Synthesis, crystal structure and photophysical properties of a series of new neutral iridium(III) complexes with 2-phenylpyridine

A series of new neutral iridium(III) complexes containing strong-field ancillary ligands, [Ir(ppy)₂(PPh₃)L] (ppy = 2-phenylpyridine, PPh₃ = triphenylphosphine, L = NCS⁻, 1; , 2; NCO⁻, 3), have been synthesized and fully characterized by ¹H NMR, IR, ESI mass spectral and elemental analysis. The crystal structure of 1 has been determined by X-ray analysis. The photoluminescence (PL) spectra of 1–3 show emission maxima at 477, 489 and 485 nm, respectively, corresponding to blue light-emitting of 1 and blue-green light-emitting of 2 and 3. PL quantum yields (PLQYs) of 1–3 are 0.39, 0.13 and 0.43, respectively.     

The synthesis, characterization, thermal and optical properties of copper, nickel, and vanadyl complexes derived from azo dyes

Two, novel, tetradentate Schiff-base ligands, namely bis-5-phenylazosalicylaldehyde diethylenetriimine and bis-5-[(4-methoxyphenyl)azo]salicylaldehyde diethylenetriimine, as well as their Cu²⁺, Ni²⁺, and VO²⁺ complexes, were synthesized and characterized using elemental analysis, infrared and also UV–Visible spectroscopy, ¹HNMR and mass spectra. The thermal stability of the free ligands and the related metal complexes, as determined using differential scanning calorimetry and thermal gravimetric analysis, were found to be thermally stable upto 240–275 °C depending on the type of ligand and the central metal atom. The λ_max of the ligands and their transition metal complexes in the region 300–800 nm are discussed. The novel metal complexes offer potential for application as recording media owing to both their absorption spectra in the blue-violet light region and high thermal stability.     

Electrochemical oxidation of aliphatic hydrocarbons promoted by inorganic radicals. I. OH radicals

The OH initiated oxidation of aliphatic hydrocarbons by the simultaneous electrochemical reduction of O₂ and of Fe(III) at controlled potential was investigated in the liquid phase over a Fe(III) concentration range 0.5–5 mM. OH radicals were generated by the reaction: Fe(II)+H₂O₂Fe(III)+^.OH+OH^– The compounds studied were the linear alkane hydrocarbons from C₅ to C₁₀ and 3-methyl pentane. The results showed that the ketones are the only reaction products and that the yields decrease with increasing number of carbonium atoms of the hydrocarbon. Decreasing yields were also observed with increasing Fe(III) concentration.     

Photodegradation of tetrahalobisphenol-A (X = Cl, Br) flame retardants and delineation of factors affecting the process

The photoassisted degradation (HPLC-UV absorption), dehalogenation (HPLC-IC) and mineralization (TOC decay) of the flame retardants tetrabromobisphenol-A (TBBPA) and tetrachlorobisphenol-A (TCBPA) were examined in UV-irradiated alkaline aqueous TiO₂ dispersions (pH 12), and for comparison the parent bisphenol-A (BPA, an endocrine disruptor) in pH 4–12 aqueous media to assess which factor impact most on the photodegradative process. Complete degradation (2.7–2.8 × 10⁻² min⁻¹) and dehalogenation (1.8 × 10⁻² min⁻¹) of TBBPA and TCBPA occurred within 2 h of UV irradiation, whereas only 45–60% mineralization (2.3–2.7 × 10⁻³ min⁻¹) was complete within 5 h for the flame retardants at pH 12 and ca. 80% for the parent BPA. Factors examined in the pH range 4–12 that impact the degradation of BPA were the point of zero charge of TiO₂ particles (pH_pzc; electrophoretic method), particle or aggregate sizes of TiO₂ (light scattering), and the relative number of OH radicals (as DMPO–OH adducts; ESR spectroscopy) produced in the UV-irradiated dispersion. Dynamics of BPA degradation (2.0–2.4 × 10⁻² min⁻¹) were pH-independent and independent of particle/aggregate size, but did correlate with the number of OH radicals, at least at pHs 4 to 8–9, after which the rates decreased somewhat at pH > 9 with decreasing adsorption owing to Coulombic repulsive forces between the very negative TiO₂ surface and the anionic forms of BPA (pK_as ca. 9.6–11.3), even though the number of OH radicals continued to increase at the higher pHs.     

