905 Acta Chim. Slov. 2022, 69, 905–912 Ali et al.: Zinc(II) Complex Containing Oxazole Ring: Synthesis, ... DOI: 10.17344/acsi.2022.7682 Scientifc paper Zinc(II) Complex Containing Oxazole Ring: Synthesis, Crystal Structure, Characterization, DFT Calculations, and Hirshfeld Surface Analysis Karwan Omer Ali, 1,* Hikmat Ali Mohamad, 2 Tomas Gerber 3 and Eric Hosten 3 1 Department of Physics, College of Science, University of Halabja, Halabja 46018, Iraq 2 Department of Chemistry, College of Education, Salahaddin University, Erbil 44001, Iraq 3 Department of Chemistry, Faculty of Science, Nelson Mandela University, Port Elizabeth 6031, South Africa * Corresponding author: E-mail: karwan.ali@uoh.edu.iq Phone No. 009647503849284 Received: 07-12-2022 Abstract A new complex of Zn(II), with 5-chloro-2-methylbenzoxazole ligand (L), has been synthesized by the reaction of zinc dichloride with the ligand (L= C 8 H 6 ClNO) in ethanol solution: dichloridobis(5-chloro-2-methyl-1,3-benzoxaz- ole)-zinc(II), C 16 H 12 Cl 4 N 2 O 2 Zn. Te synthesized complex has been fully characterized by elemental analysis, molar con- ductivity, FT-IR, UV-Vis, and single-crystal X-ray difraction (XRD). Te XRD analysis reveals that the complex has a 1:2 metal-to-ligand ratio. Te zinc(II) complex has a distorted tetrahedral geometry with two coordinated nitrogen atoms from the ligand. Density Functional Teory (DFT) calculations were performed at the B3LYP level of theory using the LANL2DZ basis set for metal complex and the 6–31G(d) basis set for non-metal elements to determine the optimum ge- ometry structure of the complex, and the calculated HOMO and LUMO orbital energies were presented. A natural bond orbital (NBO) analysis was carried out on the molecules to analyze the atomic charge distribution before and afer the complexation of the ligand. Te Hirshfeld surface mapped over d norm , shape index, and curvature exhibited strong H... Cl/Cl...H and H...H intermolecular interactions as the principal contributors to crystal packing. Keywords: Zn(II), Benzoxazole, Distorted tetrahedral geometry, Hirshfeld surface analysis, NBO analysis, DFT calcu- lations 1. Introduction Benzoxazole is a bicyclic heterocyclic compound containing both oxygen and nitrogen atoms in which the benzene ring is fused to a 1,3-oxazole ring at po- sitions 4 and 5. 1 It is one of the most common heter- ocyclics in industry and scientifc research. 2 Transition metal ions have diferent binding forces with N and O atoms. 3 Commonly, N-donor oxazole groups have demonstrated excellent coordination ability with the frst-row transition metal ions. 4 Due to the variety of coordination modes and confgurations, N-heterocy- clic ligands are typically used as neutral ligands in the synthesis of metal complexes. 5,6 Counterions are used to balance the total charge when studying the neutral ligand, which not only afects the coordination modes of the metal ions but also the entire geometry of the met- al complex. 7,8 Most Zn(II) complexes show tetrahedral and distorted tetrahedral coordination geometries, in agreement with a d 10 electronic confguration. 9,10 Tus, the strategy of using neutral mono and bidentate lig- ands with metal halides to force tetrahedral geometry has been widely used for stabilizing Zn(II) complexes. Similarly, benzoxazole derivatives have also been used to stabilize zinc in a +2 oxidation state. 11 Because of their good emission properties and inexpensive cost com- pared to other d 10 metal complexes, zinc (II) complexes have been shown to be important candidates for elec- troluminescent applications. For example, the Zinc(II) complex of [(2-(2-hydroxyphenyl)benzoxazole)(2-me- thyl-8-hydroxyquinoline)] has been recognized as a blue-emitting zinc complex to fabricate stacked organic light-emitting diodes. 12 Changes in the intermolecular interactions between metal ions and ligands that are