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<p>An adenine–succinate-based metal–organic framework, [Cu(adenine)(succinate)]<sub>n</sub> (CuAS), was synthesized via a solvothermal method and structurally characterized by single-crystal X-ray diffraction, PXRD, IR spectroscopy, TGA, and elemental analysis. CuAS forms a three-dimensional framework featuring two directional channels along the <i>a</i>- and <i>b</i>-axes, with amino groups oriented toward the cavities. In methanol, CuAS exhibits a UV–Vis absorption maximum at 260&#xa0;nm. TDDFT calculations suggest that this band corresponds to a π–π* transition of the adenine ligand. The material shows fluorescence emission at 440&#xa0;nm in the solid state (λ<sub>ex</sub> = 330&#xa0;nm) and at 430&#xa0;nm when dispersed in methanol (λ<sub>ex</sub> = 350&#xa0;nm), consistent with intraligand transitions. CuAS acts as a selective fluorescent sensor for the nitrofuran antibiotics nitrofurantoin (NFT) and nitrofurazone (NFZ), exhibiting strong fluorescence quenching primarily driven by photoinduced electron transfer (PET). Stern–Volmer analysis revealed <i>K</i><sub>sv</sub> values of 5.98 × 10⁴ M⁻¹ (NFZ) and 5.88 × 10⁴ M⁻¹ (NFT), with detection limits of 0.136 ppm and 0.110 ppm, respectively. DFT and TDDFT calculations support the PET mechanism, indicating that π-stacked interactions between adenine and NFZ/NFT facilitate electron transfer upon excitation. In contrast, bulky antibiotics show minimal quenching, possibly due to steric hindrance impeding effective interaction. These findings provide molecular-level insights into the fluorescence sensing mechanism and establish CuAS as a promising selective sensor for nitrofuran antibiotics.</p>

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Structural and Mechanistic Insights into a Cu-Adenine MOF for Selective Fluorescence Sensing of Antibiotics: Experimental and TDDFT Approaches

  • 期刊论文

  • 发表日期：

    2025年7月7日

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  • Tanin Nanok,
  • Tontrakarn Pongpai,
  • Kittinan Ketsrisung,
  • Jiraporn Singhophon,
  • Kittipong Chainok,
  • Tanwawan Duangthongyou

摘要

An adenine–succinate-based metal–organic framework, [Cu(adenine)(succinate)]n (CuAS), was synthesized via a solvothermal method and structurally characterized by single-crystal X-ray diffraction, PXRD, IR spectroscopy, TGA, and elemental analysis. CuAS forms a three-dimensional framework featuring two directional channels along the a- and b-axes, with amino groups oriented toward the cavities. In methanol, CuAS exhibits a UV–Vis absorption maximum at 260 nm. TDDFT calculations suggest that this band corresponds to a π–π* transition of the adenine ligand. The material shows fluorescence emission at 440 nm in the solid state (λex = 330 nm) and at 430 nm when dispersed in methanol (λex = 350 nm), consistent with intraligand transitions. CuAS acts as a selective fluorescent sensor for the nitrofuran antibiotics nitrofurantoin (NFT) and nitrofurazone (NFZ), exhibiting strong fluorescence quenching primarily driven by photoinduced electron transfer (PET). Stern–Volmer analysis revealed Ksv values of 5.98 × 10⁴ M⁻¹ (NFZ) and 5.88 × 10⁴ M⁻¹ (NFT), with detection limits of 0.136 ppm and 0.110 ppm, respectively. DFT and TDDFT calculations support the PET mechanism, indicating that π-stacked interactions between adenine and NFZ/NFT facilitate electron transfer upon excitation. In contrast, bulky antibiotics show minimal quenching, possibly due to steric hindrance impeding effective interaction. These findings provide molecular-level insights into the fluorescence sensing mechanism and establish CuAS as a promising selective sensor for nitrofuran antibiotics.