Manganese Carbonyl Complexes Research Articles

Correction: Time-resolved infra-red spectroscopy reveals competitive water and dinitrogen coordination to a manganese(i) carbonyl complex.

Correction for 'Time-resolved infra-red spectroscopy reveals competitive water and dinitrogen coordination to a manganese(i) carbonyl complex' by Jonathan B. Eastwood et al., Dalton Trans., 2020, DOI: .

Time-resolved infra-red spectroscopy reveals competitive water and dinitrogen coordination to a manganese(i) carbonyl complex.

Time-resolved infra-red (TRIR) spectroscopy has been used to demonstrate that photolysis of [Mn(C^N)(CO)4] (C^N = bis-(4-methoxyphenyl)methanimine) in heptane solution results in ultra-fast CO dissociation and ultimate formation of a rare Mn-containing dinitrogen complex fac-[Mn(C^N)(CO)3(N2)] with a diagnostic stretching mode for a terminal-bound N[triple bond, length as m-dash]N ligand at 2249 cm-1. An isotopic shift to 2174 cm-1 was observed when the reaction was performed under 15N2 and the band was not present when the experiment was undertaken under an atmosphere of argon, reinforcing this assignment. An intermediate solvent complex fac-[Mn(C^N)(CO)3(heptane)] was identified which is formed in less than 2 ps, indicating that CO-release occurs on an ultra-fast timescale. The heptane ligand is labile and is readily displaced by both N2 and water to give fac-[Mn(C^N)(CO)3(N2)] and fac-[Mn(C^N)(CO)3(OH2)] respectively. The fac-[Mn(C^N)(CO)3(heptane)] framework showed a significant affinity for N2, as performing the reaction under air produced significant amounts of fac-[Mn(C^N)(CO)3(N2)]. Kinetic analysis reveals that the substitution of heptane by N2 (k = (1.028 ± 0.004) × 109 mol-1 dm3 s-1), and H2O is competitive on fast (<1 μs) time scales. The binding of water is reversible and, under an atmosphere of N2, some fac-[Mn(C^N)(CO)3(OH2)] converts to fac-[Mn(C^N)(CO)3(N2)].

Physicochemical properties, molecular docking and global reactivity descriptors of manganese carbonyl complexes with imidazole ligands

Physicochemical properties, molecular docking and global reactivity descriptors of manganese carbonyl complexes with imidazole ligands

Dinuclear Manganese Carbonyl Complexes: Electrocatalytic Reduction of Protons to Dihydrogen

AbstractStudies on Mn complexes as electrocatalysts for proton reduction are limited. Mostly Mn complexes have been investigated for CO2 activation. Hence, hydrogen production by three Mn complexes [(Mn(CO)3(μ‐SN2C7H5))2] 1, [(Mn(CO)3(μ‐S2NC7H4))2] 3 and [Mn2(CO)7(μ‐S2NC7H4)2] 4 is reported in the paper. The complexes 1, 3 and 4 effectively catalyzed electrochemical proton reduction in CH3CN with trifluoroacetic acid (TFA) as the proton source. Complexes 1, 3 and 4 displayed turnover frequency (TOF / s−1) (overpotential, η / V) of 358 (0.83), 111 (0.79) and 102 (0.77), respectively for the catalytic process.

In situ study of the low overpotential "dimer pathway" for electrocatalytic carbon dioxide reduction by manganese carbonyl complexes.

The electrocatalytic reduction of CO2 using [fac-Mn(bpy)(CO)3Br] (bpy = 2,2'-bipyridine) and its derivatives has been the subject of numerous recent studies. However the mechanisms of catalysis are still debated. Here we carry out in situ vibrational sum-frequency generation (VSFG) spectroelectrochemistry to examine how this catalyst behaves at an electrode surface. In particular, a low overpotential pathway involving a dimeric manganese has been reported in several studies using substituted bipyridine ligands. Here, we find that the "dimer pathway" can also occur with the unsubstuituted bipyridine complexes. Specifically we can observe spectroscopic evidence of the interaction between [Mn2(bpy)2(CO)6] with CO2 in the presence of a suitable acid. Detailed VSFG studies of [Mn2(bpy)2(CO)6], including of the potential dependence of the surface ν(CO) mode, allow us to construct a model of how it accumulates and behaves at the electrode surface under potentiostatic control.

