Synthesis of a tetrapyrazinoporphyrazine-based fluorescent sensor for detection of Cu<Superscript>2+</Superscript> ion

In this study, a novel tetrapyrazinoporphyrazine-based fluorescent sensor for Cu²⁺ ion was synthesized and fully characterized by ¹H NMR, MALDI-TOF MS, and elemental analysis. A tetrapyrazinoporphyrazine substituent was used as the reporting group and a 2,2′-dipyridylamine moiety was employed as the recognition group. The effects of various metal ions on the absorption and emission spectra of the designed molecule were investigated, demonstrating that this compound shows selectivity and sensitivity toward the Cu²⁺ ion. Upon addition of Cu²⁺ ion, a fluorescent intensity of the tetrapyrazinoporphyrazine-based sensor decreased gradually at 655 nm. To confirm a selective binding ability of 2,2′-dipyridylamine moiety toward Cu²⁺ ion, a comparative study was performed using tetrapyrazinoporphyrazine derivative with bromine instead of 2,2′-dipyridylamine moiety. Furthermore, association constant and detection limit value of the synthesized compound toward Cu²⁺ ion were derived from a repetitive titration experiment. Also, a reversibility of the prepared sensor was confirmed through additional test using compound and ethylenediaminetetraacetic acid.     

Liquid extraction of La<Superscript>III</Superscript>, Gd<Superscript>III</Superscript>, and Yb<Superscript>III</Superscript> ions by phosphorylated calix[4]resorcinarene derivatives

New phosphorylated calix[4]resorcinarene and cavitands were synthesized. Their extraction ability toward La^III, Gd^III, and Yb^III ions was studied. The cavitands are more efficient extracting agents than octasubstituted calix[4]resorcinarenes. The nature of substituents at the nitrogen atom at the upper rim and hydrophobic substituents at the lower rim exerts a substantial effect on the solubility of the extracted complex in chloroform. Coordination of two lanthanide ions with an extragent molecule results in their efficient but non-selective extraction. The literature and our spectral (³¹P NMR) data suggested that the ligand in the extracted complex has most probably a “kite” conformation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 303–308, February, 2007.     

Time-dependent inhibition of Na<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase induced by single and simultaneous exposure to lead and cadmium

Time-dependent interactions of Na⁺/K⁺-ATPase, isolated from rat brain synaptic plasma membranes (SPMs), with Cd²⁺ and Pb²⁺ ions in a single exposure and in a mixture were investigated in vitro. The interference of the enzyme with these metal ions was studied as a function of different protein concentrations and exposure time. The aim of the work was to investigate the possibility of selective recognition of Cd²⁺ and Pb²⁺ ions in a mixture, on the basis of the different rates of their protein-ligand interactions. Decreasing protein concentration increased the sensitivity of Na⁺/K⁺-ATPase toward both metals. The selectivity in protein-ligand interactions was obtained by variation of preincubation time (incubation before starting the enzymatic reaction). The text was submitted by the authors in English.     

Global fallout levels of <Superscript>99</Superscript>Tc and activity ratio of <Superscript>99</Superscript>Tc/<Superscript>137</Superscript>Cs in the Pacific Ocean

Summary Global fallout levels of ⁹⁹Tc and ¹³⁷Cs of surface seawater in the Pacific Ocean were measured. The ⁹⁹Tc concentrations ranged from 0.62 to 3.33 mBq^. m^-3and 5 of 6 samples showed less than 1 mBq^. m^-3except one sample taken in the Great Barrier Reef, Australia. The ¹³⁷Cs concentrations ranged from 2.13 to 3.14 Bq^. m^-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in the South Pacific. The ⁹⁹Tc/¹³⁷Cs activity ratios ranged from 2.5^. 10^-4to 2.9^. 10^-4, which is very close to that calculated theoretically from the fission yield.     

Quinolinephosphomolybdate as ion exchanger: synthesis,characterization, and application in separation of <Superscript>90</Superscript>Y from <Superscript>90</Superscript>Sr

An inorganic ion exchanger, quinolinephosphomolybdate has been synthesized and characterized by elemental analysis, infrared (IR) and X-ray diffraction (XRD) spectroscopy. This compound is highly stable toward thermal, chemical and radiation dose. This has been employed in the separation of carrier-free ⁹⁰Y from its parent ⁹⁰Sr from an equilibrium mixture. The absorbed daughter was recovered by using 0.0284 mol L⁻¹ ascorbic acid solutions at pH 5.0 as eluting agent.     

