As mentioned above, we frequently observed aggregation behavior for PAT 1 and 3 even at UV/vis concentrations, which manifested itself most obviously by significant red-shifting of the E isomers absorption beyond 1000 nm in conjunction with occurrence of a distinct spectral fine-structure. After closer inspection, aggregation of PAT 2 also became evident by elevated and spread-out absorption beyond 1000 nm but no clear additional fine structure was visible in this case. Although redshifting is a known phenomenon for aggregating chromophores, especially for J-aggregates (see for example references ), we were wondering whether it could be used as a mechanism to enable SWIR photoswitching beyond 1000 nm.