Photophysical properties of the compounds were measured in solid state in both poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVA) polymer hosts. The PVA films were dropcast from 0.1 M H2SO4 to replicate somewhat the environment in 0.1 M H2SO4 solution. Supplementary Figures show the steady state absorption, excitation and photoluminescence profiles of all the compounds at 1 wt%. The 7ax series (Figure ) show poor emission in PMMA however in the PVA films the emission has higher intensity and is very similar to that observed in 0.1 M H2SO4 confirming that doubly protonated species in the PVA films have been achieved. In fact, all twelve compounds in PVA show emission very similar to that found in 0.1 M H2SO4, meaning that it is likely we have the doubly protonated compound dominating the emission in all PVA films. The weak emission of the 7bx series (the compounds with one methoxy group, Figure ) shows vibronic character in PMMA, albeit with a red shifted emission band. This is similar to what is observed in the 7cx PMMA films (See Figure ). We believe this additional red band is perhaps a result of aggregation or some CT species that may be activated in the packing of the PMMA films. The 7dx series (Figure ) behave very similar to the 7ax series with very weak emission in PMMA and the typical emission of the doubly protonated species in the PVA film. To re-emphasise, since the PVA films are made from 0.1 M H2SO4 the emission of the compounds in these films can be explained because of protonation of both the nitrogen atoms. The subsequent change in the electronic structure from protonation gives rise to the broader redshifted LE band as observed in solution.