Sébastien Clément

Two‐Photon‐Triggered Drug Delivery via Fluorescent Nanovalves

Mesoporous silica nanoparticles (MSN) are functionalized in the walls with an original fluorophore with a high two-photon absorption cross-section. The pores of the MSN filled with anticancer drug are blocked with a pseudo-rotaxane constituted by an azobenzene stalk and a β-cyclodextrin moiety. After incubation of the nanosystem with MCF-7 breast cancer cells, two-photon irradiation at low power is used to image the cells. At high power, cancer cell killing is observed due to the two-photon-triggered opening of the pores through FRET and the release of the anticancer drug from the MSN.

Reactivity of gold nanoparticles towards N-heterocyclic carbenes

The reaction of gold nanoparticles with benzimididazol-2-ylidene ligands leads to the formation of well-defined bis-carbene gold(i) complexes, as shown by characterization techniques such as powder XRD and solid state NMR.

Synthesis and Characterization of Nanocomposites Based on Functional Regioregular Poly(3-hexylthiophene) and Multiwall Carbon Nanotubes.

New functionalized poly(3-hexylthiophene)s (P3HT) have been designed and synthesized with the aim of increasing the dispersion of carbon nanotubes (CNT) in solutions and in thin films of semiconducting polymers. Dispersion in solution has been assessed by sedimentation tests while the thin film morphology has been analyzed by TEM and AFM. Both the physisorption of P3HT chains (via pyrene end-groups) or their chemical grafting (onto amine functions generated on the CNT surface) lead to a much better dispersion in solution and in the solid. In thin films, P3HT fibrils are observed to arrange perpendicular to the CNT surface, which can be understood on the basis of molecular modeling simulations. Finally, the effect of dispersing those P3HT/CNT nanocomposites in bulk-heterojunction P3HT-based photovoltaic devices has been evaluated.

Aromatic Nucleophilic Substitution (SNAr) of meso-Nitroporphyrin with Azide and Amines as an Alternative Metal Catalyst Free Synthetic Approach To Obtain meso-N-Substituted Porphyrins

Aromatic nucleophilic substitution reaction of the nitro group of meso-nitroporphyrins with azide and various amines was achieved and represents an alternative procedure to C-N coupling reactions usually needed to obtain such meso-N-substituted porphyrins in good yields.

Synthesis and characterisation of π-conjugated polymer/silica hybrids containing regioregular ionic polythiophenes

Highly regioregular poly{3-[n-(1-methylimidazolium-3-yl)alkyl]thiophene-2,5-diyl bromide} (n = 4, 6, 8) (10–12) has been prepared by reaction of poly[3-(n-bromoalkyl)thiophene-2,5-diyl] (n = 4, 6, 8) (7–9) with 1-methylimidazole. Acid-catalyzed hydrolysis and polycondensation of tetraethoxysilane (TEOS) were carried out in the presence of these polymers. The strong ionic interactions between the imidazolium moieties of the polythiophene and the charged silanol groups enabled the homogeneous dispersion of the polythiophene within silica. The resulting composite materials were characterised by SEM, TEM and tapping mode atomic force microscopy (TM-AFM). The optical and thermal properties were investigated by UV and TGA measurements.

Probing excited state electronic communications across diethynyl-[2.2]paracyclophane-containing conjugated organometallic polymers

The triplet k(ET) for three organometallic polymers built upon the diethynyl[2.2]paracyclophane was studied to show good excited state electronic communication across the materials.

High-Permittivity Conjugated Polyelectrolyte Interlayers for High-Performance Bulk Heterojunction Organic Solar Cells

Conjugated polyelectrolyte (CPE) interfacial layers present a powerful way to boost the I-V characteristics of organic photovoltaics. Nevertheless, clear guidelines with respect to the structure of high-performance interlayers are still lacking. In this work, impedance spectroscopy is applied to probe the dielectric permittivity of a series of polythiophene-based CPEs. The presence of ionic pendant groups grants the formation of a capacitive double layer, boosting the charge extraction and device efficiency. A counteracting effect is the diminishing affinity with the underlying photoactive layer. To balance these two effects, we found copolymer structures containing nonionic side chains to be beneficial.

Binding modes of a core-extended metalloporphyrin to human telomeric DNA G-quadruplexes.

The molecular recognition of human telomeric G-quadruplexes by a novel cationic π-extended Ni(II)-porphyrin (Ni(II)-TImidP4) is studied in aqueous solutions via (chir)optical spectroscopy, Fluorescence Resonance Energy Transfer (FRET) melting assay, and computational molecular modeling. The results are systematically compared with the recognition by a conventional meso-substituted Ni(II)-porphyrin (Ni(II)-TMPyP4), which allows us to pinpoint the differences in binding modes depending on the G-quadruplex topology. Importantly, FRET melting assays show the higher selectivity of Ni(II)-TImidP4 towards human telomeric G4 than that of Ni(II)-TMPyP4.

All-conjugated cationic copolythiophene “rod–rod” block copolyelectrolytes: synthesis, optical properties and solvent-dependent assembly

Amphiphilic diblock copolythiophenes were synthesised by an efficient two-step strategy. The diblock copolyelectrolytes were obtained via quasi-living Kumada catalyst-transfer polycondensation followed by quaternisation of the bromohexyl side chains of one of the monomer constituents into N-methylimidazolium, pyridinium, trimethylammonium or trimethylphosphonium units. The effect of the nature of the charged group on the thermal properties was investigated by Rapid Heat–Cool (RHC) calorimetry measurements. The solvent-driven assembly of these block copolyelectrolytes in chloroform (CHCl3), water, methanol (MeOH), water–MeOH mixtures and in subsequently prepared thin films was investigated using a combination of photoluminescence, scattering and microscopic techniques. The rigid rod-structure of the block copolyelectrolytes led to the formation of core–shell cylindrical or disc-like aggregates in solution, with features determined by the nature of the solvent. AFM studies revealed that the aggregates formed in solution can be transferred into thin films allowing for the reliable control of the self-organisation process and the resulting nanoscale architecture.

Porphyrins fused to N-heterocyclic carbenes (NHCs): modulation of the electronic and catalytic properties of NHCs by the central metal of the porphyrin.

We report herein a detailed study of the use of porphyrins fused to imidazolium salts as precursors of N-heterocyclic carbene ligands 1 M. Rhodium(I) complexes 6 M-9 M were prepared by using 1 M ligands with different metal cations in the inner core of the porphyrin (M=Ni(II) , Zn(II) , Mn(III) , Al(III) , 2H). The electronic properties of the corresponding N-heterocyclic carbene ligands were investigated by monitoring the spectroscopic changes occurring in the cod and CO ancillary ligands of [(1 M)Rh(cod)Cl] and [(1 M)Rh(CO)2 Cl] complexes (cod=1,5-cyclooctadiene). Porphyrin-NHC ligands 1 M with a trivalent metal cation such as Mn(III) and Al(III) are overall poorer electron donors than porphyrin-NHC ligands with no metal cation or incorporating a divalent metal cation such as Ni(II) and Zn(II) . Imidazolium salts 3 M (M=Ni, Zn, Mn, 2H) have also been used as NHC precursors to catalyze the ring-opening polymerization of L-lactide. The results clearly show that the inner metal of the porphyrin has an important effect on the reactivity of the outer carbene.