Thermochromatography study of volatile polonium species in various gas atmospheres

Phenomena related to the volatilization of polonium and its compounds are critical issues for the safety assessment of the innovative lead–bismuth cooled type of nuclear reactor or accelerator driven systems. The formation and volatilization of different species of polonium and their interaction with fused silica was studied by thermochromatography using carrier gases with varied redox potential. The obtained results show that under inert and reducing conditions in the absence of moisture, elemental polonium is formed. Polonium compounds more volatile than elemental polonium can be formed if traces of moisture are present in both inert and reducing carrier gas. The use of dried oxygen as carrier gas leads to the formation of polonium oxides, which are less volatile than elemental polonium. It was also found that the volatility of polonium oxides increases with increasing oxidation state. In the presence of moisture in an oxidizing carrier gas, species are formed that are more volatile than the oxides and less volatile than the elemental polonium. Considering the redox potential of the carrier gas those species are likely oxyhydroxides.

Directed Metalation Cascade To Access Highly Functionalized Thieno2,3-fbenzofuran and Exploration as Building Blocks for Organic Electronics

A tandem directed metalation has been successfully applied to the preparation of thieno2,3-fbenzofuran-4,8-dione, providing an efficient and facile approach to symmetrically and unsymmetrically functionalize the thieno2,3-fbenzofuran core at the 2,6 positions as well as to introduce the electron-withdrawing or -donating groups (EWG or EDG) at its 4,8 positions. The presence of various functional groups makes late-stage derivatization attainable.

New copper(II) complexes with isoconazole: Synthesis, structures and biological properties

There is an increasing demand for novel metal-based complexes with biologically relevant molecules in technology and medicine. Three new Cu(II) coordination compounds with antifungal agent isoconazole (L), namely mononuclear complexes CuCl2(L)(2) (1), and Cu(O2CMe)(2)(L)(2)center dot 2H(2)O (2) and coordination polymer Cu(pht)(L)(2)(n) (3) (where H(2)pht - o-phthalic acid) were synthesized and characterized by IR spectroscopy, thermogravimetric analysis and X-ray crystallography. X-ray analysis showed that in all complexes, the isoconazole is coordinated to Cu(II) centres by a N atom of the imidazole fragment. In complex I, the square-planar environment of Cu(II) atoms is completed by two N atoms of isoconazole and two chloride ligands, whereas the Cu(II) atoms are coordinated by two N atoms from two isoconazole ligands and two O atoms from the different carboxylate residues: acetate in 2 and phthalate in 3. The formation of an infinite chain through the bridging phthalate ligand is observed in 3. The biosynthetic ability of micromycetes Aspergillus niger CNMN FD 10 in the presence of the prepared complexes 1-3 as well as the antifungal drug isoconazole were studied. Complexes 2 and 3 accelerate the biosynthesis of enzymes (beta-glucosidase, xylanase and endoglucanase) by this fungus. Moreover, a simplified and improved method for the preparation of isoconazole nitrate was developed.

A Donor-Acceptor Tetrathiafulvalene Ligand Complexed to Iron(II): Synthesis, Electrochemistry, and Spectroscopy of Fe(phen)(2)(TTF-dppz)(PF6)(2)

The synthesis and photophysical properties of the complex Fe(phen)(2)(TTF-dppz)(2+) (TTF-dppz = 4',5'-bis-(propylthio)tetrathiafulvenylidipyrido3,2-a:2',3'-c-phenazine, phen = 1,10-phenanthroline) are described. In this complex, excitation into the metal ligand charge transfer bands results in the population of a high-spin state of iron(II), with a decay lifetime of approximately 1.5 ns, in dichloromethane, at room temperature. An intraligand charge transfer state can also be obtained and has a lifetime of 38 ps. A mechanism for the different states reached is proposed based on transient absorption spectroscopy.

A Pt(II) complex with both a phenanthroline and a tetrathiafulvalene-extended dithiolate ligand: Synthesis, crystal structure, electrochemical and spectroscopic properties

The reaction of 4,5-bis(2'-cyanoethylsulfanyl)-4',5'-dipropylthiotetrathiafulvalene with Pt(phen)Cl-2 (phen = 1,10-phenanthroline) with CsOH as base in CH3OH-THE affords the target complex I in 44% yield. This complex crystallizes in the monoclinic space group P2(1)/c, M = 790.01, a = 12.1732(12), b = 15.851(2), c = 14.5371(16) angstrom, beta = 107.693(12)degrees, V = 2672.4(5) angstrom(3) and Z = 4. It undergoes two reversible single-electron oxidation and two irreversible reduction processes. An intense electronic absorption band at 15200 cm(-1) (658 nm) in CH2Cl2 is assigned to the intramolecular mixed metal/ligand-to-ligand charge transfer (LLCT) from a tetrathiafulvalene-extended dithiolate-based HOMO to a phenanthroline-based LUMO. This band shifts hypsochromically with increasing solvent polarity. Systematic changes in the optical spectra upon oxidation allow precise tuning of the oxidation states of 1 and reversible control over its optical properties. Irradiation of 1 at 15625 cm(-1) (640 nm) in glassy solution below 150K results in emission from the (LLCT)-L-3 excited state. GRAPHICS (C) 2013 Elsevier Ltd. All rights reserved.

