Ionic combined nonlinear optical bis-chromophore zinc complexes: Langmuir-Blodgett film and second harmonic generation study

Two novel ionic combined amphiphilic nonlinear optical bis-chromophore zinc complexes: bis(E)-[2-(4-dimethylaminophenyl)etheny]-1-octadecyl pyridinium bis (2-thione-1,3-dithiol-4,5-dimercapto)zinc (3) and bis(E)-[2-(4-dimethyl amino phenyl) ethenyl]-1-octadecyl quinolinium bis (2-thione-1,3-dithiol-4,5-dimercapto) zinc (4) were synthesized by combining a bis-negatively charged zinc complex anion: bis (2-thione-1,3-dithiol-4,5-dimercapto) zinc with a hemicyanine cation (E)-[2-(4-dimethylamino phenyl) ethenyl]-1-octadecyl pyridinium (1) or a quinoline modified hemicyanine (E)-[2(4-dimethyl amino phenyl) ethenyl]-1-octadecyl quinolinium (2). Their Langmuir films at the air/water interface, the transfer of the Langmuir films to form LB films and the vertical homogeneity of the LB films were investigated. The Langmuir films of the bis-chromophore complexes are more stable than their corresponding dye iodides. Strong second-order nonlinearities from the LB monolayers were observed and the second-order susceptibilities (chi(zzz)((2))) were evaluated to be 230 pm V-1 for 3 and 330 pm V-1 for 4, which were 1.9 or 1.7 times that of the corresponding dye iodide. Copyright (C) 1996 Elsevier Science Ltd.Physics, Condensed MatterSCI(E)EI10ARTICLE10739-7449