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Abstract  

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°C and decomposed to oxides at higher temperatures. The molar specific heat capacities of the complexes were determined in the range between 106.452±0.399 and 145.920±0.423 J mol−1 K−1. The enthalpy changes of reactions, Δr H m θ, were determined from 18.28±0.05 to 52.59±0.07 kJ mol−1 for complexes 1–5, indicating that the thermodynamic stability of M(Hmna)2 increased in the sequence from Mn2+ to Zn2+.

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times at 25 °C and the values are −1425.8, −1420.9, −1421.0, −1427.2, −1421.9 and −1418.4 mJ, respectively. The enthalpy change of reaction, , was calculated as −23.71 ± 0.023 kJ mol −1 . The value of is negative, indicating that it is favorable to the

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one. Sufficient amount of information about enthalpy changes of reactions in water was accumulated for complex formation between transition metals ions and amino acids anions and glycine-ion [ 1 – 3 ] and for complex formation of glycine and

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longer specified to zero. In fact, according to the first law of thermodynamics at constant pressure. 25 where Q is the heat effect and Δ H , the enthalpy change of reaction. By adding z T Δ S ∗( H + / H 2 ) to both sides of Eq. 25 and noting that

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formation of the complex Zn(Met)(NO 3 ) 2 ·1/2H 2 O(s) is given in Table 5 . The enthalpy change of reaction ( 5 ) obtained from experimental values of the dissolution enthalpies of {ZnSO 4 ·7H 2 O(s) + 2NaNO 3 (s) + l -Met(s)} and {Zn(Met)(NO 3 ) 2 ·1/2H

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The standard molar enthalpies of combustion of (C 9 H 6 O 4 Na 2 ·H 2 O, s) and (C 8 H 4 O 4 Na 2 ·1/2H 2 O, s) refer to the enthalpy changes of reaction ( 6 ) and ( 7 ) at 298.15 K and 100 kPa. 6 7 The standard molar enthalpies of

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