Synthesis and Functionalization of Porphyrins through Organometallic Methodologies

This review focuses on the postfunctionalization of porphyrins and related compounds through catalytic and stoichiometric organometallic methodologies. The employment of organometallic reactions has become common in porphyrin synthesis. Palladium-catalyzed cross-coupling reactions are now standard techniques for constructing carbon-carbon bonds in porphyrin synthesis. In addition, iridium- or palladium-catalyzed direct C-H functionalization of porphyrins is emerging as an efficient way to install various substituents onto porphyrins. Furthermore, the copper-mediated Huisgen cycloaddition reaction has become a frequent strategy to incorporate porphyrin units into functional molecules. The use of these organometallic techniques, along with the traditional porphyrin synthesis, now allows chemists to construct a wide range of highly elaborated and complex porphyrin architectures.

Synthesis and self-organization of fluorene-conjugated bisimidazolylporphyrin and its optical properties

A conjugated-bisimidazolylporphyrin bridged by bis(ethynylfluorene) was synthesized and organized into linear polymer through self-coordination having mean molecular weights, M_w and M_n, of ~2.1 × 10⁵ Da and ~1.6 × 10⁵ Da, respectively. A large two-photon absorption cross section value of 3.4 × 10⁵ GM (per dimer unit) was observed. This value was comparable to that of the previously reported self-assembled linear polymer consisting of butadiyne-bridged imidazolylporphyrins. The two-photon absorption properties could be controlled by tuning the wavelength and absorption intensity of the one-photon absorption.

Enhanced two-photon singlet oxygen generation by photosensitizer-doped conjugated polymer nanoparticles

We have prepared photosensitizer-doped conjugated polymer nanoparticles by using a reprecipitation method. The conjugated polymer, poly[9,9-dibromohexylfluorene-2,7-ylenethylene-alt-1,4-(2,5-dimethoxy)phenylene] (PFEMO), was used as the host matrix to disperse tetraphenylporphyrin (TPP). These TPP-doped PFEMO nanoparticles are stable and have a uniform size of ∼50 nm. Efficient intraparticle energy transfer from PFEMO to TPP has been observed. The TPP emission of the nanoparticles was found to be enhanced by 21-fold by PFEMO under two-photon excitation. Enhanced two-photon excitation singlet oxygen generation efficiency in the TPP-doped PFEMO nanoparticles has been demonstrated. Our results suggest that these photosensitizer-doped conjugated polymer nanoparticles can act as novel photosensitizing agents for two-photon photodynamic therapy and related applications.