LANGMUIR-BLODGETT-FILMS OF A NEW PYRIDINIUM-DICYANOMETHANIDE DYE AND THEIR POTENTIAL OPTICAL APPLICATIONS

Fire report on Langmuir-Blodgett (LB) characterization of 5-(dicyanome thanidyl)thien-2-yl]-N-cetylpyridinium (C16H33-PDCNT). Surface pressur e-area isotherms of monolayers were investigated at T = 291 K. LB film s of Y- and Z-type were characterized by means of UV-vis and FTIR spec troscopies. The compound is photobleachable and undergoes a change in molecular structure in monolayer and in solution. The molecule strongl y absorbs in the visible region due to a charge transfer band both in homogeneous solution and LB films. Depending upon dipping conditions, a sharp absorption band appears at about 422 nm that could be attribut ed to molecular aggregates, probably of H-type. Both the 422 nm band a nd the broad charge transfer band at longer wavelength are photobleach able, and the former could have potential applications for optical dat a storage. The molecule seems to possess a large second-order hyperpol arizability, and non-centrosymmetric Z-type LB films could have promis ing nonlinear optical properties.