The Prospect of Selective Recognition of Nerve Agents with Modular Basket-like Hosts. A Structure-Activity Study of the Entrapment of a Series of Organophosphonates in Aqueous Media
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Taha, Hashem A.
Yoder, Ryan J.
Hadad, Christopher M.
Bađić, Jovica D.
Article (Published version)
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We designed, prepared, and characterized three cup-shaped cavitands 1-3 for trapping organophosphonates (O=PR(OR')(2), 118-197 A3) whose shape and size correspond to G-type chemical warfare agents (132-186 A(3)). With the assistance of computational (molecular dynamics) and experimental CH NMR spectroscopy) methods, we found that host [1-H-3](3+) orients its protonated histamine residues at the rim outside the cavity, in bulk water. In this unfolded form, the cavitand traps a series of organophosphonates 5-13 (K-app = 87 +/- 1 to 321 +/- 6 M-1 at 298.0 K), thereby placing the P-CH3 functional group in the inner space of the host. A comparison of experimental and computed H-1 NMR chemical shifts of both hosts and guests allowed us to derive structure activity relationships and deduce that, upon the complexation, the more sizable P OR functional groups in guests drive organophosphonates to the northern portion of the basket [1-H-3](3+). This, in turn, causes a displacement of the guest's... P-CH3 group and a contraction of the cupshaped scaffold. The proposed induced-fit model of the recognition is important for turning these modular hosts into useful receptors capable of a selective detection/degradation of organophosphorus nerve agents.
Source:Journal of Physical Chemistry. Part B: Condensed Matter, Materials, Surfaces, Interfaces and Biophys, 2013, 117, 11, 3240-3249
- Amer Chemical Soc, Washington
- Department of Defense, Defense Threat Reduction Agency [HDTRA1-11-1-0042]
- National Science Foundation [CHE-1012146]
- Supplementary material: http://cherry.chem.bg.ac.rs/handle/123456789/3556