CH···anion bonds that template zinc molecular knots
Weak C–H···anion contacts in water/methanol steer a Zn(II) dynamic library toward a trefoil knot that binds two bromides in its cavity.
Source
[C-H···anion] interactions mediate the templation and anion binding properties of topologically non-trivial metal-organic structures in aqueous solutions
Study at a glance
- Design
- Other — Zn(II)-templated DFP/DAB assemblies (catenane/knot/link) with aqueous anion-binding studies
- N
- Supramolecular synthesis and binding — no sample N
- Population
- DFP–DAB–Zn(II) interlocked assemblies in MeOD/D2O
- Outcome
- CH···anion-mediated topology selection and aqueous anion binding
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
CH···anion bonds that template zinc molecular knots
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
The TK6+ dipole is 2.77 D in the gas phase and 4.97 D in water.
the helical arrangement of the three pyridyl units of the supramolecular assembly results in a sizeable dipole moment directed along the C 3 axis, which at the B3LYP/6-31G(d) level amounts to 2.77 D in the gas-phase and 4.97 D in aqueous solution ().
The TK6+ cavity is ~130 Å3, suited to two anions of radius ≤2.5 Å.
Thus, assuming the simultaneous binding of two anions, the size of the TK 6+ cavity (∼130 Å 3 ) is suited for the recognition of two anions of relatively small radius (≤2.5 Å).
What they did
Authors assembled DFP + DAB with Zn(II), used anion templation and temperature to bias [2]catenane, trefoil knot TK6+ and Solomon link, solved TK6+ crystals with two bromides, computed ESP/dipole, and studied aqueous anion binding by NMR.
What they found
CH···anion interactions in MeOD/D2O mediate topology. Solid-state TK6+ holds two bromides via bipyridinyl C–H hydrogen bonds. Cavity ~130 Å3 fits two anions ≤2.5 Å. DFT dipole is 2.77 D (gas) and 4.97 D (water). TK6+ still binds anions in D2O.
The limits
What it doesn't show
A full aqueous Kd table for every anion under physiological salt is incomplete; TFA association mode could not be assigned by HOESY.
Key terms
- Trefoil knot (TK6+)
- Zn(II)-templated three-crossing knot that binds anions in its central cavity.
- CH···anion interaction
- Weak hydrogen bond from an aromatic C–H (bipyridine) to Br− or similar.
- [2]Catenane / Solomon link
- Other members of the same imine/Zn dynamic library.
- Anion templation
- Anions that bias which topology forms from the dynamic library.
- DFP / DAB ligands
- Diformylpyridine and diamino-bipyridine building blocks.
Flashcards
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Quiz yourself
Templating interaction in MeOD/D2O:
Common questions
What weak interaction templates the knot?
CH···anion contacts in MeOD/D2O.
How many bromides in the crystal cavity?
Two.
Cavity volume?
About 130 Å3.
Does binding survive in D2O?
Yes for TK6+.
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