Double-Proton-Transfer Processes in Dithiooxamide: UV-Induced Dithione → Dithiol Reaction and Ground-State Dithiol → Dithione Tunneling
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 (λ > 3...
| Main Author: | |
|---|---|
| Other Authors: | , , , , |
| Format: | article |
| Language: | eng |
| Published: |
2004
|
| Online Access: | http://hdl.handle.net/10316/17880 |
| Country: | Portugal |
| Oai: | oai:estudogeral.sib.uc.pt:10316/17880 |
| Summary: | 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 (λ > 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. |
|---|