8-Hydroxyquinoline-Amino Acid Hybrids and Their Half-Sandwich Rh and Ru Complexes: Synthesis,Anticancer Activities,Solution Chemistry and Interaction with Biomolecules

Solution chemical properties of two novel 8-hydroxyquinoline-D-proline and homo-proline hybrids were investigated along with their complex formation with [Rh(η⁵-C₅Me₅)(H₂O)₃]²⁺ and [Ru(η⁶-p-cymene)(H₂O)₃]²⁺ ions by pH-potentiometry, UV-visible spectrophotometry and ¹H NMR spectroscopy. Due to the zwitterionic structure of the ligands, they possess excellent water solubility as well as their complexes. The complexes exhibit high solution stability in a wide pH range; no significant dissociation occurs at physiological pH. The hybrids and their Rh(η⁵-C₅Me₅) complexes displayed enhanced cytotoxicity in human colon adenocarcinoma cell lines and exhibited multidrug resistance selectivity. In addition, the Rh(η⁵-C₅Me₅) complexes showed increased selectivity to the chemosensitive cancer cells over the normal cells; meanwhile, the Ru(η⁶-p-cymene) complexes were inactive, most likely due to arene loss. Interaction of the complexes with human serum albumin (HSA) and calf-thymus DNA (ct-DNA) was investigated by capillary electrophoresis, fluorometry and circular dichroism. The complexes are able to bind strongly to HSA and ct-DNA, but DNA cleavage was not observed. Changing the five-membered proline ring to the six-membered homoproline resulted in increased lipophilicity and cytotoxicity of the Rh(η⁵-C₅Me₅) complexes while changing the configuration (L vs. D) rather has an impact on HSA or ct-DNA binding.     

Preferred exocyclic-amino coordination of W(CO)5 on 2-aminopyrimidine and 4-aminopyrimidine vs. heterocyclic N-1 coordination for 2-aminopyridine

2-Aminopyrimidine (2-ampym) and 4-aminopyrimidine (4-ampym) coordinate to W(CO)₅ predominantly via the exocyclic amino group (>91% in 10 min photolysis) rather than to the endocyclic N-1 position as found for 2-aminopyridine (2-ampy). Photolysis of W(CO)₆ in acetone in the presence of these ligands forms amino-bound [W(CO)₅(2-ampym)] and [W(CO)₅(4-ampym)] complexes. Secondary photolysis generates 18% (1.0 h photolysis) [W(CO)₄(2-ampym)] or [W(CO)₄(4-ampym)], chelated via the exocyclic amine and the adjacent endocyclic position (N-1 and N-3, respectively). Only ca. 10% of the more unhindered N-1-bound W(CO)₅(4-ampym) was detected compared to virtually complete coordination via the exocyclic amino group for [W(CO)₅(2-ampym)]. M 94 calculations show that the W(CO)₅ coordination to the exocyclic donor is favored by 98.8 and 95.6 kcal/mol over the adjacent endocyclic position in the 2-ampym and 4-ampym complexes, respectively. Calculated W–N bond lengths by the M 94 methods gave exo-amine W–N bond distances of 2.24 and 2.26 Å and theoretical adjacent endocyclic W–N bond distances of 2.37 and 2.35 Å (isomers not observed from photolysis) for the 2-ampym and 4-ampym complexes, respectively. A W–(N-1) bond of 2.28 Å for this isomer of [W(CO)₅(4-ampym)] was calculated. All W–N bonds are near the 2.18–2.33 Å range (mean of 2.27±0.06) for [W(CO)₅L] (L=pyridine, piperidine, glycine, 1-(2-py)-1,2,4-triazole, [W(CO)₅CN]⁻, 5-MeU⁻).     

