A new solvated complex of the uranyl ion (UO 2 2+ ) with 8-hydroxyquinoline Masoud Mirzaei a,⇑ , Azam Hassanpoor a , Antonio Bauzá b , Joel T. Mague c , Antonio Frontera b,⇑ a Department of Chemistry, Ferdowsi University of Mashhad, 917751436 Mashhad, Islamic Republic of Iran b Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma de Mallorca (Baleares), Spain c Department of Chemistry, Tulane University, New Orleans, LA 70118, USA article info Article history: Received 28 July 2014 Received in revised form 28 October 2014 Accepted 30 October 2014 Available online 10 December 2014 Keywords: Uranyl complex 8-Hydroxyquinoline Noncovalent interactions DFT calculations X-ray crystallography abstract A new solvated complex of the uranyl ion, [UO 2 (quin) 2 (H’quin)]ÁDMF (1), (Hquin = 8-hydroxyquinoline and H’quin = quinolinium-8-olate, i.e. the zwitterionic form of Hquin) was synthesized and investigated by means of elemental analysis, IR spectroscopy and X-ray crystallography. Interestingly one coordinated 8-hydroxyquinoline is protonated, thus provoking the simultaneous existence of an electron rich and electron poor ring in the same molecule. This clearly enhances the ability of this ring to form antiparallel stacking interactions that are responsible for the solid state architecture of compound 1. This aspect has been analyzed by means of density functional theory calculations (DFT), molecular electrostatic potential (MEP) tool and Bader’s theory of ‘‘atoms in molecules’’. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction The coordination chemistry of actinide ions is very important for the development of new extractants for the separation and purification of actinide ions from irradiated nuclear fuel and also for the technology concerning the storage of highly radioactive waste materials [1,2]. Uranium is the second most common naturally occurring actinide after thorium, however the former has more applications than the latter [3]. Uranium is most commonly used as nuclear fuel in fission reactors for civilian pur- poses. It has a strong preference for binding two axial O atoms to form the linear uranyl species UO 2 2+ in its +6 oxidation state. The uranyl ion exhibits good stability and forms complexes with vari- ous O-, N- and S-donor ligands. 8-Hydroxyquinoline (Hquin), which typically behaves as a bidentate (N, O) ligand, has a great ability to form luminescent coordination compounds either for light-emit- ting devices [4] or sensors [5]. Since 8-hydroxyquinoline and its anion have been used to construct LEDs and sensors, it appeared interesting to analyze its coordination ability with an actinide ele- ment such as uranium, since it might show interesting structural arrangements and properties. As a continuation of our previous research [6–8], we report the synthesis of a new solvated complex of the uranyl ion (UO 2 2+ ) with 8-hydroxyquinoline, [UO 2 (quin) 2 (H’quin)]ÁDMF (1), (Hquin = 8-hydroxyquinoline and H’quin = quinolinium-8-olate, i.e. the zwitterionic form of Hquin). This structure is characterized by X-ray crystal structure determination, elemental analysis and IR spectroscopy. Moreover, we have studied the noncovalent interaction observed in the solid state by means of density functional theory calculations (DFT), molecular electro- static potential (MEP) analysis and the Bader’s theory of ‘‘atoms in molecules’’ (AIM). 2. Experimental 2.1. Materials and methods All reagents used in the syntheses were purchased from commercial sources and were used as received without further purification. Infrared spectrum in the range (4000–600 cm À1 ) was recorded on a Buck 500 Scientific spectrometer using KBr discs. Elemental analysis was carried out with a Thermo Finnigan Flash-1112EA microanalyzer. The X-ray diffraction data were collected with a Bruker-AXS Smart APEX CCD diffractometer. Absorption corrections were performed with SADABS [9], the structure solved by Patterson methods (SHELXS [10]) and refined with SHELXL [10]. Subsequent difference Fourier synthesis and least-squares refinement revealed the positions of the remaining non-hydrogen atoms. Non-hydrogen atoms were refined with http://dx.doi.org/10.1016/j.ica.2014.10.032 0020-1693/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. E-mail addresses: mirzaeesh@um.ac.ir (M. Mirzaei), toni.frontera@uib.es (A. Frontera). Inorganica Chimica Acta 426 (2015) 136–141 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica