Carbonyl Ligands Research Articles

Pyrrolylmethylene Appended Corrorin: Peripheral Coordination and Transformation to Pyridyl Incorporated Hemiporphycene Analogue.

A pyrrolylmethylene appended corrorin 1 was synthesized and coordinated with [Rh(CO)2Cl]2 to afford 1-Rh with unique RhI-η2-CC bonding in addition to the coordination of the dipyrrin-like unit and a carbonyl ligand. Further oxidation of 1 afforded 2, exhibiting a hydrocorrorinone core, and it can be further transformed into pyrrolo[3,2-c]pyridine incorporated hemiporphycene analogue 3 upon treatment with HOAc. The side chain modifies the reactivity of corrorin and effectively tunes the NIR absorption of the resulting porphyrinoids.

Tetrazole-based inhibitors of the bacterial enzyme N-succinyl-l,l-2,6-diaminopimelic acid desuccinylase as potential antibiotics

Based on a hit from a high-throughput screen, a series of phenyltetrazole amides was synthesized and assayed for inhibitory potency against DapE from Haemophilus influenzae (HiDapE). The inhibitory potency was modest but confirmed, with the most potent analog containing an aminothiazole moiety displaying an IC50 = 50.2 ± 5.0 μM. Docking reveals a potential binding mode wherein the amide carbonyl bridges both zinc atoms in the active site, and the tetrazole forms key hydrogen bonds with Arg330.

XPu(CO)n (X = B, Al, Ga; n = 2 to 4): π Back-Bonding in Heterodinuclear Plutonium Boron Group Compounds with an End-On Carbonyl Ligand.

The bonding situation and the oxidation state of plutonium in heterodinuclear plutonium boron group carbonyl compounds XPu(CO)n (X = B, Al, Ga; n = 2 to 4) were investigated by systematically searching their ground-state geometrical structures and by analyzing their electronic structures. We found that the series of XPu(CO)n compounds show various interesting structures with an increment in n as well as a changeover from X = B to Ga. The first ethylene dione (OCCO) compounds of plutonium are found in AlPu(CO)n (n = 2, 3). A direct Ga-Pu single bond is first predicted in the series of GaPu(CO)n, where the bonding pattern represents a class of the Pu → CO π back-bonding system. There is a trend where the Pu-Ga bonding decreases and the Pu-C(O) covalency increases as the Ga oxidation state increases from Ga(0) to Ga(I). Our finding extends the metal → CO covalence back-bonding concept to plutonium systems and also enriches plutonium-containing bonding chemistry.

The reaction of Cp3U=CHPMenPh3-n, n = 1, 2, or 3, with [CpM(CO)2]2, M = Fe or Ru

The reactions of Cp3U=CHPMenPPh3-n (n = 1, 2, or 3) with [M(CO)2]2 (M = Fe or Ru) produce Cp3UOC(=CHPMenPh3-n)M2Cp2(CO)3, in which a terminal carbonyl in [M(CO)2]2 has inserted into the uranium carbon multiple bond of Cp3U=CHPMenPh3-n. The x-ray structure of Cp3UOC(=CHPMe3)Ru2Cp2(CO)3 has been determined and other analogous products have been characterized chemically and spectroscopically for both Ru and Fe species when n = 2 or 3. The products with n = 1 are less stable. The iron complexes, Cp3UOC(=CHPMenPh3-n)Fe2Cp2(CO)3, undergo a further coupling of the original terminal carbonyl with a bridging carbonyl to form an unusual allyl that is σ-coordinated to one Fe and π-coordinated to the other.

