3d Metal Ions Research Articles

Tuning of High Spin Ground State and Slow Magnetic Relaxation within Trimetallic Cyanide‐Bridged {NiIIxCoII9−x[WV(CN)8]6} and {MnIIxCoII9−x[WV(CN)8]6} Clusters

Two series of trimetallic {NiII x CoII 9-x [WV (CN)8 ]6 } (NiCoW) and {MnII x CoII 9-x [WV (CN)8 ]6 } (MnCoW) (x=1-8) crystalline solid-solutions were constructed and systematically studied by SEM EDX, single-crystal X-ray diffraction (SC XRD), and magnetic measurements. The atomic Ni:Co:W and Mn:Co:W ratios in the solid state follow the stoichiometric concentration in the mother MeOH solutions fairly well. The structural studies revealed a definite strong tendency of smaller 3d ions to locate in the central [M(μ-NC)6 ] moiety of the skeleton: NiII over the CoII and CoII over MnII . In contrast, the external fac-[M(μ-NC)3 (MeOH)3 ] are consecutively occupied by the mixture of 3d metal ions, accessible according to the stoichiometry of the mother solutions. The DC magnetic χT(T) and M(H) curves illustrate the continuous tendency of change with x along both series, nicely reproducing the changes of the theoretical high spin in the ground state Sgr , assuming the ferromagnetic HS CoII -NC-WV and antiferromagnetic MnII -NC-WV interactions established by numerous literature reports. The AC magnetic measurements indicate the occurrence of slow magnetic relaxation, with the highest energy barrier ΔE/kB of 26 K for the Ni6 Co3 W6 congener and of 17 K for the Mn6 Co3 W6 congener, and relatively large values of distribution parameter α. The values of ΔE are correlated with possible anisotropy of distribution of fac-[CoII (μ-NC)3 (MeOH)3 ] moieties at the external corners of the cube substructure.

Thermochemically Consistent Free Energies of Hydration for Di- and Trivalent Metal Ions.

This paper uses the relationship between the standard half reduction potential, the third ionization potential, and the free energies of hydration (Δ Ghyd) of M2+ and M3+ ions to calculate new values of Δ Ghyd for M2+ and M3+ ions. The numbers are "thermochemically consistent"; i.e., all numbers agree with the applied thermochemical cycle. This enables the tabulation of many Δ Ghyd derived mainly from the data compiled by Marcus, but consistent with Δ Ghyd(H+) = 1100 kJ/mol and SHE = 4.44 V. The accuracy of the new values of Δ Ghyd(M3+) is by definition similar to the accuracy of the experimental hydration energy of the Δ Ghyd(M2+) used for calculation, and vice versa, i.e. the new data have the same accuracy or higher than previously reported. As a result, the literature values for Cr3+ and Au3+, and Pd2+ are substantially revised. The approach also allows the calculation of new Δ Ghyd for metal ions such as Mn3+, Ti2+, Ag3+, Ni3+, Cu3+, and Au2+ and the theoretically interesting but experimentally inaccessible +2 ions of lanthanides. The new numbers enable a discussion of the previously unreported trend in Δ Ghyd(M3+) for the 3d metal ions, which relates to the ligand field stabilization energies and effective nuclear charge as for the M2+ ions. The new tabulated values should be accurate with the applied assumptions to within 10 kJ/mol and may be of value for other thermochemical calculations, for interpretation of the aqueous trend chemistry of the metal ions, and as benchmarks for theoretical chemistry.

Trace Level Recognition of Zn2+ and Cd2+ by Biocompatible Chemosensor inside Androecium, Diagnosis of Pick's Disease from Urine and Biomimetic β-Cell Exocytosis.

