IONIC COMBINED NONLINEAR-OPTICAL BIS-CHROMOPHORE ZINC-COMPLEXES - LANGMUIR-BLODGETT-FILM AND 2ND-HARMONIC GENERATION STUDY

Two novel ionic combined amphiphilic nonlinear optical bis-chromophore zinc complexes: s(E)-[2-(4-dimethylaminophenyl)etheny]-1-octadecyl py ridinium 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-t hione-1,3-dithiol-4,5-dimercapto) zinc (4) were synthesized by combini ng a bis-negatively charged zinc complex anion: bis (2-thione-1,3-dith iol-4,5-dimercapto) zinc with a hemicyanine cation (E)-[2-(4-dimethyla mino phenyl) ethenyl]-1-octadecyl pyridinium (1) or a quinoline modifi ed hemicyanine (E)-[2(4-dimethyl amino phenyl) ethenyl]-1-octadecyl qu inolinium (2). Their Langmuir films at the air/water interface, the tr ansfer of the Langmuir films to form LB films and the vertical homogen eity of the LB films were investigated. The Langmuir films of the bis- chromophore complexes are more stable than their corresponding dye iod ides. Strong second-order nonlinearities from the LB monolayers were o bserved and the second-order susceptibilities (chi(zzz)((2))) were eva luated 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 Els evier Science Ltd.