Spectroscopic, DFT studies and electronic properties of novel functionalized bis-1,3,4-thiadiazoles

Improved electrochemical conversion of CO2 to multicarbon products by using molecular doping

The conversion of CO₂ into desirable multicarbon products via the electrochemical reduction reaction holds promise to achieve a circular carbon economy. Here, we report a strategy in which we modify the surface of bimetallic silver-copper catalyst with aromatic heterocycles such as thiadiazole and triazole derivatives to increase the conversion of CO₂ into hydrocarbon molecules. By combining operando Raman and X-ray absorption spectroscopy with electrocatalytic measurements and analysis of the reaction products, we identified that the electron withdrawing nature of functional groups orients the reaction pathway towards the production of C₂₊ species (ethanol and ethylene) and enhances the reaction rate on the surface of the catalyst by adjusting the electronic state of surface copper atoms. As a result, we achieve a high Faradaic efficiency for the C₂₊ formation of ≈80% and full-cell energy efficiency of 20.3% with a specific current density of 261.4 mA cm^-2 for C₂₊ products.

Boosting the mechanical strength and solubility-enhancement properties of hydroxypropyl-β-cyclodextrin nanofibrous films

2-hydroxypropyl-β-cyclodextrin (HPβCD) nanofiber films have high surface-to-volume ratio and show high dissolution rate of hydrophobic drugs. However, the solubility-enhancement effect of HPβCD films may not be enough to include an effective dose in a sublingually administrable film. Moreover, unmodified HPβCD films are very brittle and difficultly transported and/or handled. So, the addition of polyethylene glycol (PEG) as a plasticizer was suggested to improve their ultimate tensile strength (UTS) and solubilization of hydrophobic drugs. Accordingly, six nanofiber films were developed and characterized, using three molecular weights of PEG (400, 1500 and 6000 Da) with two concentrations each (1:100 and 2:100 PEG:HPβCD), in addition to the unmodified HPβCD nanofibrous film. The results revealed that adding 1:100 of PEG 400 increases the UTS (∼2-fold) and the average fiber diameter (AFD) (∼3-fold). Moreover, the addition of PEG 400 significantly increased the solubility of two hydrophobic model drugs; coumarin (up to 7.7-fold of the original solubility) and 2-nitroimidazole (up to 1.6-fold of the original solubility). However, with higher PEG concentration/molecular weight, both AFD and UTS of the films decreased. On the other hand, it was noted that the solubility of the two model drugs decreased upon using 1500-Da PEG, and then increased with 6000-Da PEG.

The origin of the longer wavelength emission in 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole and its analogue 2-phenylamino-5-(2-hydroxybenzono)-1,3,4-thiadiazole† ‡

In aqueous solution, 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT) was found to emit dual emission and the longer wavelength emission was assigned to the combination of aggregation and conformational change. In a number of molecules that possess an intramolecular hydrogen bond between the proton donor and the acceptor, the longer wavelength emission is often observed due to the emission from the tautomer formed by excited state intramolecular proton transfer (ESIPT). Therefore, an analogue of FABT, 2-phenylamino-5-(2-hydroxybenzono)-1,3,4-thiadiazole (PHBT), was synthesized to determine the origin of the longer wavelength emission. The luminescence of PHBT and its methoxy derivatives was studied and compared with that of FABT. Theoretical calculations were also performed on both FABT and PHBT. Based on the experimental and theoretical investigations, the nonexistence of the keto tautomer in the ground state and the origin of the longer wavelength emission are divulged.