TY - JOUR

T1 - Structure and stability of radical cations from cyclic and open-chain dithia compounds in aqueous solutions

AU - Asmus, K. D.

AU - Bahnemann, D.

AU - Fischer, C. H.H.

AU - Veltwisch, D.

N1 - Copyright: Copyright 2017 Elsevier B.V., All rights reserved.

PY - 1979/2/1

Y1 - 1979/2/1

N2 - The formation of intra-and some intermolecular radical cation complexes has been observed during the oxidation of cyclic and open-chain organic dithia compounds (the two S atoms not adjacent) by hydroxyl radicals in aqueous solutions. These species are characterized by a new sulfur-sulfur bond established by interaction of the unpaired p electron from the oxidized sulfur atom with the free p-electron pair of a second sulfur atom. Two of these electrons form a cσ; bond while the third is promoted to an antibonding σ*level. At low solute concentration (typically around 10-4M) intramolecular complex formation predominates. The radical cation complexes show characteristic broad optical absorptions which are attributable to a σ; → σ*transition. The position of the absorption maximum (reflecting the σ/σ*energy difference) and the extinction coefficients are related to the p-orbital overlap between the two interacting sulfur atoms. The extent of overlap depends on the internuclear distance, r(S.S), and particularly on the angular relationship between the interacting orbitals. Other structural parameters influencing λmaxare the flexibility of the species formed and possible interactions between the σ;(S, S) bond with σ;(C, C) bonds. λmaxis found to range from 400 to 650 nm, these particular values referring to the iVWramolecular radical cation complexes from 1, 5-dithiacyclooctane and 1, 4-dithiacyclohexane, respectively. ϵ values are found up to 7 X 103M-lcm-1. The lifetimes of the radical cation complexes depend on the stability of the new sulfur-sulfur bond and may well extend into the millisecond range in aqueous solutions.

AB - The formation of intra-and some intermolecular radical cation complexes has been observed during the oxidation of cyclic and open-chain organic dithia compounds (the two S atoms not adjacent) by hydroxyl radicals in aqueous solutions. These species are characterized by a new sulfur-sulfur bond established by interaction of the unpaired p electron from the oxidized sulfur atom with the free p-electron pair of a second sulfur atom. Two of these electrons form a cσ; bond while the third is promoted to an antibonding σ*level. At low solute concentration (typically around 10-4M) intramolecular complex formation predominates. The radical cation complexes show characteristic broad optical absorptions which are attributable to a σ; → σ*transition. The position of the absorption maximum (reflecting the σ/σ*energy difference) and the extinction coefficients are related to the p-orbital overlap between the two interacting sulfur atoms. The extent of overlap depends on the internuclear distance, r(S.S), and particularly on the angular relationship between the interacting orbitals. Other structural parameters influencing λmaxare the flexibility of the species formed and possible interactions between the σ;(S, S) bond with σ;(C, C) bonds. λmaxis found to range from 400 to 650 nm, these particular values referring to the iVWramolecular radical cation complexes from 1, 5-dithiacyclooctane and 1, 4-dithiacyclohexane, respectively. ϵ values are found up to 7 X 103M-lcm-1. The lifetimes of the radical cation complexes depend on the stability of the new sulfur-sulfur bond and may well extend into the millisecond range in aqueous solutions.

UR - http://www.scopus.com/inward/record.url?scp=33845559382&partnerID=8YFLogxK

U2 - 10.1021/ja00512a035

DO - 10.1021/ja00512a035

M3 - Article

AN - SCOPUS:33845559382

VL - 101

SP - 5322

EP - 5329

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 18

ER -