Synthesis and Redox and Photophysical Properties of Benzodifuran-Spiropyran Ensembles

Two benzodifuran (BDF)-coupled spiropyran (SP) systems and their BDF reference compounds were obtained in good yields through HuisgenMeldalSharpless click chemistry and then subjected to investigation of their electrochemical and photophysical properties. In both SP and merocyanine (MC) forms of the coupled molecules, the BDF-based emission is quenched to around 1 of the quantum yield of emission from the BDF reference compounds. Based on electrochemical data, this quenching is attributed to oxidative electron-transfer quenching. Irradiation at 366nm results in ring opening to the MC forms of the BDF-coupled SP compounds and the SP reference compound with a quantum efficiency of about 50. The rate constants for the thermal ring closing are approximately 3.4x103s1. However, in the photostationary states the MC fractions of the coupled molecules are substantially lower than that of the reference SP compound, attributed to the observed acceleration of the ring-closing reaction upon irradiation. As irradiation at 366nm invariably also excites higher-energy transitions of the BDF units in the coupled compounds, the ring-opening reaction is accelerated relative to the SP reference, which results in lower MC fractions in the photostationary state. Reversible photochromism of these BDF-coupled SP compounds renders them promising in the field of molecular switches.

Probing Charge Transfer in Benzodifuran-C-60 Dumbbell-Type Electron Donor-Acceptor Conjugates: Ground- and Excited-State Assays

Rigid electron donor-acceptor conjugates (1-3) that combine -extended benzodifurans as electron donors and C-60 molecules as electron acceptors with different linkers have been synthesized and investigated with respect to intramolecular charge-transfer events. Electrochemistry, fluorescence, and transient absorption measurements revealed tunable and structure-dependent charge-transfer processes in the ground and excited states. Our experimental findings are underpinned by density-functional theory calculations.

Benzo1,2-b:4,5-b 'difuran-based sensitizers for dye-sensitized solar cells

Two BDF-based organic sensitizers, as first examples for their use in dye-sensitized solar cells, are prepared and characterized. They yield promising power conversion efficiencies of up to 5.5 and high open circuit voltages up to 0.82 V. This work demonstrates that the BDF chromophore acts as an effective donor in organic sensitizers.

Photo-induced intramolecular charge transfer in an ambipolar field-effect transistor based on a pi-conjugated donor-acceptor dyad

A pi-conjugated tetrathiafulvalene-fused perylenediimide (TTF-PDI) molecular dyad is successfully used as a solution-processed active material for light sensitive ambipolar field-effect transistors with balanced hole and electron mobilities. The photo-response of the TTF-PDI dyad resembles its absorption profile. Wavelength-dependent photoconductivity measurements reveal an important photo-response at an energy corresponding to a PDI-localized electronic pi-pi* transition and also a more moderate effect due to an intramolecular charge transfer from the HOMO localized on the TTF unit to the LUMO localized on the PDI moiety. This work clearly elucidates the interplay between intra- and intermolecular electronic processes in organic devices.

Tetrathiafulvalene - Benzothiadiazoles as Redox-Tunable Donor - Acceptor Systems: Synthesis and Photophysical Study

Electrochemical and photophysical analysis of new donoracceptor systems 2 and 3, in which a benzothiadiazole (BTD) unit is covalently linked to a tetrathiafulvalene (TTF) core, have verified that the lowest excited state can be ascribed to an intramolecular-charge-transfer (ICT) (TTF)*(benzothiadiazole) transition. Owing to better overlap of the HOMO and LUMO in the fused scaffold of compound 3, the intensity of the 1ICT band is substantially higher compared to that in compound 2. The corresponding CT fluorescence is also observed in both cases. The radical cation TTF+. is easily observed through chemical and electrochemical oxidation by performing steady-state absorption experiments. Interestingly, compound 2 is photo-oxidized under aerobic conditions.

Two-Dimensional Supramolecular Electron Spin Arrays

A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3).

