Hofmann type clathrates - spectroscopic studies of the low frequency region

A series of Hofmann type clathrates with a general formula: M(NH3)(2)M'(CN)(4)center dot 2G, where M is an element of {Ni, Mn, Cd}, M' is an element of {Ni, Pd}, while G is benzene or thiophene, were prepared and their Raman and far-infrared spectra were recorded in the region 650-50 cm(-1)

FT-IR spectroscopic investigation of Hofmann Td-type complexes of 2-, and 3-chloropyridine

Hofmann-type modified clathrate hosts containing 2- or 3-chloropyridine molecules attached to metal (II) tetracyanocadmate frame, with a given formula: M(Clpy)(2)Cd(CN)(4), where M = Mn, Ni or Cd; Clpy = 2- or 3-chloropyridine, have been synthesised for the first time. Their FT-IR spectra are reported in the 400-4000 cm(-1) region. All the vibrational modes of coordinated Clpy are characterised. The spectral features of the compounds studied are found to be similar to each other indicating that they have analogous structures. The coordination effect on the Clpy modes is analyzed

Vibrational spectra of (M3MS3)-M-I-S-III type synthetic minerals (M-I = Tl or Ag and M-III = As or Sb)

The vibrational (Raman and far infrared) spectra of four (M3MS3)-M-I-S-III type synthetic minerals (proustite, Ag3AsS3; ellisite, Tl3AsS3; pyrargyrite, Ag3SbS3; stibioellisite, Tl3SbS3) in the region from 600 to 100 cm(-1) (Raman) and 600 to 20cm(-1) (far infrared) were investigated. Their infrared and Raman spectra were compared with corresponding vibrational spectra of natural orpiment, As2S3, and stibnite, Sb2S3. In general, rather expressed similarity between the Raman spectra of the (M3AsS3)-As-I type synthetic minerals, and particularly between the (M3SbS3)-Sb-I type synthetic minerals (M-I = Ag or Tl) was observed. This is, most probably, due to the presence of the (MS3)-S-III pyramids (M-III = As or Sb) as main structural units in all minerals. The observed similarity between the Raman spectra of the (M3AsS3)-As-I type minerals and the corresponding spectrum of orpiment, As2S3 (also built up of (MS3)-S-III pyramids), justifies the treatment of those pyramids as a main vibrational units. The agreement between the Raman spectra of (M3SbS3)-Sb-I type minerals, on the one hand, and the Raman spectrum of stibnite, Sb2S3, on the other hand, is even much more pronounced. It was found, however, that the bands in the infrared spectra in the studied (M3MS3)-M-I-S-III type minerals, besides the sensitivity to the M-III atom (As or Sb), are significantly influenced by the nature of the M-I atom (Ag or Tl). This is most probably related to the different extent of the covalent character of the Ag-S bonds compared to the Tl-S bonds. (C) 2003 Published by Elsevier B.V

Vibrational spectra of (MMIII)-M-I S-2 type synthetic minerals (M-I = Tl or Ag and M-III = As or Sb)

The far infrared and Raman spectra of four (MMS2)-M-I-S-III type synthetic minerals (lorandite, TIAsS2; smithite, AgAsS2; weissbergite, TlSbS2, and miargyrite, AgSbS2) were studied at room temperature. Their vibrational spectra were compared with the corresponding far infrared and Raman spectra Of (M2S3)-S-III type minerals: orpiment, As2S3 and stibnite, Sb2S3. In spite of different crystal structure of these minerals, a similarity between the vibrational spectra of the three arsenic containing minerals (orpiment, As2S3; lorandite, TlAsS2 and smithite, AgAsS2), on the one hand, and the three antimony containing minerals (stibnite, Sb2S3; weissbergite, TlSbS2 and miargyrite, AgSbS2), on the other hand, has been detected. The observed spectral behavior was discussed in terms of structural similarities and differences between the minerals containing As atoms and the ones containing Sb atoms. Thus, the arsenic containing minerals are characterized by the layer-like structure and the presence of rather similar As-S bond distances (208-236 pm), whereas the antimony containing minerals have sheet-like structure and the variety of Sb-S bond distances, spreading in a wider range of values (241-296 pm). (C) 2003 Elsevier Science B.V. All rights reserved