title: Experimental and theoretical charge density studies of 8-hydroxyquinoline cocrystallized with salicylic acid.
abstract: The experimental electron density distribution (EDD) in 8-hydroxyquinoline cocrystallized with salicylic acid, 1, has been determined from a multipole refinement of high-resolution X-ray diffraction data collected at 100 K. The experimental EDD is compared with theoretical densities resulting from high-level ab initio and BHandH calculations using Atoms in Molecules theory. 1 crystallizes in the triclinic crystal system, and the asymmetric unit consists of a neutral salicylic acid molecule, a salicylate anion, and an 8-hydroxyquinolinium cation exhibiting a number of inter- and intramolecular hydrogen bonds and π-π interactions. Topological analysis reveals that π-π interactions are of the "closed-shell" type, characterized by rather low and flat charge density. In general, the agreement of the topological values (ρ(bcp) and ∇(2)ρ(bcp)) between experiment and theory is good, with mean differences of 0.010 e Å(-3) and 0.036 e Å(-5), respectively. The energetics of the π-π interactions have been estimated, and excellent agreement is observed between the relative energy and the strength of π-stacking derived from the Espinosa approach, with an average difference of only 4.4 kJ mol(-1).
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW, Australia.
authors.forename: Thanh Ha
authors.initials: TH
authors.lastname: Nguyen
authors.forename: Paul W
authors.initials: PW
authors.lastname: Groundwater
authors.forename: James A
authors.initials: JA
authors.lastname: Platts
authors.forename: David E
authors.initials: DE
authors.lastname: Hibbs
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D015125:Oxyquinoline / Q000737:chemistry*; D011789:Quantum Theory; D020156:Salicylic Acid / Q000737:chemistry*
chemical_list: D015125:Oxyquinoline; D020156:Salicylic Acid