Langmuir-Blodgett films of pyridinium-dicyanomethanide dyes mixtures with photobleachable absorption bands

We report on Langmuir-Blodgett (LB) films characterization of 4-[5-dicyanom ethanido)thien-2-yl]-N-(n-hexadecyl)pyridinium (C16H33-PDCNT), and 1-(N-(n- hexadecy]-4-pyridinio)-2-[5-(dicyanomethanido)thien-2-yl]ethene (C16H33-PDC NTE); LB films of the pure compounds and of the mixtures of the two compoun ds were prepared at 291 K: UV-vis investigation revealed the presence of ph otobleachable absorption bands, the ones at about 530 nm and 640 nm were du e to charge transfer transitions of the monomer of C16H33-PDCNT and C16H33- PDCNTE, respectively; the sharp, photobleachable ones shifted to shorter wa velengths were due to H-aggregates of the two compounds. By changing the mo lar ratios of the two compounds in the mixtures and in other cases by annea ling the LB films, the absorption maxima of the sharp, photobleachable band s due to H-aggregates could be tuned in the range 415-467 nm. These LB film s are thus very promising in view of optical data storage applications. (C) 1999 Elsevier Science B.V. All rights reserved.