Highly emissive hand-shaped π-conjugated alkynylpyrenes: synthesis, structures, and photophysical properties.

Three alkynyl-functionalised, hand-shaped, highly fluorescent and stable emitters, namely, 2-tert-butyl-4,5,7,9,10-pentakis(p-R-phenylethynyl)pyrenes have been successfully synthesized via a Pd/Cu-catalysed Sonogashira cross-coupling reaction. The chemical structures of the alkynylpyrenes were fully characterized by their (1)H/(13)C NMR spectra, mass spectroscopy and elemental analysis. Synchrotron single-crystal X-ray analysis revealed that there is a 1-D, slipped, face-to-face motif with off-set, head-to-tail stacked columns, which are clearly influenced by the single, bulky, tert-butyl group in the pyrene ring at the 2-position. Detailed studies on the photophysical properties in both solutions and thin films strongly indicate that they might be promising candidates for optoelectronic applications, such as organic light-emitting devices (OLEDs) or as models for investigating the fluorescent structure-property relationship of the alkynyl-functionalised pyrene derivatives.