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Two pyrene dimers containing an -O-Si-Si-O- or -O-Si-O- linkage have been designed which exhibit ratiometric excimer/monomer emission upon fluoride anion induced Si-O bond cleavage. Incorporation of the probe into water soluble polymeric nanoparticles enhances its intracellular uptake and displays ratiometric fluorescent sensing for F(-) in living cells.

It is essential to create organic compounds that exhibit circularly polarized luminescence (CPL) in the near‐infrared (NIR) range. Helicene‐type emitters possess appealing chiroptical features, however, such NIR molecules are scarce due to a paucity of synthetic strategies. Herein, we developed a series of helical β‐isoindigo‐based B−O−B bridged aza‐BODIPY analogs that were synthesized conveniently. The reaction of diimino‐β‐isoindigo with a heteroaromatic amine produced a restricted ligand cavity, which triggered off the generation of a B−O−B bridge. The B−O−B bridge led to distorted conformations that satisfy the helical requirements, resulting in excellent spectroscopic and chiroptical properties. Tunable CPL with the highest luminescence dissymmetry factor (glum) of 1.3×10−3 and a CPL brightness (BCPL=11.5 M−1 cm−1) in the NIR region was achieved. This synthetic approach is expected to offer a new opportunity to chiral chemistry and increase flexibility for chiroptical tuning. [ABSTRACT FROM AUTHOR]

Fluorescent probes are intriguing material for ion detection. In this study, 4,4-difluoro-4-bora3a,4a-diaza-s-indacene (BODIPY) containing a dipicolylethylenediamine unit was developed as a colorimetric and fluorescence "turn-off" probe for Cu2+. The probe exhibited higher selectivity for Cu2+ than other common metal ions with a detection limit of 8.49 μM. With increasing Cu2+ concentration, the probe showed a red-shift in the absorption spectrum as well as fluorescence quenching, possibly due to the intramolecular charge transfer effect of the probe–Cu(II) complex. Furthermore, the probe was used for imaging Cu2+ in living cells based on confocal fluorescence imaging. The results show that the probe is an effective tool for detection copper ions. [ABSTRACT FROM AUTHOR]

A small series of fluorescent lysosome-targeting probes based on the BODIPY fluorophore and containing morpholine and nitro groups were rationally designed. These probes emitted light from green to NIR wavelengths, and provided specificity for imaging the lysosomes of hypoxic cells. The electron-withdrawing nitrophenyl group at the meso position was found to lead to highly efficient nonradiative decay of the S1 state, and hence a recovery of fluorescence when reduction of the nitro group occurred under hypoxic conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The review focuses on the characteristics of the emerging class of BODIPY-based hypoxia probes. • Design principles and recognition mechanisms of BODIPY-based hypoxia probes are summarized. • The relationship between structure and properties of BODIPY-based hypoxia probes are summarized. • Biological applications of BODIPY-based hypoxia probes in vitro and in vivo are overviewed. • Current challenges and further prospects for designing hypoxic probes are discussed. Hypoxic environment is an important feature of solid tumors, which comes from the imbalance of oxygen supply and consumption. Over the past few years, substantial progress has focused on the design of hypoxia probes derived from BODIPY scaffolds. Such probes are of particular interest and are closely related to tumor resistance to various therapies. This review highlights the construction strategies, recognition mechanisms as well as biological imaging applications of various BODIPY-based hypoxia probes. The aim is to inspire novel approaches and innovations for designing fluorescent probes to image hypoxic environments, and promote the development of diagnostics for tumors and hypoxia-responsive anticancer nanomedicines. [ABSTRACT FROM AUTHOR]

Novel five-membered-ring and six-membered-ring bis-(diphenylboron) complexes, consisting of hydrazine-Schiff base linked bispyrrole and two phenyl rings on the boron atoms, are readily synthesized via a facile two-step reaction. Weak intermolecular interactions are observed in the solid-state X-ray crystal structures due to the replacement of fluorine with a phenyl group at the boron atom. Both complexes exhibit high fluorescence in dilute solutions with quantum efficiencies in the range of 0.52–0.88. Because of weak intermolecular interactions and a large Stokes shift, the six-membered-ring complex 1 exhibits efficient solid-state fluorescence. However, the five-membered-ring complex 2 has a small Stokes shift, resulting in weak fluorescence in the solid-state through self-quenching. The structure–property relationships have been analyzed on the basis of X-ray crystallography, optical spectroscopy, and theoretical calculations. [ABSTRACT FROM AUTHOR]

