Effect of the chemical structures of iron complexes on the solubilities in supercritical carbon dioxide

The solubilities of iron(II) cyclopentadienyl (Fe(cp)2), iron(II) acetylacetonate (Fe(acac)2) and iron(III) acetylacetonate (Fe(acac)3) in supercritical carbon dioxide (scCO2) were measured at 313 and 333 K to obtain new experimental data on the representative iron complexes and to investigate the effect of the ligand structures on the solubilities of the iron complexes. Solubility was measured using a semi-batch flow method. The measured solubilities of Fe(cp)2 and Fe(acac)3 in scCO2 were compared with the literature values to check the validity of the experimental method. Fe(cp)2 showed the highest solubility among the three iron complexes measured, followed by Fe(acac)2 and Fe(acac)3. The σ-profile and apparent chemical potential of each iron complex were estimated using the quantum chemical calculation and COSMO-RS to examine the theoretical relationships between the chemical structures of the iron complexes and the solubilities in scCO2 from the viewpoint of the affinity between molecules.

► The solubilities of three iron complexes in supercritical CO2 were measured.
► Measurements were carried out at 313 and 333 K.
► The order of the solubilities were Fe(cp)2 > Fe(acac)2 > Fe(acac)3.
► The effect of the molecular structure on the solubility was discussed using COSMO-RS.