Copper‐based Schiff Base Complex Immobilized on Core‐shell Fe₃O₄@SiO₂ as a magnetically recyclable and highly efficient nanocatalyst for green synthesis of 2‐amino‐4H‐chromene derivatives

Abstract

Fe3O4‐supported copper (II) Schiff‐Base complex has been synthesized through post‐modification with 1,3‐phenylenediamine followed by further post‐modification with salicylaldehyde and coordination with Cu(II) ion. The resulted Fe3O4@SiO2‐imine/phenoxy‐Cu(II) magnetic nanoparticles (MNPs) were characterized by various techniques including SEM, TEM, XRD, XPS, EDX, VSM, FT‐IR, and ICP. The catalytic activity as a magnetically recyclable heterogeneous catalyst for one‐pot, three‐component synthesis of 2‐amino‐4H‐chromene derivatives was examined. The catalyst is efficient in the reaction and can be recovered by magnetic separation and recycled several times without significant loss in the catalytic activity.

Magnetic Silica-Coated Picolylamine Copper Complex [Fe3O4@SiO2@GP/Picolylamine-Cu(II)]-Catalyzed Biginelli Annulation Reaction

“…As indicated in the resultant XPS analysis shown in Figure e, the Fe 2p spectrum displayed two peaks with binding energies of around 751.06 and 772.67 eV, which were ascribed to the peaks of 2p 3/2 and 2p 1/2 , respectively . Also, Figure f shows the high-resolution spectra of Si 2p peaks that can be deconvoluted into two peaks centered at 106.92 and 108.99 eV, which are attributed to Si–C and Si–O, respectively . As illustrated in Figure g, the N atoms contained in Fe 3 O 4 @SiO 2 @GP/Picolylamine-Cu­(II ) indicated N 1s XPS spectra at 405.01 and 405.25 eV corresponding to C–N and CN bonds, respectively …”

“…61 Also, Figure 11f shows the high-resolution spectra of Si 2p peaks that can be deconvoluted into two peaks centered at 106.92 and 108.99 eV, which are attributed to Si−C and Si−O, respectively. 59 As illustrated in Figure 11g, the N atoms contained in Fe 3 O 4 @SiO 2 @GP/Picolylamine-Cu(II) indicated N 1s XPS spectra at 405.01 and 405.25 eV corresponding to C−N and CN bonds, respectively. 59 Catalytic Activity Test.…”

“…In accordance with the literature, Cu species exist in the Cu(II) state in the prepared catalyst. 59 Also, the CuO XPS peak is typically at 945.02 eV. Figure 11d shows the electron binding energies related to O 1s with three peaks at 536.09, 537.63, and 539.02 eV, which are attributed to Fe−O, Si−O, and O−H, respectively.…”

“…Figure 11b illustrates the XPS spectra of C 1s in the structure of Fe 3 O 4 @SiO 2 @GP/Picolylamine-Cu(II) by two peaks at the binding energy of 290.1 (C−C) and 291.5 (C−O) eV. 58,59 The XPS spectrum presents the doublet peak to Cu 2p at around 938.18 eV and 948.72 eV that are attributed to Cu 2p 3/2 and Cu 2p 1/2 , respectively (Figure 11c). In accordance with the literature, Cu species exist in the Cu(II) state in the prepared catalyst.…”

Design of a Schiff Base Complex of Copper Coated on Epoxy-Modified Core–Shell MNPs as an Environmentally Friendly and Novel Catalyst for the One-Pot Synthesis of Various Chromene-Annulated Heterocycles

“…Also, XRD analysis (X’Pert-PRO advanced difractometer operated at 40 kV and 40 mA at r.t.) helped to investigate the crystalline structure of the catalyst. The EDAX spectrum was utilized for the elemental analysis of the Schiff base complex of copper coated on epoxy-modified Fe 3 O 4 @SiO 2 MNPs. − …”