Zinc-based solvents free coordination complexes: Synthesis, structures, photoluminous properties, DFT calculations and Hirshfeld surface analysis

Two novel Zn(II) complexes, [Zn(2-MeImi)2(benz)2] (1) and [Zn(2-MeImi)2(piv)2] (2) were prepared by the reaction of Zn(NO3)2.6H2O with 2-methylimidazole (2-MeImi) and benzoic acid (benz) / pivalic acid (piv) in CH3OH/H2O solvents in triethylamine. Both these coordination compounds were characterized by different methods like UV, IR, elemental analysis, thermogravimetric study and single X-ray crystallography. In (1) and (2), 2-methylimidazole and two carboxylates in each complex are coordinated and overall these complexes exhibit distorted tetrahedral geometry. Carboxylates (benz and piv) act as a monodentate ligands in 1 and 2, respectively. The photoluminescence (PL) properties of 1 and 2 were recorded at 230 nm and broad peaks in 1 and 2 might be due to presence of the instruct defect states of zinc. The weak peaks in both of the complexes can be imputed because the relaxation of electrons comes out of the higher energy level to lower. In complexes 1 and 2, the intermolecular interactions were investigated by 3D Hirshfeld surface analysis (dnorm, fragment patch, curvedness and shape index) and 2D fingerprint plots. DFT calculation was used to further investigate the structural parameters of these complexes and their electronic transitions which results of DFT calculation were compatible with experimental findings.

Automated summary

Two novel Zn(II) complexes, [Zn(2-MeImi)2(benz)2] (1) and [Zn(2-MeImi)2(piv)2] (2), were synthesized using Zn(NO3)2.6H2O, 2-methylimidazole (2-MeImi), benzoic acid (benz), and pivalic acid (piv). The complexes were characterized by UV, IR, elemental analysis, thermogravimetric study, and single X-ray crystallography. Both complexes exhibited distorted tetrahedral geometry with 2-methylimidazole and two carboxylates acting as coordinating ligands. Photoluminescence (PL) measurements showed broad peaks, suggesting the presence of defect states of zinc. Intermolecular interactions in the complexes were analyzed using 3D Hirshfeld surface analysis and 2D fingerprint plots. DFT calculation further confirmed the structural parameters and electronic transitions of the complexes, which were consistent with the experimental findings.