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Potassium perrhenate | The reduction of KReO4 in the preparation of cyclopentadienyltricarbonylrhenium complexes has potential as a model for the syntheses of technetium and rhenium organometallic radiopharmaceuticals | Buy chemicals and reagents online from Sigma Aldrich

Potassium perrhenate 99 10466-65-6

Potassium perrhenate

Minimally invasive interventional cancer therapy with drug-carrying lipid nanoparticles (ie, liposomes) via convection-enhanced delivery by an infusion pump can increase intratumoral drug concentration and retention while facilitating broad distribution throughout solid tumors. The authors investigated the utility of liposome-carrying beta-emitting radionuclides to treat head and neck cancer by direct intratumoral infusion in nude rats. Four groups of nude rats were subcutaneously inoculated with human tongue cancer cells. After tumors reached an average size of 1.6 cm(3), the treatment group received an intratumoral infusion of liposomal rhenium-186 ((186)Re) (185 MBq [5 mCi]/cm(3) tumor). Three control groups were intratumorally infused with unlabeled liposomes, unencapsulated (186)Re-perrhenate, or unencapsulated intermediate (186)Re compound ((186)Re-N,N-bis[2-mercaptoethyl]-N',N'-diethyl-ethylenediamine [BMEDA]). In vivo distribution of (186)Re activity was measured by planar gamma-camera imaging. Tumor therapy and toxicity were assessed by tumor size, body weight, and hematology. Average tumor volume in the (186)Re-liposome group on posttreatment day 14 decreased to 87.7% +/- 20.1%, whereas tumor volumes increased to 395.0%-514.4% on average in the other three groups (P< .001 vs (186)Re-liposome). The (186)Re-liposomes provided much higher intratumoral retention of (186)Re activity, resulting in an average tumor radiation absorbed dose of 526.3 Gy +/- 93.3, whereas (186)Re-perrhenate and (186)Re-BMEDA groups had only 3.3 Gy +/- 1.2 and 13.4 Gy +/- 9.2 tumor doses, respectively. No systemic toxicity was observed. Liposomal (186)Re effectively treated head and neck cancer with minimal side effects after convection-enhanced interventional delivery. These results suggest the potential of liposomal (186)Re for clinical application in interventional therapy of cancer.

Interventional therapy of head and neck cancer with lipid nanoparticle-carried rhenium 186 radionuclide.

5-Methylcytosine can be converted to 5-hydroxymethylcytosine (5hmC) in mammalian DNA by the ten-eleven translocation (TET) enzymes. We introduce oxidative bisulfite sequencing (oxBS-Seq), the first method for quantitative mapping of 5hmC in genomic DNA at single-nucleotide resolution. Selective chemical oxidation of 5hmC to 5-formylcytosine (5fC) enables bisulfite conversion of 5fC to uracil. We demonstrate the utility of oxBS-Seq to map and quantify 5hmC at CpG islands (CGIs) in mouse embryonic stem (ES) cells and identify 800 5hmC-containing CGIs that have on average 3.3% hydroxymethylation. High levels of 5hmC were found in CGIs associated with transcriptional regulators and in long interspersed nuclear elements, suggesting that these regions might undergo epigenetic reprogramming in ES cells. Our results open new questions on 5hmC dynamics and sequence-specific targeting by TETs.

Quantitative sequencing of 5-methylcytosine and 5-hydroxymethylcytosine at single-base resolution.

Configuring RE(2) O(3) nanocrystals with pseudo-2D morphologies confers substantive gains in relaxivities over equivalent spherical counterparts. The most promising arises from Gd(2) O(3) whose ionic transverse and longitudinal relaxivities were as high as r(1) = 12.7 mM(-1) s(-1) and r(2) = 17.2 mM(-1) s(-1) (dispersed in H(2) O, T = 37 °C & B(0) = 1.41 T), pointing to new opportunities to achieve high contrast MRI while concomitantly affording longer half-life potential in vivo.

Stealth rare earth oxide nanodiscs for magnetic resonance imaging.

