Pillar[5]arene-Derived Terpyridinepalladium(II) Complex: Synthesis, Characterization, and Application in Green Catalysis.

Metal nanoparticle catalysts have attracted great interest because they possess high surface-to-volume ratios and exhibit a very large number of catalytically active sites per unit area. However, high surface-to-volume ratios will induce nanoparticle aggregates during the catalytic reactions, making them lose their catalytic activity. In this work, a monoterpyridine-unit-functionalized pillar[5]arene (TP5) was synthesized successfully, which can be used as anchoring sites for the controllable preparation of well-dispersed palladium nanoparticles [TP5/Pd(0) NPs]. The as-prepared TP5/Pd(0) NPs were fully characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, and powder X-ray diffraction. Importantly, the ultrafine TP5/Pd(0) NPs are found to be excellent and reusable catalysts for the reduction of nitrophenols in aqueous solution.