Optical limiting efficiency of an electroactive bis-iminopyridine ligand and its zinc complex

Abstract

Abstract-An electroactive based bis-iminopyridine ligand has beensynthesized by a condensation reaction between (4-(6,7-dimethyldithiotetrathiafulvalene)-aniline) with 2,6-diformylpyridine. The complexation of this ligand with ZnCl2 afforded a tetrahedral neutral Zinc metal complex. Nonlinear optical measurements of these structures have given good results in a picosecond regime. The nonlinear absorption of the ligand was significantly enhanced upon complexation with ZnCl2. This prompted us to conduct an experiment of optical limiting at wavelength 532nm. The nonlinear absorption properties of these structures were studied and compared to the reference material C60.Intensive studies of nonlinear optics (NLO) have been induced by expected applicability of their results in optics, telecommunications and information processing. In this regard, π-conjugated chromophores reveal good processibility, electronic and optical properties [1][2][3][4] including intrinsic hyperpolarizability of 3-dicyanomethylene-5,5-dimethyl-1-[2-(4-hydroxyphenyl) ethenyl]-cyclohexene nanocrystallites incorporated into the photopolymer matrices with high third order optical properties [5]. The delocalized π-electrons give rise to ultrafast response times and large optical nonlinearity, which makes these materials attractive candidates for optoelectronic and photonic applications in optical computing, logic devices, optical switching and organic solar cells [6][7][8][9]. We were interested in the π-conjugated "Push-pull" organic chromophores containing a tetrathiafulvalene electron donating group and an iminopyridyl accepting fragment that can also act as a coordinating unit. This type of compound is of great interest since it gives the possibility to obtain multifunctional materials which may represent an interaction between two or more physical properties, such as magnetism and conductivity [11][12][13]. Ligands such as * E-mail: guezguezimen@yahoo.fr † E-mail: bouchta.sahraoui@univ-angers.fr iminopyridines have been chosen because of their ability to form a multitude of stable complexes and were, for example, used as catalysts for olefin polymerization [14][15]. In this work, we report on the optical limiting properties of an azo-based iminopyridine ligand and its associated zinc(II) complex.The experiments were investigated by means of the Zscan technique using 16ps mode-locked Nd:YAG lasers operating at 532nm at 10Hz. The details of the Z-scan technique and the procedure used for the determination of the NLO parameters have been described in details elsewhere [7]. Their nonlinear refractive and absorptive properties were measured and are compared with those of the C 60 fullerene.Different concentrations were investigated in order to study the effect of varying the concentration in the low and high excitation energy. Four concentrations (0.5mM, 1mM, 2mM and 1.5mm) were prepared for the ligand and the corresponding zinc(II) complex.The structure of the ligand (1) is composed of an extended π-conjugated system that incorporates tetrathiafu...