The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Olivier Buriez - One of the best experts on this subject based on the ideXlab platform.
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New mechanistic insights into osmium-based tamoxifen derivatives
Electrochimica Acta, 2019Co-Authors: Hui Zhi Shirley Lee, François Chau, Eric Labbé, Siden Top, Gérard Jaouen, Anne Vessières, Olivier BuriezAbstract:Abstract The electrochemical behavior of osmociphenol (3, Oc-OH), an organometallic osmium-based anticancer drug candidate, has been investigated by cyclic voltammetry in the absence and presence of lutidine used as a base model. Osmociphenol exhibited spontaneous deprotonation of the phenol function upon oxidation of the Osmocene moiety due to its high acidity. In the presence of lutidine, a base-dependent and different electrochemical behavior was observed at low scan rates indicating a second oxidation step leading to the corresponding cationic quinone methide precursor (3b+). However, compared to ruthenocene derivatives, the stability of 3b+ prevented its conversion into quinone methide as the final and stable complex. Despite differences in their oxidative processes, osmociphenol and ruthenociphenol derivatives exhibit similar biological activities.
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Molecular Electrochemistry: a Central Method to Understand the Metabolic Activation of Therapeutic Agents. The Example of Metallocifen Anti-Cancer Drug Canditates
Current Opinion in Electrochemistry, 2017Co-Authors: Christian Amatore, Eric Labbé, Olivier BuriezAbstract:Organometallic chemistry has allowed the design and emergence of a new class of metal-based bioactive molecules and a variety of drugs used or still tested against cancer. In this field, beyond the well-known cisplatin, major contributions have focused on the functionalization of clinically validated purely organic drugs with complexes derivatized by a metallocene group. This approach, which exalts the anti-cancer properties of the organic moiety, has been successfully used to design ferrocifens. These complexes involve a ferrocenyl group covalently grafted onto the tamoxifen skeleton, the current gold standard for endocrine breast cancer therapy. Based on the same strategy, several original ruthenocene-and Osmocene-tamoxifen derivatives have been recently synthesized and successfully tested against breast and other cancer cells. The development of such potent metallodrugs was made possible thanks to the accurate mechanistic understanding of the metallodrugs activation provided by the synergistic combination of electrochemical and biological approaches.
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Molecular electrochemistry: A central method to understand the metabolic activation of therapeutic agents. The example of metallocifen anti-cancer drug candidates
Current Opinion in Electrochemistry, 2017Co-Authors: Christian Amatore, Eric Labbé, Olivier BuriezAbstract:Organometallic chemistry has allowed the design and emergence of a new class of metal-based bioactive molecules and a variety of drugs used or still tested against cancer. In this field, beyond the well-known cisplatin, major contributions have focused on the functionalization of clinically validated purely organic drugs with complexes derivatized by a metallocene group. This approach, which exalts the anti-cancer properties of the organic moiety, has been successfully used to design ferrocifens. These complexes involve a ferrocenyl group covalently grafted onto the tamoxifen skeleton, the current gold standard for endocrine breast cancer therapy. Based on the same strategy, several original ruthenocene (Rc)-tamoxifen derivatives and Osmocene (Os)-tamoxifen derivatives have been recently synthesized and successfully tested against breast and other cancer cells. The development of such potent metallodrugs was made possible thanks to the accurate mechanistic understanding of the metallodrugs activation provided by the synergistic combination of electrochemical and biological approaches.
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Revisiting the Complex Osmocene Electro-Oxidation Mechanism
Electrochimica Acta, 2016Co-Authors: François Chau, Christian Amatore, Eric Labbé, Olivier BuriezAbstract:Abstract The electrochemical oxidation of Osmocene was investigated in dichloromethane (DCM) and acetonitrile (MeCN) in the presence of various electrolyte anions ([BF 4 ] − , [PF 6 ] − , and [B(C 6 F 5 ) 4 ] − (TFAB)). The results showed that the reactivity of the electrogenerated osmocenium cation was dramatically affected by the coordinating properties of the electrolyte anion and the donor strength of the solvent. Cyclic voltammetry allowed the characterization of transient species and led to rationalization of some controversial mechanistic conclusions published before, which were in fact all correct, but referred to different conditions. Notably, the electrochemical signature of the dimer dication [Cp 2 Os] 2 2+ that appears as a crucial species to explain the voltammetric oxidative pattern of Osmocene was detected for the first time.
