Structures of the 2-nitrophenol alkali complexes in solution and the solid state

Reichelt, H; Faunce, C; Paradies, HH

Abstract

The materials studied in this investigation were aqueous solutions (0.02-25.0 mM) of the salts of alkali metal ion (Me+) and 2-nitrophenol (2-NP). In the investigation, small-angle X-ray scattering, wide-angle X-ray scattering, and membrane-pressure osmometry were used to study the 2-NP-Me+ molecular salt structures and the onset of crystallization as a function of concentration and temperature. The experimental methods used to examine the 2-NP-Me+ molecular salt complexes provided corroborative evidence for the existence of spherical clusters with hydrodynamic diameters between ∼12 Å (Li) and 14 Å (Cs). Guinier plots of the zero-angle scattering peak were characteristic of the scattering from lamellae-like shapes with thicknesses of ∼290 Å. Tetramer and pentamer 2-NP-Me+ molecular clusters for Me+ = Li, Na, K, and Rb were assembled from four or five 2-NP molecules bound to a central alkali metal ion. The coordination symmetry around the six coordinated Li+, Na+, and K+ ions was that of a trigonal prism (D3h), with an octahedral arrangement (D2h). The Rb+ also revealed six-coordinate geometry and the central Rb+ ion adopted an octahedral arrangement (D2h). The eight-coordinated Cs+ ions with six 2-NP ligands were characteristic of a square antiprism (D4d). The square antiprism was the outcome of leaving two o-nitro groups and two phenolic oxygens being left intermolecularly uncoordinated to the Cs+ ion. The 2-NP residues were strictly planar and contained short non-bonded intramolecular distances. van der Waals forces were present between the adjacently stacked phenyl rings. No water molecules were involved as ligands for any of the 2-nitrophenol-Me+ complexes.

Citation

Reichelt, H., Faunce, C., & Paradies, H. Structures of the 2-nitrophenol alkali complexes in solution and the solid state. Journal of Chemical Physics, 143(4), 044307. https://doi.org/10.1063/1.4927140

• Journal Article Type: Article
• Deposit Date: Nov 28, 2016
• Journal: Journal of Chemical Physics
• Print ISSN: 0021-9606
• Publisher: AIP Publishing
• Volume: 143
• Issue: 4
• Pages: 044307
• DOI: https://doi.org/10.1063/1.4927140
• Publisher URL: http://dx.doi.org/10.1063/1.4927140