Chlorinated BODIPYs: Surprisingly Efficient and Highly Photostable Laser Dyes

Abstract

A series of mono‐ to hexachlorinated BODIPY dyes have been prepared in good to excellent yields through the use of N‐chlorosuccinimide as an inexpensive halogenating reagent. This library of chlorinated dyes allowed analysis in detail, from the experimental and theoretical points of view, of the dependency of the photophysical and optical properties of the dyes on the number and positions of the chlorine substituents on their BODIPY cores. Quantum mechanical calculations predict the regioselectivity of the halogenation reaction and explain why some positions are less prone to chlorination. The new chlorinated BODIPYs exhibit enhanced laser action with respect to their non‐halogenated analogues, both in liquid solution and in the solid phase. In addition, chlorination is a facile and essentially costless protocol for overcoming important shortcomings exhibited by commercially available BODIPYs, which should favor their practical applications in optical and sensing fields.

Quantitative Profiling of the Heavy‐Atom Effect in BODIPY Dyes: Correlating Initial Rates, Atomic Numbers, and 1O2 Quantum Yields

“…Caution: Some intermediates and products are volatile! 1 H, 13 C, and 19 F NMR spectra were recorded with Bruker AV 300 MHz, Bruker AV 400 MHz, and Agilent DD2 600 spectrometers. Chemical shifts (δ) are reported in ppm and were referenced to the residual solvent peak.…”

“…R f = 0.69 (CH 2 C 1 and C 7 ), 133.9 (C 8 ), 131.9 (2 C, C 9 and C 10 ), 113.1 (2 C, C 2 and C 6 ), 58.1 (CH 2 ), 20.7 (CH 3 CO 2 R), 15.0 (2 C, C 1 CH 3 and C 7 CH 3 ), 14.1 (t, 4 J C,F = 2.6 Hz, 2 C, C 3 CH 3 and C 5 CH 3 ) ppm. 19 8- (Acetoxymethyl)-2,6-diiodo-1,3,5,7-tetramethylpyrromethene Fluoroborate (4): To an orange suspension of 1 (157 mg, 491 μmol) in EtOH (50 mL) under air were added iodine (249 mg, 981 μmol) and HIO 3 (173 mg, 981 μmol) to give a dark red suspension, which was stirred for 24 h. Water (50 mL) was added, and the mixture was extracted with CH 2 Cl 2 (2 × 50 mL). The combined organic layers were washed with an Na 2 S 2 O 3 ·5H 2 O solution (aq., 10 % w/w, 100 mL), and the aqueous layer was back-extracted with CH 2 Cl 2 (50 mL).…”

“…Purification by column chromatography (CH 2 13 C NMR (100 MHz, CDCl 3 ): δ = 170.5 (CH 3 CO 2 R), 158.1 (2 C, C 3 and C 5 ), 143.6 (2 C, C 1 and C 7 ), 132.9 (C 8 ), 132.7 (2 C, C 9 and C 10 ), 87.4 (2 C, C 2 and C 6 ), 58.4 (CH 2 ), 20.7 (CH 3 CO 2 R), 18.3 (2 C, C 1 CH 3 and C 7 CH 3 ), 16.5 (t, 4 J C,F = 2.6 Hz, 2 C, C 3 CH 3 and C 5 CH 3 ) ppm. 19 90 mL, 18.5 mmol) in dry CH 2 Cl 2 (100 mL) was cooled to 0°C, and then acetyl chloride (789 μL, 11.1 mmol) was added dropwise to give a yellow solution, which was warmed to room temperatur and stirred for 26 h. To the resulting dark red solution was added DIPEA (6.42 mL, 36.9 mmol), and the solution was stirred for 15 min before the addition of BF 3 ·OEt 2 (4.56 mL, 36.9 mmol). The dark red solution was stirred for 30 min, a saturated NaHCO 3 solution (aq., 200 mL) was added, and the mixture was extracted with CH 2 Cl 2 (3 × 200 mL).…”

“…The combined organic layers were dried with Na 2 SO 4 and concentrated in vacuo to give a dark red solid, which was purified by column chromatography (CH 2 C 1 and C 7 ), 131.4 (2 C, C 9 and C 10 ), 111.8 (2 C, C 2 and C 6 ), 17.5 (C 8 CH 3 ), 16.6 (2 C, C 1 CH 3 and C 7 CH 3 ), 13.8 (t, 4 J C,F = 2.6 Hz, 2 C, C 3 CH 3 and C 5 CH 3 ) ppm. 19 To a bright orange suspension of 5 in EtOH (50 mL) under air were added iodine (254 mg, 1.00 mmol) and HIO 3 (176 mg, 1.00 mmol) to give a dark orange suspension, which was stirred for 16 h. A solution of Na 2 S 2 O 3 ·5H 2 O (aq., 10 % w/w, 100 mL) was added, and the mixture was extracted with CH 2 Cl 2 (2 × 100 mL). The combined organic layers were dried with Na 2 SO 4 and concentrated in vacuo.…”

Photophysics of BODIPY Dyes as Readily-Designable Photosensitisers in Light-Driven Proton Reduction

“…All solutions and liquids in multicomponent catalyst systems were degassed via ultrasound treatment for at least 30 min before use. BODIPY dyes 1 [37], 2 [38], 3 [26], 4 [39], 5, 7, 8 [40], and 6 [41] were prepared using published procedures.…”