Thorium Complexes Research Articles

On the origin of exothermic DSC peak prior to glycine-nitrate gel combustion during ThO2 synthesis

Nature of interaction between Th4+, glycine, and nitrate ions and associated thermo chemical-changes prior to glycine-nitrate gel combustion for the synthesis of ThO2 powder have been investigated by DSC and XRD techniques, combined with FT-IR and Raman spectroscopic measurements. Combustion of dried gel is preceded by a distinct exothermic process; origin of which has been probed by systematic analysis of DSC thermograms. Mono- and multi-nuclear complexes of thorium with glycine exist in the gel before combustion and their relative concentrations depend on the starting stoichiometry, heat treatment temperature and extent of water content. Depending on the rate at which water gets removed from the gel, complexes mentioned above undergo rapid or slow aggregation to form amorphous or crystalline molecular solids. Observed additional exothermic peak in DSC thermogram prior to combustion of the gel confirms the formation of such molecular solids.

An Instant, Green, Microwave Irradiated Process for the Preparation of Advanced, Hybrid, Nanoflower of Thorium Oxide and Thorium Oxalate Hydrate Useful for Broad Application Spectrum

We report a facile and reproducible method to synthesize advanced, homogenized, hybrid, nanoflower of thorium oxide and thorium oxalate hydrate material via a novel, green, microwave irradiated chemical process. The Nanoflowers can be successfully synthesized using thorium nitrate penta hydrate as the metal source along with two different capping agents, cetyltrimethyl ammonium bromide and 4-amino-1H-pyrimidine-2-one respectively in the ubiquity of microwave irradiation having power source 230V at the temperature of 45°C for 15 minutes to get the desired product. The synthesized material was characterized by various complementary techniques namely XRD, FTIR, PL, TGA/DSC curve, SEM and EDX. The 3D nanoflowers structure, so formed, resembles a natural Peony flower. The applications of synthesized material lies in the area of making thorium metal, densified thorium oxide, carbide and nitride, anhydrous thorium complexes and thorium boron silicates glasses.

Stability constants and spectroscopic properties of thorium(IV)-arsenazo III complexes in perchloric acid

The complexation of thorium with arsenazo III in perchloric acid was quantitatively investigated with ultraviolet–visible (UV–Vis) absorption spectroscopy. The UV–Vis absorption of both 1:1 and 1:2 (thorium to arsenazo III) complexes in perchloric acid were found to be highly enhanced than the previously reported absorption of the complexes in hydrochloric acid. The stability constants of thorium-arsenazo III complexes were determined via computational analysis, and the SIT (specific ion interaction theory) was employed to evaluate the dependence on ionic strength. This work contributes to a better understanding of the speciation and spectroscopic properties of thorium-arsenazo III complexes at high ionic strength.

Functionalization of Carbon Monoxide and tert‐Butyl Nitrile by Intramolecular Proton Transfer in a Bis(Phosphido) Thorium Complex

AbstractWe report intramolecular proton transfer reactions to functionalize carbon monoxide and tert‐butyl nitrile from a bis(phosphido) thorium complex. The reaction of (C5Me5)2Th[PH(Mes)]2, Mes=2,4,6‐Me3C6H2, with 1 atm of CO yields (C5Me5)2Th(κ2‐(O,O)‐OCH2PMes‐C(O)PMes), in which one CO molecule is inserted into each thorium–phosphorus bond. Concomitant transfer of two protons, formerly coordinated to phosphorus, are now bound to one of the carbon atoms from one of the inserted CO molecules. DFT calculations were employed to determine the lowest energy pathway. With tert‐butyl nitrile, tBuCN, only one nitrile inserts into a thorium–phosphorus bond, but the proton is transferred to nitrogen with one phosphido remaining unperturbed affording (C5Me5)2Th[PH(Mes)][κ2‐(P,N)‐N(H)C(CMe3)P(Mes)]. Surprisingly, reaction of this compound with KN(SiMe3)2 removes the proton bound to nitrogen, not phosphorus.

Functionalization of Carbon Monoxide and tert-Butyl Nitrile by Intramolecular Proton Transfer in a Bis(Phosphido) Thorium Complex.

