Synthesis, Langmuir−Blodgett Film, and Second-Order Nonlinear Optical Property of a Novel Asymmetrically Substituted Metal-Free Phthalocyanine

Abstract

A novel asymmetrically substituted, soluble, metal-free phthalocyanine with only one reactive nucleophilic substituent of amine was synthesized for the first time by reduction reaction with sodium sulfide nonahydrate of the nitro group in nitrotri(tert-butylphthalocyanine, which was prepared by mixed condensation of two corresponding diiminoisoindolines. The compound can be separated by common column chromatography either on neutral Al 2 O 3 using chloroform/hexane as the eluting solvent or on silica gel using chloroform as the eluent. The structure was confirmed by elemental analysis, 1 H NMR, UV-vis, IR, and mass spectroscopy. Thermostability of the compound was checked by thermogravimetry analysis. Langmuir-Blodgett films of the compound were fabricated, and the configuration of the phthalocyanine molecules at the air-water interface was suggested in terms of the limiting area per molecule. Second-harmonic generation (SHG) from monolayer and multilayers was measured. The SH intensities of the monolayer relative to a Y-cut quartz wedge I 2w p-p and I 2w s-p are 1.97 x 10 -6 and 1.71 x 10 -7 , respectively. The second-order susceptibility (X (2) ) and the molecular hyperpolarizability (β)values of the monolayer are 3.33 x 10 -8 and 5.90 x 10 -30 esu, respectively.