Promises of cyclotron-produced 44Sc as a diagnostic match for trivalent β--emitters: in vitro and in vivo study of a 44Sc-DOTA-folate conjugate

In recent years, implementation of 68Ga-radiometalated peptides for PET imaging of cancer has attracted the attention of clinicians. Herein, we propose the use of 44Sc (half-life = 3.97 h, average β+ energy [Eβ+av] = 632 keV) as a valuable alternative to 68Ga (half-life = 68 min, Eβ+av = 830 keV) for imaging and dosimetry before 177Lu-based radionuclide therapy. The aim of the study was the preclinical evaluation of a folate conjugate labeled with cyclotron-produced 44Sc and its in vitro and in vivo comparison with the 177Lu-labeled pendant. Methods: 44Sc was produced via the 44Ca(p,n)44Sc nuclear reaction at a cyclotron (17.6 ± 1.8 MeV, 50 μA, 30 min) using an enriched 44Ca target (10 mg 44CaCO3, 97.00%). Separation from the target material was performed by a semiautomated process using extraction chromatography and cation exchange chromatography. Radiolabeling of a DOTA-folate conjugate (cm09) was performed at 95°C within 10 min. The stability of 44Sc-cm09 was tested in human plasma. 44Sc-cm09 was investigated in vitro using folate receptor–positive KB tumor cells and in vivo by PET/CT imaging of tumor-bearing mice Results: Under the given irradiation conditions, 44Sc was obtained in a maximum yield of 350 MBq at high radionuclide purity (>99%). Semiautomated isolation of 44Sc from 44Ca targets allowed formulation of up to 300 MBq of 44Sc in a volume of 200–400 μL of ammonium acetate/HCl solution (1 M, pH 3.5–4.0) within 10 min. Radiolabeling of cm09 was achieved with a radiochemical yield of greater than 96% at a specific activity of 5.2 MBq/nmol. In vitro, 44Sc-cm09 was stable in human plasma over the whole time of investigation and showed folate receptor–specific binding to KB tumor cells. PET/CT images of mice injected with 44Sc-cm09 allowed excellent visualization of tumor xenografts. Comparison of cm09 labeled with 44Sc and 177Lu revealed almost identical pharmacokinetics. Conclusion: This study presents a high-yield production and efficient separation method of 44Sc at a quality suitable for radiolabeling of DOTA-functionalized biomolecules. An in vivo proof-of-concept study using a DOTA-folate conjugate demonstrated the excellent features of 44Sc for PET imaging. Thus, 44Sc is a valid alternative to 68Ga for imaging and dosimetry before 177Lu-radionuclide tumor therapy.

Future prospects for SPECT imaging using the radiolanthanide terbium-155 — production and preclinical evaluation in tumor-bearing mice

We assessed the suitability of the radiolanthanide 155 Tb (t1/2 = 5.32 days, Eγ = 87 keV (32%), 105 keV (25%)) in combination with variable tumor targeted biomolecules using preclinical SPECT imaging. Methods 155Tb was produced at ISOLDE (CERN, Geneva, Switzerland) by high-energy (~ 1.4 GeV) proton irradiation of a tantalum target followed by ionization and on-line mass separation. 155 Tb was separated from isobar and pseudo-isobar impurities by cation exchange chromatography. Four tumor targeting molecules – a somatostatin analog (DOTATATE), a minigastrin analog (MD), a folate derivative (cm09) and an anti-L1-CAM antibody (chCE7) – were radiolabeled with 155 Tb. Imaging studies were performed in nude mice bearing AR42J, cholecystokinin-2 receptor expressing A431, KB, IGROV-1 and SKOV-3ip tumor xenografts using a dedicated small-animal SPECT/CT scanner. Results The total yield of the two-step separation process of 155 Tb was 86%. 155 Tb was obtained in a physiological l-lactate solution suitable for direct labeling processes. The 155 Tb-labeled tumor targeted biomolecules were obtained at a reasonable specific activity and high purity (> 95%). 155 Tb gave high quality, high resolution tomographic images. SPECT/CT experiments allowed excellent visualization of AR42J and CCK-2 receptor-expressing A431 tumors xenografts in mice after injection of 155 Tb-DOTATATE and 155 Tb-MD, respectively. The relatively long physical half-life of 155 Tb matched in particular the biological half-lives of 155 Tb-cm09 and 155 Tb-DTPA-chCE7 allowing SPECT imaging of KB tumors, IGROV-1 and SKOV-3ip tumors even several days after administration. Conclusions The radiolanthanide 155 Tb may be of particular interest for low-dose SPECT prior to therapy with a therapeutic match such as the β--emitting radiolanthanides 177Lu, 161 Tb, 166Ho, and the pseudo-radiolanthanide 90Y.