A novel organotellurium compound (RT-01) as a new antileishmanial agent

Synthesis and application of organotellurium compounds

Organotellurium compounds define the compounds containing carbon (organic group) and tellurium bond (C–Te). The first organic compound containing tellurium was prepared by Wohler in 1840 after the discovery of the metal by the Austrian chemist F. J. Muller von Reichenstein in the year 1782. The term tellurium was derived from Latin tellus. Tellurium was observed first time in ores mined in the gold districts of Transylvania. Naturally occurring tellurium compounds are present in various forms based on their oxidation states such as TeO2 (+4) and TeO3 (+6). These oxidation states of tellurium compounds are more stable as compared to the other oxidation states. Tellurium is a rare element and is considered a non-essential, toxic element. Tellurium possesses only one crystalline form which consists of a network of spiral chains similar to that of hexagonal selenium. Tellurium is used for the treatment and prevention of microbial infections prior to the development of antibiotics. Hence, the utilization of organotellurium compounds plays a significant role as reagents and intermediates in various organic syntheses.

Synthesis of Tellurium Oxide (TeO2) Nanorods and Nanoflakes and Evaluation of Its Efficacy Against Leishmania major In Vitro and In Vivo

PURPOSE

Today, the use of natural products and nanostructures has increased. Given the reports on beneficial effects of various organotellurane compounds on types of visceral leishmaniasis, we decided to investigate the effect of TeO₂ NPs on Leishmania major (L. major). Tellurium can cause cell apoptosis in cancer cells without activating the caspase-pathway.

METHODS

TeO₂ NPs at first synthesized and the structure was checked by XRD, SEM and EDS tests. The cytotoxic effect of TeO₂ NPs against L. major promastigotes, amastigotes and macrophages was assessed by MTT test or counting. The possible apoptosis of L. major by TeO₂ NPs was evaluated by flow cytometry test. For in vivo assay, the lesions of infected BALB/c mice with L. major promastigotes were treated with TeO₂ NPs, then the lesion size and survival rate were evaluated.

RESULTS

The synthesis of TeO₂ with tetragonal structure was confirmed by XRD. The combination of nanorods and nanoflakes and the presence of Te were proven by SEM and EDS, respectively. According the effects of nanoparticle on promastigotes and amastigotes, the IC₅₀ values of TeO₂ after 72 h of incubation were 15.13 and 52.22 µg/ml, respectively. TeO₂ NPs induced apoptosis in about 41% of promastigotes. The ulcer greatly healed and survival rate was higher in treated mice compared to those in control group.

CONCLUSION

Based on the data, favorable anti-leishmanial properties were observed by using TeO₂ NPs. TeO₂ NPs have cytotoxic impacts on L. major promastigotes and amastigotes in vitro and in vivo and may be regarded as a therapy option.

Synthesis, Mechanism Elucidation and Biological Insights of Tellurium(IV)-Containing Heterocycles

Inspired by the synthetic and biological potential of organotellurium substances, a series of five- and six-membered ring organotelluranes containing a Te-O bond were synthesized and characterized. Theoretical calculations elucidated the mechanism for the oxidation-cyclization processes involved in the formation of the heterocycles, consistent with chlorine transfer to hydroxy telluride, followed by a cyclization step with simultaneous formation of the new Te-O bond and deprotonation of the OH group. Moreover, theoretical calculations also indicated anti-diastereoisomers to be major products for two chirality center-containing compounds. Antileishmanial assays against Leishmania amazonensis promastigotes disclosed 1,2λ⁴ -oxatellurane LQ50 (IC₅₀ =4.1±1.0; SI=12), 1,2λ⁴ -oxatellurolane LQ04 (IC₅₀ =7.0±1.3; SI=7) and 1,2λ⁴ -benzoxatellurole LQ56 (IC₅₀ =5.7±0.3; SI=6) as more powerful and more selective compounds than the reference, being up to four times more active. A stability study supported by ¹²⁵ Te NMR analyses showed that these heterocycles do not suffer structural modifications in aqueous-organic media or at temperatures up to 65 °C.

