Computational prediction on photophysical properties of two excited state intramolecular proton transfer (ESIPT) fluorophores bearing the benzothiazole group

ABSTRACT

In this contribution, the photophysical properties of two excited state intramolecular proton transfer (ESIPT) fluorophores of 2,6-dibenzothiazolyl-4-methylphenol (I) and 2-benzothiazolyl-6-(2-(benzothiazolyl)vinyl)-4-methylphenol (II) were studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods at the PBE0 theoretical level. To probe into the origin of the absorption and emission bands observed experimentally, the absorption and emission spectra of I and II were simulated by the TD-PBE0/6-311 + G(d,p) calculations. In addition, the photo-induced proton enol–keto tautomerization of the two targeted molecules was also explored. The present studies indicate that a good agreement is found between theoretical predictions and experimental data. Moreover, both of these molecules can undergo an ultrafast ESIPT process, which should be responsible for the single proton-transfer tautomer emission.

GRAPHICAL ABSTRACT

KEYWORDS:

• ESIPT
• TD-DFT
• topological analysis
• non-covalent interaction analysis
• fluorescence emission

Acknowledgements

The authors thank the State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) and National Supercomputing Center in Shenzhen (Shenzhen Cloud Computing Center) for providing computational resources.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Xugeng Guo http://orcid.org/0000-0003-2152-2548

Jinglai Zhang http://orcid.org/0000-0002-2728-0511

Additional information

Funding

This work was supported by National Natural Science Foundation of China (NSFC) [grant number: 21503069 and 21676071]; Program for Henan Innovative Research Team in University [grant number: 15IRTSTHN005].