Three new 1,8-naphthalimide derivatives M1–M3 with different substituents at the C-4 position have been synthesized and characterized. Their photophysical properties have been investigated in organic solvents of different polarity, and their fluorescence intensity was found to depend strongly on both the polarity of the solvents and the type of substituent at C-4. For compounds M1 and M2 having a tertiary amino group linked via an ethylene bridge to the chromophore system, high quantum yield was observed only in non-polar media, whereas for compound M3, the quantum efficiency did not depend on the medium polarity. The effect of different metal ions (Ag⁺, Ba²⁺, Cu²⁺, Co²⁺, Mg²⁺, Pb²⁺, Sr²⁺, Fe³⁺, and Sn²⁺) on the fluorescence emission of compounds M1 and M2 was investigated. A significant enhancement has been observed in the presence of Ag⁺, Pb²⁺, Sn²⁺, Co²⁺, Fe³⁺, as this effect is expressed more preferably in the case of M2. Both compounds have shown significant pH dependence, as the fluorescence intensity was low in alkaline medium and has been enhanced more than 20-fold in acidic medium. The metal ions and pH do not affect the fluorescence intensity of M3. Density-functional theory (DFT) and Time-dependent density-functional theory (TDDFT) quantum chemical calculations are employed in deciphering the intimate mechanism of sensor mechanism. The functional properties of M1 and M2 were compared with polyamidoamine (PAMAM) dendrimers of different generations modified with 1,8-naphthalimide.

中文翻译：

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1,8-萘二甲酰亚胺新衍生物的合成，光物理特性和传感器活性。

合成并表征了三个在C-4位置具有不同取代基的1,8-萘二甲酰亚胺新衍生物M1 - M3。已经在不同极性的有机溶剂中研究了它们的光物理性质，发现它们的荧光强度在很大程度上取决于溶剂的极性和C-4取代基的类型。对于具有通过乙烯桥连接至发色团系统的叔氨基的化合物M1和M2，仅在非极性介质中观察到高量子产率，而对于化合物M3，量子效率不取决于介质极性。不同金属离子（Ag ⁺，Ba ²⁺，Cu 2 ⁺，Co 2 ⁺，Mg 2 ⁺，Pb 2 ⁺，Sr 2 ⁺，Fe ³⁺和Sn ²⁺）对化合物M1和M2的荧光发射进行了研究。在Ag ⁺，Pb 2 ⁺，Sn 2 ⁺，Co 2 ⁺，Fe ³⁺的存在下已观察到显着增强，因为在M2的情况下更优选表达这种效果。两种化合物均显示出显着的pH依赖性，因为在碱性介质中荧光强度较低，而在酸性介质中则增强了20倍以上。金属离子和pH值不会影响M3的荧光强度。密度泛函理论（DFT）和时变密度泛函理论（TDDFT）的量子化学计算被用来解释传感器机制的内在机理。将M1和M2的功能特性与用1,8-萘二甲酰亚胺改性的不同代的聚酰胺基胺（PAMAM）树状聚合物进行了比较。