Multistimuli-Responsive Materials from Benzothiadiazole-Based Charge-Transfer Chromophores: Interdependence of Optical Properties and Aggregation

We investigate a family of multipolar V‐shaped chromophores bearing an A'‐D‐A‐D‐A' structure, where 2,1,3‐benzothiadiazole, acting as the central electron acceptor (A), is linked to two thiophene‐based electron donating moieties (D) end‐capped with alkyl‐cyanoacetate substituents (A'). The spectroscopic properties of thin films and powders are investigated, in comparison to solutions and nanoaggregates. The optical properties strongly depend on the aggregation state and can be tuned via thermal treatment (annealing) on the films and via mechanical treatment (grinding) on the powders, demonstrating that these materials are multistimuli‐responsive. The spectroscopic analysis reveals the partial formation of J‐aggregates both in the films and in the powders, despite the weak luminescence. We interpret this behavior as due to the partial formation of poorly fluorescent red‐shifted aggregates acting as sink in an efficient excitation energy transfer process from J‐aggregates.