L Journal of Alloys and Compounds 344 (2002) 105–109 www.elsevier.com / locate / jallcom Study of the thermal decomposition of the Nd(III), Eu(III) and Tb(III) scorpionates a,b, a,c c b * ´ ´ Pedro Miranda Jr. , Eliana M. Arico , Marcelo F. Maduar , Jivaldo R. Matos , d Carlos Alberto A. de Carvalho a ˜ Faculdades Oswaldo Cruz –FOC, Sao Paulo ( SP), Brazil b ˜ ´ Instituto de Quımica, USP , Sao Paulo ( SP), Brazil c ˜ ´ Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo ( SP), Brazil d ´ Departamento de Quımica, UFOP , Ouro Preto ( MG), Brazil Abstract 3 The thermal behavior of the compounds [k HB(N C H ) ] Ln (Ln5Nd, Eu and Tb) was investigated through TG/DTG and DSC 2 3 3 3 3 21 analyses. TG / DTG experiments were performed in a TGA-50 Shimadzu instrument under dynamic air atmosphere (50 ml min ). DSC 21 21 measurements were performed in a dynamic nitrogen atmosphere (50 ml min ) at 10 8C min heating rate using a DSC-50 Shimadzu differential calorimeter. For the TG / DTG and DSC analyses, an amount of 1.5–2.0 mg was used. From the TG curves, it was possible to show that all compounds are anhydrous, a one-step mass loss occurring between 200 and 450 8C, yielding a residual stable up to 900 8C. From the DTG curves it was found that decomposition temperatures decrease as the Ln(III) ionic radius decreases. DSC curves indicate that the compounds do not melt before the decomposition. For all three compounds, the decomposition process is exothermic.  2002 Elsevier Science B.V. All rights reserved. Keywords: Lanthanides; Scorpionates; Thermal decomposition 1. Introduction scopic compounds, the investigation of their thermal behavior was undertaken in order to understand and The poly(pyrazolyl)-borates (Tp*), also known as scor- correlate it with the structure of the compounds along the pionates, formula HB(N C H ) , are chelating monovalent lanthanide series. 2 3 3 3 anions, containing nitrogen as donor atoms. Such com- pounds have lately found numerous applications in inor- ganic, organometallic and bioinorganic chemistry [1,2]. The Tp* ligand behaves as a six-electron donor and, with regard to rare earth ions, they fulfil the electronic and steric requirements of the central ion, saturating its coordination sphere and therefore providing anhydrous stable com- 3 pounds, [k HB(N C H ) ] Ln, even when prepared from 2 3 3 3 3 aqueous solution, with unusual chemical environments and molecular structures [3]. A formula drawing of a Ln(Tp*) 3 compound is shown in Fig. 1. As the Ln(Tp*) are very unusual water-free non-hygro- 3 *Corresponding author. Tel. / fax: 155-11-3091-3876. E-mail address: pmjunior@iq.usp.br (P. Miranda Jr.). Fig. 1. Formula drawing of Ln(Tp*) . 3 0925-8388 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388(02)00318-3