title: Photoinduced excited state intramolecular proton transfer and spectral behaviors of Aloesaponarin 1.
abstract: The novel spectral behaviors of Aloesaponarin 1 (AS1) are investigated by studying the dynamics process of excited state intramolecular proton transfer (ESIPT). Two intramolecular hydrogen bonds (HB1 and HB2) are formed between hydroxyl and carbonyl groups of AS1. The calculated potential energy curves of AS1 demonstrate that the ESIPT process along HB1 is energy favorable while not along HB2. The analysis of potential energy curves describes clearly the dynamic behaviors of the proton transfer process from hydroxyl group to carbonyl group along HB1. The infrared spectra of AS1 confirm that the stretching absorption peak of hydroxyl group in HB1 disappears and that a new peak corresponding to hydroxyl group appears in the first excited state, which depicts the ESIPT process indirectly. The fluorescence peaks of AS1 (636nm), AS2 (Aloesaponarin 1 3-O-methyl ether, 629 nm) and AS3 (Aloesaponarin 1 8-O-methyl ether, 522 nm) demonstrate that the fluorescence behavior of AS1 is primarily effected by HB1 rather than HB2. The large Stokes shifts of AS1 (206 nm) indicate that the absorbed energy is partly transferred to non-harmful long fluorescence through ESIPT process, which plays important role in the explanation for the UV protection property of AS1. The inducement and influence factors of ESIPT process of AS1 are illustrated by analyzing electrostatic potential, molecular orbital and natural bond orbital.
authors.affiliation: College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China. Electronic address: liuyufang2005@163.com.
authors.forename: Yufang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Physics Laboratory, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Yang
authors.affiliation: College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: College of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Jiang
authors.affiliation: College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Sun
mesh_terms: D000880:Anthraquinones / Q000737:chemistry*; D005453:Fluorescence; D008956:Models, Chemical; D011522:Protons; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared; D055672:Static Electricity
chemical_list: D000880:Anthraquinones; D011522:Protons; C584681:aloesaponarin I
keywords: Aloesaponarin 1; ESIPT; Hydrogen bond; Spectral behaviors; UV protection