The in vitro biological activity towards the MDA‐MB‐231 triple‐negative breast cancer cell line of two different series of anionic Pt(II) organometallic complexes was tested. For the first time, cytotoxic activity of anionic Pt(II) complexes has been observed. The anionic compounds of general formula NBu4[(C^N)Pt(O^O)], where (C^N) represents the cyclometalated form of 2‐phenylpyridine (H(PhPy)), 2‐thienylpyridine (H(Thpy)) or 2‐benzo[h]quinoline (H(Bzq)), feature two different (O^O) chelated ligands: tetrabromocatechol [BrCat]2− (1–3) or alizarine [Aliz]2− (4–6). Complexes 1–6 displayed a significant cytotoxic effect against the studied cell line (IC50 range of 1.9–52.8 μM). For BrCat‐containing complexes 1–3, the biological activity was independent of the nature of the coordinated (C^N) ligand. In contrast, in the case of 4–6, the cytotoxicity (significantly high for 4) was concomitantly induced by the presence of either the PhPy or the [Aliz]2− ligand. Since complexes 1–6 are emissive in solution, the potential use of 4 as a theranostic agent was investigated using confocal analysis. The fluorescence signal from MDA‐MB‐231 cells incubated with 4 indicated the localization of the compound into the cytosol region.

Platinum compounds cytotoxicity is strictly related to their ability to be converted into active mono- and di-aquated species and consequently to the replacement of labile ligands by water molecules. This activation process makes the platinum center prone to nucleophilic substitution by DNA purines. In the present work, quantum mechanical density functional theory (DFT) computations and experimental investigations were carried out in order to shed light on the relationship between the internalization, aquation, and DNA binding of two isostructural anionic theranostic complexes previously reported by our group, NBu 4 [(PhPy)Pt(Aliz)], 1 ( IC 50 1.9 ± 1.6 μM), and NBu 4 [(PhPy)Pt(BrCat)], 2 ( IC 50 52.8 ± 3.9 μM). Cisplatin and a neutral compound [(NH 3 ) 2 Pt(Aliz)], 3 , were also taken as reference compounds. The computed energy barriers and the endergonicity of the hydrolysis reactions showed that the aquation rates are comparable for 1 and 2 , with a slightly higher reactivity of 1 . The second hydrolysis process was proved to be the rate-determining step for both 1 and 2 , unlike for compound 3 . The nucleophilic attack by the N7 site of guanine to both mono- and di-aquated forms of the complexes was computationally investigated as well, allowing to rationalize the observed different cytotoxicity. Computational results were supported by photostability data and biological assays, demonstrating DNA as the main target for compound 1 .

A series of electropolymerizable cyclometallated IrIII complexes were synthesized and their electrochemical and photophysical properties studied. The triphenylamine electropolymerizable fragment was introduced by using triphenylamine‐2‐phenylpyridine and, respectively, triphenylamine‐benzothiazole as cyclometalated ligands. The coordination sphere was completed by two differently substituted β‐ketoiminate ligands deriving from the condensation of acetylacetone or hexafluoroacetylacetone with para‐bromoaniline. The influence of the ‐CH3/‐CF3 substitution to the electrochemical and photophysical properties was investigated. Both complexes with CH3 substituted β‐ketoiminate were emissive in solution and in solid state. Highly stable films were electrodeposited onto ITO coated glass substrates. Their emission was quenched by electron trapping within the polymeric network as proven by electrochemical studies. The ‐CF3 substitution of the β‐ketoiminate leads instead to the quenching of the emission and inhibits electropolymerization.