Correction to Dinuclear PhotoCORMs: Dioxygen-Assisted Carbon Monoxide Uncaging from Long-Wavelength-Absorbing Metal-Metal-Bonded Carbonyl Complexes.

We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium–manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal–metal-bond-to-ligand (σMM → πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re–Mn bonds to give mononuclear metal radicals. In the absence of trapping agents, these radicals primarily recombine to reform dinuclear complexes. In oxygenated media, however, the radicals react with dioxygen to form species much more labile toward CO release via secondary thermal and/or photochemical reactions. Conjugation of 4, with an amine-terminated poly(ethylene glycol) oligomer, gives a water-soluble derivative with similar photochemistry. In this contex...

Manganese N‐Heterocyclic Carbene Complexes for Catalytic Reduction of Ketones with Silanes

AbstractWell‐defined manganese(I) carbonyl complexes bearing bis‐N‐heterocyclic carbene (NHC) ligands are shown to be effective catalysts for the reduction of carbonyl groups through hydrosilylation reactions. A wide variety of ketones are selectively reduced to the corresponding alcohols by using phenylsilane, and the cheap and readily abundant polymethylhydrosiloxane (PMHS) in the presence of catalytic amounts of MnI organometallic complexes. Interestingly, α,β‐unsaturated ketones and dialkyl ketones are selectively reduced. Mechanistic studies based on radical scavengers suggest the involvement of radical species in the catalytic reaction.

Vesicles Functionalized with a CO-Releasing Molecule for Light-Induced CO Delivery.

In this paper, a new type of methodology to deliver carbon monoxide (CO) for biological applications has been introduced. An amphiphilic manganese carbonyl complex (1.Mn) incorporated into the 1,2-distearoyl-sn-glycero-3-phosphocholine lipid vesicles has been reported first time for the photoinduced release of CO. The liposomes (Ves-1.Mn) gradually released CO under light at 365 nm over a period of 50 min with a half-time of 26.5 min. The CO-releasing ability of vesicles appended with 1.Mn complexes has been confirmed by myoglobin assay and infrared study. The vesicles appended with 1.Mn have the advantages of biocompatibility, water solubility, and steady and slow CO release. This approach could be a rational approach for applying various water-insoluble photoinduced CO donors in aqueous media by using vesicles as a nanocarrier for CO release.

Acetoxymethyl Concept for Intracellular Administration of Carbon Monoxide with Mn(CO)3 -Based PhotoCORMs.

Targeted administration of carbon monoxide with CO releasing molecules (CORMs) inside of cells proved to be very challenging. Consequently, there are only very few reports on intracellular uptake of CORMs requiring high extracellular CORM loading because an equilibrium between extra- and intracellular concentrations can be assumed. Here we present a strategy for a targeted intracellular administration of manganese(I)-based CORMs that are altered inside of cells to trap these complexes. Thereafter, carbon monoxide can be liberated by irradiation (photoCORMs). To achieve this innovative task, acetoxymethyl (AM) groups are attached at the periphery of the hydrophobic manganese(I) carbonyl complexes to not influence the CO release behavior. Inside of cells these AM substituents are cleaved by esterases yielding hydrophilic manganese(I) carbonyl compounds which are captured inside of cells. This objective is realized by using the bidentate bases 4-(acetoxymethoxycarbonyl)phenyl-bis(3,5-dimethylpyrazolyl)methane (1) and 4-(acetoxymethoxy)phenyl-bis(3,5-dimethylpyrazolyl)methane (4) at facial (OC)3 MnBr fragments yielding CORM-AM1 (2) and CORM-AM2 (5), respectively. Besides synthesis, crystal structures and spectroscopic properties we present targeted administration and intracellular accumulation of these AM-containing CORMs.

A Luminescent Manganese PhotoCORM for CO Delivery to Cellular Targets under the Control of Visible Light.

A photoactive manganese carbonyl complex derived from dansylimidazole (Imdansyl), namely, [Mn(Imdansyl)(CO)3(phen)](CF3SO3) (1), has been synthesized and structurally characterized. This is the first luminescent manganese carbonyl-based photoCORM reported in the literature. This complex exhibits CO release under the exclusive control of low-power broadband visible light. The corresponding rhenium carbonyl complex, namely, [Re(Imdansyl)(CO)3(phen)](CF3SO3) (2), has also been reported, which is luminescent but sensitive only to UV-B (λ<315 nm) light. The entry of the manganese photoCORM into the human colorectal adenocarcinoma cells (HT-29) has been demonstrated with the aid of fluorescence microscopy. Irradiation of the photoCORM-loaded cancer cells to visible light leads to a dose-dependent apoptotic cell death.

