Light- or oxidation-triggered CO release from [Mn^I(CO)₃(κ³-L)] complexes: reaction intermediates and a new synthetic route to [MnIII/IV2(μ-O)₂(L)₂] compounds

Abstract

The reaction products and intermediates of the three CO-releasing manganese(i) coordination compounds [Mn(tpm)(CO)], [Mn(bpza)(CO)] and [Mn(tpa)(CO)] were analysed by combining IR-spectroscopy, electrochemical measurements and single-crystal XRD. The intermediate formation of manganese(i) biscarbonyl compounds and the rather facile oxidation of these species were identified as key reaction steps that accompany CO liberation. For the use of [Mn(CO)] complexes as light-triggered CO sources, the results indicate that in this case photo- and redox-chemistry seem to be strongly coupled which could be important and potentially even useful in the pharmacological context. Additionally, one has to be aware of the fact that [Mn(κ-L)(solv)] complexes, the primary reaction products after CO substitution, are able to bind to proteins, which was demonstrated using bovine serum albumin as a model. And finally it could be shown that the CO-release reactions can be used as a new synthetic route to prepare multinuclear μ-oxido-bridged manganese complexes: the mixed-valence compound [Mn(μ-O)(tpa)] could be prepared in a single step from [Mn(tpa)(CO)]via photo- or electrochemically induced CO substitution.

Near-Infrared and Visible Photoactivation to Uncage Carbon Monoxide from an Aqueous-Soluble PhotoCORM

“…The Mn-N bond lengths are ~0.2 Å longer than those found in h 3 -terpyridine Mn(I) complexes but close to those found for 3 and Mn(II) h 3 -tris(1-pyrazolyl)methane complexes. 36,37 Thus, the first stage photoreaction for solutions of complex 2 in DMSO, ethanol or water involves the labilization of one CO to give primarily a dicarbonyl complex, apparently the tricoordinate TPYOH complex Mn(CO)2(h 3 -TPYOH)X. The photochemical second stage, which is accelerated in aerobic media also results in CO release and, eventually, the formation of Mn(II)-TPYOH complexes (Scheme 3).…”

RuII–Carbonyl photoCORMs with N,N‐Benzimidazole Bidentate Ligands: Spectroscopic, Lysozyme Binding Affinity, and Biological Activity Evaluation

“…In contrast to the new generation of fac ‐Mn(CO) 3 containing photoCORMs that release CO in visible light (468–660 nm), most of Ru II –carbonyl complexes are either inert or liberate CO upon exposure to UV light . This may be related to the straightforward oxidation of Mn I into Mn II species . New strategies have been applied to increase the sensitivity of Ru II CORMs towards visible light .…”

Spectroscopic and DFT studies of photoactivatable Mn(I) tricarbonyl complexes

“…The mechanism of the CO photo release from fac ‐Mn (CO) 3 compounds and the formation of the intermediate Mn I (CO) 2 during the photolysis process is now well‐established . While one CO molecule is photometrically released according to the data obtained from few to second transient absorption UV pump/mid‐IR prob spectroscopy study, the rest of CO molecules require an additional dark process .…”