Design of new fluorinated bridged push–pull stilbenes and preparation of LB films for second harmonic generation in the blue domain†
In order to prepare alternating Y-type multilayers involving push–pull stilbenes giving second harmonic generation (SHG) in the blue domain, we have synthesized two new bridged compounds, 1 and 2, with the hydrophobic chain grafted onto the donor group. The photophysical properties of these dyes in both solution and LB films are reported. The SHG signal of monolayer LB films containing 1 and 2 are close to that of the analog 3 and 4 having the hydrophobic chain grafted onto the acceptor group. Finally, multilayer LB films based on one, two and four bilayers of 1/3 or 2/4 were prepared and the SHG measurements show a regular noncentrosymmetric arrangement for 2/4 films only.