Ruthenium(III) Complexes of Heterocyclic Tridentate (ONN) Schiff Base: Synthesis,Characterization and its Biological Properties as an Antiradical and Antiproliferative Agent

The current work reports the synthesis, spectroscopic studies, antiradical and antiproliferative properties of four ruthenium(III) complexes of heterocyclic tridentate Schiff base bearing a simple 2′,4′-dihydroxyacetophenone functionality and ethylenediamine as the bridging ligand with RCHO moiety. The reaction of the tridentate ligands with RuCl₃·3H₂O lead to the formation of neutral complexes of the type [Ru(L)Cl₂(H₂O)] (where L = tridentate NNO ligands). The compounds were characterized by elemental analysis, UV-vis, conductivity measurements, FTIR spectroscopy and confirmed the proposed octahedral geometry around the Ru ion. The Ru(III) compounds showed antiradical potentials against 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, with DPPH scavenging capability in the order: [(PAEBOD)RuCl₂] > [(BZEBOD)RuCl₂] > [(MOABOD)RuCl₂] > [Vit. C] > [rutin] > [(METBOD)RuCl₂], and ABTS radical in the order: [(PAEBOD)RuCl₂] < [(MOABOD)RuCl₂] < [(BZEBOD)RuCl₂] < [(METBOD)RuCl₂]. Furthermore, in vitro anti-proliferative activity was investigated against three human cancer cell lines: renal cancer cell (TK-10), melanoma cancer cell (UACC-62) and breast cancer cell (MCF-7) by SRB assay.     

Kinetics of Sn electrodeposition from Sn(II)–citrate solutions

The influence of solution chemistry on the electrodeposition of Sn from Sn(II)–citrate solutions is studied. The distribution of various Sn(II)–citrate complexes and citrate ligands is calculated and the results presented as speciation diagrams. At a SnCl₂·H₂O concentration of 0.22 mol/L and citrate concentration from 0.30 mol/L to 0.66 mol/L, SnH₃L⁺ (where L represents the tetravalent citrate ligand) is the main species at pH below about 1.2 and SnHL⁻ is the main species at pH above about 4. Polarization studies and reduction potential calculations show that the Sn(II)–citrate complexes have similar reduction potentials at a given solution composition and pH. However, the Sn(II)–citrate complexes become more difficult to reduce with higher total citrate concentration and higher solution pH. Nevertheless, SnHL⁻ which forms at higher pH is a favored Sn(II)–citrate complex for Sn electrodeposition due to better plated film morphology, likely as a result of its slower electroplating kinetics. Precipitates are formed from the Sn(II)–citrate solutions after adding hydrochloric acid (to lower the pH). Compositional and structural analyses indicate that the precipitates may have the formula Sn₂L.     

Neodymium(III) cathodic processes in molten fluorides

The electrochemical behaviour of the Nd(III)/Nd(0) system has been investigated in several molten media and more particularly in LiF-CaF₂. A preliminary study based both on thermodynamic and experimental data showed that it is not possible to observe the Nd(III)/Nd(0) system in LiF-KF and LiF-NaF melts; because the K⁺ and Na⁺ cation reduction waves hide the Nd³⁺ reduction wave. Then, the Nd(III)/Nd(0) system has been investigated at 810 °C using solutions of NdF₃ in fluoride solvents without K⁺ and Na⁺ ions, such as LiF-CaF₂, by cyclic voltammetry, chronopotentiometry and square wave voltammetry. Experimental results show that neodymium trifluoride is reduced in Nd(0) in a one-step process exchanging three electrons (Nd(III) + 3e⁻ → Nd(0)). The electrode process is shown to be diffusion controlled. Nd(III) diffusion coefficient is in the range of 1.1-1.3 × 10⁻⁵ cm² s⁻¹ at 810 °C.     

The Effect of the Synthetic Conditions on the Deposition and Distribution of Copper Complexes on Polymer Supports

