Valérie Deborde

Phosphole-based π-conjugated electroluminescent materials for OLEDs

Novel mixed phosphole–fluorene π-conjugated systems have been prepared using the Fagan–Nugent route. Their optical (UV-visible absorption, fluorescence spectra) and electrochemical properties have been systematically evaluated. The variation of the substitution pattern of phosphole derivatives and chemical modification of their P atoms afford thermally stable derivatives which are photoluminescent. The use of these derivatives as emitters in OLEDs strongly depends on the substituent linked on the P-atom. The gold complexes are not stable electroluminescent materials since they decompose rapidly when the devices are operating. In contrast, the thiooxophospholes are stable electroluminescent materials, and the OLEDs incorporating these derivatives as emitters display very high performances.

A Sugar‐Modified Phosphole Gold Complex with Antiproliferative Properties Acting as a Thioredoxin Reductase Inhibitor in MCF‐7 Cells

TrxR possesses a Cys SeCys catalytic pair in the more flexible C-terminal domain, in addition to the N-terminal Cys XXXX Cys active site. Trx contains a Cys pair which, in a reduced state, is essential for reducing disulfide bridges critical for protein activity. TrxR and Trx form an important redox system involved in multiple physiological processes. Reduced thioredoxin can provide reducing equivalents to a number of proteins including ribonucleotide reductase, which is involved in DNA synthesis and consequently in cell proliferation. The TrxR/Trx system is also involved in the cellular protection from or repair following oxidative stress, and in the regeneration of antioxidants such as vitamin C, ubiquinone, and lipoic acid. Additionally, the TrxR/Trx system modulates the activity of transcription factors involved in various signaling pathways related to apoptosis and cellular response to growth factors. TrxR and Trx have been shown to be overexpressed in several tumor types, and increased levels are known to regulate both cancer cell growth and survival. Furthermore, overexpression appears to be correlated with chemotherapeutic resistance, aggressive tumor types and poor prognosis. Taken together, these observations present the TrxR/Trx system as a target of interest for the development of new anticancer agents. Several TrxR inhibitors have already been identified and have shown growth inhibition against tumor cells (for a recent review, see ref. [6]). Among those, metal–ligand complexes are of particular interest because of their combined abilities to irreversibly target the dithiol/selenol catalytic pair essential for TrxR activity and bind DNA. Nine compounds have been evaluated in the present study for their cytotoxic activities against the human breast cancer MCF-7 cell line using a flow cytometric analysis with 2’, 7’-dichlorodihydrofluorescein diacetate (H2DCFDA) and propidium iodide (PI) staining. These compounds were selected or designed with the aim of targeting disulfide reductase activity known to be overexpressed in cancer. Analogues 1 and 2 (Figure 1) are metal-free phosphole ligands and derivative 3 has shown slight cytotoxicity in B16 melanoma and P388 leukemia cells. Phosphine-coordinated gold(I) thiosugar complexes such as auranofin (4) was developed for the treatment of rheumatoid arthritis, a disorder associated with TrxR overexpression, and reported to inhibit the purified TrxR from human placenta. Phosphole-containing gold and platinum complexes 5, 6, 7 and GoPI (8, {1-phenyl-2,5-di(2-pyridyl)phosphole}AuCl) are irreversible inhibitors of purified human GR and TrxR. 15]

A bridging ligand featuring terminal 2-pyridylphosphole moieties: synthesis, optical properties and Ru(II)-complex

Abstract 2,2′-Di[2-(5-(2-pyridyl)phospholyl)]thiophene ( 2a ) has been obtained in 63% yield via the Fagan–Nugents route. Derivative 2a possesses an extended π-conjugated system and behaves as a bis( P , N -chelate) towards cationic ( p -cymene)RuCl fragments affording the air-stable complex 3a in 60% yield. A diastereoselective coordination was observed and the solid state structure of the model Ru-complex 2b featuring a related 2-(2-pyridyl)-5-(2-thienyl)phosphole ligand is presented.

2,5-Di(2-pyridyl)phospholes: model compounds for the engineering of π-conjugated donor–acceptor co-oligomers with a chemically tunable HOMO–LUMO gap

2,5-Di(2-pyridyl)phospholes possess an extended π-conjugated system with a charge transfer structure; high yielding chemical modifications involving the phosphorus atom allow fine tuning of the HOMO–LUMO gap.