A ready-to-use hetero-tricyclic compound, 5,5′-(furan-2,5-diyl) bis (1,3,4- oxadiazol-2-amine) (5), was synthesized with a good yield; it has an suitable fluorescence characteristic and research founded that it can respond to trace Pd²⁺ in water at a normal pH range. A fluorescence titration revealed the detection limit for Pd²⁺ was as low as 3.97 × 10⁻⁹ M. Density-functional theory calculation using Guassian09 implied that the breakage of conjugation and coplanarity of compound 5 led to fluorescence quenching. Compound 5 could be applied as a chemical probe to detect trace amounts of Pd²⁺ with good accuracy, fast response time, excellent selectivity, and high sensitivity. FT-IR, NMR, and MS were used to characterize the chemical structure of compound 5.

中文翻译：

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水中 Pd2+ 的即用型荧光探针：基于 1,3,4-恶二唑的新型三环杂环基

以良好的收率合成了即用型杂三环化合物5,5'-(呋喃-2,5-二基)双(1,3,4-恶二唑-2-胺) ( 5 )；它具有合适的荧光特性，研究发现它可以在正常 pH 值范围内响应水中的痕量 Pd ²⁺。荧光滴定显示 Pd ²⁺的检测限低至 3.97 × 10 ^-9  M。使用 Guassian09 的密度泛函理论计算表明化合物5的共轭断裂和共面性导致荧光猝灭。化合物5可用作化学探针检测痕量 Pd ²⁺具有准确度好、响应时间快、选择性好、灵敏度高等特点。FT-IR、NMR和MS用于表征化合物5的化学结构。