Geometries of the C2-puckered S1 minimum and of the main S1/S0 conical intersections in 9H-adenine.
Energy gap between the ππ*(La) and the nπ* states. CC2/aug-cc-pVTZ result from Ref. 100. MS-CASPT2/aug-cc-pVTZ result from Ref. 101.
Potential energy profiles for reaction pathways between the ground state minimum geometry (0 Å amu1/2) and the conical intersections puckered at C6 and C2 for different theoretical levels. Ground state energies are only partially shown (near the end of the pathways). TDDFT, RI-CC2, and DFT/MRCI with aug-cc-pVDZ. CASPT2: SS–dotted lines; MS–solid lines. MRCIS: 1n–dotted lines; 2n–solid lines.
Potential energy profiles for reaction pathways between the S1 minimum geometry (0 Å amu1/2) and the conical intersections puckered at C6 and C2 for different theoretical levels. TDDFT and RI-CC2 with aug-cc-pVDZ. CASPT2: SS–dashed lines; MS–solid lines. MRCIS: 1n–dashed lines; 2n–solid lines. The circle in the TD-PBE0 profile indicates the peak of the Q distribution during the dynamics simulations.
Distribution of the Cremer-Pople parameters θ and ϕ for trajectories simulated with MRCIS-1n, MRCIS-2n, and OM2/MRCI (5 references, no decoherence correction). MRCIS-1n data from Ref. 24. The crosses indicate the conical intersections computed at each level. Red regions are more densely populated.
Gradient projection along the C2 and C6 puckering directions for 60 trajectories simulated with OM2/MRCI (5 references, no decoherence correction) and ab initio MRCIS methods at times 0, 20, and 40 fs. The elliptical fitting of data is shown as well.
Absorption cross section computed with TDDFT employing four different functionals. The shaded areas indicated the energy windows (L = low, M = medium, H = high) from which initial conditions were selected for dynamics simulations.
Cremer-Pople parameters for the M window from the TD-PBE0 and TD-BHLYP dynamics. (Top) Degree of puckering (Q) as a function of time. (Bottom) Type of puckering in terms of ϕ and θ parameters. The parameter values for the last point in the respective reaction pathways, Fig. 4, are indicated by crosses and dashed lines. Red regions are more densely populated.
Summary of results from dynamics simulations of UV-excited adenine with different methods.
Vertical excitation energies (in eV) at TDDFT level using different functionals. Oscillator strengths in parenthesis. The experimental value for the π-π*(La) state is 5.16 ± 0.07 eV. The amount of HF exchange in the functional increases from left (0% in PBE) to right (100% in M06-HF).
Vertical excitation energies (in eV) at ab initio and semi-empirical levels. Oscillator strengths in parenthesis. The experimental value for the π-π*(La) state is 5.16 ± 0.07 eV.
Characterization of the S1 minimum of adenine in terms of Q (degree of puckering) and conformation. Percentage of trajectories following the C2-puckered pathway for the M spectral window within 1 ps. HF – fraction of Hartree-Fock exchange in the functional.
Geometrical characterization of the C2- and C6-puckered conical intersections of 9H-adenine optimized at OM2/CI (5 references) and ab initio MRCIS-2n levels. d MW is the mass-weighted distance between the conical intersection and the ground state minimum geometries. The values in parenthesis are MRCIS-1n results from Ref. 24. Q, θ, and ϕ are the Cremer-Pople parameters.
Fraction of the population converted to the ground state after 1 ps according to experiments and simulations at several theoretical levels. Gas-phase data supposing single exponential decay, as a function of the initial excitation energy.
Number of trajectories (N traj) initiated in each state for TD-B3LYP and TD-PBE0 for each of the three spectral windows. Number of S1→S0 events and corresponding times (τ hop given in parenthesis). With the exception of the S1→S0 events marked with “b,” all others correspond to N9-H dissociation.
Number of trajectories (N traj) initiated in each state for TD-PBE, TD-BHLYP, TD-CAM-B3LYP, and TD-M06-HF. Number of S1→S0 events and corresponding approximate times (τ hop given in parenthesis). With the exception of the S1→S0 events marked with “b,” all others correspond to N9-H dissociation.
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