Available online at www.bjta.iiatbr.org Braz. J. Therm. Anal. Vol. 4 No. 4 (2015) 41 – 46 DOI: 10.18362/bjta.v4.i4.232 * Corresponding author: Tel.: +55-16-3301-9617 E-mail address: nascimento.a.l.c@gmail.com (A. L. C. S do Nascimento) © 2015 Published by IIAT – Instituto Internacional de Análise Térmica Thermal behavior of nicotinate of some bivalent transition metal ions in dry CO 2 and N 2 atmospheres do Nascimento A. L. C. S 1* , Caires F. J., Colman T. A. D., Ionashiro M. 1 Instituto de Química, Universidade Estadual Paulista, CP 355, 14801-970 Araraquara, SP, Brazil Received data: 10/07/2015; accepted data: 11/11/2015 Available online: 31/12/2015 Abstract Synthesis, characterization and thermal decomposition of bivalent transition metal nicotinates M(C 6 H 4 NO 2 ) 2 . nH 2 O (M = Mn (II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)), as well as the thermal decomposition of sodium nicotinate, were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), simultaneous thermogravimetry and differential scanning calorimetry (TG- DSC) coupled to infrared spectroscopy (FTIR) and complexometry. In both atmospheres, the thermal decomposition of sodium nicotinate up to 500 ºC, occurs with the formation of sodium carbonate and carbonaceous residue and up to 800 ºC the mass loss is still being observed. In CO 2 atmosphere the thermal decomposition of these compounds occurs in three consecutive steps, with the formation of the respective metal or metal oxides: MnO, FeO, CoO, Ni°, Cu° and ZnO. In N 2 atmosphere, the thermal decomposition also occurs, in three consecutive steps and only iron and cobalt compounds, with the formation of Fe 3 O 4 and CoO, respectively, while the other compounds the mass loss is still being observed up to 1000 ºC. Keywords: transition metals, nicotinate, thermal behaviour 1. Introduction Nicotinic, 3-picoline or pyridine-3-carboxylic acid (Fig 1) is the biological precursor of the co-enzymes: nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). Figure 1. Structural formula of nicotinic acid. The literature shows that the papers involving nicotinic acid and bivalent manganese, cobalt, nickel, copper and zinc reported the spectroscopic, thermogravimetric, magnetic studies and thermochemical behavior of solid nicotinic hydrazide [1,2], thermal decomposition of copper (II) nicotinate, isonicotinate and synthesis and characterization of copper (II) complexes with nicotinate in different coordination style [3,4], a new 2-D chiral coordination polymer of [Zn(nicotinate)2] n [5], simultaneous thermal analysis of a cobalt (II) complex with nicotinate [6], hydrothermal synthesis, crystal structures and properties of two 3-D network nickel nicotinate coordination polymers and hydrothermal synthesis, structural determination and thermal properties of 2-D cobalt-and nickel-based coordination polymers incorporating pendant-arm 3- pyridinecarboxylate ligands [7,8], synthesis, structures and properties of 3d/5d-4f metal complexes with novel polycationic chains [9], a pionner study on the anti-ulcer activies of copper nicotinate complex [CuCl(HNA) 2 ] in experimental gastric ulcer induced by aspirin-pyloris ligation model (shay model) [10], Growth and characterization of a novel polymer of manganese (II) nicotinate single crystal [11] and thermal behavior of nicotinic acid, sodium nicotinate and its compounds with some bivalent transition metal ions [12]. In this paper, solid-state compounds of some bivalent transition metal ions (i.e. Mn, Fe, Co, Ni, Cu and Zn) with nicotinate were prepared. These compounds were investigated by means of complexometric, simultaneous thermogravimetry and differential thermal analysis (TG-DTA) in CO 2 and N 2 atmospheres and simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) coupled to infrared spectroscopy (FTIR), since the use of the coupled techniques makes possible a correct interpretation for the mechanism of a thermally induced reaction, involving the formation of gaseous species evolved during the thermal decomposition [13]. This work is primarily a continuation and extension of a previously reported study [12]. 2. Experimental The nicotinic acid (C 6 H 4 NO 2 ) with 99.5% purity was obtained from Sigma and it was used as received. Aqueous solution of sodium nicotinate 0.1 mol L -1 was prepared by neutralization of an aqueous solution of nicotinic acid with sodium hydroxide solution 0.1 mol L -1 . Aqueous solutions of bivalent metal ions 0.1 mol L -1 were prepared by dissolving