IClick cycloaddition reaction of light-triggered manganese(i) carbonyl complexes

For a binuclear blue-light-induced CO-releasing manganese(i) tricarbonyl complex bearing bidentate ligand, the effect of the ancillary ligand on the dark stability and photolysis process was studied.

Spin-Forbidden Excitation: A New Approach for Triggering Photopharmacological Processes with Low-Intensity NIR Light.

Exposure to low‐intensity radiation in the near‐infrared (NIR) spectral region matching the optically transparent “phototherapeutic window” of biological tissues can be applied to directly populate spin‐restricted excited states of light‐responsive compounds. This unconventional and unprecedented approach is introduced herein as a new strategy to overcome some of the major unresolved problems observed in the rapidly emerging fields of photopharmacology and molecular photomedicine, where practical applications in living cells and organisms are still limited by undesired side reactions and insufficient light penetration. Water‐soluble and biocompatible metal complexes with a significant degree of spin–orbit coupling were identified as target candidates for testing our new hypothesis. As a first example, a dark‐stable manganese carbonyl complex acting as a visible‐light‐triggered CO‐releasing molecule (Photo‐CORM) is shown to be photoactivated by NIR radiation, although apparently no spectroscopically evident absorption bands are detectable in this low‐energy region. This quite remarkable effect is ascribed to a strongly restricted, but obviously not completely forbidden optical population of the lowest triplet excited state manifold of the diamagnetic complex from the singlet ground state.

Blue-light induced CO releasing properties of thiourea based manganese(I) carbonyl complexes

A new class of blue-light triggered carbon monoxide releasing molecules based on Mn(CO)3Br(N,S) ((N,S)=N,S-bidentate thiourea ligands) has been reported in this work. The 1H and 13C NMR analysis indicated that the thioureas coordinate to Mn(I) in the thione form. The stability test and the ability to derive CO to DMSO and myoglobin solution upon the exposure to 468nm light source have been investigated. The benzothiazole-thiourea-CORM released only one CO equivalent, while the pyridine-analogs offered two molecules at the same experimental conditions. Natural bond orbital analysis has been carried out to give details about the hybridization of MnC and CO bonds, natural charge, electronic arrangement of metal ion and strength of interaction between Mn(I) and the coordination sites. Both functional, B3LYP and CAM-B3LYP compare well with the experimental findings, where the longest wavelength band is assigned to MLCT.

Boosting the Catalytic Performance of Iron Phosphide Nanorods for the Oxygen Evolution Reaction by Incorporation of Manganese

The lack of efficient and stable oxygen evolution reaction (OER) catalysts comprising inexpensive Earth-abundant materials limits the viability of water splitting as a clean and renewable source of energy. In this work, we report the synthesis of homogeneous ternary Fe2–xMnxP nanorods with control of Mn incorporation (0 ≤ x ≤ 0.9) from the solution-phase reaction of manganese and iron carbonyl complexes with trioctylphosphine. The OER activity of Fe2–xMnxP nanorods dramatically increases with the incorporation of Mn (overpotential as low as 0.44 V at 10 mA/cm2 for x = 0.9), and the overpotential can be further decreased (by nearly 0.1 V) by postdeposition annealing. The enhanced OER activity and stability, along with the abundance and availability of Fe and Mn, make bimetallic manganese–iron phosphides a promising class of materials for more cost-effective and efficient water oxidation catalysis.

Synthesis, Structures, and CO Release Capacity of a Family of Water-Soluble PhotoCORMs: Assessment of the Biocompatibility and Their Phototoxicity toward Human Breast Cancer Cells.

