Photophysical properties for excited-state intramolecular proton transfer (ESIPT) reaction of N-salicylidene-o-aminophenol: Experimental and DFT based approaches

Nutjarin Klinhom; Nikorn Saengsuwan; Suwannee Sriyab; Panida Prompinit; Supa Hannongbua; Songwut Suramitr

doi:10.1016/j.saa.2018.08.010

Photophysical properties for excited-state intramolecular proton transfer (ESIPT) reaction of N-salicylidene-o-aminophenol: Experimental and DFT based approaches

Spectrochim Acta A Mol Biomol Spectrosc. 2019 Jan 5:206:359-366. doi: 10.1016/j.saa.2018.08.010. Epub 2018 Aug 6.

Authors

Nutjarin Klinhom¹, Nikorn Saengsuwan¹, Suwannee Sriyab¹, Panida Prompinit², Supa Hannongbua¹, Songwut Suramitr³

Affiliations

¹ Laboratory of Computational and Applied Chemistry (LCAC), Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; Center for Advanced Studies in Nanotechnology for Chemical, Food and Agricultural Industries, KU Institute for Advanced Studies, Kasetsart University, Bangkok 10900, Thailand.
² National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency, Klong Luang, Pathumthani 12120, Thailand.
³ Laboratory of Computational and Applied Chemistry (LCAC), Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; Center for Advanced Studies in Nanotechnology for Chemical, Food and Agricultural Industries, KU Institute for Advanced Studies, Kasetsart University, Bangkok 10900, Thailand. Electronic address: fsciswsm@ku.ac.th.

PMID: 30145497
DOI: 10.1016/j.saa.2018.08.010

Abstract

Photophysical properties for excited-state intramolecular proton transfer (ESIPT) reaction of N-salicylidene-o-aminophenol (SA) Schiff base were comprehensively studied based on experimental methods combined with theoretical calculations. The results revealed that the SA was mainly presented in enol form in acidic solutions while it was predominantly existed in keto form in basic solutions. From UV-vis absorption and fluorescence emission studies, it showed that the ESIPT could effectively take place in non-polar and aprotic polar solvents. By using the CAM-B3LYP/6-311G(d,p) level of theory, it was found that the intramolecular proton transfer could preferably occur through six-membered ring transition rather than through five-membered ring transition. The dynamics of the ESIPT reactions of enol and keto tautomers were studied using TD-CAM-B3LYP with 6-311G(d,p) basis set. The potential energy curves for the intramolecular proton transfer in the ground (GSIPT) and excited state (ESIPT) exhibited that the GSIPT could occur through a low activation barrier, whereas in the case of ESIPT, the process could arise via low energy barrier.

Keywords: Density functional theory; Enol-keto tautomerization; Excited-state intramolecular proton transfer (ESIPT).