Low-lying excited-states of 5-benzyluracil

Abstract

A numerical study is reported concerning the first and second singlet excited-states of 5-benzyluracil using the multireference self-consistent field (state-averaged CASSCF) method. The vertical excitation energies of low-lying excited-states were characterized using the SA-CASSCF method, as well as using higher-level methods, such as CASPT2, MRCI and EOM-CCSD. The local minima and conical intersections found on the potential energy surfaces (PESs) were characterized in terms of molecular geometry and natural population analysis. Different relaxation pathways on the PESs are identified and discussed by comparing with the similar pathways found for the individual monomers of uracil and benzene. The molecule can be thought of as a model system for the study of crosslink reaction between DNA and proteins induced by UV light.

Characterization of the Photochemical Properties of 5-Benzyluracil via Time-Dependent Density Functional Theory

“…With M06-2X and CAM-B3LYP instead, the character of the low-lying transitions (Figure 2, red lines) changes drastically, and they become almost pure intrachromophore transitions, typical of the two separated chromophore species (see Figure 3). In particular, the character of these transitions is now associated with the benzene dark ππ* transition (5.10 eV in isolated benzene at the CASPT2 level of theory 6 ) and the uracil dark nπ* and bright ππ* transitions (4.54 and 5.0 eV in isolated uracil at the CASPT2 level of theory 38 ). The pure interchromophore CT transitions observed with the first set of functionals have now higher energies and are not shown.…”

A multi-scale time-resolved study of photoactivated dynamics in 5-benzyl uracil, a model for DNA/protein interactions

“…Indeed, a statistical survey of the X-ray protein structure shows that the majority of the pyrimidine bases interacting with a protein exhibit close contact (often involving pp stacking) with the side chain of a phenylalanine (a benzene ring) or of a tyrosine (a phenol ring). 30 Recent theoretical studies, using the multireference selfconsistent field (state-averaged CASSCF) method, of the photophysics and photochemistry of a single base 31 and the steadystate optical response of 5BU 32,33 confirm the extreme interest of this system in many respects. In fact, the first and second singlet excited-states of 5BU identified possible relaxation pathways on the Potential Energy Surfaces (PESs) of the molecule, different from the pathways found for the individual moieties of uracil and benzene.…”

Ultrafast Hydrogen Migration in Photoionized Glycine

“…25 With the same experimental approach the non-adiabatic relaxation as well as the nuclear rearrangement following the ionization by an XUV attosecond pulse train have been demonstrated for 5-Fluoro-and 5-Bromo-Uracil radiosensitizers 26,27 and DNA building blocks such as thymine and thymidine 28 , and it could be used in the future to investigate the ultrafast dynamics in model systems for the DNA-protein interaction such as 5-Benzil-Uracil. 29,30,31 Here we present a time-resolved study of intramolecular hydrogen migration in glycine triggered by the sudden ionization induced by an XUV attosecond pulse train and probed by few-femtosecond near-infrared (NIR) pulses.…”