Diversity and design of metal-based carbon monoxide-releasing molecules (CO-RMs) in aqueous systems: revealing the essential trends

Abstract

The CO-releasing ability of a diverse library of primary metal carbonyl complexes has been assessed using a deoxymyoglobin-carbonmonoxymyglobin assay. A wide spectrum of rates for the CO-release process was observed in aqueous systems. For octahedral d(6) complexes, the rate was found to decrease in the sequence FeI(2)(CO)(4) > [NEt(4)][V(CO)(6)] > MnBr(CO)(5) > Cr(CO)(6) implying that CO-release is not controlled by the metal-carbon bond strengths. Within the series, [NEt(4)][MX(CO)(5)] (M = Cr, Mo, W; X =Cl, Br, I), the rate of CO-release was found to decrease down the group (Cr > Mo > W), whilst within the chromium series a similar trend was observed for the halide (Cl > Br > I). The d(4) complexes [NEt(4)][MI(3)(CO)(4)] (M = Mo, W) exhibit faster release than their d(6) congeners. A mechanistic investigation into the [NEt(4)][MX(CO)(5)] series revealed the intermediacy of [[M(CO)(5)](2)(mu-X)](-) in the CO-release process and that the hydrolysis of the M-X bond, rather than the intrinsic strength of M-CO bonds, controls the rate of CO-release in aqueous systems.

Tricarbonylmanganese(I) and –rhenium(I) Complexes of Imidazol‐Based Phosphane Ligands: Influence of the Substitution Pattern on the CO Release Properties

“…[15,16] Although the number of studies on carbonylmetal CORMs has significantly grown over recent years, very few systematic studies of the factors determining the mechanism of CO release have been carried out. [17,18] Here, we report on the synthesis and characterization of a series of Mn(CO) 3 and Re(CO) 3 complexes of different imidazol-2-yl and imidazol-4(5)-ylphosphane ligands. Since the introduction of the tris(pyrazolyl)boranes (tp) by Trofimenko, scorpionate ligands containing N-donor atoms have been intensively studied and are well known as ligands for complexes used in biomedical applications.…”

Live-Fibroblast IR Imaging of a Cytoprotective PhotoCORM Activated with Visible Light

“…To date the majority of CORMs are transition metal (TM) carbonyl complexes which under different stimuli are able to deliver CO to diseased or inflamed tissues in order to initiate and promote therapeutic effects at the site of disease. CO release in these molecules may be triggered by different strategies which include simple CO dissociation [4][5][6] , redox or ligand exchange mediated processes [7][8][9][10][11][12] , enzymatic triggering 13,14 or the use of electromagnetic radiation. [15][16][17] In general, at present, CORMs are not designed to target a specific receptor or intracellular target and their potential utility is credited to their fundamental ability to liberate CO.…”

O2-Dependent Aliphatic Carbon−Carbon Bond Cleavage Reactivity in a Ni(II) Enolate Complex Having a Hydrogen Bond Donor Microenvironment; Comparison with a Hydrophobic Analogue

“…As these factors are related to several diseases, recent studies have focused on efforts toward the development of CO-releasing compounds for use as therapeutic agents 4. The majority of the chemical compounds tested so far have been transition metal carbonyl species5, although a main group CO-releasing compound (Na 2 [H 3 BCO 2 ]) has been recently reported 4. We are interested in the CO release properties of acireductones and flavonolates, both of which possess three consecutive carbon centers having an oxygen substitutent.…”