Row Transition Metal Ions Research Articles

Some nontoxic metal-based drugs for selected prevalent tropical pathogenic diseases.

Metal coordination of bioorganic compounds from both natural and synthetic products is not only gaining recognition in drug design and medicinal inorganic chemistry research, also they are being considered in the improvement of the bioactivity of drugs. What is done in this paper is a review of recent advances in the study of coordination-driven drug delivery, i.e., metal-based drugs (MBDs). The role of some late first row transition metal ions namely Fe, Cu and Zn in the biological activities of metallodrugs such as antimalarials and antimicrobials are highlighted. It was revealed that the interaction between these bio-essential transition metal ions and the organic drugs could enhance the diagnostic and therapeutic potentials of such formed drugs. This is because such interactions were proved to have improved the stability, bioavailability and cell delivery functions of the metallodrugs. Emphasizing on the challenge of metal ions toxicity, the researchers concluded on the need for the development of MBDs to combat drug resistant parasites without causing injury to normal cells. This would be of significance in addressing the concern World Health Organisation of ameliorating the increasing mortality rate in developing countries.

Kinetic Studies of the Coordination of Mono- and Ditopic Ligands with First Row Transition Metal Ions.

The reactions of the ditopic ligand 1,4-bis(2,2':6',2″-terpyridin-4'-yl)benzene (1) as well as the monotopic ligands 4'-phenyl-2,2':6',2″-terpyridine (2) and 2,2':6',2″-terpyridine (3) with Fe(2+), Co(2+), and Ni(2+) in solution are studied. While the reaction of 1 with Fe(2+), Co(2+), and Ni(2+) results in metallo-supramolecular coordination polyelectrolytes (MEPEs), ligands 2 and 3 give mononuclear complexes. All compounds are analyzed by UV/vis and fluorescence spectroscopy. Fluorescence spectroscopy indicates that protonation as well as coordination to Zn(2+) leads to an enhanced fluorescence of the terpyridine ligands. In contrast, Fe(2+), Co(2+), or Ni(2+) quench the fluorescence of the ligands. The kinetics of the reactions are studied by stopped-flow fluorescence spectroscopy. Analysis of the measured data is presented and the full kinetic rate laws for the coordination of the terpyridine ligands 1, 2, and 3 to Fe(2+), Co(2+), and Ni(2+) are presented. The coordination occurs within a few seconds, and the rate constant increases in the order Ni(2+) < Co(2+) < Fe(2+). With the rate constants at hand, the polymer growth of Ni-MEPE is computed.

Synthesis, characterization and biological approach of metal chelates of some first row transition metal ions with halogenated bidentate coumarin Schiff bases containing N and O donor atoms

The impregnation of halogen atoms in a molecule is an emerging trend in pharmaceutical chemistry. The presence of halogens (Cl, Br, I and F) increases the lipophilic nature of molecule and improves the penetration of lipid membrane. The presence of electronegative halogen atoms increases the bio- activity of core moiety. In the present study, Co(II), Ni(II) and Cu(II) complexes are synthesised using Schiff bases (HLI and HLII), derived from 8-formyl-7-hydroxy-4-methylcoumarin/3-chloro-8-formyl-7-hydroxy-4-methylcoumarin with 2,4-difluoroaniline/o-toluidine respectively. The synthesized compounds were characterized by spectral (IR, NMR, UV–visible, Mass, ESI-MS, ESR), thermal, fluorescence and molar conductivity studies. All the synthesized metal complexes are completely soluble in DMF and DMSO. The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. Elemental analysis study suggest [ML2(H2O)2] stoichiometry, here M=Co(II), Ni(II) and Cu(II), L=deprotonated ligand. The obtained IR data supports the binding of metal ion to Schiff base. Thermal study suggests the presence of coordinated water molecules. Electronic spectral results reveal six coordinated geometry for the synthesized metal complexes. The Schiff bases and their metal complexes were evaluated for antibacterial (Pseudomonas aureginosa and Proteus mirabilis), antifungal (Aspergillus niger and Rhizopus oryzae), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activities.

The First Histidine Triad Motif of PhtD Is Critical for Zinc Homeostasis in Streptococcus pneumoniae.

