Boron Dipyrromethene Dyes Research Articles

Visible-Light Excitation of BODIPYs Enables Self-Promoted Radical Arylation at Their 3,5-Positions with Diazonium Salts.

A metal- and additive-free photochemical strategy for the direct arylation of boron dipyrromethene dyes (BODIPYs) at their 3,5-positions is reported. The operationally simple approach occurs under illumination by visible light in the absence of any external photoredox catalyst. The chemistry is driven by the singlet excited state (1PS*) of BODIPYs upon visible-light absorption while successively triggering the formation of aryl radicals from aryl diazonium salts. Furthermore, a new type of indole-fused BODIPY with NIR absorption has also been synthesized for the first time.

BODIPY Dyes Bearing Multibranched Fluorinated Chains: Synthesis, Structural, and Spectroscopic Studies.

A small series of boron-dipyrromethene (BODIPY) dyes, characterized by the presence of multibranched fluorinated residues, were designed and synthesized. The dyes differ in both the position (para-perfluoroalkoxy-substituted phenyl ring or boron functionalization) and number of magnetically equivalent fluorine atoms (27 or 54 fluorine atoms per molecule). Photophysical and crystallographic characterization of the synthesized BODIPYs was carried out to evaluate the effect of the presence of highly fluorinated moieties on the optical and morphological properties of such compounds.

A Malonyl-Based Scaffold for Conjugatable Multivalent Carbohydrate-BODIPY Presentations.

A concise synthetic route from methylmalonate to a tetravalent aliphatic scaffold has been developed. The ensuing tetra-tethered derivative is equipped with two hydroxyl groups, as well as orthogonal alkene and alkyne functionalities. The usefulness of the scaffold has been demonstrated with the preparation of two representative multivalent derivatives: (i) a tetravalent compound containing two D-mannose units, one fluorescent boron-dipyrromethene (BODIPY) dye and a suitably functionalized amino acid and (ii) by way of dimerization and saponification, a water-soluble tetramannan derivative containing two fluorescent BODIPY units. Additionally, photophysical measurements conducted on these derivatives support the viability of the herein designed single and double BODIPY-labeled carbohydrate-based clusters as fluorescent markers.

Novel pyrene-BODIPY dyes based on cyclotriphosphazene scaffolds: Synthesis, photophysical and spectroelectrochemical properties

Two novel cyclotriphosphazene compounds (Cpz-2, 3) bearing mono- and distyryl(pyrene) borondipyrromethene (BODIPY) dyes (Bod-4, 5) were synthesized and characterized by using elemental analysis, FT-IR, MALDI-TOF, 1H NMR, 13C NMR and 31P NMR techniques. The photophysical properties of these novel compounds were investigated by UV-Vis, fluorescence spectroscopy, and electrochemical properties were investigated by CV and SWV measurements. Subsequently, electrochromic properties of novel cyclotriphosphazene compounds (Cpz-2, 3) and their precursor dyes (Bod-4, 5) were investigated via in-situ spectroelectrochemical measurements. According to results, they gave electrochemically manufactured types having various colors in their diverse oxidation states in solution, suggesting that they may have a significant role in development of the color exchange matter in electrochromic device technologies.

Synthesis, characterization and application of meso-substituted fluorinated boron dipyrromethenes (BODIPYs) with different styryl groups in organic photovoltaic cells

A series of highly fluorinated BODIPY dyes with different styryl aromatic donor groups such as phenyl, naphthyl and anthracyl were designed, synthesized, characterized and applied as electron-donor materials in organic photovoltaic cells (OPV). The introduction of the styryl moieties leads to a large bathochromic shift and to a significant decrease in the HOMO-LUMO energy-gaps. All the BODIPY dyes showed relatively low HOMO energies ranging from −5.21 to −5.54 eV as determined from cyclic voltammetry measurements. Furthermore, they all show good solubility in organic solvents, thermal stability, excellent film-forming abilities which added with the great optoelectronics characteristics makes them excellent candidates as electron-donor materials for OPV cells. The power conversion efficiency (PCE) of the OPV based on the best BODIPY blend (BDP3/PC70BM (1:2, w/w) was 2.8% with a high open circuit voltage (VOC) of 1.00 V, which is a very promising PCE result for BODIPY based OPV and a top VOC value for this kind of systems.

