Synthesis,biological evaluation and biodistribution of the <Superscript>99m</Superscript>Tc–Garenoxacin complex in artificially infected rats

The labeling of garenoxacin (GXN) with technetium-99m (^99mTc) using different concentrations of GXN, sodium pertechnetate (Na^99mTcO₄), stannous chloride dihydrate (SnCl₂·2H₂O) at different pH was investigated and evaluated in terms of in-vitro stability in saline, serum, binding with multi-resistant Staphylococcus aureus (MDRSA) and penicillin-resistant Streptococci (PRSC) and its biodistribution in artificially MDRSA and PRSC infected rats. ^99mTc–GXN complex with 97.45 ± 0.18% radiochemical stability was prepared by mixing 3 mg of GXN with 3 mCi of Na^99mTcO₄ in the presence of 150 μL of SnCl₂·2H₂O (1 μg/μL in 0.01 N HCl) at a pH 5.6. The radiochemical stability of the complex was evaluated in normal saline up to 240 min of reconstitution. It was observed that the complex showed maximum RCP values after 30 min of the reconstitution and remained more than 90% up to 240 min. The complex showed radiochemical stability in normal saline at 37 °C up to 16 h with a 17.80% de-tagging. The complex showed saturated in-vitro binding with living MDRSA and PRSC as compared to the insignificant binding with heat killed MDRSA and PRSC. Biodistribution behavior of the complex was assessed in artificially infected with living and heat killed MDRSA and PRSC rats. It was observed that the accumulation of the complex in the infected (live MDRSA and PRSC) tissue of the rats was almost five fold than in the inflamed and normal tissue. The high radiochemical stability in normal saline at room temperature, promising in-vitro stability in serum at 37 °C, saturated in-vitro binding with living MDRSA and PRSC, specific biodistribution behavior and high infected (target) to normal (non-target) tissue and low inflamed (non-target) to normal (non-target) tissue ratios we recommend ^99mTc–GXN complex for in-vivo localization of infection caused by MDRSA and PRSC effective stains.     

X-ray emission study of the electronic structure of binuclear niobium complexes with (S<Subscript>2</Subscript>)<Superscript>2</Superscript>–disulfide bridging ligands

The electronic structure of binuclear niobium complexes [Nb₂S₄(acac)₄] and K₄[Nb₂S₄(ox)4] is studied by X-ray emission fluorescent spectroscopy and quantum chemistry techniques. Data on the partial atomic composition of highest occupied molecular orbitals of the complexes are obtained. The energy positions of bonding and antibonding frontier molecular orbitals observed in the X-ray emission spectra of binuclear [Nb₂((S₂)^2–)₂]⁴⁺ clusters are determined by the analysis of overlap populations.     

Quantum chemical study of formation of Cu<Superscript>II</Superscript>–Y<Superscript>III</Superscript> metallamacrocyclic complexes based on glycinehydroximate ligands

The process of solution-phase formation of the Cu^II–Y^III 15-metallacrown-5 complexes bearing the glycinehydroximate ligands has been for the first time investigated by methods of quantum chemistry. The DFT modeling at the B3LYP/DGDZVP (PCM) level was carried out for mono-, bi-, and tri-nuclear copper(II) complexes and also for heteronuclear Cu^II–Y^III derivatives as the metallamacrocycle precursors. The dependence of relative stability of these complexes on the Cu^II and Y^III coordination surroundings and also on the mutual positions of ligands was found. The structural (variations of interatomic distances and valence angles), electronic (changes in the atomic charges and electron density), and thermodynamical (enthalpies and Gibbs free energies) regularities of 15-metallacrown-5 formation were revealed. The key role of Y^III cation was established for the process of formation of the polynuclear metallamacrocyclic compound (15-metallacrown-5).     

Thermodynamics of the formation of Cu<Superscript>2+</Superscript>–glycyl-glycyl-glycine complex in water–ethanol solutions at 298 K

The stability constants of monoligand complexes of copper(II) ions with glycyl-glycyl-glycine zwitterions (triglycine, HL^±) and triglycinate ions (L^?) in a water–ethanol solvent with 0.0, 0.1, 0.3, and 0.5 mole fractions of ethanol at an ionic strength of 0.1 created by sodium perchlorate and temperature Т = 298.15 K are determined by means of potentiometric titration. It is found that an increase of ethanol content improves the stability of the investigated complexes, due mainly to the resolvation of ligands.     

