Synthesis of conjugated polymer based in Zn(II) porphyrin bearing terminal alkynyl groups as photosensitizer

Porphyrins immobilized on a surface have been proposed for the photodynamic inactivation of microorganisms, considering economic and ecological subjects. In hospitals, surfaces are one of the main components of possible reservoirs of bacteria, which can cause a notable incidence in nosocomial infections. In this sense, the coating of surfaces with photosensitizers that are immobilized in a film are of great interest to maintain aseptic surfaces in public health.

In this study, 5,10,15,20-tetrakis-[4-(ethynyl)phenyl]porphyrin (TEP) was synthesized from the condensation of 4-(ethynyl)benzaldehyde and pyrrole catalyzed by boron trifluoride diethyl etherate in dichloromethane (DCM). After oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and purification, TEP was obtained in 38% yield. This porphyrin was metaled with zinc(II) acetate in DCM/methanol to produce the complex ZnTEP in 98% yield. Homocoupling reaction of terminal alkynes of ZnTEP to diynes was used to synthesize conjugated polymer organogel cocatalyzed by PdCl₂(PPh₃)₂ and CuI in THF. Solvent was evaporated to obtain xerogel and the SEM images showed microporous structure. In addition, spectroscopic and photodynamic studies indicated that the porphyrin unit retains its properties as photosensitizer. Thus, this polymer is an interesting material with potential applications to form photoactive aseptic surfaces.