Platinum(IV)-Gold(I) Agents with Promising Anticancer Activity: Selected Studies in 2D and 3D Triple-Negative Breast Cancer Models

New heterometallic binuclear and trinuclear platinum(IV)-gold(I) compounds of the type [Pt(L)n Cl2 (OH){(OOC-4-C6 H4 -PPh2 )AuCl}x ] (L=NH3 , n=2; x=1, 2; L=diaminocyclohexane, DACH, n=1; x=2) are described. These compounds are cytotoxic and selective against a small panel of renal, bladder, ovarian, and breast cancer cell lines. We selected a trinuclear PtAu2 compound containing the PtIV core based on oxaliplatin, to further investigate its cell-death pathway, cell and organelle uptake and anticancer effects against the triple-negative breast cancer (TNBC) MDA-MB-231 cell line. This compound induces apoptosis and accumulates mainly in the nucleus and mitochondria. It also exerts remarkable antimigratory and antiangiogenic properties, and has a potent cytotoxic effect against TNBC 3D spheroids. Trinuclear compounds do not seem to display relevant interactions with calf thymus (CT) DNA and plasmid (pBR322) even in the presence of reducing agents, but inhibit pro-angiogenic enzyme thioredoxin reductase (TrxR) in TNBC cells.

Interligand communication in a metal mediated LL'CT system - a case study

A series of oxo-Mo(iv) complexes, [MoO(Dt²⁻)(Dt⁰)] (where Dt²⁻ = benzene-1,2-dithiol (bdt), toluene-3,4-dithiol (tdt), quinoxaline-2,3-dithiol (qdt), or 3,6-dichloro-benzene-1,2-dithiol (bdtCl₂); Dt⁰ = N,N′-dimethylpiperazine-2,3-dithione (Me₂Dt⁰) or N,N′-diisopropylpiperazine-2,3-dithione (ⁱPr₂Dt⁰)), possessing a fully oxidized and a fully reduced dithiolene ligand have been synthesized and characterized. The assigned oxidation states of coordinated dithiolene ligands are supported with spectral and crystallographic data. The molecular structure of [MoO(tdt)(ⁱPr₂Dt⁰)] (6) demonstrates a large ligand fold angle of 62.6° along the S⋯S vector of the Dt⁰ ligand. The electronic structure of this system is probed by density functional theory (DFT) calculations. The HOMO is largely localized on the Dt²⁻ ligand while virtual orbitals are mostly Mo and Dt⁰ in character. Modeling the electronic spectrum of 6 with time dependent (TD) DFT calculations attributes the intense low energy transition at ∼18 000 cm⁻¹ to a ligand-to-ligand charge transfer (LL′CT). The electron density difference map (EDDM) for the low energy transition depicts the electron rich Dt²⁻ ligand donating charge density to the redox-active orbitals of the electron deficient Dt⁰ ligand. Electronic communication between dithiolene ligands is facilitated by a Mo-monooxo center and distortion about its primary coordination sphere.

The interligand communication between non-innocent dithiolene ligands of different oxidation states has been described in a Mo system. The fully reduced ene-dithiolate (Dt²⁻) acts as a donor moiety to the oxidized dithione (Dt⁰) in an LL′CT process.