Clathrochelate Complexes Containing Axial Cymantrene and Tromancenium Moieties.

New clathrochelate complexes of manganese, iron and cobalt containing peripheral organometallic manganese moieties cymantrene or tromancenium were synthesized via self-assembly from di/tri-topic dioximes, metal templates and cymantrene/tromancenium boronic acid pinacol esters. These air-stable, highly colored, oligometallic complexes are composed of various combinations of MnIFeIIMnI, MnICoIIMnI, MnIMnIIMnIIMnI and MnICoIICoIIMnI metal assemblies with corresponding complicated magnetic and electrochemical properties. Full spectroscopic and structural characterization by 1H/11B/13C NMR, HRMS, IR, UV-vis, single crystal XRD and CV (cyclic voltammetry) is provided. Tetrametallic complexes containing tromanceniumyl substituents with two CoII or MnII central metals exhibit promising anticancer properties against different tumor cell lines.

Cobaltoceniumselenolate Gold(I) Complexes: Synthesis, Spectroscopic, Structural and Anticancer Properties.

Cobaltoceniumselenolate is an unusual, highly air-sensitive, mesoionic compound containing a very soft anionic selenium donor atom. Here we explore its coordination chemistry with Au(I) metal centers and show that its hetero- and homoleptic gold complexes are highly colored, air-stable compounds, which were characterized by 1H/13C/31P/77Se NMR, IR, UV-Vis, HR-MS and single crystal XRD. Cytotoxicity of these polar, water-soluble complexes was studied against various standard cancer cell lines (A549MDA-MB-231, HT-29) revealing good anticancer activity of all three complexes.

Gold(I) and Gold(III) N-Heterocyclic Carbene Complexes as Antibacterial Agents and Inhibitors of Bacterial Thioredoxin Reductase.

A series of (NHC)Au(I)Cl monocarbene complexes and their gold(III) analogues (NHC)Au(III)Cl3 were prepared and investigated as antibacterial agents and inhibitors of bacterial TrxR. The complexes showed stronger antibacterial effects against the Gram-positive MRSA and E. faecium strains than against several Gram-negative bacteria. All complexes were efficient inhibitors of bacterial thioredoxin reductase, indicating that inhibition of this enzyme might be involved in their mechanism of action. The efficacy of gold(I) and gold(III) analogues was comparable in most of the assays. The cytotoxicity of the gold NHC compounds against cancer and human cells was overall weaker than the activity against the Gram-positive bacteria, suggesting that their optimization as antibacterials warrants further investigation.

An Erlotinib gold(I) conjugate for combating triple-negative breast cancer.

An Erlotinib triphenylphosphane gold(I) conjugate has been prepared from AuCl(PPh3) and its crystal structure has been established by X-ray diffraction, showing a metallo-helicate formation. IC50 values of the new gold conjugate were calculated towards a panel of human tumor cell lines representative of breast (MCF-7, MDA-MB-231) and colon (HT-29) cancer cells. Overall, the gold conjugate exhibited higher cytotoxic activity than that of Erlotinib against the cancer cells studied. Particularly, the antiproliferative effect of the conjugate demonstrated to be 68-fold higher than Erlotinib in highly metastatic and triple negative MDA-MB-231 cell line. The gold conjugate caused DNA damage, reactive oxygen species (ROS) increase and induced apoptosis. Flow cytometry analysis showed that the conjugate induces significant arrest in S and G2/M phases primarily, whereas Erlotinib, as an inhibitor of epidermal growth factor receptor (EGFR), blocks G1/S transition and increases G1 cell population.

Preparation and Antitumoral Activity of Au-Based Inorganic-Organometallic Nanocomposites.

The synergy between gelator molecules and nanostructured materials is currently a novel matter of study. The possibility to carefully design the skeleton of the molecular entity as well as the nanostructure's morphological and chemical features offers the possibility to prepare a huge variety of nanocomposites with properties potentially different than just the sum of those of the individual building blocks. Here we describe the synthesis and characterization of nanocomposites made by the unconventional combination of phosphine-Au(I)-alkynyl-based organometallic gelating molecules and plasmonic Au nanoparticles. Our results indicate that the interaction between the two moieties leads to a significant degree of aggregation in both hydrophilic and hydrophobic media, either when using DAPTA or PTA-based organometallic molecules, with the formation of a sponge-like hybrid powder upon solvent evaporation. The biological activity of the nanocomposites was assessed, suggesting the existence of a synergetic effect evidenced by the higher cytotoxicity of the hybrid systems with respect to that of any of their isolated counterparts. These results represent a preliminary proof-of-concept for the exploitation of these novel nanocomposites in the biomedical field.

Highly Electrophilic, Catalytically Active and Redox-Responsive Cobaltoceniumyl and Ferrocenyl Triazolylidene Coinage Metal Complexes.

A convenient access to a triad of triazoles with ferrocenyl and cobaltoceniumyl substituents is reported. N-Alkylation, deprotonation and metalation with CuI /AgI /AuI synthons affords the heteroleptic triazolylidene complexes. Due to the combination of neutral, electron-donating ferrocenyl substituents and cationic, strongly electron-withdrawing cobaltocenium substituents, the mesoionic carbene (MIC) ligands of these complexes are electronically interesting "push-pull", "pull-push" and "pull-pull" metalloligands with further switchable redox states based on their fully reversible FeII /FeIII , (ferrocene/ferrocenium) and CoIII /CoII , (cobaltocenium/cobaltocene) redox couples. These are the first examples of metal complexes of (di)cationic NHC ligands based on cobaltoceniumyl substituents. DFT calculated Tolman electronic parameter (TEP) of the new MIC ligands, show these metalloligands to be extremely electron-poor NHCs with properties unmatched in other carbene chemistry. Utilization of these multimetallic electronically tunable compounds in catalytic oxazoline synthesis and in antitumor studies are presented. Remarkably, 1 mol % of the AuI complex with the dicationic MIC ligand displays full catalytic conversion, without the need for any other additives, in less than 2 hours at ambient temperatures. These results thus firmly establish these new classes of cobaltoceniumyl based (di)cationic MIC ligands as prominent players in several branches of chemistry.