The Role of a Confined Space on the Reactivity and Emission Properties of Copper(I) Clusters.

Metal clusters have gained a lot of interest for their remarkable photoluminescence and catalytic properties. However, a major drawback of such materials is their poor stability in air and humidity conditions. Herein we describe a versatile method to synthesize luminescent Cu(I) clusters inside the pores of zeolites, using a sublimation technique with the help of high vacuum and high temperature. The porous materials play an essential role as a protecting media against the undesirable and easy oxidation of Cu(I). The obtained clusters show fascinating luminescence properties, and their reactivity can be triggered by insertion in the pores of organic monodentate ligands such as pyridine or triphenylphosphine. The coordinating ligands can lead to the formation of Cu(I) complexes with completely different emission properties. In the case of pyridine, the final compound was characterized and identified as a cubane-like structure. A thermochromism effect is also observed, featuring, for instance, a hypsochromic effect for a phosphine derivative at 77K. The stability of the encapsulated systems in zeolites is rather enthralling: they are stable and emissive even after several months in the air.

Cationic iridium(III) complexes bearing ancillary 2,5-dipyridyl(pyrazine) (2,5-dpp) and 2,2':5',2''-terpyridine (2,5-tpy) ligands: synthesis, optoelectronic characterization and light-emitting electrochemical cells.

Four cationic iridium(III) complexes of the form [Ir(C^N)2(N^N)](+) bearing either a 2,5-dipyridylpyrazine (2,5-dpp) or a 2,2':5',2''-terpyridine (2,5-tpy) ancillary ligand and either 2-phenylpyridine (ppy) or a 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppy) cyclometalating ligands were synthesized. The optoelectronic properties of all complexes have been fully characterized by UV-visible absorption, cyclic voltammetry and emission spectroscopy. The conclusions drawn from these studies have been corroborated by DFT and TDDFT calculations. The four complexes were assessed as emitters in light-emitting electrochemical cells. Complex 1a, [Ir(ppy)2(2,5-dpp)]PF6, was found to be a deep red emitter (666 nm) both in acetonitrile solution and in the electroluminescent device. Complex 2a, [Ir(ppy)2(2,5-tpy)]PF6 was found to be an orange emitter (604 nm) both in solution and in the LEEC. LEECs incorporating both of these complexes were stable over the course of around 4-6 hours. Complex 1b, [Ir(dFMeppy)2(2,5-dpp)]PF6, was also determined to emit in the orange (605 nm) but with a photoluminescent quantum yield (ΦPL) double that of 2a. Complex 2b, [Ir(dFMeppy)2(2,5-tpy)]PF6 is an extremely bright green emitter (544 nm, 93%). All four complexes exhibited quasireversible electrochemistry and all four complexes phosphoresce from a mixed charge-transfer excited state.

Dual photosensitive polymers with wavelength-selective photoresponse.

Polyurethane thin films that photopolymerize and photodegrade upon exposure to light of different wavelengths are presented. The chromic response is based on two caged monomers with the ability to be activated or photocleaved with different wavelengths under single and two-photon excitation. This material represents a dual photoresist with "positive" and "negative" tone contained in a single resist formulation and with the ability to generate complex 2D and 3D patterns.

Mono- and dinuclear cationic iridium(III) complexes bearing a 2,5-dipyridylpyrazine (2,5-dpp) ligand.

The synthesis, X-ray structures, photophysical, and electrochemical characterization of mono- (1) and dinuclear (2) cationic iridium(III) complexes bearing a 2,5-dipyridylpyrazine (2,5-dpp) ancillary ligand are reported. Upon the complexation of a first equivalent of iridium, the photoluminescence shifts markedly into the deep red (λem = 710 nm, ΦPL = 0.9%) compared to other cationic iridium complexes such as [Ir(ppy)2(bpy)]PF6. With the coordination of a second equivalent of iridium, room temperature luminescence is completely quenched. Both 1 and 2 are luminescent at low temperatures but with distinct excited state decay kinetics; the emission of 2 is significantly red-shifted compared to 1. Emission both at 298 and 77 K results from a mixed charge-transfer state. Density functional theory (DFT) calculations and electrochemical behavior point to an electronic communication between the two iridium complexes.

A rare case of dual emission in a neutral heteroleptic iridium(III) complex.

Herein we describe the synthesis and characterization of a neutral heteroleptic iridium complex bearing an unusual 2-pyridyl-6-methylthiazine dioxide ligand (pythdo). X-ray crystallographic analysis reveals that in the complex, the pythdo ligand is twisted and puckered, resulting in very low photoluminescent quantum efficiency. The emission profile is structured. Excited state lifetime measurements along with oxygen quenching studies point to a rare case of dual emission from different excited states whereby the high energy bands possess significant ligand-centered ((3)LC) character while the lower energy bands are predominantly characterized as a mixture of charge transfer ((3)CT) states. A detailed computational analysis corroborates the unusual photophysical behavior.

Cationic iridium(III) complexes bearing a bis(triazole) ancillary ligand.

Three new heteroleptic cationic iridium complexes of the form [Ir(C^N)(btl)](+), where btl = 1,1'-benzyl-4,4'-bi-1H-1,2,3-triazolyl and C^N = 2-phenylpyridine (ppyH) (1), 1-benzyl-4-phenyl-1H-1,2,3-triazole (phtl) (2) or 1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole (dFphtl) (3), were synthesized and isolated as their hexafluorophosphate (PF6(-)) salts and fully characterized. The single crystal structure of 3 has been solved. Along the series from 1-3 the absorption spectra shift hypsochromically while the electrochemical gap increases from 3.25 to 3.54 to 3.88 V. Acetonitrile solutions of 1 and 2 are poorly luminescent, sky-blue emitters with predominant ligand-centered and charge transfer character, respectively. Theoretical calculations support these assignments. Complex 3 is not photostable and decomposes to solvento-based structures of the form [Ir(dFphtl)2(ACN)n](+) (n = 1, 2) through a dissociation and degradation of the btl ligand.

The donor-acceptor biphenyl platform: a versatile chromophore for the engineering of highly efficient two-photon sensitive photoremovable protecting groups.

Different photoremovable protecting groups in the o-nitrobenzyl, phenacyl, and 2-(o-nitrophenyl)propyl series with a donor-acceptor biphenyl backbone, known to display excellent two-photon absorption cross-sections, were investigated in order to develop efficient two-photon sensitive photoremovable protecting groups. The 2-(o-nitrophenyl)propyl series was a more versatile platform to increase the two-photon sensitivity of photoremovable protecting groups, leading to the p-alkoxy and p-bisalkylamino-4-nitro-[1,1'-biphenyl]-3-yl)propyl derivatives: PENB and EANBP respectively. Those two photoremovable protecting groups are to date the best caging groups for two-photon excitation at 800 and 740 nm respectively, offering attracting perspectives in chemical biology.