Class Of Organometallic Compounds Research Articles

Cationic Carbon Monoxide-Releasing Polymers as Antimicrobial and Antibiofilm Agents by the Synergetic Activity.

Recent studies indicate that carbon monoxide-releasing molecules (CORMs), a class of organometallic compounds, exert antibacterial activities through the delivery of carbon monoxide (CO) molecules. We developed a new-class CO-delivery system by conjugating classical low-molecular-weight CORMs (i.e., [Ru(CO)3Cl2]2 and Mn(CO)5Br) onto a positively charged carrier, polyimidazolium (PIM), giving cationic CO-releasing polymers Ru@PIM and Mn@PIM, respectively. Compared with low-molecular-weight CORMs, our polymeric CO vehicles showed improved water solubility, reduced cytotoxicity, significantly extended CO-releasing duration, and enhanced antimicrobial ability against both planktonic and biofilm microorganisms. Ru@PIM and Mn@PIM inhibited the growth of a broad spectrum of free Gram-positive and Gram-negative bacteria as well as fungus with the lowest minimum inhibitory concentration (MIC) at 8 μg/mL. They were effective in preventing pathogenic Pseudomonas aeruginosa biofilm formation with biofilm reduction by more than 92% at 16 μg/mL and 99% at 32 μg/mL. They also demonstrated potent dispersal efficacy on recalcitrant well-established biofilms through a synergetic activity with a biofilm log10 reduction of 2.5-3.2 ≥ 64 μg/mL and nearly 2.0 at the concentration of as low as 16 μg/mL. This CO-releasing system may retain long-time antimicrobial ability after the complete release of CO molecules owing to the cationic structure. The novel CO-releasing polymers have great potential as antimicrobial and antibiofilm agents in biomedical applications.

SYNTHESIS OF THIAZOLOQUINAZOLINARYLTELLURID

Symmetric and asymmetric chalcogenides of organic nature are a class of organometallic compounds that are widely used as intermediates in a number of organic reactions, as ligands in the chemistry of coordination compounds, they have a wide range of biological activity. Diaryl tellurides, which are important for the formation of new carbon-carbon bonds, have a special area in the chemistry of organotelluric compounds. The synthesis of new representatives of this class of tellurium-containing compounds is an urgent task.
 One of the main methods of obtaining of diaryl tellurides is the interaction of arylboronic acids with diarylditellurides in the presence of various metal-containing catalysts or microwave radiation. In this paper, we have considered the method of obtaining asymmetric tellurides by the reaction of reduction of sodium sulfite with salts of thiazoloquinazolinaryl dichlorotellurides without the usage of catalysts.
 It was found that the reaction of 2-((dichloro(4-methoxyphenyl)-4-tellanyl)methyl)-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one hydrochloride with triple excess of sodium sulfite leads to the formation of 2-((4-methoxyphenyl)tellanyl)methyl)-2,3-dihydro-5H-thiazolo [2,3-b]quinazolin-5-one. It should be noted that the recovery does not break the bond Te-C. In the analysis of spectral data, the signals of the protons of the thiazole cycle and the exocyclic aryltelluric fragment undergo a strong field shift.
 Thus, as a result of the reduction reaction of 2-((dichloro(4-methoxyphenyl)-4-tellanyl)methyl)-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one hydrochloride, a biologically promising and suitable for further functionalization telluride was received.

Carbynes reloaded: Isolation of singlet metallocarbenes

Metallocarbenes are the elusive electromers of the well-established carbyne complexes with subvalent carbon ligands. In this issue of <i>Chem</i>, Liu and co-workers report the isolation of the first bona fide metallocarbenes. Their work introduces a new class of organometallic compounds with unique bonding properties and paves the way toward new catalytic applications.

Novel meso‐substituted ferrocene‐appended porphyrins: Synthesis, characterization, and electrochemical evaluation

This paper focuses on the synthesis of the novel ferrocene‐appended porphyrin architectures and their zinc metal complexes. Tetraferrocenylporphyrins are a class of organometallic compounds where the porphyrin core is functionalized with a ferrocenyl unit at each of the four meso positions. Tetraferrocenylporphyrin derivatives were synthesized via a direct tetramerization reaction between some ferrocene carboxaldehyde derivatives and pyrrole in the presence of BF3·Et2O as an efficient catalyst. Moreover, a metalation reaction between tetraferrocenylporphyrin derivatives and zinc acetate was applied in the synthesis of related zinc complexes. The structures of the new organometallic compounds were confirmed by Fourier transform infrared spectroscopy (FT‐IR), 1H NMR, 13C NMR, UV–vis, and CHNS analyses. The redox‐active properties of the synthesized compounds were characterized by cyclic voltammetry (CV) analysis.

Boron Chemistry for Medical Applications.

