engleski

A TD-B2-PLYP study of excited state proton transfer in malonaldehyde

The double-hybrid density functional B2-PLYP is based on a mixing of standard GGAs for exchange and correlation with HF exchange and a perturbative second-order correlation part. It outperforms most of the standard functionals in obtaining accurate vertical excitation energies. Still its reliability and efficiency for the organic and bioorganic photoreactions has not been thoroughly explored so far. Therefore, the aim of this study is to assess the performance of the B2-PLYP density functional for excited-state proton/hydrogen transfer reactions using malonaldehyde as a model molecule. It will be shown that adiabatic xcitation energies for the S1 and the S2 states are in excellent agreement while the energy barriers for the reaction in the S0 and the S1 states are slightly underestimated with respect to the reference MR-AQCC values. Also, as shown in Figure 1, it will be demonstrated that B2-PLYP corrects the excited state potential energy profile of the S2 state along the hydrogen atom transfer coordinate in a similar way as CASPT2 does on the small CASSCF reference and yields much better results compared to standard functional like PBE0 or B3LYP.

TD-DFT; excited-state intramolecular proton transfer; malonaldehyde; photochemistry

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