Arylazo-3,5-diphenylpyrazole Derivatives: Molecular Probes Exhibiting Reversible Light-induced Phase Transitions for Energy Storage and Direct Photolithographic Patterning.

We report azopyrazole photoswitches decorated with variable N-alkyl and alkoxy chains (for hydrophobic interactions) and phenyl substituents on the pyrazoles (enabling π-π stacking), showing efficient bidirectional photoswitching and reversible light-induced phase transition (LIPT). Extensive spectroscopic, microscopic, and diffraction studies and computations confirmed the manifestation of molecular-level interactions and photoisomerization into macroscopic changes leading to the LIPT phenomena. Using differential scanning calorimetric (DSC) studies, the energetics associated with those accompanying processes were estimated. The long half-lives of Z isomers, high energy contents for isomerization and phase transitions, and the stability of phases over an extended temperature range (-60 to 80 °C) make them excellent candidates for energy storage and release applications. Remarkably, the difference in the solubility of the distinct phases in one of the derivatives allowed us to utilize it as a photoresist in photolithography applications on diverse substrates.

Azopyridinium Ionic Photoswitches: Tuning Half-Lives of Z Isomers from Seconds to Days in Water.

Herein, we describe water-soluble heteroaryl azopyridinium ionic photoswitches (HAPIPs). We aim to combine variations in five-membered heterocycles, their substitutions, N-alkyl groups at pyridinium nitrogen, the position of pyridinium center relative to azo group, counterions, and solvents, in achieving better photoswitching. Through these studies, we successfully tuned the half-life of Z isomers of the resultant HAPIPs between seconds to days in water. Extensive spectroscopic studies and density functional theory (DFT) computations unravelled the factors responsible for thermal relaxation behavior. Considering the versatility of these photoswitches, the tunability of half-lives and photoswitching in aqueous medium allows the scope of applications in several fields.

Functionalization of Endohedral Metallofullerenes toward Improving Barrier Height for the Relaxation of Magnetization for Dy2@C80-X (X = CF3, C3N3Ph2).

We theoretically studied the electronic and magnetic properties of the exterior functionalized endohedral metallofullerenes (EMFs) of Gd2@ I h-C80-X (where X is the exterior functional group). Molecular orbital analysis suggests that the presence of unpaired electron on the I h-C80 cage is not favoring the observation of stable species. One of the effective strategies to address this problem is by attaching an exterior functional group to the fullerene cage. Out of the studied exterior functionalized EMFs, we were successful in finding two stable species such as Gd2@ I h-C80-CF3 and Gd2@ I h-C80-C3N3Ph2 with no unpaired spin on the cage. Further, we utilized exterior functional groups such as -CF3 (1) and -C3N3Ph2 (2) to model and to stabilize dinuclear Dy2@ I h-C80 species, and we thoroughly investigated their magnetic properties using ab initio calculations. Within the single-ion paradigm, DyIII ions in 1 and 2 are magnetically anisotropic, and their magnetization-reversal energy barriers are estimated to be ∼698 and ∼705 cm-1, respectively. Furthermore, beyond the single-ion paradigm, i.e., considering a ferromagnetic coupling (∼30 cm-1) between the lanthanide ions and the radical spin, the energy barriers of 1 and 2 are estimated to be 79.8 and 73.0 cm-1, respectively.

Enhanced oxygen reduction activity of platinum subnanocluster catalysts through charge redistribution.

Single-size platinum Pt6 subnanoclusters exhibit superior mass-specific and surface-specific activities for the oxygen reduction reaction. The enhanced activity is attributed to polarized electron distributions based on rigorous structure characterization by X-ray absorption fine structure spectroscopy and density functional theory.