Metal-ligand Complexes Research Articles

Theoretical investigations into the Spectrophotometrically Analyzed Niobium (V)-6-Chloro-3-hydroxy-7-methyl-2-(2’-thienyl)-4H-chromen-4-one Complex

Abstract Pentavalent niobium cation forms a stable yellow-colored binary complex with 6-chloro-3-hydroxy-7-methyl-2-(2’-thienyl)-4H-chromen-4-one (CHMTC) in the ratio of 1:2. The complex is quantitatively extractable into carbon tetrachloride from HClO4 solution maintained at pH 1.26–1.75 and strictly adheres to Beer’s law as verified by the Ringbom plot with an optimized range of determination as 0.385–1.211 ppm of Nb(V). The ligand-metal complex system shows good precision, accuracy, sensitivity, and selectivity and handles satisfactorily the analysis of several samples of varying complexity. The results are highly reproducible as confirmed by statistical data. The stability of the complex is theoretically confirmed with the help of HOMO-LUMO values and the energy gap [for CHMTC, ΔE gap = 3.62 V and for Nb(V)-CHMTC Complex, ΔE gap = 2.97 eV]. The reactivity descriptors were calculated for detailed computational study to probe into the chemical behavior of the studied ligand and its complex. Further, mapped electrostatic potential diagrams help in justifying the donor sites of CHMTC ligand which is in accordance with the analytical findings.

On-surface synthesis of ballbot-type N-heterocyclic carbene polymers.

N-Heterocyclic carbenes (NHCs) are established ligands for metal complexes and surfaces. Here we go beyond monomeric NHCs and report on the synthesis of NHC polymers on gold surfaces, consisting of ballbot-type repeating units bound to single Au adatoms. We designed, synthesized and deposited precursors containing different halogens on gold surfaces under ultrahigh vacuum. Conformational, electronic and charge transport properties were assessed by combining low-temperature scanning tunneling microscopy, non-contact atomic force microscopy, X-ray photoelectron spectroscopy, first-principles calculations and reactive force field simulations. The confirmed ballbot-type nature of the NHCs explains the high surface mobility of the incommensurate NHC polymers, which is prerequisite for their desired spatial alignment. The delicate balance between mobility and polymerization rate allows essential parameters for controlling polymer directionality to be derived. These polymers open up new opportunities in the fields of nanoelectronics, surface functionalization and catalysis.

Comparative Studies on Spectrophotometric Determination of Selected Heavy Metals in Environmental and Biological Samples with Synthetic Phenylhydrazones as Chromogenic Reagents

This work involves a comparative study on a simple, sensitive, selective and non-extractive Uv- Vis spectrophotometric method for the determination of cadmium, lead, chromium and arsenic in biological, soil and water samples using synthesized and characterized phenylhydrazones; [glutaraldehyde phenylhydrazone (GPH) and acetylpyridine-2,4-dinitrophenylhydrazone (APDH)] as the chromogenic reagents was developed. GPH and APDH were synthesized as new chromogenic analytical reagents for the direct UV-Vis spectrophotometric determination of the selected metals of interest in a slightly acidic pH of 6.5-7.5 and 20% dimethylformamide (DMF) solution to give stable coloured metal-ligand complexes. The reactions were instantaneous; the wavelengths of maximum absorptions were followed spctrophometrically and noted. The analytical properties of the reagent APGH on the metals (Cd, As, Pb, and Cr) revealed the wavelength of maximum absorption ranged between 385.0 (Cr) to 440.0nm for (Pb). The reagent APDH had molar absorptivities (L mol -1 cm -1 ) ranging from 2.006 x 10 4 (Pb) to 2.407 x 10 4 (Cd), a mole ratio of metal to ligand of 1:1, a detection limit (µg/g) ranging from 0.3272 (As) to 0.4456 (Cd) and the metal-ligand complex was stable for 0-36 hours. The reagent GPH revealed a wavelength of maximum absorption between 360.0 (Cr) to 395.0 nm for (Pb and As) at a working pH of 6.5 to 7.5 room temperature (37°C). The reagent GPH had a molar absorptivities (L mol -1 cm -1 ) ranging from 2.213 x 10 4 (Pb) to 2.460 x 10 4 (As), a mole ratio of metal to ligand of 2:1, the detection limit (µg/g) ranging from 0.3432 (As) to 0.5250 (Pb) and the metal-ligand complex was stable for 0-48 hours. Both reagents had a Beer’s law validity range (mgL -1 ) of 0.001 to 100. The Sandell’s sensitivities (µg/cm 2 ) ranged from 0000409 (As) to 0.00499 (Pb) for APDH and 0.00406 (As) to 0.00452 (Pb) respectively. Large excess of cations and anions as possible interferences up to 1

Applications of time‐resolved step‐scan Fourier‐transform infrared spectroscopy in revealing the light‐initiated reactions in condensed phases

AbstractStep‐scan Fourier‐transform infrared spectroscopy (ssFTIR) simultaneously provides the spectroscopic and kinetic information of a given reaction. ssFTIR has been extensively employed to acquire the transient absorption and emission spectra in gas phase for identifying unstable species, for example, various Criegee intermediates, and elucidating the dynamics and kinetics of the reaction, such as the molecular elimination dynamics of haloalkenes and the bimolecular reactions involving chlorine atoms and singlet oxygen atoms. In addition to gaseous studies, ssFTIR has been also utilized to record the time‐resolved difference spectra of the photochemical reactions in condensed phases, such as the photolysis of metal–ligand complexes, photocycles of the retinal proteins, coordination capability of solvents to unstable transient species, chemical reactions of atmosphere‐related molecules in aqua, and the exciplex dynamics of organic light emitting materials. Moreover, my group has pioneered the recording of the transient thermal infrared emission of gold nanostructures upon photoexcitation. The experimental setups and the working principles for probing the time‐resolved infrared absorption and emission in condensed phases will be revealed and a number of studies on chemical, biological, and materials systems will be described. These reported results demonstrate that ssFTIR is a versatile tool for exploring the properties of novel materials and photoreactions in condensed phases.

Infrared Ion Spectroscopic Characterization of the Gaseous [Co(15-crown-5)(H2O)]2+ Complex.

We report fingerprint infrared multiple-photon dissociation spectra of the gaseous monohydrated coordination complex of cobalt(II) and the macrocycle 1,4,7,10,13-pentaoxacyclopentadecane (or 15-crown-5), [Co(15-crown-5)(H2O)]2+. The metal-ligand complexes are generated using electrospray ionization, and their IR action spectra are recorded in a quadrupole ion trap mass spectrometer using the free-electron laser FELIX. The electronic structure and chelation motif are derived from spectral comparison with computed vibrational spectra obtained at the density functional theory level. We focus here on the gas-phase structure, addressing the question of doublet versus quartet spin multiplicity and the chelation geometry. We conclude that the gas-phase complex adopts a quartet spin state, excluding contributions of doublet species, and that the chelation geometry is pseudo-octahedral with the six oxygen centers of 15-crown-5 and H2O coordinated to the metal ion. We also address the possible presence of higher-energy conformers based on the IR spectral evidence and calculated thermodynamics.

Theoretical Assessment of the Ligand/Metal/Quadruplex Recognition in the Non-Canonical Nucleic Acids Structures.

Quadruplexes (GQs), peculiar DNA/RNA motifs concentrated in specific genomic regions, play a vital role in biological processes including telomere stability and, hence, represent promising targets for anticancer therapy. GQs are formed by folding guanine-rich sequences into square planar G-tetrads which stack onto one another. Metal cations, most often potassium, further stabilize the architecture by coordinating the lone electron pairs of the O atoms. The presence of additional nucleic acid bases, however, has been recently observed experimentally and contributes substantially to the structural heterogeneity of quadruplexes. Therefore, it is of paramount significance to understand the factors governing the underlying complex processes in these structures. The current study employs DFT calculations to model the interactions between metal cations (K+, Na+, Sr2+) and diverse tetrads composed of a guanine layer in combination with a guanine (G)-, adenine (A)-, cytosine (C)-, thymine (T)-, or uracil (U)-based tetrad layer. Moreover, the addition of 4-(3,4-dihydroisoquinolin-2-yl)-2-(quinolin-2-yl)quinazoline to the modeled quadruplexes as a possible mechanism of its well-exerted antitumor effect is assessed. The calculations imply that the metal cation competition and ligand complexation are influenced by the balance between electronic and implicit/explicit solvation effects, the composition of the tetrad layers, as well as by the solvent exposure to the surrounding environment expressed in terms of different dielectric constant values. The provided results significantly enhance our understanding of quadruplex diversity, ligand recognition, and the underlying mechanisms of stabilization at an atomic level.

