RESUMO
With large surface area and versatile electronic behaviour, the composites of Fe4S4(SRS)4 nanoclusters and functionalized carbon nanotubes (f-CNTs), are expected to catalyze the conversion of protons to hydrogen gas at lower electro-potentials with higher output than a platinum electrode. In search of a non-noble metal based catalytic material, we report for the first time, the isolation of unimolecular iron-sulfur cubane cluster, [Fe4(µ-S)4(mnt)4], (1) (mnt = maleonitriledithiolate) as nanocubes (63×85×120 nm) in MeCN-EtOH (MeCN is acetonitrile, while EtOH is ethanol) solvents and bimolecular [NBu4]4[Fe4(µ-S)4(mnt)4] as nanocuboctahedra (120×121×125 nm) in pure EtOH. The cubic shape of the nanocrystal reminds its geometrical relationship with a molecular cube and one of sides of the nanocube and nanocuboctahedron matches at 120 nm. The nanocubes of Fe4S4(SRS)4 have been immobilized on f-CNTs and characterized by SEM and TEM methods which indicate that clusters of Fe4S4 of diameter (8-9 nm) interact with surfaces, sidewalls and tip of the f-CNTs. A ferrocene type of interaction could not be observed with f-CNTs, because nanoparticles are not found in CNT-inner cavity. The interaction could be either adsorption or hydrogen bonding interactions between -COOH/-OH groups of f-CNTs and N≡C terminals of iron-sulphur nanoclusters leading to immobilization of an iron-sulfur nanocluster on a single CNT molecule or the iron-sulfur nanoclusters can be entrapped between two CNT molecules.