Dihydronaphthalene‐Fused Boron–Dipyrromethene (BODIPY) Dyes: Insight into the Electronic and Conformational Tuning Modes of BODIPY Fluorophores

Abstract

A new series of boron-dipyrromethene (BDP, BODIPY) dyes with dihydronaphthalene units fused to the beta-pyrrole positions (1a-d, 2) has been synthesised and spectroscopically investigated. All the dyes, except pH-responsive 1d in polar solvents, display intense emission between 550-700 nm. Compounds 1a and 1b with a hydrogen atom and a methyl group in the meso position of the BODIPY core show spectroscopic properties that are similar to those of rhodamine 101, thus rendering them potent alternatives to the positively charged rhodamine dyes as stains and labels for less polar environments or for the dyeing of latex beads. Compound 1d, which carries an electron-donating 4-(dimethylamino)phenyl group in the meso position, shows dual fluorescence in solvents more polar than dibutyl ether and can act as a pH-responsive "light-up" probe for acidic pH. Correlation of the pK(a) data of 1d and several other meso-(4-dimethylanilino)-substituted BODIPY derivatives allowed us to draw conclusions on the influence of steric crowding at the meso position on the acidity of the aniline nitrogen atom. Preparation and investigation of 2, which carries a nitrogen instead of a carbon as the meso-bridgehead atom, suggests that the rules of colour tuning of BODIPYs as established so far have to be reassessed; for all the reported couples of meso-C- and meso-N-substituted BODIPYs, the exchange leads to pronounced redshifts of the spectra and reduced fluorescence quantum yields. For 2, when compared with 1a, the opposite is found: negligible spectral shifts and enhanced fluorescence. Additional X-ray crystallographic analysis of 1a and quantum chemical modelling of the title and related compounds employing density functional theory granted further insight into the features of such sterically crowded chromophores.

Host lipid droplets: An important source of lipids salvaged by the intracellular parasite Toxoplasma gondii

“…We performed assays to examine whether Toxoplasma is able to take up neutral lipids from host LD. In lipid trafficking studies, BODIPY-fatty acids are routinely used and have been shown to incorporate into LD and be readily metabolized by living cells to phospholipids, DAG, TAG and CE [49–52]. We incubated infected cells with C4-BODIPY-C9, which has the fluorophore BODIPY 500/510 linked within the fatty acid chain, to track the internalization of this fatty acid analog into the parasite.…”

Azadipyrromethenes: from traditional dye chemistry to leading edge applications

“…In this first report nine different tetraarylazadipyrromethenes were described using these routes. 15 N labelled derivatives of 4a and 6a showed that in the overall conversion of 1a into 3a, two related pathways are ongoing concurrently; the first involves a dimerization of in situ formed 3,5-diphenyl-2H-pyrrol-2-imine 7, and the other reaction of 7 with 2,4-diphenylpyrrole 4a (Scheme 3). condensation between the corresponding aromatic aldehyde and substituted acetophenone.…”

Synthesis, spectral-luminescent properties of B(III) and Zn(II) complexes with alkyl- and aryl-substituted dipyrrins and azadipyrrins

“…Later, a direct modification was made to provide ster ical hindrances for rotation of meso phenyl substitu ents that led to emergence of strong fluorescence of the corresponding dipyrrin complexes containing mesityl groups instead of phenyl rings [20][21][22]. It was shown subsequently in the works [23,24] that, in con trast to meso aryl substitution, the introduction of mobile aromatic groups at the periphery of pyrrole rings of the ligand may result in opposite effect, enhancement of complex fluorescence. Number and positions of aryl substituents in pyrrole rings may play an important role.…”