Thermodynamics of the complex formation between Cu<Superscript>2+</Superscript> and triglycine in water–ethanol solutions at 298 K

Thermodynamic functions Δ_r H, Δ_r G, and TΔ_r S of the complex formation between Cu²⁺ and triglycine in water–ethanol solutions are calculated on the basis of calorimetric data. It is found that raising the concentration of EtOH results in a monotonic increase in the exothermic effect of [CuHL]²⁺ complex formation due to the weakening of triglycine solvation with the mutual compensation of ion solvation contributions. The enthalpy of [CuL]⁺ complex formation has an exothermic maximum at 0.1?0.3 molar fractions of EtOH due to competition between the solvation contributions from ions and ligands.     

Preparation and bioevaluation of <Superscript>99m</Superscript>Tc–carbonyl complex of guanine

The aim of this study is to prepare radiolabeled guanine with ^99mTc(CO)₃⁺ core. For this purpose, guanine has been radiolabeled with ^99mTc(CO)₃⁺ core. Quality control study of radiolabeled guanine molecule with ^99mTc(CO)₃⁺ core was performed by thin layer radio chromatography (TLRC) and high performance liquid radio chromatography (HPLRC). The results showed that the radiolabeling yield was quite high (94 ± 3%). Beside that ^99mTc(CO)₃–Gua complex has showed good in vitro stability during the 24 h period. Radiopharmaceutical potential of this complex was evaluated in Wistar Albino Rats. It was concluded that ^99mTc(CO)₃–Gua could be used as a nucleotide radiopharmaceutical for in vivo applications.     

Synthesis,characterisation and X-ray structure of a novel porphyrin array employing Zn–O and O–H…O bonding motifs

The preparation and characterisation of the free-base and zinc metallated derivatives of 5,10,15,20-tetrakis(4-(2-(2-hydroxyethoxy)ethoxy)phenyl)porphyrin 1 is described. The X-ray crystal structure of the Zn(II) adduct 2 dimerises in the solid state via an intermolecular polyether oxygen–Zn(II) interaction (O…Zn = 2.124(4) Å). The porphyrin dimers form discrete layers defined by a distance of 5.10 Å between the porphyrin planes in adjacent layers. A bilayer sheeting arrangement of the porphyrin macrocyclic units is achieved through cooperative hydrogen bonding of the ethoxyethanol arms to form 11-membered macrocycles containing four hydrogen bonds.     

Synthesis and structural determination of a novel complex [Yb<Superscript>III</Superscript>(HEgta)] · 4H<Subscript>2</Subscript>O in comparison with [Yb<Superscript>III</Superscript>(HEgta)] · 2H<Subscript>2</Subscript>O

One novel ytterbium complex [Yb^III(HEgta)] · 4H₂O (I), where H₄Egta = ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid, has successfully been synthesized by the reaction of Yb₂O₃ with H₄Egta in an aqueous solution after refluxing for 18 h. The crystal and molecular structures were determined by the infrared spectrum and X-ray crystallography. The crystal structural analysis reveals that central Yb(III) in I is eight-coordinated in a geometry of pseudo-square antiprismatic polyhedron by two amine N atoms, two ethylene glycol O atoms, and four carboxyl O atoms from one HEgta ligand and crystallizes in the orthorhombic crystal system with P2₁2₁2₁ space group. The crystal data are as follows: a = 9.4927(8), b = 12.2627(13), c = 18.3657(17) Å, V=2137.9(4) ų, Z = 4, ρ_calcd = 1.934 mg/m³, μ = 4.448 mm^?1, F(000) = 1236, R = 0.0291, and wR = 0.0714 for 8850 observed reflections with I ≥ 2σ(I). In addition, there is a protonated coordinated carboxyl O atom (O(5)) in the [Yb^III(HEgta)] moiety.     

Thermochemical study of mixed-ligand complex formation in the system M<Superscript>2+</Superscript>-Nta<Superscript>3−</Superscript>-En (M = Ni,Cu, Zn,or Cd) in aqueous solution

Direct calorimetric data were used to calculate the heats of formation for mixed-ligand complexes MNtaEn^?, where Nta^3? is nitrilotriacetato ion, En is ethylenediamine, and M²⁺ = Ni²⁺, Zn²⁺, Cu²⁺, or Cd²⁺, in aqueous solution at 298.15 K and ionic strength I = 0.5 (NaNO₃). The complete set of thermodynamic parameters of reaction was calculated for mixed-ligand complex formation and comproportionation.     