Production and characterization of chitosan of crustacean shells

After cellulose, chitin is the most prevalent biopolymer. The purpose of this work was to produce and characterize chitosan from expended crustacean shells (crab, prawn, and shrimp), primarily from Lagos State in Nigeria. Three main processes—deproteination, demineralization, and deacetylation—were used to manufacture their chitosan. The produced chitosan samples were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and X-ray Fluorescence (XRF) analyses, respectively, for functional components (ligands), surface shape, mineral constituent, and chemical constituent. The crab, shrimp, and prawn shell chitosan absorption altitudes ranged from 3360 to 893, 3775 to 570, and 3761 to 707 cm−1, respectively, in FTIR wavelengths; while both shrimp and prawn shell chitosan showed a clear and small filament lucent shape, the SEM pictures of crab shell chitosan showed a non-permeable, loosen skin semblance made up of protruding openings, tiny threadlike, and mineral form. Additionally, the chitosan found in shrimp shells is permeable and comprises granular layers. The crustaceans' related XRD results showed two tiny altitudes at 20°, 35°, 19.50° and 29.52°, 25.79° and 32.02°. Shrimp and prawn chitosan were both found to contain CaO, with larger proportions of 81.60 and 84.02%, respectively, according to XRF analysis. In general, all of the chitosan samples had amine, amide, carbonyl, carboxylic acid, hydrogen, and hydroxyl ligands (among others), which gave them better metal comity and band capability. As a result, the prepared chitosan of crab, prawn, and shrimp portrayed appropriate attributes for the adsorption techniques.

NMP makes the difference - facilitated synthesis of [FeFe] hydrogenase mimics.

To overcome the limitations of high reaction temperatures and long reaction times of conventional synthesis routes towards [FeFe] hydrogenase (H2ase) mimicking complexes, we introduced a more efficient synthesis route in the presence of aprotic polar co-solvents such as N-methyl-2-pyrrolidone (NMP). Versatile (di)thiol or disulfide ligands as well as selenium and tellurium analogues were converted to their corresponding complexes. While both reaction times and temperatures were reduced significantly, yields could be increased. Intensive kinetic monitoring of the formation of two [FeFe] H2ase mimics via UV-vis spectroscopy was performed, revealing an increase of the rate constant by one order of magnitude compared to that obtained in the same reaction without NMP. IR spectroscopic examination of the formation of the 1,3-propandithiole analogue (2a) revealed the appearance of a side product, analyzed by IR and UV-vis spectroscopy and mass spectrometry, which was proposed to be a NMP monosubstituted triirondodecacarbonyl (Fe3(CO)11NMP) cluster. Reacting triirondodecacarbonyl (Fe3(CO)12) with NMP in the absence of any additional ligand yielded this species as well. Quantum chemical simulations of Fe3(CO)11NMP indicated structural rearrangements including the omission of bridging carbonyls (μ-CO). Similar observations were made on utilizing other aprotic polar co-solvents.

Optimized Coordination of Uranyl in Engineered Calmodulin Site 1 Provides a Subnanomolar Affinity for Uranyl and a Strong Uranyl versus Calcium Selectivity.

As an alpha emitter and chemical toxicant, uranium toxicity in living organisms is driven by its molecular interactions. It is therefore essential to identify main determinants of uranium affinity for proteins. Others and we showed that introducing a phosphoryl group in the coordination sphere of uranyl confers a strong affinity of proteins for uranyl. In this work, using calmodulin site 1 as a template, we modulate the structural organization of a metal-binding loop comprising carboxylate and/or carbonyl ligands and reach affinities for uranyl comparable to that provided by introducing a strong phosphoryl ligand. Shortening the metal binding loop of calmodulin site 1 from 12 to 10 amino acids in CaMΔ increases the uranyl-binding affinity by about 2 orders of magnitude to log KpH7 = 9.55 ± 0.11 (KdpH7 = 280 ± 60 pM). Structural analysis by FTIR, XAS, and molecular dynamics simulations suggests an optimized coordination of the CaMΔ-uranyl complex involving bidentate and monodentate carboxylate groups in the uranyl equatorial plane. The main role of this coordination sphere in reaching subnanomolar dissociation constants for uranyl is supported by similar uranyl affinities obtained in a cyclic peptide reproducing CaMΔ binding loop. In addition, CaMΔ presents a uranyl/calcium selectivity of 107 that is even higher in the cyclic peptide.

Group 6 germylidyne complexes in the gas phase by LIFDI and APCI mass spectrometry.

