Syntheses and thermal properties of some complexes with 2-mercaptonicotinic acid
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- 作者：Q. Yang ; S. Chen and S. Gao
- 关键词：enthalpy changes of reaction ; 2 ; mercaptonicotinic acid ; molar specific heat capacity ; thermal stability
- 刊名：Journal of Thermal Analysis and Calorimetry
- 出版年：2007
- 出版时间：December, 2007
- 年：2007
- 卷：90
- 期：3
- 页码：881-885
- 全文大小：110.2 KB
文摘
Five new complexes M(Hmna)2 [M=Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4) and Zn(II) (5), H2mna=2-mercaptonicotinic acid] have been synthesized and characterized by elemental analyses, IR spectra, thermogravimetric analyses. In addition, molar specific heat capacities and enthalpy changes of reactions were determined by a microcalorimeter at 298.15 K. All the complexes exhibited similar IR spectra, the sulfur and oxygen atoms from monoanionic Hmna− ligand coordinated to M2+ in a bidentate fashion. The thermal stability of M(Hmna)2 complexes varied in the sequence 1>2>3>4>5. The complexes were stable up to about 300¡ãC and decomposed to oxides at higher temperatures. The molar specific heat capacities of the complexes were determined in the range between 106.452¡À0.399 and 145.920¡À0.423 J mol−1 K−1. The enthalpy changes of reactions, Δr H mθ, were determined from 18.28¡À0.05 to 52.59¡À0.07 kJ mol−1 for complexes 1–5, indicating that the thermodynamic stability of M(Hmna)2 increased in the sequence from Mn2+ to Zn2+.