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Exploring the ESIPT dynamical processes of two novel chromophores: symmetrical structure CHC and asymmetric structure CHN

Abstract

The detailed excited-state intramolecular proton transfer (ESIPT) dynamical processes of two novel chromophores 8,8’-((1E,1E’)-hydrazine-1,2-diylidenebis(methanylylidene))bis-(7-hydroxy-4-methyl-2H-chromen-2-one) (CHC) (symmetrical structure) and 7-hydroxy-8-((E)-((E)-((2-hydroxynaphthalen-1-yl)-methylene)hydrazono)methyl)-4-methyl-2H-chromen-2-one (CHN) (asymmetric structure), which were synthesized in a previous work (Xiao et al. New. J. Chem. 2014, 38, 2386), have been investigated based on density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The analysis of bond lengths, angles and IR vibrational spectra confirmed that the intramolecular hydrogen bonds (HBs) of CHC and CHN molecules were strengthened in the S1 state, which could facilitate the ESIPT reactions. In addition, intramolecular charge transfer based on the frontier molecular orbitals (MOs) and the maps of the electron density difference between the S0 and S1 states provided the possibility of ESIPT reactions for these two molecules. Moreover, to explore the detailed ESIPT dynamical processes of CHC and CHN molecules, the potential energy surfaces (PESs) in the S0 and S1 states were constructed. The low excited-state potential barriers illustrated that both stepwise and simultaneous double ESIPT processes could occur for these two molecules. For the symmetrical structure CHC, two pathways of ESIPT processes existed as pathwayⅠ (stepwise double PT) and pathwayⅡ (simultaneous double PT). The relationship of the potential barriers was pathwayⅡ (4.71 kcal/mol) < pathwayⅠ (6.15 and 7.62 kcal/mol), which manifested that the pathwayⅡ was more prone to double ESIPT for CHC molecule. For the asymmetric structure CHN, three pathways of ESIPT processes existed as pathwayⅢ (stepwise double PT: firstly H8 from O7 to N9, and secondly H11 from O10 to N12 ), pathwayⅣ (other stepwise double PT: firstly H11 from O10 to N12, and secondly H8 from O7 to N9) and pathwayⅤ(double PT). The relationship of the potential barriers was pathwayⅢ (2.67 and 6.75 kcal/mol) < pathwayⅣ (3.04 and 7.24 kcal/mol) < pathwayⅤ (7.69 kcal/mol), which indicated that the pathwayⅢ was more susceptible to double ESIPT for CHN molecule. Obviously, the ESIPT processes of the asymmetric structure CHN was more complicated than that of the symmetric structure CHC.

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Publication details

The article was received on 18 Dec 2017, accepted on 07 Feb 2018 and first published on 08 Feb 2018


Article type: Research Article
DOI: 10.1039/C7QO01127J
Citation: Org. Chem. Front., 2018, Accepted Manuscript
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    Exploring the ESIPT dynamical processes of two novel chromophores: symmetrical structure CHC and asymmetric structure CHN

    J. J. Hao and Y. Yang, Org. Chem. Front., 2018, Accepted Manuscript , DOI: 10.1039/C7QO01127J

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