Although showing fascinating chemical properties and reactivity in solution, heavier tetrelylidyne complexes with M≡E triple bonds have not been studied in the gas phase before due to their high sensitivity towards air and moisture. We selected four group 6 germylidyne complexes, [Cp(PMe3)2M≡GeArMes] (M = Mo (1-Mo), W (1-W), ArMes = 2,6-dimesitylphenyl) and [Tp'(CO)2M≡GeArMes] (M = Mo (2-Mo), W (2-W), Tp' = κ3-N,N',N''-hydridotris(3,5-dimethylpyrazolyl) borate), for a mass-spectrometric study. Liquid Injection Field Desorption Ionization (LIFDI) proved to be a well-suited technique to ionize these sensitive compounds as the spectra show the molecular ions as radical cations and only minor traces of fragmentation or degradation products. In addition, Atmospheric Pressure Chemical Ionization (APCI) connected to a high-resolving tandem mass spectrometer allowed us to study the gas-phase fragmentation behaviour of these compounds. The fragmentation patterns not only comprise the expected losses of phosphane or carbonyl ligands, respectively, but also indicate C-H bond activation by the electron-deficient metal centre. An enhanced reactivity of the tungsten species is visible in a preferred methyl abstraction in the phosphane complex 1-W compared to 1-Mo. Although degradation in solution before ionization obviously can destroy the M≡Ge triple bond, the cleavage of the M≡Ge bond upon gas-phase activation is not observed for the Mo species and only as a minor pathway for the W compounds, highlighting the high bonding energy between metal and tetrel.

Molecular docking, synthesis and antimicrobial evaluation of metal complexes with Schiff base

The appearance of resistant bacteria was found to reduce the efficiency of antimicrobial therapies with the current antibiotics, thereby increasing the need for more efficient drugs for the treatment of infections. A microbial infection affects tremendously to the human health and antimicrobials are one of the mainly successful forms of chemotherapy which saves the human population from the risk of infectious diseases. In this regard, the present study involves synthesis of transition metal complexes have often shown the immense antimicrobial activity. In this article, metal complexes were synthesized using different metals such as of Zn(II), Hg(II), Pt(II) and Pd(II), using Schiff’s base derived from amino and carbonyl ligand. All the synthesized compounds were characterized using IR, NMR, and mass spectral data and also by UV–visible spectra, molar electric conductance, magnetic susceptibility and thermal studies. Moreover, the antimicrobial activities of metal complexes were demonstrated using both gram negative and gram positive bacteria. The synthetic series of title compounds 6a-d, the compounds 6c and 6d with platinum and palladium metal were found to be active. The complex 6c has shown excellent antimicrobial activity and the result was also confirmed by molecular docking.

Diosmium carbonyl sawhorse complexes containing a ferrocenedicarboxylato ligand

In an attempt to prepare a supramolecular assembly consisting of two, three, or four diosmium carbonyl sawhorse units linked together by dicarboxylato ligands, the reaction of [Os3(CO)12] with ferrocene-1,1′-dicarboxylic acid, Fe(C5H4COOH)2, was carried out with microwave heating. Instead of an assembly, the lone diosmium product was the single sawhorse complex [Os2(μ-ferrocene-1,1′-dicarboxylato)(CO)6] (1) with a tetradentate doubly bridging Fe(C5H4CO2 –)2 ligand, a metal–metal single bond, four equatorial carbonyl ligands, and two axial carbonyl ligands. Two additional sawhorse complexes, [Os2(μ-ferrocene-1,1′-dicarboxylato)(CO)4(tri-p-tolylphosphine)2] (2) and [Os2(μ-ferrocene-1,1′-dicarboxylato)(CO)4(N,N-dimethylaminomethylferrocene)2] (3), were prepared by substituting the axial CO ligands in 1 with P- or N-donor ligands, respectively. Clusters 1, 2, and 3 represent the first examples of carbonyl sawhorse complexes with ferrocenedicarboxylato ligands, and all three were characterized with single-crystal X-ray diffraction studies.

Hybridization of amantadine with gardenamide A enhances NMDA antagonism and in vivo anti-PD effects

Eight hybrids of amantadine (ATD) with a natural modulator gardenamide A (GA) via an alkylene carbonyl bridge or alkylene bridge have been designed and synthesized. Evaluated by electrophysiological assay, compound 5b was confirmed an enhanced NMDAR antagonist compared to ATD with IC50 value of 10.2 ± 1.2 μM. 5b has been demonstrated to reverse the damages of behavioral performance, the loss of dopaminergic neurons, the reduction of TH positive, and the increase of α-synuclein in both MPTP-treated mice and zebrafish models. In both ethological and ecological experiments, the activity of 5b was confirmed better than ATD or ATD/GA combination, and was almost equal to the positive selegiline. In vivo and in vitro, 5b is shown to reverse the ascend of NR1 and i-NOS levels. This candidate was also demonstrated the activity to down-regulated MPTP-increased Ca2+ influx in SH-SY5Y cells in a steep and sharp mode. It is displayed that 5b exerts neuroprotective effect partly by activating the PI3K/Akt signaling pathway. Taken all together, our data support that 5b is a more promising agent against PD than ATD.

