Imidazole function appended Zn(II)-based complex with acetylsalicylic acid: Synthesis, characterization and its application as photocatalytic agent for degradation of organic dyes

A zinc (II) coordinated compound, formulated as [Zn(1-MeImi)₂(acetylsalicylic acid)₂], (1) (where,1-MeImi=1-methyl imidazole) was prepared by the reaction of Zn(NO₃)₂·6H₂O with acetylsalicylic acid and 1-methyl imidazole in methanol. It is structurally characterized by CHN analysis, FT-IR spectroscopy, and Single X-ray crystallography. The Zn(II) ion exhibits a four-coordination number with distorted square planar geometry. Each acetylsalicylic acid ligand coordinates in a monodentate way via O1 and O4, respectively, while 1-methylimidazole is bonded through its deprotonated nitrogen atoms. The prepared complex was applied for photocatalytic degradation of organic dyes like methylene blue (MB) and methyl orange (MO). Under optimized conditions, the effects of different operating parameters on photocatalytic activity were studied, revealing degradation efficiencies of 93.2 % for MB and 86.8 % for MO, respectively. Kinetic study indicates a straight line with R² value of 0.992 and 0.967 for MB and MO, respectively, showing the good linear fit of the pseudo-first-order model. The rate constant value for MB and MO were 0.0238 min^-1 and 0.0155 min^-1, respectively and the higher value of MB suggests that the degradation of MB is more facilitated by this designed catalyst. The plausible dye degradation mechanism is supported by the formation of three active species during the catalytic process. 2D fingerprint analysis indicated the six types of homo- and heteroatomic bonds contributing to the overall crystal arrangement within and between molecules. Intermolecular interactions H—H, H—C/C—H, and H—O/O—H are most prominent in the formation of the Hirshfeld surface.