Monolayers of 5,10,15,20-tetra-4-oxy(acetic acid) phenyl porphyrin (TAPP) and TAPP/Dimethyldihexadecylammonium bromide (DMDHA) (molar ratio: 1:1, 1:4) at the air/liquid interface and on quartz plates have been studied by using π-A isotherms, UV-vis spectra and polarized UV- vis spectra. The interaction between porphyrin rings is stronger in pure TAPP monolayer, and the distance between the macrocycles was deduced to be about 0.55 nm. The distance between the macrocycles does not change obviously in the 1:1 complex monolayer, but the distance between the adjacent aggregates increased. In the 1:4 complex monolayer , the distances between the macrocycles in the same aggregate and between the adjacent aggregates increased significantly, and the interactions between porphyrin rings became weaker.

Key words: PORPHYRIN, MONOLAYER, STRUCTURAL ANALYSIS, ORIENTATION