Synthesis and First Studies of the Host-Guest and Substrate Recognition Properties of a Porphyrin-Tethered Calix[6]arene Ditopic Ligand

The synthesis and first host-guest investigations of a (Zn)porphyrin-tethered calixarene are described. The target compound was obtained by selective copper-catalyzed alkyne/azide cycloaddition at one position of a tris-azide-substituted calixarene using an alkyne-functionalized (Zn)porphyrin. After the complexation of zinc to the tris-imidazole site of the modified calixarene, the heteroditopic receptor showed a strong affinity for primary alkylamines, which formed host guest complexes within the cavity. This process is in competition with the binding of the amine at the apical coordination site of the (Zn)porphyrin. The use of a diamine (primary) with a C-12 aliphatic chain led to the formation of a heteroditopic complex, as evidenced by NMR and UV/Vis spectroscopy. This highlights the possibility of generating cooperative interactions between the three actors of the complex (calixarene <> guest <> porphyrin), a feature of great interest as it is reminiscent of the interactions governing enzymatic catalysis (recognition pocket <> substrate <> reactive center).