Equilibrium between tri- and tetra-coordinate chalcogenuranes is critical for cysteine protease inhibition

There have been significant advances in the biological use of hypervalent selenium and tellurium compounds as cysteine protease inhibitors. However, the full understanding of their reaction mechanisms for and cysteine proteases inhibition is still elusive. Kinetic studies suggest an irreversible inhibition mechanism, which was explained by forming a covalent bond between the enzyme sulfhydryl group and the chalcogen atom at its hypervalent state (+4). In this work, we performed a theoretical investigation using density functional theory to propose the active inhibitor form in an aqueous solution. To this end, we investigated chloride ligand exchange reactions by oxygen and sulfur nucleophiles on hypervalent selenium and tellurium compounds. All tetra- and tri-coordinated chalcogen compounds and distinct protonation states of the nucleophiles were considered, totaling 34 unique species, 7 nucleophiles, and 155 free energies reactions. We discovered that chloride is easily replaced by a nonprotonated nucleophile (SH^- or OH^- ) in R₂ SeCl₂ . We also found that tri-coordinate species are more stable than their tetra-coordinate counterparts, with selenoxide (R₂ SeO) protonation being strongly exergonic in acid pH. The thermodynamic and kinetic results suggest that the protonated selenoxide (R₂ SeOH⁺ ) is the most probable active chemical species in biological media. The computed energetic profiles paint a possible picture for selenuranes activity, with successive exergonic steps leading to a covalent inhibition of thiol-dependent enzymes, like cysteine proteases. A second pathway has also been uncovered, with a direct reaction to chalcogenonium cation (R₂ SeCl⁺ ) as the inhibition step. Tellurium compounds showed similar trends but formed telluroxide in a pH-independent fashion.

preADMET analysis and clinical aspects of dogs treated with the Organotellurium compound RF07: A possible control for canine visceral leishmaniasis?

Tellurium compounds have been described as potential leishmanicides, bearing promising leishmanicidal and antimalarial effects. Therefore, the present study investigated the pharmacological potential of the organotellurane compound RF07 through preADMET parameters, such as absorption, distribution, metabolism and excretion. After studying the pharmacokinetic properties of RF07, studies were carried out on dogs naturally infected with visceral leishmaniasis after the administration of RF07, in order to assess pathophysiological parameters. Thus, dogs were divided into 4 groups with administration of daily intraperitoneal injections for 3 weeks (containing RF07 or placebo). During the trial, hematological parameters, renal and hepatic toxicity were evaluated. Serum urea, creatinine, alkaline phosphatase, transaminases (GOT and GPT), as well as hemogram results, were evaluated before the first administration and during the second and third weeks after the start of the treatment. In dogs with VL, RF07 improved liver damage, regulated GPT levels and significantly decreased leukocyte count, promoting its regularization. These phenomena occurred at the end of the third week of treatment. The administration of RF07 promoted a significant decrease in the average levels of GOT and GPT after the third week of treatment and did not significantly alter the hematological parameters. The application of RF07 in the treatment of visceral leishmaniasis suggests that it is an alternative to the disease, since the reversal of clinical signs in dogs with VL requires the use of 0.6 mg/kg.

Tellurides Bearing Sulfonamides as Novel Inhibitors of Leishmanial Carbonic Anhydrase with Potent Antileishmanial Activity

We report for the first time a novel series of tellurides bearing sulfonamide as selective and potent inhibitors of the β-class carbonic anhydrase (CA; EC 4.2.1.1) enzyme expressed in Leishmania donovani protozoa. Such derivatives showed high activity against axenic amastigotes, and among them, compound 5g (4-(((3,4,5-trimethoxyphenyl)tellanyl)methyl)benzenesulfonamide) showed an IC₅₀ of 0.02 μM being highly selective for the parasites over THP-1 cells with a selectivity index of 300. The in vitro and in vivo toxicity experiments showed compound 5g to possess a safe profile and thus paving the way for tellurium-containing compounds as novel drug entities.

Antitumor effect of chiral organotelluranes elicited in a murine melanoma model

Protease roles in cancer progression have been demonstrated and their inhibitors display antitumor effects. Cathepsins are lysosomal cysteine proteases that have increased expression in tumor cells, and tellurium compounds were described as potent cysteine protease inhibitors and also assayed in several animal models. In this work, the two enantiomeric forms of 1-[Butyl(dichloro)-λ⁴-tellanyl]-2-[1S-methoxyethyl]benzene (organotelluranes RF-13R and RF-13S) were evaluated as inhibitors of cathepsins B and L, showing significant enantiodiscrimination. We observed their cytotoxic effects on a murine melanoma model, effectively inhibiting tumor progression in vivo. The enantiomers were able to inhibit melanoma cell viability, migration and invasion in vitro. Besides, RF-13S and RF-13R were able to inhibit endothelial cell angiogenesis using a tube formation assay in vitro, in a stereodependent manner. These organotelluranes affected cell morphology, showing disassembling of the actin cytoskeleton. These results suggest organotelluranes as potential antitumor agents, acting directly on tumor cell proliferation, migration and invasion, and on endothelial cells, disrupting angiogenesis, showing low toxicity and high efficiency. Taken together our results suggest that this class of compounds should be further studied to reveal their potential as antitumoral agents.

