Synthesis, spectral characterization, and catalytic efficiency of aroylhydrazone-based Cu(ii) complexes

A series of copper(II) complexes [Cu(DKMB)Cl] (1), [Cu(DKMB)NO3] (2), [Cu(APMBH)Cl-2] (3) and [Cu(APMB)NO3(H2O)] (4) (where DKMBH = di-2-pyridyl ketone-4-methoxybenzhydrazone and APMBH = 2-acetylpyrazine-4-methoxybenzhydrazone) were prepared. The structural aspects of aroylhydrazones and metal complexes were examined using a combination of spectroscopic techniques, such as FT-IR, UV-Visible, mass, and H-1 NMR analysis, and further followed by analytical methods, such as CHN elemental analyses, thermal analyses, and molar conductivity studies. The molecular and crystal structures of aroylhydrazone, APMB and copper complex 4 were resolved using single-crystal X-ray diffraction (XRD) studies. The occurrence of the amido form of the aroylhydrazone in the solid state was confirmed by IR spectroscopy and single-crystal XRD studies. The crystal structure of the aroylhydrazone is stabilized through various non-covalent interactions including hydrogen bonding, C-H & ctdot;pi and pi & ctdot;pi interactions. The IR spectral studies further substantiated the tridentate nature of the aroylhydrazone ligands. Additionally, the copper(II) complexes demonstrated their potential as a promising catalyst for oxidation of cinnamyl alcohol using tert-butyl hydroperoxide (TBHP) as an oxidant. The copper(II) complex 1 exhibited better catalytic activity than the other complexes for cinnamyl alcohol conversion. A maximum cinnamyl alcohol conversion of 79% with 74% cinnamaldehyde selectivity was observed using copper(II) complex 1 in acetonitrile as solvent at 70 degrees C for 4 h using TBHP (70% water) as an oxidant.

Automated summary

The structural characteristics of a series of copper(II) complexes were investigated using spectroscopic and analytical methods. The crystal structures of aroylhydrazone, APMB and copper complex 4 were resolved using single-crystal X-ray diffraction studies. The copper(II) complexes showed promising catalytic activity in the oxidation of cinnamyl alcohol, with complex 1 exhibiting the highest activity.