Synthesis and Assessment of CO‐Release Capacity of Manganese Carbonyl Complexes Derived from Rigid α‐Diimine ­Ligands of Varied Complexity

Abstract

Four manganese carbonyl complexes of the type [MnBr(CO)3(NˆN)] (NˆN = α-diimine ligands) namely [MnBr(CO)3(bpy)] (1), [MnBr(CO)3(phen)] (2), [MnBr(CO)3(dafo)] (3) and [MnBr(CO)3(pyzphen)] (4) (where bpy = bipyridine, phen = 1,10-phenanthroline, dafo = 4,5-diazafluoren-9-one and pyzphen = pyrazino[2,3-f][1,10]-phenanthroline) have been synthesized and structurally characterized. These four complexes containing the fac-[Mn(CO)3] motif release CO upon illumination with low power visible and UV light. The CO release rates and the absorption maxima of the complexes are however very similar despite systematic increase in structural complexity in the rigid α–diimine ligand frames. This is quite in contrary to manganese carbonyl complexes derived from α–diimine ligands in which at least one of the imine functions is not part of the rigid ring systems. Results of this study will provide help in the future design of ligand frames suitable for the syntheses of photoCORMs to deliver CO to biological targets under the control of light.

Light-triggered CO delivery by a water-soluble and biocompatible manganese photoCORM

“…Since electronic absorption spectroscopy of the photolyzed solution indicated deligation of pyTAm from complex 2 , the similarity in these two EPR patterns suggested a solvated Mn(II) species in the photolyzed product along with the free ligand (pyTAm). Collectively the photo behavior of 2 is consistent with our previous findings 17,22 as well with other water-soluble manganese photoCORMs reported recently. 34 …”

“…21 In a recent work we have isolated a family of manganese carbonyl complexes derived from α-diimine ligands and critically investigated the correlation between ligand structure and CO release property. 22 Results of these studies now clearly demonstrate that among photoCORMs bearing α-diimine ligands, complexes in which one of the imine functions is not a part of rigid ring system exhibit superior light absorption and faster CO release compared to complexes in which both imine functions are part of a rigid ring framework. This finding has led us to select the former type of α-diimine ligands for the present study.…”

Light Response of Three Water-Soluble MnI PhotoCORMs: Spectroscopic Features and CO Release Investigation

“…One way to overcome these disadvantages is the use of molecular carriers, which act as prodrugs and can transport carbon monoxide into the organism in a controlled manner, only releasing CO under the influence of a specific trigger. [11][12][13] Several carriers based on organic compounds 14,15 or using transition metals, such as tungsten, molybdenum, iron, ruthenium, rhenium and manganese, [16][17][18][19][20][21] have been used to deliver CO to the organism, the latter being preferred due to the high flexibility in terms of the properties obtained from both the metal center and the organic framework. 13 The correct selection of these properties is essential in the development of new metal carbonyl compounds (MCCs), 12 which should preferentially be water soluble.…”

Dual Targeting of the p38 MAPK-HO-1 Axis and cIAP1/XIAP by Demethoxycurcumin Triggers Caspase-Mediated Apoptotic Cell Death in Oral Squamous Cell Carcinoma Cells

“…Low doses of CO were reported to prevent apoptosis in different cell models [48]. In contrast, an moderately high concentration of CO exerts pro-apoptotic effects toward several cell types, including cancer cells [49]. The production of CO catalyzed by HO-1 was reported to further induce HO-1 expression in cancer cells [44], and this positive feedback loop can promote an high amount of CO production.…”