This journal is c The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012 New J. Chem., 2012, 36, 865–868 865 Cite this: New J. Chem., 2012, 36, 865–868 Evidence of ionic liquid crystal properties for a DODA + salt of the keplerate [Mo 132 O 372 (CH 3 COO) 30 (H 2 O) 72 ] 42 w Se´ bastien Floquet,* a Emmanuel Terazzi,* b Akram Hijazi, ac Laure Gue´ne´e, b Claude Piguet b and Emmanuel Cadot a Received (in Montpellier, France) 31st October 2011, Accepted 26th January 2012 DOI: 10.1039/c2nj20923c Thermal studies of a DODA + salt of the nanoscopic hollow sphere [Mo 132 O 372 (H 2 O) 72 (CH 3 CO 2 ) 30 ] 42 revealed ionic liquid crystalline properties, which were evidenced by Polarised Optical Microscopy, DSC and SA-XRD. Liquid crystals constitute a fascinating example of functional self- assembled materials. Incorporation of some inorganic compo- nents into liquid crystalline phases appears particularly relevant for the elaboration of synergistic multifunctional materials according to a ‘‘bottom-up’’ approach. 1 To date, a large part of metallomesogens have been prepared by chemical integration of metal ions into organic ligands, which offer a large panel of materials tuned by the design of the organic part. 2 Polyoxo- metalates (POM), often described as polyanionic molecular oxides, exhibit a number of properties in all domains of chemistry. 3 Dietz and Wu demonstrated that the association of various POM with phosphonium or ammonium derivatives leads to ionic liquids or ionic mesomorphic self-assemblies. 4 In such a context, the ‘‘keplerate’’ clusters with the general formula [(Mo 6 O 21 ) 12 (linker) 30 (Ligand) 30 (H 2 O) 72 ] n (Fig. 1) constitute a unique class of nano- scopic hollow spherical clusters capable of exchanging and trapping cations, especially when internal ligands are sulfates. 5 These highly charged nano-capsules can be further encapsulated by surfactants like dioctadecyl–dimethylammonium cations (DODA + ) to give precursors for the preparation of monolayers and Langmuir– Blodgett films, 6 useful for the functionalization of mesoporous silica 7 or for cation-trapping. 8 Taking into account the capability of changing the nature of internal ligands and the properties of the large inner cavity of the keplerate, 5,9 these spherical systems offer promising properties towards sequestration of various substrates. A result obtained with a Mu¨ller’s ring-shaped compound, namely (DODA) 23 [Mo 154 O 462 H 5 ] nH 2 O, supports this expectation since adsorption of various gases and some catalytic properties of the inner open cavity are demonstrated. 10 However, to our knowledge, despite the evidence that these ionic associations easily self-assemble into organized layers or vesicles, the liquid crystal properties of keplerate-based materials were not established. In this contribution, we present preliminary results obtained with (DODA) 36 (NH 4 ) 6 [Mo 132 O 372 (CH 3 COO) 30 (H 2 O) 72 ]75H 2 O, denoted hereafter DODA-Mo 132 , which exhibits ionic liquid crystalline properties between room temperature and temperature of decomposition, after removal of the water molecules. Syntheses of mixed DODA + /NH 4 + salts (DODA) x (NH 4 ) 42x [Mo 132 O 372 (CH 3 COO) 30 (H 2 O) 72 ]nH 2 O were performed by extracting the anion [Mo 132 O 372 (CH 3 COO) 30 (H 2 O) 72 ] 42 (Mo 132 ) from an aqueous solution into a chloroform solution of DODACl. After extraction of keplerate into the organic phase, the final product was precipitated by addition of ethanol, isolated by filtration and washed with ethanol. Interestingly, the proportion of DODA + vs. NH 4 + cations can be easily tuned as a function of the initial ratio DODACl/Mo 132 and several compounds with the DODA + content, x, ranging from 15 to 36 can be isolated when the ratio DODA + /Mo 132 varies from 42 to 182. The synthesis and the Fig. 1 Space filling representation of the spherical cluster [Mo 132 O 372 (H 2 O) 72 (CH 3 CO 2 ) 30 ] 42 (black: carbon, red: oxygen, blue: molybdenum) and schematic view of the DODA + cation. a Institut Lavoisier de Versailles, UMR 8180, University of Versailles Saint-Quentin, 45 av. des Etats-Unis, 78035 Versailles, France. E-mail: sebastien.floquet@chimie.uvsq.fr; Fax: +33 139254381; Tel: +33 139254379 b Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland. E-mail: emmanuel.terazzi@unige.ch; Fax: +41 223796830; Tel: +41 223796035 c Lebanese University, Doctoral School of Science and Technology, Research Platform for Environmental Science (PRASE), Beirut, Lebanon w Electronic supplementary information (ESI) available: Experimental section; SA-XRD data in the 30 to 240 1C temperature range; FT-IR spectra; UV-Visible spectrum, TGA traces, evolution of the lattice parameter h with temperature; representation of the organization of clusters DODA-Mo 132 in the mesophase. See DOI: 10.1039/c2nj20923c NJC Dynamic Article Links www.rsc.org/njc LETTER