Rhenium(V) oxo complexes of the type [ReOX(L)(2)] (1-7; X = Cl, Br) containing beta-ketiminate ligands (L = CH(3)C(O)CH(2)C(NAr)CH(3): Ar = Ph (APOH), 2-MePh (MPOH), 2,6-Me(2)Ph (DPOH), 2,6-(i)Pr(2)Ph (DiPOH)) have been prepared by reaction of [ReOX(3)(OPPh(3))(SMe(2))] (X = Cl, Br) with the lithium salts of the corresponding ligands. All compounds have been spectroscopically characterized, showing [ReOX(DiPO)(2)] (X = Cl (1), Br (5)), [ReOX(DPO)(2)] (X = Cl (2), Br (6)), and [ReOX(APO)(2)] (X = Cl (4), Br (7)) to be isomerically pure, in contrast to complex [ReOCl(MPO)(2)] (3), which exhibits a mixture of isomers. Compounds 2, 3, 5, and 7 were crystallographically characterized, showing similar octahedral coordination spheres with trans O horizontal lineRe-O and cis O horizontal lineRe-Cl bonds. However, the coordination of the nitrogen atoms vs each other is found to be cis or trans. Compounds 2 and 5 showed a trans-N,N configuration, for compound 3 both isomers (trans-N,N 3 and cis-N,N 3) were structurally characterized, and 7 gave a cis-N,N configuration. Compounds 1-6 are catalyst precursors for the epoxidation of cis-cyclooctene with 3 equiv of tert-butyl hydroperoxide (TBHP). Yields of the formed epoxide were up to 55% with all precursors, except with 2 and 6, where only up to 13% of epoxide was obtained under analogous conditions.

Oxorhenium(V) complexes with ketiminato ligands: coordination chemistry and epoxidation of cyclooctene.

The detailed syntheses of complexes of the form [Re(O)(X)(RNCH(2)CH(2))(2)N(Me)] (X = Me, Cl, I, R = mesityl, C(6)F(5)), 1-3, incorporating diamidoamine ancillary ligands are described. X-ray crystal structures for the complexes [Re(O)(Me)((C(6)F(5))NCH(2)CH(2))(2)N(Me)], 1a, [Re(O)(I)((C(6)F(5))N CH(2)CH(2))(2)N(Me)], 3a, and [Re(O)(I)((Mes)NCH(2))(2)N(Me)], 3b, are reported. The geometry about the metal center in 1a is best described as a severely distorted square pyramid with the oxo ligand in the apical position. In contrast, the geometry about the metal center in 3a is best described as a severely distorted trigonal bipyramid, with the iodo ligand occupying the apical position and the diamido nitrogens and the oxo ligand occupying the equatorial plane. The catalytic activities of these complexes for oxygen atom transfer, OAT, from pyridine-N-oxides, PyO, to PPh(3) were also examined. The reactions exhibited a clear dependence on the diamido ligand substituent and the X ligand (Me, I, Cl) attached to the metal, with the combined effect that electron-withdrawing substituents on the diamido ligand and poor sigma donors directly attached to the metal center increases the rate of catalytic activity. The kinetics of OAT from pyridine-N-oxides to Re were also investigated. The reactions displayed clean first order kinetics in Re and saturation kinetics for the dependence on PyO. Changing the PyO substrate had no effect on the saturation value, k(sat), suggesting that the OAT reaction in these five-coordinate complexes appears to be governed by isomerization of the starting complex. Attempts to isolate a postulated Re(VII) intermediate were not successful because of hydrolytic degradation. The product of hydrolytic degradation [((C(6)F(5))N(H)CH(2)CH(2)))(2)NH(Me)][X], (X = ReO(4)(-), or I(-)), 4 can be isolated, and its X-ray crystal structure is reported. Although the Re(VII) intermediate could not be isolated, its activity in OAT reactions was probed by competition experiments with PPh(3) and four para-substituted triarylphosphines (p-X-Ph)(3)P (X = OMe, Me, Cl, CF(3)). These experiments led to a Hammett that yielded a reaction constant of rho = -0.30 +/- 0.01. This data suggests a positive charge buildup on phosphorus for the OAT reaction and is consistent with the nucleophilic attack of phosphorus on an electrophilic metal oxo.

