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Issue 4, 2017
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A spectroscopic study of the excited state proton transfer processes of (8-bromo-7-hydroxyquinolin-2-yl)methyl-protected phenol in aqueous solutions

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Abstract

A combination of spectroscopic methods and density functional theory (DFT) computations was used to study the excited state proton transfer (ESPT) processes of (8-bromo-7-hydroxyquinolin-2-yl)methyl-protected phenol (BHQ-OPh). Characterization of the prototropic forms of BHQ-OPh in different solvent environments revealed that the neutral form predominates in acetonitrile and in 1 : 1 acetonitrile/water (pH 5.0), whereas the anionic form predominates in 1 : 1 acetonitrile/PBS (pH 7.4). Both the neutral and anionic forms were significantly populated in 1 : 1 acetonitrile/water. Upon irradiation in acetonitrile the triplet neutral form was observed, whereas the triplet anionic form was detected in 1 : 1 acetonitrile/PBS (pH 7.4). The existence of the triplet tautomeric form of BHQ-OPh in both 1 : 1 acetonitrile/water and 1 : 1 acetonitrile/water (pH 5.0), and the ESPT processes from the neutral to the anionic to the tautomeric forms in the excited state were observed using time-resolved spectroscopy. A reaction mechanism in 1 : 1 acetonitrile/water and 1 : 1 acetonitrile/water (pH 5.0) was proposed based on the spectroscopic and DFT computational results. A comparison of the results for BHQ-OPh with those of BHQ-OAc reveals that the initial prototropic states and photochemical processes are similar. The understanding gained of the initial photo-induced processes of BHQ-based photoremovable protecting groups (PPGs) is useful for the design of new quinolinyl-based PPGs for specialized applications.

Graphical abstract: A spectroscopic study of the excited state proton transfer processes of (8-bromo-7-hydroxyquinolin-2-yl)methyl-protected phenol in aqueous solutions

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Publication details

The article was received on 18 Oct 2016, accepted on 12 Jan 2017 and first published on 13 Jan 2017


Article type: Paper
DOI: 10.1039/C6PP00377J
Citation: Photochem. Photobiol. Sci., 2017,16, 575-584
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    A spectroscopic study of the excited state proton transfer processes of (8-bromo-7-hydroxyquinolin-2-yl)methyl-protected phenol in aqueous solutions

    J. Huang, A. P. Muliawan, J. Ma, M. D. Li, H. K. Chiu, X. Lan, D. Deodato, D. L. Phillips and T. M. Dore, Photochem. Photobiol. Sci., 2017, 16, 575
    DOI: 10.1039/C6PP00377J

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