Rhenium Complexes with p‐Fluorophenylisocyanide

Abstractp‐Fluorophenylisocyanide (CNPhpF) reacts with [Re(CO)5Br] under stepwise exchange of the carbonyl ligands depending on the conditions applied. The reaction stops with the formation of fac‐[Re(CO)3Br(CNPhpF)2] in boiling THF. An ongoing carbonyl exchange is observed at higher temperatures, e. g. in refluxing toluene, with the final formation of the [Re(CNPhpF)6]+ cation. The progress of the reactions has been studied by 19F NMR spectroscopy and the structures of [Re(CO)Br(CNPhpF)4] and [Re(CNPhpF)6](BPh4) have been elucidated by X‐ray diffraction.

Mixed-Isocyanide Complexes of Technetium under Steric and Electronic Control.

Reactions of the alkyl isocyanide fac-[Tc(CO)3(CNR)2Cl] complexes (2) (CNR = CNnBu or CNtBu) with the sterically encumbered isocyanide CNp-FArDarF2 [DArF = 3,5-(CF3)2C6H3] allow a selective exchange of the carbonyl ligands of 2 and the isolation of the mixed-isocyanide complexes mer,trans-[Tc(CNp-FArDarF2)3(CNR)2Cl] (3). Depending on the steric requirements of the residues R, the remaining chlorido ligand can be replaced by another isocyanide ligand. Cationic complexes such as mer-[Tc(CNp-FArDarF2)3(CNnBu)3]+ (4a) or mer,trans-[Tc(CNp-FArDarF2)3(CNnBu)2(CNtBu)]+ (6) have been prepared in this way and isolated as their PF6- salts. mer,trans-[Tc(CNp-FArDarF2)3(CNnBu)2(CNtBu)](PF6) represents to the best of our knowledge the first transition-metal complex with three different isocyanides in its coordination sphere. Since the degree of the ligand exchange seems to be controlled both by the electronic and steric measures of the incoming isocyanides, we undertook similar reactions with the sterically less demanding p-fluorophenyl isocyanide, CNPhpF, which indeed readily led to the hexakis(isocyanide)technetium(I) cation through an exchange of all ligands in the staring materials [Tc2(CO)6(μ-Cl)3]- or fac-[Tc(CO)3(CNR)2Cl]. The influence of the substituents at the isocyanide ligands in such reactions has been reasoned with the density functional theory-derived electrostatic potential at the accessible surface of the corresponding isocyanide carbon atoms.

Basal Plane Functionalization of Niobium Disulfide Nanosheets with Cyclopentadienyl Manganese(I) Dicarbonyl.

Basal plane-functionalized NbS2 nanosheets were obtained using in situ photolysis to generate the coordinatively unsaturated organometallic fragment cyclopentadienyl manganese(I) dicarbonyl (CpMn(CO)2). Under UV irradiation, a labile carbonyl ligand dissociates from the tricarbonyl complex, creating an open coordination site for bonding between the Mn atom and the electron-rich sulfur atoms on the surface of the NbS2 nanosheets. In contrast, no reaction is observed with 2H-MoS2 nanosheets under the same reaction conditions. This difference in reactivity is consistent with the electronic structure calculations, which indicate stronger bonding of the organometallic fragment to electron-poor, metallic NbS2 than to semiconducting, electron-rich MoS2. X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) spectroscopy, and powder X-ray diffraction (PXRD) were used to characterize the bonding between Mn and S atoms on the surface-functionalized nanosheets.

