A Fluorescence Study of Pyrazole Derivative 2-(1,5-diphenyl-4,5-dihydro-1H-pyrazole-3-yl)pyridine Upon Addition of La3+ and Eu3+ Ions

Abstract

Synthesis of pyrazole derivative ligand 2-(1,5-diphenyl-4,5-dihydro-1H-pyrazole-3-yl) pyridine (L) has been successfully carried out by the Claisen-Schmidt condensation followed by the excess addition of phenyl hydrazine in ethanol solution. Reddish yellow solid with a 28.85% yield then characterized using FTIR , UV-Visible, and H1-NMR spectroscopy. UV-Visible spectroscopy was conducted to determine the complex formation between lanthanide ions with ligands. Fluorescent experiment with spectrofluorometer has conducted in compound emission intensity change upon addition of La3+ and the Eu3+. UV-Visible result show complex formation in molar ratio Eu3+ : L (1:2) which occurred at a absorption wavelength of 366 nm, while the complex with the ratio La3+ : L (1:3) exhibited at 342 nm in acetonitrile. Fluorescence analysis showed ligands have two excitation λ at 257 nm 365 nm with a noticeable molar absorptivity at concentration 2x10-5 M. The addition of La3+ ions lead to the fluorescence enhancement effect on the λem at 355 nm. While the addition of the Eu3+ demonstrates the effect of fluorescence quenching at the λem 340 nm.