The semiempirical AM1 SCF method is used to study the first static hyperpolarizabilities of some novel mono-O-Hydroxy bidentate Schiff base in which electron donating (D) and electron accepting (A) groups were introduced on either side of the Schiff base ring system. Geometries of all molecules were optimized at the semiempirical AM1. The first static hyperpolarizabilities of these molecules were calculated using Hyperchem package. To understand this phenomenon in the context of molecular orbital picture, we examined the molecular HOMO and molecular LUMO generated via Hyperchem. The study reveals that the mono-O-Hydroxy bidentate Schiff bases have large values and hence in general may have potential applications in the development of nonlinear optical materials. 1. Introduction An intense research activity is currently associated with the synthesis and development of molecule-based second-order nonlinear optical (NLO) materials, involving organic chromophore and metal complexes [1–3]. The Schiff base compounds have been under investigation for several years because of their potential application to optical communications and because many of them have NLO behaviour [4, 5]. The design of efficient organic materials for the nonlinear effect is based on molecular units containing highly delocalized -electron moieties and extra electron donor and electron acceptor groups on opposite sides of the molecule at appropriate positions on the ring to enhance the conjugation. The effect of electron withdrawing and electron attracting substituents on the first hyperpolarizability of conjugated systems has received a great deal of attention in recent years [6, 7]. It was shown that the type of substituent plays a major role in charge transfer through the molecule and therefore in nonlinear properties [8]. Prasad and Williams [9] explained that the certain classes of organic materials exhibit extremely larger NLO and electrooptic effect. The design of most efficient organic materials for the nonlinear effect is based on molecular units containing highly delocalized pi-electron moieties and extra electron donor (D) and electron acceptor (A) groups on opposite sides of the molecule at appropriate positions on the ring to enhance the conjugation. The pi-electron cloud movement from donor to acceptor makes the molecule to be highly polarized. The chromophore design was mainly done by synthetic explorations which are time consuming and costly process. At the same time, measurement of the molecular nonlinear optical coefficients ( ) requires the use of the well-known
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