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Cassandra L Fraser - One of the best experts on this subject based on the ideXlab platform.
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Meta-Alkoxy-Substituted Difluoroboron Dibenzoylmethane Complexes as Environment-Sensitive Materials
2017Co-Authors: Margaret L. Daly, Christopher A Derosa, Caroline Kerr, Cassandra L FraserAbstract:The optical properties of meta-alkoxy-substituted difluoroboron Dibenzoylmethane dyes were investigated in solution and in the solid state. Meta-alkoxy substitution induced strong intramolecular charge transfer (ICT) from the oxygen-donating substituent to the halide and boron acceptors in the excited state, as compared to the π–π* transition that is observed with para-alkoxy substitution. The optical properties of para- and meta-substituted alkoxy boron dyes were evaluated by calculations, in dilute solution, and in solid-state films. When embedded in amorphous matrixes (e.g., PLA, PMMA, PS, cholesterol), all dyes showed fluorescence (F) and phosphorescence (P) emission. In this report, we show that meta-substitution resulted in enhanced solvatochromism and an increased phosphorescence-to-fluorescence ratio in solid-state films compared to analogous para-substituted samples. With enhanced phosphorescence intensity via the heavy-atom effect, iodo-substituted dyes were further studied in PLA–PEG nanoparticles. Oxygen calibrations revealed stronger phosphorescence and a greater oxygen-sensing range for the meta- versus para-alkoxy-substituted dyes, features that are important for oxygen-sensing materials design
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modulating mechanochromic luminescence quenching of alkylated iodo difluoroboron Dibenzoylmethane materials
Journal of Physical Chemistry C, 2016Co-Authors: William A Morris, Michal Sabat, Tristan Butler, Christopher A Derosa, Cassandra L FraserAbstract:Difluoroboron β-diketonate compounds exhibit solid-state luminescence phenomena. Among these are reversible mechanochromic luminescence (ML), aggregation induced emission (AIE), and mechanochromic luminescence quenching (MLQ). These properties can be tuned by alterations to the molecular structure. Dyes with varying halide substituents exhibit tunable ML, MLQ, and solid-state emission with high quantum yields. A series of difluoroboron Dibenzoylmethane (BF2dbm) dyes with iodide and alkoxyl substituents (BF2dbm(I)OR) were synthesized where R = CH3 (C1), C5H11 (C5), C6H13 (C6), C12H25 (C12), and C18H37 (C18)). The 4-iodo parent compound BF2dbm(I) (H) was made for comparison. By keeping the heavy atom static, the dependence of ML properties on alkyl chain length was probed. The hydrogen derivative is only weakly emissive as a solid and exhibited minimal mechanoresponsive behavior. In contrast, alkoxy dyes exhibited tunable ML and MLQ properties depending on the length of the alkyl chain. Longer chain dyes co...
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Modulating Mechanochromic Luminescence Quenching of Alkylated Iodo Difluoroboron Dibenzoylmethane Materials
2016Co-Authors: William A. Morris, Tristan Butler, Michal Sabat, Christopher A Derosa, Cassandra L FraserAbstract:Difluoroboron β-diketonate compounds exhibit solid-state luminescence phenomena. Among these are reversible mechanochromic luminescence (ML), aggregation induced emission (AIE), and mechanochromic luminescence quenching (MLQ). These properties can be tuned by alterations to the molecular structure. Dyes with varying halide substituents exhibit tunable ML, MLQ, and solid-state emission with high quantum yields. A series of difluoroboron Dibenzoylmethane (BF2dbm) dyes with iodide and alkoxyl substituents (BF2dbm(I)OR) were synthesized where R = CH3 (C1), C5H11 (C5), C6H13 (C6), C12H25 (C12), and C18H37 (C18)). The 4-iodo parent compound BF2dbm(I) (H) was made for comparison. By keeping the heavy atom static, the dependence of ML properties on alkyl chain length was probed. The hydrogen derivative is only weakly emissive as a solid and exhibited minimal mechanoresponsive behavior. In contrast, alkoxy dyes exhibited tunable ML and MLQ properties depending on the length of the alkyl chain. Longer chain dyes corresponded to smaller singlet triplet energy gaps, greater triplet emission enhancement (77 K), and longer recovery times after smearing under ambient conditions. Shorter chain dyes have a much greater affinity for the ordered emissive state, as confirmed by atomic force microscopy (AFM). Powder X-ray diffraction (XRD) was performed on pristine dye powders as well as drop-cast films to gauge crystallinity in various forms. Single crystal XRD analysis of the H and C5 dyes revealed significant differences in crystal packing and π–π stacked dimers for dyes bearing alkyl chains and dyes without alkyl chains. Unique I–I and F−π close interactions were discovered in the dye crystals
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Structure–mechanical property correlations in mechanochromic luminescent crystals of boron difluoride Dibenzoylmethane derivatives
