Synthesis, spectroscopic characterization and biological activities of complexes of light lanthanide ions with...

New solid compounds of light lanthanide ions with 3-hydroxyflavone were synthesized in good yields (up to 85 %). The resulting complexes have been thoroughly characterized using various analytical and spectral techniques, including elemental analysis, complexometry, thermogravimetry, UV-VIS, FT-IR, ¹H NMR, ¹⁰⁹AgNPET LDI MS and fluorescence spectroscopy. The molecular formulas of the complexes were determined as follows: Ln(3HF)₃, where 3HF-3-hydroxyflavone, Ln = La(III), Pr(III), Nd(III) and Ln(3HF)₃·nH₂O, where n = 1 for Ln = Ce(III), Sm(III), Eu(III), and n = 2 for Gd(III). Thermogravimetric studies revealed that the water molecules in the hydrated compounds are located in the outer coordination sphere. Based on the spectral data, it was noted that lanthanide ions interacted with the 3OH and 4CO groups of 3-hydroxyflavone. The effect of lanthanide ion chelation on the excited-state intramolecular proton transfer (ESIPT) process and fluorescence emission of 3HF was investigated. It was found that coordination with metal ions can suppress the ESIPT process and enhance the fluorescence emission of 3HF. The synthesized compounds were also screened for their antibacterial activity, free radical scavenging capacity, and interaction with BSA. The results showed that the complexes exhibit higher biological activity compared to the ligand.