Arnd Vogler - One of the best experts on this subject based on the ideXlab platform.
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Photochemistry of Osmocene. Reductive elimination and generation of elemental osmium
Inorganic Chemistry Communications, 2014Co-Authors: Horst Kunkely, Arnd VoglerAbstract:Abstract Osmocene is intrinsically photoactive. It photolyzes in n-hexane by a reductive elimination leading to the generation of metallic osmium. Moreover, both cyclopentadienyl anions as ligands in Osmocene are oxidatively eliminated. Surprisingly, they are liberated as benzene and cyclobutadiene which is trapped by diphenyl acetylene. As a result of this trapping o-terphenyl is formed. It is suggested that in the LF excited state both cyclopentadienyl ligands undergo a bending in agreement with the previous conclusions. The close approach of both ligands facilitates a CH group transfer between them. The subsequent decay generates elemental osmium, benzene and cyclobutadiene as photolysis products.
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Dehydrogenation of 1,3-cyclohexadiene photocatalyzed by Osmocene
Inorganic Chemistry Communications, 2010Co-Authors: Horst Kunkely, Arnd VoglerAbstract:Abstract Osmocene acts as a photocatalyst for the dehydrogenation of 1,3-cyclohexadiene which yields benzene and hydrogen. It is suggested that the primary photochemical step is an electron transfer from the excited Osmocene to the diene.
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Water splitting by light with Osmocene as photocatalyst.
Angewandte Chemie (International ed. in English), 2009Co-Authors: Horst Kunkely, Arnd VoglerAbstract:Last but not least: A simple molecular redox system is used to split water into hydrogen and oxygen photochemically. Two separate photolyses are combined to a cyclic process (see scheme). Osmocene ([Cp(2)Os(II)] with Cp(-) = C(5)H(5)(-)) serves as photocatalyst.
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Phosphorescence of permercurated Osmocene at ambient conditions
Inorganic Chemistry Communications, 2008Co-Authors: Horst Kunkely, Arnd VoglerAbstract:Abstract The permercurated Osmocene derivative Os[C5(HgOAc)5]2 shows a LF phosphorescence at λmax = 770 nm at ambient conditions. This triplet emission is facilitated by the heavy-atom effect of mercury and, possibly, by the absence of C–H vibrations which may assist radiationless deactivation in Osmocene.
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Photoluminescence of Osmocene and decamethylOsmocene
Transition Metal Chemistry, 2000Co-Authors: Horst Kunkely, Arnd VoglerAbstract:Osmocene (and decamethylOsmocene) is characterized by a lowest-energy ligand field triplet which occurs at λ_max = 372 nm (374 nm) in absorption and 567 nm (572 nm) in emission. This orange–yellow phosphorescence is rather intense at 77 K but is also visible at r.t.
Julia Hein - One of the best experts on this subject based on the ideXlab platform.
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The Preparation of Tetramethyl 1,1′,3,3′-Ruthenocenetetracarboxylate and Tetramethyl 1,1′,3,3′-Osmocenetetracarboxylate, and a Simplified Synthesis for Tetramethyl 1,1′,3,3′-Ferrocenetetracarboxylate
Synthesis, 2018Co-Authors: Jan Klett, Julia HeinAbstract:Substituted metallocenes with more than two substituents have to be synthesized using doubly substituted cyclopentadiene rings in a reaction with a metal compound or by the introduction of additional functional groups to an already di-substituted metallocene. The direct formation of tetra-substituted metallocenes often suffers due to insufficient reactivity of the reagents or the resulting product mixtures, which are hard to separate. In this work, a protocol, which was successful in a tetra-substitution of ferrocene by a tetra-metalation followed by a reaction with carbon dioxide, is used to perform the tetra-substitution of ruthenocene and Osmocene. In addition, a simplified protocol for the tetra-functionalization of ferrocene using commercially available components on a medium scale is described.
Gabriel Merino - One of the best experts on this subject based on the ideXlab platform.
