Peripheral Ruthenium(II) Complexes and Orthogonal, Ferrocyanide-Linked Bilayers of (β-Tetraethyl-β-p- and m-Tetrapyridyl)porphyrins in Bulk Water

• Published in: Langmuir 1999-07, Vol.15 (15), p.5029-5039
• Main Authors: Donner, Dan, Böttcher, Christoph, Messerschmidt, Christian, Siggel, Ulrich, Fuhrhop, Jürgen-Hinrich
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solution properties; Solutions
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la981791+

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 β-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 β-ethyl groups of two orthogonal porphyrin ligands interact. Transmission electron and atomic force microscopy were used to characterize this new type of molecular assembly.