Electronic Structure of the Complete Series of Gas-Phase Manganese Acetylacetonates by X-ray Absorption Spectroscopy.

Metal centers in transition metal-ligand complexes occur in a variety of oxidation states causing their redox activity and therefore making them relevant for applications in physics and chemistry. The electronic state of these complexes can be studied by X-ray absorption spectroscopy, which is, however, due to the complex spectral signature not always straightforward. Here, we study the electronic structure of gas-phase cationic manganese acetylacetonate complexes Mn(acac)1-3+ using X-ray absorption spectroscopy at the metal center and ligand constituents. The spectra are well reproduced by multiconfigurational wave function theory, time-dependent density functional theory as well as parameterized crystal field and charge transfer multiplet simulations. This enables us to get detailed insights into the electronic structure of ground-state Mn(acac)1-3+ and extract empirical parameters such as crystal field strength and exchange coupling from X-ray excitation at both the metal and ligand sites. By comparison to X-ray absorption spectra of neutral, solvated Mn(acac)2,3 complexes, we also show that the effect of coordination on the L3 excitation energy, routinely used to identify oxidation states, can contribute about 40-50% to the observed shift, which for the current study is 1.9 eV per oxidation state.

Open-Cage Fullerene as a Macrocyclic Ligand for Na, Pt, and Rh Metal Complexes.

An open-cage [60]fullerene derivative was prepared through Malaprade oxidation of a vicinal triol moiety as the key step. Above the 17-membered orifice, there is one carboxyl group. Three ketone carbonyl groups and one lactone carbonyl group are located on the rim of the orifice. The carboxylic and carbonyl oxygen atoms around the orifice act as strong polydentate ligands for a sodium ion. These oxygen atoms also react with [Rh(CO)2Cl]2 to form various isomeric rhodium complexes with comparable stability. The fullerene C═C bond on the rim of the orifice forms a stable platinum complex when treated with Pt(PPh3)4. Single crystal X-ray diffraction data reveal that one of the carboxylic oxygen atoms above the orifice forms a H-bond with the water molecule trapped in the cage.

Structural investigation, quantum chemical calculation, energy framework analysis and MIC studies of silver and cobalt complexes of 4-amino-N-(4, 6-dimethyl-2 pyrimidinyl) benzenesulfonamide in presence of secondary ligand

Silver and cobalt complexes of SMZ ligand (SMZ = 4-amino-N-(4, 6-dimethyl-2 pyrimidinyl) benzenesulfonamide) have been synthesized and characterized by elemental, FT-IR and 1H-NMR spectroscopy analysis. Due to the magnetic behaviour of the cobalt complex, it was characterized by EPR and magnetic susceptibility analysis. Single crystal X-ray diffraction (SC-XRD) study reveals the [Ag2(C12H14N4O2S)2(C6H7N), complex-1 crystallizes in orthorhombic space group Pbca, while [{Co(C12H13N4O2S)2(C5H5N)2}.(C5H5N)], complex-2 crystallizes in monoclinic space group C2/c. The SC-XRD analysis shows that silver in complex-1 is four-coordinate exhibiting distorted tetrahedral geometry, while cobalt in complex-2 is coordinated to six nitrogen’s leading to distorted octahedral geometry. Additionally, Hirshfeld surfaces and 2D fingerprint plots analysis shows that the H…H intermolecular contacts are the main contribution to the Hirshfeld surface area displaying values for complex-1 and complex-2 are 59.1% and 50% respectively (%H-H; complex 1 > Complex 2). In 3D energy frameworks analysis, complex-1, has shown the highest dispersion interaction energies than that of complex 2 [dispersion energy; -74.5 kJ mol-1 (complex-1) > -63.4 kJ mol-1 (complex-2)], Moreover, computational studies such as frontier molecular orbital (FMO), natural bond orbital (NBO) and Mulliken population analysis (MPA) were calculated using B3LYP method. Besides, The MIC data against panel of gram-positive and gram-negative organisms confirm that both the metal complexes of SMZ ligand possesses better inhibitory activities than that of SMZ ligand. The MIC data shows the silver complex exhibits comparatively better response towards the panel of the gram positive and gram negative bacteria. Furthermore, the molecular docking study agrees that the binding affinity of the complexes with 1BNA is higher than that of free SMZ ligand.

