MOLECULAR MATERIALS CONFINED IN MESOPOROUS SURFACES, PREPARATION, CHARACTERIZATION AND PROPERTIES

MARTIN HERNÁN GAITÁN; GALO J. A. A. SOLER-ILLIA; LUIS M. BARALDO

Rio de Janeiro - Brasil

Congreso; Nano 2008 – 9th international Conference on Nanostructured Materials; 2008

Centro Brasileiro de Pesquisas

The mesoporous oxides are a family of new materials that offer advantages due to their surface, highly controlled porosity and easy access to species in solution. These characteristics make their functionalization, by adding organic groups or inorganic complexes specially designed an open field of diverse possibilities in the design of new catalyzers, sensors, selective membranes, etc. In this communication we present the functionalization of thin monolayers of TiO2 films using coordination compounds. The molecular materials that we are exploring are “Prussian Blues”. These are hexacyanometalates of inorganic cations. Unlike other salts, these materials are coordination polymers and in that sense they are halfway between an ionic compound, like sodium chloride, and more covalent inorganic solids, like metallic oxides. Prussian blues can be prepared with different hexacyanometalates (Co(III) diamagnetic, Fe(III), Cr(III) paramagnetic) and different metallic ions (provided that the metal ion is labile enough). The classic Prussian Blue is the hexacyanoferrate (II) of Fe(III). This family of compounds has been extensively studied because of their magnetic properties, having been prepared materials that show ferromagnetic ordering at temperatures above room temperature1. Another attractive property of these materials is that they present changes in their magnetic properties induced by light (photo magnetism).2 The preparation of Prussian Blues confined in the TiO2 film pores (pore diameter ~ 13 nm) is initiated with the deposit on a monolayer of  1, 10 phenantroline 5, 6 diona  (Q-phen) that is then coordinated with Fe(II). The exposition of this material to a solution of hexacyanometalate results in the coordination of the cyano complex on the labile Fe(II) sites of the surface. The nitrile end of the coordinated cyanides allows the incorporation of labile more cations to the surface. Repeating this cycle it is possible to build the material layer by layer. The characterization techniques used in this work are: electrochemistry,  EDS, IR, UV vis, SQUID, reflectometry, XPS and TEM.       1)  Ferlay, S.; Mallah, T.; Ouahes, R.; Veillet, P.; Verdaguer, M. "A Room-Temperature Organometallic Magnet Based on Prussian Blue" Nature 1995, 378, 701-703. 2) (a)       Sato, O.; Einaga, Y.; Fujishima, A.; Hashimoto, K. "Photoinduced long-range magnetic ordering of a cobalt-iron cyanide" Inorg. Chem. 1999, 38, 4405-4412.