International Union of Crystallography, 2015Co-Authors: Gamidi Rama Krishna, Cassandra L Fraser, Ramesh Devarapalli, Rajesh Prusty, Tiandong Liu, Upadrasta Ramamurty, Chilla Malla ReddyAbstract:The structure and mechanical properties of crystalline materials of three boron difluoride Dibenzoylmethane (BF2dbm) derivatives were investigated to examine the correlation, if any, among mechanochromic luminescence (ML) behaviour, solid-state structure, and the mechanical behaviour of single crystals. Qualitative mechanical deformation tests show that the crystals of BF2dbm(tBu)2 can be bent permanently, whereas those of BF2dbm(OMe)2 exhibit an inhomogeneous shearing mode of deformation, and finally BF2dbmOMe crystals are brittle. Quantitative mechanical analysis by nanoindentation on the major facets of the crystals shows that BF2dbm(tBu)2 is soft and compliant with low values of elastic modulus, E, and hardness, H, confirming its superior suceptibility for plastic deformation, which is attributed to the presence of a multitude of slip systems in the crystal structure. In contrast, both BF2dbm(OMe)2 and BF2dbmOMe are considerably stiffer and harder with comparable E and H, which are rationalized through analysis of the structural attributes such as the intermolecular interactions, slip systems and their relative orientation with respect to the indentation direction. As expected from the qualitative mechanical behaviour, prominent ML was observed in BF2dbm(tBu)2, whereas BF2dbm(OMe)2 exhibits only a moderate ML and BF2dbmOMe shows no detectable ML, all examined under identical conditions. These results confirm that the extent of ML in crystalline organic solid-state fluorophore materials can be correlated positively with the extent of plasticity (low recovery). In turn, they offer opportunities to design new and improved efficient ML materials using crystal engineering principles
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emission color tuning with polymer molecular weight for difluoroboron Dibenzoylmethane polylactide
Advanced Materials, 2008Co-Authors: Guoqing Zhang, Steven E Kooi, J N Demas, Cassandra L FraserAbstract:plays, [11] sensors [12] and molecular probes. [13] Another easy approach to dye emission color tuning takes advantage of solvatochromism. [14] Polar dyes in particular can be sensitive to the properties of their surroundings. The polarity or dielectric constant of the local medium, whether liquid [15] or solid state, [16,17] can affect the ground state or excited state energies of fluorophores. [18,19] In fact, intermolecular interactions are not restricted to fluorophores and solvents. For polar dyes, fluorophore‐fluorophore (F‐F) interactions can be so significant that their emission spectra may be adjusted with concentration. For example, emission from the laser dye DCM2 can vary from yellow to red when the relative concentration of DCM2 in TPD thin films changes from 0.9‐11wt%. [16] Polyester side chain grafted poly(aryleneethynylene)s also display different solid state emission colors as a function of the polyester/conjugated polymer dye ratio. [20] Recently, a single dye species was used to generate multicoloremissionon pre-patternedsolidsubstrates,basedon the transition energy differences associated with different dye aggregation states. [7] These are examples of luminescence
Ana Maria Goulart Azevedo Tozzi - One of the best experts on this subject based on the ideXlab platform.
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Toxicidade e atividade antioxidante de flavonoides das cascas das raízes de Lonchocarpus filipes
Química Nova, 2009Co-Authors: Érica L. Santos, Emmanoel V. Costa, Francisco A. Marques, Nelissa P. Vaz, Beatriz Helena L. N. Sales Maia, Eva G. Magalhães, Ana Maria Goulart Azevedo TozziAbstract:The phytochemical investigation of dichloromethane extract from root bark of Lonchocarpus filipes Benth (Leguminosae) afforded four flavonoids including three Dibenzoylmethane derivatives rarely found in nature. The structures were established based on their spectral data (1H and 13C NMR, 2D-NMR) as being: lanceolatin B (1), pongamol (2), (E)-7-O-methylpongamol (3) and (E)-9-O-methylpongamol (4). Compound (4) is described herein for the first time as a natural product. The extracts and the isolated compounds (1), (2) and (3) displayed high toxicity in the brine shrimp lethality assay. Only compound (2) showed antioxidant activity using a DPPH radical scavenging assay. This is the first report on the phytochemical study of Lonchocarpus filipes.
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Three Dibenzoylmethane derivatives from Lonchocarpus species
Phytochemistry, 1997Co-Authors: Aderbal F. Magalhães, Ana Maria Goulart Azevedo Tozzi, Eva G. Magalhães, Ivani S. Blanco, Marisa A. NogueiraAbstract:Abstract Three new Dibenzoylmethane derivatives were isolated from petrol extracts of the roots of Lonchocarpus latifolius and L. muehlbergianus . Molecular structures were determined from spectroscopic data, especially NMR techniques. An alkyl group bonded to the central carbon (C-8) of a natural Dibenzoylmethane, had not been found before. Spectral data analysis suggested a preponderance of the respective diketotautomers.