A Chemist's View on Electronic and Steric Effects of Surface Ligands on Plasmonic Metal Nanostructures.

ConspectusPlasmonic metal nanostructures have been extensively developed over the past few decades because of their ability to confine light within the surfaces and manipulate strong light-matter interactions. The light energy stored by plasmonic nanomaterials in the form of surface plasmons can be utilized to initiate chemical reactions, so-called plasmon-induced catalysis, which stresses the importance of understanding the surface chemistry of the plasmonic materials. Nevertheless, only physical interpretation of plasmonic behaviors has been a dominant theme, largely excluding chemical intuitions that facilitate understanding of plasmonic systems from molecular perspectives. To overcome and address the lack of this complementary understanding based on molecular viewpoints, in this Account we provide a new concept encompassing the well-developed physics of plasmonics and the corresponding surface chemistry while reviewing and discussing related references. Inspired by Roald Hoffmann's descriptions of solid-state surfaces based on the molecular orbital picture, we treat molecular interfaces of plasmonic metal nanostructures as a series of metal-ligand complexes. Accordingly, the effects of the surface ligands can be described by bisecting them into electronic and steric contributions to the systems. By exploration of the quality of orbital overlaps and the symmetry of the plasmonic systems, electronic effects of surface ligands on localized surface plasmon resonances (LSPRs), surface diffusion rates, and hot-carrier transfer mechanisms are investigated. Specifically, the propensity of ligands to donate electrons in a σ-bonding manner can change the LSPR by shifting the density of states near the Fermi level, whereas other types of ligands donating or accepting electrons in a π-bonding manner modulate surface diffusion rates by affecting the metal-metal bond strength. In addition, the formation of metal-ligand bonds facilitates direct hot-carrier transfer by forming a sort of molecular orbital between a plasmonic structure and ligands. Furthermore, effects of steric environments are discussed in terms of ligand-ligand and ligand-surface nonbonding interactions. The steric hindrance allows for controlling the accessibility of the surrounding chemical species toward the metal surface by modulating the packing density of ligands and generating repulsive interactions with the surface atoms. This unconventional approach of considering the plasmonic system as a delocalized molecular entity could establish a basis for integrating chemical intuition with physical phenomena. Our chemist's outlook on a molecular interface of the plasmonic surface can provide insights and avenues for the design and development of more exquisite plasmonic catalysts with regio- and enantioselectivities as well as advanced sensors with unprecedented chemical controllability and specificity.

Naphthalimide-benzimidazole conjugate towards “Turn-on” recoginition of Hg2+ in pure aqueous medium

A chemosensor, 6-(1-cyclohexyl-1H-benzo[d]imidazol-5-yl)-2-(2-(diethylamino)ethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (9), containing 1H,3H-benzo[de]isochromene-1,3-dione and 1-cyclohexyl-1H-benzo[d]imidazole moieties has been designed and found to be selective towards Hg2+ ions over-tested wide-range of metal ions. Compound 9 shows the absorption and emission peaks at 370 nm and 540 nm, respectively. The addition of Hg2+ ions to compound 9 (20 μM; H2O, pH = 7.4) prompted the formation of a 2:1 ligand–metal complex, 9-Hg2+, which shows a significant blue-shifted emission enhancement to 495 nm, due to the mechanism of ligand to metal charge transfer. The formation of compound 9 and Hg2+ ions complex has also been confirmed through mass spectrometry and 1H NMR titrations. The photophysical properties of the compound and its complex corroborated with Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) calculations.