Interaction energies of histidine with cations (H<Superscript>+</Superscript>, Li<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>)

The imidazol side group of histidine has two nitrogen atoms capable of being protonated or participating in metal binding. Hence, histidine can take on various metal-bound and protonated forms in proteins. Because of its variable structural state, histidine often functions as a key amino acid residue in enzymatic reactions. Ab initio (HF and MP2) calculations were done in modeling the cation (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) interaction with side chain of histidine. The region selectivity of metal ion complexation is controlled by the affinity of the side of attack. In the imidazol unite of histidine the ring nitrogen has much higher metal ion (as well as proton) affinity. The complexation energies with the model systems decrease in the following order: Mg²⁺ > Ca²⁺ > Li⁺ > Na⁺ > K⁺. The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction energies.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Spectroscopic and thermal investigations of complexes of Cr<Superscript>III</Superscript>, Mn<Superscript>II</Superscript>, Zn<Superscript>II</Superscript> &; Cd<Superscript>II</Superscript> - carboxamide

Complexes of Cr^III, Mn^II, Zn^II & Cd^II with the polydentate carboxamide ligandN′, N′′-bis(3-carboxy-1-oxoprop-2-enyl) 2-Amino-N-arylbenzamidine (H₂L) have been synthesized and characterized by elemental analyses, spectroscopic studies (Vibrational, electronic, ESR and ¹H-NMR), magnetic susceptibility measurements, thermal studies and powder diffraction studies. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicates octahedral or tetrahedral geometry around the metal ions, has been supported by magnetic susceptibility measurements. The results of electron spin resonance & ¹H-NMR spectra have supported the results of other spectral techniques. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. Powder diffraction determines the cell parameters of the complexes.     

Heterospin mixed-ligand heterotrinuclear Co<Superscript>II</Superscript>, Gd<Superscript>III</Superscript>, Co<Superscript>II</Superscript> complex with nitronyl nitroxide

A method was developed for the synthesis of mixed-metal heterospin compounds with the direct coordination of the nitroxide fragment based on the replacement of acetonitrile molecules in the heterotrinuclear complex [Co₂Gd(NO₃)Piv₆(CH₃CN)₂] with nitroxide molecules. The molecular and crystal structure of the heterospin mixed-ligand heterotrinuclear Co^II, Gd^III, Co^II complex [Co₂Gd(NO₃)Piv₆(NIT-Me)₂], where NIT-Me is stable nitronyl nitroxide, was established. The magnetic properties of this complex were investigated in the temperature range of 2–300 K. The coordination of nitroxide groups to Co^II ions is responsible for strong exchange interactions between the unpaired electrons in the exchange clusters {>-·O-Co^II}, resulting in the virtually complete spin coupling between each coordinated >N-·O group and one of the unpaired electrons of each Co^II ion at temperatures below 200 K. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1742–1745, September, 2007.     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.     

<Superscript>1</Superscript>H and <Superscript>31</Superscript>P nuclear spin-lattice relaxation in C-phosphorylated oximes

The ¹H spin-lattice relaxation times of the proton-bearing groups and the ³¹P spin-lattice relaxation times in C-phosphorylated oximes R¹C(=NOH)P(=O)R²R³ (R¹ = Ph, R² = R³ = OMe; R¹ = Ph, R² = OMe, R³ = OCH²CH²Br; R¹ = PhCH², R² = R³ = OCHMe²) and dioxime R²P(=O)C(=NOH)(CH₂)₄C(=NOH)P(=O)R² (R = OMe) in DMSO-d₆ were measured. The characteristic reorientation times of the whole molecules were estimated using the measured values of the ¹H relaxation times and the results of semiempirical PM3 quantum chemical calculations of the molecular geometries. The reorientation times were used to identify the contributions of different relaxation mechanisms to the rate of ³¹P spin-lattice relaxation. The anisotropy of the chemical shielding of ³¹P nuclei was evaluated from the difference between the ³¹P relaxation rates measured at 101.27 and 161.92 MHz.     

Specific features of absorption of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript> cations from aqueous solutions by calcium phosphates

Kinetic characteristics of the interaction of trisubstituted calcium phosphate Ca₃(PO₄)₂ · xH₂O with Cu²⁺, Zn²⁺, Co²⁺, and Pb²⁺ ions in aqueous solutions were studied.     

Molecular modeling of hydration properties of hydrophobic ions Li<Superscript>+</Superscript>@C<Subscript>60</Subscript> and K<Superscript>+</Superscript>@C<Subscript>60</Subscript>

The Gibbs free energies of solvation (ΔG _s) and the electronic structures of endohedral metallofullerenes M⁺@C₆₀ (M⁺= Li⁺, K⁺) were calculated within the framework of the density functional theory and the polarizable continuum model. In water environment, the equilibrium position of K⁺ is at the center of the fullerene cavity whereas that of Li⁺ is shifted by 0.14 nm toward the fullerene cage. The Li⁺ cation is stabilized by interactions with both the fullerene and solvent. The equilibrium structures of both endohedral metallofullerenes are characterized by very close ΔG _s values. In particular, the calculated ΔG _s values for K⁺@C₆₀ are in the range from −124 to −149 kJ mol⁻¹ depending on the basis set and on the type of the density functional. Molecular dynamics simulations (TIP3P H₂O, OPLS force field, water sphere of radius 1.9 nm) showed that the radial distribution functions of water density around C₆₀ and M⁺@C₆₀ are very similar, whereas orientations of water dipoles around the endohedral metallofullerenes resemble the hydration pattern of isolated metal ions.     

