absorption band located at 413 nm (ε = 42.9 × 10 3 M -1 cm -1 for TPPQ, ε = 28.2 ×10 3 M -1 cm -1 for 4DMAC-TPPQ and ε = 32.9 × 10 3 M -1 cm -1 for 4PXZ-TPPQ ) is of mixed LE/CT character, based on an analysis of the TD-DFT calculations, where the LE is transition is centred on the acceptor and the CT transition occurs from the phenylene groups to the PQ (Figure ). The weakly absorptive CT band of 4PXZ-TPPQ (ε = 7.57 × 10 3 M -1 cm -1 at labs = 506 nm) and 4DMAC-TPPQ (ε = 8.75 × 10 3 M -1 cm -1 at labs = 475 nm) reflects the poor orbital overlap between the donor and the PQ acceptor (Figure ); notably, the red-shifted band in 4PXZ-TPPQ is consistent with its smaller HOMO-LUMO gap compared to that of 4DMAC-TPPQ, as observed in the electrochemistry study. The photoluminescence (PL) of TPPQ does not change as a function of solvent, with a peak maximum, lPL, of around 456 nm, and a shoulder band at around 476 nm (Figure ). This, coupled with the reasonably narrow FWHM (56 nm), indicates that the emission emanates from a LE state. By contrast, 4DMAC-TPPQ and 4PXZ-TPPQ show unstructured and broad emission that is sensitive to solvent polarity and thus is assigned to originating from a CT state. In toluene, 4DMAC-TPPQ emits at lPL of 650 nm, while 4PXZ-TPPQ emits at lPL of 762 nm (Figure and Table ).