Synthesis,characterization and spectroscopic study of riboflavin–molybdenum complex

A riboflavin–molybdenum [(RF)–Mo(V)] complex in powder form was synthesized and characterized by elemental analysis, UV–Vis, IR, NMR spectroscopy and X-ray diffraction. During the synthesis of this metal complex, another metal complex [Mo₂O₄(H₂O)₆]²⁺ was also synthesized and characterized. The results of X-ray diffraction study have revealed an orthorhombic cubic system for the RF–Mo complex. The steady state absorption and emission studies of RF and RF–Mo in hydrochloric acid (HCl) of varying pH were investigated. The steady state absorption with RF–Mo showed distinct changes in the absorption spectra of RF after complexation. The steady state emission results, consistent with prior reports showed fluorescence quenching in the aqueous solution of both RF and RF–Mo in HCl with the proton acting as a quencher. The Stern–Volmer constant observed was 108.79 and 98.68 for RF and RF–Mo, respectively. The binding constant for RF–Mo complex was found to be 1.201 × 10³ M⁻¹ at 298 K.     

The thermodynamic characteristics of complex formation between Cd<Superscript>2+</Superscript> and ethylenediamine-N,N′-disuccinic acid in aqueous solution

The enthalpies of complex formation between ethylenediamine-N,N′-disuccinic acid (H₄A) and Cd²⁺ ions were determined calorimetrically at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 (KNO₃). The thermodynamic characteristics of formation of the CdA^2? and CdHA^? complexes at fixed and zero ionic strengths were calculated. The values obtained were interpreted.     

Synthesis,X-ray, 1H-NMR and DFT analysis of the phthalimide–hydrazone probes as selective anion sensor

Two simple phthalimide–hydrazone probes with nitro groups were synthesised and characterised by NMR, FT-IR, HR-MS and single crystal X-ray crystallography. The synthesised receptors were evaluated for application in anion sensing. The receptors displayed strong, sensitive and selective colouration in the presence of cyanide ions by forming a stable complex with cyanide ion. The use of variable nitro groups helped in the elucidation of the mechanism of the complex formation. The ¹H NMR spectroscopy was used to support the mechanism of the complex formation. DFT methods were used to understand the stability of the complex with respect to the reactant. The absorbance data were also compared with the TD-DFT calculated excitation parameters. The experimental results were found to correlate well with the theoretical data.     

Synthesis of heteropolynuclear Cu<Superscript>I</Superscript> and Pd<Superscript>II</Superscript> complexes with polymeric 2,2′-biquinoline-containing ligands and investigation of their catalytic activity in the Sonogashira couplings

A method for electrosynthesis of heteropolynuclear biquinoline-containing Cu^I and Pd^II complexes using sacrificial Cu and Pd anodes was developed. The sequence of anode dissolution (first Pd and then Cu) was important for the synthesis of the complex. The opposite sequence of dissolution resulted in oxidation of the initially formed Cu^I ions to Cu^II. The obtained Cu^I and Pd^II complexes with polymer ligands had high catalytic activity in the reaction of aryl halides with phenylacetylene giving rise to a C(sp²)-C(sp) bond. The yield of arylphenylacetylene in the presence of 0.1 mol.% of Pd catalyst in relation to the starting halide was 50–90% depending on the nature of the aryl halide.     

Quantum-chemical DFT study of acid properties of thiols RSH and ligand power of their anions RS<Superscript>−</Superscript>

The DFT calculations of electronic and geometry structure, dissociation energies of S-H and S-C bonds, and acid dissociation constants (pK _a) for ten RSH thiols were fulfilled. Calibration corrections to the calculated pK _a^DFT values, which allowed obtaining a good correspondence with experimental data were introduced. Donor power of thiolate anions RS- was estimated for the prediction of stability of their compounds with ions of d-elements.     

Synthesis and structures of Cu<Superscript>I,II</Superscript> complexes with a 2,2´-bipyridine derivative bearing a (+)-3-carene moiety

The complex salt {[CuL₂][Cu₄I₆]?MeCN}_n (1) and the compound [Cu₄L₃I₄]?3 MeCN (2) (L is a chiral ligand bearing a natural monoterpene (+)-3-carene moiety) were synthesized. The crystal structures of compounds 1 and 2 were determined by X-ray diffraction. The structure of compound 1 consists of complex cations [CuL₂]²⁺ (N₃O₂ polyhedron is a trigonal bipyramid) and Cu^I coordination polymers (CuI₄ polyhedron is a tetrahedron) as anions. The experimental magnetic moment μ_eff at 300 K is 1.90 μ_B, which is consistent with the X-ray diffraction data and the assumption that compound 1 is mixed-valence. The structure of compound 2 comprises a tetranuclear Cu^I complex, in which three Cu atoms are coordinated by two N atoms of the ligand L and two I atoms, and the fourth Cu atom is coordinated by four I atoms (coordination polyhedra are distorted tetrahedra). Compounds L and 2 were found to influence the viability of human laryngeal carcinoma cells (Hep2). The IC₅₀ value for complex 2 (13.0±1.7 μM) is substantially smaller than IC₅₀ for compound L (30.5±0.5 μM).     

