Molecular Mechanism of Diaminomaleonitrile to Diaminofumaronitrile Photoisomerization: An Intermediate Step in the Prebiotic Formation of Purine Nucleobases
| Autoři | |
|---|---|
| Rok publikování | 2014 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Chemistry - A European Journal |
| Fakulta / Pracoviště MU | |
| Citace | |
| www | http://onlinelibrary.wiley.com/doi/10.1002/chem.201304224/pdf |
| Doi | http://dx.doi.org/10.1002/chem.201304224 |
| Obor | Fyzikální chemie a teoretická chemie |
| Klíčová slova | isomerization; nucleobases; nucleotides; photochemistry; quantum chemistry |
| Popis | The photoinduced isomerization of diaminomaleonitrile (DAMN) to diaminofumaronitrile (DAFN) was suggested to play a key role in the prebiotically plausible formation of purine nucleobases and nucleotides. In this work we analyze two competitive photoisomerization mechanisms on the basis of state-of-the-art quantum-chemical calculations. Even though it was suggested that this process might occur on the triplet potential-energy surface, our results indicate that the singlet reaction channel should not be disregarded either. In fact, the peaked topography of the S-1/S-0 conical intersection suggests that the deexcitation should most likely occur on a sub-picosecond timescale and the singlet photoisomerization mechanism might effectively compete even with a very efficient intersystem crossing. Such a scenario is further supported by the relatively small spin-orbit coupling of the S-1 and T-2 states in the Franck-Condon region, which does not indicate a very effective triplet bypass for this photoreaction. Therefore, we conclude that the triplet reaction channel in DAMN might not be as prominent as was previously thought. |
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