Synthesis and characterization of Fe(II) and Ni(II) complexes with Quercetin / Muhammad Azrin Md Yusof

Quercetin which is one of the flavonoid derivatives has several health-promoting effects on humans, including antioxidant, anticancer, antiviral, antibacterial, neuroprotective, and cardioprotective activities. The biological and pharmacological actions of metal-chelated quercetin are much greater than those of quercetin ligand. Recently, it was shown that flavonoids such as quercetin form high-affinity compounds with transition metal ions such as iron and nickel. This technique is regarded as the primary means of enhancing their efficiency in biological tasks such as radical scavenging. In this study, Fe(II) and Ni(II) complexes with quercetin ligand were synthesized in a ratio of quercetin 2:1 metal and characterized using spectroscopic methods such as UV-Vis and FTIR. Fe(II)-quercetin complex was formed with a dark black colour, whereas Ni(II)-quercetin complex was dark brown. According to UV-Vis spectral data, the band I (cinnamoyl system) of both Fe(II)-quercetin and Ni(II)- quercetin complexes had undergone a bathochromic shift, shifting towards longer wavelengths (lower energy). For FTIR spectroscopy, the v(C=O), v(C=C), v(C-OH), and v(O-H) frequencies in Fe(II)-quercetin and Ni(II)-quercetin complexes were shifted somewhat lower from their original value, but v(C-O-C) shifted slightly higher. Additional spectrum data for Fe(II)-quercetin and Ni(II)-quercetin were discovered at 519 cm−1 and 473 cm−1, respectively, representing the v(M-O) absorbance. Both spectroscopic studies demonstrated the complexation of metal with quercetin through an oxygen atom of hydroxyl and carbonyl groups.