A cationic amphiphilic molecule was synthesized and employed
to encapsulate Lindqvist ([M6O19]2?)
and Keggin polyoxometalates
([SiM12O40]4?, M=Mo, W) to
form hybrid molecules through electrostatic interaction. The X-ray diffraction
results illustrate that the former hybrids possess lamellar nanostructures in
their solid states, while the latter hybrids show a cubic Im3m packing model with low intensities and poor long-range order. These hybrids have
clear charge-transfer characters as shown in their deeper colors and UV–vis
diffuse reflectance spectra. According to the reported reduction potentials of
the POM acceptors and the band gaps deduced from their diffuse reflectance
spectra, we have calculated the theoretical values of the lowest unoccupied
molecular orbital (LUMO) position similar to the electron affinity
(EA) of solid materials. Such energy level parameters are
comparable to those of electroluminescence and electron-transport materials
commonly used in organic electroluminescence devices. These
organic–polyoxometalate charge-transfer salts have more advantages, such as
higher decomposition temperatures, easier film fabrication and better electron
affinities, which presumably would be used for electron-transport materials in
the area of the electroluminescence.