Theoretical investigations of copper ion selectivity by new fluorescent chemo sensor based on carbazole-Schiff

In this work the most practicable complexes formed between Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) cations and 2-Amino-3-((Z)-((9-hexyl-9H-carbazol-yl)methylene)amino)maleonitrile. Since there was no crystallographic data for this ligand, an auxiliary molecule that was the most similar molecule to the original ligand was selected to determine the computational level and its X-ray data was used. Geometry optimization of auxiliary molecule was carried out using B3LYP functional by 3-21G, 6-31G, 6-31G(d), 6-31+G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311++G(d,p) basis sets without any symmetry constrain. The construction parameters of the optimized molecule were compared with the crystallography data. The mean absolute deviation (MAD) between DFT calculated results and those of the crystallographic data were determined. The B3LYP/6-31+G(d) computational level was selected as the best level with the least computational cost for complexation reaction. Formation of the complex in three modes was investigated and the best site of coordination was determined. The geometry optimization and frequency calculations was performed at B3LYP/6-31+G(d) level of theory in the gas phase then thermo-chemistry results, were improved via single point energy (SPE) calculations at higher level of theory. Polarized Continuum Model (PCM) was used to model the solvent medium. Thermo-chemistry data in the solution were collected at the B3LYP/6-31+G(d) computational level