Diacetal Ditellurides as Highly Active and Selective Antiparasitic Agents toward Leishmania amazonensis

Leishmaniasis is a neglected tropical disease and a public health concern in at least 98 countries, affecting mainly the poorest populations. Pharmaceuticals and chemotherapies available for leishmaniasis treatment have several limitations, which clearly justify the efforts to find new potential antileishmanial drugs. In this context, antiprotozoal activities toward different Leishmania species have been reported for hypervalent tellurium compounds, which motivated us to investigate, for the first time, the leishmanicidal properties of some nonhypervalent diaryl ditellurides. Thus, this work describes in vitro activity against Leishmania amazonensis and the cytotoxicities of diaryl ditellurides. Ditelluride LQ7 revealed a strong leishmanicidal activity on promastigotes and amastigotes at submicromolar levels (IC50 = 0.9 ± 0.1 and 0.5 ± 0.1 μmol L-1, respectively) and presented selectivity indexes greater than those of reference drug miltefosine. This preliminary study suggests that diaryl ditellurides may be promising scaffolds for the development of new agents for leishmaniasis treatment.

Cysteine proteases in protozoan parasites

Cysteine proteases (CPs) play key roles in the pathogenesis of protozoan parasites, including cell/tissue penetration, hydrolysis of host or parasite proteins, autophagy, and evasion or modulation of the host immune response, making them attractive chemotherapeutic and vaccine targets. This review highlights current knowledge on clan CA cysteine proteases, the best-characterized group of cysteine proteases, from 7 protozoan organisms causing human diseases with significant impact: Entamoeba histolytica, Leishmania species (sp.), Trypanosoma brucei, T. cruzi, Cryptosporidium sp., Plasmodium sp., and Toxoplasma gondii. Clan CA proteases from three organisms (T. brucei, T. cruzi, and Plasmodium sp.) are well characterized as druggable targets based on in vitro and in vivo models. A number of candidate inhibitors are under development. CPs from these organisms and from other protozoan parasites should be further characterized to improve our understanding of their biological functions and identify novel targets for chemotherapy.

Ammonium trichloro [1,2-ethanediolato-O,O']-tellurate cures experimental visceral leishmaniasis by redox modulation of Leishmania donovani trypanothione reductase and inhibiting host integrin linked PI3K/Akt pathway

In an endeavor to search for affordable and safer therapeutics against debilitating visceral leishmaniasis, we examined antileishmanial potential of ammonium trichloro [1,2-ethanediolato-O,O']-tellurate (AS101); a tellurium based non toxic immunomodulator. AS101 showed significant in vitro efficacy against both Leishmania donovani promastigotes and amastigotes at sub-micromolar concentrations. AS101 could also completely eliminate organ parasite load from L. donovani infected Balb/c mice along with significant efficacy against infected hamsters (˃93% inhibition). Analyzing mechanistic details revealed that the double edged AS101 could directly induce apoptosis in promastigotes along with indirectly activating host by reversing T-cell anergy to protective Th1 mode, increased ROS generation and anti-leishmanial IgG production. AS101 could inhibit IL-10/STAT3 pathway in L. donovani infected macrophages via blocking α4β7 integrin dependent PI3K/Akt signaling and activate host MAPKs and NF-κB for Th1 response. In silico docking and biochemical assays revealed AS101's affinity to form thiol bond with cysteine residues of trypanothione reductase in Leishmania promastigotes leading to its inactivation and inducing ROS-mediated apoptosis of the parasite via increased Ca2+ level, loss of ATP and mitochondrial membrane potential along with metacaspase activation. Our findings provide the first evidence for the mechanism of action of AS101 with excellent safety profile and suggest its promising therapeutic potential against experimental visceral leishmaniasis.

