The electronic and steric effects of aryl substituents and the influence of hydrogen bonding in Z-isomer stability of phenylazopyrazole derivatives have been investigated. In this regard, 38 substituted phenylazopyrazole derivatives and 6 N-methyl phenylazopyrazoles (with meta substitutions) have been synthesized. Their photoswitching behavior, photostationary states (PSS), and kinetics of thermal reverse isomerization were evaluated experimentally using UV-vis and NMR spectroscopic techniques. Furthermore, density functional theory (DFT) computations have been performed for more detailed insights. Despite the presence of substantial substituent effects inferred through Taft and Hammett relationships, the concentration dependency in controlling the isomerization rates has also been observed. Kinetics studies at different concentrations, solvent effects, and computations have confirmed the decisive role of hydrogen bonding and solvent-assisted tautomerism in this regard. Through this study, a complex interplay of steric, electronic effects and hydrogen bonding as factors in dictating the stability of Z-isomers in arylazo-1 H-3,5-dimethylpyrazoles has been demonstrated.

Tripodal triazole linked azo(hetero)arenes based photoswitchable catalysts T1-5 have been designed, synthesized and optimized for the tritylation reaction of benzylamine (BzNH2). Difference in the tritylation reaction rates/yields have been achieved...

In the recent decades, the investigations on photoresponsive molecular systems with multiple azoarenes are quite popular in diverse perspectives ranging from fundamental understanding of multiple photoswitches, supramolecular chemistry, and various application prospects. In fact, several insightful and conceptual designs of such systems were investigated with architectural distinctions. In particular, the demonstration of applications such as data storage with the help of multistate or orthogonal photoswitches, light modulation of catalysis via cooperative switching, sensors using supramolecular host-guest interactions, and materials such as liquid crystals, grating, actuators, etc. are some of the milestones in this area. Herein, we cover the recent advancements in the research areas of multiazoarenes containing systems that have been classified into Type-1 {linear, non-linear, and core-based (A)}, Type-2 {tripodal C 3symmetric (C3)} and Type-3 {macrocyclic (M)} structural motifs.

Two tripodal C 3 -symmetric photoswitchable molecular systems T1 and T2 are reported that have extended conjugation at external and internal positions using an acryl group. The influence of the extended π-bonds in their absorption properties, thermal relaxation of the photoisomers and their propensities in forming supramolecular self-assemblies have been explored through spectroscopy, and microscopic studies. In particular, the investigations on the self-assembly have been carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), polarized optical microscopy (POM), X-ray diffraction studies (XRD) and atomic force microscopy (AFM). Remarkably, the position of the acryl group influences the behaviour of the two target molecules in supramolecular assembly, and also in the formation of photoresponsive organic hydrogels or microcrystals.

We report the design, synthesis, and studies of light-induced shape-changing azomacrocycles. These systems have been incorporated with azobenzene photoswitches using alkoxy tethers and triazole units to afford flexibility and binding....