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Schiff bases of 1,5-diarylpent-4-ene-1,3-diones and their metal complexes: Synthesis, characterization and fluorescent studies

Four Schiff bases (H 2 L 1 to H 2 L 4 ) have been synthesized by the con­densation between o -aminophenol and unsaturated diketones (1,5-diarylpent-4--ene-1,3-diones). Analytical, IR, 1H NMR and mass spectral data revealed their existence in the imine-enamine form. Dibasic tetradentate coordination of the Schiff bases in their ML complexes [M = Cu(II), Ni(II), Co(II), Zn(II), Cd(II), and Hg(II)] has been established on the basis of physical, analytical and spectral data. The fluorescent studies of H 2 L 4 show that fluorescence emission maxima shift with increase in polarity and hydrogen bonding ability of the solvent. Paramagnetic Cu(II), Ni(II) and Co(II) ions decrease the fluorescence intensity with increase in concentration of the metal ion while diamagnetic Zn(II), Cd(II) and Hg(II) ions have very little influence on the intensity of fluorescence of the Schiff base H 2 L 4 .