Experimental and theoretical characterization of Fe<Subscript>2</Subscript>Cr trinuclear-oxo-centered complex with a CF<Subscript>2</Subscript>ClCOO<Superscript>–</Superscript> bridge

In this work, an atrinuclear-oxo-centered complex of the CrFe₂ type with the CF₂ClCOO^– bridging ligand is newly synthesized. The complex is characterized by experimental and theoretical methods. The optimized geometry and theoretical vibrational frequencies are computed using the density functional theory (DFT) method. Also, the AIM analysis was applied to study changes in topological parameters such as the electron density at critical points of all the bonds of the complex. In the optimized geometry of the complex, three metal ions form a trigonal-planar structure with a μ₃-O atom in its center. Each of M³⁺ metal ions has an octahedral coordination environment of oxygen atoms. The DFT results are in agreement with the experimental ones, confirming the validity of the optimized geometry for the complex.     

Synthesis of bifunctional core–shell particles with a porous zeolite core and a responsive polymeric shell

The aim of our work is the synthesis and characterization of colloidal core–shell particles with a zeolite core and an environmentally responsive shell. We have synthesized colloidal ZSM-5 zeolite and modified the surface with 3-(trimethoxysilyl)propyl methacrylate in order to introduce double bonds at the surface. The cross-linked polymeric shell was prepared by precipitation polymerization using the functionalized zeolite particles as seeds. We employed thermoresponsive poly(N-isopropylacrylamide) and pH-responsive poly(vinylpyridine) as the polymeric shell, respectively. The temperature- and pH-depending swelling and deswelling of the core–shell particles were characterized with dynamic light scattering techniques. Transmission electron microscopy pictures show the morphology of the synthesized particles. It is proposed that these types of bifunctional core–shell particles could be of use for controlled uptake and release applications and separation of molecules.     

A study on seasonal variability of <Superscript>222</Superscript>Rn–<Superscript>220</Superscript>Rn parameters in dwellings around a thermal power plant,India

A novel ethylene diamine tetraacetic acid derivative of 4-nitroimidazole (EDTA-4-EtNHNM) was successfully synthesized as a carrier molecule and it was radiolabeled with ^99mTc in high yield to obtain ^99mTc-EDTA-4-EtNHNM, which was hydrophilic and had good in vitro stability. The tumor cell experiment and the biodistribution study in mice bearing S180 tumor showed that this complex exhibited a hypoxic selectivity and had high accumulation in tumor tissue with major clearance through urinary tract. High tumor uptake and tumor/muscle ratio of the complex suggests promise towards further evaluation.     

Pulse radiolysis study of the oxidation of the I<Superscript>−</Superscript> ions with the radical anions Br<Subscript>2</Subscript><Superscript>·−</Superscript> in an aqueous solution: formation and properties of the radical anion BrI<Superscript>·−</Superscript>

The radiation chemical redox transformations in solutions of bromides in the presence of minor additives of iodides were studied by pulse radiolysis. The change in the concentrations of the Br⁻ and I⁻ ions changes the ratio of the formed short-lived radical anions Br₂ ^·−, BrI^·−, and I₂ ^·−. The spectrum of the mixed radical anion BrI^·− contains a broad optical band at 370 nm with ɛ₃₇₀ = 9650 L mol⁻¹ cm⁻¹. The reduction potential of the BrI^·−/Br⁻, I⁻ pair is 1.25 V. The rate constants for the forward and backward reactions Br₂ ^·− + I⁻ ⇌ BrI^·− + Br⁻ are k _f = 4.3·10⁹ and k _r = 1.0·10⁵ L mol⁻¹ s⁻¹, respectively; for the reactions BrI^·− ⇌ Br⁻ + I^·, k _f = 5.7·10⁸ s⁻¹ and k _r = 1.0·10¹⁰ L mol⁻¹ s⁻¹. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1787–1792, September, 2008.