Similarly, the spectral response of TPAPyAP and TPAPyBPN also revealed a binding selectivity towards ZnCl2, showing a new, red-shifted emission band at 650 nm and 655 nm, respectively (Figure ). The Job plot for both compounds indicates the same 1:1 binding stoichiometry as that observed for TPAPyBP (Figure ). Given the more distinct and stronger optical response using TPAPyBP compared to TPAPyAP and TPAPyBPN, here we only focused on TPAPyBP.