10.1080/00387019909350031

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new series of trichloromethylated- 4, 5-dihydro-1H-pyrazoles has been studied. The molecular structure of 5-hydroxy-3-phenyl-5-trichloromethyl-4,5-dihydro-7H-pyrazole-1-carboxyamide (2), synthesized from the reaction of 4-methoxy -4-phenyl-1,1,1-trichloro-3-buten-2-one (1) with semicarbazide hydrochloride, was selected and determined by NMR spectroscopy, X-ray diffraction, and semiempirical MO calculations.

ISSN:0038-7010    

DOI:10.1080/00387019909350032

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The Tb3+-doped strontium quinolinate was prepared by rheological phase reaction method. The thermal stability, powder X-ray diffraction, infrared, emission and excitation spectra are investigated. The energy transfer mechanism from C5H3N(CO2)2to Tb3+ion and the influence of structure and heterocycle on the luminescence intensity were discussed. The energyS1π,π excited states of C5H3N(CO2)2can be transferred to5D4of Tb3+ion to send out the5D4→Fjtransition emission of Tb3+.The nitrogen heterocycle makes the excitation band of Tb3+ion shift to short wavelength.

ISSN:0038-7010    

DOI:10.1080/00387019909350033

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Spectra of107Ag18O and107Ag16O molecules have been obtained in a low-pressure arc in oxygen atmosphere, and recorded with medium dispersion. Vibrational assignments for the bands ofB2π —X2π system were verified by the study of the oxygen isotope effect, and the vibrational constants were obtained for the states involved in transitions.

ISSN:0038-7010    

DOI:10.1080/00387019909350034

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The metal binding sites in the two Pt containing metallothioneins (Pt7MT and Pt14MT) were examined by means of Pt(II) L3-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. Comparisons between the phase and amplitude functions derived from the isolated shells to those of Pt…Pt, Pt-S and Pt-N model components showed that each platinum in Pt7MT was coordinated by four sulfur atoms at a distance of 2.31±0.01 Å. Analysis of the outer shell data of platinum atom in Pt7MT indicated backscattering platinum atom at approximate 4.29 Å. Strikingly different structural parameters had been obtained for the Pt14MT species, fitting of the first shell revealed that each platinum was coordinated by two sulfurs at the distance of 2.30±0.02 Å and two nitrogens at 2.02±0.02 Å. The results of the work provided the detailed information concerning the local environments of the coordinated Pt(II) in these two platinothioneins.

ISSN:0038-7010    

DOI:10.1080/00387019909350035

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor