Important Transition Metal Research Articles

Two-Dimensional Semiconductors Thin Films of MoS2 and MoSe2 on Ag(111)

In the recent years, technological development in the fields spanning from nanoelectronics to new solar energy materials, requires highly controlled nanostructured surfaces, ultra-thin films and 2D structured materials. The Electrochemical Atomic Layer Deposition (E-ALD) is one of these techniques that allows us to produce thin films of semiconductor. Exploiting Surface Limited Reactions (SLR), it enables the deposition of highly ordered ultra-thin films from diluted aqueous solutions and at room temperature and pressure. Underpotential deposition (UPD) is a type of electrochemical SLR, where an atomic layer of a first element is deposited on a second, at a potential prior to (under) that needed to deposit the first element on itself, so that the resulting deposit is generally limited to an atomic layer. It occurs when the depositing element is able to somehow interact with the substrate, so that the deposition of the layer in direct contact with the substrate occurs at a potential preceding bulk deposition, that is, the deposition of the element on itself. MoS2 and MoSe2 are important transition metal dichalcogenides (TMDs). E-ALD method was used to obtain semiconductor compounds in the form of thin films. UPD anodic electrodeposition of Na2S and Na2SeO3 on crystalline Ag[111] electrode are well-known. The research move to discover the optimal conditions to deposit Mo on Ag/S and on Ag/Se from a solution of MoO4 2- in alkaline buffer. This study has been carried by means of voltammetric techniques, XPS and AFM characterizations of the deposit.

Elastic, thermodynamic, electronic, and optical properties of recently discovered superconducting transition metal boride NbRuB: An ab-initio investigation

The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation (GGA) and local density approximation (LDA) are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency (energy) dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.

Observing Imperfection in Atomic Interfaces for van der Waals Heterostructures

Vertically stacked van der Waals heterostructures are a lucrative platform for exploring the rich electronic and optoelectronic phenomena in two-dimensional materials. Their performance will be strongly affected by impurities and defects at the interfaces. Here we present the first systematic study of interfaces in van der Waals heterostructure using cross-sectional scanning transmission electron microscope (STEM) imaging. By measuring interlayer separations and comparing these to density functional theory (DFT) calculations we find that pristine interfaces exist between hBN and MoS2 or WS2 for stacks prepared by mechanical exfoliation in air. However, for two technologically important transition metal dichalcogenide (TMDC) systems, MoSe2 and WSe2, our measurement of interlayer separations provide the first evidence for impurity species being trapped at buried interfaces with hBN interfaces that are flat at the nanometer length scale. While decreasing the thickness of encapsulated WSe2 from bulk to monolayer we see a systematic increase in the interlayer separation. We attribute these differences to the thinnest TMDC flakes being flexible and hence able to deform mechanically around a sparse population of protruding interfacial impurities. We show that the air sensitive two-dimensional (2D) crystal NbSe2 can be fabricated into heterostructures with pristine interfaces by processing in an inert-gas environment. Finally we find that adopting glovebox transfer significantly improves the quality of interfaces for WSe2 compared to processing in air.

Direct Imaging of Kinetic Pathways of Atomic Diffusion in Monolayer Molybdenum Disulfide.

Direct observation of atomic migration both on and below surfaces is a long-standing but important challenge in materials science as diffusion is one of the most elementary processes essential to many vital material behaviors. Probing the kinetic pathways, including metastable or even transition states involved down to atomic scale, holds the key to the underlying physical mechanisms. Here, we applied aberration-corrected transmission electron microscopy (TEM) to demonstrate direct atomic-scale imaging and quasi-real-time tracking of diffusion of Mo adatoms and vacancies in monolayer MoS2, an important two-dimensional transition metal dichalcogenide (TMD) system. Preferred kinetic pathways and the migration potential-energy landscape are determined experimentally and confirmed theoretically. The resulting three-dimensional knowledge of the atomic configuration evolution reveals the different microscopic mechanisms responsible for the contrasting intrinsic diffusion rates for Mo adatoms and vacancies. The new insight will benefit our understanding of material processes such as phase transformation and heterogeneous catalysis.

Controllable fabrication of Cu<sub>2</sub>O porous nanostructured films by negative bias deposition method

As one of the most common two kinds of copper oxides, cuprous oxide (Cu2O) is an important p-type transition metal oxide semiconductor material. Due to the advantages of low-cost, non-toxicity and abundant copper sources and the potential applications in the fields of gas sensors, solar cells and photocatalysts, thin films of Cu2O have attracted great interest of researchers. To enhance the performances of the above Cu2O-based surface-sensitive devices and materials, the researchers tend to prepare Cu2O thin films of porous or even nanoporous structures. However, there is still no effective method available for the controllable fabrication of Cu2O porous nanostructured films (or porous nanostructure-films, short for PNFs), which owns not only the common features of porous thin films but also the unique properties of nanosize building units. By using a radio- frequency balanced magnetron sputtering (MS) deposition system, in this paper, Cu2O PNFs were prepared on clean glass slides by applying different negative bias voltage during film deposition. After the preparation, a field-emission scanning electron microscope (FESEM), a grazing-incidence X-ray diffractometer (GIXRD) and an ultraviolet-visible (UV-Vis) spectrophotometer were applied subsequently for the detailed characterizations of surface morphology, texture and optical property respectively. It was observed that the as-prepared Cu2O PNFs exhibited flexible porosities and nanosize building units, which were greatly dependent on the substrate negative bias voltage. In particular, when the substrate bias voltage was kept at −50 or −150 V, the as-prepared Cu2O PNFs both demonstrated intriguing triangular pyramid-like nanostructures with distinct edges and corners on the porous film surface. Further, the side view FESEM images and the out-of-plane GIXRD spectra demonstrated a columnar growth of the Cu2O PNFs with a notable preferential orientation of (111). The optical testing results showed that the band gap of the Cu2O PNFs obtained at different negative bias voltages was tunable between 2.0 and 2.35 eV, which demonstrated a little red or blue shift relative to that of bulk Cu2O (2.17 eV). It is expected that the traditional ion bombardment and re-sputtering theories are not suitable for the explanation of the above bias voltage effects. This is because the traditional ion bombardment and re-sputtering theories were proposed to account for the bias deposition in an unbalanced magnetron sputtering (MS) system rather than the present balanced MS system. Further, the experimentally observed non-linearly changed density or porosity of the Cu2O PNFs with the bias voltage at relatively low values and the common even surface at relatively high values confirmed this viewpoint. Based on the above findings and analysis, a selectively preferential deposition of material atoms or molecules on the film surface during the negative bias deposition was proposed. That is, when the substrate is negatively biased, the tip- charging effect of electrons would occur on the nanoscale rough surface of the substrate or the depositing film. The resulting electric field near the substrate or film surface is non-uniform and could be regarded as an assembly of many electric fields of particle or tip charges. As a consequence, the sputtered atoms or molecules would be acted by two kinds of Coulomb forces: one is the attractive force originating from the electric fields of the closest particles or tips when traveling near the substrate, and the other is the repulsive force coming from the surrounding particles or tips with the same kind of charges after depositing on one particle or tip. For the former force, it would lead to a preferential deposition of sputtered atoms or molecules on the particles or tips and meanwhile provide an additional kinetic energy for the deposited atoms or molecules to migrate or diffuse around; for the later force, the constraint effect of the surrounding electric fields of particle or tip charges would hinder the migration or diffusion of deposited atoms or molecules on the film surface. It is thus expected that the tip charging effect would lead to a columnar growth of films, and the contradictory of the above two forces would influence or even determine the final surface morphology of films which depends on the value of substrate bias voltage.

Colloidal synthesis of MoSe2 nanonetworks and nanoflowers with efficient electrocatalytic hydrogen-evolution activity

MoSe2 represents an important layered transition metal dichalcogenides (LTMDs) that have high electrocatalytic activity in hydrogen evolution reaction (HER). A key issue to achieve excellent electrochemical properties of MoSe2 is to synthesize nanostructures that are composed of few-layer MoSe2 with maximized exposure of active edge sites. In this study, we report the synthesis of MoSe2 nanostructures with network-like and flower-like morphologies via an organic solution approach that utilizes molybdenum hexacarbonyl as Mo precursor and Se powders as Se source. The prepared MoSe2 nanostructures consist of few-layer ultrathin nanosheets which can have different orientations. Depending on the volume ratio of oleylamine to oleic acid, the arrangement of ultrathin MoSe2 nanosheets is adjustable and can form porous network-like or discrete flower-like nanostructure which has large specific surface area and a wealth of exposed edge sites. Excellent HER activities with low overpotentials, small Tafel slopes and long-term durability are observed on the as-synthesized MoSe2 nanostructures. The acetic acid-washing step that may effectively remove the organic molecules capped on MoSe2 surfaces is also found to be efficient in improving the HER activity of the synthesized MoSe2 nanostructures.

Bromide ion mediated modification to digestive ripening process: Preparation of ultra-small Pd, Pt, Rh and Ru nanoparticles

Nanoparticles of catalytically important transition metals, such as Pd, Pt, Rh, and Ru have been prepared by the well-known “digestive ripening” (DR) and “modified digestive ripening” (mDR) methods. In the traditional DR process, a polydisperse colloidal dispersion is refluxed in the presence of a surface-active molecule, such as alkanethiol. The mDR method involved a small modification in the procedure, wherein refluxing was performed with an alkanethiol and a tetra-alkylammonium bromide surfactant. This minor modification led to a dramatic change in the final particle size distributions, giving access to nanoparticles in the <3 nm size regime; this was not possible with the traditional DR process. Bromide ions, which are present during refluxing, proved to be an important ingredient in the modification process. These bromide ions are revealed to act as etchants, resulting in ultra-small nanoparticles. All transition metal nanoparticles investigated displayed catalytic activity in the reduction reaction of p-nitro phenol. Pd nanoparticles, synthesized by a modified digestive ripening method, exhibited the best catalytic activity among the systems investigated.

Progress on Synthesis and Applications of Cr2O3 Nanoparticles.

As is known to us that nanosized chromic oxide (Cr2O3) is an important transition metal oxide. Because it has many excellent properties, it can be used in many fields such as pigment, catalyst, Lithium material etc. This article briefly reviewed the preparation and applications of Cr2O3 nanoparticles. In this paper, some specific applications will be listed according to different fields. Nanosized chromic oxide (Cr2O3) can be obtained via many methods. A summary of the methods have been made. The preparation methods are divided into three main types, including vapor phase method, solid phase method and liquid phase method. Simultaneously, different types of methods have been simply evaluated in this paper. And the advantage and disadvantage are simply noted.

Development of some important nitrogen donor ligands for transition metal homogeneous catalysis

This review provides a broad overview of the literature related to the importance of ligands in homogeneous catalysis. In particular, it describes the types of nitrogen donor ligands that have typically been used for homogeneous catalysis. We surveyed the important transition metal homogenous catalysts explicitly from 2011 up to early 2014 and summarize their comparative catalytic activities. Generally, the main factors observed are the ligand structure, electron donor property and steric bulk which can affect the catalytic activity. Electron count and inductive effect can also influence the efficiency of homogeneous catalyst.

Direct Mass Spectrometric Analysis of Zinc and Cadmium in Water by Microwave Plasma Torch Coupled with a Linear Ion Trap Mass Spectrometer

Microwave plasma torch (MPT) is a simple and low power-consumption ambient ion source. When MPT mass spectrometry is applied in the detection of some metal elements, the metallic ions exhibit some novel features which are different from traditional ICP mass spectrometry and may be helpful for the metal element analysis. Zinc and cadmium both are important transition metals with wide applications in modern industry. Here, we presented the research results of the MPT mass spectra of zinc and cadmium elements by a linear ion trap mass spectrometer (LTQ) both in positive and negative modes. Without any sample pretreatment, the aqueous samples were pneumatically nebulized and the aerosols were generated. The dried aerosols were introduced into the plasma through the central tube of the MPT to generate the complex metallic ions. For the positive composite ions of zinc and cadmium, the general forms are the hybrid of M(NO3)·nOH·mH2O, thus the MPT mass spectra are extremely complicated and unsuitable for the quantitative monitoring. However, the MPT negative ionic of zinc and cadmium is quite regular in the forms of M(NO3). We also showed that the limit of detection (LOD) for zinc and cadmium in negative mode can be achieved at the level of 10μg/L (ppb). Therefore, the negative mode MPT mass spectrometry can be used as one of the alternative supplements of ICP-MS applied in on-line monitoring of zinc and cadmium metal ions in water at trace levels, which will be promising in the field analysis of metal elements and the rapid water quality inspection.

Pyridine and related ligands in transition metal homogeneous catalysis

This review provides a broad overview of the literature related to the importance of pyridine and related ligands in homogeneous catalysis. In particular, it describes the various ways by which this ligand can stabilised the metal within a complex for homogeneous catalysis. We surveyed the important transition metal homogenous catalysts containing pyridine and related ligand acting as backbone for other ligands in homogeneous catalytic reactions explicitly from 2011 up to early 2014 and summarized their comparative catalytic activities.

The Study of Structural and Magnetic Properties of NiO Nanoparticles

Nickel Oxide (NiO) is an important transition metal oxide with cubic lattice structure. Among the magnetic nanoparticles, fabrication of nickel nanoparticles is often more difficult than that of the other particles. This is because they are easily oxidized. To achieve pure nickel nanocrystals, numerous methods have been conducted in organic environments in order to prevent formation of hydroxide or oxidation. In the present work, we report the synthesis of NiO nanoparticles. Magnetic properties of NiO nanoparticles with different sizes and at different temperatures are compared. The phase structures, particle sizes and magnetic properties of NiO nanoparticles have been characterized by X-ray diffraction, TEM images and Vibrating Sample Magnetometer (VSM). We collected the experimental data reported in the literature, for the same conditions, and after fitting, extrapolating and doing some calculations. The magnetization for smaller nanoparticles is bigger for the samples we consider here. This difference could be explained by the difference of surface volume ratio of nanoparticle which shows the contribution of the paramagnetic surface is more important with respect to the anti-ferromagnetism of the core for smaller particles. Also the nanoparticle at lower temperatures shows bigger magnetization.

Transcriptome analysis of Streptococcus pneumoniae D39 in the presence of cobalt.

Cobalt (Co2 +) is an important transition metal ion that plays a vital role in cellular physiology of bacteria. The role of Co2 + in the regulation of several genes/operons in Streptococcus pneumoniae has recently been reported [1]. The data described in this article relate to the genome-wide transcriptional profiling of Streptococcus pneumoniae D39, either in the presence or absence of 0.5 mM Co2 + in chemically defined medium (CDM) using DNA microarray analysis. Genes belonging to a broad range of cellular processes such as virulence, transport and efflux systems, stress response and surface attachment were differentially expressed in the presence of Co2 +. We used transcriptional lacZ assays and electrophoretic mobility shift assays (EMSAs) to confirm our results [1]. The dataset is publicly available at the Gene Expression Omnibus (GEO) repository (http://www.ncbi.nlm.nih.gov/geo/) with accession number GSE57696.

Copper oxide nanoparticles: an antidermatophytic agent for Trichophyton spp.

Abstract Copper oxide (CuO) is one of the most important transition metal oxides due to its unique properties. It is used in various technological applications such as high critical temperature, superconductors, gas sensors, in photoconductive applications and so on. Recently, it has been used as an antimicrobial agent against various pathogenic bacteria. In the present investigation, we studied the structural and antidermatophytic properties of CuO nanoparticles (NPs) synthesized by a precipitation technique. Copper sulfate was used as a precursor and sodium hydroxide as a reducing agent. Scanning electron microscopy (SEM) showed flower-shaped CuO NPs and X-ray diffraction (XRD) pattern showed the crystalline nature of CuO NPs. These NPs were evaluated against two prevalent species of dermatophytes, i.e. Trichophyton rubrum and T. mentagrophytes by using the broth microdilution technique. Further, the NPs activity was also compared with synthetic sertaconazole. Although better antidermatophytic activity was exhibited with sertaconazole as compared to NPs, being synthetic, sertaconazole may not be preferred, as it shows different adverse effects. Trichophyton mentagrophytes is more susceptible to NPs than T. rubrum. A phylogenetic approach was applied for predicting differences in susceptibility of pathogens.

Co(2+)-dependent gene expression in Streptococcus pneumoniae: opposite effect of Mn(2+) and Co(2+) on the expression of the virulence genes psaBCA, pcpA, and prtA.

Manganese (Mn2+)-, zinc (Zn2+)- and copper (Cu2+) play significant roles in transcriptional gene regulation, physiology, and virulence of Streptococcus pneumoniae. So far, the effect of the important transition metal ion cobalt (Co2+) on gene expression of S. pneumoniae has not yet been explored. Here, we study the impact of Co2+ stress on the transcriptome of S. pneumoniae strain D39. BLAST searches revealed that the genome of S. pneumoniae encodes a putative Co2+-transport operon (cbi operon), the expression of which we show here to be induced by a high Co2+ concentration. Furthermore, we found that Co2+, as has been shown previously for Zn2+, can cause derepression of the genes of the PsaR virulence regulon, encoding the Mn2+-uptake system PsaBCA, the choline binding protein PcpA and the cell-wall associated serine protease PrtA. Interestingly, although Mn2+ represses expression of the PsaR regulon and Co2+ leads to derepression, both metal ions stimulate interaction of PsaR with its target promoters. These data will be discussed in the light of previous studies on similar metal-responsive transcriptional regulators.

Rapid Preparation of WO3 Nanorods Via Microwave-Assisted Solvothermal Synthesis

A simple and efficient method enables to synthesize nanorods WO3 with high quantity by microwave-solvothermal. It has been found that ethanol involves the features of inexpensive and environmentally friendly, which is more suitable to be considered as a solvent. Tungsten oxide is an important transition metal oxide material, which possesses some unique properties such as electrochromic, opochromic, and gaschromic properties. The authors used the microwave assisted solvothermal method, which has the advantages of both microwave and solvothermal methods, to synthesize 1-D tungsten oxide such as nanorods. The synthesis of tungsten oxide nanorods has been investigated under microwave-solvothermal conditions at 240°C, and uses WCl6 and poly(ethylene glycol) (PEG) 20000 as a precursor and dispersant in 20% ethanol. The average diameter of WO3 nanorods were 80–100 nm and 3 μm long. The crystallized products were characterized by X-ray diffraction, thermogravimetric analysis, dynamic light scattering, X-ray fluorescence, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy.

High performance of Mn-Co-Ni-O spinel nanofilms sputtered from acetate precursors.

Mn-Co-Ni-O (MCN) spinel oxide material, a very important transition metal oxide (TMO) with the best application prospects in information and energy fields, was discovered over five decades ago, but its applications have been impeded by the quality of its films due to the magnitude of deposition challenge. Here we report that high quality of MCN nanofilms can be achieved by sputtering deposition via acetate precursors whose decomposition temperatures are matched to the initial synthesis temperature of the MCN thin films. Excellent performance of MCN nanofilms is demonstrated, combining for the first time preferred orientation, high temperature coefficient of resistance, and moderate resistivity. The film devices show an intrinsic recombination with a much faster rate of the order of a microsecond for the laser-pumped carriers, which is ~3 orders of magnitude larger compared with that of the ceramic material. The electronic structure of the thin films confirms that it is indeed of n-type nature, exhibiting appropriate electronic states consistent with the levels of metal electrodes and semiconductors. The results offer a vital avenue for depositing high performance TMO thin films for advanced oxide devices, and will have great significance for exploiting new applications in modern oxide electronics and optoelectronics.

High-pressure structure, decomposition, and superconductivity ofMoS2

The high pressure structural and electronic evolution of bulk MoS$_2$, an important transition metal layered dichalchogenide, is currently under active investigation. Recent theoretical and experimental work predicted and verified a 2H$_c \to$ 2H$_a$ layer sliding structural transition at 20 GPa and a band overlap semiconductor-semimetal transition in the same pressure range. The 2H$_a$ structure is known to persist up to pressure of 81 GPa but properties at higher pressures remain experimentally unknown. Here we predict, with a reliable first-principles evolutionary search, that major structural transformations should take place in equilibrium at higher pressures near 130-140 GPa. The main motif is a decomposition into MoS + S, also heralded in a small bimolecular cell by the appearance of a metastable non-layered metallic MoS$_2$ structure with space group \textit{P4/mmm}. Unlike semimetallic 2H$_a$-MoS$_2$, both this phase and sulphur in the fully phase separated system are fully metallic and superconducting with higher critical temperatures than alkali-intercalated MoS$_2$.

Genotoxic effects of bismuth (III) oxide nanoparticles by comet assay

Event Abstract Back to Event Genotoxic effects of bismuth (III) oxide nanoparticles by comet assay Reecep Liman1*, Muhsin Konuk2 and İbrahim H. Ciğerci3 1 Uşak University, Molecular Biology and Genetics, Turkey 2 Üsküdar University, Molecular Biology and Genetics, Turkey 3 Afyon Kocatepe University, Molecular Biology and Genetics, Turkey Bismuth oxide is one of the important transition metal oxides and it has been intensively studied due to their peculiar characteristics (semiconductor band gap, high refractive index, high dielectric permittivity, high oxygen conductivity, resistivity, photoconductivity and photoluminescence etc.). Therefore, it is used such as microelectronics, sensor technology, optical coatings, transparent ceramic glass manufacturing, nanoenergetic gas generator, biosensor for DNA hybridization, potential immobilizing platforms for glucose oxidase and polyphenol oxidase, fuel cells, a additive in paints, an astringent in a variety of medical creams and topical ointments, and for the determination of heavy metal ions in drinking water, mineral water and urine. In addition this, Bismuth (III) oxide nanoparticles (BONPs) are favorable for the biomolecules adsorption than regular sized particles because of their greater advantages and novel characteristics (much higher specific surface, greater surface free energy, and good electrochemical stability etc.). Genotoxic effects of BONPs were investigated on the root cells of Allium cepa by Comet assay. A. cepa roots were treated with the aqueous dispersions of BONPs at 5 different concentrations (12.5, 25, 50, 75, and 100 ppm) for 4 h. A significant increase in DNA damage was also observed at all concentrations of BONPs except 12.5 ppm by Comet assay. The results were also analyzed statistically by using SPSS for Windows; Duncan’s multiple range test was performed. These result indicate that BONPs exhibit genotoxic activity in A. cepa root meristematic cells. Keywords: Allium, Comet, DNA Damage, bismuth oxide, Nanoparticles Conference: ICAW 2015 - 11th International Comet Assay Workshop, Antwerpen, Belgium, 1 Sep - 4 Sep, 2015. Presentation Type: Poster Presentation Topic: Genotoxicity testing of chemicals and nanomaterials Citation: Liman R, Konuk M and Ciğerci İH (2015). Genotoxic effects of bismuth (III) oxide nanoparticles by comet assay. Front. Genet. Conference Abstract: ICAW 2015 - 11th International Comet Assay Workshop. doi: 10.3389/conf.fgene.2015.01.00010 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 13 May 2015; Published Online: 23 Jun 2015. * Correspondence: Dr. Reecep Liman, Uşak University, Molecular Biology and Genetics, Uşak, Turkey, recep.liman@usak.edu.tr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Reecep Liman Muhsin Konuk İbrahim H Ciğerci Google Reecep Liman Muhsin Konuk İbrahim H Ciğerci Google Scholar Reecep Liman Muhsin Konuk İbrahim H Ciğerci PubMed Reecep Liman Muhsin Konuk İbrahim H Ciğerci Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Transition metal complexes of phyllobilins - a new realm of bioinorganic chemistry.

Natural cyclic tetrapyrroles feature outstanding capacity for binding transition metal ions, furnishing Nature with the important metallo-porphyrinoid 'Pigments of Life', such as heme, chlorophyll (Chl) and vitamin B12. In contrast, linear tetrapyrroles are not generally ascribed a biologically relevant ability for metal-binding. Indeed, when heme or Chl are degraded to natural linear tetrapyrroles, their central Fe- or Mg-ions are set free. Some linear tetrapyrroles are, however, effective multi-dentate ligands and their transition metal complexes have remarkable chemical properties. The focus of this short review is centred on such complexes of the linear tetrapyrroles derived from natural Chl-breakdown, called phyllobilins. These natural bilin-type compounds are massively produced in Nature and in highly visible processes. Colourless non-fluorescing Chl-catabolites (NCCs) and the related dioxobilin-type NCCs, which typically accumulate in leaves as 'final' products of Chl-breakdown, show low affinity for transition metal-ions. However, NCCs are oxidized in leaves to give less saturated coloured phyllobilins, such as yellow or pink Chl-catabolites (YCCs or PiCCs). YCCs and PiCCs are ligands for various biologically relevant transition metal-ions, such as Zn(ii)-, Ni(ii)- and Cu(ii)-ions. Complexation of Zn(ii)- and Cd(ii)-ions by the effectively tridentate PiCC produces blue metal-complexes that exhibit an intense red fluorescence, thus providing a tool for the sensitive detection of these metal ions. Outlined here are fundamental aspects of structure and metal coordination of phyllobilins, including a comparison with the corresponding properties of bilins. This knowledge may be valuable in the quest of finding possible biological roles of the phyllobilins. Thanks to their capacity for metal-ion coordination, phyllobilins could, e.g., be involved in heavy-metal transport and detoxification, and some of their metal-complexes could act as sensitizers for singlet oxygen or as plant toxins against pathogens.