Pyrazine-Coordinated Dinuclear and Mononuclear Ruthenium Complexes Formed via the Conversion of the Triply Chlorido-Bridged Diruthenium(II) Complex

The pyrazine-coordinated dinuclear and mononuclear ruthenium complexes were synthesized through the framework conversion reactions of the triply chlorido-bridged diruthenium(II) complex [{RuII,II(bbpma)}2(μ-Cl)3]+ (bbpma; benzylbis(2-pyridylmethyl)amine, [1]+) in the presence of pyrazine, which could function as the simple molecular multinucleation ligand of metal compounds. A reduction reaction of fac-[RuIIICl3(bbpma)] with zinc in the presence of hydrochloric acid afforded [1]+ in solution, and the following addition of pyrazine (1 equiv) in the solution led to the formation of a singly pyrazine (pz)-bridged diruthenium complex, [{RuII,II(μ-Cl2ZnCl2)(bbpma)}2(μ-pz)] ([2(II,II)(ZnCl2)2]). The stoichiometric two-electron oxidation of [2(II,II)(ZnCl2)2] was successfully proceeded, and a Ru(III)-Ru(III) species, [{RuIII,IIICl2(bbpma)}2(μ-pz)](PF6)2 ([III,III](PF6)2), was isolated. The reaction of [1]+ with excess amounts of pyrazine without hydrochloric acid afforded mononuclear Ru(III) and Ru(II) complexes containing one or two pyrazine, fac-[RuClm(pz)3-m(bbpma)]+ (m = 2; [3]+; m = 1; [4]+). The details of the electrochemical and spectroscopic properties of [1]+-[4]+ in organic and aqueous solutions were discussed.

Structural and electronic forms of doubly oxido/Pz and triply oxido/(Pz)2 bridged mixed valent and isovalent diruthenium complexes (Pz = pyrazolate)

The article reported on the diastereomeric dinuclear mixed-valent complexes [(acac)₂Ru(III)(μ-O)(μ-Pz^R)Ru(IV)(acac)₂] (R = H, Me, meso: ΔΛ, 1a-1c; rac: ΔΔ/ΛΛ, 2a-2c) and rac-[(acac)₂Ru(III)(μ-O)(μ-Iz)Ru(IV)(acac)₂], (2d) (HPz = pyrazole, HIz = indazole, acac = acetylacetonate). Moreover, the diruthenium(II,II) complexes [(HPz)₃Ru(II)(μ-O)(μ-Pz)₂ Ru(II)(HPz)₃] (3a) and [(HIz)₃Ru(II)(μ-O)(μ-Iz)₂Ru(II)(HIz)₃] (3d) were presented. The analogous form of 3a, i.e., [(HPz)₂(Pz)Ru(III)(μ-O)(μ-Pz)₂Ru(III)(Pz)(HPz)₂], was previously reported. Single crystal X-ray structures of 1a-1c/2a-2d and representative 3a showed their molecular forms, including the diastereomeric nature of the former. The Ru-O-Ru angle decreased appreciably on switching from doubly bridged 1 and 2 (128-135°) to triply bridged 3a (114°). Both series of complexes displayed rhombic symmetry in their EPR spectra, with g₁ and g₂ being very similar for 1a-1c with an almost axial look. The mixed-valence complex with a Ru(III)Ru(IV) (S = 1/2) state of 1 and 2 would lead to iso-valence complexes of Ru(III)Ru(III) and Ru(IV)Ru(IV) with an EPR inactive state by one electron redox reaction. On the other hand, metal based {Ru(II)Ru(II)/Ru(II)Ru(III), 3a/3a⁺} and terminal ligand (HPz/HPz^-, 3a/3a^-) based redox processes displayed anisotropic and free radical EPR, respectively. An IVCT (intervalence charge transfer) band was found for the delocalised mixed valent 1 and 2 {Ru(III)Ru(IV)} or 3a⁺ {Ru(II)Ru(III)} in the NIR region. The intense metal-to-ligand charge transfer (MLCT) transitions of 1-3 in the visible region varied systematically as a function of the metal oxidation state.

Designing biotin-human serum albumin nanoparticles to enhance the targeting ability of binuclear ruthenium(III) compound

On the one hand, to obtain a novel next-generation anticancer metal agent; on the other hand, to improve the targeting ability and decrease side effects of metal agent, we proposed to design active-targeting human serum albumin (HSA) nanoparticles (NPs) to achieve the end. Thus, we not only designed and synthesized two ruthenium (Ru) thiosemicarbazone compounds (C1 and C2) but also succeeded in constructing active Biotin-HSA NPs for Ru(III) compounds. Importantly, Biotin-HSA-C2 NPs not only possessed a stronger capacity for killing MCF-7 cells and inhibiting their migration versusC2 alone but also increased accumulation compared to non-malignant WI-38 cells. Additionally, C2 and Biotin-HSA-C2 NPs act against MCF-7 cells by the following potential mechanism: 1) arresting the cell cycle in the S phase by regulating cyclin and cyclin-dependent kinases; 2) inducing apoptosis by releasing cytochrome c to activate caspase-9/3; 3) inhibiting the expression of p-EGFR and regulating its neighboring cellular pathways, followed by the inactivation of PI3K/Akt and activation of p38 MAPK signaling pathways.