A novel class of Mx-Sr-Nb-Oy+δ (M = Cr3+, Cu2+, Zn2+, Ag+ and Cd2+) nanocomposites as catalyst for the synthesis of 2-amino-4H-chromene derivatives under ultrasound and microwave irradiations

Abstract

Fabrication of some transitional metals doped into Nb2O5-Sr2Nb2O7-SrCO3 nanocomposites via a simple and low-cost solvothermal route is reported. Sr(NO3)2, Nb2O5, Cr(NO3)3.9H2O, Cu(NO3)2.3H2O, Zn(NO3)2.6H2O, AgNO3 and Cd(NO3)2.4H2O were used as raw materials at 200 °C for 96 h. Rietveld analysis data revealed that the synthesized nanocomposites were mainly crystallized in tetragonal (Nb2O5) and orthorhombic (Sr2Nb2O7) crystal systems. According to the data, it was found that Nb2O5 was the main phase and no dopant crystal phase was found separately in the mixture. Field emission scanning electron microscope (FESEM) images revealed that the synthesized materials had rod and particle morphologies. Vibrating-sample magnetometer (VSM) analysis showed that the as-synthesized nanomaterials had ferromagnetic behavior. Ultraviolet–visible (UV–Vis) spectra indicated that the synthesized nanocomposites had absorption in the ultraviolet and visible light regions. The photoluminescence (pL) spectra showed that the as-prepared nanocomposites had considerable optical emissions in violet, blue, green and yellow regions. The catalytic performance of the synthesized nanomaterials was studied for the synthesis of 2-amino-4H-chromene derivatives under ultrasound and microwave irradiations. The reaction parameters such as reaction time, temperature, solvent type and catalyst amount were optimized. The data showed that the optimum reaction time, temperature, catalyst amount, frequency and solvent type are 10 min, 60 °C, 10 mol%, 50 kHz and H2O under ultrasound and 11 min,10 mol% and solvent-free under microwave irradiation for model reaction. Studying the kinetic model of the chromene reactions revealed that the reactions followed a pseudo-first-order kinetic model in the two reaction conditions under ultrasound and microwave irradiations.