Star-Shaped Polycyclic Aromatics Based on Oligothiophene-Functionalized Truxene: Synthesis, Properties, and Facile Emissive Wavelength Tuning

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Abstract
A facile approach to soluble star-shaped oligothiophene-functionalized polycyclic aromatics based on truxene is developed in this Communication. The Suzuki coupling reactions afford the thiophene-containing polycyclic aromatics with long branches (about 2.1 nm length from the heart to the periphery) from truxene precursor with excellent yields. The unsubstituted alpha-positions of thiophene rings allow for efficient halogenation and for further functionalization. The investigation of proton NMR spectra indicates that the hexahexyl groups efficiently prevent the self-association through the arene-arene pi-stacking. Chemical shifts belonging to methylene groups move more upfield than do those of methyl groups. These chemical shift values (about 0.5-0.6 ppm) are quite lower than those of normal methyl and methylene groups. We also prepare a dendritic hyperbranched polymer P1 through FeCl3 mediated oxidative polymerizations. The photophysical properties of all compounds possessing good symmetry are investigated by UV-vis and emission measurement.