A cross-shaped organic framework: a multi-functional template arranging chromophores

This work explores the use of a cross-shaped organic framework that is used as a template for the investigation of multi-functionalized chromophores. We report the design and synthesis of a universal cross-shaped building block bearing two bromines and two iodines on its peripheral positions. The template can be synthesized on a gram scale in a five-step reaction comprising an oxidative homo-coupling macro-cyclization. The formed scaffold was selectively functionalized <i>via</i> Suzuki cross-coupling reactions with methoxynaphthalene, naphthalimide and BODIPY derivatives, yielding a library of cross-shaped and chromophore-decorated model compounds, all of which were fully characterized. The formed racemic bis- and tetra-substituted crosses were resolved <i>via</i> chiral stationary phase HPLC, and assignment of the enantiomers was done <i>via</i> comparison of experimental and simulated electronic circular dichroism spectra as well as enantiomer single-crystal analysis. Additionally, the hybrid naphthalimide/BODIPY chromophore was found to be acting as an intramolecular Förster energy resonance transfer pair, which was investigated in more detail. With this easy-to-functionalize universal building block, we believe it might prove to be useful in the study of different sets of chromophores.