Interconnection of Porphyrins in Langmuir−Blodgett and Self-Assembled Monolayers by Means of Silver Acetylide Bridges

Axial metal complexation was used in the organization of the cobalt(II) meso-tetra(trimethylsilylethynyl)porphyrin, CoPTMS, by the Langmuir−Blodgett (LB) technique or by self-assembly (SA). The axial ligand is a para-substituted pyridine that carries a long aliphatic chain, C18NHPy, in the case of the LB technique or a triethoxysilane group, SiPy, in the case of SA. In both cases, monomolecular films of nonaggregated porphyrins have been obtained and characterized by IR and UV spectroscopies, linear dichroism, and X-ray diffraction. A 1/1/5 mixture of CoPTMS, C18NHPy, and methyl eicosanoate spread on a silver nitrate subphase led to the formation of a silver acetylide polychelate of porphyrins. After transfer onto a solid substrate, the macrocycles displayed a flat-on orientation. The polychelate monolayers are robust enough to allow easy dissolution of the methyl eicosanoate filling molecule without disturbing the macrocycle orientation inside the LB film.