On–off allosteric control of a bifunctional catalyst
A Pt(II) weak-link tweezer and a sulfonate regulator switch a squaramide–amine co-catalyst fully on or off in situ.
Source
A concerted two-prong approach to the <i>in situ</i> allosteric regulation of bifunctional catalysis
Study at a glance
- Design
- Animal / in-vitro — Pt(II) weak-link tweezer with chloride toggling, 1H NMR binding, and timed Michael addition
- N
- Multiple catalyst states and kinetic runs rather than a single sample N
- Population
- In situ bifunctional squaramide–amine catalysis in organic solvent
- Outcome
- Fully closed Na+ complex binds DMA and catalyzes nearly quantitative Michael addition; chloride switching turns activity off
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Inspect source passages
On–off allosteric control of a bifunctional catalyst
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Closed-state TOF is 2.69 × 10−4 s−1 with nearly quantitative conversion.
As can be seen in , FC 2 gives the product with nearly quantitative conversion (TOF = 2.69 × 10 –4 s –1 ).
What architecture enables reversible allosteric switching here?
our group has developed the weak-link approach (WLA) to supramolecular coordination chemistry, which is a powerful tool for the synthesis of multi-component catalytically active complexes
What they did
Authors assembled a heteroligated Pt(II) tweezer with a squaramide–tertiary amine ligand and a sodium sulfonate hydrogen-bond acceptor, switched it between semi-open and fully closed states with chloride, measured DMA binding by 1H NMR, and timed the Michael addition of nitroethane to β-nitrostyrene.
What they found
The fully closed Na+ complex binds DMA strongly (Ka ≈ 75 558 M−1) while the semi-open state shows no recognition. Closed-state catalysis gives nearly quantitative conversion (TOF = 2.69 × 10−4 s−1), and chloride toggling reverses activity. Embedding the catalyst in the WLA scaffold improves activity versus free ligand.
The limits
What it doesn't show
Scope beyond a few conjugate additions is proposed rather than demonstrated at scale; polymer-length control of lactide ROP is suggested but not shown here.
Key terms
- Weak-link approach (WLA)
- Hemilabile P,X ligands on d8 metals that open or close a supramolecular catalyst with chemical effectors such as Cl−.
- Hydrogen-bond-donating (HBD) catalyst
- A squaramide that activates electrophiles by dual hydrogen bonds.
- Fully closed (FC) vs semi-open (SO)
- Chelated rigid vs flexible P-only states of the Pt(II) tweezer.
- Bifunctional HBD–Lewis base
- Co-catalyst that activates both electrophile (HBD) and nucleophile (amine).
- Allosteric regulation
- Activity switched by a remote coordination change rather than by modifying the catalytic site covalently.
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Quiz yourself
The off state of this tweezer catalyst is the:
Common questions
What turns the catalyst off?
The semi-open state lets the sulfonate hydrogen-bond to the squaramide so substrate cannot bind.
What model reaction was timed?
Michael addition of nitroethane to β-nitrostyrene.
Why does Na+ matter in the closed state?
The cation screens the sulfonate so intermolecular ligand–ligand association is minimized.
Can you switch in situ?
Yes: add and abstract Cl− to toggle FC and SO.
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