Two chemosensors with varying substitution have been synthesized for selective detection of d10 metal ion analyte Zn2+ and Cd2+ by fluorometric method from aqueous medium at very low limit of detection. Density functional theory (DFT)-based Loewdin spin population analysis reveals that methoxy-substituted chemosensor is much stronger donor than bromo-substituted chemosensor. Eventually, bromo and methoxy substituted chemosensors are moderate and strong donor, respectively, toward selective detection of Cd2+ and Zn2+ by luminescence induced phenomenon (blue for Cd2+ and cyan for Zn2+). The mechanism of sensing could be explained by PET-CHEF-C = N isomerization-ILCT pathway. 1H NMR, ESI-MS and FT-IR has been carried out in order to explore the selective ion sensing mechanism. Intracellular detection of Zn2+ and Cd2+ has been carried out inside androecium (filament and pollens) of Tecoma Stans. Extracellular detection of Zn2+ for yeast cells represents the bio mimetic model experiments toward β-cells exocytosis as a marker of diabetes mellitus. The unprecedented and novel feature of the present biocompatible chemosensor is its application as biosensor to detect in vivo Zn2+ from human urine specimen which could be a next generation diagnostic tool for Pick's disease.

Optical properties and photocatalytic activity of nanocrystalline TiO2 doped by 3d-metal ions

Optical properties and photocatalytic activity of nanocrystalline TiO2 doped by 3d-metal ions

Multicomponent Self-Assembly of Metallo-Supramolecular Macrocycles and Cages through Dynamic Heteroleptic Terpyridine Complexation.

Spontaneous formation of the heteroleptic cadmium(II) bis(terpyridine) complex under ambient conditions can be achieved by a combination of 6,6''-di(2,6-dimethoxylphenyl)-substituted and unsubstituted terpyridine-based ligands. Building on this dynamic heteroleptic complexation, diverse metallo-supramolecular macrocycles and cages were readily assembled in quantitative yields from the predesigned multicomponent systems. The complementary ligation reinforced self-recognition to facilitate the shape-dependent self-sorting of a four-component dynamic library into two well-defined parallelograms. In addition, the subtle lability difference between homoleptic and heteroleptic complexes led to the site-selective CdII -ZnII transmetalation in the Sierpiński triangle. Facile construction of a dodecanuclear tetrahedral metallocage was also realized by using two self-recognizable tritopic building blocks. The photophysical study of the metallo-supramolecules assembled from the d10 metal ions revealed intense ligand-based photoluminescence in solution. The self-assembly strategy described here provides an efficient methodology for building pre-programmable, sophisticated supramolecular architectures furnished with photoactivity.

Metal Coordination to Ligand-Modified Peptide Nucleic Acid Triplexes.

A challenging goal in nanotechnology is the precise and programmable arrangement of specific elements in nanosystems in the three-dimensional space. The use of ligand-modified nucleic acids represents an accurate and selective tool to achieve this goal when it comes to metal ion organization. The synthesis of peptide nucleic acid (PNA) monomers that contain ligands instead of nucleobases makes possible the creation of metal-mediated alternative base pairs and triplets at specific locations in PNA duplexes and triplexes, respectively. We report the formation of four- and six-coordinate metal complexes between PNA triplexes modified with 2,2'-bipyridine (Bpy) or 8-hydroxyquinoline (Q) ligands and 3d metal ions. These metal complexes function as alternative base triplets or pairs in that they increase the thermal stability of the triplexes if the stability constants of the metal complexes are relatively high. The increase in the triplex melting temperature correlates with the stability constants of the metal complexes with ligand-containing PNA determined by UV-vis titrations. The metal complexes coordinate two or three ligands although three bidentate ligands are in close proximity of each other within a triplex. Metal coordination to ligand-modified PNA triplexes was further studied by electron paramagnetic resonance (EPR) spectroscopy and circular dichrosim (CD) spectroscopy. EPR spectroscopy indicated the formation of a square planar [CuQ2] complex between Cu2+ and Q-containing PNA triplex. Taken together, the spectroscopic results indicate that in the presence of 1 equiv of Fe2+ or Ni2+ the majority, but not all, of the Bpy-containing PNA triplexes contain [MBpy3] complexes, with a minority of them being metal free. We attribute this behavior to a supramolecular chelate effect exerted by the triplex, which favors the formation of tris-ligand complexes, that is balanced by the steric interactions between the metal complex and the adjacent nucleobase triplets, which decrease the stability of the complex and triplex. In contrast, the very high stability of square planar [MQ2] complexes of Cu2+ and Ni2+ leads to formation of bis-ligand complexes instead of tris-ligand complexes with Q3-containing PNA triplexes. The metal-containing PNA triplexes have a terminal l-lysine and adopt a left-handed chiral structure in solution. The handedness of the PNA triplex determines that of the metal complexes formed with the Bpy-containing PNA triplexes.

