Langmuir–Blodgett films of hexamolybdate and porphyrin prepared by two different approaches: Synthesis, characterization and electrical properties

A novel covalently-linked organic–inorganic hybrid compound [(n-C4H9)4N]2[Mo6O18(NPor)] (OpL) [Por = 5-(p-phenyl),10,15,20-triphenylporphyrin)] was prepared by the reaction of 5-(p-aminophenyl)-10,15,20-triphenylporphyrin (Op) with [(n-C4H9)4N]2[Mo6O19] (L) in the presence of N,N’-dicyclohexylcarbodiimide (DCC) in anhydrous DMSO, and characterized by 1H NMR, IR, UV–Vis, fluorescence spectra. Monolayer and multilayer film of OpL was fabricated on different substrates by the Langmuir–Blodgett (LB) technique using H2O as the subphase. For comparison, another type of organic–inorganic hybrid film composed of noncovalently-linked Op/L system was also deposited on the same substrate under the same condition by the LB technique using an aqueous solution of L as the subphase. The as-prepared organic–inorganic hybrid films were characterized by π-A isotherms, atomic force microscopy imaging, scanning tunneling microscopy. The results indicate that stable monolayers can be formed at the air–water interface for OpL, and at the air-L solution interface for Op. The two LB films containing OpL and Op/L display interesting electrical conductivity.