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Titolo:
DFT-STUDY AND POST-HF-STUDY ON STRUCTURE AND ELECTRONIC EXCITATION OFACYCLIC AND CYCLIC SULFUR DIIMIDES
Autore:
STRASSNER T; FABIAN J;
Indirizzi:
TECH UNIV DRESDEN,INST ORGAN CHEM D-01062 DRESDEN GERMANY TECH UNIV DRESDEN,INST ORGAN CHEM D-01062 DRESDEN GERMANY
Titolo Testata:
Journal of physical organic chemistry
fascicolo: 1, volume: 10, anno: 1997,
pagine: 33 - 41
SICI:
0894-3230(1997)10:1<33:DAPOSA>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
D-ORBITAL PARTICIPATION; 2ND-ROW ATOMS; HARTREE-FOCK; S2N2; MOLECULES; POLYMER; NITRIDE; SYSTEMS; ISOMERS; (SN)X;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
71
Recensione:
Indirizzi per estratti:
Citazione:
T. Strassner e J. Fabian, "DFT-STUDY AND POST-HF-STUDY ON STRUCTURE AND ELECTRONIC EXCITATION OFACYCLIC AND CYCLIC SULFUR DIIMIDES", Journal of physical organic chemistry, 10(1), 1997, pp. 33-41

Abstract

A series of representative organic acyclic and cyclic sulfur diimideswere studied by Hartree-Fock-plus-correlation ab initio quantum chemistry and by density functional theory using Becke's three-parameter functional along with the LYP functional. The widely used formula representation -N=S=N- for these compounds suggests octet expansion of sulfur, This is not confirmed by theory, Although d-polarization functions significantly improve the numerical results, sulfur d-orbitals are hardly occupied, The calculated electronic charge distribution derived bypopulation analysis and by the atoms-in-molecules topological theory favors charge separation resulting in a more or less ylidic structure with -N=S+-N-- and -N-=S+-N- resonance contributors, This structure does not exclude relatively short SN bond lengths. The characteristics of the bonds in the parent structures is preserved in some non-Kekule-type NSN heterocyles. Strong SN bond charge separations of organyl sulfur diimides are accompanied by short SN bond distances and narrow S-0/T-1 and S-0/S-1 energy gaps. The experimentally well known naphtho[1,8-cd][1,2,6]thiadiazine and the unknown 3,4-dimethylene-1,2,5-thiadiazole belong to this series. The calculations confirm that 1,2,3-thiadiazole is the diaza analog of thiophene rather than the vinylene-bridged sulfur diimide, while more complex heterocycles such as benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole take an intermediate position between classical and non-classical structures, Two closely related minimum structures are defined on the DFT Born-Oppenheimer energy surface of naphtho[1,8-cd; 4,5-c'd']bis[1,2,6]thiadiazine, but so far only one compound is experimentally known, The lowest energy structure is the quinoid form corresponding to the experimentally known compound.

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Documento generato il 26/09/20 alle ore 12:12:21