Synthesis of oxorhenium(V) complexes with diamido amine ancillary ligands and their role in oxygen atom transfer catalysis.

The use of an inorganic perrhenate ligand in the structure of early-transition-metal alkoxide precursors permits to achieve uniform self-assembly of the primary nanoparticles produced by their hydrolysis. The latter has been carried out in a hydrocarbon reaction medium by the addition of water with vigorous stirring, either in the pure form or in solutions in parent alcohols. The self-assembly is guided by the surface charge enhanced by the presence of strongly coordinated anions as determined by zeta potential measurements. The aggregation process has been followed in real time by nanoparticle tracking analysis (NanoSight technique). The reaction products are spherical aggregates with a size that can be efficiently controlled through the polarity of the reaction medium. The produced nanobeads have been characterized by TEM, SEM-EDS, DLS, nitrogen adsorption, and FTIR. The coordination of metal centers has been investigated using EXAFS spectroscopy. The aggregates remain amorphous on thermal treatment of up to 700 °C (24 h treatment) but crystallize when treated at 1000 °C. This latter process is associated with the total loss of rhenium content and offers early-transition-metal oxides as products.

Precursor-directed assembly of complex oxide nanobeads: the role of strongly coordinated inorganic anions.

Radiolabeled biomolecules are routinely used for clinical diagnostics. (99m)Tc is the most commonly used radioactive tracer in radiopharmaceuticals. (188)Re and (186)Re are also commonly used as radioactive tracers in medicine. However, currently available methods for radiolabeling are lengthy and involve several steps in bioconjugation processes. In this work we present a strategy to engineer proteins that may selectively recognize the perrhenate (ReO(4)(-)) ion as a new way to label proteins. We found that a molybdate (MoO(4)(2-))-binding protein (ModA) from Escherichia coli can bind perrhenate with high affinity. Using fluorescence and isothermal titration calorimetry measurements, we determined the dissociation constant of ModA for ReO(4)(-) to be 541 nM and we solved a crystal structure of ModA with a bound ReO(4)(-). On the basis of the structure we created a mutant protein containing a disulfide linkage, which exhibited increased affinity for perrhenate (K(d) = 104 nM). High-resolution crystal structures of ModA (1.7 Å) and A11C/R153C mutant (2.0 Å) were solved with bound perrhenate. Both structures show that a perrhenate ion occupies the molybdate binding site using the same amino acid residues that are involved in molybdate binding. The overall structure of the perrhenate-bound ModA is unchanged compared with that of the molybdate-bound form. In the mutant protein, the bound perrhenate is further stabilized by the engineered disulfide bond.

Binding of ReO4(-) with an engineered MoO4(2-)-binding protein: towards a new approach in radiopharmaceutical applications.

We describe a multidentate tripodal ligand in which three pendant arms carrying di(2-picolyl)amine units are linked to the ortho positions of a tris(o-xylyl) scaffold, providing N(CH(2)-o-C(6)H(4)CH(2)N(CH(2)py)(2))(3) (L). Reaction of L with CuCl(2) in the presence of hexafluorophosphate anion afforded blue cubes of [(CuCl)(3)L](PF(6))(3)·5H(2)O (1). Crystallographic studies of 1 revealed that the three symmetry-related arms each coordinate a {Cu(II)Cl} unit, and two molecules of 1 are connected to one another through a Cu(μ-Cl)(2)Cu bridge, extending the molecular structure to form a two-dimensional (2-D) layer. These 2-D layers pack in an ABCABC... fashion with PF(6)(-) anions located in between. Reaction of 1 with a stoichiometric amount of perrhenate ion afforded blue plates of [(CuCl)(3)L](PF(6))(ReO(4))(2)·3H(2)O (2). Compound 2 has the same lattice structure as 1, but the tricopper unit backbone now traps one ReO(4)(-) anion through Coulombic interactions. In addition, three molecules of 2 are bridged by a perrhenate ion, forming a Cu(3)(μ(3)-ReO(4)) cluster, to give a different 2-D structure displaying a rare tridentate bridging ReO(4)(-) mode. Thus, in addition to classic perrhenate trapping through weak Coulombic interactions, 2 represents an exceptional example in which the ReO(4)(-) anion is immobilized in an extended framework through tight covalent interactions. The interlamellar PF(6)(-) anions in 1 can be exchanged with other anions including perrhenate, perchlorate, or periodate. The structural similarity between perrhenate and pertechnetate makes these materials of potential interest for pertechnetate trapping.

