Synthesis, crystal structure and thermodynamic properties of a new praseodymium Schiff-base complex

• Published in: Thermochimica acta 2014-04, Vol.581, p.118-122
• Main Authors: Li, Chuan-Hua, Song, Xiang-Zhi, Jiang, Jian-Hong, Gu, Hui-Wen, Tao, Li-Ming, Yang, Ping, Li, Xu, Xiao, Sheng-Xiong, Yao, Fei-Hong, Liu, Wen-Qi, Xie, Jin-Qi, Peng, Meng-Na, Pan, Lan, Wu, Xi-Bin, Jiang, Chao, Wang, Song, Xu, Man-Fen, Li, Qiang-Guo
• Format: Article
• Language: English
• Subjects: Austenitic stainless steels; Calorimetry; Constants; Dissolution–reaction calorimeter; Enthalpy; Ethyl alcohol; Hess's law; Ligands; Polyhedrons; Standard molar enthalpy of formation; Thermochemical cycle; Valen Schiff-base
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2014.02.021

•A new mononuclear Schiff base praseodymium complex was synthesized.•Based on Hess's law, thermochemical cycles of two reactions were designed.•The dissolution enthalpies were measured by a solution–reaction calorimeter.•The standard molar enthalpy of formation of the complex was calculated. The title complex [Pr(H2vanen)(NO3)2(H2O)2·NO3] was synthesized reacting of Valen Schiff-base ligand [H2vanen=N,N′-ethylene-bis(3-methoxysalicylideneimine)] and Pr(NO3)3·6H2O in ethanol at 60°C. The complex was crystallized in the monoclinic crystal system with space group P21/c. The coordination polyhedron of Pr(III) ion was consisted of two bidentate nitrate ions, two molecules of water and one ligand which coordinated through oxygen atoms of the two phenolic and methoxy groups. After designing two reasonable thermochemical cycles according to Hess's law, the calorimetric experiments were conducted using isoperibol solution–reaction calorimeter at a constant temperature of 298.15K. The standard molar enthalpy changes of two reactions were determined to be ΔrHmθ(1a)=−(51.94±1.26) kJmol−1 and ΔrHmθ(1b)=−(8.62±1.34) kJmol−1. Then the standard molar enthalpies of formation of the ligand and the title complex were calculated to be ΔfHmθ [H2vanen(s), 298.15K]=−(517.75±2.36) kJmol−1 and ΔfHmθ [Pr(H2vanen)(NO3)2(H2O)2·NO3 (s), 298.15K]=−(2454.8±2.7) kJmol−1, respectively. The rationality of two thermochemical cycles was verified by UV spectra and refractive indexes.