A near-infrared benzoquinone-coupled BODIPY: Synthesis, spectroscopic and electrochemical properties

Abstract

A near-infrared absorbing boron-dipyrromethene (BODIPY) chromophore coupled with two benzoquinone moieties at its 3,5-positions, 3, was prepared via Knoevenagel condensation of 1,3,5,7-tetramethyl-8-(4[Formula: see text]-benzonitrile) BODIPY 1 with 3,5-di-tert-butyl-4-hydroxybenzaldehyde to afford 1,7-dimethyl-3,5-di-(4[Formula: see text]-hydroxy-3[Formula: see text],5[Formula: see text]-di-tert-butyl styryl)-8-(4[Formula: see text]-benzonitrile) BODIPY 2, followed by oxidization with Ag2O in good yield (91%). The UV-vis-NIR absorption spectrum of 3 exhibits two major bands at 795 and 895 nm in the near-IR region, while 2shows maximum absorbance at 661 nm and strong fluorescence at 692 nm ([Formula: see text] 0.59). The cyclic voltammetry of 3 consists of two pairs of reversible one-electron reductions at -0.61 V and -0.88 V and two pairs of one-electron oxidation waves at 0.26 V and 0.54 V. Compared with the redox potentials of 2([Formula: see text] V and [Formula: see text] 0.25 V), the first reduction of 3 is anodically shifted for 710 mV, whereas the first oxidation potential is close. Theoretical calculation reveals that conjugation with the benzoquinone moieties on the BODIPY chromophore significantly lowers the LUMO energy level and the HOMO–LUMO energy gap, resulting in a dramatic bathochromic shift of the S0–S1 transition of 3 compared with that of 2. X-ray crystallographic analysis of 3 reveals that the whole molecule adopts a V-type twisted conformation along the delocalized [Formula: see text]-conjugated pathway.

Near-Infrared Photoacoustic Probe for Reversible Imaging of the ClO–/GSH Redox Cycle In Vivo

“…Synthesis of 1,3,5,7-Tetramethyl-8-fluorophenyl-4,4difluoro-4-bora-3a,4a-diaza-s-indacene (F-BDP). The one-pot method previously reported 32,33 was used to synthesize 1,3,5,7-tetramethyl-8-fluorophenyl-4,4-difluoro-4bora-3a,4a-diaza-s-indacene (F-BDP). 2,4-Dimethylpyrrole (1.55 mL, 15 mmol) and 4-fluorobenzaldehyde (0.51 mL, 5 mmol) were added to a 250 mL single-neck flask containing dry dichloromethane (25 mL).…”

“…The crude product was purified by silica gel flash column chromatography (silica gel, CH 2 Cl 2 /petroleum = 1/1) and the recrystallization (CHCl 3 /hexane) yielded purple crystals of DiOH-BDP (200 mg, 52% yield). 1 (33,000), 375 (75,100), 599 (48,100), 648 (140,000).…”