Immobilization, trapping, and anion exchange of perrhenate ion using copper-based tripodal complexes.

New sequencing technique produces high-resolution map of 5-hydroxymethylcytosine.

Accumulation of iodide and other substrates via the human sodium/iodide symporter (hNIS) is fundamental to imaging and therapy of thyroid disease, hNIS reporter gene imaging and hNIS-mediated gene therapy. There is no readily available positron emission tomography (PET) tracer for hNIS. Our aim was to develop a colon carcinoma cell line stably expressing hNIS, and use it to evaluate a novel hNIS PET tracer, [18F]-tetrafluoroborate. Colon carcinoma cell line, HCT116, was stably transfected with hNIS, thus producing a cell line, HCT116-C19, with high hNIS expression. A Fisher rat thyroid cell line, FRTL5, which expresses rat sodium/iodide symporter when stimulated with thyroid-stimulating hormone, was used for comparison. Accumulation of [188Re]-perrhenate, [99mTc]-pertechnetate and [18F]-tetrafluoroborate was evaluated with and without perchlorate inhibition using an automated radioimmune assay system, LigandTracer. The affinity of [18F]-tetrafluoroborate for hNIS, and its half-maximal inhibitory concentration (IC50) for the inhibition of [99mTc]-pertechnetate transport were determined from the plateau accumulation of [18F]-tetrafluoroborate and [99mTc]-pertechnetate, respectively, as a function of tetrafluoroborate concentration. [18F]-tetrafluoroborate accumulated effectively in both FRTL5 and HCT116-C19 cells. The accumulation in HCT116-C19 cells (plateau accumulation 31%) was comparable to that of [188Re]-perrhenate (41%) and [99mTc]-pertechnetate (46%). Its affinity for hNIS and half-maximal inhibitory concentration (IC50) for the inhibition of pertechnetate uptake was approximately micromolar. We have produced a human colon cell line with a stable constitutive expression of functional hNIS (HCT116-hNIS-C19). [18F]-tetrafluoroborate accumulates in cells expressing hNIS or rat sodium/iodide symporter and is a potential PET imaging agent in thyroid disease and hNIS reporter gene imaging.

Evaluation of [18F]-tetrafluoroborate as a potential PET imaging agent for the human sodium/iodide symporter in a new colon carcinoma cell line, HCT116, expressing hNIS.

Assembly of independent chemical modules through oxorhenium coordination by a NS(2)+S chelation motif was applied to the synthesis of RGD (Arg-Gly-Asp) analogs. Modules were assembled through oxorhenium chelation to give a series of 18 metal complexes in good yields and satisfactory purities. Screening of these oxorhenium coordinates as antagonists of integrins αVβ3, αIIbβ3 and αVβ5 led to the identification of 3 bioactive compounds that exhibit submicromolar affinities for the 3 integrins. Preliminary studies showed that the corresponding oxotechnetium complexes are stable in mice plasma and therefore could be proposed for the molecular imaging of pathologies that overexpress integrins αVβ3 and αVβ5.

Chelate oxorhenium to assemble new integrin antagonists.

The design and synthesis of a neutral macrocyclic host that is capable of perrhenate and pertechnetate recognition is described. The anion affinities and underlying coordination modes were estimated by several experimental and theoretical methods including a new technique--reverse (99)Tc NMR titration.