We report intramolecular proton transfer reactions to functionalize carbon monoxide and tert-butyl nitrile from a bis(phosphido) thorium complex. The reaction of (C5 Me5 )2 Th[PH(Mes)]2 , Mes=2,4,6-Me3 C6 H2 , with 1 atm of CO yields (C5 Me5 )2 Th(κ2 -(O,O)-OCH2 PMes-C(O)PMes), in which one CO molecule is inserted into each thorium-phosphorus bond. Concomitant transfer of two protons, formerly coordinated to phosphorus, are now bound to one of the carbon atoms from one of the inserted CO molecules. DFT calculations were employed to determine the lowest energy pathway. With tert-butyl nitrile, t BuCN, only one nitrile inserts into a thorium-phosphorus bond, but the proton is transferred to nitrogen with one phosphido remaining unperturbed affording (C5 Me5 )2 Th[PH(Mes)][κ2 -(P,N)-N(H)C(CMe3 )P(Mes)]. Surprisingly, reaction of this compound with KN(SiMe3 )2 removes the proton bound to nitrogen, not phosphorus.

Вимірювання періоду напіврозпаду ядра 212Po за допомогою насиченого торієм рідкого сцинтилятора

Precise measurement of half-life of $^{212}$Po (one of the daughter nuclides in radioactive chain of $^{232}$Th) was realized by means of liquid scintillator based on toluene doped by complex of thorium and trioctylphosphine oxide with concentration of Th $\sim0.1$ mass %. Fast photomultiplier tube and high frequency oscilloscope were used to acquire the scintillation signals waveforms. The algorithms were developed to find pairs of $^{212}$Bi beta-decays and subsequent $^{212}$Po alpha-decays, to calculate time differences between the events in the pair, and to build $^{212}$Bi beta-decay and $^{212}$Po alpha-decay energy spectra. Preliminary the $^{212}$Po half-life is $T_{1/2} = (294.8 \pm 1.9)$ ns. The experiment is in progress aiming at reduction of the statistical and systematic uncertainties.

Efficient extraction of multivalent cations from aqueous solutions into sitinakite-based sorbents

A highly selective adsorbent for multivalent cationic species based on a sitinakite-type titanosilicate was prepared from a leucoxene ore enrichment waste. The synthesized material was used as for the selective removal of alkali-earth strontium (II) and barium (II) cations as well as for the cationic species based on the natural isotopes of uranium, radium, and thorium from aqueous solutions. The influence of such parameters as the pH, the initial concentration of the ions, the presence of other electrolytes on the sorption parameters was investigated. The sorption capacity of the synthesized material at ambient conditions is 80 and 110 mg/g for Sr2+ and Ba2+, respectively, and it rises with increasing temperature. Furthermore, the material shows a high selectivity towards radionuclides of radium, uranium, and thorium. By using the current titanosilicate materials, the extracting degree of over 99% could be achieved when extracting these species from their respective standard aqueous solutions. The origin of the high adsorption selectivity for cationic complexes of thorium and uranium is rationalized based on periodic density functional theory calculations. The obtained results indicate that the described materials could be promising and inexpensive sorbents for the selective extraction of radioactive isotopes and particularly those of Sr, Ba and U, Th, Ra.

Solid State Chemistry of Ten-Fold Coordinate Thorium(IV) Complexes with Oxalates in the Presence of Ammonium and Hydrazinium Ions

Double and triple thorium oxalates have been synthesized by successive evaporation of a solution of thorium nitrate, ammonium, or hydrazinium oxalate and hydrogen peroxide. Compounds M6Ca2Th2(C2O4)9·nH2O (M = NH4+, N2H5+) (1) were first accidentally obtained due to the unexpected presence of calcium as impurities in the thorium nitrate used. Further evaporation led to the M2Th2(C2O4)5·nH2O (M = NH4+, N2H5+) (2) precipitation. After an additional evaporation of 2 weeks, compounds (2) transform into M4Th(C2O4)4·nH2O (M = NH4+, N2H5+) (3). In the three compounds, thorium is coordinated by five bidentate oxalate ions. In (1) Th(C2O4)5 entities share an oxalate ion to form dimeric units further connected by Ca(C2O4)5 (M = NH4+) or Ca(C2O4)5(H2O) (M = N2H5+) entities to build three-dimensional (3D) frameworks. Compounds (2) exhibit a 3D honeycomb thorium oxalate framework. Compounds (3) contain chains of oxalate-shared Th(C2O4)5 entities, whereas, in solution, the compound (NH4)2Th2(C2O4)5·1.5H2O (2) reacts with oxalate ions and turns into compound (NH4)4Th(C2O4)4·4H2O (3); in the solid state the chains of the compound (3) condense to form the 3D framework of the compound (2) and release solid ammonium oxalate.

A Relativistic DFT Probe of Thorium and Protactinium Complexes Supported by Heterocalix[4]arene and Redox Properties of Early‐Middle Actinides

AbstractThorium and protactinium complexes of trans‐calix[2]benzene[2]pyrrolide (H2L) have been examined using a relativistic density functional theory, where the metal center has +IV and +III oxidation states and is saturated by a borohydride donor. Good agreement in geometry parameters has been achieved for the thorium(VI) complex compared with its experimentally obtained analogue. Three types of conformers, labeled as (ArL)(Anm)(2HB), (ArL)(Anm)(3HB) and (PlL)(Anm)(3HB) (An=Th and Pa, m=VI and III), are energetically favored for each complex. The first and last configurations are found to be the most stable for tri‐ and tetravalent complexes, respectively. Intriguing δ(An−Ar) bonding(s) are revealed for trivalent complexes (ArL)(AnIII)(2HB); and (PlL)(PaIV)(3HB) has a Pa(5f)‐dominated HOMO, while (PlL)(ThIV)(3HB) displays a 5f06d07s0 electronic configuration. Exothermic process was calculated for reactions starting from actinide borohydride sources and various macrocyclic ligands. From a thermodynamic perspective, this provides synthetically accessible possibility of these complexes. The mechanism of reducing tetra‐ to trivalent actinide complexes has been proposed. Reduction potentials were calculated to follow the order of Th < Pa < U < Np < Pu, which well reproduces reported results of aquo AnVI/AnIII ions.

CONCENTRATION OF THORIUM (IV) BY CHELATING SORBENT

The paper analyses complexation of thorium(IV) with 2,3,4-trihydroxy-4’-fluoroazobenzene. A complex is formed immediately after mixing the components. Their molar ratio (1:2) was established using the methods of Starik–Barbanel relative yield, equilibrium shift and isomolar series. The maximum light absorption of the complex is observed at 440 nm, with the molar absorption coefficient being equal to 1.80×10 4 . In this work, we synthesised a new sorbent containing fragments of para-aminosalicylic acid. Identification of sorbents was carried out using IR spectroscopy. Sorption was studied in static and dynamic modes. The optimal conditions for concentration were investigated. The magnitude of the sorption and the degree of metal extraction was calculated from its residual concentration in the solution using a spectrophotometric method. Our results show that the maximum sorption is observed at pH = 4. In the course of preliminary kinetic experiments, it was found that the maximum sorption of cadmium is attained within 2 hours, remaining practically at the same level thereafter. The effect of the ionic strength of the solution was studied using the photometric method. Thorium(IV) was sorbed from solutions having an ionic strength of 0.1–1.4. It is shown that a significant decrease in the sorption of thorium(IV) occurs in solutions with an ionic strength of more than 0.2 M. The effect of metal concentration on sorption was also investigated. An isotherm of thorium sorption by the synthesised sorbent was constructed. An increased concentration of thorium(IV) in the solution leads to an increase in the amount of sorbed metal, with the maximum concentration being reached at 1856 mg/l. We also studied the effect of various acids (HClО 4 , H2SО 4 , HNО 3 , HCl) on the desorption of thorium(IV) from the sorbent: thorium(IV) was quantitatively desorbed by 2 M nitric acid. The degree of extraction of thorium ions (IV) under optimal conditions exceeds 95%. The study has revealed the possibility of using the matrix of a copolymer of maleic anhydride and styrene modified by para-aminosalicylic acid for sorption-photometric determination of thorium(IV). Following regeneration, this sorbent can be reused.

Complexation of thorium with pyridine monocarboxylate-N-oxides: Thermodynamic and computational studies.

