Accordingly, PyPhCz and PyCz display clearly different slopes before and beyond the threshold, supporting our hypothesis of HLCT states (see Figure and). In PyPox the NTO confirms a distinct CT state upon excitation, where hole and electron are strongly segregated to the donor and acceptor moieties, respectively (see Figure and d). TD-DFT also allows us to determine the oscillator strengths (f) for the S1 geometries of our molecules. In fact, we see that PyFlCz and PyPhCz have similar f > 1, whereas PyCz and PyPox have f < 0.5 (see Table The ϕ differs when measured in aerated or in degassed (argon-purged) DCM, indicating potential involvement of triplet states. The ϕ is higher in degassed DCM as in oxygen. This can be explained by quenching of excited statespredominantly triplet stateswhen triplet oxygen is present. When we check the photoluminescence lifetimes (τ) in DCM, we observe that most of our compounds exhibit monoexponential and fast decay; however, also here we see longer lifetimes for our pyrenes in degassed solvent, again indicating the involvement of triplet states (see Table ). Only the decay of PyPox requires fitting with a biexponential decay. Together with the low ϕ of only 2 %, this biexponential decay can be rationalized by considering that several nonradiative decay mechanisms will be at play together.