Resuspendable Powders of Lyophilized Chalcogen Particles with Activity against Microorganisms

Many organic sulfur, selenium and tellurium compounds show considerable activity against microorganisms, including bacteria and fungi. This pronounced activity is often due to the specific, oxidizing redox behavior of the chalcogen-chalcogen bond present in such molecules. Interestingly, similar chalcogen-chalcogen motifs are also found in the elemental forms of these elements, and while those materials are insoluble in aqueous media, it has recently been possible to unlock their biological activities using naturally produced or homogenized suspensions of respective chalcogen nanoparticles. Those suspensions can be employed readily and often effectively against common pathogenic microorganisms, still their practical uses are limited as such suspensions are difficult to transport, store and apply. Using mannitol as stabilizer, it is now possible to lyophilize such suspensions to produce solid forms of the nanoparticles, which upon resuspension in water essentially retain their initial size and exhibit considerable biological activity. The sequence of Nanosizing, Lyophilization and Resuspension (NaLyRe) eventually provides access to a range of lyophilized materials which may be considered as easy-to-handle, ready-to-use and at the same time as bioavailable, active forms of otherwise insoluble or sparingly substances. In the case of elemental sulfur, selenium and tellurium, this approach promises wider practical applications, for instance in the medical or agricultural arena.

Stability Study of Hypervalent Tellurium Compounds in Aqueous Solutions

Hypervalent tellurium compounds (telluranes) are promising therapeutical agents with negligible toxicities for some diseases in animal models. The C-Te bond of organotellurium compounds is commonly considered unstable, disfavoring their applicability in biological studies. In this study, the stability of a set of telluranes composed of an inorganic derivative and noncharged and charged organic derivatives was monitored in aqueous media with ¹H, ¹³C, and ¹²⁵Te NMR spectroscopy and high-resolution mass spectrometry. Organic telluranes were found to be remarkably resistant and stable to hydrolysis, whereas the inorganic tellurane AS101 is totally converted to the hydrolysis product, trichlorooxytellurate, [TeOCl ₃ ]^-, which was also observed in the hydrolysis of TeCl ₄ . The noteworthy stability of organotelluranes in aqueous media makes them prone to further structure-activity relationship studies and to be considered for broad biological investigations.

Glucose-6-phosphate dehydrogenase and Trypanothione reductase interaction protects Leishmania donovani from metalloid mediated oxidative stress

Exploration of metabolons as viable drug target is rare in kinetoplastid biology. Here we present a novel protein-protein interaction among Glucose-6-phosphate dehydrogenase (LdG6PDH) and Trypanothione reductase (LdTryR) of Leishmania donovani displaying interconnection between central glucose metabolism and thiol metabolism of this parasite. Digitonin fractionation patterns observed through immunoblotting indicated localisation of both LdG6PDH and LdTryR in cytosol. In-silico and in-vitro interaction observed by size exclusion chromatography, co-purification, pull-down assay and spectrofluorimetric analysis revealed LdG6PDH and LdTryR physically interact with each other in a NADPH dependent manner. Coupled enzymatic assay displayed that NADPH generation was severely impaired by addition of Sb^III, As^III and Te^IV extraneously, which hint towards metalloid driven structural changes of the interacting proteins. Co-purification patterns and pull-down assays also depicted that metalloids (Sb^III, As^III and Te^IV) hinder the in-vitro interaction of these two enzymes. Surprisingly, metalloids at sub-lethal concentrations induced the in-vivo interaction of LdG6PDH and LdTryR, as analyzed by pull-down assays and fluorescence microscopy signifying protection against metalloid mediated ROS. Inhibition of LdTryR by thioridazine in LdG6PDH^-/- parasites resulted in metalloid induced apoptotic death of the parasites due to abrupt fall in reduced thiol content, disrupted NADPH/NADP⁺ homeostasis and lethal oxidative stress. Interestingly, clinical isolates of L.donovani resistant to SAG exhibited enhanced interaction between LdG6PDH and LdTryR and showed cross resistivity towards As^III and Te^IV. Thus, our findings propose the metabolon of LdG6PDH and LdTryR as an alternate therapeutic target and provide mechanistic insight about metalloid resistance in Visceral Leishmaniasis.