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how strong are the metallocene metallocene interactions cases of ferrocene ruthenocene and Osmocene
Physical Chemistry Chemical Physics, 2016Co-Authors: Alba Vargascaamal, Filiberto Ortizchi, Jose Luis Cabellos, Roberto A Boto, Julia Contrerasgarcia, Albeiro Restrepo, Pratim K Chattaraj, Gabriel MerinoAbstract:An exhaustive exploration of the potential energy surfaces of ferrocene, ruthenocene and Osmocene dimers has been performed. Our computations involving dispersion show that only four different isomers are present in each metallocene dimer. The collective action of small interaction energies of dispersive nature leads to a dissociation energy of 7.5 kcal mol−1 for the ferrocene dimer. Dispersion has strong effects on the geometrical parameters, reducing the M⋯M distances by almost 1 A. Our results also reveal that inclusion of entropic factors modifies the relative stability of the complexes. The nature of bonding is examined using the energy decomposition analysis and the non-covalent interaction index. Both analyses indicate that dispersion is the major contributing factor in stabilizing a metallocene dimer.
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How strong are the metallocene–metallocene interactions? Cases of ferrocene, ruthenocene, and Osmocene
Physical Chemistry Chemical Physics, 2015Co-Authors: Alba Vargas-caamal, Jose Luis Cabellos, Roberto A Boto, Albeiro Restrepo, Pratim K Chattaraj, Filiberto Ortiz-chi, Julia Contreras-garcía, Gabriel MerinoAbstract:An exhaustive exploration of the potential energy surfaces of ferrocene, ruthenocene and Osmocene dimers has been performed. Our computations involving dispersion show that only four different isomers are present in each metallocene dimer. The collective action of small interaction energies of dispersive nature leads to a dissociation energy of 7.5 kcal mol−1 for the ferrocene dimer. Dispersion has strong effects on the geometrical parameters, reducing the M⋯M distances by almost 1 A. Our results also reveal that inclusion of entropic factors modifies the relative stability of the complexes. The nature of bonding is examined using the energy decomposition analysis and the non-covalent interaction index. Both analyses indicate that dispersion is the major contributing factor in stabilizing a metallocene dimer.
E Padma J Malar - One of the best experts on this subject based on the ideXlab platform.
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can the cyclo p5 ligand introduce basicity at the transition metal center in metallocenes a hybrid density functional study on the cyclo p5 analogues of metallocenes of fe ru and os
European Journal of Inorganic Chemistry, 2004Co-Authors: E Padma J MalarAbstract:Density functional theory (DFT) calculations and natural population analysis (NPA) performed on metallocenes of Fe, Ru and Os triad reveal that the cyclo-P5 ligand introduces basicity at the metal center. All-electron calculations at the B3LYP/6-311+G* level yield NPA charges of 0.28, −0.28 and −0.91 at the iron center in [FeCp2], [FeCp(η 5 -P5)] and [Fe(η 5 P5)2], respectively. The same trend in the charges is observed even when the core electrons of the metal are replaced by effective core potentials (ECPs). The accumulation of negative charge at the metal center is found to be similar in the cyclo-P5 analogues of ruthenocene and Osmocene. Thus, for example, the net NPA charges on Ru and Os in the decaphosphametallocenes are predicted to be −0.6 to −0.9, respectively, at different levels of calculations involving ECPs. The natural orbital populations show a small transfer of electron
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Can the cyclo‐P5 Ligand Introduce Basicity at the Transition Metal Center in Metallocenes? A Hybrid Density Functional Study on the cyclo‐P5 Analogues of Metallocenes of Fe, Ru and Os
European Journal of Inorganic Chemistry, 2004Co-Authors: E Padma J MalarAbstract:Density functional theory (DFT) calculations and natural population analysis (NPA) performed on metallocenes of Fe, Ru and Os triad reveal that the cyclo-P5 ligand introduces basicity at the metal center. All-electron calculations at the B3LYP/6-311+G* level yield NPA charges of 0.28, −0.28 and −0.91 at the iron center in [FeCp2], [FeCp(η 5 -P5)] and [Fe(η 5 P5)2], respectively. The same trend in the charges is observed even when the core electrons of the metal are replaced by effective core potentials (ECPs). The accumulation of negative charge at the metal center is found to be similar in the cyclo-P5 analogues of ruthenocene and Osmocene. Thus, for example, the net NPA charges on Ru and Os in the decaphosphametallocenes are predicted to be −0.6 to −0.9, respectively, at different levels of calculations involving ECPs. The natural orbital populations show a small transfer of electron