The influence of conditions (e.g., ratios of components, temperature etc.) on the reaction of Cu(OCOCH₃)₂·2H₂O with polyethylene grafted-polyacrylic on the amount of the metal and the composition of the immobilized Cu(II) complexes was studied. The concentration dependence obeys the Langmuir law. Analysis of the data leads to an evaluation of the stability constant for the Cu(II) complexes (K=300 l/mole at 333 K). The constant corresponds to a Cu(II) fixation value, k=0.35 mole/l (22.22 mg Cu(II)/g). The multistage fixation mechanism for Cu(II) complex formation was demonstrated by the marked atom technique. Cu(II) is fixed by one carboxylate group (to 16 mol% of the supported Cu(II), K ₁=16×10^–2 mole/g) and by two carboxylate groups (K ₂=2.54×10^–3 mole/g) of the grafted ligands. The PE-gr-PAA–Cu(II) system mimics the situation-insoluble support-soluble functional polymer covering and realizes the advantages of both the soluble and the three-dimensional crosslinked polymer. Steady-state magnetic susceptibility measurements and ESR spectroscopy were used to study the distribution of cupric ion attached to a polyethylene-grafted poly(acrylic acid) support. The existence of three types of cupric ion complexes was demonstrated: (1) isolated complexes, (2) complexes bonded by dipole–dipole interactions, and (3) clusters with strong exchange interactions. The mean distances between the isolated ions (¯r22–15 Å) and between the dipole–bound complexes (¯r _agreg7 Å) were estimated. The results obtained were compared to the data for other immobilized catalysts. Preliminary results on the fixation of bimetallic Cu(II) and Pd(II) complexes to the polymers as well as on their distributions were obtained.     

Influence of Adsorbed Water and Oxygen on the Photoluminescence and EPR of Por-TiO2 (Anatase)

The influence of adsorbed water, oxygen, air and vacuum on the photoluminescence (PL) and electron paramagnetic resonance (EPR) has been investigated in situ and quasi in situ for por-TiO₂ (anatase). The broad PL signal in the visible spectral region decreases with increasing partial pressure of oxygen and vanishes at pressures higher than 1 mbar. Adsorption of water leads (i) to a fast quenching and (ii) to a subsequent increase of the PL signal. The concentration of the O₂ ^–, O^–, O₃ ^– anion-radicals depends sensitively on the surface conditioning and on the illumination of the por-TiO₂. Ti₃+ centers could be observed only in vacuum treated samples. The concentrations of the Ti₃+ and oxygen anion radicals are in the range of 10¹⁵ and 10¹⁷ cm^–3, respectively.     

Studies on interaction of Cr(III) polypyridyl complexes with DNA

Two chromium(III) complexes containing derivatives of 1,10-phenanthroline were synthesized and characterized using different spectroscopic methods. The interaction of the synthesized complexes with DNA was performed. From the absorption titration data, the binding constant for the complexes [Cr(imiphen)₂Cl₂]⁺ (1) and [Cr(furphen)₂Cl₂]⁺ (2) with DNA were found to be 5.69 ± 0.3 × 10⁴ M^− 1 for 1 and 3.7 ± 0.2 × 10⁴ M^− 1 for 2, respectively. The viscosity studies show that both the complexes bind to DNA in a partial intercalative mode. The results of competitive binding assay reveal that both complexes displace EB from DNA marginally. Gel electrophoresis data show that both the complexes 1 and 2 requires co-reagent to induce DNA cleavage but complex 2 exhibit better nuclease activity compared to complex 1. The results from this study describe the role of ligand structure in the binding and cleavage of DNA as furan based ligand exhibit better cleaving ability compared to imidazole moiety.     

Influence of the A-site cation in AMnO3+x and AFeO3+x (A = La,Pr, Nd and Gd) perovskite-type oxides on the catalytic activity for methane combustion

The effect of rare-earth ions (La, Pr, Nd and Gd) in AMnO_3+x and AFeO_3+x perovskites on the thermal behavior and on the catalytic activity for the deep oxidation of methane has been studied. AMnO_3+x perovskites showed after preparation an oxidative non-stoichiometry. Oxygen desorption analysis revealed for the four manganites different desorption steps occurring between 930 and 1370 K. Stoichiometry was reached after the first desorption step. Heating the samples at temperatures above 1300 K resulted in phase segregation to the simple oxides. AFeO_3+x perovskites were more stable towards thermal decomposition than the Mn-perovskites, showing no oxygen evolution up to 1400 K. The reducibility of these perovskites in hydrogen correlated inversely with the relative effective ionic radii of the trivalent rare-earth cations. Comparative catalytic studies were carried out in a fixed-bed microreactor at atmospheric pressure in the temperature range 600–1200 K. The activities at 770 K, expressed as reaction rates referred to the BET surface area, varied between 1.4 × 10^–7 and 2.9 × 10^–7 mol s^–1 m^–7 for the AMnO_3+x, and between 1.1 × 10^–7 and 1.6 × 10^–7 mols^–1m^–2for the AFeO_3+x perovskites.     