The Anticancer Activity of Organotelluranes: Potential Role in Integrin Inactivation

Organic Te(IV) compounds (organotelluranes) differing in their labile ligands exhibited anti-integrin activities in vitro and anti-metastatic properties in vivo. They underwent ligand substitution with l-cysteine, as a thiol model compound. Unlike inorganic Te(IV) compounds, the organotelluranes did not form a stable complex with cysteine, but rather immediately oxidized it. The organotelluranes inhibited integrin functions, such as adhesion, migration, and metalloproteinase secretion mediation in B16F10 murine melanoma cells. In comparison, a reduced derivative with no labile ligand inhibited adhesion of B16F10 cells to a significantly lower extent, thus pointing to the importance of the labile ligands of the Te(IV) atom. One of the organotelluranes inhibited circulating cancer cells in vivo, possibly by integrin inhibition. Our results extend the current knowledge on the reactivity and mechanism of organotelluranes with different labile ligands and highlight their clinical potential.

Antileishmanial activity of essential oil from Chenopodium ambrosioides and its main components against experimental cutaneous leishmaniasis in BALB/c mice

Chenopodium ambrosioides have been used during centuries by native people to treat parasitic diseases.

AIMS OF THE STUDY

To compare the in vivo anti-leishmanial activity of the essential oil (EO) from C. ambrosioides and its major components (ascaridole, carvacrol and caryophyllene oxide).

MATERIALS AND METHODS

Anti-leishmanial effect was evaluated in BALB/c mice infected with Leishmania amazonensis and treated with the EO, main compounds and artificial mix of pure components by intralesional route at 30 mg/kg every 4 days during 14 days. Diseases progression and parasite burden in infected tissues were determined.

RESULTS

EO prevented lesion development compared (p<0.05) with untreated animals and treated with vehicle. In addition, the efficacy of EO was also statistically superior (p<0.05) compared with the glucantime-treated animals. No potential effects were observed with pure components treatment. Mix of pure compounds cause death of animals after 3 days of treatment.

CONCLUSIONS

Our results demonstrate the superiority of EO against experimental cutaneous leishmaniasis caused by L. amazonensis.

Tri-phenyl-tellurium chloride

The asymmetric unit of the title compound, C18H15ClTe, contains two mol-ecules which are in inverted orientations. The compound displays a tetra-hedral geometry around the Te atom in spite of there being five electron domains. This is attributed to the fact that the lone pair is not sterically active. The dihedral angles between the three phenyl rings are 76.51 (16)/73.75 (16)/71.06 (17) and 78.60 (17)/77.67 (16)/79.11 (16)° in the two mol-ecules. The crystal packing features eight C-H⋯π inter-actions.

Oxidative stress in mice treated with antileishmanial meglumine antimoniate

In order to improve the understanding of the toxicity of pentavalent antimony (Sb(V)), we investigated the acute effects of meglumine antimoniate (MA) on the oxidative stress in heart, liver, kidney, spleen and brain tissue of mice. Levels of lipoperoxidation and protein carbonylation were measured to evaluate the oxidative status, whereas superoxide dismutase/catalase activity and glutathione levels were recorded to examine the antioxidative status. We observed that MA caused significant protein carbonylation in the heart, spleen and brain tissue. Increased lipoperoxidation was found in the liver and brain tissue. An imbalance between superoxide dismutase and catalase activities could be observed in heart, liver, spleen and brain tissue. Our results suggest that MA causes oxidative stress in several vital organs of mice. This indicates that the production of highly reactive oxygen and nitrogen species induced by MA might be involved in some of its toxic adverse effects.

Metalloid compounds as drugs

The six elements commonly known as metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Metalloid containing compounds have been used as antiprotozoal drugs. Boron-based drugs, the benzoxaboroles have been exploited as potential treatments for neglected tropical diseases. Arsenic has been used as a medicinal agent and arsphenamine was the main drug used to treat syphilis. Arsenic trioxide has been approved for the treatment of acute promyelocytic leukemia. Pentavalent antimonials have been the recommended drug for visceral leishmaniasis and cutaneous leishmaniasis. Tellurium (IV) compounds may have important roles in thiol redox biological activity in the human body, and ammonium trichloro (dioxoethylene-O, O'-)tellurate (AS101) may be a promising agent for the treatment of Parkinson's disease. Organosilicon compounds have been shown to be effective in vitro multidrug-resistance reverting agents.

