Fully Spiro-Configured Terfluorenes as Novel Amorphous Materials Emitting Blue Light

A series of fully spiro-configured terfluorenes were synthesized and characterized to be amorphous materials showing a T_g of 296 °C with dendritic aromatic pendants, the highest value ever reported for organic molecular systems. X-ray single-crystal analysis of key structural moieties indicated nearly perpendicular orientations at all spiro-links. The spectroscopic comparison of solid film and dilute solution suggested absence of aggregates in the ground state and no increase in torsion angle with an increasing volume of the aromatic pendant. All these conformational characteristics are consistent with molecular mechanics simulation. Thermal annealing in argon caused a decrease in photoluminescence quantum yield with phenyl pendants but an increase with dendritic pendants. These can be understood in terms of local morphological reorganization of molecules to enhance or inhibit interactions between the backbone chromophores.