Structural variation and luminescence properties of d10 metal ions complexes from 5-Aminotetrazolate ligand

Three new d10 complexes with 5-aminotetrazolate (5-HATZ), [Zn2(5-ATZ)3(N3)]n (1), {[Cd6(5-ATZ)8Cl5]n·(H2O)4}n (2), and {[Cd12(5-ATZ)12Cl8(N3)4]·2H2O}n (3) have been obtained under hydrothermal conditions and structurally characterized. Single-crystal X-ray structural analyses reveal that complex 1 can be rationalized to be 3D dia topological nets with the metal ZnII centers acting as four-connected nodes and L acting as linkers, and the Schläfli symbol is 66, while 2 exhibits a 3D architecture based on six crystallographically independent hexahedral coordinated CdII centers linked by 5-ATZ anion and Cl anion. Complex 3 also possesses a 3D network linked by 5-ATZ anion, Cl anion as well as N3 anion. The ligand 5-ATZ anion adopts μ1,4-bridging coordination mode in complex 1, μ1,2,3, μ1,2,4, μ1,2,3,4-bridge coordination mode in complex 2, while μ1,2,4, μ1,2,3,4-bridge coordination mode in complex 3. Also, the fluorescent properties of complexes 1 and 2 have been investigated.

Role of (1,3) {Cu-Cu} Interaction on the Magneto-Caloric Effect of Trinuclear {CuII-GdIII-CuII} Complexes: Combined DFT and Experimental Studies.

Molecular refrigeration is found to be of great interest in the field of coordination chemistry, and GdIII ion based complexes are particularly attractive, as they exhibit a large magneto-caloric effect (MCE). As the magnetic coupling in GdIII clusters is difficult to control, other avenues to enhance the MCE values have been explored and incorporation of 3d metal ions in the cluster aggregation with GdIII yielding {3d-Gd} clusters are targeted. Among the transition-metal ions, the CuII ion is particularly attractive, as it does not possess any anisotropy, and in this regard, several di- and polynuclear {Cu-Gd} clusters are reported to yield attractive MCE values. While the role of near-neighbor {Cu-Gd} interactions in the MCE has been explored in detail, how the next-nearest-neighbor interaction influences the MCE has not been explored. To explore the importance of next-nearest-neighbor (1,3) {Cu-Cu} interaction, we have undertaken detailed density functional studies on five trinuclear {CuII-GdIII-CuII} complexes that are reported in the literature. In addition, we also report the synthesis and magnetic and EPR studies of a novel complex [(CuSALen)2Gd(NO3)3] (6; where SALen is N,N'-ethylenebis(salicylaldiminato)). Both magnetic and EPR studies reveal an S = 9/2 ground state for 6 with a very small zero-field splitting parameter (+0.01 cm-1), which aid in the achievement of a large MCE value for this molecule. Magnetization data collected for 6 yield a magnetic entropy change (-ΔSm) of 17 J kg-1 K-1 at 3.5 K by employing a 7 T magnetic field. Our calculations on all six complexes reveal that {Cu-Gd} exchange is ferromagnetic in nature, while the next-nearest-neighbor {Cu-Cu} exchange is found to vary from a weak ferromagnetic to a moderate antiferromagnetic interaction. In all of the cases studied, simulated susceptibility data are in excellent agreement with the experimental data, offering confidence in the computed J values. In addition, we have developed a mechanism of magnetic coupling for {CuII-GdIII-CuII} trinuclear complexes, where the role of formally empty 5d, 6s, and 6p orbitals of GdIII ion is established. In particular, our studies reveal that the next-nearest-neighbor {Cu-Cu} interaction is strongly correlated to Cu-Gd-Cu angle, with both smaller and larger angles yielding stronger antiferromagnetic exchange. The antiferromagnetic {Cu-Cu} interaction diminishes the gap between the ground S = 9/2 state and first excited S = 7/2 state, leading to enhancement of MCE values. In contrast to the general belief that weak interactions are desired for large MCE, our study advocates targeting a stronger antiferromagnetic {Cu-Cu} interaction to obtain larger MCE values in this class of clusters.

