Effect of substituents on the excited-state dynamics of the modified DNA bases 2,4-diaminopyrimidine and 2,6-diaminopurine

Zsolt Gengeliczki, Michael P. Callahan, Nathan Svadlenak, Csaba István Pongor, Bálint Sztáray, Leo Meerts, Dana Nachtigallová, Pavel Hobza, Mario Barbatti, Hans Lischka, Mattanjah S. de Vries

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Abstract

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 (S0→ S1 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- (S0→ S1 34 881 cm-1) and 7H- (S0→ S1 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 S0/S1 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.

Original languageEnglish
Pages (from-to)5375-5388
Number of pages14
JournalPhysical Chemistry Chemical Physics
Volume12
Issue number20
DOIs
StatePublished - Jan 1 2010

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Gengeliczki, Z., Callahan, M. P., Svadlenak, N., Pongor, C. I., Sztáray, B., Meerts, L., Nachtigallová, D., Hobza, P., Barbatti, M., Lischka, H., & de Vries, M. S. (2010). Effect of substituents on the excited-state dynamics of the modified DNA bases 2,4-diaminopyrimidine and 2,6-diaminopurine. Physical Chemistry Chemical Physics, 12(20), 5375-5388. https://doi.org/10.1039/b917852j