Benzothiadiazole-Substituted Aza-BODIPY Dyes: Two-Photon Absorption Enhancement for Improved Optical Limiting Performances in the Short-Wave IR Range

Aza-boron dipyrromethenes (aza-BODIPYs) presenting a benzothiadiazole substitution on upper positions are described. The strong electron-withdrawing effect of the benzothiadiazole moiety permits enhancement of the accepting strength and improves the delocalization of the aza-BODIPY core to attain a significant degree of electronic communication between the lower donating groups and the upper accepting groups. The nature of the intramolecular charge transfer is studied both experimentally and theoretically. Linear spectroscopy highlighted the strongly redshifted absorption and emission of the synthesized molecules with recorded fluorescence spectra over 1000 nm. Nonlinear optical properties were also investigated. Strong enhancement of the two-photon absorption of the substituted dyes compared with the unsubstituted one (up to 4520 GM at 1300 nm) results in an approximately 15–20 % improvement of the optical power limiting performances. These dyes are therefore a good starting point for further improvement of optical power limiting in the short-wave IR range.     

Tris(trichlorosilyl)tetrelide Anions and a Comparative Study of Their Donor Qualities

Trichlorosilylated tetrelides [(Cl₃Si)₃E]⁻ have been prepared by adding 1 equiv of a soluble Cl⁻ salt to (Cl₃Si)₄Si (E=Si) or 4 Si₂Cl₆/GeCl₄ (E=Ge). To assess their donor qualities, the anions [(Cl₃Si)₃E]⁻ (E=C, Si, Ge) have been treated with BCl₃, AlCl₃, and GaCl₃. Both BCl₃ and GaCl₃ give 1:1 adducts with the anionic centers. AlCl₃ leads to Cl⁻ abstraction from [(Cl₃Si)₃E]⁻ with formation of (Cl₃Si)₄E (E=Si or Ge). (Cl₃Si)₄Ge is cleanly converted to the perhydrogenated (H₃Si)₄Ge by use of Li[AlH₄]. Another case of Cl⁻ abstraction was observed for [(Cl₃Si)₃Ge ⋅ GaCl₃]⁻, which reacts with GaCl₃ to afford the neutral dimer [(Cl₃Si)₃Ge−GaCl₂]₂.     

An improved singlet oxygen sensitizer with two-photon absorption and emission in the biological transparency window as a result of ground state symmetry-breaking

A chromophore featuring a diyne bridge that connects two dibromobenzene moieties shows a much improved two-photon singlet oxygen generation ability in the biological transparency window compared to a related and relevant literature benchmark, as a result of a distorted ground state.     

Synthesis of chiral ionic liquids by ion cross-metathesis: en route to enantioselective water-ionic liquid extraction (EWILE), an eco-friendly variant of the ELLE process

From two initial ILs two other ILs are obtained by simultaneous ion exchange. The hydrophobic ions unite in the hydrophobic layer, whereas the hydrophilic ions gather in water. This protocol is explored as a variant of the ELLE process, in which an enantiomer of a racemic mixture is preferentially extracted with water.     

New probing techniques of radiative shocks

Radiative shock waves propagating in xenon at a low pressure have been produced using 60 joules of iodine laser (λ = 1.315 μm) at PALS center. The shocks have been probed by XUV imaging using a Zn X-raylaser (λ = 21 nm) generated with a 20-ns delay after the shock creating pulse. Auxiliary high-speed silicon diodes allowed performing space- and time-resolved measurement of plasma self-emission in the visible and XUV. The results show the generation of a shock wave propagating at 60 km/s preceded by a radiative precursor. This demonstrates the feasibility of radiative shock generation using high power infrared lasers and the use of XRL backlighting as a suitable diagnostic for shock imaging.     

Essential oil of Plectranthus tenuicaulis leaves from Gabon, source of (R),(E)-6,7-epoxyocimene. An unusual chemical composition within the genus Plectranthus

Water distilled essential oils from leaves of Plectranthus tenuicaulis (Hook. f.) J. K. Morton collected in Gabon were analyzed using GC-FID and GC-MS. The main constituent, unusual within the genus Plectranthus, was isolated and formally identified as being the (+)-(R)-enantiomer of (E)-6,7-epoxyocimene [(E)-myroxide]. This enantiomer, which represents about 75% of the essential oil, has been previously identified as a pheromone emitted by the male fruit-spotting bug Amblypelta nitida; this insect is responsible of destruction of most fruit crops in tropical and subtropical areas. The potential application of P. tenuicaulis essential oil in crop protection programs is discussed and the atypical chemical profile of the gabonese essential oil is compared with those previously reported in the genus Plectranthus (or Coleus).     

Histidinylated linear PEI: a new efficient non-toxic polymer for gene transfer

A series of linear polyethylenimine (lPEI) substituted with histidine residue (His-lPEI) was synthesized using the Michael reaction in order to provide new highly efficient vectors for gene therapy applications (up to 95% of transfected cells) with remarkable low cytotoxicity compared to lPEI-based polyplexes.     

Azide‐functionalized nanoparticles as quantized building block for the design of soft–soft fluorescent polystyrene core—PAMAM shell nanostructures

This work deals with the covalent coupling of azide‐functionalized polymeric nanoparticles as a reactive core and amino‐terminated PAMAM dendrons as a reactive shell. The nanoassemblies thereby obtained could be modified after the dendronization step by grafting an alkynyl Bodipy dye on the unreacted azide moieties. Only a few steps are required to attain nanoassemblies that could mimic dendrimers of high generation with sizes of nano‐objects beyond those of dendrimers. The structure of the nanoassemblies are composed of a polystyrene core, an inner shell including the Bodipy dyes along with the internal branches of the PAMAM, and the terminal amino groups from the outer shell. The dendritic shell acts as a protective layer that prevents NP from aggregation in a surfactant free aqueous solution. The nano‐objects display absorption and emission maxima above 500 nm with brightness that are the same order of magnitude than Qdots. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 115–126     

Boron Difluoride Curcuminoid Fluorophores with Enhanced Two‐Photon Excited Fluorescence Emission and Versatile Living‐Cell Imaging Properties

The synthesis of boron difluoride complexes of a series of curcuminoid derivatives containing various donor end groups is described. Time‐dependent (TD)‐DFT calculations confirm the charge‐transfer character of the second lowest‐energy transition band and ascribe the lowest energy band to a “cyanine‐like” transition. Photophysical studies reveal that tuning the donor strength of the end groups allows covering a broad spectral range, from the visible to the NIR region, of the UV–visible absorption and fluorescence spectra. Two‐photon‐excited fluorescence and Z‐scan techniques prove that an increase in the donor strength or in the rigidity of the backbone results in a considerable increase in the two‐photon cross section, reaching 5000 GM, with predominant two‐photon absorption from the S₀–S₂ charge‐transfer transition. Direct comparisons with the hemicurcuminoid derivatives show that the two‐photon active band for the curcuminoid derivatives has the same intramolecular charge‐transfer character and therefore arises from a dipolar structure. Overall, this structure–relationship study allows the optimization of the two‐photon brightness (i.e., 400–900 GM) with one dye that emits in the NIR region of the spectrum. In addition, these dyes demonstrate high intracellular uptake efficiency in Cos7 cells with emission in the visible region, which is further improved by using porous silica nanoparticles as dye vehicles for the imaging of two mammalian carcinoma cells type based on NIR fluorescence emission.