Carbon-free dry reforming of methane to syngas over NdCoO3 perovskite-type mixed metal oxide catalyst

CoNdO_x (Co/Nd = 1) is a highly promising catalyst for the carbon-free CO₂ reforming of methane. Influence of the Co/Nd ratio on the catalyst performance in the CO₂ reforming and also on the crystalline phases and reduction by temperature programmed reduction (TPR) of the CoNdO_x catalyst has also been investigated. The CoNdO_x (CoNd = 1.0) catalyst consisted of mainly NdCoO₃ perovskite-type mixed metal oxide and it showed not only a high resistance to carbon formation at different process conditions (viz. temperature = 750–900 °C and gas hourly space velocity (GHSV) = 10000–50000 cm³ g^–1 h^–1) but also high activity and selectivity in the CO₂ reforming process. The high resistance to carbon formation for this catalyst is attributed mostly to strong metal (Co°)–support (Nd₂O₃) interactions.     

Silver Nanostructures: Limited Sensitivity of Detection,Toxicity and Anti-Inflammation Effects

Nanosilver with sizes 1–100 nm at least in one dimension is widely used due to physicochemical, anti-inflammatory, anti-angiogenesis, antiplatelet, antifungal, anticancer, antibacterial, and antiviral properties. Three modes of the nanosilver action were suggested: “Trojan horse”, inductive, and quantum mechanical. The Ag⁺ cations have an affinity to thiol, amino, phosphate, and carboxyl groups. Multiple mechanisms of action towards proteins, DNA, and membranes reduce a risk of pathogen resistance but inevitably cause toxicity for cells and organisms. Silver nanoparticles (AgNP) are known to generate two reactive oxygen species (ROS)-superoxide (•O₂⁻) and hydroxyl (•OH) radicals, which inhibit the cellular antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and cause mechanical damage of membranes. Ag⁺ release and replacement by electrolyte ions with potential formation of insoluble AgCl result in NP instability and interactions of heavy metals with nucleic acids and proteins. Protein shells protect AgNP core from oxidation, dissolution, and aggregation, and provide specific interactions with ligands. These nanoconjugates can be used for immunoassays and diagnostics, but the sensitivity is limited at 10 pg and specificity is restricted by binding with protective proteins (immunoglobulins, fibrinogen, albumin, and others). Thus, broad implementation of Ag nanostructures revealed limitations such as instability; binding with major blood proteins; damage of proteins, nucleic acids, and membranes; and immunosuppression of the majority of cytokines.     

Study of the mechanism of additives on copper dissolution in monoethanolamine-complexed cupric ion solution

The dissolution of copper in monoethanolamine (MEA)-complexed cupric ion solution containing different additives was studied. Bridging ligands, such as F^–, Cl^–, Br^–, I^–, SCN^–, and oxidizers, including S₂O₈ ^2–, Cr₂O₇ ^2–, MnO₄ ^– were added to this nonammoniacal etching solution to increase the copper dissolution rate. Potentiodynamic methods were employed to elucidate the dissolution mechanism and the corrosion potential (E _corr) was found to shift from 10 to 90 mV as opposed to that of the original solution (0.045 M cupric sulfate and 0.225 M MEA) for bridging ligands. In contrast, some conventional oxidizers were also added in the etchant and the E _corr did not shift obviously. Therefore, we proposed that copper dissolution proceeds through an inner-sphere pathway in solution containing bridging ligands. The electron is transferred from the copper surface into the cupric species through the ligands, which greatly influences the copper dissolution rate. The order of effectiveness of these ligands is SCN^– > I^– > Br^– > Cl^– > F^–, which is related to their polarizability.     

Synthesis, crystal structure and photoelectric property of two novel coordinated complexes constructed by 4,4′-bipyridine and sebacic acid

Two two-dimensional (2D) new complexes: [M(bpy)(C₁₀H₁₆O₄)H₂O] [M = Ni (1), Co (2); bpy = 4,4-bipyridine, C₁₀H₁₈O₄ = sebacic acid] were synthesized by the hydrothermal reaction at 180 °C and characterized by elemental analysis, infrared spectra, and thermogravimetric spectra, single-crystal X-ray diffraction and surface photovoltage spectrum (SPS). The single-crystal X-ray diffraction showed that both complexes are isomorphous, crystallized in monoclinic system, and space group P2₁/c. In addition, The results of SPS for complexes (1) and (2) indicate that these two complexes exhibit positive surface photovoltage response in the range of 300–800 nm, which can be assigned to LMCT and d → d^* electronic transition. The SPS spectra of the two complexes are consistent with their UV–Vis spectra.     

