Synthesis, structure and optoelectronic properties of rigid 3D tetraindeno-fused spirofluorene with thioxanthene or dioxothioxanthene substitutes

Abstract

This work reports the synthesis and characterization of two blue emitters. Their 3D rigid structures are the appealing feature.

Oligofluorene with multiple spiro-connections: its and their use in blue and white OLEDs

“…S5, ESI †). 36,39 Moreover, in the case of Spiro-F, two emission bands at 386 and 406 nm in CH 2 Cl 2 were observed, similar to those in the above-mentioned model compounds, which further indicates that the spiro-carbon linkages disrupt intramolecular electronic coupling. Furthermore, the symmetric mirror images of the absorption and emission spectra, as well as the very small Stokes shift (4 nm), coincide with the super-rigid molecular structure of Spiro-F.…”

“…34 Interestingly, reports have shown that the S1/T1 values of Spiro-4S and Spiro-4SO 2 are the same. 36 Thus, we can conclude that the optoelectronic properties of Spiro-F mainly arise from its DFF backbone.…”

“…As we had previously reported, starting material tetraketone Spiro-4 was prepared on a multigram scale in a three-step synthesis. 35,36 Firstly, excess fresh Grignard reagent, namely [1,1 0 -biphenyl]-2-ylmagnesium bromide, was prepared to ensure efficient nucleophilic attack upon tetraketone Spiro-4O. Then, the reaction was quenched with dilute hydrochloric acid to afford the tetra-alcohol intermediate, which was used directly in the next step without purification.…”

“…S5, ESI †). 36,39 Two face-toface fluorenes 8.76 Å in distance are quasi-parallel. This is one ''super-rigid'' structure characterized using X-ray crystallography.…”

“…1 bottom left) no intermolecular p-p interactions are detected between the two DFF p-conjugated systems, due to steric hindrance from perpendicular fluorene units. 36…”