Perylene-Based Linear Nonalternant Nanoribbons with Bright Emission and Ambipolar Redox Behavior

Abstract

Here we report stepwise solution-synthesis of linear nonalternant nanoribbons (NNRs), featuring pentagonal rings peri-fused onto the repeating perylene unit. The X-ray single-crystal structures demonstrated their π-backbones as a twisted ribbon, with the longest crystalline length of the nanoribbon up to 3.9 nm. NNRs exhibited an orange to deep-red photoluminescence even under the room light, with absolute Φ_F up to 82 %, most likely due to ring-strain induced molecular stiffness. Benefiting from the enlarged size and the antiaromatic character of pentagons, all of NNRs possessed ambipolar redox properties, especially for longer nanoribbons showing multiple reversible reductions and oxidations. In addition, experimental and theoretical results indicated a ground state open-shell singlet diradicaloid for the dication of longer NNRs. Our studies reveal the intriguing nonalternant structures and physical properties of this type of nanoribbons, involving the striking effects of the multiple annulated pentagons, and also provide fundamental insights into their electronic structures.

Keywords: Ambipolar Redox Chemistry; Diradicals; Nanoribbons; Perylenes; Photochemistry.