Synthesis and photophysical characterization of highly water-soluble PEGylated BODIPY derivatives for cellular imaging

A series of poly(ethylene glycol) (PEG)-modified water-soluble boron dipyrromethene (BODIPY) dyes (EtBOD-PEG and BOD-PEG) were synthesized and their photophysical properties in various solutions were investigated. The presence of ethyl groups at the 2,6-positions of the BODIPY core in EtBOD-PEG resulted in bathochromic shifts in both the absorption and emission spectra relative to those of the unsubstituted BOD-PEG. Importantly, bulky di-branched PEG chains were introduced at the meso position of the BODIPY core, leading to enhanced solubilities and high fluorescence quantum yields in aqueous solutions. The water-soluble BODIPY dyes were explored for their applicability in fluorescent bio-imaging using MCF-7 human breast cancer cells. The dyes were cell-permeable and were concentrated in cellular cytoplasm area, suggesting that they have potential applications as bio-imaging agents.

Tetrahydrodibenzophenanthridine-Based Boron-Bridged Polycyclic Aromatic Hydrocarbons: Synthesis, Structural Diversity, and Optical Properties

A series of B←N coordinated tetrahydrodibenzo[a,i]phenanthridine-based polycyclic aromatic hydrocarbons (PAHs) have been designed and synthesized. All of these compounds have been characterized by multinuclear NMR spectroscopy and high-resolution mass spectrometry. Compounds 1, 2, 4, and 7 have also been characterized by single-crystal X-ray diffraction analysis. Our newly synthesized compounds exhibit good luminescence quantum yields in solution and moderate quantum yields in the solid state. Furthermore, the compounds show a large Stokes shift in comparison to the well-known boron–dipyrromethene dyes.

BODIPY derivatives bearing borneol moieties: Enhancing cell membrane permeability for living cell imaging

Three novel boron-dipyrromethene (BODIPY) dyes bearing borneol moieties have been designed, synthesized and characterized. The single-crystal structure of the compound 3 was also elucidated for the first time. Their photophysical properties and confocal fluorescence images were investigated by the optical spectroscopy and Confocal fluorescence microscopy. The results indicate that the ompounds 2–3 take on high fluorescence quantum yield and cell membrane permeability, which can be utilized as fluorescent visualizers for cell and lysosome fluorescence imaging.

A near-infrared I emissive dye: toward the application of saturable absorber and multiphoton fluorescence microscopy in the deep-tissue imaging window.

A boron-dipyrromethene (BODIPY) dye emitting in the near-infrared (NIR) I region (723 nm) exhibits strong saturable absorption at 680 nm. Its multiphoton absorption spectra in the NIR II and III regions are determined. Three-photon fluorescence imaging of the BODIPY-labeled cells excited at 1665 nm is also demonstrated.

A H₂O₂-Responsive Boron Dipyrromethene-Based Photosensitizer for Imaging-Guided Photodynamic Therapy.

In this study, we demonstrate a novel H2O2 activatable photosensitizer (compound 7) which contains a diiodo distyryl boron dipyrromethene (BODIPY) core and an arylboronate group that quenches the excited state of the BODIPY dye by photoinduced electron transfer (PET). The BODIPY-based photosensitizer is highly soluble and remains nonaggregated in dimethyl sulfoxide (DMSO) as shown by the intense and sharp Q-band absorption (707 nm). As expected, compound 7 exhibits negligible fluorescence emission and singlet oxygen generation efficiency. However, upon interaction with H2O2, both the fluorescence emission and singlet oxygen production of the photosensitizer can be restored in phosphate buffered saline (PBS) solution and PBS buffer solution containing 20% DMSO as a result of the cleavage of the arylboronate group. Due to the higher concentration of H2O2 in cancer cells, compound 7 even with low concentration is particularly sensitive to human cervical carcinoma (HeLa) cells (IC50 = 0.95 μM) but hardly damage human embryonic lung fibroblast (HELF) cells. The results above suggest that this novel BODIPY derivative is a promising candidate for fluorescence imaging-guided photodynamic cancer therapy.

