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Chemical Speciation and Bond Lengths of Organic Solutes by Core‐Level Spectroscopy: pH and Solvent Influence on p ‐Aminobenzoic Acid
Author(s) -
Stevens Joanna S.,
Gainar Adrian,
Suljoti Edlira,
Xiao Jie,
Golnak Ronny,
Aziz Emad F.,
Schroeder Sven L. M.
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405635
Subject(s) - xanes , chemistry , solvent , absorption spectroscopy , absorption (acoustics) , bond length , spectroscopy , chemical shift , homo/lumo , x ray absorption spectroscopy , chemical state , chemical bond , analytical chemistry (journal) , molecule , materials science , organic chemistry , x ray photoelectron spectroscopy , chemical engineering , physics , quantum mechanics , engineering , composite material
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.