A highly fluorescent chemosensor based on 1,8-naphthyridine with high sensitivity and selectivity toward Ni²⁺/Cu²⁺ over other cations both in aqueous solution over a wide pH range (4–10) and in cellular environments was developed. Counteranions such as acetate, sulfate, nitrate, and perchlorate have no influence on the detection of such metal ions. Ethylenediamine showed high selectivity toward the in situ-prepared Cu²⁺ complex over the Ni²⁺ complex, which can be applied to distinguish Ni²⁺ and Cu²⁺. The Ni²⁺-induced fluorescence on–off mechanism was revealed to be mediated by intramolecular charge transfer from the metal to the ligand, while that by Cu²⁺ involves intramolecular charge transfer from the ligand to the metal, as confirmed by picosecond time-resolved fluorescence spectroscopy and time-dependent density functional theory calculations.

中文翻译：

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1,8-萘啶衍生的Ni ²⁺ / Cu 2 ⁺ -选择性荧光化学传感器，具有不同的电荷转移过程

开发了一种基于1,8-萘啶的高荧光化学传感器，该传感器在宽pH范围（4-10）的水溶液中和细胞环境中对Ni ²⁺ / Cu ^2+的灵敏度均高于其他阳离子，并且具有选择性。诸如乙酸根，硫酸根，硝酸根和高氯酸根之类的抗衡离子对这种金属离子的检测没有影响。乙二胺对原位制备的Cu ²⁺络合物具有比Ni ²⁺络合物更高的选择性，可用于区分Ni ²⁺和Cu ²⁺。Ni ²⁺诱导的荧光开-关机制被揭示是由分子内的电荷从金属转移到配体介导的，而由Cu介导的²⁺涉及分子内电荷从配体到金属的转移，这已被皮秒时间分辨荧光光谱法和随时间变化的密度泛函理论计算所证实。