Modeling Biological Copper Clusters: Synthesis of a Tricopper Complex, and Its Chloride- and Sulfide-Bridged Congeners

Di- and Trinuclear Mixed-Valence Copper Amidinate Complexes from Reduction of Iodine

Molecular examples of mixed-valence copper complexes through chemical oxidation are rare but invoked in the mechanism of substrate activation, especially oxygen, in copper-containing enzymes. To examine the cooperative chemistry between two metals in close proximity to each other we began studying the reactivity of a dinuclear Cu(I) amidinate complex. The reaction of [(2,6-Me2C6H3N)2C(H)]2Cu2, 1, with I2 in tetrahydrofuran (THF), CH3CN, and toluene affords three new mixed-valence copper complexes [(2,6-Me2C6H3N)2C(H)]2Cu2(μ2-I3)(THF)2, 2, [(2,6-Me2C6H3N)2C(H)]2Cu2(μ2-I) (NCMe)2, 3, and [(2,6-Me2C6H3N)2C(H)]3Cu3(μ3-I)2, 4, respectively. The first two compounds were characterized by UV-vis and electron paramagnetic resonance spectroscopies, and their molecular structure was determined by X-ray crystallography. Both di- and trinuclear mixed-valence intermediates were characterized for the reaction of compound 1 to compound 4, and the molecular structure of 4 was determined by X-ray crystallography. The electronic structure of each of these complexes was also investigated using density functional theory.

Reactivity of Hydride Bridges in High-Spin [3M-3(μ-H)] Clusters (M = FeII, CoII)

The designed [3M-3(μ-H)] clusters (M = Fe(II), Co(II)) Fe3H3L (1-H) and Co3H3L (2-H) [where L(3-) is a tris(β-diketiminate) cyclophane] were synthesized by treating the corresponding M3Br3L complexes with KBEt3H. From single-crystal X-ray analysis, the hydride ligands are sterically protected by the cyclophane ligand, and these complexes selectively react with CO2 over other unsaturated substrates (e.g., CS2, Me3SiCCH, C2H2, and CH3CN). The reaction of 1-H or 2-H with CO2 at room temperature yielded Fe3(OCHO)(H)2L (1-CO2) or Co3(OCHO)(H)2L (2-CO2), respectively, which evidence the differential reactivity of the hydride ligands within these complexes. The analogous reactions at elevated temperatures revealed a distinct difference in the reactivity pattern for 2-H as compared to 1-H; Fe3(OCHO)3L (1-3CO2) was generated from 1-H, while 2-H afforded only 2-CO2.

Metal containing cryptands as hosts for anions: evaluation of Cu(i)⋯X and π⋯X interactions in halide–tricopper(i) complexes through relativistic DFT calculations

More selective than crown ethers, cryptands arise as suitable hosts for several ions, with the size of the cavity and the behavior of the atoms belonging to the structure being the main factors governing their selectivity.

Alkali metal control over N-N cleavage in iron complexes

Though N2 cleavage on K-promoted Fe surfaces is important in the large-scale Haber-Bosch process, there is still ambiguity about the number of Fe atoms involved during the N-N cleaving step and the interactions responsible for the promoting ability of K. This work explores a molecular Fe system for N2 reduction, particularly focusing on the differences in the results obtained using different alkali metals as reductants (Na, K, Rb, Cs). The products of these reactions feature new types of Fe-N2 and Fe-nitride cores. Surprisingly, adding more equivalents of reductant to the system gives a product in which the N-N bond is not cleaved, indicating that the reducing power is not the most important factor that determines the extent of N2 activation. On the other hand, the results suggest that the size of the alkali metal cation can control the number of Fe atoms that can approach N2, which in turn controls the ability to achieve N2 cleavage. The accumulated results indicate that cleaving the triple N-N bond to nitrides is facilitated by simultaneous approach of least three low-valent Fe atoms to a single molecule of N2.

Arene ruthenium(ii) complex, a potent inhibitor against proliferation, migration and invasion of breast cancer cells, reduces stress fibers, focal adhesions and invadopodia

Effective chemotherapy drugs for cancer that would inhibit tumor growth and suppress metastasis are currently lacking. In this study, a series of arene ruthenium complexes, [(η6-arene)Ru(H2iip)Cl]Cl (arene = p-cymene, RAWQ03; CH3C6H5, RAWQ04; and C6H6, RAWQ11), were synthesized and their inhibitory activity against tumor cells were evaluated. The results showed that the complex RAWQ11 inhibited the growth of MDA-MB-231 breast cancer cells by inducing S-phase arrest, which is closely related to the inhibition of cell mitosis-mediated cell nucleus damage. Further studies showed that RAWQ11 can inhibit the invasion and metastasis of MDA-MB-231 cells. The morphology of MDA-MB-231 cells changed, the number of focal adhesions decreased, and the stress fibers de-polymerized upon dealing with the complex RAWQ11. The FITC-gelatin assay confirmed that the formation of invadopodia in MDA-MB-231 cells was significantly blocked by RAWQ11. Furthermore, RAWQ11 can block the AKT signal pathway by upregulating the PTEN expression through binding and downregulating miR-21. These results demonstrated that this type of arene ruthenium(ii) complex can block the invadopodia formation by regulating the PTEN/AKT signal pathway mediated by miR-21 to inhibit the invasion and metastasis of breast cancer cells. Therefore, this complex can be used as a potential dual functional agent to inhibit the growth and metastasis of tumor cells.