Sonoluminescence of terbium chloride in an H2O-D2O mixture

The effect of solvent deuteration on the multibubble sonoluminescence (SL) of an aqueous solution of terbium chloride was studied. The dependence of the intensity of the characteristic SL of the Tb^III ion on the composition of an H₂O-D₂O mixture is similar to an analogous dependence of its photoluminescence (PL) but with a much smaller isotope effect. In pure D₂O, the SL intensity increases by 4 times only compared to the SL in water, while the PL intensity increases by 10 times. The mechanism of inner-bubble excitation of lanthanide ions is considered. According to this mechanism, an additional “heterogeneous” channel of quenching of excited Tb^III ions appears, which is absent for PL. The proposed model satisfactorily describes the experimental data on the effect of solvent deuteration on the SL intensity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1074–1078, July, 2006.     

Prostanoids: LXXVII. Synthetic Approaches to Sterically Overcrowded Cyclopentenones

Condensation of (±)-5-allyl-2,3,5-trichloro-4,4-dimethoxy-2-cyclopentenone with phenylethynylmagnesium bromide in THF gave (±)-5-allyl-2,3,5-trichloro-4,4-dimethoxy-1-phenylethynyl-2-cyclopenten-1-ol which chemoselectively reacted with ozone at the terminal double bond, affording (±)-2,3,5-trichloro-5-formylmethyl-4,4-dimethoxy-1-phenylethynyl-2-cyclopenten-1-ol. Oxidation of the latter with H₂CrO₄ yielded a mixture of the expected product, (±)-5-carboxymethyl-2,3,5-trichloro-4,4-dimethoxy-1-phenylethynyl-2-cyclopenten-1-ol, and anomalous profound oxidation product, (±)-2,3,5-trichloro-5-carboxymethyl-4,4-dimethoxy-1-(2-oxo-2-phenylacetyl)-2-cyclopenten-1-ol. Attempts to remove protective methoxy groups in these compounds under standard conditions were unsuccessful.     

Phenylisocyanation and bromination studies on lanthanide β-diketonates

Summary Phenylisocyanation and bromination of some twenty lanthanide -diketonates: Ln(acac)₃, Ln(bzac)₃ and Ln(dbzm)₃ where Ln=Pr^III, Nd^III, Sm^III, Gd^III, Dy^III and Y^III and Ce(acac)₄, Ce(bzac)₄ and Ce(dbzm)₄ have been investigated. While phenylisocyanation gives the expected 3-substituted phenylamido product, bromination, for the first time, has been observed to yield a substituted product with flipping of one (or two) six-membered diketone ring to give a five-membered ring in which the entering bromine electrophile is bonded to the metal and a carbon atom. The other diketone rings, although -substituted, remain intact with respect to metal coordination. The substituted complexes have been characterised by i.r., u.v. and n.m.r. spectroscopy.     

Zur Reaktion von Fluorsilanen mit lithiierten Aminen

The reaction of fluorosilanes with lithium salts of bulky amines like tetramethyl-piperidine and di-tert. butylamine leads to stable aminofluorosilanes of the type R-SiF₂-NRR [R=F, C(CH₃)₃, C₆H₅, C₆H₄N(CH₃)₂]. Lithium salts of silylamines react analogously: R₂Si(NR-SiF₂R)₂ (R=R= =CH₃, R=C₆H₅). An eight membered Si–N-ring is obtained in the reaction of a disubstituted silylaminofluorosilane with the dilithium salt of a silylamine. The mass-,¹H-, and¹⁹F-NMR spectra of the above mentioned compounds are reported.     

Chromotropic acid,a fluorogenic chelating agent for aluminium(III)

Complexation of aluminium(III) with the fluorogenic ligand chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonic acid) has been revisited with the aim of using enhancement of the fluorescence intensity as an analytical tool. Complexation at the optimum pH4 was shown to lead to a 1:1 complex with a stability constant log ₁₁₀=18.4±0.7. The fluorogenic effect was thoroughly investigated. Nearly selective excitation of the chelate rather than the ligand could be achieved at wavelengths longer than 360 nm. For analytical purposes the main interfering ion was Ga³⁺. The strongest competing ligand was shown to be citric acid. Competitive complexation by acetate or formate ions can also make their use in a buffer at the usual concentration, 0.2 mol L^–1, questionable, whereas a 10^–2 mol L^–1 formic acid buffer was shown to be a good alternative. The calibration plot showed that the dependence of response on Al(III) concentration was linear up to 500 g L^–1; the detection limit was 0.65 g L^–1 (3SD _blank, n=10, SD=±1.4% at 10 g L^–1 and ±0.8% at 100 g L^–1). The analytical procedure was successfully applied to several samples of tap water and the results were in good agreement with those from AAS determination.     

