Kumar, YogeshSingh, Vishwa DeepakDwivedi, Bhupendra KumarSingh, Nikhil KumarPandey, Daya Shankar2025-01-302025-01-30202111440546https://dl.bhu.ac.in/ir/handle/123456789/25541The synthesis of Zn(ii) complexes (C1-C2) based on azo-Schiff base ligands 2-((E)-(phenyl-imino)methyl)-4-((E)-(2-(phenylthio)phenyl)diazenyl)phenol (L1) and 4-((E)-(2-(phenyl-thio)phenyl)diazenyl)-2-((E)-(p-tolylimino)methyl)phenol (L2) has been described. These have been thoroughly characterized by spectroscopic studies (IR, 1H, 13C, ESI-MS, electronic absorption, emission) and the structures of C1 and C2 have been determined by X-ray single crystal analyses. The ligands L1 and L2 exhibit reversible acid/base induced "ON-OFF-ON"switching in solution and solid state. Upon exposure to UV light (?, 365 nm) C1 and C2 display cis-trans photoisomerisation and after removal of light they transform to more stable trans-form. Electronic absorption and 1H NMR studies on C1 and C2 revealed rather rapid (1.27 � 10-1 s-1) photoisomerization for C2 relative to C1 (2.7 � 10-2 s-1) which has also been supported by theoretical studies (DFT). The rather fast photoisomerization for C2 compared to C1 may be related to a small energy gap between HOMO and LUMO levels for the respective isomers. � The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Articlehttps://doi.org/10.1039/d0nj03401k