Theoretical modelling of the structure, reactivity, and the application of Co (II), Cu (II), and Ni (II) Schiff base complexes as sensor materials for phosgene (COCl₂) gas

Co(II), Cu(II), and Ni(II) quinolyl Schiff base complexes of (E)-1-(quinolin-2-yl)-N-(quinolin-8yl)methan- imine and (E)-2-((quinolin-8-ylimino)methyl)quinolin-8-ol that were designed here, have been the focus of theoretical simulations based on density functional theory at the (sic)B97XD/def2svp level of computation to examine their potential to act effectively as phosgene gas adsorbent materials. According to our findings for electronic properties, surfaces' energy gaps significantly increased during complexation with gas molecules. It was discovered that Ni(II) complexes improved in conductivity and stability on adsorption and Ni_Str01_Cl became more conductive. The variation of the HOMO and LUMO energies was graphically depicted in the density of State (DOS) plots. For all complexes, significant intramolecular interactions between filled and unfilled orbitals were observed. Co_Str02 also exhibited the maximum perturbation energies, which shows that it is stable for the investigated gas adsorption. The active sites realized from the MESP map are clear evidence of the adsorption capacity of the studied complexes Topology analysis suggests both the covalent nature and noncovalent nature of the interaction. Furthermore, the analysis of non-covalent interaction demonstrated weak bonded interaction of vdW type between metal complexes and gas molecule. This suggests good interaction between COCl2 gas molecule and adsorbing complexes. From our calculation, for adsorption energies, Ni-Str01_Cl is observed with negative adsorption energy -6.531 eV and a short distance which shows strong chemisorption with COCl2 gas molecule whereas positive adsorption energies are found for other complexes. Hence, Ni_Str01 is considered a better adsorbent compared to other surfaces. The groundwork for using quinolyl Schiff bases metal complexes to detect COCl2 gas molecules is laid by the current research.