Bis(thio)carbohydrazone Luminogens with AIEE and ACQ Features and Their In Silico Investigations with SARS-CoV-2.

Herein, we report two novel multidentate luminogen proligands bis(3,5-diiodosalicylidene) carbohydrazone (H 4 L 1 ) and bis(3,5-diiodosalicylidene) thiocarbohydrazone (H 4 L 2 ), which are suitable candidates for biomedical applications. Though the thiocarbohydrazone H 4 L 2 shows aggregation caused quenching (ACQ), the carbohydrazone H 4 L 1 exhibits stronger fluorescence due to aggregation induced emission enhancement (AIEE). Molecular docking studies of H 4 L 1 and H 4 L 2 along with four similar (thio)carbohydrazones with the active sites of SARS-CoV-2 main protease 3CL pro reveals that the thiocarbohydrazones, in general, are showing better propensity compared to their oxygen analogues. Both the thiocarbohydrazones and the carbohydrazones, however, exhibit better binding potential at the active sites than that of some of the repurposed drugs such as chloroquine, hydroxychloroquine, lopinavir, ritonavir, darunavir and remdesivir. Also, the carbohydrazone H 4 L 1 can be a better bioprobe compared to H 4 L 2 as the former is found to have better binding potential with SARS-CoV-2 spike glycoprotein along with AIEE feature.