Novel Fe (III) heterochelates: Synthesis, structural features and fluorescence studies

Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H2SBn) and their Fe (III) heterochelates of the type [Fe(SBn)(L)(H2O)]·mH2O [H2SBn = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = -CH3, m = 4 (H2SB1); -C6H5, m = 2 (H2SB2); -CH2-CH3, m = 3 (H2SB3); -CH2-CH2-CH3, m = 1.5 (H2SB4); -CH2-C6H5, m = 1.5 (H2SB5) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (Ea), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported.