The UV-Vis absorption spectra of the three emitters in dilute toluene are shown in Figure and the photophysical properties are summarized in Table . All three compounds exhibit strong absorption bands at around 320 nm, which are assigned to locally excited (LE) π-π* transitions of the donors and acceptor moieties based on the TD-DFT predicted transitions (Figure ). A strong and broad absorption band is observed at 427 nm (ε = 31×10 3 M -1 cm -1 ) for TPAPyAP, 456 nm (ε = 37×10 3 M -1 cm -1 ) for TPAPyBP and 469 nm (ε = 19 ×10 3 M -1 cm -1 ) for TPAPyBPN, which is assigned in each case to an intramolecular charge transfer (ICT) transition from the TPA donor to the acceptor moiety. The molar absorption coefficient of the ICT band at 427 nm of TPAPyAP is higher than that of ICT band at 469 nm of TPAPyBPN, which aligns with the TD-DFT calculated oscillator strength (f = 0.47 for TPAPyAP and f =0.36 for TPAPyBPN, Figure ), while TPAPyBP exhibits the highest e at 456 nm (f of 0.39). The ICT absorption bands of these three compounds also expectedly shift to lower energies as the acceptor strength increases. All compounds show unstructured and broad PL spectra in toluene (Figure ), indicative of an excited state of ICT character, with peak maxima, lPL, at 513 nm, 550 nm, and 575 nm for TPAPyAP, TPAPyBP and TPAPyBPN, respectively. Positive solvatochromism is observed for all three compounds (Figure , Table ), which is consistent with the ICT nature of the emissive excited state. The optical bandgaps, Eg, calculated from the intersection point of the normalized absorption and emission spectra, are 2.62 eV, 2.46 eV, and 2.38 eV for TPAPyAP, TPAPyBP and TPAPyBPN, respectively (Figure ). The photoluminescence quantum yields, ΦPL, in degassed toluene solution of TPAPyAP, TPAPyBP and TPAPyBPN are 93, 89, and 86%, respectively, decreasing to 85, 81, and 78% upon exposure to oxygen (Table ).