Multifunctional Polystyrene Core/Silica Shell Microparticles with Antifouling Properties for Bead-Based Multiplexed and Quantitative Analysis.

Commercial bead-based assays are commonly built upon polystyrene particles. The polymeric carrier can be encoded with organic dyes and has ideal material properties for cytometric applications such as low density and high refractive index. However, functional groups are conventionally integrated during polymerization and subsequent modification is limited to the reactivity of those groups. Additionally, polystyrene as the core material leads to many hydrophobic areas still being present on the beads' surfaces even after functionalization, rendering the particles prone to nonspecific adsorption during an application. The latter calls for several washing steps and the use of additives in (bio)analytical assays. In this contribution, we show how these limitations can be overcome by using monodisperse polystyrene (PS) core/silica (SiO2) shell particles (SiO2@PS). Two different hydrophobic BODIPY (boron-dipyrromethene) dyes were encapsulated inside a poly(vinylpyrrolidone) (PVP) -stabilized polystyrene core in different concentrations to create 5-plex arrays in two separate detection channels of a cytometer. A subsequent modification of the silica shell with an equimolar APTES/PEGS (aminopropyltriethoxysilane/polyethylene glycol silane) blend added multifunctional properties to the hybrid core/shell microparticles in a single step: APTES provides amino groups for the attachment of a caffeine derivative (as a hapten) to create antigen-coupled microspheres; the PEG moiety effectively suppresses nonspecific binding of antibodies, endowing the surface with antifouling properties. The particles were applied in a competitive fluorescence immunoassay in suspension, and a highly selective wash-free assay for the detection of caffeine in beverages was developed as a proof of concept.

Mix-&-Read Determination of Mercury(II) at Trace Levels with Hybrid Mesoporous Silica Materials Incorporating Fluorescent Probes by a Simple Mix-&-Load Technique.

The synthesis, characterization, and application of mesoporous materials containing boron–dipyrromethene (BODIPY) moieties that allow the sensitive and selective detection of HgII in aqueous environments by fluorescence enhancement is reported. For this purpose, BODIPY dye I containing a thia‐aza crown ether receptor as the fluorescent probe for the detection of HgII in aqueous environments is encapsulated into mesoporous materials to avoid self‐quenching or aggregation in water. Determination of HgII is accomplished within a few seconds with high selectivity and sensitivity, reaching a limit of detection of 12 ppt. The determination of trace amounts of HgII in natural waters and in fish extracts is demonstrated by using our sensing material. The incorporation of the material into several μ‐PAD strips yields a portable, cheap, quick, and easy‐to‐handle tool for trace HgII analysis in water.

Symposium review: Intravital imaging of the lactating mammary gland in live mice reveals novel aspects of milk-lipid secretion

Milk fat comprises membrane-coated droplets of neutral lipid, which constitute the predominant source of lipids for survival of the suckling neonate. From the perspective of the dairy industry, they are the basis for the manufacture of butter and essential ingredients in the production of cheese, yogurt, and specialty dairy produce. To provide mechanistic insight into the assembly and secretion of lipid droplets during lactation, we developed novel intravital imaging techniques using transgenic mice, which express fluorescently tagged marker proteins. The number 4 mammary glands were surgically prepared under a deep plane of anesthesia and the exposed glands positioned as a skin flap with intact vascular supply on the stage of a laser-scanning confocal microscope. Lipid droplets were stained by prior exposure of the glands to hydrophobic fluorescent BODIPY (boron-dipyrromethene) dyes and their formation and secretion monitored by time-lapse subcellular microscopy over periods of 1 to 2 h. Droplets were transported to the cell apex by directed (superdiffusive) motion at relatively slow and intermittent rates (0–2 µm/min). Regardless of size, droplets grew by numerous fusion events during transport and as they were budding from the cell enveloped by apical membranes. Surprisingly, droplet secretion was not constitutive but required an injection of oxytocin to induce contraction of the myoepithelium with subsequent release of droplets into luminal spaces. These novel results are discussed in the context of the current paradigm for milk fat synthesis and secretion and as a template for future innovations in the dairy industry.