Thiocarbamoylation of Chlorosulfonated Polystyrene for Preparing Sorbents for Noble Metal Ions

A new sorbent for noble metal ions, ensuring selective recovery of Au(III) ions from aqueous solutions containing interfering 3d metal ions, was suggested. The new functional derivative, poly(thiocarbamoylsulfostyre ne), was prepared by treatment of poly(chlorosulfostyrene) with thiourea. At the total degree of functionalization with sulfo and thiourea groups of up to 1.0, the degree of thiocarbamoylation can be controlled in the range from 10 to 75%. The composition and structure of the polymer-analogous transformation products were characterized by elemental analysis, Fourier IR spectroscopy, and thermal gravimetric analysis with IR identification of the decomposition products. Evaluation of the sorption activity of poly(thiocarbamoylsulfostyrene) has shown that the sorbent takes up Au(III) ions virtually quantitatively with high selectivity from an aqueous solution containing Co(II), Fe(III), Pd(II), and Ni(II) ions.

Ibandronate metal complexes: solution behavior and antiparasitic activity.

To face the high costs of developing new drugs, researchers in both industry and academy are looking for ways to repurpose old drugs for new uses. In this sense, bisphosphonates that are clinically used for bone diseases have been studied as agents against Trypanosoma cruzi, causative parasite of Chagas disease. In this work, the development of first row transition metal complexes (M=Co2+, Mn2+, Ni2+) with the bisphosphonate ibandronate (iba, H4iba representing the neutral form) is presented. The in-solution behavior of the systems containing iba and the selected 3d metal ions was studied by potentiometry. Mononuclear complexes [M(Hxiba)](2-x)- (x=0-3) and [M(Hiba)2]4- together with the formation of the neutral polynuclear species [M2iba] and [M3(Hiba)2] were detected for all studied systems. In the solid state, complexes of the formula [M3(Hiba)2(H2O)4]·6H2O were obtained and characterized. All obtained complexes, forming [M(Hiba)]- species under the conditions of the biological studies, were more active against the amastigote form of T. cruzi than the free iba, showing no toxicity in mammalian Vero cells. In addition, the same complexes were selective inhibitors of the parasitic farnesyl diphosphate synthase (FPPS) enzyme showing poor inhibition of the human one. However, the increase of the anti-T. cruzi activity upon coordination could not be explained neither through the inhibition of TcFPPS nor through the inhibition of TcSPPS (T. cruzi solanesyl-diphosphate synthase). The ability of the obtained metal complexes of catalyzing the generation of free radical species in the parasite could explain the observed anti-T. cruzi activity.

Colorimetric Chemosensors for d-metal Ions: Short Communication

Parallel advance study in colorimetric and fluorescent chemosensing have sparked in the development of chemosensors. Among the chemosensors the naked eye ones i.e. the colorimetric chemosensors are most important because they don’t involve either any costly instrument or any pretreatment of the sample. Present review article covers colorimetric chemosensors for d-metal ions have been widely applied in many promising fields such as, pharmacology, biology and environmental sciences. These chemosensors are enable to sense d-metal ions especially hazardous d-metal ions that is significantly impacting the application in the field of healthcare, agriculture and environment. This review covers in depth study of research publication.

Spectroscopic, electrochemical and photovoltaic properties of Pt(ii) and Pd(ii) complexes of a chelating 1,10-phenanthroline appended perylene diimide.

