NO<sub>3</sub>- anions can act as Lewis acid in the solid state.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28220788.
- Also identified by DOI 10.1038/ncomms14522 and PMC identifier 5321794.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Identifying electron donating and accepting moieties is crucial to understanding molecular aggregation, which is of pivotal significance to biology. Anions such as NO<sub>3</sub><sup>-</sup> are typical electron donors. However, computations predict that the charge distribution of NO<sub>3</sub><sup>-</sup> is anisotropic and minimal on nitrogen. Here we show that when the nitrate's charge is sufficiently dampened by resonating over a larger area, a Lewis acidic site emerges on nitrogen that can interact favourably with electron rich partners. Surveys of the Cambridge Structural Database and Protein Data Bank reveal geometric preferences of some oxygen and sulfur containing entities around a nitrate anion that are consistent with this 'π-hole bonding' geometry. Computations reveal donor-acceptor orbital interactions that confirm the counterintuitive Lewis π-acidity of nitrate.