A series of amphiphilic azo-methine dyes with different relative positions of electron-accepting groups, (E)-N-octadecyl-2-［2-(4-N,N-dimethylaminophenyl)azomethinyl］quinolinium iodide(QN2), (E)-N-octadecyl-4-［2-(4-N,N-dimethylaminophenyl)azomethinyl］quinolinium iodide(QN4) and (E)-N-octadecyl-6-［2-(4-N,N-dimethylaminophenyl)azomethinyl］ quinolinium iodide(QN6) were synthesized. These dye molecules were successfully transferred onto quartz by Langmiur-Blodgett(LB) technique. We studied the second-harmonic generation(SHG) of their monolayers and found that the effect of relative position of acceptor group on SHG can not be negligible.
