Synthesis and Thermal Characterization of Lanthanide(III) Complexes with Mercaptosuccinic Acid and Hydrazine as Ligands

Hindawi Publishing Corporation Journal of Chemistry Volume 2013, Article ID 497956, 10 pages http://dx.doi.org/10.1155/2013/497956 Research Article Synthesis and Thermal Characterization of Lanthanide(III) Complexes with Mercaptosuccinic Acid and Hydrazine as Ligands S. Devipriya,1 N. Arunadevi,2 and S. Vairam1 1 2 Department of Chemistry, Government College of Technology, Coimbatore 641013, India Department of Chemistry, SNS College of Technology, Coimbatore 641035, India Correspondence should be addressed to S. Vairam; Received 27 January 2012; Revised 11 July 2012; Accepted 12 July 2012 Academic Editor: Marc Visseaux Copyright © 2013 S. Devipriya et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Reaction of hydrazine and mercaptosuccinic acid with metal ions forms complexes with general formula [Ln(N2 H4 )2 {CH2 (COO)CH(SH)(COO)}1.5 ]⋅(H2 O), where Ln = La(III), Pr(III), Nd(III), Sm(III), and Gd(III) at pH 5. e complexes have been characterized by elemental analysis, IR and UV-visible spectroscopic, thermal and X-ray diffraction studies. e IR data reveal that the acid moiety in the complexes is present as dianion due to the deprotonation of COOH groups by lanthanides in these complexes, leaving –SH group unionized and hydrazine as bidental neutral ligand showing absorptions in the range of 945–948 cm−1 . e thermoanalytical data evince that the complexes are stable up to 103∘ C and undergo complete decomposition in the range of 550–594∘ C resulting in metal oxides. SEM images of La2 O3 and Gd2 O3 residues show their nano sized clusters suggesting that the complexes may be used as precursors for nano La2 O3 and Gd2 O3 , respectively. X-ray powder diffraction patterns show isomorphism among the complexes. e kinetic parameters of the decomposition of the complexes have been computed by Coats-Redfern equation. 1. Introduction Mercaptosuccinic acid, as a ligand, has been of interest because of its versatility in coordinate modes due to two carboxylic acid and sulydryl groups. It is known to form complexes with divalent transition metal ions, Mn(II), Fe(II), Co(II), and Ni(II). It is reported that, in these complexes, S–H is ionised and coordinated in addition to coordination of one of the COOH groups [1]. Patil and Krishnan have reported that alkaline earth metals Mg, Sr, and Ba also form 1 : 1 complexes in which S–H group is not involved and two COOH groups involve in coordination. ese complexes are found to form precipitates of metal mercaptosuccinates with aqueous solution of zinc and cadmium salts, leaving alkaline earth metal ions in solution and hence they can be used as antidote for Zn and Cd poisoning [2]. A potentiometric titration study indicates the formation of mercaptosuccinic acid complexes of Zn and Ni with and without the involvement of sulydryl group in coordination [3]. Another potentiometric study of chelates formed by La3+ , Ce3+ , Pr3+ , and Nd3+ with this acid reveals that the chelates of acids containing –SH group are less stable than those with NH2 or OH donor group [4]. A study on heterochelates of Zn2+ with nitrilotriacetic acid and mercapto acids system explains the stability of chelates due to two factors, Π interaction in M–S bond and sigma bonding of M–S bond due to polarisation of sulfur [5]. A similar type of study on heterochelates of Ni and Zn containing this acid and dipyridyl supports the above factors. However, it concludes that the greater stability of M–S bond may be due to strengthening of M–S sigma bond and the contribution of M–S Π interaction, its lower stability due to the presence of coligands. In spite of these reports, there is no systematic study of synthesis of mercaptosuccinic acid complexes with lanthanides found in the literature. We have been studying carboxylate complexes of lanthanides and transition metals using hydrazine as coligand. ere are numerous reports on metal hydrazine complexes of formic [6], acetic [7], propionic [8], glycolic [9], salicylic [10], tri- and tetracarboxylic [11, 12], and naphthoxy and hydroxy naphthoic 2 (a) (b) Transmittance (%) acid [13, 14] systems. In many complexes, hydrazine being a simple diamine acts as neutral monodentate, bidentatebridged, and monodentate N2 H5 + cation in many complexes [15, 16]. With the interest of understanding the nature of interaction of lanthanides with carboxylic acid containing S–H group and hydrazine together, we performed this work. We have reported the synthesis of new lanthanide complexes using mercaptosuccinic acid and hydrazine as ligands and their characterization by IR and UV-visible spectroscopic methods, simultaneous TG-DTA analysis, powder X-ray diffraction method, and magnetic measurements. Since these complexes were found to yield metal oxides of nanosize on decomposition, SEM image reports of residual oxides have also been presented. Journal of Chemistry (c) (d) (e) 2. Experimental 2.1. Preparation of [Ln(N2 H4 )2 {CH2 (COO)CH(SH) (COO)}1.5 ] ⋅ (H2 O), Where Ln = La(III), Pr(III), Nd(III), Sm(III), and Gd(III). ese complexes were prepared by adding a ligand solution which was obtained by mixing an aqueous solution of mercaptosuccinic acid (0.3 g, 2 mmol in 60 mL of H2 O) and hydrazine hydrate (0.2 g, 4 mmol) to a metal nitrate solution which was prepared by dissolving metal oxide (e.g., La2 O3 , 0.163 g, 0.5 mmol) in a minimum quantity of 1 : 1 conc. HNO3 and evaporated to eliminate excess of acid and dissolved in distilled water at pH 5. A crystalline product formed from the turbid solution while heating over water bath at 80∘ C for 1 h was �ltered, washed with absolute alcohol followed by ether, and dried in a desiccator over anhydrous CaCl2 . 2.2. Experimental Techniques. e composition was �xed by chemical analysis. Hydrazine content was determined by titrating against standard KIO3 (0.025 molL−1 ) [17]. Metal contents were determined by titrating with EDTA (0.01 molL−1 ) aer decomposing the complexes with 1 : 1 nitric acid [17]. IR Spectra of the complexes in the region 4000–400 cm−1 were recorded as KBr pellets using Perkin Elmer 597 spectrophotometer. Electronic re�ectance spectra of Pr(III), Nd(III), Sm(III), and Gd(III) complexes were obtained using a Varian Cary 5000 recording spectrophotometer. e magnetic susceptibility of Pr(III) and Nd(III) complexes was measured using a vibrating sample magnetometer, VSM EG & G model 155 at room temperature. e X-ray powder diffraction patterns of the complexes were recorded using Philips X-ray diffractometer (model PW 1050/70) employing Cu-K𝛼𝛼 radiation with nickel �lter. e simultaneous TGDTA experiments were carried out using SDT Q600 V8.3 instrument and Stanton 781 simultaneous thermal analyzer. ermal analyses were carried out in air at the heating rate of 10∘ C/min using 5 to 10 mg of the samples. P (...truncated)