Main-Group Medicinal Chemistry Including Li and Bi*

Main-group element compounds were among the first developed in the modern era as pharmaceutical preparations for the treatment of a wide variety of human ailments; it is now recognized that many of these elements exist in traditional medicine of many societies, for example, arsenic. The use of main-group element compounds in contemporary medicine continues for the treatment of, for example, depression (Li), stomach ulcers (Bi), cancer (As and Ga), and leishmaniasis (Sb). Not surprisingly, new compounds of these elements, and other main-group elements, continue to be investigated for their potential use in new therapies. In this chapter, the use of main-group elements as therapeutic agents is outlined and also, where understood, comments on biological targets and mechanisms of action. Further, key advances in new potential applications of main-group element compounds in medicine are evaluated.

In vitro and in vivo activity of an organic tellurium compound on Leishmania (Leishmania) chagasi

Tellurium compounds have shown several biological properties and recently the leishmanicidal effect of one organotellurane was demonstrated. These findings led us to test the effect of the organotellurium compound RF07 on Leishmania (Leishmania) chagasi, the agent of visceral leishmaniasis in Latin America. In vitro assays were performed in L. (L.) chagasi-infected bone marrow derived macrophages treated with different concentrations of RF07. In in vivo experiments Golden hamsters were infected with L. (L.) chagasi and injected intraperitoneally with RF07 whereas control animals received either Glucantime or PBS. The effect of RF07 on cathepsin B activity of L. (L.) chagasi amastigotes was assayed spectrofluorometrically using fluorogenic substrates. The main findings were: 1) RF07 showed significant leishmanicidal activity against intracellular parasites at submicromolar concentrations (IC50 of 529.7±26.5 nM), and the drug displayed 10-fold less toxicity to macrophages (CC50 of 5,426±272.8 nM); 2) kinetics assays showed an increasing leishmanicidal action of RF07 at longer periods of treatment; 3) one month after intraperitoneal injection of RF07 L. (L.) chagasi-infected hamsters showed a reduction of 99.6% of parasite burden when compared to controls that received PBS; 4) RF07 inhibited the cathepsin B activity of L. (L.) chagasi amastigotes. The present results demonstrated that the tellurium compound RF07 is able to destroy L. (L.) chagasi in vitro and in vivo at concentrations that are non toxic to the host. We believe these findings support further study of the potential of RF07 as a possible alternative for the chemotherapy of visceral leishmaniasis.

Therapeutic potential of selenium and tellurium compounds: opportunities yet unrealised

Despite being disparaged for their malodorous and toxic demeanour, compounds of selenium, a bio-essential element, and tellurium, offer possibilities as therapeutic agents. Herein, their potential use as drugs, for example, as anti-viral, anti-microbial, anti-inflammatory agents, etc., will be surveyed along with a summary of the established biological functions of selenium. The natural biological functions of tellurium remain to be discovered.

Bis(μ-phenyl-tellurido-κTe:Te)bis-[tetra-carbonyl-rhenium(I)]

The title compound, [Re(2)(C(6)H(5)Te)(2)(CO)(8)], crystallizes with two mol-ecules in the asymmetric unit, in which two Re atoms are coordinated in a slightly distorted octa-hedral environment and are bridged by two Te atoms, which show a distorted trigonal-pyramidal geometry. The torsion angles for the Te-Re-Te-Re sequence of atoms are 19.29 (18) and 16.54 (16)° in the two mol-ecules. Thus, the Re-Te four-membered rings in the two mol-ecules deviate significantly from planarity. Two intra-molecular C-H⋯O inter-actions occur in one of the mol-ecules. Te-Te [4.0551 (10) Å] inter-actions between the two mol-ecules and weak inter-molecular C-H⋯O inter-actions stabilize the crystal packing.

Heptacarbonyl-1κC,2κC-(4-phenyl-pyridine-1κN)di-μ-phenyltellurido-1:2κTe:Te-dirhenium(I)

In the title complex, [Re(2)(C(6)H(5)Te)(2)(C(11)H(9)N)(CO)(7)], two Re atoms are coordinated in slightly distorted octa-hedral coordination environments and are bridged by two Te atoms, which are coordinated in trigonal-pyramidal environments. The torsion angle for the Te-Re-Te-Re sequence of atoms is 17.06 (3)°. The crystal structure is stabilized by weak C-H⋯O and C-H⋯π inter-actions. In addition, there are Te⋯Te distances [4.0392 (12) Å] and O⋯O distances [2.902 (19) Å] which are shorter than the sum of the van der Waals radii for these atoms. A short inter-molecular lone pair⋯π distance [C O⋯Cg = 3.31 (2) Å] is also observed.