Erhong Hao

Regioselective stepwise bromination of boron dipyrromethene (BODIPY) dyes.

Halogenated BODIPYs are important synthetic precursors and potential sensitizers for photodynamic therapy (PDT). Electrophilic bromination of pyrrolic-unsubstituted BODIPYs using bromine regioselectively generated mono- to heptabromoBODIPYs in a stepwise fashion in good to excellent yields. These resultant bromoBODIPYs were applied for regioselective substitution and Suzuki coupling reaction to generate BODIPYs 4, 5, 6, and 7 in good to excellent yields. According to NMR and X-ray analysis results, the stepwise bromination first takes place at 2,6-, then at 3,5-, and eventually at 1,7-positions, whereas the regioselective substitution occurs first at 3,5- then at 1,7-positions of the chromophore. The spectroscopic properties of these resultant BODIPYs were studied, which shows the potential application of these bromoBODIPYs as sensitizers for PDT.

β-Formyl-BODIPYs from the Vilsmeier−Haack Reaction

A series of beta-formyl-BODIPYs 2 were synthesized in high yields from tetramethyl-BODIPYs 1 via the Vilsmeier-Haack reaction and were further functionalized using a Knoevenagel condensation to generate novel BODIPYs 3 and 4.

Synthesis and Functionalization of Asymmetrical Benzo-Fused BODIPY Dyes

A series of asymmetrical benzo-fused BODIPY dyes were synthesized from the Sonogashira coupling and nucleophilic substitution reactions on the 3-halogenated benzo-fused BODIPY, generated from readily available 3-halogeno-1-formylisoindoles in a two-step synthetic procedure. This novel BODIPY platform provides an easy path for the linking of BODIPY fluorophore to various desired functionalities as demonstrated in this work. Most of the resulting BODIPY dyes show long-wavelength absorption and fluorescence emission, with good fluorescence quantum yields and long fluorescence lifetimes.

A selective fluorescent sensor for imaging Cu2+ in living cells

Copper ion is a biochemically essential yet toxic metal ion, connected to serious neurodegenerative diseases, and also has been identified as an environmental pollutant. For the effective detection of Cu2+ in biological and environmental systems, we have developed a new membrane-permeable Cu2+-selective water-soluble BODIPY 1, which was synthesized by nucleophilic disubstitution of novel 3,5-diiodo-BODIPY 4 with N,N-bis(2-hydroxyethyl)amines. BODIPY 1 shows a highly sensitive and selective fluorescence response to Cu2+ in aqueous solution. Fluorescence image experiments establish that 1 can be used to monitor intracellular Cu2+ within living cells.

Long wavelength red fluorescent dyes from 3,5-diiodo-BODIPYs

Amphiphilic and long wavelength red fluorescent dyes (4 and 7) were prepared from the Sonogashira coupling reactions of 3,5-diiodo-BODIPYs (1 and 6). One of these compounds, BODIPY 7, readily accumulated within human carcinoma HEp2 cells and was found to localize mainly within the endoplasmic reticulum (ER).

Highly Fluorescent BF2 Complexes of Hydrazine–Schiff Base Linked Bispyrrole

A series of BF2 complexes of hydrazine-Schiff base linked bispyrrole have been prepared from a simple two-step reaction from commercially available substances and are highly fluorescent in solution, film, and solid states with larger Stokes shift and excellent photostabilities comparable or even super to those of their BODIPY analogues. These resultant fluorescent dyes are highly susceptible to the postfunctionalization, as demonstrated in this work via the Knoevenagel condensation to introducing functionalities or tether groups to the chromophore.

β-Thiophene-Fused BF2-Azadipyrromethenes as Near-Infrared Dyes

A facile synthetic route to a new class of near-IR β-thiophene-fused BF2-azadipyrromethenes (aza-BDTPs) is presented. Sharp absorption and fluorescence emission bands at around 800 nm were observed for these highly photostable aza-BDTPs, with a large absorption coefficient and very low absorptions in the visible range from 700 to 380 nm.

Expeditious synthesis of porphyrin–cobaltacarborane conjugates

Two porphyrin-cobaltacarborane conjugates and were prepared in high yields via a nucleophilic ring-opening reaction of . These novel boron-rich and fluorescent compounds have potential application as boron delivery agents for the boron neutron capture therapy of tumors.

Accessing near-infrared-absorbing BF2-azadipyrromethenes via a push-pull effect.

Novel aza-BODIPYs with significant bathochromic shifts were designed and synthesized by installation of strong electron-withdrawing groups on the para-positions of 1,7-phenyls and electron-donating groups on the para-positions of 3,4-phenyls. These dyes show strong NIR fluorescence emissions up to 756 nm, and absorptions up to 720 nm.

Diversity-Oriented Facile Access to Highly Fluorescent Membrane-Permeable Benz[c,d]indole N-Heteroarene BF2 Dyes

A diversity-oriented one-pot synthesis of a series of membrane-permeable BF2-rigidified benz[c,d]indole N-heteroarene BBN and BBC dyes has been achieved from the condensation of two commercial components (benz[c,d]indol-2-one and a set of N-heteroarene derivatives that can be selected from thousands of commercially available sources) and the subsequent in situ BF2 complexation reaction. These dyes enjoy a set of excellent photophysical properties including the large Stokes shift, high solution and solid-state fluorescence, and excellent photostabilities.