Computational design of covalently bound dimers for singlet fission

We present two different computational approaches to design covalently bound dimers for singlet fission. Both designs aim at maximizing the effective coupling between the initial singlet excited state 𝑆∗ and the double triplet state 𝑇 𝑇 , by tuning the interaction (mainly through-space) between the chromophore units. Design I is based on a preliminary search for the optimal relative arrangements of chromophores in a space of possible stacked pair geometries. Then, the optimized dimeric arrangements are used as targets for the covalent connection of the two chromophores. In design II, all viable ways to covalently bind the two chromophores are considered, using a given set of linkers. Next, the most promising covalent dimers for singlet fission, among our tested candidates, are identified. The application of our approaches to a locked 1,3-diphenyl-isobenzofuran chromophore and a diamino-fluoroquinone compound allowed to design several promising dimers for singlet fission, featuring large 𝑆∗-𝑇 𝑇 effective couplings and favorable energetics.