Synthesis and X-ray crystal structures of mononuclear and multinuclear metal complexes of 3-substituted 4-cyanopyrazole ligands

Complexes of pyrazole ligands with a cyano substituent in the 4-position and alkyl or aryl substituents in the 3-position are reported, including mononuclear {M(HpzR,4CN)4X2 (X = Cl, M = Ni, R = t-Bu, c-Pr, Cy, Et; X = Cl, M = Co, R = Et, Cy, t-Bu; X = Br, M = Ni, R = i-Pr), [Pt(Hpzt-Bu,4CN)2Cl4], [Cu(HpzEt,4CN)2(H2O)2(NO3)2], M(HpzR,4CN)2Cl2 (M = Pt, Pd; R = t-Bu), [Pd(HpztBu,4CN)2Br2], [Pd(HpzPh2)2Cl2]}, dinuclear {(NEt4)2{Ni(pztBu,4CN)2(μ-pztBu,4CN)}2, {Pd(HpzPh2)(μ-pzPh2)Br}2}, and trinuclear {Ni3(pzPh)6, Pd3(pzPh,4CN)6} complexes, as well as a novel octanuclear complex {(NEt4)2[Ni8(pzPh,4CN)8Cl4(OH)6]}. Computational analysis is utilized to address the observation of only one isomer of tetrakis(pyrazole)dihalometal complexes. X-ray crystal structures are reported for two new pyrazoles and 18 metal complexes.

Synthesis, characterization of polymeric ligand-metal complexes and their biological activity properties

New members are joining to the Schiff bases family every day. In our study, firstly a new Schiff base was abbreviated as ligand (L) that was synthesized via condensation reaction between 3-aminonaphtalen-2-ol and 2,3-dihydroxybenzaldaheyde. Then, poly-ligand (PL) was obtained in basic medium in the presence of ammonium persulfate (NH4)2S2O8 via poly-condensation reaction by using L. Metal complexes were synthesized from the interaction of PL with various metal species such as Zn2+, Hg2+, Ni2+, Pb2+and Cu2+. The structures of compounds were confirmed by FT-IR, UV–Vis, 1HNMR and elemental analysis. Their SEM images were recorded at different sizes. Looking at the SEM images, it can be seen that the [Hg(PL)2] metal complex is similar to the red blood cells. Thermal analyses of PL and its metal complexes [M(PL)2] were performed. The biological properties such as DNA binding-cleavage, antioxidant and antibacterial activities of all synthesized compounds were investigated. According to the results, it was determined that such properties of its metal complexes were better than PL. For example, when the oxidative cleavage activity was examined, it was determined that [Cu(PL)2] complex completely cleaved the DNA and also it denatured all DNA at higher concentrations (≥100 ppm). DNA binding for the poly-ligand and its metal complexes bounded to CT-DNA in electrostatic mode. The antioxidant activity results showed that [Hg(PL)2] complex had a high inhibition value of 78.70±0.55% at 100 ppm. The [Hg(PL)2] complex was much more effective against all bacterial strains. The antibacterial activity of [Cu(PL)2] and [Zn(PL)2] complexes showed the highest activity against B. subtilis strain at the concentration of 62.5 µg/mL. DNA binding was determined from the UV–Vis spectra of the interaction of the PL and its metal complexes with CT-DNA. According to these UV–Vis results, it can be said that the poly-ligand and its metal complexes bounds to CT-DNA in electrostatic mode.

