Preparation, Crystal Structure And Thermal Decomposition Kinetics Of Samarium Benzoic Acid And Its Derivatives Complexes With 1, 10-Phenanthroline

Nineteen ternary complexes of Sm(III) have been synthesized, in which benzoic acid and its derivatives were as the first ligand, and 1,10-phenanthroline as the second ligand. They are [Sm(BA)₃phen]₂ , [Sm(o-MBA)₃phen]₂, [Sm(m-MBA)₃phen]₂ , [Sm(p-MBA)₃phen]₂ , [Sm(o-MOBA)₃phen]₂·2H_<sub>2O , [Sm(m-MOBA)₃phen]₂, [Sm(p-MOBA)₃phen]₂ , [Sm(o-ClBA)₃phen]₂ , [Sm(m-ClBA)₃phen]₂?2H₂O, [Sm(p-ClBA)₃phen]₂?2H₂O, [Sm(o-BrBA)₃phen]₂, [Sm(m-BrBA)₃phen]₂?2H₂O, [Sm(p-BrBA)₃phen]₂?2H₂O , [Sm(o-NBA)₃phen]₂, [Sm(m-NBA)₃phen]₂?2H₂O,[SmO-NBA)₃phen]₂?2H₂O,[Sm(o-ABA)₃phen]₂?2H₂O, [Sm(m-ABA)₃phen]₂?2H₂(X [Sm(p-ABA)₃phen]₂?6H₂O. They were characterized by elemental analysis, IR and UV spectroscopy, thermal analysis and X-ray diffractometer.The structures of four ternary complexes of [Sm(BA)₃phen]₂ , [Sm(o-MBA)₃phen]₂, [Sm(o-MBA)₃phen?H₂O]₂?4H₂O and [Srn(o-ClBA)₃phen]₂ have been determined using crystal X-ray diffraction. They all exist as binuclear molecules, and their crystal are triclinic, space group P I With a=10.8216(11) A, b=11.9129(13)A, c=12.425(2)A, α=105.007(2)°, β=93.652(2)°, γ=113.2630(10)°;a=13.1364(10)A , b=14.3739(11)A , c=17.4356(13)A , α=83.1100(10) ,° β=83.7760(10)° , γ=73.0520(10)°;a=12.0312(10)A , b=12.9302(10)A , c=13.0581(11)A, α=64.5020(10)°, β=81.9320(10)°, γ=74.8140(10)°;a=13.157(3)A, b=14.139(4)A, c=17.397(4)A, α=83.755(3)°, β=84.064(3)°, γ=73A34(3)° The coordination number is 9. The carboxylate groups are bonded to the samarium ion in four modes: (1) mondentate (2) bidentate chelating, (3) bidentate bridging, (4) tridentate chelating-bridging. However, the complexes of [Sm(o-MBA)₃phen]₂ and [Sm(o-ClBA)₃phen]₂ consist of two different types of binuclear molecule. This is possibly because of the electronic and steric effects aroused by the position of the substitutional group substituent on the benzene ring.The thermal decomposition processes of the complexes were determined using TG-DTG, DSC, IR techniques. The non-isothermal kinetics of the complexes wereinvestigated using a new method of processing the data of thermal analysis kinetics, i e. double equal-double step method. The most probable mechanism functions, activation energy E and pre-exponential factor A of the first thermal decomposition stage for complexes [Sm(/7-MBA)3phen]2 n [Sm(p>-MOBA)3phen]2 > [Sm(o-NBA)3phen]2 and of the second stage forcomplexes[Sm(/7z-ClBA)3phen]2-2H2CK [Sm(/w-BrBA)3phen]2-2H2O were obtained from analysis of the TG-DTG curves, and the Gibbs free energy of activationZ\G^, the enthalpy of activation A H", the entropy of activation A S" were also calculated. The dehydration processes and kinetics of the complexes [Sm(w-ClBA)3phen]2-2H2O > [Sm(p-ClBA)3phen]2-2H2O and[Sm(/M-BrBA)3phen]2-2H2O have been studied from analysis of the DSC curves, and the thermodynamic parameters( AH', AG" and AS") were calculated. Meanwhile, the complexes without crystal waters of the lifetime equation at weight-loss of 10% were obtained. The thermal ability of a series of complexes was compared. The results will provide some valuable materials for the choice of the functional materials of rare-earth complexes.