Coordination polymer nano-objects into ionic liquids: Nanoparticles and superstructures Joulia Larionova a, * , Yannick Guari a, * , Alexei Tokarev a , Elena Chelebaeva a , Carlos Luna b,1 , Claudio Sangregorio b, * , Andrea Caneschi b , Christian Guérin a a Institut Charles Gerhardt, UMR 5253, Chimie Moléculaire et Organisation du Solide, Université Montpellier II, Place E. Bataillon, 34095 Montpellier cedex 5, France b INSTM Research Unit – Dipartimento di Chimica, Università di Firenze, via della Lastruccia 3, 50019 Sesto F.no, Firenze, Italy article info Article history: Received 13 February 2008 Accepted 10 March 2008 Available online 15 March 2008 This paper is dedicated to Prof. Dante Gatteschi. Keywords: Cyano-bridged coordination polymers Ionic liquids Nanoparticles Superparamagnetic Spin-glass-like Magnetic properties abstract A new exploit of ionic liquids as an alternative reaction media in the synthesis of cyano-bridged coordi- nation polymers nano-objects such as nanoparticles and their superstructures is discussed. Stable colloidal solutions containing nanoparticles of cyano-bridged coordination polymers Cu 3 [Fe(CN) 6 ] 2 / [C n -MIM][An] (where n = 2, 4; An = BF 4 , Cl) or their superstructures were prepared in the corresponding 1-R-3-methylimidazolium salts [C n -MIM][An] which acts as both the stabilizing agent and the solvent. Different conditions, such as temperature, nature of the ionic liquid counter anion and N-alkyl substi- tuted chain length, water content and microwave action have been varied in order to check their influ- ence on the size, the shape and the organisation of the nanoparticles. A special emphasis is devoted to detailed studies of the magnetic properties of these frozen colloids. The dynamic study shows that the relaxation of magnetisation for the nanoparticles and their superstructures is influenced by interparticle interactions leading to appearance of a cluster-glass-like behaviour in these systems. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Cyano-bridged homo- and hetero-metallic coordination poly- mers belong to an important family of molecule-based materials presenting interesting magnetic, optic, photo-switchable and intercalation properties [1]. Consequently, during the last 30 years, numerous compounds of this family with various structures have been synthesised and extensively studied due to their fundamental interest as well as their technological applications in many fields [2]. About eight years ago, the research activity on the synthesis and studies of size and shape controlled cyano-bridged metallic coordination polymers at the nano-sized level regime started to develop [3]. Such interest is due to the fact that thanks to the very important surface/core atoms ratio or confinement effects, nano- meter-scaled materials often exhibit the appearance of new inter- esting size-dependent physical and chemical properties, which cannot be observed in their bulk analogous [4]. For this reason, such nano-sized materials are interesting candidates for applica- tions in many fields, including electronics, catalysis, separation, biology, medical imagery and others [5]. A pioneering work con- cerning the synthesis of cyano-bridged coordination polymer nano-objects has been realised by Mann and co-workers, who pre- pare cubic shaped nanocrystals of Prussian Blue of ca. 12–50 nm stabilized within reverse micelles [6]. Then, the synthesis of cya- no-bridged metallic nanoparticles of different size by using reverse micelles [7], polymer [8] and biopolymer [9] as stabilizing agents, amorphous [10] and mesostructured silica [11] as matrixes were reported. Recently, we reported the synthesis of cyano-bridged coordina- tion polymers nanoparticles of adjustable size by using ionic liq- uids (ILs) as both stabilizing agent and reaction media [12]. It should be noted that ILs are typically composed of organic cations with a variety of moieties such as quaternary ammonium cation, pyrrolidinium, phosphonium, sulfonium and other more exotic cations along with a variety of inorganic anions [13]. Their unique physico-chemical properties, such as a low melting point, a wide liquid range, negligible vapour pressure, good solubility character- istics, relatively low viscosity, high fluidity, non-flammability, a wide electrochemical window, tolerance to strong acids, and their excellent thermal and chemical stability provide their rapid emer- gence as alternative solvents for chemical reactions and separa- tions [14]. ILs were also found interesting as a media for the synthesis of inorganic matters including the stabilization of various nano-sized objects [15]. As concerning coordination polymer 0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2008.03.038 * Corresponding authors. Fax: +33 4 67 14 38 52 (J. Larionova). E-mail addresses: joulia@univ-montp2.fr (J. Larionova), guari@univ-montp2.fr (Y. Guari), claudio.sangregorio@unifi.it (C. Sangregorio). 1 Present address: Facultad de Ciencias Físico-Matemáticas, Universidad Autónoma de Nuevo León, Av. Pedro de Alba s/n, San Nicolás de los Garza, 66450 Nuevo León, Mexico. Inorganica Chimica Acta 361 (2008) 3988–3996 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica