SummaryIn the present paper, the photoredox catalysis is presented as a unique approach in the field of photoinitiators of polymerization. The principal photocatalysts already reported as well as the typical oxidation and reduction agents used in both reductive or oxidative cycles are gathered. The chemical mechanisms associated with various systems are also given. As compared to classical iridium-based photocatalysts which are mainly active upon blue light irradiation, a new photocatalyst Ir(piq)2(tmd) (also known as bis(1-phenylisoquinolinato-N,C 2’)iridium(2,2,6,6-tetramethyl-3,5-heptanedionate) is also proposed as an example of green light photocatalyst (toward the long wavelength irradiation). The chemical mechanisms associated with Ir(piq)2(tmd) are investigated by ESR spin-trapping, laser flash photolysis, steady state photolysis, cyclic voltammetry and luminescence experiments.

A series of cationic diiminoiridium(III) complexes [Ir(ppy‐N,C)2(L‐N,N)](PF6) has been prepared [Hppy = 2‐phenylpyridine; L = 4,4′‐tBu2dpbpy (1), 4,4′‐Me2dpbpy (2), 4,4′‐Me2pbpy (3), 4,4′‐Me2bpy (4)] and their photophysical and electrochemical properties studied. X‐ray diffraction studies of complex 1 reveal a dihedral angle of about 33° between the pyridine rings, and that the two phenyl groups are also tilted with respect to the adjacent pyridine rings. All the complexes exhibit moderately intense and long‐lived emission. The origin of the emission is tentatively assigned to a triplet metal‐to‐ligand charge‐transfer 3MLCT [dπ(Ir) → π*(diimine)] excited state, although the possibility of a triplet σ‐bond‐to‐ligand charge transfer 3SBLCT [σ(Ir−C) → π*(diimine)] cannot be excluded. The luminescence properties of the complexes are dependent on the substituents on the diimine ligands. Selective N‐methylation of the diimine ligands has been achieved and their N,C‐coordination to the Ir centre has been attempted. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

A new class of heteroacenes containing B, N and S elements in the 22-electron aromatic nucleus has been synthesized by reaction of diaminoterthiophenes with dichlorophenylborane. Their structure was studied by X-ray crystallography and DFT calculations. UV-Vis absorption /emission spectroscopy shows high rigidity and deep-blue fluorescence of these compounds.

International audienceA new iridium complex (nIr) was designed and investigated as a photoinitiator catalyst for radical and cationic polymerizations upon very soft irradiations (lights ranging from 457 to 532 nm). A ring-opening polymerization (ROP) of an epoxy monomer was easily promoted through the interaction between nIr and an iodonium salt (Iod) upon light. The addition of N-vinylcarbazole (NVK) enhances the performance. In radical polymerization, nIr can be efficient in combination with phenacyl bromide (PBr) and optionally an amine: these photoinitiating systems work according to an original oxidative cycle and a regeneration of nIr is observed. A control of the methyl methacrylate polymerization (conducted under a 462 nm light) with 1.2–1.6 polydispersity indexes was displayed. Surface modifications by direct laser write was also easily carried out for the first time through surface re-initiation experiments, i.e. the dormant species being reactivated by light in the presence of nIr; the polymer surfaces were analyzed by XPS. The chemical mechanisms were examined through laser flash photolysis, NMR, ESR and size exclusion chromatography experiment

A series of 18 iridium complexes (Ir) have been prepared and studied. Their abilities to initiate both a ring‐opening cationic polymerization (CP) using an Ir/iodonium salt couple and a free radical polymerization (FRP) in the presence of an Ir/amine/alkyl halide system under very soft irradiation (i.e., halogen lamp) or upon exposure to laser diodes @457 nm and @532 nm are investigated. Interestingly, these photoinitiating systems operate through an oxidative or a reductive photoredox catalytic cycle, respectively. Excellent polymerization profiles are obtained (reactive function conversions >70% for the CP of an epoxide and >60% for the FRP of low viscosity triacrylate). The photochemical mechanisms are studied by fluorescence, steady state photolysis, cyclic voltammetry, and electron spin resonance spin trapping experiments.

International audienceSTM Observation of Open- and Closed-Ring Forms of Functionalized Diarylethene Molecules Self-Assembled on a Au(111) Surface Abstract HTMLFull Text HTML PDFHi-Res PDF[3988 KB] PDFPDF w/ Links[782 KB] Supporting Info Figures Your current credentials do not allow retrieval of the full text. Purchase the full-text Cart PDF/HTML, figures/images, references and tables, (where available) PDF Sergii V. Snegir†‡||, Alexandr A. Marchenko§, Pei Yu, Francois Maurel#, Oleksiy L. Kapitanchuk, Sandra Mazerat, Marc Lepeltier, Anne Léaustic, and Emmanuelle Lacaze*†|| Institut des NanoSciences de Paris (INSP), CNRS, 4 place Jussieu, 75251 Paris, France Institut des NanoSciences de Paris (INSP), UPMC Université Paris 6, 4 place Jussieu, 75251 Paris, France ‡Chuiko Institute of Surface Chemistry, §Institute of Physics, and Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Kyiv, Ukraine Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182, Université Paris Sud 11, 91405 Orsay, France Univ Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR CNRS 7086, 15 rue J-A de Baïf, 75205 Paris Cedex 13, France J. Phys. Chem. Lett., 2011, 2 (19), pp 2433-2436 DOI: 10.1021/jz200875c Publication Date (Web): August 24, 2011 Copyright © 2011 American Chemical Society E-mail: Emmanuelle.lacaze@insp.jussieu.fr. CASSection: Surface Chemistry and Colloids Abstract Abstract Image Ordered self-assembled monolayers (SAMs) of thiolated diarylethene photochromic molecules have been built on a Au(111) surface and characterized by mean of scanning tunneling microscopy (STM) for the first time. It has been revealed that molecules deposited from UV-illuminated (closed-ring isomer) and initial solutions (open-ring isomer) both occupy 4 × 2√3 adsorption sites on Au(111) and present a conformation where conjugated parts are parallel to the surface, forming "umbrella-like" structure. On the basis of the distances measured from STM images with intramolecular resolution and on quantum chemical DFT calculations of electronic structure for single molecules, an identical model of molecular packing with a 4 × 4√3 unit cell is proposed for both isomers. The variation of internal orbitals between open- and closed-ring isomers leads to significant change of STM contrast, allowing direct identification of each diarylethene isomer using STM images

A new series of tris-cyclometalated Ir(III) styryl complexes and their saturated analogues have been synthesized; the former are formed by functionalization of Ir(4-Me-ppy) 3 and the latter from a hydrogen transfer process to the styryl groups. Their luminescence properties have been investigated.

International audienceGold and silver nanoparticles in the 5 nm range functionalized by luminescent and electroactive iridium complexes are synthesized and characterized. Cyclometalated iridium complexes with a modified phenanthroline ligand bearing a pyridine end group are able to cap gold nanoparticles without changing their size and shape, while for silver the size slightly increases and aggregation starts to occur but without any flocculation. The luminescence of iridium is partially quenched by gold nano- particles even when interactions with the complex do not involve surface functionalization (simple mixture). This quenching is much weaker in the case of silver, and capped nanoparticles retain the same luminescence as the free complex. Both iridium complexes display electrofluorochromism, that is, a reversible electrochemically driven luminescence switch when changing the redox state of the metal center