Supramolecular organization and optical properties of nanoscale and microscale films of an anisometric europium(III) complex

An anisometric Eu(III) complex was used to produce nanoscale and microscale films by three different methods. These films demonstrated considerable differences in their supramolecular organization and optical properties. The impact of the fabrication method and supramolecular organization on optical properties of the films was studied. The nanoscale films deposited from solutions were found to have excitation spectra identical to those of diluted solutions with the maximum at 330 nm. The microscale films fabricated by vitrification from their melts or solvent evaporation from solutions were found to contain J-aggregates. Their spectra were comparable to those of concentrated solutions with the maximums at about 400 nm. For the first time, we report growing a monocrystal of a lanthanide’s mesogenic complex and its characterization by X-ray crystallography. The type of intermolecular interactions was identified and the size and shape of the aggregates were characterized. Formation of J-aggregates in microscale vitrified films was shown to be the key factor that provided these materials with the properties of excitation not only by UV light but also by inexpensive visible light sources with wavelengths corresponding to the absorption range of 390–425 nm.