Supramolecular Assembly at Interfaces: Formation of an Extended Two-Dimensional Coordinate Covalent Square Grid Network at the Air-Water Interface
Reaction of a Langmuir monolayer of an amphiphilic pentacyanoferrate(3+) complex with Ni2+ ions from the subphase results in the formation of a two-dimensional iron-nickel cyanide-bridged network at the air-water interface. The network can be transferred to various supports to form monolayer or multilayer lamellar films by the Langmuir-Blodgett (LB) technique. The same network does not form from homogeneous reaction conditions. Therefore, the results demonstrate the potential utility of an interface as a structure director in the assembly of low dimensional coordinate covalent network solids. Characterization of the LB film extended networks by X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy, SQUID magnetometry, X-ray absorption fine structure (XAFS), and grazing incidence synchrotron X-ray diffraction (GIXD) revealed a face-centered square grid structure with an average domain size of 3600 Å2. Magnetic measurements indicated that the network undergoes a transition to a ferromagnetic state below a Tc of 8 K.