Low temperature heat capacity study of Zn, Cd and Mn based coordination compounds synthesized using phenanthroline and halogenated benzoic acid

• Published in: Thermochimica acta 2018-12, Vol.670, p.76-86
• Main Authors: Li, Rongchun, Zheng, Hui, Hua, Yushan, Wei, Rongmin, Tan, Zhicheng, Shi, Quan
• Format: Article
• Language: English
• Subjects: Coordination compounds; Crystal structure; Heat capacity; PPMS; Thermodynamic function
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2018.10.012

•We have synthesized four Zn, Cd and Mn based coordination compounds.•Molecular structures have been well characterized.•Heat capacities have been measured in the temperature region of (1.9–300) K.•The corresponding thermodynamic functions have been obtained.•The heat capacity contributions have been extracted by fitting the data to theoretical models below 10 K. Four Zn, Cd and Mn based 1,10-phenanthroline and halogenated benzoic acid coordination compounds, formulated as Zn2II(H2O)3(phen)(SO4)·H2O (1, phen = 1,10-phenanthroline), ZnII(phen)(L2)2(H2O) (2, L2 = 2-chloro-4-fluorobenzoic acid), MnIV(phen)(L1)4 (3, L1 = 2-Chloro-4,5-difluorobenzoic acid) and CdII(phen)2(NO3)2 (4), were successfully synthesized and structurally characterized. The low temperature heat capacities of these four compounds were further investigated using a Physical Property Measurement System calorimetric method. The experimental heat capacities were fitted to a series of theoretical and empirical heat capacity models, and the corresponding thermodynamic functions were calculated in the temperature range from (0 to 300) K based on these models and fitting parameters. The low temperature fits indicated that compound 1 can be modeled using only lattice heat capacity contribution, compound 3 modeled using lattice and A-2 term or Schottky heat capacity contributions, and compound 2 and 4 modeled using contributions from lattice, vacancies and one-dimensional phonons with a finite energy onset or gap.