Synthesis, spectroscopic, and lead(II) binding behavior of three novel dibenzo-18-crown-6 hydrazones

Three novel hydrazonic derivatives of dibenzo-18-crown-6 were synthesized and their vibrational and electronic absorption spectroscopic properties thoroughly investigated. Their lead binding behaviors were also characterized and the observations rationalized by density functional theoretical modeling. All three cis-dihydrazonic compounds are of low overall molecular symmetry with their ether cavity adopting an open configuration at the global energy minima where the hydrazonic side-arms are electronically and vibrationally nonequivalent. Their optical absorption features are dominated by π → π * transitions where one side of the molecule exhibits Lewis acid behavior whereas the other behaves like a Lewis base. In addition to their sensitivity to pH, all three derivatives form stable 2:1 metal-ligand complexes with lead, due to coordination at the ether cavity, in addition to the hydrazone “backbone” and possibly the heterocyclic ring. The most stable lead complex is formed with the thiophene carboxylic acid hydrazide derivative due to favorable soft-soft interactions between lead and the ring-based sulfur atom.

Synthesis, structure of luminescence complexes and metalopolymers of Dy(III) and influence of the nature of substitutes on their emission

The new complexes of Dy (III) other β-diketones containing unsaturated, alkyl- and aryl- substituents were obtainted. Their heteroligand complexes with phenanthroline were synthesized. Quantum-chemical calculations of ligand molecules and metal complexes were performed. The main energy characteristics of ligand molecules were calculated: enthalpy of formation, total energy of the molecule and bond lengths, electronic population parameters of ligands. Metal polymers based on synthesized complexes were obtained by the method of radical polymerization. The composition and structure of synthesized complexes and metal polymers are established. It is shown that during polymerization the coordination environment of the central ion remains unchanged. The spectral-luminescent characteristics of the synthesized compounds were studied. The peculiarities of the influence of substituents in the diketonate fragment on the luminescent properties of metal complexes have been established. It is shown that the emission intensity of powdered samples depends on their morphology and dispersion.

Preparation and Properties of Three Plasticiser-Free Novel Di-benzo-18-Crown-6 Aldimine-Derived Lead(II) Ion-Selective Electrodes

Three novel dibenzo-18-crown-6 aldimines were successfully synthesised and structurally characterised via various spectroscopic methods (1H,13H NMR, FT-IR) and their solution phase lead binding behaviours probed via absorption spectroscopy, the results are supported by Density Functional Theoretical (DFT) modelling. These methods revealed that the asymmetric nature of these compounds is such that at equilibrium the ether cavity adopts an open configuration where the constituent oxygen atoms exhibit a highly negative electrostatic potential; hence, they spontaneously (ΔG~−58 kJ mol−1) interact/bind aqueous lead ions to form stable 2:1 metal–ligand complexes. As indicated by cyclic and square voltammetry studies, all compounds are redox active and polymerise relatively easily onto a platinum surface to form a multi-layered lead Ion-selective Membrane (ISM), the structure of which is confirmed by Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). These novel Ion-selective Electrodes (ISEs), as characterised by Differential Pulse Anodic Stripping Voltammetry (D PASV), allow selective electrochemical detection and quantification of lead at concentrations as low as 10 ppm, over a range of 15–60 ppm, with only minimal interference from mercury(II) and aluminium(III) ions at a 1:1 analyte-interferent ratio.

Schiff base functionalized 1,2,3-triazole derivative for Fe(III) ion recognition, as N,O,O-Fe-O,O,N sandwich complex: DFT analysis

The present research aims to synthesize Schiff base tethered 1,2,3-triazole derivative using Cu(I) catalyzed click reaction as a highly sensitive and selective optical chemosensor for the recognition of ferric ions. The synthesized probe was characterized using Fourier transform infrared spectroscopy (FTIR), NMR (1H and 13C), mass spectrometry, CHN analysis, and Thermal gravimetric analysis (TGA). The UV–vis spectroscopy was employed in eco-friendly EtOH:H2O (9:1 v/v) solvent media to investigate the optical properties of the developed chemosensor SBT, the association constant and limit of detection of Fe3+ was determined to be 2.6 × 104 M- 1 and 1.3 × 10-7 M establishing the designed SBT as a potent probe for analytical and practical applications. Additionally, the time-dependent study and pH sensitivity of the developed probe SBT and metal–ligand complex were also studied via UV–visible spectroscopy. Besides, FTIR spectra and TGA curve of the synthesized (SBT-metal complex) confirmed the binding of the metal–ligand complex. Furthermore, the real sample application for detection of Fe3+ in spinach (food rich in Iron) was analysed, and the SBT-based sensing system yielded a recovery rate of greater than 99.07%. The synthesized probe was also explored for its computational-based DFT studies via Gaussian 09 programs using the DFT method with (B3LYP)/-311G (d,p) basis set of hybrid density functional theory.

