Selective Modulation of Internal Charge Transfer and Photoinduced Electron Transfer Processes in <i>N</i>‑Aryl-1,8-Naphthalimide Derivatives: Applications in Reaction-Based Fluorogenic Sensing of Sulfide

Three reaction-based fluorescent probes based on two new naphthalimide platforms were developed for the detection of H₂S. A new approach in detecting H₂S by the reduction of an azide to a triazene intermediate in aqueous media is reported. Given their design features, these chemodosimeters provide useful insights into the relatively unexplored area of C₀ spacers between receptor:reporter components. The <i>N</i>-aryl-1,8-naphthalimide platform features straightforward placement of the internal charge transfer and photoinduced electron transfer (PET) modulators on the same molecule. In the three examples presented, the <i>N</i>-aryl component proved to be an effective photophysical device as it allows the placement of a PET modulator at the strategically important and less explored imide position of 1,8-naphthalimides. These probes or dosimetric agents demonstrated good selectivity, two-signal response, and the desirable OFF–ON fluorescence response. By implementation of both the azido and nitro group as sulfide-reactive functionalities on the same chemosensory platform in probe SNAN-3, a much broader range of H₂S can be detected. Remarkably, probe SNAN-3 exhibits both a dual-emission and dual-response for the detection of sulfide in aqueous solution

N-Aryl Arenedicarboximides as Tunable Panchromatic Dyes for Molecular Solar Cells

Three organic dyes designed as molecular dyads were prepared that feature a common naphthalimide acceptor and N-aryl donors. One of these incorporated an additional cyanoacrylic acid linker and conjugated thiophene bridge inserted between donor and acceptor groups. Electrochemical and photochemical characterizations have been carried out on nanocrystalline TiO2 dye-sensitized solar cells which were fabricated with these dyes as the sensitizing component. HOMO and LUMO energies were also calculated using TDDFT methods and validated by the cyclic voltammetry method. A key finding from this study indicates that computational methods can provide energy values in close agreement to experimental for the N-aryl-naphthalimide system. Relative to HOMO/LUMO energy levels of N719, the dyes based on naphthalimide chromophore are promising candidates for metal-free DSSCs

Photocatalyzed Reduction of Bicarbonate to Formate: Effect of ZnS Crystal Structure and Positive Hole Scavenger

Zinc sulfide is a promising catalyst due to its abundance, low cost, low toxicity and conduction band position that enables the photoreduction of CO₂ to formic acid. This study is the first to examine experimentally the photocatalytic differences between wurtzite and sphalerite under the parameters of size (micrometer and nanoscale), crystal lattice, surface area, and band gap on productivity in the photoreduction of HCO₃^–. These photochemical experiments were conducted under air mass coefficient zero (AM 0) and AM 1.5 solar simulation conditions. We observed little to no formate production under AM 1.5, but found linear formate production as a function of time using AM 0 conditions. Compared to earlier reports involving bubbled CO₂ in the presence of bicarbonate, our results point to bicarbonate as the species undergoing reduction. Also investigated are the effects of three hydroxylic positive hole scavengers, ethylene glycol, propan-2-ol (isopropyl alcohol, IPA) and glycerol on the reduction of HCO₃^–. Glycerol, a green solvent derived from vegetable oil, greatly improved the apparent quantum efficiency of the photocatalytic reduction

Electronic Properties and Electroluminescent OLED Performance of Panchromatic Emissive <i>N</i>‑Aryl-2,3-naphthalimides

This report investigates the excited-state properties of a series of <i>N</i>-aryl-2,3-naphthalimides along with their fabrication into OLEDs and electroluminescence measurements. The <i>N</i>-aryl-2,3-NIs substituted specifically with chloro, fluoro, and methoxy substituents were chosen because of their unique propensity to display two emission bands or panchromatic fluorescence. Using the Lippert–Mataga analysis along with TD-DFT calculations, the excited states were determined to be n,π* and π,π*. The TD-DFT calculations on the geometries of the excited states indicate that the excited state shows a planar structure. The origin of both the short wavelength (SW) and long wavelength (LW) emission were correlated to specific geometries such that the SW emission originates from an “angled” structure in the excited state, and LW emission originates from an excited state of coplanar structure. All of the dyes investigated readily formed good films under ultrahigh vacuum deposition. The molecular energy levels of these compounds (HOMO and LUMO) were measured with cyclic voltammetry. Band gaps were also measured in both electrochemical and optical methods and indicate that the HOMOs of these fluorophores matched well with the anode (ITO work function), and their LUMOs matched well with the cathode (LiF/Al). To compare photoluminescence of the four dyes with their potential electroluminescence, three OLED devices were designed and fabricated. The electroluminescent spectra of these devices indicate that the panchromatic fluorescence, observed in solution, shifts toward the red in the solid-state. A plausible explanation appears to stem from an inability to inject electrons to the higher LUMO+1 orbitals; a process observed in the solution phase. Hence, the short wavelength fluorescence peak, a key component to panchromatic luminescence disappears in the OLED device. The observed EL spectrum from these smaller heteroatomic architectures is on par if not more broadly emissive than rubrene (5,6,11,12-tetraphenyltetracene), a red-colored C₄₂H₂₈ polycyclic aromatic hydrocarbon, that displays an orange-color E

Semiconductor Photocatalysis of Bicarbonate to Solar Fuels: Formate Production from Copper(I) Oxide

Copper-oxide-based photocatalysts, micron- and nanosized, and silver nanoparticle–copper oxide nanocomposites (Ag/Cu₂O) were characterized and evaluated for the first time in the application of bicarbonate conversion to formate. The Ag/Cu₂O nanocomposite yielded considerable production improvement over pure copper oxides due to the role of silver as a plasmonic sensitizer. We attribute these marked production improvements to plasmon-induced electron transfer from metal to semiconductor. These photocatalysts were studied in two different hole scavenger solvents (2-propanol and glycerol) using a solar simulator with air mass coefficient 1.5 and 0 (AM 1.5, AM 0) filters. Formate production increased significantly with AM 0 solar irradiation due to inclusion of the ultraviolet portion of the solar spectrum, and nanoparticulate Cu₂O showed improved photocatalysis relative to micron Cu₂O. Green chemistry solvent, glycerol, proved to be a far superior hole scavenger in comparison to 2-propanol

Tracking the migration of a nocturnal aerial insectivore in the Americas

Abstract Background Populations of Eastern Whip-poor-will (Antrostomus vociferous) appear to be declining range-wide. While this could be associated with habitat loss, declines in populations of many other species of migratory aerial insectivores suggest that changes in insect availability and/or an increase in the costs of migration could also be important factors. Due to their quiet, nocturnal habits during the non-breeding season, little is known about whip-poor-will migration and wintering locations, or the extent to which different breeding populations share risks related to non-breeding conditions. Results We tracked 20 males and 2 females breeding in four regions of Canada using geolocators. Wintering locations ranged from the gulf coast of central Mexico to Costa Rica. Individuals from the northern-most breeding site and females tended to winter furthest south, although east-west connectivity was low. Four individuals appeared to cross the Gulf of Mexico either in spring or autumn. On southward migration, most individuals interrupted migration for periods of up to 15 days north of the Gulf, regardless of their subsequent route. Fewer individuals showed signs of a stopover in spring. Conclusions Use of the southeastern United States for migratory stopover and a concentration of wintering locations in Guatemala and neighbouring Mexican provinces suggest that both of these regions should be considered potentially important for Canadian whip-poor-wills. This species shows some evidence of both “leapfrog” and sex-differential migration, suggesting that individuals in more northern parts of their breeding range could have higher migratory costs