441 research outputs found
Tailoring the Solid-State Fluorescence Emission of BODIPY Dyes by meso Substitution
No full text4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives bearing varied substituents at the meso position (i.e., CF3, CH3, COOR, CHO, CN, Cl, iPr) were synthesized to elucidate the structure-property relationships that give rise to emissive J-aggregates. Several new BODIPY derivatives can be added to the previously reported 1,3,5,7-tetramethyl-8-trifluoromethyl derivative to the list of those forming J-aggregates, in addition to other dyes that are emissive in the solid state without forming J-aggregates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Excimers Beyond Pyrene: A Far-Red Optical Proximity Reporter and its Application to the Label-Free Detection of DNA
No full textA family of organic chromophores that, like pyrene, forms emissive excimers is reported. Their chemical and photophysical properties are superior to pyrene for the design of chemo- and biosensors. Unlike hydrophobic pyrene, which requires excitation by cell-damaging UV irradiation, these polar dyes absorb strongly in the visible range, and their excimers emit brightly in the red to far-red region of the electromagnetic spectrum. The intensity of the emission signal is greatly increased upon formation of a preassociated dimer that is triggered upon aggregation or crystallization. In demonstration of the potential of this new family of excimer-forming dyes, a probe that is capable of detecting label-free DNA in water down to 10 pm and also doubles as a visualization agent for DNA in gel electrophoresis is reported
Amine-Reactive Activated Esters of meso-CarboxyBODIPY: Fluorogenic Assays and Labeling of Amines, Amino Acids, and Proteins
No full textFluorescence-based amine-reactive dyes are highly valuable for the sensing of amines and the labeling of biomolecules. Although it would be highly desirable, large changes in emission spectra and intensity seldom accompany the conjugation of known amine-reactive dyes to their target molecules. On the contrary, amide bond formation between amines and the pentafluorophenyl (2-PFP) and succinimidyl (2-NHS) esters of meso-carboxyBODIPY results in significant changes in emission maxima (Delta lambda: 70-100 nm) and intensity (up to 3000-fold), enabling the fast (down to 5 min) and selective fluorogenic detection and labeling of amines, amino acids, and proteins. This approach further benefits from the demonstrated versatility and high reliability of activated ester chemistry, and background hydrolysis is negligible. The large "turn-on" response is a testament of the extreme sensitivity of meso-carboxyBODIPYs to the minimal changes in electronic properties that distinguish esters from amides. Applications to the detection of food spoilage, staining of proteins on electrophoretic gels or in living cells, and the expedited synthesis of organelle-specific fluorescence microscope imaging agents are further demonstrated
Mesoionic Carbene (MIC)-Catalyzed H/D Exchange at Formyl Groups
No full textH/D exchange at formyl groups is the most direct approach for the synthesis of deuterated aldehydes. Platinum-group metal complexes have been employed to catalyze this transformation, with significant substrate scope limitations. Although N-heterocyclic carbenes can also activate the C- H bond of aldehydes through the formation of Breslow intermediates, benzoin condensation and other C-C-bond-forming pathways have so far outpaced synthetically useful H/D exchange. Investigation of the reaction of aldehydes with 1,2,3-triazolylidenes has revealed the reversible formation of Breslow intermediates and the inhibition of the condensation steps in methanol solvent. 1,2,3-Triazolylidenes catalyze the H/D exchange of aryl, alkenyl, and alkyl aldehydes in high yields and deuterium incorporation levels using deuterated methanol as an affordable D source. The unique properties of these mesoionic carbenes (MICs) enable a streamlined preparation of deuterated synthetic intermediates and pharmaco-phores that are highly valuable as mechanistic and metabolic probes
Anionic 1,2,3-triazole-4,5-diylidene: A 1,2-dihapto ligand for the construction of bimetallic complexes
No full textA super pyrazolate: Deprotonation of the flanking hydrogen of metal complexes of mesoionic carbenes (MICs) offers a simple and general route for the preparation of bimetallic complexes of a 1,2-dihapto anionic dicarbene ligand that is isoelectronic with widely used pyrazolate ligands, while conferring greater electron donation and stronger M-L bonds (see scheme). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Molecular Rotors for the Detection of Chemical Warfare Agent Simulants
No full textThe fluorogenic probe o-OH is able to detect and quantify orgariop-hosphoms nerve agent mimics in solution and in the vapor phase following immobilization on a solid substrate, making the system a suitable candidate for the field detection of chemical warfare agents. Detection is achieved by the suppression of internal rotation upon phosphorylation of a reactive phenolate, resulting in a large fluorescence "turn-on" response
Aggregation-induced emission enhancement of a meso-trifluoromethyl BODIPY via J-aggregation
No full textRapid, specific, and ultrasensitive fluorogenic sensing of phosgene through an enhanced PeT mechanism
No full textWe report the design of an enhanced PeT-based fluorogenic phosgene probe 1-CN comprising a BODIPY fluorescence reporter, and a catechol quencher at the meso-position acting as the phosgene reaction site. The fluorescent catechol-derived probe 1-CN specifically reacts with phosgene to result in a cyclic carbonate ester. The fast (< 3 s) reaction suppresses a reductive PeT quenching process, leading to a fluorescence turn-on signal (F/F-0 up to ca. 1300). The high sensitivity (LOD = 24 pM) of the probe is achieved by the precise adjustment of the energy levels of the frontier orbitals involved in the PeT
Instantaneous Colorimetric and Fluorogenic Detection of Phosgene with a meso-Oxime-BODIPY
No full textThe meso-oxime-substituted-1,3,5,7-tetramethyl BODIPY (1-oxime) was developed into a colorimetric and fluorogenic probe to selectively detect and quantify phosgene. The fast (<10 s) and sensitive (LOD = 0.09 ppb) phosgene detection is achieved by the conversion of the meso-oxime to the meso-nitrile, resulting in a large fluorescence turn-on response. The utility of 1-oxime was established for the visual detection of phosgene in solution and in a practical solid-state platform, making it a suitable candidate for on-site monitoring of phosgene gas exposure in the workplace. © 2017 American Chemical Society
Long-Range Order Self-Assembly of Conjugated Block Copolymers at Inclined Air-Liquid Interfaces
No full textHere, we report that long-range order, direction-controlled, ultrathin conjugated polymer films can be formed by the self-assembly of conjugated block copolymers (i.e., poly(3-hexylthiophene)-block-poly(ethylene glycol)) at inclined air-water interfaces. Structure analyses revealed well-aligned nanowire arrays of poly(3-hexylthiophene) with a dramatically increased ordered domain size compared to the polymer films formed on a flat water surface. The improved degree of order was attributed to the flow field created by the enhanced solvent evaporation at the top of the water contact line. Note that it is challenging to prepare such well-ordered and molecularly thin films of conjugated polymers by conventional fabrication methods. The long-range order polymer film showed hole mobility an order of magnitude higher than polymer films formed on a flat interface when implemented as an active layer of field-effect transistor devices. This study demonstrates that a simple interface modification can significantly impact the self-assembly process, structure, and function of polymer films formed at the air-liquid interface
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