title: Chemical Speciation and Bond Lengths of Organic Solutes by Core-Level Spectroscopy: pH and Solvent Influence on p-Aminobenzoic Acid.
abstract: Through X-ray absorption and emission spectroscopies, the chemical, electronic and structural properties of organic species in solution can be observed. Near-edge X-ray absorption fine structure (NEXAFS) and resonant inelastic X-ray scattering (RIXS) measurements at the nitrogen K-edge of para-aminobenzoic acid reveal both pH- and solvent-dependent variations in the ionisation potential (IP), 1s→π* resonances and HOMO-LUMO gap. These changes unequivocally identify the chemical species (neutral, cationic or anionic) present in solution. It is shown how this incisive chemical state sensitivity is further enhanced by the possibility of quantitative bond length determination, based on the analysis of chemical shifts in IPs and σ* shape resonances in the NEXAFS spectra. This provides experimental access to detecting even minor variations in the molecular structure of solutes in solution, thereby providing an avenue to examining computational predictions of solute properties and solute-solvent interactions.
authors: School of Chemical Engineering and Analytical Science, School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL (UK).
authors: Joanna S
authors: JS
authors: Stevens
authors: Adrian
authors: A
authors: Gainar
authors: Edlira
authors: E
authors: Suljoti
authors: Jie
authors: J
authors: Xiao
authors: Ronny
authors: R
authors: Golnak
authors: Emad F
authors: EF
authors: Aziz
authors: Sven L M
authors: SL
authors: Schroeder
keywords: X-ray absorption spectroscopy; X-ray scattering; ionization potentials; liquids; speciation