Lewis Acid Modulation of meso‐Pyridyl BODIPY Chromophores

Abstract

Two pyridyl‐substituted boron dipyrromethene (BODIPY) compounds are shown to interact with the strong Lewis acid B(C6F5)3. The borane adducts are characterized by multinuclear NMR and in one case by X‐ray crystallography. The titration of pyridyl‐substituted BODIPYs with B(C6F5)3 results in a bathochromic shift of the UV/Vis absorption and emission spectra, with the magnitude of the shift depending on the distance of the bound borane from the BODIPY core. In meso‐4‐pyridyl‐BODIPY, binding of B(C6F5)3 induces a small circa 230 cm−1 red shift in the UV/Vis absorption maximum, with a much larger 1950 cm−1 shift in the photoluminescence maximum. In meso‐4‐pyridylphenyl‐BODIPY, where the pyridine Lewis base is separated from the BODIPY core by a phenyl spacer, smaller shifts of circa 120 cm−1 in UV/Vis absorption and 330 cm−1 in photoluminescence are observed. This work shows that these organic chromophores can interact with Lewis acids as a means of systematically perturbing the electronic structure and excited‐state properties.

Cyclometalated iridium–BODIPY ratiometric O2 sensors

“…However in complex 6a , where the [Ir(F 2 ppy) 2 (CNAr dmp )] + fragment is linked to the BODIPY via a short pyridyl spacer, the BODIPY fluorescence is significantly red-shifted to 549 nm, and while not as pronounced the fluorescence in the piq complex with the same linker ( 6b ) red-shifts to 528 nm. This measurable red shift of the fluorescence upon coordination to iridium is similar to the effect we observed previously when Lewis acidic boranes were coordinated to BODIPY 3 65. Lifetimes for the fluorescence component are quite similar to the free BODIPYs 3–5 (Table S2†).…”

“…Pyridyl-substituted BODIPY precursors 3–5 with three types of linkers at the meso -position were prepared. Compounds 3 and 4 , with a meso -pyridyl and extended meso -4-pyridylphenyl linker, respectively, were accessed following known procedures,63,64 and the Lewis acid–base chemistry of these versions have been recently described by our group 65. Methylene-spaced 4-pyridinyl–CH 2 –BODIPY 5 , with an unconjugated linker between the pyridine moiety and the BODIPY core, can be prepared by the previously reported synthetic method involving a palladium-catalyzed Suzuki cross-coupling reaction 66.…”

Control of Multicolor and White Emission by Adjusting the Equilibrium between Fluorophores, Lewis Acids, and Their Complexes in Polymers

“…[9] There are several methods to achieve multicolor emissive materials with as ingle luminophore: [10] 1) control the equilibrium of protolytic reactions of an emissive dye; [11] 2) control the equilibrium between al uminophore,acyclic compound, and its complex; [12] and 3) control the equilibrium between afluorescent dye,aLewis acid, and its complex. [13] There have been several reports on multicolor emissive compounds with asingle luminophore that exhibit emission in the solid state. [14] Some examples include 1) single-luminophore liquid crystals that exhibit bright tricolored mechano-chromic luminescence; [15] 2) p-conjugated systems that consist of aflexible and nonplanar p joint and two emissive rigid and planar wings; [16] and 3) combinations of p-conjugated molecules and Lewis acids.…”

Tris(pentafluorophenyl)borane‐pyrrolo[3,2‐b]pyrrole Hybrids: Solid‐State Structure and Crystallization‐Induced Enhanced Emission

“…For example, tris(pentafluorophenyl)borane (TPFB) is recognized as a powerful Lewis acid because of the electron‐withdrawing effects of the three perfluorinated aryl rings . The high stability and the unique properties of TPFB have been useful in a wide variety of reactions and for various applications including frustrated Lewis pair chemistry, and materials chemistry . Bazan, Nguyen, and co‐workers reported luminescent color tuning of conjugated polymers containing pyridine moieties by complexation with TPFB through boron‐nitrogen (B−N) complex .…”

“…[5][6][7] The high stability and the unique properties of TPFB have been useful in a wide variety of reactions and for various applications including frustrated Lewis pair chemistry, and materials chemistry. [8][9][10][11][12][13][14][15][16][17][18][19] Bazan, Nguyen, and co-workers reported luminescent color tuning of conjugated polymers containing pyridine moieties by complexation with TPFB through boron-nitrogen (BÀ N) complex. [11] Hashim, Romero-Nieto, and co-workers achieved luminescent color tuning of a boron-carbonyl (BÀ O) complex, composed of benzaldehyde derivatives as the Lewis base and TPFB as the Lewis acid.…”