Syntheses, structural and thermal analysis of Tb(III) complexes with 4-nitrophenol, 2,6-dinitrophenol and 1,10-phenanthroline ligands

• Synthesis of two new Tb(III) complexes with PNP, 2,6-DNP and phen.
• Detailed study of crystal structures and their 3D packing.
• Thermal studies showed their multi-step decomposition.
• End products of thermal decomposition are Tb2O3 that is confirmed by PXRD.
• Ignition delay and activation energies are found in the order 2 > 1.

Two terbium (III) complexes namely {[Tb(PNP)3(phen)2OH2]·CH3OH} (1), {[Tb(2,6-DNP)3phenOH2]·phen} (2) (PNP = 4-nitrophenol, 2,6-DNP = 2,6-dinitrophenol and phen = 1,10-phenanthroline) have been synthesized and characterized by different physico-chemical methods including single crystal X-ray crystallography. The X-ray studies reveal that the complex 1 crystallizes in monoclinic space group P21/n with the cell dimensions a = 10.9302(18) Å, b = 18.496(3) Å, c = 20.913(3) Å, whereas the complex 2 crystallizes in the triclinic space group P1 with the cell dimension a = 12.0734(7) Å, b = 13.0447(7) Å, c = 14.6824(8) Å. Crystal structures also show that both complexes have eight coordination number and distorted square-antiprism geometry around the metal center. Thermal analysis is carried out by using TG, DSC, which signifies that the final product after decomposition is stable oxide (Tb2O3), which has been confirmed by their PXRD patterns. The kinetics of thermal decomposition has been evaluated by applying model fitting as well as an isothermal–isoconversional methods. In order to see the response of rapid heating, ignition delay measurements (Di) are carried out. On the basis of thermal studies, the ignition delay (Di) and activation energies (Ea∗) of these complexes are found in the order 2 > 1.

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