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Issue 11, 2016
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A concerted two-prong approach to the in situ allosteric regulation of bifunctional catalysis

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Abstract

Herein, we report the reversible in situ “on–off” allosteric regulation of hydrogen-bond-donating (HBD)–Lewis base co-catalytic activity via a concerted two-prong methodology entailing cooperative acid–base chemistry and a structurally addressable coordination complex. Specifically, a heteroligated Pt(II) weak-link approach (WLA) tweezer complex containing both a hemilabile squaramide–piperidine-based catalytic ligand and a sodium sulfonate hydrogen-bond-accepting (HBA) ligand was synthesized. Due to the hemilabile nature of the catalyst-containing ligand, the heteroligated complex can be reversibly toggled in situ between a flexible, semi-open state and a rigid, fully closed state upon the addition of elemental ion cues. 1H NMR spectroscopy titration studies show that in the semi-open state interligand hydrogen-bonding prevents substrate recognition by the squaramide unit, while in the fully closed state ligand–ligand interactions are prevented. This results in a catalytically active closed state, whereas in the semi-open state, when the piperidine tertiary amine is deliberately protonated, no catalytic activity is observed. Reversible interconversion between the active fully closed state and the dormant protonated semi-open state is achieved in the presence of substrate upon the concerted addition and abstraction of both a proton and a coordinating elemental anion. In this work, allosteric regulation of catalytic activity is demonstrated for both the Michael addition of nitroethane to β-nitrostyrene and the ring-opening of L-(−)-lactide. Taken together, this work details a potentially generalizable platform for the “on–off” allosteric regulation of a family of HBD–Lewis base co-catalysts capable of catalyzing a broad scope of reactions, including the living ring-opening polymerization of cyclic esters.

Graphical abstract: A concerted two-prong approach to the in situ allosteric regulation of bifunctional catalysis

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Supplementary files

Article information


Submitted
01 Apr 2016
Accepted
08 Jul 2016
First published
18 Jul 2016

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2016,7, 6674-6683
Article type
Edge Article

A concerted two-prong approach to the in situ allosteric regulation of bifunctional catalysis

C. M. McGuirk, J. Mendez-Arroyo, A. I. d'Aquino, C. L. Stern, Y. Liu and C. A. Mirkin, Chem. Sci., 2016, 7, 6674 DOI: 10.1039/C6SC01454B

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