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Flexibility Coexists with Shape-Persistence in Cyanostar Macrocycles
- Source :
- Journal of the American Chemical Society. 138:4843-4851
- Publication Year :
- 2016
- Publisher :
- American Chemical Society (ACS), 2016.
-
Abstract
- Shape-persistent macrocycles are attractive functional targets for synthesis, molecular recognition, and hierarchical self-assembly. Such macrocycles are noncollapsible and geometrically well-defined, and they are traditionally characterized by having repeat units and low conformational flexibility. Here, we find it necessary to refine these ideas in the face of highly flexible yet shape-persistent macrocycles. A molecule is shape-persistent if it has a small change in shape when perturbed by external stimuli (e.g., heat, light, and redox chemistry). In support of this idea, we provide the first examination of the relationships between a macrocycle's shape persistence, its conformational space, and the resulting functions. We do this with a star-shaped macrocycle called cyanostar that is flexible as well as being shape-persistent. We employed molecular dynamics (MD), density functional theory (DFT), and NMR experiments. Considering a thermal bath as a stimulus, we found a single macrocycle has 332 accessible conformers with olefins undergoing rapid interconversion by up-down and in-out motions on short time scales (0.2 ns). These many interconverting conformations classify single cyanostars as flexible. To determine and confirm that cyanostars are shape-persistent, we show that they have a high 87% shape similarity across these conformations. To further test the idea, we use the binding of diglyme to the single macrocycle as guest-induced stimulation. This guest has almost no effect on the conformational space. However, formation of a 2:1 sandwich complex involving two macrocycles enhances rigidity and dramatically shifts the conformer distribution toward perfect bowls. Overall, the present study expands the scope of shape-persistent macrocycles to include flexible macrocycles if, and only if, their conformers have similar shapes.
- Subjects :
- Macrocyclic Compounds
Magnetic Resonance Spectroscopy
010405 organic chemistry
Chemistry
Molecular Conformation
General Chemistry
Molecular Dynamics Simulation
010402 general chemistry
01 natural sciences
Biochemistry
Article
Catalysis
0104 chemical sciences
Molecular dynamics
Colloid and Surface Chemistry
Molecular recognition
Models, Chemical
Computational chemistry
Chemical physics
Thermodynamics
Molecule
Density functional theory
Subjects
Details
- ISSN :
- 15205126 and 00027863
- Volume :
- 138
- Database :
- OpenAIRE
- Journal :
- Journal of the American Chemical Society
- Accession number :
- edsair.doi.dedup.....73f3f7398a737c872bde407219762109