Dataset Information

Taming a monomeric [Cu(?⁶-C₆H₆)]⁺ complex with silylene.

ABSTRACT: Previous theoretical and experimental endeavors suggested that [Cu(C₆H₆)]⁺ prefers the ?¹/?² mode over the ?⁶ mode due to the augmented repulsion between the benzene ring and metal d-electrons. Nevertheless, the use of silylene as a neutral ligand has led to the isolation of the first monomeric copper cation, [{PhC(NtBu)₂SiN(SiMe₃)₂}Cu(?⁶-C₆H₆)]⁺[SbF₆]^- (3), where a copper atom is bound to the benzene ring in an unsupported ?⁶ fashion. However, the use of IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) in place of silylene results in the formation of [IPr·Cu(?²-C₆H₆)]⁺[SbF₆]^- (6), where the copper atom is bound to the benzene ring in the ?² mode. The discrepancy in hapticities is also reflected when hexamethylbenzene is employed as the arene ring. The silylene supported copper cation continues to bind in the ?⁶ mode in 2 while the NHC copper cation displays an ?³ bonding mode in 5. DFT calculations are carried out to understand how the use of silylene led to the ?⁶ binding mode and why IPr afforded the ?² binding mode.

SUBMITTER: Parvin N

PROVIDER: S-EPMC5944381 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Taming a monomeric [Cu(η6-C6H6)]+ complex with silylene.

Parvin Nasrina N Pal Shiv S Echeverría Jorge J Alvarez Santiago S Khan Shabana S

Chemical science 20180413 18

Previous theoretical and experimental endeavors suggested that [Cu(C6H6)]+ prefers the η1/η2 mode over the η6 mode due to the augmented repulsion between the benzene ring and metal d-electrons. Nevertheless, the use of silylene as a neutral ligand has led to the isolation of the first monomeric copper cation, [{PhC(NtBu)2SiN(SiMe3)2}Cu(η6-C6H6)]+[S ...[more]

PMID: 29780565

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Project description:BackgroundDiacetyl-bis(N4-methylthiosemicarbazone), labeled with 64Cu (64Cu-ATSM) has been suggested as a promising tracer for imaging hypoxia. However, various controversial studies highlighted potential pitfalls that may disable its use as a selective hypoxic marker. They also highlighted that the results may be tumor location dependent. Here, we first analyzed uptake of Cu-ATSM and its less lipophilic counterpart Cu-Cl2 in the tumor over time in an orthotopic glioblastoma model. An in vitro study was also conducted to investigate the hypoxia-dependent copper uptake in tumor cells. We then further performed a comprehensive ex vivo study to compare 64Cu uptake to hypoxic markers, specific cellular reactions, and also transporter expression.MethodsμPET was performed 14 days (18F-FMISO), 15 days (64Cu-ATSM and 64Cu-Cl2), and 16 days (64Cu-ATSM and 64Cu-Cl2) after C6 cell inoculation. Thereafter, the brains were withdrawn for further autoradiography and immunohistochemistry. C6 cells were also grown in hypoxic workstation to analyze cellular uptake of Cu complexes in different oxygen levels.ResultsIn vivo results showed that Cu-ASTM and Cu-Cl2 accumulated in hypoxic areas of the tumors. Cu-ATSM also stained, to a lesser extent, non-hypoxic regions, such as regions of astrogliosis, with high expression of copper transporters and in particular DMT-1 and CTR1, and also characterized by the expression of elevated astrogliosis. In vitro results show that 64Cu-ATSM showed an increase in the uptake only in severe hypoxia at 0.5 and 0.2% of oxygen while for 64Cu-Cl2, the cell retention was significantly increased at 5% and 1% of oxygen with no significant rise at lower oxygen percentages.ConclusionIn the present study, we show that Cu-complexes undoubtedly accumulate in hypoxic areas of the tumors. This uptake may be the reflection of a direct dependency to a redox metabolism and also a reflection of hypoxic-induced overexpression of transporters. We also show that Cu-ATSM also stained non-hypoxic regions such as astrogliosis.

Project description:Copper-dependent metalloenzymes are widespread throughout metabolic pathways, coupling the reduction of O2 with the oxidation of organic substrates. Small-molecule synthetic analogs are useful platforms to generate L/Cu/O2 species that reproduce the structural, spectroscopic, and reactive properties of some copper-/O2-dependent enzymes. Landmark studies have shown that the conversion between dicopper(II)-peroxo species (L2CuII2(O22-) either side-on peroxo, SP, or end-on trans-peroxo, TP) and dicopper(III)-bis(μ-oxo) (L2CuIII2(O2-)2: O) can be controlled through ligand design, reaction conditions (temperature, solvent, and counteranion), or substrate coordination. We recently published ( J. Am. Chem. Soc. 2012 , 134 , 8513 , DOI: 10.1021/ja300674m ) the crystal structure of an unusual SP species [(MeAN)2CuII2(O22-)]2+ (SPMeAN, MeAN: N-methyl-N,N-bis[3-(dimethylamino)propyl]amine) that featured an elongated O-O bond but did not lead to O-O cleavage or reactivity toward external substrates. Herein, we report that SPMeAN can be activated to generate OMeAN and perform the oxidation of external substrates by two complementary strategies: (i) coordination of substituted sodium phenolates to form the substrate-bound OMeAN-RPhO- species that leads to ortho-hydroxylation in a tyrosinase-like fashion and (ii) addition of stoichiometric amounts (1 or 2 equiv) of Lewis acids (LA's) to form an unprecedented series of O-type species (OMeAN-LA) able to oxidize C-H and O-H bonds. Spectroscopic, computational, and mechanistic studies emphasize the unique plasticity of the SPMeAN core, which combines the assembly of exogenous reagents in the primary (phenolates) and secondary (Lewis acids association to the MeAN ligand) coordination spheres with O-O cleavage. These findings are reminiscent of the strategy followed by several metalloproteins and highlight the possible implication of O-type species in copper-/dioxygen-dependent enzymes such as tyrosinase (Ty) and particulate methane monooxygenase (pMMO).

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Taming a monomeric [Cu(?⁶-C₆H₆)]⁺ complex with silylene.

Publications

Taming a monomeric [Cu(η<sup>6</sup>-C<sub>6</sub>H<sub>6</sub>)]<sup>+</sup> complex with silylene.

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OmicsDI is part of the ELIXIR infrastructure

Dataset Information

Taming a monomeric [Cu(?6-C6H6)]+ complex with silylene.

Publications

Taming a monomeric [Cu(η<sup>6</sup>-C<sub>6</sub>H<sub>6</sub>)]<sup>+</sup> complex with silylene.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Taming a monomeric [Cu(?⁶-C₆H₆)]⁺ complex with silylene.