In this study, a bis-chelating bridging perylene diimide ditopic ligand, namely N,N'-di(1,10-phenanthroline)-1,6,7,12-tetrakis-(4-methoxyphenoxy)perylene tetracarboxylic acid diimide (1), was synthesized and characterized. Further reactions of 1 with d8 metal ions such as Pt(ii) and Pd(ii) having preferential square-planar geometry afforded the novel triads [(Cl2)M(ii)-(1)-M(ii)(Cl2)] where M(ii) = Pt(ii) (2), and Pd(ii) (3), respectively. The isolated triads and the key precursor were fully characterized by FT-IR, 1D-NMR (1H NMR and 13C DEPT NMR), 2D-NMR (1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC), MALDI-TOF mass and UV/Vis spectroscopy. The electrochemical properties of 1, 2 and 3 were investigated by cyclic voltammetry as well as in situ spectroelectrochemistry and also in situ electrocolorimetric measurements. These compounds were shown to exhibit net colour changes suitable for electrochromic applications. The compounds exhibited remarkably narrow HOMO-LUMO gaps, leading to their ease of reduction at low negative potentials. More importantly, dye-sensitized solar cells (DSSCs) were also fabricated using 1-3 to clarify the potential use of these complexes as a sensitizer. Analysis of the experimental data indicated that 2 has good potential as a sensitizer material for DSSCs.

Realization of toroidal magnetic moments in heterometallic 3d-4f metallocycles.

Toroidal arrangements of magnetic moments are realized in heterometallic Ln6Cu6 (Ln = Tb and Dy) macrocycles thanks to the magnetic coupling between lanthanide and 3d metal ions.

Mapping the Assembly of Metal-Organic Cages into Complex Coordination Networks.

Structural transformations of supramolecular assemblies play an important role in the synthesis of complex metal-organic materials. Nonetheless, often little is known of the assembly pathways that lead to the final product. This work describes the conversion of cubic metal-organic polyhedra to connected-cage networks of varying topologies. The neutral cubic cage assembly of formula {Pd3 [PO(NiPr)3 ]}8 (PZDC)12 has been synthesized from {Pd3 [(NiPr)3 PO](OAc)2 (OH)}2 ⋅2 (CH3 )2 SO and 2,5-pyrazenedicarboxilic acid (PZDC-2H). This 42-component self-assembly is the largest known among the neutral cages with PdII ions. The cage contains twenty-four vacant carboxylate O-sites at the PZDC ligands that are available for further coordination. Post-assembly reactions of the cubic cage with FeII and ZnII ions produced cage-connected networks of dia and qtz topologies, respectively. During these reactions, the discrete cubic cage transforms into a network of tetrahedral cages that are bridged by the 3D metal ions. The robustness of the [Pd3 {[PO(NiPr)3 }]3+ molecular building units made it possible to map the post-assembly reactions in detail, which revealed a variety of intermediate 1D and 2D cage networks. Such step-by-step mapping of the transformation of discrete cages to cage-connected frameworks is unprecedented in the chemistry of coordination driven assemblies.

Synthesis, structure characterization and biological studies on a new aromatic hydrazone, 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-2,2-dimethyl-1,3-dioxane-4,6-dione, and its transition metal complexes

A new aromatic hydrazone 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-2,2-dimethyl-1,3-dioxane-4,6-dione has been synthesized by Japp-Klingemann reaction from diazotized 4-aminoantipyrine and Meldrum's acid. A few 3d-metal ion complexes of this hydrazone were synthesized. The compound and its complexes were characterized by UV–Visible, 1H NMR, ESR, Mass spectral, molar conductance and magnetic susceptibility measurements. The compound was found to exist in hydrazone form in solid state and solution from SXRD and 1H NMR study. The influence of pH on the molecule was studied and found that it shows azo/enol-hydrazone tautomerism in solution. This molecule act as a univalent tridentate ligand and the complexes were assigned to have a 1:2 stoichiometry (M:L). The antioxidant properties of the compounds were explored by DPPH assay and found that the ligand possesses better free radical scavenging effect than the complexes. Antimicrobial activities of these compounds were investigated and were found to be active.

Quantum Chemical Simulation of the Interaction of Functional Groups in Polyurethanes with 3d-Metal Ions During Their Extraction from Aqueous Solutions

The interaction of the functional groups in the polyurethane foam adsorbent Penopurm® with the cations of some 3d-metals upon their extraction from aqueous solutions has been studied by atomic emission spectroscopy, UV/Vis and vibrational IR spectroscopy, and quantum chemical simulation using density functional theory. Penopurm® absorbs 3d-metal cations from aqueous solutions in the pH range 5–7. Some spectral criteria have been found indicating a predominant interaction of Ni2+ ions with various fragments of the polyurethane foam structure.

