The above results give the proof-of-concept for the single-chain luminogen of PLVPs and further understanding of its PL mechanism. As pyridine, as well as carbonyl groups, are well-known organic ligands, we speculate that the intra-chain interactions of PLVP will be interfered by introducing metal ions. Namely, the intra-chain interactions of PLVP may be broken by the presence of metal ions, which will result in the change of photophysical properties. To this end, the response of PLVP to a variety of metal ions is investigated. Figure shows the PL spectra of PLVP-3 in DMF (0.05 mM) with 20 mM metal ions. It is found that the presence of Co 2+ , Na + , and Zn 2+ could slightly enhance the PL of PLVPs, whereas the other ions, i.e., Ni 2+ , Eu 3+ , Ga 3+ , Cu 2+ , and Fe 3+ , would reduce the PL of PLVPs (Figure and). In particular, Fe 3+ significantly quenched the PL of PLVP-3. Generally, the quenching effect is determined by the metal ion charge/radius ratio. Namely, the stability of the metal complexes increases with increasing of the metal ion charge/radius ratio. As Fe 3+ has the largest charge/radius ratio than the other ions used in this work (Table ), it possesses stronger interaction with pyridines. Figure show the PL spectra of PLVP-3 in DMF with varied concentration of Fe 3+ , With the increase of Fe 3+ concentration, the fluorescence intensity of PLVP-3 gradually decreased. The UV-Vis absorption spectra of PLVP-3 with the addition of different metal ions (Figure ) shows a new absorption band at 300 -450 nm upon adding Fe 3+ , suggesting that Fe 3+ could coordinate with the carbonyl groups and pyridine, breaking the intra-chain interactions of PLVP, leading to the quenching of PL. Again, it evidences that the intra-chain interaction of PLVPs is critical to its intrinsic PL. Moreover, it is noteworthy that PL of PLVP is not very sensitive to the presence of Fe 3+ . This may be because the strong intra-chain interactions and the steric hindrance weaken the coordination abilities between ligands and Fe 3+ ions.