Cuminaldehyde-3-hydroxy-2-napthoichydrazone: Synthesis, effect of solvents, nonlinear optical activity, antioxidant activity, antimicrobial activity, and DFT analysis

Cooperativity of ESPT and Aggregation-Induced Emission Effects—An Experimental and Theoretical Analysis of a 1,3,4-Thiadiazole Derivative

“…Some of the identified spectroscopic effects include changes in spectral characteristics in complexes with transition metal ions [ 12 ], dynamics changes in lipid systems [ 13 , 14 ], or the emergence of dual fluorescence. Rationalization of the latter is usually based on the coexistence of multiple emissive states in different electronic and/or molecular structures, which is associated with the processes of excited-state proton transfer (ESPT) [ 15 ] and twisted intramolecular charge transfer (TICT) [ 16 , 17 ] or breaching the Kasha’s rule [ 18 ], as well as aggregation effects related to the formation of excimer systems [ 19 , 20 , 21 ] and aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE), typically attributed to restriction of intramolecular rotation (RIR) [ 22 ]. With regard to the particular group of 2,4-dihydroxyphenyl-substituted 1,3,4-thiadiazoles, dual fluorescence has been most commonly explained by referring to ESPT effects, more specifically excited-state intramolecular proton transfer (ESIPT) [ 23 , 24 , 25 ], i.e., a proton transfer occurring within the molecule itself, as well as aggregation [ 26 , 27 ].…”