The UV-Vis absorption and photoluminescence (PL) spectra of DMACPyBP, PXZPyBP, and DPACzPyBP in dilute toluene solutions are shown in Figure . The absorption spectrum for each emitter shows two characteristic bands: a high-energy, sharp, and strong absorption band below 390 nm, which can be attributed to locally excited (LE) π-π* transitions within both the donor and acceptor moieties, and a weak, broad, low energy absorption band above 450 nm, associated with intramolecular charge transfer (ICT) from the donor to the PyBP acceptor. As expected, the ICT band shifts to lower energy as the donor strength increases, shifting from 470 nm for DMACPyBP to 520 nm for PXZPyBP and 510 nm for DPACzPyBP, consistent with the TDA-DFT-calculated transitions (Figure ).