Chemiluminescence and catalysis of decomposition of dispiro(diadamantane-1,2-dioxetane) in solutions of lanthanide perchlorates

Chemiluminescence (CL) accompanying the decomposition of dispiro(diadamantane-1,2-dioxetane) (1) in acetonitrile solutions of Eu^III, Gd^III, Tb^III, Pr^III, and Ce^III perchlorates was studied. In the presence of Eu^III, Tb^III, and Pr^III ions, the chemiluminescence spectra contain the luminescence bands of these ions. In the cases of Gd^III and Ce^III, the chemiluminescence is caused by deactivation of singlet-excited adamantanone (2). The excitation of the lanthanide ion depends on the existence of suitable energy levels at which intracomplex excitation transfer from the³n,π^* of ketone is possible. Chemiluminescence of1 increases in solutions of Eu^III and Tb^III. The yields of CL and excitation of the lanthanide ions in the decomposition of1 in the1·Eu^III and1\Tb^III complexes were determined: φ_Eu · =0.013 ± 0.003 and φ_Tb · =0.08±0.02. The fact that the efficiency for the population of the⁵D₄-level of Tb^III is higher than that for the⁵D₁ and⁵D₀-levels of Eu^III is related to the difference in the energy gap between the triplet level of2 and the excited levels of the lanthanides. For Part I, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 730–735, April, 1997.     

Mechanism of oxidation of selenium(IV) by cobalt(III) in perchloric acid — a kinetic study

Summary The kinetics of Co^III oxidation of Se^IV have been studied in aqueous HClO₄. The order with respect to Co^m is two the order with respect to Se^IV is one at low concentrations; two at high concentrations. The latter variation is attributed to the greater reactivity of the Se^IV dimier A mechanism involving complexation between oxidant and substrate is proposed. [CoOH]²⁺ is presumed to be the reactive Co^III species and H₂SeO₃ and HSeO ₃ ^– to be those of Se^IV. At 25° C, E_a, H and S for the monomeric path are 125.6±4.0 kJ mol^–1, 122.1±3.8 kJ mol^–1 and 206±12 JK^–1 mol^–1 respectively and those for the dimeric path are 88.6±3.6 kJ mol^–1, 85.9±3.4 kJ mol^–1 and 62.6±11.3 JK^–1 mol^–1 respectively.     

Sonoluminescence of aqueous solution of gadolinium chloride

A line of the Gd^III ion was detected at 311 nm in the multibubble sonoluminescence spectrum of a concentrated (1 mol L⁻¹) solution of gadolinium chloride. A comparison with the earlier studied sonoluminescence of the Ce^III and Tb^III ions shows that the Gd^III ion is excited in the volume and/or on the surface of cavitation bubbles upon collisions with “hot” particles. The efficiency of excitation of the lanthanide ions via this mechanism depends on the type of electron transition. For the same energy of the excited state, the efficiency of Gd^III excitation (f-f transition) exceeds by at least 50 times that of Ce^III excitation (f-d transition). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1341–1344, June, 2005.     

On the problem of predicting the activity of oxide and carbonate catalysts in some reactions of petrochemical synthesis

The problem of predicting the activity of oxide and carbonate catalysts for some reactions of petrochemical synthesis (vapor phase conversion of carboxylic acids, catalytic oxidation of asphaltic tar to bitumen) according to the established dependence of thermal stability variations of intermediates on the formation enthalpy of metal oxides or standard ele.trode potentials is discussed.

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Synthesis and photophysical properties of Ir<Superscript>III</Superscript>-Ln<Superscript>III</Superscript> (Ln = Nd,Yb, Er) bimetallic complexes containing bipyrimidines as bridging ligands

Bipyrimidines have been chosen as (N∧N)(N∧N) bridging ligands for connecting metal centers. Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes [Ir(dfppy)₂(μ-bpm)Ln(TTA)₃]Cl were synthesized by using Ir(dfppy)₂(bpm)Cl as the ligand coordinating to lanthanide complexes Ln(TTA)₃·2H₂O. The stability constants between Ir(dfppy)₂(bpm)Cl and lanthanide ions were measured by fluorescence titration. The obvious quenching of visible emission from Ir^III complex in the Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes indicates that energy transfer occurred from Ir^III center to lanthanides. NIR emissions from Nd^III, Yb^III, and Er^III were obtained under the excitation of visible light by selective excitation of the Ir^III-based chromophore. It was proven that Ir(dfppy)₂(bpm)Cl as the ligand could effectively sensitize NIR emission from Nd^III, Yb^III, and Er^III.     

Crystal-Chemical Classes of “Cambridge” Crystal Structures: Statistical Analysis of Topology

Crystals structures with organic carbon, i.e., organic and organometal compounds and coordination compounds with organic ligands are systematized based on the results of a statistical treatment of CSD (Cambridge Structural Database) data. The overwhelming majority of CSD structures are molecular crystals, which may be homomolecular or heteromolecular; the latter, in turn, are classified into molecular complexes, salts, crystal solvates, and crystal hydrates. Polymeric (nonmolecular) crystals occur much more rarely. For substances belonging to different crystal-chemical classes, distributions according to space groups and structural classes have been studied; considerable differences between the distributions have been found. In particular, it was established that chiral structures (with P2₁2₁2₁, P2₁, etc. symmetry) are met much more rarely among inorganic CSD structures with metals and metalloids than among organic structures consisting exclusively of organogen elements; the most striking examples are hydrates and salts containing Cl^–, Br^–, and I^– ions.     

Ruthenium clusters containing the [2.2] paracyclophane ligand: Recent developments in arene-cluster chemistry

In this article we review the synthesis, reactivity, and characterization of a number of clusters bearing the [2.2] paracyclophane ligand with nuclearities ranging from two to eight. Particular attention is focused on the different coordination modes that paracyclophane adopts; these being µ₁- ⁶, µ₂- ³ : ³, µ₃- ¹ : ² : ², and µ₃- ² : ² : ². Structural modifications which take place within the ring system on bonding in these various modes are also discussed.     

Metal chelates with some cellulose derivatives; part IV. Structural chemistry of HEC complexes

Reactions of hydroxyethyl cellulose (HEC) with Cr ^III, Ni^II, Co^II, or Cu^II chlorides in aqueous medium yielded complexes with formulae [M(HEC)Cl _m .n H ₂O], wherem =1 or 2 and n=2 or 3. HEC acted as a uninegatively charged bidentate ligand in the case of Cr^III and Ni^II, and as a neutral ligand in the case of Co^II and Cu^II complexes. The spectra showed that the binding sites in Cr^III and Ni^II complexes were the ether oxygen between two ethoxyl groups and the oxygen of the hydroxyl group; while in the Co^II and Cu^II complexes the binding sites were the oxygen of ethoxyl groups and the primary alcoholic O atom of glucopyranose rings. These complexes would most likely exhibit octahedral geometry with Cr^III, Ni^II, and Co^II, but square planar configuration in the case of the Cu^II complex. The ligand parameters of the Cr^III, Ni^II, and Co^II metal chelates were calculated in different solvents and at different temperatures. The thermal stability of the above complexes was investigated and the overall thermodynamics functions G⁰, H⁰, and S⁰, associated with complex formation, were estimated.     

Synthesis,structure, and properties of a new trinuclear iron cluster, [(MeOH)(H2O)2Fe3(μ3-O)(μ-OOCC6H4OCH2C5H4NH)6] (ClO4)7 · · 8MeOH · 3.5H2O

Reactions of iron(m) salts with a new bidentate ligand, which is potentially capable of forming binuclear iron complexes upon complexation, were studied. Under various conditions, we succeeded in isolating only the trinuclear cationic complex (Fe^III ₃(O₂CR)6(₃-)17+ (1), where RCO₂ is 2-(pyrid-2-ylmethoxy)benzoic acid protonated at the pyridyl moiety. The structure of 1 was established by spectral, magnetic, and X-ray structural studies. Cyclic voltammetry in McCN in the temperature range from -35 to 20 °C demonstrated that 1 undergoes successive Fe^IIIFe^II reduction in three one-electron stages, which is indicative of the electronic interaction between iron atoms in the complex.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2086–2092, August, 1996.     

Structure and magnetic properties of diaqua(4,4′-bipyridine) terbium(III) and the zinc(II) carboxylate dimer [Tb2Zn2(CH2C(CH3)COO)10(bipy)(H2O)2]2

A novel heteronuclear complex, [Tb₂Zn₂L₁₀(bipy)(H₂O)₂]₂ (HL = -methylacrylic acid, bipy = 4,4-bipyridine), was synthesized and characterized by elemental analysis and i.r. absorption spectra. Its structure, determined by X-ray diffraction, is a discrete octanuclear molecule, in which two Zn^II ions are linked by a bipy molecule and between Tb^III ions, or Tb^III and Zn^II ions are bridged by bidentate -methylacrylato groups. The temperature dependence of the magnetic susceptibility of the complex shows strong ferromagnetic interaction between the terbium atoms.     

Micelle formation of ethoxylated nonyl-phenols in aqueous solutions

The micelle formation of nonyl-phenols with various numbers of ethoxy groups (n _EO=10–40) was investigated in aqueous solutions and the study was focussed on the effect of temperature (293–323 K), the chain length and the inorganic electrolyte (NaCl) on the critical micelle concentration (c.m.c).The c.m.c. was determined by surface tension and interfacial tension measurements in a water/n-octane system. On the basis of the actual c.m.c. and its temperature dependence the thermodynamic functions of micelle formation (H° _m,S°_m,G°_m) were also calculated. The latter study comprised the determination of the thermodynamic function for unity ethoxy groups ((Y° _m)) as a function ofn _EO.According to the experimental results the micellar solutions are the more stable, the smaller the number of ethoxy groups in the tenside molecule and the higher the temperature as well as the electrolyte content of the system.     

