The use of 1,3,5-triazines in dendrimer synthesis

Synthesis of Multi(metallo)porphyrin Dendrimers through Nucleophilic Aromatic Substitution on meso-Pyrimidinyl Substituted Porphyrins

A convergent synthetic strategy toward novel all-porphyrin dendrimers, which can be regarded as synthetic model systems of the natural photosynthetic light-harvesting antennae, was successfully explored. The dendron propagation, based on nucleophilic aromatic substitution reactions on a meso-dichloropyrimidinyl substituted porphyrin AB2 monomer, was carried out up to the second-generation dendron, and the used approach was proven to be compatible with the stepwise introduction of different metals in the successive generations. Three different metals (Pt, Zn, and Ni) could be introduced in the second-generation heptaporphyrin dendron. By applying analogous meso-dichloropyrimidinyl substituted porphyrin cores, novel multiporphyrin dendrimers were obtained.

Dendrimers Based on [1,3,5]-Triazines

A comprehensive and chronological account of dendrimers based on [1,3,5]-triazines is provided. Synthetic strategies to install the triazine through cycloaddition, cyclotrimerization, and nucleophilic aromatic substitution of cyanuric chloride are discussed. Motivations and applications of these architectures are surveyed, including the preparation of supra-molecular assemblies in the solution and solid states and their use in medicines, advanced materials, and separations when anchored to solid supports.

Porphyrin-Functionalized Dendrimers: Synthesis and Application as Recyclable Photocatalysts in a Nanofiltration Membrane Reactor

The convergent synthesis of a series of porphyrin-functionalized pyrimidine dendrimers has been accomplished by a procedure involving the nucleophilic aromatic substitution (NAS) as a key reaction step. The resulting dendritic porphyrin catalysts show high activity in the light-induced generation of singlet oxygen ((1)O2) from ground-state oxygen. These materials are synthetically useful photosensitizers for the oxidation of various olefinic compounds to the corresponding allylic hydroperoxides. Catalytic activities and regio- and stereoselectivities of the dendritic photosensitizers are comparable to those observed for mononuclear porphyrin catalysts. Recycling of the dendrimer-enlarged homogeneous photocatalysts was possible by solvent-resistant nanofiltration (SRNF) by using an oxidatively stable membrane consisting of a polysiloxane polymer and ultrastable Y zeolite as inorganic filler. Moreover, this membrane technology provides a safe way to isolate the hydroperoxide products under very mild conditions. The membrane showed high retention for the macromolecular catalysts, even in chlorinated solvents, but some oxidative degradation of the porphyrin units of the dendrimer was observed over multiple catalytic runs.