Streptococcus pneumoniae is the world's foremost human pathogen. Acquisition of the first row transition metal ion zinc is essential for pneumococcal colonization and disease. Zinc is acquired via the ATP-binding cassette transporter AdcCB and two zinc-binding proteins, AdcA and AdcAII. We have previously shown that AdcAII is reliant upon the polyhistidine triad (Pht) proteins to aid in zinc recruitment. Pht proteins generally contain five histidine (His) triad motifs that are believed to facilitate zinc binding and therefore play a significant role in pneumococcal metal ion homeostasis. However, the importance and potential redundancy of these motifs have not been addressed. We examined the effects of mutating each of the five His triad motifs of PhtD. The combination of in vitro growth assays, active zinc uptake, and PhtD expression studies show that the His triad closest to the protein's amino terminus is the most important for zinc acquisition. Intriguingly, in vivo competitive infection studies investigating the amino- and carboxyl-terminal His triad mutants indicate that the motifs have similar importance in colonization. Collectively, our new insights into the contributions of the individual His triad motifs of PhtD, and by extension the other Pht proteins, highlight the crucial role of the first His triad site in zinc acquisition. This study also suggests that the Pht proteins likely play a role beyond zinc acquisition in pneumococcal virulence.

ChemInform Abstract: 3d Single‐Ion Magnets

AbstractReview: single‐molecule magnets consisting of one first row transition metal ion in a suitable ligand field; 52 refs.

Host-imposed manganese starvation of invading pathogens: two routes to the same destination.

During infection invading pathogens must acquire all essential nutrients, including first row transition metals, from the host. To combat invaders, the host exploits this fact and restricts the availability of these nutrients using a defense mechanism known as nutritional immunity. While iron sequestration is the most well-known aspect of this defense, recent work has revealed that the host restricts the availability of other essential elements, notably manganese (Mn), during infection. Furthermore, these studies have revealed that the host utilizes multiple strategies that extend beyond metal sequestration to prevent bacteria from obtaining these metals. This review will discuss the mechanisms by which bacteria attempt to obtain the essential first row transition metal ion Mn during infection, and the approaches utilized by the host to prevent this occurrence. In addition, this review will discuss the impact of host-imposed Mn starvation on invading bacteria.

Dysregulation of transition metal ion homeostasis is the molecular basis for cadmium toxicity in Streptococcus pneumoniae.

Cadmium is a transition metal ion that is highly toxic in biological systems. Although relatively rare in the Earth’s crust, anthropogenic release of cadmium since industrialization has increased biogeochemical cycling and the abundance of the ion in the biosphere. Despite this, the molecular basis of its toxicity remains unclear. Here we combine metal-accumulation assays, high-resolution structural data and biochemical analyses to show that cadmium toxicity, in Streptococcus pneumoniae, occurs via perturbation of first row transition metal ion homeostasis. We show that cadmium uptake reduces the millimolar cellular accumulation of manganese and zinc, and thereby increases sensitivity to oxidative stress. Despite this, high cellular concentrations of cadmium (~17 mM) are tolerated, with negligible impact on growth or sensitivity to oxidative stress, when manganese and glutathione are abundant. Collectively, this work provides insight into the molecular basis of cadmium toxicity in prokaryotes, and the connection between cadmium accumulation and oxidative stress.

A polyamide receptor based benzothiazole derivative: highly selective and sensitive fluorescent sensor for Hg2+ ion in aqueous medium

A water soluble benzothiazole derivative having polyamide arms has been designed and synthesized. The sensor selectively detects Hg2+ ion in aqueous medium in presence of alkali, alkaline earth, first row transition metal and heavy metal ions. The reversible behaviour of the sensor can be achieved in presence of iodide ion.

3d single-ion magnets.

One of the determining factors in whether single-molecule magnets (SMMs) may be used as the smallest component of data storage, is the size of the barrier to reversal of the magnetisation, Ueff. This physical quantity depends on the magnitude of the magnetic anisotropy of a complex and the size of its spin ground state. In recent years, there has been a growing focus on maximising the anisotropy generated for a single 3d transition metal (TM) ion, by an appropriate ligand field, as a means of achieving higher barriers. Because the magnetic properties of these compounds arise from a single ion in a ligand field, they are often referred to as single-ion magnets (SIMs). Here, the synthetic chemist has a significant role to play, both in the design of ligands to enforce propitious splitting of the 3d orbitals and in the judicious choice of TM ion. Since the publication of the first 3d-based SIM, which was based on Fe(ii), many other contributions have been made to this field, using different first row TM ions, and exploring varied coordination environments for the paramagnetic ions.

Preparation, electrochemical behavior and variable temperature magnetic properties of transition metal complexes containing 2-phenyl-4,5-di-(2-pyridyl)imidazole

We report the synthesis of three new complexes featuring first row transition metal ions (Mn2+, Fe2+, or V3+) and a 2-pyridyl-substituted imidazole ligand. We investigate the electronic and magnetic properties of the complexes via electronic spectroscopy, cyclic voltammetry, superconducting quantum interference device magnetometry and density functional theory calculations. Complexes with Fe2+ or V3+ are redox active, and we observe spin crossover from the variable temperature magnetic susceptibility data for the complex with Fe2+. We intend to use these complexes as precursors to bimetallic mixed-valent materials.