Boron compounds now have many applications in a number of fields, including Medicinal Chemistry. Although the uses of boron compounds in pharmacological science have been recognized several decades ago, surprisingly few are found in pharmaceutical drugs. The boron-containing compounds epitomize a new class for medicinal chemists to use in their drug designs. Carboranes are a class of organometallic compounds containing carbon (C), boron (B), and hydrogen (H) and are the most widely studied boron compounds in medicinal chemistry. Additionally, other boron-based compounds are of great interest, such as dodecaborate anions, metallacarboranes and metallaboranes. The boron neutron capture therapy (BNCT) has been utilized for cancer treatment from last decade, where chemotherapy and radiation have their own shortcomings. However, the improvement in the already existing (BPA and/or BSH) localized delivery agents or new tumor-targeted compounds are required before realizing the full clinical potential of BNCT. The work outlined in this short review addresses the advancements in boron containing compounds. Here, we have focused on the possible clinical implications of the new and improved boron-based biologically active compounds for BNCT that are reported to have in vivo and/or in vitro efficacy.

Guanidine-modified cyclometalated iridium(III) complexes for mitochondria-targeted imaging and photodynamic therapy

PDT is a well-established therapeutic modality for many types of cancer. Photoluminescent cyclometalated iridium(III) complexes are one of the most commonly used classes of organometallic compounds with potential beneficial applications in bioimaging and as promising anticancer agents. In the present study, three new cyclometalated iridium(III) complexes (Ir1–Ir3) containing guanidinium ligands were found to exert excellent cytotoxic effects on different types of cancer cells upon light irradiation at 425 nm. Notably, Ir1 conferred almost no dark toxicity (IC50 > 100 μM) to HepG2 cells, but the value decreased by 387-fold to 0.36 μM following 10 min of light irradiation (425 nm). Further mechanistic investigation revealed that complex Ir1 could induce apoptosis via the activation of reactive oxygen species (ROS)-mediated mitochondrial signaling pathways in the presence or absence of light irradiation. In vivo studies demonstrated that Ir1 significantly inhibited tumor growth in HepG2 xenograft-bearing mice under light irradiation at 425 nm. Taken together, these findings indicate that designing PDT-based Ir(III) complexes may hold a great deal of promise for anticancer drug development.

Position of Methyl and Nitrogen on Axial Aryloxy Substituents Determines the Crystal Structure of Silicon Phthalocyanines

Phthalocyanines are a class of organometallic compounds that have been investigated extensively for emerging applications such as organic photovoltaics, organic light-emitting diodes, and thin-film transistors. For these applications, the understanding of molecular structures and intermolecular interactions is extremely crucial and is one of the most promising pathways for designing a new generation of functional materials. Here, the crystal structures of six axially substituted silicon phthalocyanines (SiPcs) with aryloxy groups are reported. Three bis(methylphenoxy) SiPcs with varying methyl positions and two bis(pyridoxy) derivatives with varying nitrogen positions are compared to the bare bis(phenoxy) SiPc. Quantitative analysis is conducted to describe the impact of the position and nature of the functional group/atom on the orientation of the axial aryloxy subtituents as well as on the aromaticity and planarity of the SiPc macrocycle. Quantitative analysis of changes in intermolecular interactions, ...

Relation between topology and stability of bent titanocenes

Bent metallocenes are a class of organometallic compounds that are widely used as catalysts in olefin polymerization procedures. We found a linear relation between the relative stability of bent titanocenes and the average delocalization index (DI) for Ti-C (from the cyclopentadienyl ring) atomic pairs within the evaluated compounds. As a consequence, the stability of the bent titanocenes can be estimated from their topologies. However, secondary interactions between the ligands of some of the bent titanocenes reduce the coefficient of determination for the average DI-stability relation.

ChemInform Abstract: Tantallaaziridines: From Synthesis to Catalytic Applications

AbstractReview: 76 refs.

Tantallaaziridines: from synthesis to catalytic applications

Tantallaaziridines are a class of organometallic compounds containing three-membered rings that include a tantalum, carbon and nitrogen atom. Closely related complexes containing the related iminoacyl ligand can be used as starting materials for tantallaaziridine synthesis. Tantallaaziridines can also be synthesized by reduction of imines or β-hydrogen abstraction of amides to give stable, isolable complexes. Tantallaaziridines possess a reactive Ta-C bond that can undergo stoichiometric transformations with unsaturated organic molecules to give new organometallic products. Upon quenching of such reactions with aqueous workup, selectively substituted small molecule amines can be prepared. Tantallaaziridines have also been proposed as catalytic intermediates in the direct α-alkylation of amines, hydroaminoalkylation, by exploiting the β-hydrogen abstraction route to regenerate the catalytically active species. Recent progress and remaining challenges in the field will be discussed.