Design of High-Relaxivity Polyelectrolyte Nanocapsules Based on Citrate Complexes of Gadolinium(III) of Unusual Composition

Through nuclear magnetic relaxation and pH-metry, the details of the complexation of gadolinium(III) ions with citric acid (H₄L) in water and aqueous solutions of cationic polyelectrolytes are established. It is shown that the presence of poly(ethylene imine) (PEI) in solution affects magnetic relaxation behavior of gadolinium(III) complexes with citric acid (Cit) to a greater extent than polydiallyldimethylammonium chloride (PDDC). A large increase in relaxivity (up to 50 mM⁻¹s⁻¹) in the broad pH range (4–8) is revealed for the gadolinium(III)–citric acid–PEI system, which is particularly strong in the case of PEI with the molecular weight of 25 and 60 kDa. In weakly acidic medium (pH 3–7), the presence of PEI results in the formation of two tris-ligand associates [Gd(H₂L)₃]³⁻ and [Gd(H₂L)₂(HL)]⁴⁻, which do not exist in aqueous medium. In weakly alkaline medium (pH 7–10), formation of ternary complexes Gd(III)–Cit–PEI with the Gd(III)–to–Cit ratio of 1:2 is evidenced. Using transmission electron microscopy (TEM) and dynamic light scattering techniques (DLS), the formation of the particles with the size of 50–100 nm possessing narrow molecular-mass distribution (PDI 0.08) is determined in the solution containing associate of PEI with tris-ligand complex [Gd(H₂L)₂(HL)]⁴⁻.     

Design and synthesis of near-IR luminescent mesoporous materials covalently linked with tris(8-hydroxyquinolinate)lanthanide(III) complexes

By using the bifunctional ligand, 8-hydroxyquinoline-functionalized organosilane (Q-Si), the new mesoporous material Q–MCM-41 covalently bonded with 8-hydroxyquinoline was synthesized. Through the ligand exchange reaction, the new near-infrared (NIR) luminescent mesoporous LnQ₃–MCM-41 (Ln = Er, Nd, Yb) materials were prepared by linking the lanthanide quinolinate complexes to the ordered mesoporous Q–MCM-41 material. The LnQ₃–MCM-41 materials were characterized by powder X-ray diffraction and N₂ adsorption/desorption, and they all show the characteristic mesoporous structure of MCM-41 with highly uniform pore size distributions. Fluorescence spectra of these LnQ₃–MCM-41 materials were recorded and the corresponding luminescence decay analyses were measured. After ligand-mediated excitation, all the emission spectra of the LnQ₃–MCM-41 materials show the characteristic NIR-luminescence of the corresponding lanthanide ions via the intramolecular energy transfer from the ligands to the lanthanide ions. The good luminescent performances enable these NIR-luminescent mesoporous materials to have potential applications in optical amplification (operating at 1.3 or 1.5 μm) and laser systems, etc.     

Immobilizing DNA on clay mineral modified carbon paste electrodes

Al-kaolinite, Al-montmorillonite, and Al₁₃-montmorillonite have been prepared and their electrokinetic mobility were measured to be – 2.06 × 10^- 8, -0.62 × 10^- 8 and +2.98 × 10^- 8 m²V^{- 1}s^{- 1} respectively. DNA immobilized on the clay mineral modified carbon paste electrode via the positive charges of the clay mineral. The immobilizing efficiencies of DNA were monitored with the DNA markers methylene blue (MB) and ethidium bromide (EB) and they were of the following sequence: Al-kaolinite < Al-montmorillonite < Al₁₃-montmorillonite. The immobilization did not affect the binding event between DNA and MB or EB. The obtained DNA-sensors can be used to study the interaction between low molecular weight compounds and DNA as well as the different binding strength of low molecular weight compounds with ssDNA and dsDNA.