Highly Photostable and Fluorescent Microporous Solids Prepared via Solid-State Entrapment of Boron Dipyrromethene Dyes in a Nascent Metal-Organic Framework.

We report a strategy to synthesize highly emissive, photostable, microporous materials by solid-state entrapment of boron dipyrromethene (BODIPY) fluorophores in a metal-organic framework. Solvent-free mechanochemistry or accelerated aging enabled quantitative capture and dispersal of the PM605 dye within the ZIF-8 framework starting from inexpensive, commercial materials. While the design of emissive BODIPY solids is normally challenged by quenching in a densely packed environment, herein reported PM605@ZIF-8 materials show excellent emissive properties and to the best of our knowledge an unprecedented ∼10-fold enhancement of BODIPY photostability. Time-resolved and steady-state fluorescence studies of PM605@ZIF-8 show that interchromophore interactions are minimal at low dye loadings, but at higher ones lead to through-pore energy transfer between chromophores and to aggregate species.

Photo-Induced Charge Separation vs. Degradation of a BODIPY-Based Photosensitizer Assessed by TDDFT and RASPT2

A meso-mesityl-2,6-iodine substituted boron dipyrromethene (BODIPY) dye is investigated using a suite of computational methods addressing its functionality as photosensitizer, i.e., in the scope of light-driven hydrogen evolution in a two-component approach. Earlier reports on the performance of the present iodinated BODIPY dye proposed a significantly improved catalytic turn-over compared to its unsubstituted parent compound based on the population of long-lived charge-separated triplet states, accessible due to an enhanced spin-orbit coupling (SOC) introduced by the iodine atoms. The present quantum chemical study aims at elucidating the mechanisms of both the higher catalytic performance and the degradation pathways. Time-dependent density functional theory (TDDFT) and multi-state restricted active space perturbation theory through second-order (MS-RASPT2) simulations allowed identifying excited-state channels correlated to iodine dissociation. No evidence for an improved catalytic activity via enhanced SOCs among the low-lying states could be determined. However, the computational analysis reveals that the activation of the dye proceeds via pathways of the (prior chemically) singly-reduced species, featuring a pronounced stabilization of charge-separated species, while low barriers for carbon-iodine bond breaking determine the photostability of the BODIPY dye.

Bichromophoric Sensors for Ratiometric Measurements of Molecular Microenvironments through the Interplay of Charge Transfer and Energy Transfer Channels

A new molecular architecture was designed to amplify the sensitivity of bichromophoric probes, in which two sequential kinetic competitions of photophysical channels were used to define the emission yield of the lower energy chromophore. Additionally, the emission from both chromophores can be used for ratiometric measurements, which are concentration independent. Two sensors were synthesized to demonstrate the concept, coupling a boron-dipyrromethene (BODIPY) dye and a cyanine dye. Both the energy transfer from the BODIPY to the cyanine and the cyanine radiative channel compete with a charge transfer state formation, giving the cyanine emission intensity a twofold dependence on polarity. This was confirmed with steady state and time-resolved spectroscopies. Also, the large spectral gap between the two emissions (approx. 280 nm) makes the ratiometric measurements crosstalk-free. The use of the sensors in live cells was demonstrated through the staining and imaging of SK-LU-1 lung cells under normal and apoptotic conditions.

