A dual approach to study the key features of nickel (II) and copper (II) coordination complexes: Synthesis, crystal structure, optical and nonlinear properties

Abstract

In the present study, we use a dual approach comprising of experimental and computational techniques to report the syntheses and characterizations of two novel nickel (II) [Ni(L)2] (1) and copper (II) [Cu(L)2] (2) coordination complexes, which are made through the coordination of 1-(E-(2, 4-dibromophenylimino) methyl) naphthalene-2-ol (HL) ligand. Several modern techniques including experimental electronic spectroscopy, single crystal X-ray crystallography and quantum computational methods are used to characterize the isolated coordination compounds. Both the complexes display a square planar trans-[MN2O2] coordination geometry, whose central M (II) atoms lie on the centre of symmetry. Complexes [Ni(L)2] (1) and [Cu(L)2] (2) crystallize in the monoclinic system of the space groups P21/c with a = 9.307(4)Å, b = 12.242(4)Å, c = 13.823(4)Å, α = 90°, β = 105.262(10)°, γ = 90° and Z = 2 for complex (1), a = 9.171(5) Å, b = 12.507(8) Å, c = 13.666(8) Å, α = 90°, β = 103.823(15)°, γ = 90°, and Z = 2 for complex (2). The ligand (HL) is coordinated as monobasic bidentate with N and O donor groups suitably oriented for forming two six membered chelate rings. State of the art quantum computations are performed at molecular and bulk levels to get structure-property relationships from molecule to materials. The molecular nonlinear optical (NLO) response properties including third-order polarizability (γ) are calculated using density functional theory (DFT) methods. The calculated γ amplitudes for the synthesized [Ni(L)2] (1) and [Cu(L)2] (2) complexes are found to be 444.09 × 10−36 and 567.03 × 10−36 esu, respectively. These γ amplitudes of [Ni(L)2] (1) and [Cu(L)2] (2) complexes are about 21 and 27 times larger than that of standard para-nitroaniline (PNA, a prototype NLO molecule), respectively, which show the potential of these complexes as efficient NLO materials. Additionally, several important optical parameters including dielectric function, reflective index, reflectivity, conductivity and loss function are calculated at bulk level using ab initio methods within periodic boundary conditions (PBC). The obtained results indicate that both coordination complexes has good optical and NLO properties, which may render the above entitled complexes as efficient candidates for optoelectronic and NLO device fabrications.