N,N′-Di-tert-butyl-P,P-diphenylphosphinimidic Amidato-κN,κN′]chlorosilicon-κSi-tetracarbonyliron

The title complex {[Ph2P(tBuN)2](Cl)Si:->Fe(CO)4} (2) was synthesized via the reaction of chlorosilylene [Ph2P(tBuN)2]SiCl (1), supported by an iminophosphonamide ligand with Fe(CO)5 in THF. The molecular structure of 2 was fully characterized by NMR (1H, 13C, 29Si, and 31P) and IR spectroscopies, as well as single-crystal X-ray diffraction (SCXRD) analysis. In the SCXRD analysis of 2, the silylene ligand was located in the axial positions of the coordination sphere of the central iron atom and other sites were occupied by carbonyl ligands.

Biomimics of [FeFe]-hydrogenases incorporating redox-active ligands: Ferrocene-bridged dithiolate complexes [Fe2(CO)6(μ-EC5H4FeC5H4E)] (E = S, Se)

Ferrocene-bridged dithiolate complexes [Fe2(CO)6(μ-EC5H4FeC5H4E)] (E = S, Se) (1-2) have been studied as biomimics of [FeFe]-hydrogenases, ferrocene taking the role of an Fe4S4 surrogate. Both show a quasi-reversible electron reduction at E1/2 = -1.81 V and -1.56 V respectively with IR SEC showing that it is Fe2-based (ca. 50 cm−1 hypsochromic shift) and leads to a significant structural rearrangement with formation of a bridging carbonyl being at ca. 1715 cm−1. They also show reversible one-electron oxidation with a small (ca. 15 cm−1) hypsochromic ν(CO) shift, showing it is ferrocene-based, while oxidation of the Fe2 centre occurs outside of the potential window. DFT calculations on 1 show that the HOMO is ferrocene-based, and the LUMO Fe2-based, both in accord with the IR SEC results. However, the radical anion [1]− is calculated to have an elongated metal-metal vector rather than a bridging carbonyl, although a complex with an open structure [1(μ-CO)]− in which one thiolate group moves from a bridging to a terminal position is energetically similar. For 2, DFT shows the HOMO is Fe2-based, which is not supported experimentally. Complexes 1-2 are proton-reduction catalysts at their first reduction potential in the presence of trifluoroacetic acid. DFT suggests two competing pathways for H2 generation catalysed by 1, occurring upon protonation of either [1]− or [1(μ-CO)]− to give bridging and terminal hydride complexes respectively. For 2, DFT suggests that [2(μ-CO)]− is only slightly higher in energy than [2]−, probably a result of the weaker Fe-Se vs Fe-S bond, and thus proton-reduction likely proceeds (primarily) through the open-structure isomer.

In Situ Time-of-Flight Mass Spectrometry of Ionic Fragments Induced by Focused Electron Beam Irradiation: Investigation of Electron Driven Surface Chemistry inside an SEM under High Vacuum.

Recent developments in nanoprinting using focused electron beams have created a need to develop analysis methods for the products of electron-induced fragmentation of different metalorganic compounds. The original approach used here is termed focused-electron-beam-induced mass spectrometry (FEBiMS). FEBiMS enables the investigation of the fragmentation of electron-sensitive materials during irradiation within the typical primary electron beam energy range of a scanning electron microscope (0.5 to 30 keV) and high vacuum range. The method combines a typical scanning electron microscope with an ion-extractor-coupled mass spectrometer setup collecting the charged fragments generated by the focused electron beam when impinging on the substrate material. The FEBiMS of fragments obtained during 10 keV electron irradiation of grains of silver and copper carboxylates and shows that the carboxylate ligand dissociates into many smaller volatile fragments. Furthermore, in situ FEBiMS was performed on carbonyls of ruthenium (solid) and during electron-beam-induced deposition, using tungsten carbonyl (inserted via a gas injection system). Loss of carbonyl ligands was identified as the main channel of dissociation for electron irradiation of these carbonyl compounds. The presented results clearly indicate that FEBiMS analysis can be expanded to organic, inorganic, and metal organic materials used in resist lithography, ice (cryo-)lithography, and focused-electron-beam-induced deposition and becomes, thus, a valuable versatile analysis tool to study both fundamental and process parameters in these nanotechnology fields.