Two manganese(I) carbonyl complexes derived from 2-(pyridyl)benzothiazole (pbt) and 1,10-phenanthroline (phen) release carbon monoxide (CO) under low-power broad-band visible-light illumination. CO photorelease from [Mn(CO)3(pbt)(PTA)]CF3SO3 (1, where PTA = 1,3,5-triaza-7-phosphaadamantane) is accompanied by an emergence of a strong fluorescence around 400 nm from almost nonfluorescent preirradiated 1. However, [Mn(CO)3(phen)(PTA)]CF3SO3 (2) showed no such phenomenon upon prolonged illumination under similar experimental conditions. The two analogous rhenium(I) complexes, namely, [Re(CO)3(pbt)(PTA)]CF3SO3 (3) and [Re(CO)3(phen)(PTA)]CF3SO3 (4), have also been synthesized and characterized to compare their photo properties with the manganese congeners. Complexes 3 and 4 exhibit moderate CO release upon irradiation with low-power UV light. All four complexes are highly soluble in anaerobic/aerobic aqueous media and are also considerably more stable when kept under dark conditions. The inherently luminescent rhenium complex 3 was utilized to demonstrate cellular internalization of these types of compounds by MDA-MB-231 (human breast cancer) cells, while the two biocompatible manganese(I) complexes (1 and 2) have been applied to assess the cell viability of these malignant cells upon CO delivery.

Mono- and bimetallic manganese-carbonyl complexes and clusters bearing imidazol(in)ium-2-dithiocarboxylate ligands.

Five complexes with the generic formula fac-[MnBr(CO)3(S2C·NHC)] were obtained by reacting [MnBr(CO)5] with a set of representative imidazol(in)ium-2-dithiocarboxylate zwitterions. These ligands are the adducts of N-heterocyclic carbenes (NHCs) and carbon disulfide. The mononuclear Mn(i) derivatives were coupled with Na[Mn(CO)5] to afford bimetallic [Mn2(CO)6(S2C·NHC)] clusters. Yet, the most convenient strategy to access these dinuclear Mn(0) products implied a direct carbonyl substitution from the [Mn2(CO)10] dimer. The molecular structures of three monometallic and four bimetallic compounds were elucidated by single crystal X-ray diffraction analysis. In the monometallic complexes, the NHC·CS2 ligands exhibited a bidentate κ2-S,S' coordination mode with an S-C-S bite angle of about 116°. In the dinuclear clusters, the CS2- unit acted as a chelate toward one manganese center and as a pseudoallylic ligand toward the other one. The S-C-S bite angle was reduced to ca. 104°. Thus, the zwitterions displayed a remarkable flexibility, which also permitted a staggered arrangement of the carbonyl groups in the bimetallic systems. Examination of the [small nu, Greek, macron]CO absorption bands on IR spectroscopy helped identify the presence of fac-Mn(CO)3 or Mn2(CO)6 motifs, while the 13C NMR chemical shift of the CS2- moiety was a reliable indicator for monitoring its hapticity. Whereas the dinuclear clusters were air- and moisture-stable crystalline solids, mononuclear halido derivatives displayed only a limited stability under aerobic conditions. Both types of compounds underwent rather unselective, extensive fragmentations in the gas phase, in sharp contrast with the analogous rhenium derivatives that led to clean sequential decarbonylation processes upon collision-induced dissociation.

Structure, CO-releasing property, electrochemistry, DFT calculation, and antioxidant activity of benzimidazole derivative substituted [Mn(CO)3(bpy)L]PF6 type novel manganese complexes

Metal carbonyl complexes are prominent group organometallic compounds because of their applications in industrial and pharmaceutical chemistry. In recent years, metal carbonyl complexes have been accepted major for storage and transportation of carbon monoxide which is an important signaling molecule significantly in pathogenesis of some diseases. Thus, we designed and synthesized novel manganese(I)carbonyl complexes with general formula [Mn(CO)3(bpy)L]PF6 (bpy=2,2-bipyridyl, L=N-(2-chlorobenzyl)benzimidazole, N-(2-methoxybenzyl)benzimidazole, N-(2-methylbenzyl)benzimidazole). The complex molecules were characterized by LC-MS, 1H-NMR, 13C-NMR, IR spectroscopy methods and elemental analysis. The CO-releasing properties, antioxidant activities and redox properties of these complexes were investigated. The DFT/TDDFT analyses were made by ORCA package program.

