Quasi‐One‐Dimensional Electronic Systems Formed from Boron Dipyrromethene (BODIPY) Dyes

Abstract

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.

Charge‐Recombination Fluorescence from Push–Pull Electronic Systems Constructed around Amino‐Substituted Styryl–BODIPY Dyes

“…39 The emission peak lies at 640 nm (i.e., 15 635 cm −1 ) and the profile can be deconstructed into Gaussian‐shaped bands with a common half‐width of 680 cm −1 and accompanying vibronic components of 1300 and 580 cm −1 . The Huang–Rhys factors ( S ), which are 0.96 ( ν =750 cm −1 ) and 0.79 ( ν =1600 cm −1 ) at room temperature, have values of 0.30 ( ν =735 cm −1 ) and 0.11 ( ν =1570 cm −1 ) in the glassy matrix and are in better accord with those expected40 for a π–π* transition. The implication, therefore, is that the glassy matrix restricts internal charge transfer by virtue of its rigid nature; it might be noted that the polarity of glassy MTHF has been likened to that of N , N ‐dimethylformamide at room temperature 41.…”

A Versatile Synthesis of Long-Wavelength-Excitable BODIPY Dyes from Readily Modifiable Cyclopenta[2,1-b:3,4-b′]dithiophenes

“…Nevertheless, irradiation of 17 at 320 nm generates no pyrene emission due to cascade energy transfer to the tetramethyl Bodipy unit (picoseconds time scale). 27 This result is in keeping with the observation made for compound 14 (Figure 1b). The excitonic energy of the tetramethyl Bodipy is transferred to the final energy acceptor (the bis-styryl dye) which relaxes to the ground state by emitting light at 864 nm as in the previous case.…”

Tuning Optical Properties of BODIPY Dyes by Pyrrole Conjugation for Photoacoustic Imaging

“…[ 19 ] In addition, we wanted to tune the absorption maximum (λ Max ) of BODIPYs, which is typically for aryl conjugated BODIPYs < 700 nm range, into the near‐infrared (NIR). The electron‐rich thiophene, or polyaromatics like anthracene and pyrene‐conjugated BODIPY [ 30 ] also exhibited λ Max < 700 nm (see Figure A). The 8‐aza substituted tetraaryl azaBODIPYs also exhibit λ Max < 700 nm, which have been explored in PA imaging [ 31 ] and for analyte‐induced change by ratiometric detection.…”