Naslov
Delocalization of the Unpaired Electron in the Three-Electron Cl-S Bond: ENDOR Study

Autori
Sanković, Krešimir ; Herak, Janko N. ; Hole, Eli O. ; Sagstuen, Einar

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
1999 Europian Conference on Inorganic Mechanisms - Program and Abstracts / - Zagreb, 2000, 28 - 28

Skup
1999 Europian Conference on Inorganic Mechanisms Annual Conference of the Royal Society of Chemistry, Dalton Division Inorganic Reaction Mechanisms Group

Mjesto i datum
Zagreb, Hrvatska, 06.01.2000. - 09.01.2000

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
ENDOR; EPR; three-electron bond

Sažetak
The "two-centre three-electron" bond found in many activated species (radicals) is usually considered to be strictly localised on the two bonded atoms. Here we show that if one of the atoms participating in the formation of the * bond is a part of a conjugated system, the unpaired electron is delocalised, both via the -bonding (short range) and the -bonding (long range) sub-systems. We studied the interaction of the unpaired electron of the three-electron S-Cl bond in the chlorinated thiocytosine radical with the neighbouring protons by electron-nuclear-double resonance (ENDOR) spectroscopy. The SCl bond is formed on thiocytosine (imbedded in the crystal lattice of cytosine hydrochloride) by acquisition of a chlorine atom that has lost an electron upon ionising irradiation. It is shown that the unpaired electron of the three-electron bond significantly interacts with at least seven protons from its neighbourhood. Five of them have been assigned. From the nature of the coupling tensors it is concluded that three protons are constituents of the chlorine-thiocytosine radical, and the remaining two belong to the neighbouring cytosine molecules. The nature of the dipolar component of the coupling tensors is not consistent with the idea of the location of the entire electron in the SCl bond. From both isotropic and anisotropic tensor components it is concluded that the unpaired electron is significantly delocalised over the radical. It has been estimated that the spin density in the SCl bond is only about 0.4. The data also suggest that we deal with the radical protonated at both N-1 and N-3 positions.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

POVEZANOST RADA