Structural analysis of organometallic compounds with soft ionization mass spectrometry

The analysis of organometallic compounds with mass spectrometry has some special features in comparison with organic and bioorganic compounds. The first step is the choice of a suitable ionization technique, where the electrospray ionization is certainly the best possibility for most classes of organometallic compounds and metal complexes. Some ionization mechanisms of organometallic compounds are comparable to organic molecules, such as protonation/deprotonation, and adduct formation with sodium or potassium ions; however, in many cases, different mechanisms and their combinations complicate the spectra interpretation. Organometallics frequently undergo various types of adduct and polymerization reactions that result in significantly higher masses observed in the spectra in comparison to molecular weights of studied compounds. Metal elements typically have more natural isotopes than common organic elements, which cause characteristic wide distributions of isotopic peaks; for example, tin has ten natural isotopes. The isotopic pattern can be used for the identification of the type and number of metal elements in particular ions. The ionization and fragmentation behavior also depend on the type of metal atom; therefore, our discussion of mass spectra interpretation is divided according to the different type of organometallic compounds. Among various types of mass spectrometers available on the market, trap-based analyzers (linear or spherical ion-traps, Orbitrap) are suitable to study complex fragmentation pathways of organometallic ions and their adducts, whereas high-resolution and high-mass accuracy analyzers (time-of-flight-based analyzers, or Fourier transform-based analyzers-Orbitrap or ion cyclotron resonance mass spectrometers) provide accurate masses applicable for the determination of the elemental composition of individual ions.

The Shortened Transition Metal–Tellurium Bonds in Organometallic Clusters

The shortening of partly multiple M-Te (M = Mn, Fe, Co, Cr or W) bonds is observed for two classes of organometallic compounds: (1) formally electron-deficient species with additional donor-acceptor interaction between Te lone pairs and half-occupied d-orbitals of M; (2) formally electron-saturated species having additional dative interaction between M lone pairs and LUMO of Te. These compounds could be prepared by two main methods: (a) interaction of [CpMn(CO) 2 PhC(O) − ]Li + with Te proceeds via formation of intermediate {[CpMn(CO) 2 ] 2 Te} 2− which is further transformed into binuclear complex [CpMn(CO) 2 ] 2 Te(CH 2 Ph) 2 or into trinuclear ditelluride cluster [CpMn(CO) 2 ] 3 Te 2 on one hand or to mixed-metal monotelluride clusters [CpMn(CO) 2 ] 2 TeM(CO) 5 on another hand. (b) treatment of Fe(CO) 5 , CpMn(CO) 2 (THF) or Me 4 C 4 Co(CO) 2 I with [PhTeI] 4 , PhTeI 3 or PhTeI 2 HC = CPhI results in different PhTeI-containing complexes of Fe, Mn or Co. The molecular structures of all new compounds were studied by means of X-ray diffraction analyses and the mechanism of M-Te bond shortening is discussed.

Ruthenium (II)-Derived Organometallic Compounds Induce Cytostatic and Cytotoxic Effects on Mammalian Cancer Cell Lines through p53-Dependent and p53-Independent Mechanisms

The metallic compound cisplatin has been used for many years to treat various human cancers. Here, we describe the cytostatic and cytotoxic properties of a new class of organometallic compounds that contain a ruthenium (II) atom covalently linked to carbon and nitrogen atoms. We found that several ruthenium-derived compounds (RDCs) led to G1 arrest and induced apoptosis in tumor cell lines derived from glioblastomas, neuroblastomas, and lymphoid tumors at least as efficiently as cisplatin. We further analyzed the signaling pathways underlying these effects, and we showed that both RDCs and cisplatin induced p53 and p73 protein levels but with different intensities and kinetics. This accumulation of p53 and p73 proteins correlated with an increase in p21 and Bax expression, two p53 target genes linked to cell growth arrest and apoptosis. However, in contrast to cisplatin-induced apoptosis, overexpression of DeltaNp73, a p53 and p73 dominant-negative isoform, only partly reduced RDC-induced apoptosis, suggesting p53-dependent and p53-independent modes of action. This observation was further confirmed by the ability of RDC to induce apoptosis in p53-/- cells. Altogether, this study highlights key cellular and molecular features of RDCs and suggests that further development of this new class of compounds may contribute to improve future chemotherapeutic protocols.

Cyclopentadienyl—Carboranyl Hybrid Compounds: A New Class of Versatile Ligands for Organometallic Chemistry

AbstractFor Abstract see ChemInform Abstract in Full Text.

Cyclopentadienyl-carboranyl hybrid compounds: a new class of versatile ligands for organometallic chemistry.

A new class of organic-inorganic hybrid compounds bearing a cyclic pi-ligand, an icosahedral carborane moiety, and a bridging group has been developed. These are very versatile ligands, featuring both an organic and an inorganic moiety as well as a bridging ligand. They can be readily converted into mono-, di-, tri- and pentaanionic species under suitable reaction conditions, leading to the generation of a new class of organometallic compounds in which the carboranyl unit can be cast in the role of a bulky substituent, a sigma-, eta(5), eta(6), or eta(7) pi-ligand. This Account provides an overview of our recent work in this area.

