Gram Scale Synthesis of Benzophenanthroline and Its Blue Phosphorescent Platinum Complex

The design, synthesis, and characterization of 12-phenyl­benzo­[<i>f</i>]­[1,7]­phenanthroline, Bzp, is reported. Its use as a fluorine-free ligand for sky blue phosphorescence is demonstrated in a cyclometalated platinum complex, BzpPtDpm. BzpPtDpm phosphoresces at the same wavelength as its analogous 4,6-difluoro­phenyl­pyridine complex at both room temperature (466 nm) and 77 K (458 nm). Finally, production of a conformationally restricted derivative of BzpPtDpm with greatly increased quantum yield (46%) validates the versatility of the synthetic route

Properties of Fluorenyl Silanes in Organic Light Emitting Diodes

Multifluorenyl silanes have been studied as potential hosts for organic light emitting diodes. Four molecules, (9,9′-dimethylfluoren-2-yl)nSi(phenyl)4-n (SiFln, n = 1, 2, 3, and 4), with an increasing number of fluorene units have been synthesized and investigated. These compounds possess high triplet energies (2.9 eV), large HOMO−LUMO gaps (∼5.2 eV), and high glass transition temperatures. Their glass transition and sublimation temperatures increase linearly as the fluorene ratio increases, but there are only small changes in their electrochemical or photophysical properties. These studies suggest that the Si center helps maintain the high singlet and triplet energy levels of these molecules. These materials exhibit ambipolar transport characteristics in undoped OLED devices, and the charge conductivity of the devices was enhanced by increasing the fluorene ratios in the host molecules. Compared with phenylsilanes, the fluorenylsilanes show better hole injecting and charge transporting abilities. SiFl4 was investigated as a host material for red, green, and blue phosphorescent devices, giving peak efficiencies of 8, 8, and 3%, respectively

Asymmetric Triaryldiamines as Thermally Stable Hole Transporting Layers for Organic Light-Emitting Devices

The synthesis of a series of asymmetric triaryldiamines has provided a number of materials with a wide range of thermal, electrochemical, and spectroscopic properties. The asymmetric materials described herein have two different diarylamine groups bound to a 1,4-phenylene or 4,4‘-biphenylene core, i.e., Ar1Ar2N−C6H4−NAr1‘Ar3 or Ar1Ar2N-biphenyl-NAr1‘Ar3, respectively. The diarylamines studied include diphenylamine, phenyl-m-tolylamine, naphthylphenylamine, iminostilbene, iminodibenzyl, and carbazole. These materials were prepared by copper- and palladium-catalyzed coupling of aryl halides and diarylamines. The asymmetry inherent in these compounds prevents these low molecular mass compounds from crystallizing, thus yielding higher thermal stability over that of the symmetric derivatives. In all cases, the asymmetric diamines form stable glasses, with glass transition temperatures up to 125 °C. HOMO levels for these materials, estimated by cyclic voltammetry, show a broad range of values, with oxidation potentials both lower and higher than those of common hole transport materials used in organic light emitting devices

Photocurrent Generation in Multilayer Organic−Inorganic Thin Films with Cascade Energy Architectures

Zirconium organobisphosphonate multilayer thin films of viologen derivatives were grown on copper dithiolate multilayers of 5,15-di(p-thiolphenyl)-10,20-di(p-tolyl)porphyrin (POR) and 5,15-di(p-thiolphenyl)-10,20-di(p-tolyl)porphyrinzinc (ZOR) on a variety of substrates (e.g. Au, SiO2), using solution depositions methods. The multilayer structures were studied by atomic force microscopy, UV−vis spectroscopy, and ellipsometry. In the case of copper dithiolate thin films, layer-by-layer lamellar growth with low surface roughness resulted, while higher surface roughness was observed in the growth of Zr viologen bisphosphonate films. Gold electrodes modified with zirconium bisphosphonate multilayers of viologen on top of copper dithiolate multilayers of porphyrin derivatives (ZOR or POR) were photoelectroactive and produced efficient and stable photocurrents using visible light. By arranging the zinc-porphyrin (ZOR) and the free base porphyrin (POR) donors in an energetically favorable fashion, according to their redox potentials and optical energy gaps, the photoinduced charge separation was improved, and higher photocurrent quantum yields (∼4%) and fill factor (∼50%) of the photoelectrode were achieved

Hydroxylated Quantum Dots as Luminescent Probes for in Situ Hybridization

Hydroxylated Quantum Dots as Luminescent Probes for in Situ Hybridizatio

Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly­(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times

Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly­(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times

Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly­(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times

Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly­(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times

Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host

Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly­(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times