The spectroscopic properties of 2a-c were investigated in diluted DCM solutions (see Fig. ). All compounds display transitions in the UV-visible range up to 500 nm. 2a and 2b display almost the same absorption properties with a first broad band around 300 nm. Those two compounds also display a larger band in the visible range (max(2a) = 406 nm; max(2b) = 415 nm, see Table and Fig. ). This large band is attributed to Internal Charge Transfer (ICT) from the arylamine donor to the benzophosphole acceptor as it has been reported for similar compounds. 11 2c shows a maximal absorption wavelength at 327 nm and broad shoulder up to 480 nm (vide infra for theoretical rationalization). 2a and 2b display fluorescence in diluted solution (DCM) with their maximum wavelengths at 578 nm and 637nm, respectively (Fig. and Table ). A stronger redshift ( = 59 nm) is observed compared to the absorption, which is typical for molecules showing ICT. A solvent dependence study on 2a indicates a positive solvatofluorochromism confirming the ICT nature of this transition (Fig. ). Both 2a and 2b show moderate photoluminescence quantum yield (PLQY) of 0,34 and 0,09, respectively. This difference in PLQY follows the energy-gap rule and is therefore unsurprising. 2c does not luminesce in diluted DCM solution.