Characterization, DFT calculations and antimicrobial assays of some novel nanoparticles mixed ligand complexes of 5-cyano-6-phenyl-2-thiouracil in presence of 1,10-phenanthroline

Some trivalent (Cr(III), Fe(III)) and divalent (Co(II), Ni(II), Cu(II) Zn(II)) combined with synthesized 5-cyano-6-phenyl-2-thiouracil (H2CPT) in presence 1,10-phenanthroline monohydrate (Phen) to produce crystalline and semi-crystalline nanoparticles mixed ligand metal complexes. The separated nanoparticles complexes were investigated by physicochemical, spectroscopic techniques (FT-IR, UV–Vis. and 1H NMR), X-ray powder diffraction (XRD) and thermal analyses (TG-DTG-DTA). The metal complexes were ionic with 1:2 electrolytes for divalent elements and 1:3 electrolytes for trivalent elements. The FT-IR spectra indicated that H2CPT and Phen functioning as bidentate ligand binding to the metal ions via oxygen and nitrogen of cyano group of H2CPT and through two nitrogen of Phen. According to the magnetic moment and UV–vis. spectra the complexes were identified as octahedral geometries. The XRD analysis of the prepared compounds revealed that H2CPT and the complexes of Cr(III), Fe(III), Co(II) and Ni(II) display semi-crystalline peaks while, Cu(II) and Zn(II) complexes were crystalline in nature. The mechanism of the thermal degradation was identified and the kinetic parameters of the disintegration stages were assessed using Coats-Redfern (CR) and Horowitz-Metzger (HM) methods. DFT computations were used to calculate equilibrium geometric parameters and the lowest energy model structures. H2CPT, Phen and their metal complexes were examined for effectiveness towards two G(+), two G(-) bacteria and two fungi. Co(II) complex was significant, highly significant and very highly significant against all tested bacterial and fungi strains compared with H2CPT, Phen, references standard control and all other complexes.

Critical roles of metal–ligand complexes in the controlled synthesis of various metal nanoclusters

Metal nanoclusters (NCs), an important class of nanoparticles (NPs), are extremely small in size and possess quasi-molecular properties. Due to accurate stoichiometry of constituent atoms and ligands, NCs have strong structure-property relationship. The synthesis of NCs is seemingly similar to that of NPs as both are formed by colloidal phase transitions. However, they are considerably different because of metal-ligand complexes in NC synthesis. Reactive ligands can convert metal salts to complexes, actual precursors to metal NCs. During the complex formation, various metal species occur, having different reactivity and fraction depending on synthetic conditions. It can alter their degree of participation in NC synthesis and the homogeneity of final products. Herein, we investigate the effects of complex formation on the entire NC synthesis. By controlling the fraction of various Au species showing different reactivity, we find that the extent of complex formation alters reduction kinetics and the uniformity of Au NCs. We demonstrate that this concept can be universally applied to synthesize Ag, Pt, Pd, and Rh NCs.

Corrosion prevention and control using in situ phase layers formation via application of the complexing‐type inhibitors

AbstractA set of organic ligands of different natures has been investigated as complexing‐type corrosion inhibitors for the protection of low carbon steel in an acidic medium. The inhibitive mechanism implying the formation of phase protective layers on the metal surface as a result of the complexation process of added organic ligands with the metal cations is being discussed. The results of the investigation of the influence of pH and temperature conditions on the phase layers formation dynamics have been presented. A range of practical aspects of the application of organic ligands as complexing‐type inhibitors for the formation of ultrathin coatings have been discussed. The stability constant of the metal–ligand complex and its solubility have been proposed as the basis of a predictive model for analytical assessment of their potential protective efficiency.