AbstractA new amphiphilic BF2-azadipyrromethene (aza-BODIPY) dye 1 has been synthesized using a CuI-catalyzed “click” reaction. For this dye, two self-assembly pathways that lead to different type of J-aggregates with distinct near-infrared optical properties have been discovered. The metastable off-pathway product displays a broad, structureless absorption band while the thermodynamically stable on-pathway aggregate exhibits the characteristic spectral features of a J-aggregate, that is, red-shifted intense absorption band with significantly narrowed linewidth. The morphology and structure of the aggregates were studied by atomic force microscopy, transmission and scanning electron microscopy. The aggregation processes of 1 were investigated by temperature- and concentration-dependent UV/Vis spectroscopy and evaluated by models for cooperative self-assembly.

AbstractA new amphiphilic BF2-azadipyrromethene (aza-BODIPY) dye 1 has been synthesized using a CuI-catalyzed “click” reaction. For this dye, two self-assembly pathways that lead to different type of J-aggregates with distinct near-infrared optical properties have been discovered. The metastable off-pathway product displays a broad, structureless absorption band while the thermodynamically stable on-pathway aggregate exhibits the characteristic spectral features of a J-aggregate, that is, red-shifted intense absorption band with significantly narrowed linewidth. The morphology and structure of the aggregates were studied by atomic force microscopy, transmission and scanning electron microscopy. The aggregation processes of 1 were investigated by temperature- and concentration-dependent UV/Vis spectroscopy and evaluated by models for cooperative self-assembly.

A new class of biomimetic J-aggregate based on an amphiphilic BF2-azadipyrromethene dye is reported by Z. Chen, F. Würthner, et al. in their Communication on page 5729 ff. The J-aggregate (aggregate II) is formed via kinetically favored metastable aggregate I intermediate and characterized by a sharp and intense J-band at 799 nm. The optical properties and the rod-like morphology of aggregate II resemble those of the natural bacteriochlorophyll J-aggregates found in chlorosomes of green bacteria.

Four near-infrared (NIR) boron-azadipyrromethene (aza-BODIPY) dyes 5a–d bearing tetraphenylethylene- and fluorenyl substituents at the 1,7-position or 3,5-position were synthesized and characterized by 1H NMR, 13C NMR and HRMS. The single crystal structure of compound 5c was studied by X-ray crystallography. UV/vis and fluorescence spectroscopic studies of the aza-BODIPY dyes 5a–d indicated that the absorption and emission maxima of these dyes were bathochromically shifted up to 48 nm in comparison with that of the 1,3,5,7-tetraphenyl aza-BODIPY. Moreover, fluorescence quantum yields up to 0.45 were observed for the new dyes. The redox properties of these dyes were investigated by cyclic voltammetry. The observed optical and electrochemical properties of these dyes were further elucidated by the DFT calculation of the frontier molecular orbitals. Owing to their outstanding fluorescence properties, these dyes can be applied as fluorescence imaging probes for living cells.

A series of boron-dipyrromethene dyes (BODIPYs) 4a–g with different thienyl moieties at 2,3,5,6-positions of the BODIPY core were synthesized by the Stille cross-coupling reaction. The new compounds were characterized by 1H NMR, 13C NMR, HRMS, and IR spectroscopy. The single crystal structure of compound 4e was obtained by X-ray crystallography. The optical and electrochemical properties of these dyes were studied by UV/Vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. The DFT calculation of the frontier molecular orbitals of these dyes corroborates the observed effects of peripheral substituents on the optical and redox properties. These results reveal a good tunability of the optical and electronic properties of these BODIPYs by varying the peripheral groups at the α-positions of thienyl moieties, which leads to the absorption and emission reaching the NIR region.

Eine neue Klasse biomimetischer J-Aggregate basierend auf einem amphiphilen BF2-Azadipyrromethen-Farbstoff stellen Z. Chen, F. Würthner et al. in ihrer Zuschrift auf S. 5823 ff. vor. Das J-Aggregat (Aggregat II) entsteht über eine kinetisch bevorzugte, metastabile Zwischenstufe (Aggregat I) und ist durch eine scharfe und intensive J-Bande bei 799 nm charakterisiert. Die optischen Eigenschaften und die stäbchenförmige Morphologie des Aggregats II erinnern an natürliche Bakteriochlorophyll-J-Aggregate in Chlorosomen von Grünen Bakterien.

In this work, magnetic field driven polymer microplate arrays are fabricated to modulate the optical properties of the sample, i.e. reflectance and fluorescence. Inspired by poplar leaves, which rotate the high reflectance white side of the leave upwards to act as a “roof” under strong light radiation, and switch the low reflectance green side for photosynthesis back again when the light is less severe. In this study, gold was selectively deposited on one side of the microplate, and surface reflectivity can be reversibly switched from higher to lower state through the change of the magnetic field direction to bend the microplates with the gold side facing up and down. The modulation of fluorescence emission is realized by magnetically control the tilting angle of the microplates, in the same way as a venetian blind. The fluorescence intensity reaches its maximum and minimum at the perpendicular and parallel position to the fluorescent substrate, respectively. This system provides a fast responding and remote controllable means to modulate the optical properties of samples, which has been considered important in certain applications, such as smart reflectors, environmentally friendly windows, and field emission.

Co-self-assembled vesicular nanoparticles of two structurally comparable amphiphilic boron-dipyrromethene (BODIPY) dyes with dequenchable dual colour fluorescence were prepared for ratiometric imaging of live cells.

A new amphiphilic boron-dipyrromethene (BODIPY) dye 1 with a hydrophobic wedge at the meso-position and two hydrophilic cationic moieties at boron was synthesized. Temperature- and concentration-dependent UV/Vis spectroscopic studies in water were conducted to explore the self-assembly process of the dye. Detailed analysis of the data using two different models (developed by Van der Schoot et al. and Goldstein et al. respectively) for cooperative supramolecular polymerization indicates distinctly a nucleation–growth mechanism of the aggregation of dye 1 and the nucleus size (ca. 12–18 molecules) and a cooperativity factor (ca. 0.01) could be derived. Further investigation by transmission electron microscopy, scanning confocal microscopy, and X-ray diffraction revealed a unique vesicular morphology of the aggregates with multilamellar wall structure. Meanwhile, these dye vesicles exhibit unique optical characteristics, i.e. red-shifted sharp absorption band, narrowed emission linewidth, and increase in fluorescence quantum yield, as compared with the monomeric dye.

Nanohybrids from waterborne polyurethane (WPU), poly(vinyl alcohol) (PVA) and silver nanoparticles (AgNPs) with ultrasmall sizes (5.1 ± 0.6 nm) are facilely obtained by directly one-step dual-spinneret electrospinning fabrication from water. SEM and TEM images indicated the nanofibre morphology as designed. Moreover, the elemental distribution mapping indicated the good mixture of WPU/PVA and PVA/AgNPs nanofibers in the mats via such dual-spinneret technique. Also the thermal stability and biocidal activity of the hybrid nanofibers were greatly enhanced by the addition of WPU component and incorporation of Ag nanoparticles without increase of cytotoxicity.

In recent years, boron-dipyrromethene (BODIPY) and boron-azadipyrromethene (aza-BODIPY) dyes have attracted considerable multidisciplinary attention due to their diverse applications. By introducing various hydrophilic groups, such as quaternary ammonium, sulfonate or oligo-ethyleneglycol moieties into the BODIPY core, the solubilities of these dyes in aqueous solution can be greatly improved while maintaining their high fluorescence quantum yields. Accordingly, applying these fluorescent dyes in aqueous systems to areas such as chemosensors, biomacromolecule labeling, bio-imaging and photodynamic therapy has been achieved. In this article, the recent progress on the synthesis, optical properties and application of water-soluble BODIPY dyes and aza-BODIPY dyes is reviewed.

Penicillin sulfoxide is the intermediate for the synthesis of 7-amino-3-desacetoxycephalosporanic acid which is one of the most important nucleuses of cephalosporin antibiotic. In this contribution, two crystal structures of penicillin sulfoxide (forms I and II) were determined by X-ray diffraction, and their thermotropic properties were investigated by differential scanning calorimetry (DSC). Furthermore, the transformation of form II to form I was studied quantitatively by Raman spectroscopy, and its rates at different temperatures were determined. The results indicate that penicillin sulfoxide is more stable as form I, and the temperature plays an important role in the crystal transformation.

A new amphiphilic boron-dipyrromethene (BODIPY) dye 1 with a hydrophobic wedge at the meso-position and two hydrophilic cationic moieties at boron was synthesized. Temperature- and concentration-dependent UV/Vis spectroscopic studies in water were conducted to explore the self-assembly process of the dye. Detailed analysis of the data using two different models (developed by Van der Schoot et al. and Goldstein et al. respectively) for cooperative supramolecular polymerization indicates distinctly a nucleation–growth mechanism of the aggregation of dye 1 and the nucleus size (ca. 12–18 molecules) and a cooperativity factor (ca. 0.01) could be derived. Further investigation by transmission electron microscopy, scanning confocal microscopy, and X-ray diffraction revealed a unique vesicular morphology of the aggregates with multilamellar wall structure. Meanwhile, these dye vesicles exhibit unique optical characteristics, i.e. red-shifted sharp absorption band, narrowed emission linewidth, and increase in fluorescence quantum yield, as compared with the monomeric dye.

Co-self-assembled vesicular nanoparticles of two structurally comparable amphiphilic boron-dipyrromethene (BODIPY) dyes with dequenchable dual colour fluorescence were prepared for ratiometric imaging of live cells.

A series of boron-dipyrromethene dyes (BODIPYs) 4a–g with different thienyl moieties at 2,3,5,6-positions of the BODIPY core were synthesized by the Stille cross-coupling reaction. The new compounds were characterized by 1H NMR, 13C NMR, HRMS, and IR spectroscopy. The single crystal structure of compound 4e was obtained by X-ray crystallography. The optical and electrochemical properties of these dyes were studied by UV/Vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. The DFT calculation of the frontier molecular orbitals of these dyes corroborates the observed effects of peripheral substituents on the optical and redox properties. These results reveal a good tunability of the optical and electronic properties of these BODIPYs by varying the peripheral groups at the α-positions of thienyl moieties, which leads to the absorption and emission reaching the NIR region.