Hany Aziz - One of the best experts on this subject based on the ideXlab platform.
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Pure red phosphorescent OLED (PhOLED) based on a cyclometalated iridium complex with a Dibenzoylmethane (dbm) moiety as the ancillary ligand
Journal of Luminescence, 2014Co-Authors: Frédéric Dumur, Marc Lepeltier, Hossein Zamani Siboni, Pu Xiao, Bernadette Graff, Jacques Lalevée, Didier Gigmes, Hany AzizAbstract:A neutral heteroleptic iridium(III) complex bis(1-phenylisoquinoline) (Dibenzoylmethane)iridium(III) Ir(piq)2(dbm) bearing a Dibenzoylmethane (dbm) moiety as the ancillary ligand has been designed and investigated as an emitter in phosphorescent organic light emitting devices (PhOLEDs). To date, the family of dbm based complexes has only been scarcely investigated in OLEDs and only one complex of this family has been tested in electroluminescent devices. Interestingly, pure red devices were obtained with this emitter. PhOLEDswere fabricated at different dopant concentrations and the best device performances were obtained in the device with 8wt.% dopant concentration. Ir(piq)2(dbm) was characterized by UV-visible absorption and photoluminescence spectroscopy, cyclic voltammetry and theoretical calculations were also performed to support our experimental results.
Pu Xiao - One of the best experts on this subject based on the ideXlab platform.
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Wide bandgap iridium complexes varying by their ancillary ligands: influence on their electroluminescence properties
'Elsevier BV', 2015Co-Authors: Lepeltier Marc, Pu Xiao, Graff Bernadette, Morlet-savary Fabrice, Gigmes Didier, Lalevee Jacques, Dumur FredericAbstract:International audienceThree heteroleptic iridium(III) complexes comprising 1-methyl-3-propyl-5-(2,4,5-trifluorophenyl)-1H-1,2,4-triazole (tfpt) as the cyclometalated ligand and varying by their ancillary ligands were examined as triplet emitters for Phosphorescent OLEDs. Interestingly, major differences in device performances were obtained with these three isostructural complexes comprising Dibenzoylmethane (dbm), acetylacetone (acac) or pyridine-2-carboxylic acid (pic) as the ancillary ligands. Best OLEDs were fabricated with the Dibenzoylmethane-based iridium(III) complex. On the opposite, the picolinate and the acetylacetonate-based complexes gave moderate performances. To complement this work, theoretical calculations were carried out on the three complexes. The newly synthesized complex i.e., Ir(tfpt)(pic) was also characterized by UV–vis absorption and luminescence spectroscopy as well as cyclic voltammetr
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Pure red phosphorescent OLED (PhOLED) based on a cyclometalated iridium complex with a Dibenzoylmethane (dbm) moiety as the ancillary ligand
Journal of Luminescence, 2014Co-Authors: Frédéric Dumur, Marc Lepeltier, Hossein Zamani Siboni, Pu Xiao, Bernadette Graff, Jacques Lalevée, Didier Gigmes, Hany AzizAbstract:A neutral heteroleptic iridium(III) complex bis(1-phenylisoquinoline) (Dibenzoylmethane)iridium(III) Ir(piq)2(dbm) bearing a Dibenzoylmethane (dbm) moiety as the ancillary ligand has been designed and investigated as an emitter in phosphorescent organic light emitting devices (PhOLEDs). To date, the family of dbm based complexes has only been scarcely investigated in OLEDs and only one complex of this family has been tested in electroluminescent devices. Interestingly, pure red devices were obtained with this emitter. PhOLEDswere fabricated at different dopant concentrations and the best device performances were obtained in the device with 8wt.% dopant concentration. Ir(piq)2(dbm) was characterized by UV-visible absorption and photoluminescence spectroscopy, cyclic voltammetry and theoretical calculations were also performed to support our experimental results.
