Circularly Polarized Luminescence from Helically Chiral N,N,O,O-Boron-Chelated Dipyrromethenes.

Helically chiral N,N,O,O-boron chelated dipyrromethenes showed solution-phase circularly polarized luminescence (CPL) in the red region of the visible spectrum (λem (max) from 621 to 663 nm). The parent dipyrromethene is desymmetrised through O chelation of boron by the 3,5-ortho-phenolic substituents, inducing a helical chirality in the fluorophore. The combination of high luminescence dissymmetry factors (|glum | up to 4.7 ×10(-3) ) and fluorescence quantum yields (ΦF up to 0.73) gave exceptionally efficient circularly polarized red emission from these simple small organic fluorophores, enabling future application in CPL-based bioimaging.

Fluorescent molecular rotors based on the BODIPY motif: effect of remote substituents.

The ability of an unconstrained boron dipyrromethene dye to report on changes in local viscosity is improved by appending a single aryl ring at the lower rim of the dipyrrin core. Recovering the symmetry by attaching an identical aryl ring on the opposite side of the lower rim greatly diminishes the sensory activity, as does blocking rotation of the meso-aryl group. On the basis of viscosity- and temperature-dependence studies, together with quantum chemical calculations, it is proposed that a single aryl ring at the 3-position extends the molecular surface area that undergoes structural distortion during internal rotation. The substitution pattern at the lower rim also affects the harmonic frequencies at the bottom of the potential well and at the top of the barrier. These effects can be correlated with the separation of the H1,H7 hydrogen atoms.

High-performance solution-processed solar cells and ambipolar behavior in organic field-effect transistors with thienyl-BODIPY scaffoldings.

Green-absorbing dipyrromethene dyes engineered from bis-vinyl-thienyl modules are planar molecules, exhibiting strong absorption in the 713-724 nm range and displaying comparable electron and hole mobilities in thin films (maximum value 1 × 10(-3) cm(2)/(V·s)). Bulk heterojunction solar cells assembled with these dyes and a fullerene derivative (PC(61)BM) at a low ratio give a power conversion efficiency as high as 4.7%, with short-circuit current values of 14.2 mA/cm(2), open-circuit voltage of 0.7 V, and a broad external quantum efficiency ranging from 350 to 920 nm with a maximum value of 60%.

Synthetic routes to fluorescent dyes exhibiting large Stokes shifts.

Derivatives of isomeric 2-(hydroxytolyl)-4,6-dimethylamino-1,3,5-triazines have been synthesized in high yields in a controlled manner using a multistep reaction sequence. Iodination of either 2-(1'-hydroxy-6'-methylphen-2'-yl)- or 2-(1'-hydroxy-4'-methylphen-2'-yl)-4,6-dimethylamino-1,3,5-triazine with ICl provides species differing in the positioning of the iodo group relative to the hydroxyl which readily undergo Suzuki, Sonogashira, and Heck reactions under Pd(0) catalysis. Thus, thienyl, bisthienyl, and 3,4-ethylenedioxythienyl groups have been directly grafted, while unsubstituted polycyclic aromatics such as pyrene and perylene have been linked via alkyne bridges, as have ethynyldifluoroborondipyrromethane (BODIPY) dyes prepared in situ. The presence of a hydrogen bond in the ground state involving the hydroxyl substituent has been established by proton NMR and several X-ray structure determinations. All of the new dyes with a simple substituent (phenyl, thienyl) exhibited a pronounced green fluorescence resulting from an intramolecular proton transfer in the excited state (ESIPT) which produces a large Stokes shift (>10,000 cm(-1)). With other dyes, the fluorescence of the keto form responsible for the ESIPT process could be used as the input energy in efficient intramolecular energy transfer processes. Replacing perylene with pyrene allowed reversal of the direction of energy transfer from the polyaromatic module to the keto form.

Quasi-one-dimensional electronic systems formed from boron dipyrromethene (BODIPY) dyes.

Synthetic strategies have been devised that allow the rational design and isolation of highly coloured boron dipyrromethene (BODIPY) dyes that absorb across much of the visible region. Each dye has an aryl polycycle (usually pyrene or perylene) connected to the central BODIPY core through a conjugated tether at the 3,5-positions. Both mono- and difunctionalised derivatives are accessible, in certain cases containing both pyrene and perylene residues. For all new compounds, the photophysical properties have been recorded in solution at ambient temperature and in a glassy matrix at 77 K. The presence of the aryl polycycle(s) affects the absorption and emission maxima of the BODIPY nucleus, thereby confirming that these units are coupled electronically. Indeed, the band maxima and oscillator strengths depend on the conjugation length of the entire molecule, whereas there is no sign of fluorescence from the polycycle. As a consequence, the radiative rate constant tends to increase with each added appendage. The nature of the linkage (styryl, ethenyl, or ethynyl) also exerts an effect on the photophysical properties and, in particular, the absorption spectrum is perturbed in the region of the aryl polycycle. The perylene-containing BODIPY derivatives absorb over a wide spectral range and emit in the far-red region in almost quantitative yield. A notable exception to this generic behaviour is provided by the anthracenyl derivative, which exhibits charge-transfer absorption and emission spectra in weakly polar media at ambient temperature. Regular BODIPY-like behaviour is restored in a glassy matrix at 77 K. Overall, these new dyes represent an important addition to the range of strongly absorbing and emitting reagents that could be used as solar concentrators.

Phenyliodine(III) bis(trifluoroacetate) (PIFA)-promoted synthesis of Bodipy dimers displaying unusual redox properties.

Phenyliodine(III) bis(trifluoroacetate) (PIFA) in conjunction with a Lewis acid promotes C-C coupling of Bodipy monomers leading to mixtures of various oligomers. When a single position is blocked with an iodo or phenyl group, formation of the dimer is favored. These dimers display two successive oxidation and two reduction waves separated on average by 260 and 130 mV, respectively, corresponding to each Bodipy subunit.

A tailored hybrid BODIPY-oligothiophene donor for molecular bulk heterojunction solar cells with improved performances.

Fixation of a 5-hexyl-2,2'-bithienyl unit on a conjugated BODIPY donor increases the conversion efficiency of the resulting molecular bulk heterojunction solar cells from 1.30 to 2.20%.