Preparation of Dicarbonyl Iron Compounds with a Bidentate Phosphine and Their CO Release Behaviors upon Irradiation

CO-releasing molecule (CORM) facilitates the precise delivery of CO in the human body. To improve the stability of CORM, iron dicarbonyl compounds bearing a bidentate phosphine ligand, [Fe(cis-CO)(2)(dppe)I-2] (1, dppe= 1, 2. bis(diphenylphosphino)ethane), [Fe(cis - CO)(2)(dppp)I-2] (2, dppp=1, 3. bis(diphenylphosphino)propane), and [Fe(trans-CO)(2){Ph2PN(cyclohexyl) PPh2}I-2] (3) were prepared by reacting of the precursor [Fe(CO)(4)I-2] with the phosphine ligands via coordination substitution reactions. The compounds were structurally characterized by means of FT-IR, UV-Vis, NMR, elemental analysis, and single. crystal X-ray diffraction (for compounds 2 and 3). Moreover, CO-releasing behaviors of compounds 1-3 in DMSO were investigated by FT-IR to evaluate their application as a potential CORM. As demonstrated by the FT-IR spectroscopical monitoring, these compounds exhibited good stability in the dark but were easily decomposed to release CO upon irradiation of visible lights (red, green, and blue lights). Their degradation with CO release depends on the energy of the light source and the chemical structures of the compounds. Moreover, isomerization transformations of compounds 1 and 2 from cis- to trans-dicarbonyl configuration were confirmed by the FT-IR spectroscopy under the green and blue lights. However, the red light did not trigger the configuration conversion due to its low energy. Among them, the trans-dicarbonyl compound 3 exhibited the best stability upon the irradiation, which adopted a zero-order model for the photo-induced CO release. CCDC: 2154703, 2; 2154704, 3.