Journal of the Korean Chemical Society 2013, Vol. 57, No. 3 Printed in the Republic of Korea http://dx.doi.org/10.5012/jkcs.2013.57.3.311 -311- Halide (Cl - , Br - , I - ) Influence on the Electronic Properties of Macrocyclic Nickel(II) Complexes: Ab-initio DFT Study Seyed Amir Zarei * , Keivan Akhtari † , Keyumars Hassanzadeh, Mohammad Piltan, Saadi Saaidpour, and Marjan Abedi ‡ Department of Chemistry, Faculty of Science, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran. * E-mail: Seyedamirzarei@yahoo.com † Department of Physics, Sharif University of Technology, P.O.Box 11365-9161, Tehran, Iran ‡ Department of Chemistry, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran (Received January 16, 2013; Accepted March 19, 2013) ABSTRACT. The geometry structures of hexa-coordinated [NiLX]X complexes (X = Cl - , Br - , I - ) {L = 8,9,18,19-tetrahydro- 7H,17H-dibenzo[f,o] [1,5,9,13]dioxadiaza cyclohexadecine-8,18-diol} are optimized by density functional theory (DFT) using B3LYP/LANL2DZ. The calculated geometric parameters are in good agreement with the corresponding experimental values. Calculation results about these complexes show that dipole moment decreases, and the energy levels of HOMOs descend from iodo-complex to chloro-complex. The energy levels of HOMOs descend gently from iodo-complex to chloro-complex, while the energy levels of LUMOs in the present complexes are almost similar; therefore the energy gapes between HOMOs and LUMOs increased from iodo-complex to chloro-complex. Key words: Density functional theory, Nickel(II) complexes, Macrocyclic Schiff base, Halide, Electronic properties INTRODUCTION Macrocyclic ligands, in particular, those containing functional pendant arms and their metal complexes have been frequently investigated due to their potential appli- cations in different fields such as: catalysts, 1-3 discovery of new chemical sensors and optoelectronic devices, 4-8 advance- ment of bioinorganic chemistry to understand the chemistry of metallo-protein and produce useful new biomimetic reactions 9-12 and continuing development of basic coor- dination chemistry. 13-15 It has been found that the kind of central metal, its coordination environment, type of donor atoms and the conformation of macrocyclic ligands can influence these properties. 16 The precise insight for syn- thesizing such unique macrocyclic complexes is dependent on the precise understanding about electronic structure of these compounds which could lead to reach new compounds with high performance in the above-mentioned applica- tions. 17-21 Therefore, molecular orbitals (particularly, HOMO and LUMO) and their properties such as energy that are very important parameters for quantum chemistry would be very useful for physicists and chemists. 22-26 In our pre- vious works, 27,28 we have reported the synthesis of some nickel(II) complexes of two alcohol pendant arms mac- rocyclic potentially hexadentate ligand(L) (Scheme 1) with formula [NiLX]X (X = Cl - , Br - , I - ) and their molecular structures. In the present study, we report a theoretical research on the electronic structures of previously reported [NiLX]X (X = Cl - , Br - , I - ) complexes and the influence of coor- dinated halides on their electronic structures, using DFT- B3LYP/LANL2DZ. COMPUTAIONAL DETAILS The geometrical optimization and single point energy calculation were carried out using GAUSSIAN03 29 program. The density functional theory (DFT) with Unrestricted Becke’s three parameters(B3) exchange functional along with the Lee–Yang–Parr(LYP) non-local correlation func- tional (UB3LYP) 31,32 the Los Alamos LANL2DZ 31-33 effec- tive core pseudo-potentials (ECP) and valence double Zeta basis set. Scheme 1.