A Direct Method for Oxidizing Quinoxaline, Tetraazaphenanthrene, and Hexaazatriphenylene Moieties Using Hypervalent λ³‑Iodinane Compounds

An efficient oxidation reaction of various electron-poor quinoxaline-core-containing compounds, such as quinoxalines, 1,4,5,8-tetraazaphenanthrenes, and 1,4,5,8,9,12-hexaazatriphenylene, using [bis­(trifluoroacetoxy)­iodo]­benzene is reported. These compounds are converted into the corresponding quinoxalinediones in good to high yields at room temperature using an acetonitrile/water solvent mixture. This unprecedented reaction should enable the synthesis of a wide variety of compounds useful in several fields of chemistry

Influence of the Grafting Density on the Self-Assembly in Poly(phenylene­ethynylene)‑<i>g</i>‑poly(3-hexyl­thiophene) Graft Copolymers

Conjugated graft copolymers consisting of a chiral poly­(phenylene­ethynylene) (PPE) backbone and poly­(3-hexyl­thiophene) side chains (P3HT) with different grafting degrees were synthesized. While PPE was prepared by classical Sonogashira couplings, the end-functionalized P3HT was prepared by a controlled Kumada catalyst transfer polycondensation (KCTP) allowing the installation of an acetylene end group. After some postpolymerization reactions on the PPE to introduce azide groups, the P3HT was clicked to the PPE through the CuAAC coupling reaction. Subsequently, the (chiral) self-assembly of these materials was studied by means of UV–vis and CD spectroscopy, AFM, and DSC. Finally, fluorescence spectroscopy is used to study the quenching of the PPE fluorescence by P3HT

Influence of Structure of End-Group-Functionalized Poly(3-hexylthiophene) and Poly(3-octylselenophene) Anchored on Au Nanoparticles

Different protected thiol-functionalized initiators were prepared and used to polymerize end-functionalized poly­(3-hexylthiophene)­s in which the spacer between the thiol and the P3HT chain is varied. The protected thiol P3HTs were in situ deprotected and anchored onto Au nanoparticles (NPs) to form P3HT/Au hybrids. The influence of the length of the linker between the P3HT and the Au NP surface on the fluorescence quenching was investigated. The strongest quenching was observed for the shortest linkers. Also, a protected thiol poly­(3-octylselenophene) (P3OS) was polymerized and anchored together and separately with P3HT to a Au NP. The effect of the presence of P3OS on the quenching was investigated, and an additional quenching was observed when P3OS is anchored on the same NP as P3HT. For all polymers, ¹H NMR and MALDI-ToF analysis confirmed the successful functionalization and strong control over the polymerization

Synthesis of End-Group Functionalized P3HT: General Protocol for P3HT/Nanoparticle Hybrids

Poly­(3-hexylthiophene)­s were synthesized with phosphonic ester, pyridine, thiol, and phenol end-groups using functionalized air-stable Ni initiators. The protected thiol- and phenol-functionalized P3HTs were converted into thiol and phenol P3HTs by quantitative postpolymerization reactions. ¹H NMR and MALDI–ToF analysis showed very high degrees of functionalization and strong control over the polymerization except for the pyridine functionalized P3HT. These functional end-groups were used to prepare hybrid materials from a broad variety of nanoparticles, including metal oxides, quantum dots, and noble metals

Trifluoromethyl-Substituted Iridium(III) Complexes: From Photophysics to Photooxidation of a Biological Target

Photodynamic therapeutic agents are of key interest in developing new strategies to develop more specific and efficient anticancer treatments. In comparison to classical chemotherapeutic agents, the activity of photodynamic therapeutic compounds can be finely controlled thanks to the light triggering of their photoreactivity. The development of type I photosensitizing agents, which do not rely on the production of ROS, is highly desirable. In this context, we developed new iridium­(III) complexes which are able to photoreact with biomolecules; namely, our Ir­(III) complexes can oxidize guanine residues under visible light irradiation. We report the synthesis and extensive photophysical characterization of four new Ir­(III) complexes, [Ir­(ppyCF₃)₂(N^N)]⁺ [ppyCF₃ = 2-(3,5-bis­(trifluoromethyl)­phenyl)­pyridine) and N^N = 2,2′-dipyridyl (bpy); 2-(pyridin-2-yl)­pyrazine (pzpy); 2,2′-bipyrazine (bpz); 1,4,5,8-tetraazaphenanthrene (TAP)]. In addition to an extensive experimental and theoretical study of the photophysics of these complexes, we characterize their photoreactivity toward model redox-active targets and the relevant biological target, the guanine base. We demonstrate that photoinduced electron transfer takes place between the excited Ir­(III) complex and guanine which leads to the formation of stable photoproducts, indicating that the targeted guanine is irreversibly damaged. These results pave the way to the elaboration of new type I photosensitizers for targeting cancerous cells

Design of Multistimuli-Responsive Shape-Memory Polymer Materials by Reactive Extrusion

Shape-memory polymers (SMPs) are a class of stimuli-responsive materials that have attracted tremendous attention in various applications, especially in the medical field. While most SMPs are thermally actuated, relating to a change of thermal transition (e.g., melting temperature), SMPs that can be actuated upon exposure to light are emerging. Recently, there has been new interest into multiple stimuli-responsive SMPs in order to cover the range of applications for these smart materials. In this work, poly­(ester-urethane)­s (PURs) made of heating-responsive poly­(ε-caprolactone) (PCL) segments of various degrees of crystallinity and photoresponsive <i>N</i>,<i>N</i>-bis­(2-hydroxyethyl) cinnamide (BHECA) monomer were successfully prepared using reactive extrusion technology to design dual-stimuli-responsive SMPs (DSRSMP). In order to tune the SMP properties (temperature or light), the crystallinity of the PCL segment was finely adjusted by the copolymerization of ε-caprolactone with para-dioxanone in bulk at 160 °C using tin­(II) octoate. The resulting polyester segments were then coupled with BHECA using <i>n</i>-octyl diisocyanate at 130 °C. The SMP properties of resulting PURs were correlated with DSC and DMTA measurements. Further addition of di- and tetracinnamate PCL segments into these SMPs was also studied in order to enhance the photoactuated SMP properties

Meisenheimer Complex Inspired Catalyst- and Solvent-Free Synthesis of Noncyclic Poly(aryl ether sulfone)s

Identifying solvent- and catalyst-free conditions for polymerizations of engineering thermoplastics is of increasing interest due to new polymer processing technologies such as 3-D printing. We report the selective formation of linear poly­(aryl ether sulfone)­s (PESs) from the polycondensation of trimethylsilyl-protected bisphenol A (TMS-BPA) with nitro-substituted diaryl fluorides without added solvent or catalyst. DFT calculations show that nitro groups strategically placed in the <i>ortho</i>-position to the fluoride leaving group form a stable Meisenheimer complex during polyether synthesis. This strategy represents a route to linear PESs that employs anionic conditions, destabilizing propagating phenoxide chain ends preventing backbiting while simultaneously stabilizing the Meisenheimer complex intermediate. Thermodynamic over kinetic control in the polycondensation minimizes cyclic PES formation and promotes the formation of pure linear PESs