Photosensitive iron(II)-based CO-releasing molecules (CORMs) with vicinal amino and diphenylphosphino substituted chelating ligands

The reactions of [Fe(H2O)6] [BF4]2 with aminoethyl-diphenylphosphane and 2-(diphenylphosphino)aniline lead to the formation of trans-[Fe(NC-Me)2(H2NCH2CH2PPh2)2] [BF4]2 (1a) and trans-[Fe(NC-Me)2(H2NC6H4-2-PPh2)2] [BF4]2 (1b), respectively. One acetonitrile ligand can be substituted by CO yielding [Fe(CO)(NC-Me)(H2NCH2CH2PPh2)2] [BF4]2 (2a, CORM-P1) and [Fe(CO)(NC-Me)(H2NC6H4-2-PPh2)2] [BF4]2 (2b, CORM-P2). Upon irradiation with visible light, CO is liberated making especially 2a a promising photo-CORM whereas for 2b a slow and incomplete CO release is observed.

Graphical abstractCO represents an important signaling molecule with a huge therapeutic potential. Here we present the iron(II) complex [Fe(CO)(NC-Me)(H2NCH2CH2PPh2)2] [BF4]2 (2a, CORM-P1) that liberates CO upon irradiation with visible light, being a promising photo-CORM.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► [Fe(CO)(NC-Me)(H2NCH2CH2PPh2)2] [BF4]2 (CORM-P1) acts as an efficient photo-CORM upon irradiation with visible light. ► In trans-bis(acetonitrile)iron(II) complexes only one acetonitrile is substituted by carbon monoxide yielding CORM-P1. ► Neither solvent nor dithionite nor the concentration influence light-induced CO-release from CORM-P1. ► Carbon monoxide release of photo-CORMs can be determined faithfully with a standard myoglobin assay at 422 nm.