Introduction Antipyrine (2,3-dimethyl-1-phenyl-3-pyrazolin-5- one) and its derivatives possess a wide variety of po- tentially useful application, including biological [1, 2], clinical [3] and pharmacological areas [4]. They are also used as antipyretic, analgesic and anti-rheumatic materials [5–8]. Antipyrines have also been used as analytical reagents in determination of some metal ions [9]. Follow up literature indicate that considerable study has been devoted to Schiff bases and azo containing ligands derived from either 4-amino- or 4-formylantipyrine [10–12]. However, all the reported studies on this type of compounds are concerning with synthesis, structure and properties. However, comparatively less is known regarding their thermal behaviour. The present study extends to synthesis, characterization and thermal behaviour studies of UO 2 (VI), Sn(IV), Th(IV) and Li(I) com- plexes with 4-azomalononitrile antipyrine (L). Experimental Reagent grade chemicals were used without further purification. The ligand 4-azomalononitrile anti- pyrine (Scheme 1) was prepared and characterized as described [13]. The metal complexes were prepared by stirring magnetically at ca. 60°C an ethanolic solution (0.002 mol) of a metal salt of UO 2 (VI) chloride, nitrate, ace- tate, Sn(IV) diphenyl chloride, Sn(IV) chloride, Th(IV) nitrate or Li(I) chlorate (VII) with (0.002 or 0.004 mol) 4-azomalononitrile antipyrine (L) in ca. 50 mL EtOH for periods of 5 h or more. The re- sulting solids were filtered off, washed several times with EtOH and dried under vacuum over P 4 O 10 . Ele- mental analysis (C, H and Cl) were performed by the Microanalytical unit of the University of Cairo, Egypt. Metal analyses were estimated using standard methods. IR spectra in the 4000–200 cm –1 range were performed as KBr discs using a PerkinElmer 1430 re- cording spectrophotometer. 1 H NMR spectra were re- corded in DMSO-d 6 using a 300 MHz Varian NMR spectrometer. The molar conductivity measurements were made in DMF solutions (10 –3 M) using a Tacussel conductometer type CD6N. Thermal analyses (DTA/TG) were carried out under N 2 atmo- sphere using a Schimadzu DT-50 thermal analyzer at a heating rate of 10°C min –1 in the temperature range 25–800°C using platinum crucibles. 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2008 Akadémiai Kiadó, Budapest UO 2 (VI), Sn(IV), Th(IV) AND Li(I) COMPLEXES OF 4-AZOMALONO- NITRILE ANTIPYRINE Synthesis, characterization and thermal studies H. A. El-Boraey 1* , F. A. El-Saied 1 and S. A. Aly 2 1 Department of Chemistry, Faculty of Science, El-Menoufia University, Shebin El-Kom, Egypt 2 Department of Chemistry, Genetic Engineering and Biotechnology Research Institute, El-Menoufia University, Sadat City, Egypt UO 2 (VI), Sn(IV), Th(IV) and Li(I) complexes of 4-azomalononitrile antipyrine (L) have been isolated and characterized based on IR spectra, 1 H NMR, elemental analyses, molar conductance and thermal analysis (DTA/TG). The study revealed that the ligand be- haves as a neutral bidentate one and coordination takes place via the carbonyl atom of pyrazolone ring >C=O and the azomethine ni- trogen >C=N. The thermal stability of the metal complexes were investigated by thermogravimetry (TG), differential thermal anal- ysis (DTA) techniques and infrared spectra, and correlated to their structure. The thermal study revealed that Th(IV) complexes show lower thermal stability than both UO 2 (VI) and Sn(IV) complexes. Keywords: complexes, conductivity, IR, synthesis, thermal analysis (DTA/TG) Scheme 1 * Author for correspondence: helboraey@yahoo.com Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 96 (2009) 2, 599–606