Effect of temperature on formation of two new lanthanide metal-organic frameworks: Synthesis, characterization and theoretical studies of Tm(III)-succinate Carlos Alberto F. de Oliveira a , Fausthon Fred da Silva a , Ivani Malvestiti a , Vale ´ ria Rodrigues dos S. Malta b , Jose ´ Diogo L. Dutra c , Nivan B. da Costa Jr. c , Ricardo O. Freire c , Severino A. Ju ´ nior a,n a Department of Fundamental Chemistry, UFPE, 50590-470 Recife, PE, Brazil b Institute of Chemistry and Biotechnology, UFAL, 57062-970 Maceio ´, AL, Brazil c Department of Chemistry, UFS, 49100-000 S ~ ao Cristo ´v ~ ao, SE, Brazil article info Article history: Received 9 May 2012 Received in revised form 7 August 2012 Accepted 12 August 2012 Available online 29 August 2012 Keywords: Metal-organic frameworks Succinates Hydrothermal synthesis Thulium Sparkle abstract Two new metal-organic frameworks (MOFs) have been synthesized under different hydrothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravi- metric analysis, scanning electron microscopy and elemental analysis. Compound 1, crystallized in space group P1 ¯ with the formula [Tm 2 (L) 3 (H 2 O) 2 ]  H 2 O, (H 2 L ¼succinic acid), has triclinic cell parameters of a ¼7.61780(10), b ¼10.58050(10), c ¼12.71030(10), a ¼95.3130(10), b ¼107.4370(10), g ¼111.0960(10) and a cell volume of 888.446(16) ˚ A 3 . Compound 2, crystallized in space group I2/a with the same formula, is monoclinic, with cell parameters of a ¼13.77020(10), b ¼7.63170(10), c ¼17.2410(2), b ¼101.303(10) and a cell volume of 1776.72(3) ˚ A 3 . The results of this work indicate that a flexible succinate ligand that provides several modes of coordination can lead to different conformations, depending on the temperature used in the reaction. In the theoretical part of this study, semiempirical quantum chemistry methods using AM1, PM3 and PM6 models are employed to predict the structure of MOFs, calculate the geometric and crystallographic parameters, and make comparisons with experimental data. & 2012 Elsevier Inc. All rights reserved. 1. Introduction Metal-organic frameworks (MOFs) are a promising class of porous materials with strategic applications in fields such as catalysis [1,2], gas adsorption [3], luminescent materials [4], non-linear optics [5,6] and others. These applications depend on the material’s structure. Therefore, control of the synthesis para- meters and ligand structures is considered important in the formation of new structures [7]. It is well known that the conditions of synthesis are crucial to obtain certain compounds. The most important factors susceptible to change in the rational design of metal-organic frameworks are the pH value, solvent type, and reaction time and temperature [8]. Varying the reaction temperature and time enables one to determine the existence of a thermodynamic or kinetic control of the formation of a specific phase. In this context, flexible ligands have been recognized for the different conformations they can assume in the formation of compounds [9]. In recent years, several researchers have used the hydrother- mal route to prepare a variety of lanthanide ion compounds based on succinate ligands, such as Ln ¼ Er [10], Ce and Sm [11], Gd [4], Eu and Tb [12], Ho [7], Pr [13], Yb [1], and others [14]. Succinate ligands are particularly important because of their flexibility and various modes of coordination that usually favor the formation of 3D coordination networks. To the best of our knowledge, metal- organic frameworks with thulium ion and succinate ligands have so far not been investigated. Narda et al. [7] reported that the reaction of lanthanide ions with succinate anions forms compounds that can be separated into groups according to the presence or absence of molecules of water of hydration and that, under hydrothermal conditions, the reaction of holmium ion with succinate ligand forms compounds that crystallize into monoclinic or triclinic systems. In theoretical chemistry, the ability to predict geometries of thulium complexes is fundamental in the design of luminescent complexes, for which theoretical models such as Sparkle [15], as well as other lanthanides [16], have been used successfully. In this paper, we describe the synthesis, crystal structures, theoretical studies and characterization of two different hybrid 3D frameworks based on thulium(III) ion and succinate ligand Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jssc Journal of Solid State Chemistry 0022-4596/$ - see front matter & 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jssc.2012.08.036 n Corresponding author. E-mail address: salvesjr@ufpe.br (S.A. Ju ´ nior). Journal of Solid State Chemistry 197 (2013) 7–13