Influence of intermolecular hydrogen bonding and solvent effects on the excited-state properties of a photoactive yellow protein chromophore compound

• A series of hydrogen-bonded compounds of PYP chromophore were formed.
• TDDFT method was carried out to investigate the hydrogen bonding dynamics.
• It was demonstrated that the hydrogen bonds are strengthened in excited state.
• Moreover, two approaches are adopted to consider the solvation effect.

The time-dependent density functional theory (TDDFT) method has been carried out to investigate the hydrogen bonding dynamics of a series of hydrogen-bonded complexes of PYP chromophore formed with water molecules both in vacuum and aqueous solution. We demonstrate that the intermolecular hydrogen bonds formed between carbonyl oxygen and hydrogen of water are strengthened in the lowest bright state as well as one other charge transfer state and result in spectral redshift. Whereas, a totally opposite result happens to the site of phenolate oxygen, which can be confirmed based on the excited-state geometric optimizations by TDDFT method. In addition, the frontier molecular orbital analysis reveals the nature of the lowest bright state and the CT state as well as the understanding of the electronic excited-state hydrogen bonding dynamics. Moreover, two approaches are adopted to consider the solvation effect.

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