The investigation of in vitro dark cytotoxicity and photodynamic therapy effect of a 2,6-dibromo-3,5-distyryl BODIPY dye encapsulated in Pluronic® F-127 micelles

A 2,6-dibrominated 3,5-distyryl boron-dipyrromethene (BODIPY) dye with a moderately high singlet oxygen quantum yield was encapsulated in Pluronic® F-127 micelles, and its dark cytotoxicity and photodynamic activity were investigated on the human breast adenocarcinoma MCF-7 cell line. The BODIPY dye exhibited very low dark toxicity and a significant PDT effect when added in drug formulations consisting of 5.0% (v/v) DMSO in supplemented Dulbecco’s modified Eagle’s medium (DMEM) and as Pluronic® F-127 micelle encapsulation complexes in supplemented DMEM alone. An IC50 value of 4 ± 2 μM was obtained when the BODIPY dye was encapsulated in Pluronic® F-127 micelles during in vitro photodynamic activity studies in MCF-7 cancer cells with a 660 nm light emitting diode.

Synthesis of an ultrasensitive BODIPY-derived fluorescent probe for detecting HOCl in live cells.

Hypochlorous acid (HOCl) is a critical member of the reactive oxygen species (ROS) produced by immune cells to fight infections. On the other hand, HOCl in homeostasis causes oxidative damage to biomolecules and is linked to many diseases, including inflammatory, neurodegenerative, and cardiovascular diseases. Herein, we detail a procedure for the preparation of a boron-dipyrromethene (BODIPY)-derived fluorescent probe for HOCl (BClO) and its application as an imaging reagent in living cells. BClO is synthesized in one pot through a four-step procedure that is nearly the same as that for conventional BODIPY dye preparation, except for the ratio of starting materials. BClO has an extremely rapid response (saturated within seconds) and is ultrasensitive to HOCl. The detection limit of BClO reaches the subnanomolar range, which is the highest HOCl sensitivity to date. Taking advantage of the ultrasensitive character of BClO, we have previously demonstrated its ability to detect endogenous HOCl generated by macrophages and shown that it can also be used to discriminate cancer cell lines (which show high HOCl production) from non-cancer cell lines (which show low HOCl production). The protocol requires ~2 d for probe synthesis and up to ~18 h for fluorescence imaging and flow cytometry assays.

Mix-&-Read Determination of Mercury(II) at Trace Levels with Hybrid Mesoporous Silica Materials Incorporating Fluorescent Probes by a Simple Mix-&-Load Technique.

The synthesis, characterization, and application of mesoporous materials containing boron–dipyrromethene (BODIPY) moieties that allow the sensitive and selective detection of HgII in aqueous environments by fluorescence enhancement is reported. For this purpose, BODIPY dye I containing a thia‐aza crown ether receptor as the fluorescent probe for the detection of HgII in aqueous environments is encapsulated into mesoporous materials to avoid self‐quenching or aggregation in water. Determination of HgII is accomplished within a few seconds with high selectivity and sensitivity, reaching a limit of detection of 12 ppt. The determination of trace amounts of HgII in natural waters and in fish extracts is demonstrated by using our sensing material. The incorporation of the material into several μ‐PAD strips yields a portable, cheap, quick, and easy‐to‐handle tool for trace HgII analysis in water.

Synthesis and aggregation properties of boron-dipyrromethene dyes conjugated with guanine units

Two boron-dipyrromethene dyes bearing a conjugated guanine unit (G-BODIPYs) 1 and 2 were synthesized and fully characterized. The self-assembly properties of these dyes were investigated by X-ray crystallography, [Formula: see text]H NMR and UV-vis spectroscopy. As revealed by X-ray crystal structure studies, G-BODIPY 1 self-assembled into ribbon-like structures due to the intermolecular hydrogen bonding and [Formula: see text]–[Formula: see text] stacking interaction. Concentration-dependent [Formula: see text]H NMR experiments confirmed the formation of hydrogen bonds of the guanine units in solution for both dye 1 and 2. In the presence of K[Formula: see text], the characteristic signals for the formation of cyclic G-quadruplex structures were observed in the [Formula: see text]H NMR study. Aggregation of G-BODIPY dyes was further monitored by UV-vis absorption spectroscopy by varying the solvent polarity and temperature. H-type aggregates of dye 1, which was characterized by a new hypsochromically shifted absorption band with [Formula: see text] 461 nm, was obtained. In the presence of K[Formula: see text], the enhancement of stability was observed for the H-aggregates of dye 1.