Exploring dynamic dimers for singlet fission in thiophene-functionalized pentacene derivatives

Artikel i vetenskaplig tidskrift, 2026

Singlet fission (SF) is a spin-allowed photophysical process of considerable interest for next-generation solar-energy conversion. Orientation, proximity and orbital overlap of the chromophores largely affect the success of SF, which can be overcome by forming covalent-linked dimers. However, triplet separation then becomes a key challenge for efficient SF. Therefore, we are introducing a dynamic, non-covalent dimer strategy, that enables effective SF without requiring covalent linkers or solid-state packing. The chromophores associate only through weak intermolecular interactions forming dynamic dimers, still able to undergo SF. Two TIPS-pentacene derivatives functionalized with a thiophene unit at the 2-position, bearing either an aldehyde (PTA) or a carboxylic acid (PTCA), were synthesized to promote π-stacking and hydrogen bonding. Comprehensive photophysical characterization shows that both compounds can undergo efficient SF even at micromolar concentrations, with initial rates of 1.3 × 10¹¹ and 5.6 × 10¹⁰ s⁻¹, respectively. Furthermore, unlike covalent dimers or crystalline systems, our approach facilitates tunability of the excited-state dynamics by concentrations, pH, and the introduction of cations that form dynamic ion-bridges through weak coordination. These results demonstrate that dynamic, non-covalent assemblies offer a versatile platform for modulating SF in solution and opening new avenues for designing adaptive SF materials.