The standard thermodynamic characteristics of resolvation of the K<Superscript>+</Superscript>, Ca<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript>, and Br<Superscript>−</Superscript> ions in water-acetone mixtures

The standard real and chemical thermodynamic characteristics of transfer of the K⁺, Ca²⁺, Cd²⁺, and Br^? ions from water into water-acetone solvents of various compositions were analyzed to study the rules governing the solvation of these ions in mixed solvents and its special features. All calculations were performed within the framework of the vertical jet method at 298.15 K. The energy of resolvation as a function of ion charges and crystallographic radii was found to increase in the series K⁺ < Ca²⁺ < Cd²⁺ < Al³⁺     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Enhancing single-molecule magnet behavior of linear Co<Superscript>II</Superscript>-Dy<Superscript>III</Superscript>Co<Superscript>II</Superscript> complex by introducing bulky diamagnetic moiety

Single-molecule magnets (SMMs) are regarded as promising candidates for ultrahigh-density storage, quantum information processing and molecular spintronics. It is a crucial challenge for chemists to modulate magnetic dynamics of SMMs. Here, we successfully synthesized two 3d-4f polynuclear compounds [Co₂Dy(TTTT^Cl)₂(MeOH)]NO₃·3MeOH (1) and [Co₂Dy(TTTT^Cl)₂ (MeOH)][Co(HTTTT^Cl)](NO₃)₂·2.5MeOH·2H₂O (2), where H₃TTTT^Cl=2,2′,2′′-(((nitrilotris(ethane-2,1-diyl)) tris(azanediyl)) tris(methylene))tris-(4-chlorophenol). On applying the approach by co-crystallization of bulky diamagnetic moiety, the effective energy barrier enhances from 401 K (1) to 536 K (2), which are both among the highest d-f heterometallic SMMs.     

Quantum chemical analysis of possible fragmentation of [M + H]<Superscript>+</Superscript> and [M + Na]<Superscript>+</Superscript> complexes of monosubstituted methane,cyclohexane, and benzene derivatives in mass spectrometric studies

The formation and fragmentation energies of the proton and sodium cation complexes with monosubstituted methane, cyclohexane, and benzene derivatives in which carbon atoms are bonded to substituents (NH₂, OH, F, Cl, Br, ONO₂, NO₂, COOH, CN, and Ph) were calculated by the B3LYP/6-31G(d) method. For [M + Na]⁺ complexes, the formation energies are much lower (and differ from one another to a much lesser extent), while the dissociation energies are much higher, than the corresponding energies of the [M + H]⁺ complexes. Na⁺ cation shows a lower selectivity toward localization at functional groups in molecules compared to H⁺. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 246–249, February, 2008.     

<Superscript>234</Superscript>U/<Superscript>235</Superscript>U activity ratios as a probe for the <Superscript>238</Superscript>U/<Superscript>235</Superscript>U half-life ratio

High-resolution alpha-particle spectrometry was performed on three uranium materials enriched in ²³⁵U. Besides the ²³⁵U peaks, separate peaks belonging to impurity traces of ²³⁴U could be quantified. Relying on the isotopic composition of the uranium, as determined by mass spectrometry, the ratio of the half-lives of ²³⁸U and ²³⁵U was determined via the activity ratio of ²³⁴U and ²³⁵U in the materials. As an intermediate link, the ²³⁴U/²³⁸U half-life ratio was taken from published mass spectrometric analyses of ‘secular equilibrium’ uranium material. The resulting half-life ratio T _1/2(²³⁸U)/T _1/2(²³⁵U) = 6.351±0.031 is in agreement with the commonly adopted half-life values determined by Jaffey et al.     

Determination of activity ratios of <Superscript>238,239+240,241</Superscript>Pu, <Superscript>241</Superscript>Am, <Superscript>134,137</Superscript>Cs,and <Superscript>90</Superscript>Sr in Bulgarian soils

The origins of different artificial radionuclides found in soils from Northern and Southern Bulgaria was determined by measurements of their actual concentrations and respective ratios. On the basis of the measured mobility and concentrations of the investigated radionuclides in soils, it was estimated that after the Chernobyl accident the mean depositions of fresh ¹³⁷Cs were 3.0 ± 2.5 kBq/m² for Northern Bulgaria and 15 ± 7 kBq/m² for Southern Bulgaria. As a result of global fallout following atmospheric nuclear weapon tests in the 1950s, mean depositions (corrected to 1965) were calculated for Northern and Southern Bulgaria as follows: for ⁹⁰Sr—1.0 ± 0.5 and 2.3 ± 1.3 kBq/m², ²³⁸Pu—1.3 ± 0.8 and 2.8 ± 1.6 Bq/m², ^239+240Pu—15 ± 14 and 47 ± 38 Bq/m², and ²⁴¹Pu—520 ± 200 and 760 ± 260 Bq/m².