Mechanistic and Kinetic Investigations of ON/OFF (Photo)Switchable Binding of Carbon Monoxide by Chromium(0), Molybdenum(0) and Tungsten(0) Carbonyl Complexes with a Pyridyl‐Mesoionic Carbene Ligand

This work tackles the photochemistry of a series of mononuclear Cr0, Mo0 and W0 carbonyl complexes containing a bidentate mesoionic carbene ligand of the 1,2,3‐triazol‐5‐ylidene type. FTIR spectroscopy, combined with density functional theory calculations, revealed a clean photo‐induced reaction in organic solvents (acetonitrile, pyridine, valeronitrile) to give mainly one photoproduct with monosubstitution of a carbonyl ligand for a solvent molecule. The highest photodissociation quantum yields were reached for the Cr0 complex under UV irradiation (266 nm). Based on previous investigations, the kinetics of the dark reverse reactions have now been determined, with reaction times of up to several hours in pyridine. Photochemical studies in the solid state (KBr matrix, frozen solution) also showed light‐induced reactivity with stabilization of the metastable intermediate with a free coordination site at very low temperature. The identified reactive species emphasizes a mechanism without ligand–sphere reorganization.

Excited‐State Dynamics of Phosphorescent Trinuclear Re(I) Complexes

AbstractThe excited‐state dynamics of cyanide‐bridged trinuclear carbonyl rhenium(I) complexes with general formula of [Re]p[Re]c[Re]p {[Re]c=[(−NC)ReI(CO)2(phen)(CN−)]; [Re]p=[−ReI(CO)2(L L)(La)], L L= diimine or diphosphine, La=triphenylphosphine or carbonyl ligand} and the monomeric peripheral control complexes have been elucidated through a study with ultrafast transient absorption spectroscopy. The time constants for the energy transfer between the MLCT excited states of the peripheral and central Re(I) chromophores (ca. 0.56–0.78 ps) are typical for other cyanide‐bridged polynuclear transition metal complexes. The emissive excited states and the absorption transient have been characterized by nanosecond transient Raman spectroscopy.

SYNTHESIS AND PROPERTIES OF RUTHENIUM CLUSTER COMPLEXES

Methods for the synthesis of ruthenium cluster complexes based on carbonyl and amine-containing organic bifunctional ligands have been developed. The structure of the obtained combinations of clusters were determined on the basis of IR spectroscopy data, thermogravimetry, and elemental analysis. Samples of ligands I and II were obtained by condensation of carboxylic acid chlorides of cyclopentane and cyclohexane with ethylene followed by replacement of the chlorine atom by amine groups. To obtain cluster complexes of ruthenium with the synthesized ligands the ruthenium trichloride salt (RuCl3) was dissolved in water, and the calculated amount of sodium borohydride was added in portions to the resulting solution under vigorous stirring in nitrogen atmosphere. Rapidly emerging black-dispersed nanoparticles of metallic ruthenium did not precipitate. When organic ligands I and II are added, the corresponding cluster compounds III and IV are formed, which gradually over 45 min. precipitated from an aqueous solution. The resulting dark-brown precipitates were washed with distilled water and dried in a nitrogen atmosphere at a temperature of 35-400C. The melting temperatures of the synthesized compounds were determined, the components for cluster III - 2060С and cluster IV - 2220С (with decomposition). The IR spectra of cluster compounds show intense absorption bands characterizing the presence of both the ketone carbonyl group and the amine fragment. The absorption bands of ketone groups in cluster compounds are shifted towards higher frequencies compared to the initial ligands. A similar picture is also observed when comparing the IR vibrations of CN bonds in the initial ligands and the corresponding cluster compounds. The results of elemental analysis confirm the structures of cluster compounds and are in complete agreement with the concept that cluster compounds are formed upon the reduction of ruthenium salts with metal hydrides in an aqueous solution. Apparently, in this case, the most stable ruthenium clusters with tetrahedral structure are formed.. Thermogravimetric analysis made it possible to establish the presence of a peak at a temperature of 3180C with a mass number of 744.8 , corresponding to a cluster combination of four ruthenium atoms. At each stage of decomposition, the experimental mass losses are in good agreement with the calculated values. Keywords: synthesis, ruthenium, cluster complexes, amine and caryonyl containing ligands, bifunctional ligands, cyclopentyl amino ketone, cyclohexyl amino ketone.