Using invariom modelling to distinguish correct and incorrect central atoms in `duplicate structures' with neighbouring 3d elements.

Modelling coordination compounds has been shown to be feasible using the invariom method; for the best fit to a given set of diffraction data, additional steps other than using lookup tables of scattering factors need to be carried out. Here such procedures are applied to a number of `duplicate structures', where structures of two or more supposedly different coordination complexes with identical ligand environments, but with different 3d metal ions, were published. However, only one metal atom can be plausibly correct in these structures, and other spectroscopic data are unavailable. Using aspherical scattering factors, a structure can be identified as correct from the deposited Bragg intensities alone and modelling only the ligand environment often suffices to make this distinction. This is not possible in classical refinements using the independent atom model. Quantum-chemical computations of the better model obtained after aspherical-atom refinement further confirm the assignment of the element in the respective figures of merit.

Structural studies and biological activity evaluation of Pd(II), Pt(II) and Ru(II) complexes containing N‐phenyl, N`‐(3‐triazolyl)thiourea

[MCl(H2L)(OH2)]·1.5H2O (M = Pd(II) (1) and Pt(II) (2)) and [Ru(H2L)2(OH2)2]·3H2O (3) (H3L: N‐phenyl, N`‐(3‐triazolyl)thiourea) were synthesized, characterized and tested for their antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria. The thiourea derivative is coordinated to Mn+ ions as a mono‐negatively N,S‐bidentate ligand via the enolization of C = S group and triazole N center. The density functional theory calculations reveal that presence of a water molecule in a trans position to triazole ring increased the stability of d8 metal ions complexes via the formation of strong Cl…NH intramolecular H‐bond. The cis‐Ru(II)‐isomer with two isoenergetically H2L− molecules are more stable than the trans‐analog. Coordination of H3L to Ru(II) ion did not alter the toxicity of the free ligand, while the interaction with the d8 metal ions gave rise to inactive compounds.

Comparing Pt II - and Pd II -nucleobase coordination chemistry: Why Pd II not always is a good substitute for Pt II

Abstract As is well established, numerous similarities exist as far as reactivity patterns and structural features of the d8 metal ions M = Pd2+ and Pt2+ are concerned. Here reactions of metal complexes of type cis-[M(a)2X2] (a = NH3 or (a)2 = diamine or diimine; X = monodentate or X2 = bidentate leaving groups) with nucleobases, the constituents of nucleic acids, are discussed and differences regarding intrinsic stability of the starting compounds, kinetics of formation of products, thermodynamics of products, as well as donor site selectivity are pointed out. It is concluded that PdII complexes representing strict or close analogues of established antitumor PtII drugs of the Cisplatin-type, if active under in vivo conditions at all, are unlikely to have a similar mode of action as their PtII congeners. Relationships to supramolecular constructs containing cis-[M(a)2]2+ entities are likewise discussed.

Low-Pressure Selectivity, Stepwise Gas Sorption Behaviors, and Luminescent Properties (Experimental Findings and Theoretical Correlation) of Three Zn(II)-Based Metal–Organic Frameworks

In this report, three new luminescent metal–organic frameworks (LMOFs), [Zn(L1)2]·CH3CN (1), [Zn(L1)2] (2), and [Zn(L1)(L2)0.5]·NMP (3) (HL1 = 6-aminonicotinic acid; H2L2 = terephthalic acid; and NMP = N-methyl-2-pyrrolidone), have been solvothermally synthesized based on d10 metal ion Zn(II) and free organic ligands (HL1 and H2L2) in different solvent systems, all of which have been fully characterized. Single crystal data reveal that 1 and 2 are two 2D isomeride but with different space groups, which is caused by the different solvent systems during the synthesis procedure. The introduction of the bridging ligand H2L2 in the solvent system of 2 produces 3 with the 3D microporous framework. The gas sorption exploration of 3 shows an interesting stepwise gas sorption behavior and attractive low-pressure selectivity between CO2 and CH4, which may be used as a potential material to separate the CO2 from the natural gas. In addition, the luminescent properties of the free ligands and 1–3 have been investigat...