Synthesis and first studies of the host-guest and substrate recognition properties of a porphyrin-tethered calix[6]arene ditopic ligand

摘要

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 C12 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). The synthesis and binding properties of a calix[6]arene bearing a porphyrin at its large rim are described. It is shown that the host-guest adduct with a long-chain diamine displays strongly enhanced stability relative to the adducts formed with monoamines, which reveals the multipoint nature of the binding process.