Palladium-catalyzed selective B(3)-H arylation of o-carboranes with arylboronic acids at room temperature

A palladium-catalyzed selective B(3)-H arylation of o-carboranes at room temperature has been developed using readily available arylboronic acids as the aryl source, and the corresponding 3-aryl-o-carboranes were obtained in good to excellent yields. This method provides a powerful synthetic route for constructing polysubstituted o-carborane derivatives.

Bioconjugated technetium carbonyls by transmetalation reaction with zinc derivatives

The transmetalation reaction between zinc dithiocarbamates functionalized with organic groups and the cation fac-[^99mTc(H₂O)₃(CO)₃]⁺ has been studied as a new strategy to bind biomolecules to this radionuclide for preparing radiopharmaceuticals with high molar activity. All complexes were obtained in high yields by heating at moderate temperatures and without subsequent purification. The chemical identity was ascertained by HPLC comparison with the homologous rhenium complexes. Stability studies in cysteine solution and serum have shown a good stability of the coordination set fac-[^99mTc(CO)₃(SS)(P)]. Preliminary biological studies of the radiocomplex functionalized with D-(+)-glucosamine with carcinoma cells have been performed.

Neutral Rhenadicarbaboranes with Re(CO)2(NO) Vertices: A Theoretical Study of Building Blocks for Rhenacarborane-Based Drug Delivery Agents

The rhenadicarbaborane carbonyl nitrosyls (C₂B_n−3H_n−1)Re(CO)₂(NO), (n = 8 to 12), of interest in drug delivery agents based on the experimentally known C₂B₉H₁₁Re(CO)₂(NO) and related species, have been investigated by density functional theory. The lowest energy structures of these rhenadicarbaboranes are all found to have central ReC₂B_n−3 most spherical closo deltahedra in accord with their 2n + 2 Wadean skeletal electrons. Carbon atoms are found to be located preferentially at degree 4 vertices in such structures. Furthermore, rhenium atoms are preferentially located at a highest degree vertex, typically a vertex of degree 5. Only for the 9-vertex C₂B₆H₈Re(CO)₂(NO) system are alternative isocloso deltahedral isomers found within ~8 kcal/mol of the lowest energy closo isomer. Such 9-vertex isocloso structures provide a degree 6 vertex for the rhenium atom flanked by degree 4 vertices for each carbon atom.

Transition-metal-free direct nucleophilic substitution of carboranyllithium and 2-halopyridines

A practical and efficient C(cage)-heteroarylation of carborane is presented, via direct nucleophilic substitution of carboranyllithium with 2-halopyridines. This reaction does not need the aid of any transition metal and utilizes readily available carboranyllithium nucleophiles, thereby avoiding transmetalation of carboranyllithium. The process exhibits a broad scope, and a vast array of 2-halopyridines have proven to be suitable substrates. The method serves as a complement to C(cage)-arylation reactions and may find wide applications in materials science and medicinal and coordination chemistry.

Thermal rearrangement mechanisms in icosahedral carboranes and metallocarboranes

Ab initio MD and potential energy surface sampling has been used to study the rearrangement processes in carboranes and their derivatives. A new mechanism is found, in addition to those previously proposed. The fact that theoretical activation energies are lower than those observed experimentally, and the differing activity of technetium and rhenium complexes, are rationalised by orbital symmetry constraints.

Rhenium solubility in borosilicate nuclear waste glass: implications for the processing and immobilization of technetium-99

The immobilization of technetium-99 ((99)Tc) in a suitable host matrix has proven to be a challenging task for researchers in the nuclear waste community around the world. In this context, the present work reports on the solubility and retention of rhenium, a nonradioactive surrogate for (99)Tc, in a sodium borosilicate glass. Glasses containing target Re concentrations from 0 to 10,000 ppm [by mass, added as KReO(4) (Re(7+))] were synthesized in vacuum-sealed quartz ampules to minimize the loss of Re from volatilization during melting at 1000 °C. The rhenium was found as Re(7+) in all of the glasses as observed by X-ray absorption near-edge structure. The solubility of Re in borosilicate glasses was determined to be ~3000 ppm (by mass) using inductively coupled plasma optical emission spectroscopy. At higher rhenium concentrations, additional rhenium was retained in the glasses as crystalline inclusions of alkali perrhenates detected with X-ray diffraction. Since (99)Tc concentrations in a glass waste form are predicted to be <10 ppm (by mass), these Re results implied that the solubility should not be a limiting factor in processing radioactive wastes, assuming Tc as Tc(7+) and similarities between Re(7+) and Tc(7+) behavior in this glass system.

Inorganic chemistry in nuclear imaging and radiotherapy: current and future directions

Radiometals play an important role in diagnostic and therapeutic radiopharmaceuticals. This field of radiochemistry is multidisciplinary, involving radiometal production, separation of the radiometal from its target, chelate design for complexing the radiometal in a biologically stable environment, specific targeting of the radiometal to its in vivo site, and nuclear imaging and/or radiotherapy applications of the resultant radiopharmaceutical. The critical importance of inorganic chemistry in the design and application of radiometal-containing imaging and therapy agents is described from a historical perspective to future directions.

Multimodal radio- (PET/SPECT) and fluorescence imaging agents based on metallo-radioisotopes: current applications and prospects for development of new agents

This perspective focuses on complexes of radioactive metal ions applied in multimodal radio- and optical imaging. The application of metal ions in radioimaging techniques such as Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) has advantages over lighter nuclei in terms of half-life, but there are particular issues related to their speciation (particularly leaching from complexes) and with the combination of certain ions with fluorescent systems. The basic coordination chemistry of the ions involved and issues relating to biological conditions and their compatibility with optical imaging techniques are reviewed, the current literature presented in context, and the prospect of exploiting the intrinsic luminescence of certain metal-ligand complexes is discussed.