Inorganic-organic nanocomposite materials based on macrocyclic compounds

The synthesis, structural characterisation, properties and applications of inorganic-organic hybrid materials (nanocomposites) containing macrocycles are reviewed. Three different ways to prepare such materials are discussed: i) intercalation in layered host solids, ii) entrapping into inorganic mat rices generated by sol-gel, and iii) grafting of macrocycles on inorganic s urfaces. Macrocyclic compounds, as crown ethers and cryptands, were the gue st organic species used in intercalation processes. The host inorganic soli ds were layered silicates, vanadium pentoxide xerogel, transition-metal dic halcogenides and phosphorus trichalcogenides. The resulting nanocomposites present synergic host-guest properties useful for applications as solid ele ctrolytes, ion-selective membranes and electrochemical sensors. Alternative ly, nanocomposites based on macrocycles can be obtained by entrapping of su ch compounds into inorganic matrices generated by sol-gel, using different organosilanes as precursors (TMOS, TEOS, ETEOS, MAPTMS, etc). Electrodes ba sed on such systems are sensitive to alkaline cations, lead, silver and amm onium ions giving linear potentiometric responses in a wide concentration r ange. Finally, the grafting of macrocycles on inorganic surfaces is also di scussed. Silica can be functionalised by anchorage of macrocycles able to c onfer specific properties and reactivity to the inorganic substrate. The ma in applications of this last class of nanocomposites have been found for ch romatography purposes, including separation of cations, anions and non-elec trolytic organic compounds.