Double-proton-transfer processes in dithiooxamide: UV-induced dithione -> dithiol reaction and ground-state dithiol -> dithione tunneling

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Lapinski L., Rostkowska H., Khvorostov A., Yaman M., Fausto R., Nowak M.

JOURNAL OF PHYSICAL CHEMISTRY A, cilt.108, sa.26, ss.5551-5558, 2004 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 108 Sayı: 26
  • Basım Tarihi: 2004
  • Doi Numarası: 10.1021/jp049263w
  • Dergi Adı: JOURNAL OF PHYSICAL CHEMISTRY A
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.5551-5558
  • Eskişehir Osmangazi Üniversitesi Adresli: Evet

Özet

Dithiooxamide [rubeanic acid, NH2C(=S)C(=S)NH2)] monomers were studied by FTIR spectroscopy combined with the low-temperature matrix-isolation technique. The most stable dithione-diamino tautomer of the compound was exclusively observed in argon matrixes immediately after deposition. Upon UV (lambda > 345 nm) irradiation the dithione-diamino form transformed, by a double-proton transfer, into the dithiol-diimino tautomer. Theoretically supported analysis of the infrared spectrum emerging upon UV irradiation allowed identification of one of the conformers of the dithiol-diimino tautomer as the dominating photoproduct. Smaller quantities of other conformers of the dithiol-diimino tautomer were also found to be photogenerated. For the UV-irradiated matrix kept subsequently at 10 K and in darkness, a dithiol-diimino-->dithione-diamino tautomerization leading to partial recovery of the initial form of the compound was observed. The only possible mechanism of this ground-state transformation at cryogenic temperature is synchronous double-proton tunneling. The experimentally obtained time constant of this process was 18 h.