Carbon monoxide-releasing properties and DFT/TDDFT analysis of [Mn(CO)3(bpy)L]PF6 type novel manganese complexes

Novel manganese(I)carbonyl complexes of the general formula [Mn(CO)3(bpy)L]PF6 (bpy = 2,2-bipyridyl, L = N-(2-methylbenzyl)imidazoline, N-(3-methylbenzyl)imidazoline, N-(4-methylbenzyl)imidazoline, N-(2,4,6-trimethylbenzyl)imidazoline) were synthesized and characterized by analytical (LC-MS spectrometry and elemental analysis) and spectroscopic (1H NMR, 13C NMR, cosy2D-NMR, infrared) methods. The CO-releasing properties of these complexes were investigated with myoglobin assay. The DFT/TDDFT calculations were made by ORCA package program with both BP86 and B3LYP functionals.

MnBrL(CO)4] (L = Amidinatogermylene): Reductive Dimerization, Carbonyl Substitution, and Hydrolysis Reactions

The manganese(I) carbonyl complex [MnBr{Ge(iPr2bzam)tBu}(CO)4] (1; iPr2bzam = 1,3-di(isopropyl)benzamidinate), which contains an amidinatogermylene ligand, reacts with LiPh or LitBu at room temperature undergoing a reductive dimerization process that leads to the manganese(0) dimer [Mn2{Ge(iPr2bzam)tBu}2(CO)8]. This complex and the monosubstituted derivative [Mn2{Ge(iPr2bzam)tBu}(CO)9] have also been prepared by reacting [Mn2(CO)10] with Ge(iPr2bzam)tBu at high temperature (110 °C). These binuclear complexes contain their germylene ligands in axial positions (trans to the Mn–Mn bond). The large volume of the germylene ligand clearly affects the reactivity of complex 1 with neutral two-electron donor reagents, since for bulky reagents, the CO substitution occurs trans to the germylene ligand, as in trans-mer-[MnBrL{Ge(iPr2bzam)tBu}(CO)3] (L = Ge(iPr2bzam)tBu, PMe3), whereas for small reagents, the CO substitution occurs cis to the germylene ligand, as in fac-[MnBr(CNtBu){Ge(iPr2bzam)tBu}(CO)3]. The IR spectra (νCO) of these complexes have confirmed that the germylene Ge(iPr2bzam)tBu is a very strong electron-donating ligand, even stronger than the most basic trialkylphosphanes and N-heterocyclic carbenes. The hydrolysis of complex 1 leads to the salt [iPr2bzamH2][MnBr{Ge(OH)2tBu}(CO)4], the anion of which contains an unprecedented germanato(II) ligand, [Ge(OH)2tBu]−, in cis to the Br atom. This hydrolysis product and its precursor 1 have been tested as catalyst precursors for the electrolytic reduction of CO2, showing no significant activity.

The synthesis of PNP-supported low-spin nitro manganese(I) carbonyl complexes

The coordination chemistry of Mn(CO)5Br was investigated with a series of PNP-pincer ligands. The ligands iPrPONOP (iPrPONOP=2,6-bis(diisopropylphosphinito)pyridine) and iPrPNHP (iPrPNHP=HN{CH2CH2(PiPr2)}2) gave the desired organometallic manganese complexes (iPrPONOP)Mn(CO)2Br and (iPrPNHP)Mn(CO)2Br, respectively, upon chelation to Mn(CO)5Br. The reactivity of iPrPNNNP (iPrPNNNP=N,N′-bis(diisopropylphosphino)-2,6-diaminopyridine) with Mn(CO)5Br yielded a pair of products, [(iPrPNNNP)Mn(CO)3][Br] and (iPrPNNNCO)Mn(CO)3. The formation of the asymmetric chelate arises from a formal loss of iPr2PBr and C–N bond formation from a carbonyl ligand and NH, yielding a Mn(I) amide core. The nitration reactions of (iPrPONOP)Mn(CO)2Br and (iPrPNHP)Mn(CO)2Br were carried out using silver nitrite, yielding the nitro compounds (iPrPONOP)Mn(CO)2(NO2) and (iPrPNHP)Mn(CO)2(NO2), respectively. The analogous iron complex (iPrPONOP)Fe(CO)Cl2 was nitrated under the same conditions to yield the salt pair [(iPrPONOP)Fe(CO)2][FeCl3NO]. This reactivity underlines the difference between iso-valent iron and manganese centers. The manganese complexes (iPrPONOP)Mn(CO)2(NO2) and (iPrPNHP)Mn(CO)2(NO2) were ineffective as oxygen atom transfer reagents for a variety of substrates.