Hexabranched Dendrimers Encapsulated Metallic Copper Nanoparticles and Their Catalytic Evaluation for the Conversion of Para-Nitrophenol to Para-Aminophenol

Two new hexanuclear copper (II) complexes, [Cu-6(G2hexpyD)(DMF)(24)](TFA)(12) and [Cu-6(G2hexbzaD)(DMF)(18)](TFA)(12), where G2hexpyD and G2hexbzaD are second-generation dendrimers (G = 2) and TFA is trifluoroacetate, have been synthesized. The prepared copper (II) complexes have been fully characterized. Furthermore, to prepare dendrimer encapsulated copper nanoparticles (G2dendrimer-CuNPs), metal ions were chemically reduced by NaBH4 in 2-methoxyethanol, which yielded zero-valent metal particles with a narrow size distribution. The catalytic reduction of para-nitrophenol to para-aminophenol by G2dendrimer-CuNPs was evaluated in the presence of NaBH4. The reduction reaction was completed in 3 min. The reaction progress was monitored by electronic absorption spectroscopy. The rate constant was calculated to be 0.0073 and 0.0079 s(-1) for G2hexbzaD-CuNPs and G2hexpyD-CuNPs, respectively. The results revealed that G2dendrimer-CuNPs exhibit high catalytic performance in the conversion of para-nitrophenol to para-aminophenol. Easy separation, low price, high recyclability and great efficiency are the main advantages of G2dendrimer-CuNPs that make them as the suitable catalysts for the catalytic reduction of para-nitrophenol.