Time-dependent density functional theory study on excited state intramolecular proton transfer of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one

• Published in: Journal of luminescence 2010-08, Vol.130 (8), p.1431-1436
• Main Authors: Zhao, Xiaohong, Liu, Yufang, Zhou, Lichuan, Li, Yuanzuo, Chen, Maodu
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Bonding; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Density functional theory; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Excitation; Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion); Hydrogen bonds; Lewis acid; Luminescence; Molecular properties and interactions with photons; Physics; Switches; Tautomers
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2010.03.007

The time-dependent density functional theory (TDDFT) method was carried out to investigate the excited state intramolecular proton transfer (ESIPT) process of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one (1a). 1a has two tautomeric forms: one is 1a(O), which is induced by intramolecular hydrogen bond O-H[cdots, three dots, centered]O=C, and the other one is 1a(N), which is caused by intramolecular hydrogen bond O-H[cdots, three dots, centered]N. From excited state to tautomer excited state coming from ESIPT, the hydroxyl hydrogen breaks away and the dissociated hydrogen adsorbed on pyridinic nitrogen or carbonyl oxygen formed new intramolecular HB and the corresponding bond length and bond angle varied greatly. In comparison, a similar process of proton transfer for 1a(N)H super(+) protonated 1a(N) from ground state to excited state was obtained. This detailed proton transfer mechanism was provided by molecular orbitals analysis and it may be applied to molecular switch and organic Lewis acid/base. We investigated the excited state proton transfer mechanism of the four molecules through the theoretical method for the first time and gave unambiguous geometry of excited state.