Macrocyclic receptor for pertechnetate and perrhenate anions.

The goal of this study is to design new (99m)Tc-radiolabelled shortened CCK derivatives that might be suitable for the molecular imaging of cholecystokinin-2 receptors (CCK2-R), these receptors being over-expressed in a number of neuroendocrine tumors such as medullary thyroid cancer and small-cell lung cancer. For this purpose, we designed several modified CCK4 analogs bearing an ON(2)S tetradentate chelating agent at the N-terminus, the CCK4 sequence representing the minimal peptide sequence that presents nanomolar affinity and activity towards the CCK2-R. Four peptide conjugates of general formula (Trt)SN(2)OPh-(X)(n)-CCK4 (X=beta-alanine or 6-aminohexanoic acid spacers; n=0, 2, 4) and their oxorhenium peptide conjugates have been synthesized and characterized. In vitro evaluation of these compounds showed a close relationship between the nature and the length of the spacer and the corresponding binding affinity values. The most promising oxorhenium complex 5-Re exhibited potent CCK2-receptor agonist properties in promoting the production of inositol phosphate in COS-7 cells (EC(50)=5.17nM). Preliminary (99m)Tc-radiolabelling studies with peptide conjugates 3 or 5 led exclusively to the corresponding (99m)TcO-complexes 3-Tc and 5-Tc, which exhibited high resistance towards an excess of cysteine and satisfactory stabilities in human serum. To conclude, the promising in vitro characteristics of compounds 5-Re, 5-Tc illustrate the feasibility to develop stable radiolabelled shortened CCK4 derivatives with a nanomolar CCK2-R affinity.

Synthesis, characterization and in vitro evaluation of new oxorhenium- and oxotechnetium-CCK4 derivatives as molecular imaging agents for CCK2-receptor targeting.

A novel 6-(2-pyridinyl)-5,6-dihydrobenzimidazo[1,2-c]quinazoline (HL) serves as a first-time highly selective and sensitive ratiometric fluorescent chemosensor probe for oxorhenium (ReO(V)) ion in acetonitrile : water = 9 : 1 (v/v) at 25 °C. The decrease in fluorescence at 410 nm and increase in fluorescence at 478 nm with an isoemissive point at 444 nm in the presence of ReO(V) ion is accounted for by the formation of mononuclear [ReOL(2)Cl] complex, characterized by physico-chemical and spectroscopic tools. The fluorescence quantum yield of the chemosensor (HL) was only 0.198 at 410 nm, and it increased more than 3-fold in the presence of 2 equiv. of the ReO(V) ion at 478 nm. Interestingly, the introduction of other metal ions and relevant anions caused the fluorescence intensity at 478 nm to be either unchanged or weakened. The fluorescence-response fits a Hill coefficient of 2.088 indicates the formation of a 1 : 2 stoichiometry for the L-ReO(V) complex. In the concentration range of 0-20 μM of oxorhenium(V) species calibration graph was linear with correlation coefficient (R) of 0.99994 and the calibration sensitivity was found to be 4.0 × 10(-7) M. The cellular image in the confocal microscope clearly indicated the presence of ReO(V) in Candida albicans cells using this chemosensor (HL).

Development of a highly selective cell-permeable ratiometric fluorescent chemosensor for oxorhenium(V) ion.

Despite the wide-ranging applications of binary Rh and Ir oxides, their stability and trends in Rh and Ir oxidation states are not fully understood. Using first-principles electronic structure calculations, we demonstrate that the origin of the categorical stability of Ir(4+) is the relativistic contraction of the 6s orbital and, consequently, an expansion of 5d orbitals. Relativistic effects significantly stabilize Ir(4+)-containing metallic rutile IrO(2) over a wide range of O chemical potentials, despite the choice that Ir has of forming semiconducting corundum Ir(2)O(3). In contrast, Rh is found to display a wider stability range for corundum Rh(2)O(3) with Rh(3+) and a greater propensity for multiple oxidation states.

Rh2O3 versus IrO2: relativistic effects and the stability of Ir4+.

