Syntheses, structural and thermal studies of Eu(III) and Gd(III) complexes with 2,6-dinitrophenol and 1,10-phenanthroline/2,2′-bipyridine ligands

Some europium(III) and gadolinium(III) complexes viz., [Eu(phen)2Cl3CH3OH] (1), [Gd(phen)2(NO3)3] (6), [Ln(2,6-DNP)3(phen)CH3OH] (2, 7), [Ln(2,6-DNP)3(phen)(OH)]·Hphen (3, 8), [Ln(2,6-DNP)3(bipy)OH2] (4, 9), [Ln(2,6-DNP)3(bipy)(OH)].Hbipy (5, 10) (Ln = Eu, Gd; 2,6-DNP = 2,6-dinitrophenol; phen = 1,10-phenanthroline; bipy = 2,2′-bipyridine), have been synthesized and characterized by different physico-chemical methods including single crystal X-ray crystallography. Their thermal properties have been studied by thermogravimetric analysis (TG) and demonstrated that the final product after decomposition was stable oxide (Ln2O3) for all these complexes. Isothermal thermogravimetric study in the range of 410–450 °C for 1–5 and 270–310 °C for 6–10 has been done for all the complexes while the kinetics of thermal decomposition was evaluated by applying model fitting as well as an isoconversional methods. To investigate the response of these complexes under the condition of rapid heating, ignition delay (Di) has been measured. The possible pathways of thermolysis for these complexes have also been proposed.

Graphical abstractSome europium(III) and gadolinium(III) complexes viz., [Eu(phen)2Cl3CH3OH] (1), [Gd(phen)2(NO3)3] (6), [Ln(2,6-DNP)3(phen)CH3OH] (2, 7), [Ln(2,6-DNP)3(phen)(OH)]·Hphen (3, 8), [Ln(2,6-DNP)3(bipy)OH2] (4, 9), [Ln(2,6-DNP)3(bipy)(OH)].Hbipy (5, 10) (Ln = Eu, Gd; 2,6-DNP = 2,6-dinitrophenol; phen = 1,10-phenanthroline; bipy = 2,2′-bipyridine), have been synthesized and characterized by different physico-chemical methods including single crystal X-ray crystallography.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► First report on Eu(III) and Gd(III) complexes of 2,6-DNP and phen/bipy at various pH. ► At pH 6–7, coordination number of complex is nine but at pH 4–5, it reduces to eight. ► The complexes contain protonated phen/bipy molecule in lattice at lower pH. ► The mechanism of thermal decomposition changes as the reaction proceeds.