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Pure red phosphorescent OLED (PhOLED) based on a cyclometalated iridium complex with a Dibenzoylmethane (dbm) moiety as the ancillary ligand
'Elsevier BV', 2014Co-Authors: Dumur Frédéric, Pu Xiao, Lepeltier Marc, Graff Bernadette, Gigmes Didier, Lalevee Jacques, Zamani Siboni Hossein, Aziz HanyAbstract:International audienceA neutral heteroleptic iridium(III) complex bis(1-phenylisoquinoline) (Dibenzoylmethane)iridium(III) Ir(piq)2(dbm) bearing a Dibenzoylmethane (dbm) moiety as the ancillary ligand has been designed and investigated as an emitter in phosphorescent organic light emitting devices (PhOLEDs). To date, the family of dbm based complexes has only been scarcely investigated in OLEDs and only one complex of this family has been tested in electroluminescent devices. Interestingly, pure red devices were obtained with this emitter. PhOLEDswere fabricated at different dopant concentrations and the best device performances were obtained in the device with 8wt.% dopant concentration. Ir(piq)2(dbm) was characterized by UV-visible absorption and photoluminescence spectroscopy, cyclic voltammetry and theoretical calculations were also performed to support our experimental results
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Phosphorescent organic light-emitting devices (PhOLEDs) based on 1-methyl-3-propyl-5-(2,4,5-trifluorophenyl)-1H-1,2,4-triazole as the cyclometalated ligand: Influence of the ancillary ligand on the emissive properties
'Elsevier BV', 2014Co-Authors: Dumur Frederic, Pu Xiao, Lepeltier Marc, Graff Bernadette, Morlet-savary Fabrice, Gigmes Didier, Lalevee Jacques, Siboni Zamani Hossein, Aziz HanyAbstract:International audienceTwo heteroleptic iridium complexes have been designed with 1-methyl-3-propyl-5-(2,4,5-trifluorophenyl)-1H-1,2,4-triazole as the cyclometalated ligand and acetylacetone (acac) or Dibenzoylmethane (dbm) as the ancillary ligands. Interestingly, when tested as emitters for phosphorescent OLEDs (PhOLEDs), these two isostructural complexes that only have varying ancillary ligands exhibited completely different behaviors in devices. Notably, highly efficient PhOLEDs were only obtained with the complex bearing dbm as the ancillary ligand. To get a deeper insight in this unexpected behavior, TD-DFT calculations were carried out. The optical properties of the two complexes (UV–vis absorption and photoluminescence) and their electrochemical behaviors were also studied
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Concentration-insensitive phosphorescent organic light emitting devices (PhOLEDs) for easy manufacturing
'Elsevier BV', 2014Co-Authors: Dumur Frederic, Pu Xiao, Lepeltier Marc, Graff Bernadette, Gigmes Didier, Lalevee Jacques, Siboni, Hossein Zamani, Aziz HanyAbstract:International audienceTwo heteroleptic iridium(III) complexes Ir(piq)(2)(dbm) and Ir(btp)(2)(acac) have been tested as emitters for phosphorescent OLEDs (PhOLEDs). Interestingly, device performance exhibited a marked insensitivity to the dopant concentration. In this study, a Dibenzoylmethane (dbm)-based complex has also been tested for the first time as dopant for OLEDs. To evaluate the emissive properties of this new emitter belonging to a family of complexes that has not been investigated yet, identical devices were prepared with the well-known red dopant Ir(btp)(2)(acac) for comparison. The new complex Ir(piq)(2)(dbm) exhibited comparable performance to that obtained with Ir(btp)(2)(acac). (C) 2014 Elsevier B.V. All rights reserved
Eva G. Magalhães - One of the best experts on this subject based on the ideXlab platform.
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Toxicidade e atividade antioxidante de flavonoides das cascas das raízes de Lonchocarpus filipes
Química Nova, 2009Co-Authors: Érica L. Santos, Emmanoel V. Costa, Francisco A. Marques, Nelissa P. Vaz, Beatriz Helena L. N. Sales Maia, Eva G. Magalhães, Ana Maria Goulart Azevedo TozziAbstract:The phytochemical investigation of dichloromethane extract from root bark of Lonchocarpus filipes Benth (Leguminosae) afforded four flavonoids including three Dibenzoylmethane derivatives rarely found in nature. The structures were established based on their spectral data (1H and 13C NMR, 2D-NMR) as being: lanceolatin B (1), pongamol (2), (E)-7-O-methylpongamol (3) and (E)-9-O-methylpongamol (4). Compound (4) is described herein for the first time as a natural product. The extracts and the isolated compounds (1), (2) and (3) displayed high toxicity in the brine shrimp lethality assay. Only compound (2) showed antioxidant activity using a DPPH radical scavenging assay. This is the first report on the phytochemical study of Lonchocarpus filipes.
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Three Dibenzoylmethane derivatives from Lonchocarpus species
Phytochemistry, 1997Co-Authors: Aderbal F. Magalhães, Ana Maria Goulart Azevedo Tozzi, Eva G. Magalhães, Ivani S. Blanco, Marisa A. NogueiraAbstract:Abstract Three new Dibenzoylmethane derivatives were isolated from petrol extracts of the roots of Lonchocarpus latifolius and L. muehlbergianus . Molecular structures were determined from spectroscopic data, especially NMR techniques. An alkyl group bonded to the central carbon (C-8) of a natural Dibenzoylmethane, had not been found before. Spectral data analysis suggested a preponderance of the respective diketotautomers.