The mechanisms of boronate ester formation and fluorescent turn-on in ortho-aminomethylphenylboronic acids

Xiaolong Sun; Brette M. Chapin; Pedro Metola; Byron Collins; Binghe Wang; Tony D. James; Eric V. Anslyn

doi:10.1038/s41557-019-0314-x

The mechanisms of boronate ester formation and fluorescent turn-on in ortho-aminomethylphenylboronic acids

Xiaolong Sun, Brette M. Chapin, Pedro Metola, Byron Collins, Binghe Wang, Tony D. James, Eric V. Anslyn^*

^*Corresponding author for this work

Research output: Contribution to journal › Review article › peer-review

49 Citations (Scopus)

Abstract

ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pK_a of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/boronate ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids.

Original language	English
Pages (from-to)	768-778
Number of pages	11
Journal	Nature chemistry
Volume	11
Issue number	9
Early online date	23 Aug 2019
DOIs	https://doi.org/10.1038/s41557-019-0314-x
Publication status	Published - 01 Sep 2019
Externally published	Yes

Bibliographical note

Funding Information:
The authors gratefully acknowledge financial support for the several years of their work in the area of boronic acids. E.V.A. is grateful to the NSF (CHE-0716049, CHE-1212971), the Welch Foundation (F-1151) and the Welch Regents Chair (F-0046). B.W. acknowledges the Georgia Research Alliance, Georgia Cancer Coalition and the NIH throughout the years for their support of the boronic acid-relate projects (GM084933, CA159567, DK55062, CA88343, NO1-CO-27184, CA113917, CA123329 and GM086925). T.D.J. wishes to thank the Royal Society for a Wolfson Research Merit Award.

Publisher Copyright:
© 2019, The Author(s), under exclusive licence to Springer Nature Limited.

Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.

ASJC Scopus subject areas

Chemistry(all)
Chemical Engineering(all)

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Cite this

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title = "The mechanisms of boronate ester formation and fluorescent turn-on in ortho-aminomethylphenylboronic acids",

abstract = "ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pKa of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/boronate ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids.",

author = "Xiaolong Sun and Chapin, {Brette M.} and Pedro Metola and Byron Collins and Binghe Wang and James, {Tony D.} and Anslyn, {Eric V.}",

note = "Funding Information: The authors gratefully acknowledge financial support for the several years of their work in the area of boronic acids. E.V.A. is grateful to the NSF (CHE-0716049, CHE-1212971), the Welch Foundation (F-1151) and the Welch Regents Chair (F-0046). B.W. acknowledges the Georgia Research Alliance, Georgia Cancer Coalition and the NIH throughout the years for their support of the boronic acid-relate projects (GM084933, CA159567, DK55062, CA88343, NO1-CO-27184, CA113917, CA123329 and GM086925). T.D.J. wishes to thank the Royal Society for a Wolfson Research Merit Award. Publisher Copyright: {\textcopyright} 2019, The Author(s), under exclusive licence to Springer Nature Limited. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.",

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N2 - ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pKa of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/boronate ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids.

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The mechanisms of boronate ester formation and fluorescent turn-on in ortho-aminomethylphenylboronic acids

Abstract

Bibliographical note

ASJC Scopus subject areas

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