A versatile, modular synthesis of monofunctionalized BODIPY dyes

Abstract

A careful choice of the pyrrole building blocks allows the synthesis of a wide range of monohalogenated BODIPY dyes with excellent reactivity in palladium catalyzed coupling reactions.

Effect of the substitution position (2, 3 or 8) on the spectroscopic and photophysical properties of BODIPY dyes with a phenyl, styryl or phenylethynyl group

“…However, in contrast to what was observed for 8-Ph, but in accordance to what was found for 3-Ph, fwhmem, fwhmabs and  of 2-Ph increase roughly parallel with the dielectric constant  of the solvent. 3-Ph exhibits large  values, from 0.81 to 1.00, which are in good agreement with previously reported ones, 35,37 except for 3-Ph in toluene that shows a slightly larger  in this work. Regarding the rate constants of radiative (kf) and nonradiative (knr) S1 deactivation, 3-Ph shows an increase of kf with solvent refractive index n, from 1.6 × 10 8 s -1 in methanol to 2.2 × 10 8 s -1 in toluene, whereas knr ranges from negligible values in diethyl ether and 1,4-dioxane to 0.4 × 10 8 s -1 in methanol.…”

“…3-Ethyn exhibits large  values, from 0.77 (in cyclohexanone) to 1.00 in several solvents, which is in good agreement with previous reports. 35,37 Likewise, the fluorescence lifetime  decreases from 5.17 ns in methanol to 4.35 ns in chlorobenzene ( Figure S8). These  and  values involve an increase in kf in more polarizable solvents, ranging from (1.6-1.7) × 10 8 s -1 in acetonitrile and methanol to (2.2-2.3) × 10 8 s -1 in chlorobenzene and toluene, combined with low values for knr.…”

“…3-Styryl displays a main, narrow S1S0 transition band (Figure 2A) similar to other 3-substituted boron dipyrromethenes. 35,37 The abs(max) values range from 549 to 561 nm, with a typical red shift from acetonitrile to chlorobenzene. The extended conjugation provided by the styryl functional group causes an extra bathochromic shift of around 20 nm with respect to 3-Ethyn, and ca.…”

“…The synthesis of 2-Ph, 3-Ph, 2-Ethyn and 3-Ethyn was carried out by following our previously reported procedure, 37 whereas the synthesis of 8-Ph was performed as described by Kee et al 32 Also 8-Ethyn 26 and 3-Styryl 35 were synthesized prepared according to our protocols. Novel synthetic procedures for BODIPY derivatives 2-Styryl and 8-Styryl are described next.…”

“…2-Styryl [4,4-difluoro-5,7,8-trimethyl-2-(E)-styryl-4-bora-3a,4a-diaza-s-indacene] was prepared as follows (Scheme 1): To a stirred solution of BODIPY 1 (117 mg, 0.33 mmol, prepared as in reference 37 ) in toluene (5 mL) at room temperature, (E)-styrylboronic acid (64 mg, 0.43 mmol) and tetrakis(triphenylphosphine) palladium (4 mg, 3.4 μmol) were added, followed by the addition of 1.5 mL of Na2CO3 1M (aq). The solution was heated to reflux and after 3 h the reaction mixture was poured in Et2O (300 mL) and dried over magnesium sulfate.…”