The hydrogenolysis of erythritol using an Ir-ReO(x)/SiO(2) catalyst was performed for the production of butanediols, which are widely used as a raw material of polymers. The activity and selectivity to butanediols on Ir-ReO(x)/SiO(2) was much higher than that on conventional hydrogenolysis catalysts. The maximum selectivity to 1,4- and 1,3-butanediols reached 33 and 12 % at 74 % conversion, respectively. The erythritol conversion and selectivity to butanediols was almost maintained during four repeating tests if small amounts of acid were added to the reaction and the catalyst was calcined again. The reaction kinetics, reactivity trends, and characterization results indicate a direct hydrogenolysis mechanism in which the hydride species on the Ir metal surface attacks the alkoxide species on the 3D ReO(x) clusters. Based on the production of erythritol by the fermentation of glucose and glycerol, erythritol hydrogenolysis may be a promising pathway for the production of biobutanediols.

Production of biobutanediols by the hydrogenolysis of erythritol.

Heterogeneous Re/SiO(2) catalysts prepared using a one pot sol-gel synthesis were found to display high activity in the direct, selective methanol conversion to methylal, which is correlated to an unprecedented rhenium oxide structure.

An easily accessible Re-based catalyst for the selective conversion of methanol: evidence for an unprecedented active site structure through combined operando techniques.

Heterometallic cerium(IV) perrhenate, permanganate, and molybdate complexes containing the imidodiphosphinate ligand [N(i-Pr2PO)2](-) have been synthesized, and their reactivity was investigated. Treatment of Ce[N(i-Pr2PO)2]3Cl (1) with AgMO4 (M = Re, Mn) afforded Ce[N(i-Pr2PO)2]3(ReO4) (2) or Ce2[N(i-Pr2PO)2]6(MnO4)2 (3). In the solid state, 3 is composed of a [Ce2{N(i-Pr2PO)2}6(MnO4)](+) moiety featuring a weak Ce-OMn interaction [Ce-OMn distance = 2.528(8) Å] and a noncoordinating MnO4(-) counteranion. While 3 is stable in the solid state and acetonitrile solution, it decomposes readily in other organic solvents, such as CH2Cl2. 3 can oxidize ethylbenzene to acetophenone at room temperature. Treatment of 1 with AgBF4, followed by reaction with [n-Bu4N]2[MoO4], afforded [Ce{N(i-Pr2PO)2}3]2(μ-MoO4) (4). Reaction of trans-Ce[N(i-Pr2PO)2]2(NO3)2 (5), which was prepared from (NH4)2Ce(NO3)6 and K[N(i-Pr2PO)2], with 2 equiv of [n-Bu4N][Cp*MoO3] yielded trans-Ce[N(i-Pr2PO)2]2(Cp*MoO3)2 (6). 4 can catalyze the oxidation of methyl phenyl sulfide with tert-butyl hydroperoxide with high selectivity. The crystal structures of complexes 3-6 have been determined.

Heterometallic cerium(IV) perrhenate, permanganate, and molybdate complexes supported by the imidodiphosphinate ligand [N(i-Pr2PO)2]-.

The dynamic combinatorial assembly of libraries of modular cyclophilin hCyp18 oxorhenium inhibitors of general formula [A˙ReO˙B] was accelerated by addition of increasing concentrations of hCyp18 ('Cyclophilin Enhancing Effect', CEE). This result suggested that modules assembly might proceed through an in situ coordination chemistry process. However, we observed that the CEE was not strictly related to the affinity of the complexes for hCyp18. The CEE was not altered by cyclosporine A, a potent competitive inhibitor of hCyp18. The use of a non-degassed buffer caused a fall in complexation yields that could be reversed upon addition of hCyp18. All these data suggested that the CEE results from a partial protection of exogenous thiols against reoxidation. As anticipated, carbamido-methylation of cyclophilin Cys52 and Cys62 residues with iodoacetamide annihilated the CEE. All these results highlight the role of hCyp18 in maintaining chemical modules in a reduced state.

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