Reduced fluorenoazomethine based photoluminescence turn-on sensors for transition metal ions

Photoluminescence (PL) turn-on sensors for first row transition metal ions have been developed based on reduced fluorenoazomethine podands. The bare podands, which are in the PL-quenched state, are quantitatively converted into an emissive charge-transfer species upon metal-ion binding, leading to a remarkable PL enhancement.

Low pH Electrolytic Water Splitting Using Earth-Abundant Metastable Catalysts That Self-Assemble in Situ

Typical catalysts for the electrolysis of water at low pH are based on precious metals (Pt for the cathode and IrO2 or RuO2 for the anode). However, these metals are rare and expensive, and hence lower cost and more abundant catalysts are needed if electrolytically produced hydrogen is to become more widely available. Herein, we show that electrode-film formation from aqueous solutions of first row transition metal ions at pH 1.6 can be induced under the action of an appropriate cell bias and that in the case of cobalt voltages across the cell in excess of 2 V lead to the formation of a pair of catalysts that show functional stability for oxygen evolution and proton reduction for over 24 h. We show that these films are metastable and that if the circuit is opened, they redissolve into the electrolyte bath with concomitant O2 and H2 evolution, such that the overall Faradaic efficiency for charge into the system versus amounts of gases obtained approaches unity for both O2 and H2. This work highlights the ability of first row transition metals to mediate heterogeneous electrolytic water splitting in acidic media by exploiting, rather than trying to avoid, the natural propensity of the catalysts to dissolve at the low pHs used. This in turn we hope will encourage others to examine the promise of metastable electrocatalysts based on abundant elements for a range of reactions for which they have traditionally been overlooked on account of their perceived instability under the prevailing conditions.

Subcomponent self-assembly of polymer chains based on dynamic and geometrical coordination diversity of the first row transition metal ions

The subcomponent self-assembly of polymer chains based on the dynamic/geometrical coordination diversity of first row transition metal ions is reported. A well-defined NH2-functional hydrophilic block copolymer, Ni(II), Cu(II) and Zn(II) and a salicylaldehyde derivative are selected as subcomponents. The imine formation and self-assembly are followed using 1H NMR, DLS, GPC, and UV-vis spectroscopy. The results demonstrate that the subcomponent self-assembly strongly depends on the coordination stability constants and geometries of these metal ions. Ni(II) induces interchain coordination, and rapid phase transition to macro-phase separation but with the lowest autocatalysis efficiency. However, Cu(II) ions induce intrachain coordination with the most remarkable autocatalysis, and the delaying of the phase transition to form well-defined hybrid nanoparticles. The behaviour with Zn(II) ions is in between that with Ni(II) and Cu(II) ions. This striking differentiation demonstrates that the dynamic/geometrical coordination diversity of the abundant first row transition metal ions effectively control the subcomponent self-assembly of polymer chains, and thus the hierarchical nanostructures of dative metal–polymer hybrid functional materials.

ChemInform Abstract: Coordination Polymers and Metal‐Organic Frameworks Derived from 4,4′‐Dicarboxy‐2,2′‐bipyridine and 4,4′,6,6′‐Tetracarboxy‐2,2′‐bipyridine Ligands: A Personal Perspective

AbstractReview: 68 refs.

Synthetic, spectroscopic, magnetic and thermal aspects of drug based metal complexes derived from 1st row transition metal ions

A newly synthesized ligand, 5-((1H-indol-1-yl)methyl)quinolin-8-ol (L) was characterized by 1H NMR, 13C NMR, DEPT-135 and IR spectroscopic techniques. The synthesized metal complexes were characterized using elemental analyses, (infrared, electronic and FAB mass) spectra, magnetic measurements and thermogravimetric analyses. Kinetic parameters such as order of reaction (n) and the energy of activation (Ea) are reported using the Freeman–Carroll method. The pre-exponential factor (A), the activation entropy (ΔS#), the activation enthalpy (ΔH#) and the free energy of activation (ΔG#) were calculated. Metal complexes are also screened for their in vitro antibacterial activity against a range of Gram-positive and Gram-negative organisms.

