Premium
Sodium Salicylate: An In‐Depth Thermal and Photophysical Study
Author(s) -
Spielberg Eike T.,
Campbell Paul S.,
Szeto Kai C.,
Mallick Bert,
Schaumann Julian,
Mudring AnjaVerena
Publication year - 2018
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.201803045
Subject(s) - chemistry , absorption (acoustics) , absorption spectroscopy , carboxylate , single crystal , van der waals force , cyclohexane , excited state , spectroscopy , ionic bonding , photochemistry , crystallography , analytical chemistry (journal) , materials science , ion , molecule , organic chemistry , physics , quantum mechanics , nuclear physics , composite material
Sodium salicylate (2‐hydroxybenzoate) has been fully characterised by single‐crystal X‐ray diffraction (SCXRD), thermogravimetric analysis in combination with in operando FTIR spectroscopy and GC‐MS, as well as by UV/Vis absorption and photoluminescence spectroscopy backed up by DFT calculations. SCXRD revealed a layered crystal structure composed of ionic sheets formed by Na + –O contacts sandwiched between π‐stacked aromatic rings of the salicylate anion oriented perpendicular to the layer plane. Only weak van der Waals interactions hold the individual sheets together. No solid/solid or solid/liquid phase transitions were observed upon heating, but a three‐step decomposition was observed, with the first onset at 245 °C corresponding to concomitant release of CO 2 and phenol. The UV/Vis absorption spectra show temperature‐dependent absorption bands at around 305 and/or 345 nm, which according to DFT calculations correspond to the absorption of the carboxylate or phenolate proton transfer species, respectively. In solution, indications of the phenolate species are found only in a very apolar solvent (cyclohexane). Because of excited‐state relaxation, emission always occurs from the phenolate structure, which explains the large Stokes shift.