Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
On the molecular and vibrational structure of 1,6,6a lambda(4)-trithiapentalenes. Analysis of the "bell-clapper'' asymmetrical S-S-S stretching mode
Autore:
Spanget-Larsen, J; Andersen, KB;
Indirizzi:
Roskilde Univ, Dept Chem & Life Sci, DK-4000 Roskilde, Denmark Roskilde Univ Roskilde Denmark DK-4000 fe Sci, DK-4000 Roskilde, Denmark
Titolo Testata:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
fascicolo: 6, volume: 3, anno: 2001,
pagine: 908 - 916
SICI:
1463-9076(2001)3:6<908:OTMAVS>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
INFRARED LINEAR DICHROISM; SPECTROSCOPY; POLYETHYLENE; EXCHANGE; ENERGY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Spanget-Larsen, J Roskilde Univ, Dept Chem & Life Sci, Bldg 17-2,POB 260, DK-4000 Roskilde, Denmark Roskilde Univ Bldg 17-2,POB 260 Roskilde DenmarkDK-4000
Citazione:
J. Spanget-Larsen e K.B. Andersen, "On the molecular and vibrational structure of 1,6,6a lambda(4)-trithiapentalenes. Analysis of the "bell-clapper'' asymmetrical S-S-S stretching mode", PHYS CHEM P, 3(6), 2001, pp. 908-916

Abstract

The molecular and vibrational structure of the 1,6,6a lambda (4)-trithiapentalene (TTP) ring system was studied by experimental and theoretical procedures. IR absorption spectra were recorded of 2,5-dimethyl-1,6,6a lambda (4)-trithiapentalene (DMTTP) in liquid solution, in a stretched polyethylene matrix, and in solid state tablet samples. The linear dichroism observed inthe stretched polymer sample provided experimental symmetry assignments ofthe observed vibrational states. The results of B3LYP and B3PW91 density functional theoretical calculations were in good agreement with the observedmolecular geometries and vibrational transitions for TTP and DMTTP. The computed molecular structures were characterized by sulfonium ylide-like Mulliken charge distributions (positively charged, three-coordinated sulfur center in position 6a, negatively charged carbons in positions 2, 3a and 5), consistent with the large dipole moments reported for these species. Of particular interest was the strong vibrational transition observed around 187 cm(-1) in the far-IR spectrum of DMTTP, similar to the transition previouslyobserved at 153 cm(-1) for TTP. These transitions must be assigned to the asymmetrical S-S-S stretching vibration, the so-called "bell-clapper" mode. According to B3LYP and B3PW91 calculations the potential is U-shaped, corresponding to a negative anharmonicity constant x(e) in the order of -0.025. Anharmonic effects are predicted to increase the frequency of the fundamental transition by about 5%. Hartree-Fock (HF) theory predicts a double-minimum potential for this mode, while post-HF Moller-Plesset second-order perturbation theory (MP2) predicts a single-minimum potential with a complicated shape and a positive anharmonicity.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/03/20 alle ore 14:23:06