Recent developments in organosilicon-based chemosensors for F − recognition are reviewed. The design strategies for improving the photophysical properties of organosilicon-based chemosensors are elaborated, with an emphasis placed on their utility for biological applications. The photophysical properties and electronic structures are analyzed in depth with reference made to the results of molecular modeling calculation and possible future research directions are assessed. [ABSTRACT FROM AUTHOR]

A 2,6-distyryl-substituted boradiazaindacene (BODIPY) dye and a new series of 2,6- p-dimethylaminostyrene isomers containing both α- and β-position styryl substituents were synthesized by reacting styrene and p-dimethylaminostyrene with an electron-rich diiodo-BODIPY. The dyes were characterized by X-ray crystallography and NMR spectroscopy and their photophysical properties were investigated and analyzed by carrying out a series of theoretical calculations. The absorption spectra contain markedly redshifted absorbance bands due to conjugation between the styryl moieties and the main BODIPY fluorophore. Very low fluorescence quantum yields and significant Stokes shifts are observed for 2,6-distyryl-substituted BODIPYs, relative to analogous 3,5-distyryl- and 1,7-distyryl-substituted BODIPYs. Although the fluorescence of the compound with β-position styryl substituents on both pyrrole moieties and one with both β- and α-position substituents was completely quenched, the compound with only α-position substituents exhibits weak emission in polar solvents, but moderately intense emission with a quantum yield of 0.49 in hexane. Protonation studies have demonstrated that these 2,6- p-dimethylaminostyrene isomers can be used as sensors for changes in pH. Theoretical calculations provide strong evidence that styryl rotation and the formation of non-emissive charge-separated S1 states play a pivotal role in shaping the fluorescence properties of these dyes. Molecular orbital theory is used as a conceptual framework to describe the electronic structures of the BODIPY core and an analysis of the angular nodal patterns provides a reasonable explanation for why the introduction of substituents at different positions on the BODIPY core has markedly differing effects. [ABSTRACT FROM AUTHOR]

Abstract: A boron-dipyrromethene (BODIPY) derivative with a hydroxymethyl group at the meso-position, 1, was synthesized, which exhibits a highly specific and rapid ‘turn-off’ response for HOCl during confocal fluorescence microscopy experiments under physiological conditions and in live cells. The formation of an electron-withdrawing formyl substituent upon oxidation results in highly efficient nonradiative decay of the S1 state and hence in a drastic decrease in fluorescence emission intensity. [Copyright &y& Elsevier]

Boron dipyrromethenes (BODIPYs) with bulky triphenylsilylphenyl(ethynyl) and triphenylsilylphenyl substituents on pyrrole sites were prepared via Hagihara-Sonogashira and Suzuki-Miyaura cross-coupling with ethynyl-terminated tetraphenylsilane and boronic acid-terminated tetraphenylsilane. The chromophores are designed to prevent intermolecular π-π stacking interaction and enhance fluorescence in the solid state. Single crystals of 1 a and 2 b for X-ray structural analysis were obtained, and weak π-π stacking interactions of the neighboring BODIPY molecules were observed. Spectroscopic properties of all of the dyes in various solvents and in films were investigated. Triphenylsilylphenyl-substituted BODIPYs generally show more pronounced increases in solid-state emission than triphenylsilylphenyl(ethynyl)-substituted BODIPYs. Although the simple BODIPYs do not exhibit any fluorescence in the solid state ( Φ=0), arylsilyl-substituted BODIPYs exhibit weak to moderate solid-state fluorescence with quantum yields of 0.03, 0.07, 0.10, and 0.25. The structure-property relationships were analyzed on the basis of X-ray crystallography, optical spectroscopy, cyclic voltammetry, and theoretical calculations. [ABSTRACT FROM AUTHOR]