The feed wastes and waste water treatment plants are the major sources for the entry of N-oxides into the soils then to aquatic life. The complexation of actinides with potentially stable anthropogenic ligands facilitate the transportation and migration of the actinides from the source confinement. The present study describes the determination of thermodynamic parameters for the complexation of Th(IV) with the three isomeric pyridine monocarboxylates (PCNO) namely picolinic acid-N-oxide (PANO), nicotinic acid-N-oxide (NANO) and isonicotinic acid-N-oxide (IANO). The potentiometric and isothermal calorimetric titrations were carried out to determine the stability and enthalpy of the formations for all the Th(IV)-PCNO complexes. Th-PANO complexes are more stable than Th-NANO and Th-IANO complexes which can be attributed to chelate formation in the former complexes. Formation of all the Th-PCNO complexes are endothermic and are entropy driven. The geometries for all the predicted complexes are optimized the energies, bond distances and charges on individual atoms are obtained using TURBOMOLE software. The theoretical calculation corroborated the experimental determinations.

Oxovanadium(IV), cerium(III), thorium(IV) and dioxouranium(VI) complexes of 1-ethyl-4-hydroxy-3-(nitroacetyl)quinolin-2(1H)-one: Synthesis, spectral, thermal, fluorescence, DFT calculations, antimicrobial and antitumor studies

A new series of mononuclear oxovanadium(IV), cerium(III), thorium(IV) and dioxouranium(VI) complexes of a quinolinone ligand; 1-ethyl-4-hydroxy-3-(nitroacetyl)quinolin-2(1H)-one (H2L) have been synthesized. The metal complexes were characterized by different techniques such as elemental and thermal analyses, IR, 1H NMR, electronic, ESR, mass spectra and powder XRD, TEM in addition to magnetic susceptibility and conductivity measurements. The quinolinone ligand acts as a dibasic bidentate ligand forming mononuclear complexes, which can be formulated as: [(L)VO(H2O)2]·0.5H2O, [(L)M(NO3)x(H2O)y]·nH2O; M = Ce or Th, x = 1 or 2, y = 3 or 4 and n = 2 or 7 and [(L)UO2(H2O)x(MeOH)y]·nH2O; x = 2 or 3, y = 0 or 1 and n = 0.5 or 2.5. The photoluminescent properties of the prepared complexes were studied. The ligand and its thorium(IV) complex are characterized by an intense green emission. Kinetic parameters (Ea, A, ΔH, ΔS and ΔG) of the thermal decomposition stages have been evaluated using Coats–Redfern equations. The geometry of the ligand and its oxovanadium(IV) complex has been optimized using density functional theory (DFT). Total energy, energy of HOMO and LUMO, dipole moment and structure activity relationship were performed and confirmed practical antimicrobial and antitumor results. The antimicrobial activity of the ligand and its metal complexes was conducted against the microorganisms S. aureus, K. pnemonia, E. coli, P. vulgaris and C. albicans and the MIC values were determined. The antitumor activity of the ligand and its metal complexes was investigated against human Hepatocelluar carcinoma and human breast cancer cell lines.

Understanding the Scarcity of Thorium Peroxide Clusters.

The reaction of Th(NO3)4·5H2O with 3 equiv of 2,2',6',2″-terpyridine (terpy) in a mixture of acetonitrile and methanol results in formation of the trinuclear thorium peroxide cluster [Th(O2)(terpy)(NO3)2]3. This cluster is assembled via bridging by μ-η2:η2 peroxide anions between thorium centers. It decomposes upon removal from the mother liquor to yield Th(terpy)(NO3)4 and Th(terpy)(NO3)4(EtOH). The peroxide formation appears to be radiolytic in origin and is, most likely, generated from radiolysis of water by short-lived daughters generated from 232Th decay. This cluster does not form when freshly recrystallized Th(NO3)4·5H2O is used as the starting material and requires an aged source of thorium. Analysis of the bonding in these clusters shows that, unlike uranium(VI) peroxide interactions, thorium(IV) complexation by peroxide is quite weak and largely ionic. This explains its much lower stability, which is more comparable to that observed in similar zirconium(IV) peroxide clusters.

Complexation of Th(IV) with sulfate in aqueous solution at 10–70 °C

The applicability of spectrophotometry or H+-potentiometry to the studies of the complexation of thorium(IV) in aqueous solutions is limited because Th(IV) does not have characteristic optical absorption in UV/Vis/Near IR region and H+-electrode is not sensitive in solutions of high acidity that needs to be maintained to prevent the hydrolysis of Th(IV). In the present work, the technique of calorimetric titration was used to determine the heat of reaction for the complexation of Th(IV) with sulfate in the temperature range of 10–70°C. The equilibrium constants and enthalpy of complexation were determined simultaneously from the calorimetric data. It was observed that the enthalpy of complexation is endothermic at 10°C, and become more endothermic as the temperature is increased. Despite of this, the complexes, Th(SO4)2+ and Th(SO4)2(aq), become more stable at higher temperatures due to the increasingly more positive entropy of complexation that exceeds the increase of enthalpy. The trends in the stability of sulfate complexes with tetravalent actinides (Th4+, U4+, Np4+, and Pu4+) are discussed in terms of electrostatic interactions that correlate with the ionic radii of the metal cations.

Synthesis, characterization and catalytic performances of benzimidazolin-2-iminato actinide (IV) complexes in the Tishchenko reactions for symmetrical and unsymmetrical esters

A new family of benzimdazolin-2-iminato actinide−(IV) complexes [(Bim7-MeDipp/MeN)An(N(SiMe3)2)3] (An = U (3), Th (4)) and [(Bim4-MeDipp/MeN)An(N(SiMe3)2)3] (An = U (5), Th (6)) were synthesized and their solid state structures were established by single-crystal X-ray diffraction analysis. The catalytic performances of complexes 3–6 towards the homo- and cross-coupling of aldehydes (Tishchenko reaction) were studied and the thorium complexes 4 and 6 displayed moderate to high activities for the production of the corresponding symmetric and unsymmetrical esters. Coupling of aldehyde and alcohols, known as the tandem proton-transfer esterification, and the intermolecular coupling reaction between aldehyde and trifluoromethylketones were also investigated by these thorium complexes, indicating a complementary method to obtain unsymmetrical esters selectively. Plausible mechanisms for these reactions are proposed based on stoichiometric studies.

Synthesis, Characterization and Antibacterial Activity of Thorium(IV), Dioxouranium(VI), Cobalt(II), Nickel(II), Copper(II) and Zinc(II) Complexes with Picolinoyl Hydrazones

Synthesis, Characterization and Antibacterial Activity of Thorium(IV), Dioxouranium(VI), Cobalt(II), Nickel(II), Copper(II) and Zinc(II) Complexes with Picolinoyl Hydrazones

Synthesis, Structure, and Reactivity of the Sterically Crowded Th3+ Complex (C5Me5)3Th Including Formation of the Thorium Carbonyl, [(C5Me5)3Th(CO)][BPh4

The Th3+ complex, (C5Me5)3Th, has been isolated despite the fact that tris(pentamethylcyclopentadienyl) complexes are highly reactive due to steric crowding and few crystallographically characterizable Th3+ complexes are known due to their highly reducing nature. Reaction of (C5Me5)2ThMe2 with [Et3NH][BPh4] produces the cationic thorium complex [(C5Me5)2ThMe][BPh4] that can be treated with KC5Me5 to generate (C5Me5)3ThMe, 1. The methyl group on (C5Me5)3ThMe can be removed with [Et3NH][BPh4] to form [(C5Me5)3Th][BPh4], 2, the first cationic tris(pentamethylcyclopentadienyl) metal complex, which can be reduced with KC8 to yield (C5Me5)3Th, 3. Complexes 1-3 have metrical parameters consistent with the extreme steric crowding that previously has given unusual (C5Me5)- reactivity to (C5Me5)3M complexes in reactions that form less crowded (C5Me5)2M-containing products. However, neither sterically induced reduction nor (η1-C5Me5)- reactivity is observed for these complexes. (C5Me5)3Th, which has a characteristic EPR spectrum consistent with a d1 ground state, has the capacity for two-electron reduction via Th3+ and sterically induced reduction. However, it reacts with MeI to make two sterically more crowded complexes, (C5Me5)3ThI, 4, and (C5Me5)3ThMe, 1, rather than (C5Me5)2Th(Me)I. Complex 3 also forms more crowded complexes in reactions with I2, PhCl, and Al2Me6, which generate (C5Me5)3ThI, (C5Me5)3ThCl, and (C5Me5)3ThMe, 1, respectively. The reaction of (C5Me5)3Th, 3, with H2 forms the known (C5Me5)3ThH as the sole thorium-containing product. Surprisingly, (C5Me5)3ThH is also observed when (C5Me5)3Th is combined with 1,3,5,7-cyclooctatetraene. [(C5Me5)3Th][BPh4] reacts with tetrahydrofuran (THF) to make [(C5Me5)3Th(THF)][BPh4], 2-THF, which is the first (C5Me5)3M of any kind that does not have a trigonal planar arrangement of the (C5Me5)- rings. It is also the first (C5Me5)3M complex that does not ring-open THF. [(C5Me5)3Th][BPh4], 2, reacts with CO to generate a product characterized as [(C5Me5)3Th(CO)][BPh4], 5, the first example of a molecular thorium carbonyl isolable at room temperature. These results have been analyzed using density functional theory calculations.

