Investigation on Third-Order Nonlinear Optical Properties of Four Transition Metal Complexes Thin Films by Z-Scan Technique

Abstract

In this work, four new transition metal complexes, [Zn(PTP)]12(1,4-NDA)12·2H2O (1), [Zn(PTP) (4,4′-ODA)]2 (2), [Ni(PTP)(4,4′-ODA)]2 (3) and [Ni(FTP)]2Cl4 (4), have been synthesized by the reaction between a metal salt, Zn(II) or Ni(II), a rigid polycarboxylic ligand, naphthalene-1,4-dicarboxylic acid (1,4-NDA) or 4,4′-oxydibenzoic acid (4,4′-ODA) and a co-ligand, 4′-phenyl-2,2′:6′,2″-terpyridine (PTP) or 4′-(furan-2-yl)-2,2′:6′,2″-terpyridine (FTP). Complex 1 based on {Zn(PTP)(1,4-NDA)}n intertwined chains characterized by three different configurations which form a chiral chain structure. Complexes 2 and 3 present a structure made of discrete rings containing two central metal atoms. In Complex 4, two complex Ni(FTP)2+ ions are found to be connected with the μ2–Cl bridge to form a binuclear cluster. The third-order nonlinear optical properties of each complex thin film were evaluated by the Z-scan technique, indicating a strong third-order nonlinear reverse saturable absorption effect, with a high absorption coefficient β 3.89 × 10−6 for 1, 40.50 × 10−6 for 2, 4.76 × 10−6 for 3, and 1.37 × 10−6 m W−1 for 1, respectively. Interestingly, Complex 1 exhibits an effective nonlinear refractive effect with a refractive coefficient of 7.16 × 10−13 m2 W−1. The third-order NLO susceptibilities χ (3) of each complexes were calculated.