期刊
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
卷 12, 期 20, 页码 5375-5388出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/b917852j
关键词
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资金
- National Science Foundation [CHE-0911564]
- Hungarian National Science Fund (OTKA) [T60669, F61153]
- Rosztoczy Foundation
- Ministry of Education of the Czech Republic
- Austrian Science Fund [P18411-N19]
- Preamium Academiae, Academy of Sciences of the Czech Republic
- [Z40550506]
To explore the excited state dynamics of pyrimidine derivatives, we performed a combined experimental and theoretical study. We present resonant two-photon ionization (R2PI) and IR-UV double resonance spectra of 2,4-diaminopyrimidine and 2,6-diaminopurine seeded in a supersonic jet by laser desorption. For 2,4-diaminopyrimidine (S-0 -> S-1 34 459 cm(-1)), we observed only the diamino tautomer with an excited state lifetime bracketed between experimental limits of 10 ps and 1 ns. For 2,6-diaminopurine, we observed two tautomers, the 9H- (S-0 -> S-1 34 881 cm(-1)) and 7H- (S-0 -> S-1 32 215 cm(-1)) diamino forms, with excited state lifetimes of 6.3 +/- 0.4 ns and 8.7 +/- 0.8 ns, respectively. We investigated the nature of the excited state of 2,4-diaminopyrimidine by means of multi-reference ab initio methods. The calculations of stationary points in the ground and excited states, minima on the S-0/S-1 crossing seam and connecting reaction paths show that several paths with negligible barriers exist, allowing ultrafast radiationless deactivation if excited at energies slightly higher than the band origin. The sub-nanosecond lifetime found experimentally is in good agreement with this finding.
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