title: NO3- anions can act as Lewis acid in the solid state.
abstract: Identifying electron donating and accepting moieties is crucial to understanding molecular aggregation, which is of pivotal significance to biology. Anions such as NO3-are typical electron donors. However, computations predict that the charge distribution of NO3-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.
authors.affiliation: Department of Chemistry, Universitat de les Illes Balears, Carretera de Valldemossa km 7.5, 07122 Palma, Baleares, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Bauzá
authors.affiliation: Department of Chemistry, Universitat de les Illes Balears, Carretera de Valldemossa km 7.5, 07122 Palma, Baleares, Spain.
authors.forename: Antonio
authors.identifier: 0000-0001-7840-2139
authors.initials: A
authors.lastname: Frontera
authors.affiliation: Faculteit der Natuurwetenschappen, Wiskunde en Informatica, van 't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.|School of Chemistry, Faculty of Science, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
authors.forename: Tiddo J
authors.identifier: 0000-0002-9086-1343
authors.initials: TJ
authors.lastname: Mooibroek