Coordination Polymers and Metal–Organic Frameworks Derived from 4,4'-Dicarboxy-2,2'-bipyridine and 4,4',6,6'-Tetracarboxy-2,2'-bipyridine Ligands: A Personal Perspective

Presented herein is a personal overview of some of the contributions we have made over recent years to coordination polymer chemistry employing 2,2'-bipyridine-polycarboxylic acid ligands in conjunction with first row transition, main group or lanthanide metal ions. Primarily the discussion is centred upon the two ligands with which we have enjoyed the most success: 4,4'-dicarboxy-2,2'-bipyridine (4,4'-H2dcbp) and 4,4',6,6'-tetracarboxy-2,2'-bipyridine (4,4',6,6'-H4tcbp). Initial discussion is focused upon the synthetic aspects of ligand formation and their structural characterisation and then moves on to the synthesis of metal complexes incorporating these ligands and the coordination polymers they form. Where possible the discussion is presented from a synthetic and structural perspective with highlight given to the pertinent properties of the coordination polymers formed e.g. thermal behaviour, magnetic, luminescent or small molecule sorption properties. We end the review with some conclusions and highlight some current work with a view to future research.

Aqueous Molecular Sieving and Strong Gas Adsorption in Highly Porous MOFs with a Facile Synthesis

Aqueous molecular sieving is demonstrated in a new series of isostructural metal organic frameworks based on the perylene tetracarboxylate (PTC) ligand. The frameworks can be formed in water at room temperature with Mg, Ni, and other first row transition metal ions and adopt a highly porous topology that results in predicted surface areas of over 2000 m2 g–1 and periodic channels of around 6 A in diameter. Unusually, the M-PTC MOFs are highly resistant to moisture and can be readily synthesized on multigram scales. The frameworks have been shown to exhibit molecular sieving in the absorption from mixtures of organic molecules at low aqueous concentrations, with an application demonstrated on a dangerous water-borne herbicide, Paraquat. Ni-PTC also exhibits a structural flexibility that leads to strong and selective gas adsorption characteristics, with an IAST selectivity of 300 for carbon dioxide being adsorbed over nitrogen. Binding enthalpies for hydrogen and carbon dioxide are also very strong in compa...

Fine tuning of the coordination environments and magnetic properties of first row transition metal ions with 5-methylisophthalate and 2,2′-bipyridine/phenanthroline

Twelve coordination compounds of Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+, with mixed organic ligands 5-methylisophthalic acid, 2,2′-bipyridine or phenanthroline, have been hydrothermally synthesised and characterised. The magnetic properties of the Mn2+, Co2+, Ni2+ and Cu2+ compounds have been investigated. Structure analysis shows that the assemblies with a bridging ligand possessing a smaller methyl group (compared to the tert-butyl group) afford coordination compounds containing multinuclear metal centres and structures of higher dimension. The result shows that the structures and properties of the metal–organic materials can be finely tuned by the substituent on the organic bridging ligands.

Wide-Bore Capillary Hydrodynamic Chromatography with ICP-MS Detection for Evaluation of Lanthanide Uptake by Molecular Aggregates

Wide-bore capillary hydrodynamic chromatography (W-HDC) resolves analytes on the basis of a difference in the extent of radial diffusion simply by their passage through an empty capillary. The combination of this method with ICP-MS proves efficient for the evaluation of the interaction of metal ions with molecular aggregates. Lecithin vesicles are suitable molecular aggregates for the uptake of the lanthanide ions in the presence of the first row transition metal ions, suggesting that the present method is applicable to the screening of the molecular aggregate system suitable for selective extraction of a particular targeted small molecule. The visual inspection of the elution profiles gives us qualitative but useful information on the interaction between the vesicle and metal ions. In addition, studying the slope of the front edge of an elution curve provides more quantitative implications.

Terpyridines and their Complexes with First Row Transition Metal Ions:Cytotoxicity, Nuclease Activity and Self-Assembly of Biomacromolecules

Transition metal complexes with terpyridine ligands have attracted a widespread interest with respect to biomedical applications: [(tpy)PtCl]Cl and [(tpy)RuCl(3)] are potent anti-tumor agents with activities comparable to those of cisplatin and carboplatin. The Ru(II) complexes feature a high potential as reactive probes for DNA oxidation; whereas, luminescent Ir(III), Pt(II) or Eu(III) complexes have been utilized in biolabeling applications. Besides complexes based on heavy second or third row transition metal ions, remarkable results have been obtained with respect to the development of new types of metallodrugs, based on the naturally more abundant and intrinsically less toxic first row transition metal ions (e.g. Fe(II), Cu(I/II), Zn(II)). The perspective of these complexes in particular with respect to future biomedical applications in chemotherapy and cleavage of nucleic acids is evaluated in this review.