3,5-Diaryl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) Dyes:  Synthesis, Spectroscopic, Electrochemical, and Structural Properties

Abstract

This research was undertaken to obtain new "BODIPY" dyes that fluoresce at relatively long wavelengths. The title compounds 1a-e were prepared via a divergent route involving Suzuki couplings of arylboronic acids to N-tert-butoxycarbonyl-4-bromopyrrole 2, condensation of the products with an acid chloride, and incorporation of the boron difluoride entity. Two alkyl-substituted systems 7a and 7b were also prepared for comparison; the critical difference between structures 1 and 7 is that the former have an aryl group attached to each pyrrole nucleus whereas the latter only have alkyl substituents on that same ring. UV absorption and fluorescence emission data were compared for compounds 1 and 7. Absorption and fluorescence emission maxima for compounds 1 occur at higher wavelengths than for compounds 7, and the Stokes shifts for the aryl-substituted compounds 1 are larger than for the alkyl-substituted compounds 7. Fluorescence quantum yields measured for compounds 1 are less than for compounds 7, and possible reasons for this are outlined. Other physical data for the compounds were also collected. Oxidation and reduction potentials of the systems were obtained from cyclic voltammetry experiments, and a single-crystal X-ray structure determination was performed for the bisnaphthyl-substituted compound 1b.

New Trends in Near-Infrared Fluorophores for Bioimaging

“…2·2·2 "Coupled" BODIPY (36 -79, Fig. 4) Introduction of aryl, 40,41 vinylaryl (styryl), [42][43][44][45] or ethynylaryl 46-48 groups at the 1-to 7-positions significantly contributes to bathochromic shifts. The degree of the bathochromic shift depends on the introduction positions: a modification at the 3-/5-position has a more drastic effect than at the 1-/7-or 2-/6-position.…”

“…The degree of the bathochromic shift depends on the introduction positions: a modification at the 3-/5-position has a more drastic effect than at the 1-/7-or 2-/6-position. 40,45,49 Some of the 3-/5-substituted BODIPYs are commercially available. 21 These aryl moieties can be easily introduced via palladium-catalyzed coupling reactions (for all) 46 or Knoevenagel condensation (for vinylaryl BODIPY), 42,44 allowing easy tuning of the fluorescence wavelength.…”

“…21 These aryl moieties can be easily introduced via palladium-catalyzed coupling reactions (for all) 46 or Knoevenagel condensation (for vinylaryl BODIPY), 42,44 allowing easy tuning of the fluorescence wavelength. However, the extinction coefficients and the quantum yields of 3,5-aryl-substituted BODIPYs tend to decrease in some cases, 40 probably due to rotation of the aryl rings. 80 -111, Fig.…”

Phenylethynyl-BODIPY Oligomers: Bright Dyes and Fluorescent Building Blocks

“…Thus, our synthetic work starts with the preparation of 3,5-didecyloxybenzaldehyde in analogy to the literature. 6 Then, the BODIPY dye 2 was obtained following a rather routine procedure for the synthesis of this class of dyes. 1,4-Diethynylbenzene 3 and the mono-TMS-protected form of it (4) are important intermediates.…”

“…1,4-Diethynylbenzene 3 and the mono-TMS-protected form of it (4) are important intermediates. The BODIPY dye 2 can be iodinated at the electron-rich positions 2 and 6 using an I 2 /HIO 3 iodination procedure, 7 and both monoiodinated (5) and diiodinated (6) products can be obtained in satisfactory yields by adjusting the dye to iodination reagent ratio (or the reaction time). 2-Iodo-BODIPY dye 5 was then subjected to Sonogashira coupling conditions (Pd(Ph 3 )Cl 2 and CuI catalysis) and coupled to mono-TMS-protected 1,4-diethynylbenzene (4).…”