Investigating the effect of tuning the metal center in complexes for nonlinear optical application

Abstract

In this study, the new transition metal complexes, ML with M = Zn (II), Ni (II), and Pd (II) based on the N,N'-Bis[O-(diphenylphosphino)benzylidene)ethylenediamine ligand were successfully synthesized with a percentage yield of between 33 - 68%. As a result of fourier transform infrared spectroscopy (FTIR), UV-vis spectroscopy (UV-vis), and 1H nuclear magnetic resonance (proton NMR) was used to design and completely describe the metal complexes properties. Moreover, for computational study, the Gaussian16 software installed in the high-performance computer (HPC) is used for NLO calculation. The method used to perform this study is Density Functional Theory (DFT) method. 6-31G(d,p) basis set is used with LANL2DZ for zinc, nickel, and palladium along with the keyword 'GEN'. The molecular structure has been optimized and checked both bond length and bond angle before starting to run the calculation. Thus, NLO calculation had been performed. The dipole moment and the HOMO-LUMO energy gap were employed to verify the first hyperpolarizability, βtot, which can be utilized as an indication of second nonlinear optical characteristics. Transition metal-based complexes produce impressive results because they provide additional flexibility by offering charge transfer (CT) transitions between the metal and the ligands, resulting in a higher NLO response. Due to the charge transfer excitations, it was discovered that the nickel complex with 2.87 D had the largest NLO response (117215.66 x 10-30 esu), particularly in comparison with the zinc complex (2329.72 x 10-30 esu) and palladium complex (191.07 x 10-30 esu) with 6.52 D and 4.04 D values, respectively.