STUDIES ON THE STRUCTURE OF LB FILMS OF P ORPHYRIN DERIVATIVES CONTAINING DIFFERENT SUBSTITUTED ALKYL CHAINS

Monolayers and LB films of three kinds of carboxylic acid substituted porphyrins without alkyl chain or with alkyl chains of different lengt h have been studied in this paper. Mean molecular areas were measured and found to increase as the alkyl chain length increased. UV - Vis sp ectrashow that Soret absorption bands of porphyrins in LB films have d ifferent red - shift compared with solution spectra. The polarized UV - Vis spectra show that the three kinds of porphyrins have the same or ientation in LB films. The LB monolayers were obtained by using subpha se lowing method, their UV - Vis spectra show the same characteristics as those in LB films obtained by using vertical dipping method. These results indicate that substituted alkyl chains have great influence o n mean molecular areas and the distance between porphyrin rings in mon olayers or LB films, but have no influence on porphyrin ring orientati on. The porphyrin ring orientation is determined by porphyrin and the substituted hydrophilic groups. The three kinds of porphyrins have the same orientation in monolayers at Cd2+ aqueous solution interface, to o, and the orientation preserved during the transfer.