A re-investigation of [Fe(l-cysteinate)2(CO)2]2−: an example of non-heme CO coordination of possible relevance to CO binding to ion channel receptors

Abstract

[Fe(L-cysteinate)₂(CO)₂]²⁻ is a CO releasing molecule which has low cytotoxicity to RAW264.7 macrophages. It provides an example of CO binding using ligands available to ion channels which use CO as a signalling molecule in the absence of heme. Previous work has shown that this compound consists of five isomers and it was proposed that the two isomers with trans-dicarbonyls are dominant. In this work the isomers are re-assigned and shown to be capable of releasing CO, albeit too slowly to act as a signalling receptor. It is shown that by linking the two L-cysteines together to form [Fe(SCH₂CH{CO₂H}NHCH₂)₂(CO)₂], only one isomer is isolated.