Organometallic Homogeneous Catalysis—Quo vadis?

AbstractHomogeneous catalysis is the success story of organometallic chemistry. Otto Roelen's initial discovery of hydroformylation in 1938 not only entailed large‐capacity production plants but was later followed by systematic research into the catalytic chemistry of the ever‐growing class of organometallic compounds. Further developments in industrial chemistry towards clean, low‐temperature, low‐pressure, and economic processes—in feedstock or in the fine chemicals and polymer area—clearly depend on improved catalysts. Molecularly defined, tailor‐made structures are the safest prerequisites for chemical selectivity; hence, organometallic compounds with their overwhelming variety of compositions and structures offer the most promising approach. Wilkinson's catalysts [HRh(CO){P(C6H5)3] and [ClRh{P(C6H5)}3}3] are outstanding examples. On the other hand, process technology has to be considered also (for example catalyst‐product separation and hear‐exchange problems). The following review attempts to critically assess the future trends and present demands in the applied area of orgnometallic catalysis–a “gentle art” that is far from being a mature field.

Synthesis and optical properties of a new class of organometallic compounds: Organometallic merocyanines

Abstract A new class of organometallic compounds, organometallic merocyanines based upon the [( η -(C 5 H 5 ) 2 Fe 2 (CO) 2 ( μ -CO)] fragment acting as a donor, have been synthesized and characterized. The non-linear optical properties of these organometallic merocyanines have been determined by electric field induced second harmonic generation and indicate that these compounds have large second-order optical non-linearities.

Computer processing and interpretation of mass spectral information. Part IX—generalized characteristics of mass spectra

AbstractThe formation of numerical generalized characteristics (indices) of mass spectra by using one or two experimental parameters (mass numbers and/or ion peak amplitudes) is suggested. The influence of the measuring error of peak amplitudes on the statistical characteristics of indices was studied. It was ascertained by four classes of organometallic compounds that within an isolated class the value of each index is distributed by a normal law. The possibility of using mass spectral indices for the identification of unknown compounds is demonstrated.

Relationship between structure and stereoselectivity in ring-opening metathesis polymerization catalytic systems

Polypentenylenes of varying cis and trans steric configurations have been synthesized from cyclopentene using binary and ternary catalytic systems based on WCl 6 and three classes of organometallic compounds: organoaluminium, organotin and organosilicon. In several cases the distribution of the double-bond pair sequences has been determined from the fine structure of the 13C NMR spectra. Analysis of the polymer microstructure indicated that the catalytic systems derived from WCl 6 and organoaluminium compounds (Bu i 3Al, Et 3Al, ET 2AlCl and EtAlCl 2) gave mainly trans configuration of the carbon-carbon double bond and a random or slightly blocky distribution of the double-bond dyads. By contrast, catalysts derived from WCl 6 and organotin (Et 4Sn, Bu 4Sn and Ph 4Sn) and organosilicon (Me 2(allyl) 2Si) compounds led primarily to cis configuration of the carbon-carbon double bond and a blocky or slightly blocky distribution of the double-bond dyads. In addition, the catalysts based on WCl 6 and aluminoxane (diisobutylaluminoxane) exhibited a rather high cis stereospecificity in cyclopentene polymerization. ESR and UV-Vis investigations as well as ceriometric determinations performed on WCl 6/Bu i 3Al, WCl 6/Bu i 2AlOAlBu i 2, WCl 6/Me 2(allyl) 2Si and WCl 6/Ph 4Sn afforded new structural data concerning the oxidation states of the W atom and the interaction between the catalytic components. These results indicated that (if other parameters, e.g., temperature, time, activators, solvent, are not considered) there exists a direct correlation between the oxidation state of the W species generated in these systems and the polymer microstructure. These data allowed proposals to be advanced concerning the structure of the active species, the mechanism and the stereochemistry of the ring-opening polymerization induced by the above catalysts.

Action Mechanism of Load-Carrying Performance of a New Lubricant Additive

A new load-carrying additive belonging to the class of organo-metallic compounds having ligands of 8-hydroxyquinoline has recently been developed. The additive provides excellent lubrication for motor oils under very high load and speed conditions; it also acts as friction modifier. A study has been made to elucidate the action mechanism of this additive. An approach based on the negative ion concept has been applied. To determine the formation of negative ions of this additive and its ligand, electron attachment mass spectrography was used. On the basis of the results of mass spectrographic and tribological investigation, a lubrication mechanism of this additive has been proposed. The mechanism provides one explanation of all the friction and wear reduction effects of the additive experienced in practical applications.