A Bis(pyridine N‐oxide) Analogue of DOTA: Relaxometric Properties of the GdIII Complex and Efficient Sensitization of Visible and NIR‐Emitting Lanthanide(III) Cations Including PrIII and HoIII

We report the synthesis of a cyclen‐based ligand (4,10‐bis[(1‐oxidopyridin‐2‐yl)methyl]‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid= L1 ) containing two acetate and two 2‐methylpyridine N‐oxide arms anchored on the nitrogen atoms of the cyclen platform, which has been designed for stable complexation of lanthanide(III) ions in aqueous solution. Relaxometric studies suggest that the thermodynamic stability and kinetic inertness of the Gd^III complex may be sufficient for biological applications. A detailed structural study of the complexes by ¹H NMR spectroscopy and DFT calculations indicates that they adopt an anti‐Δ(λλλλ) conformation in aqueous solution, that is, an anti‐square antiprismatic (anti‐SAP) isomeric form, as demonstrated by analysis of the ¹H NMR paramagnetic shifts induced by Yb^III. The water‐exchange rate of the Gd^III complex is ${k{{298\hfill \atop {\rm ex}\hfill}}}$ =6.7×10⁶ s^?1, about a quarter of that for the mono‐oxidopyridine analogue, but still about 50 % higher than the ${k{{298\hfill \atop {\rm ex}\hfill}}}$ of GdDOTA (DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid). The 2‐methylpyridine N‐oxide chromophores can be used to sensitize a wide range of Ln^III ions emitting in both the visible (Eu^III and Tb^III) and NIR (Pr^III, Nd^III, Ho^III, Yb^III) spectral regions. The emission quantum yield determined for the Yb^III complex (${Q{{{\rm L}\hfill \atop {\rm Yb}\hfill}}}$ =7.3(1)×10^?3) is among the highest ever reported for complexes of this metal ion in aqueous solution. The sensitization ability of the ligand, together with the spectroscopic and relaxometric properties of its complexes, constitute a useful step forward on the way to efficient dual probes for optical imaging (OI) and MRI.     

Thermodynamic study of the β-cyclodextrin benzyl-2-pyridyl ketone 2-pyridyl hydrazone inclusion process

Benzyl-2-pyridylketone-2-pyridylhydrazone and -cyclodextrin form a 1 : 1 adduct in water with a standard free energy change, G ^o, in the region of 14.2 kJ mol^–1 at 25°C, and an association constant of 275 M^–1 in the pH range 5–7. These values have been obtained by using the fluorimetric spectral changes associated with the inclusion process.     

Crystal and molecular structure of trans-diiodobis-(1-methyl-5-nitroimidazole)platinum(II)

Summary A new platinum complex of 1-methyl-5-nitroimidazole has been obtained and characterized by elemental analysis, i.r. and n.m.r. spectroscopy. The structure of [PtI₂-(C₄ H₅N₃O₂)₂] has been determined by single-crystal X-ray diffraction. The crystals are triclinic: P1, a = 15.640(3), b = 12.617(2), c = 6.701(1) , = 102.77(5), = 101.15(5), = 100.71(5)°, V = 1228.6(3) ³, Z = 3, D_x = 2.851(6) Mg m^–3, (MoK ) = 0.71069 , = 12.85 mm^–, F(000) = 948, final R = 0.038 for 2859 reflections. The complex consists of monomeric PtI₂(1-methyl-5-nitroimidazole)₂ units. The coordination geometry is square-planar. The two 1-methyl-5-nitroimidazole ligands are trans coordinated to platinum.     

Mechanism of recoil implantation reactions of technetium and ruthenium in metal acetylacetonates

Recoil implantation of Tc and Ru in metal acetylacetonates were performed using ruthenium metal as a source and M^III/acac/₃ and M^II/acac/₂ complexes as catchers. The recoil atoms were obtained by¹⁰⁰Ru/, p/^99mTc and⁹⁸Ru/, n/⁹⁷Ru reactions. The yields of Tc/acac/₃ and Ru/acac/₃ were clearly dependent on the force constant of the bond between the central metal atom and oxygen in acetylacetone K/M–O/. A plot of the yield vs. 1/K(M–O) showed a linear relationship. However, the yield of Tc/acac/₂ implanted in M/acac/₂ did not show such a dependence on the force constant. The difference of the mechanism of complex formation between Tc/acac/₃ and Tc/acac/₂ was discussed on the basis of a reaction cage surrounding the recoil atom and of reaction time necessary for competition between the recoil atom and the central metal of the catcher complex.