2,8,12,18-Tetraethyl-3,9,13,17-tetra-m- and p-pyridylporphyrins have been synthesized via dipyrromethanes. They form strongly fluorescing planar monolayer leaflets in water. Upon titration with ferrocyanide the m-pyridylporphyrin adsorbs these anions and the fluorescence decreases drastically. One ferrocyanide ion quenches the fluorescence of about 50 porphyrin units. In the case of the p-isomer the quenching effect is much less pronounced. The zinc complex gives no defined monolayer in water, but assembles in the presence of equimolar amounts of ferrocyanide to a triple layer. Here, the central porphyrins are rotated into two different orthogonal positions: one of these porphyrin molecules provides its beta-pyridyl groups as axial ligands of the central zinc ions for the outer layers, the other takes part in a closed hydrophobic region, in which the beta-ethyl groups of two orthogonal porphyrin ligands interact. Transmission electron and atomic force microscopy were used to characterize this new type of molecular assembly.