Two novel thorium organic frameworks constructed by bi- and tritopic ligands

Abstract Two thorium organic frameworks, Th(BDC)2 and Th(OH)(BCPBA) have been hydrothermally synthesized using 1,4-benzenedicarboxylic acid (H2BDC) and 3,5-bi(4-carboxyphenoxy)benzoic acid (H3BCPBA), respectively. The obtained two compounds were determined by single-crystal XRD, and they exhibited two new topologies. Th(BDC)2 shows a 3-dimensional (4,4,8)-connected framework with the Schläfli symbol of (414·612·82)(42·63·8)(44·62), and it is a mononuclear thorium(IV) complex. Th(OH)(BCPBA) possesses a (4,6)-connected topology with the Schläfli symbol of (415)2(46)3, and it has a dinuclear thorium(IV) asymmetric unit with the shortest Th–Th distances. Viewing along suitable directions, channels with different shapes can be found in the obtained two frameworks. Based on calculation with PLATON, the amount of void space is 21.9% and 13.5% in Th(BDC)2 and Th(OH)(BCPBA), respectively. Density functional theory (DFT) studies revealed that the metal-ligand interactions were mainly of ionic character in both compounds and the hydroxyl ions might play an important role in the stability of dinuclear thorium(IV) of Th(OH)(BCPBA).

Thorium complexes possessing expanded ring N-heterocyclic iminato ligands: synthesis and applications.

Six and seven membered N-heterocyclic iminato ligands (L) are introduced allowing access a new class of Th(iv) complexes of the type Cp*2Th(L)(CH3). These complexes were studied in the Tishchenko reaction. Stoichiometric reactions together with kinetic and thermodynamic studies permit us to propose a plausible mechanism.

Benzoquinonoid-bridged dinuclear actinide complexes

We report the coordination chemistry of the tripodal tris[2-amido(2-pyridyl)ethyl]amine ligand, L, with thorium(iv) and uranium(iv). Using a salt-metathesis strategy from the potassium salt of this ligand, K3L, new actinide complexes were isolated, namely the dimeric thorium complex [ThCl(L)]2 (1) and the monomeric uranium complex UI(THF)(L) (2); under different crystallisation conditions, the dimeric uranium complex is also isolated, [UI(L)]2 (2-dimer). With the aim of studying electronic phenomena such as magnetic exchange between two actinide ions, we have synthesised the first examples of dinuclear, quinoid-bridged actinide complexes from dianionic 2,5-bis[2,6-(diisopropyl)anilide]-1,4-benzoquinone (QDipp) and 2,5-bis[2-(methoxy)anilide]-1,4-benzoquinone (QOMe) ligands. The resulting complexes are [Th(L)]2QDipp (3), [Th(THF)(L)]2QOMe (5) and [U(L)]2QOMe (6). The targeted [U(L)]2QDipp complex (4) could not be isolated. All isolated complexes have been characterised by spectroscopic methods and X-ray crystallography. The uranium(iv) complexes 2-dimer and 6 have been studied by SQUID magnetometry but indicate that there is negligible magnetic exchange between the two uranium(iv) ions. The reduced form of 6, [K(18-c-6)][6-] is unstable and highly sensitive, but X-ray crystallography indicates that it is a novel UIVUIV complex bridged by a quinoid-radical.