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<p>Molecular materials showing synergetic coupling of near-infrared (NIR) fluorescence and spin-crossover (SCO) are promisingly applicable in <i>in-vivo</i> bioimaging, temperature sensing, and spintronic devices. Whilst the related study faces formidable challenges. In this work we graft the NIR fluorophore xanthene onto the dipyridyl substituted triazole ligand and construct a new Fe-based SCO material, {Fe<sup>II</sup>(ddxc-abpt)<sub>2</sub>[N(CN)<sub>2</sub>]<sub>2</sub>} (<b>1</b>, ddxc-abpt: (<i>E</i>)-4-(((3,5-di(pyridin-2-yl)-4<i>H</i>-1,2,4-triazol-4-yl)imino)methyl)-<i>N,N</i>-diethyl-2,3-dihydro-1<i>H</i>-xanthen-6-amine). Magnetic studies indicate that compound <b>1</b> exhibits thermally induced SCO property in both the solid and solution state. Variable-temperature fluorescence emission spectra reveal a remarkable 7-fold increase in photoluminescence intensity upon the transition from the low-spin state at 110 K to the high-spin state at 280 K, which is the record of all reported coupled fluorescence-SCO materials. Variable-temperature ultraviolet-visible (UV-Vis) absorption spectra show a significant change in absorption intensity within the fluorescence emission window, consistent with the Förster resonance energy transfer (FRET) mechanism. Time-dependent density functional theory (TD-DFT) calculations demonstrate that the strong coupling is attributed to disrupted energy transfer between the xanthene fluorophore and high-spin Fe<sup>II</sup> center. Our work provides a feasible approach for expanding the synergetic SCO-fluorescence materials to the NIR-I wavelength region, and hopefully contributes to the applications of tunable NIR-SCO molecule-based sensors and devices.</p>

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Spin-modulated near-infrared-I emission in a xanthene-decorated Fe(II) spin-crossover complex

  • 期刊论文

  • 发表日期：

    2025年1月13日

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  • Cheng Yi,
  • Duyong Chen,
  • Shi-Hui Zhang,
  • Rui Cai,
  • Chunying Duan,
  • Yin-Shan Meng,
  • Tao Liu

摘要

Molecular materials showing synergetic coupling of near-infrared (NIR) fluorescence and spin-crossover (SCO) are promisingly applicable in in-vivo bioimaging, temperature sensing, and spintronic devices. Whilst the related study faces formidable challenges. In this work we graft the NIR fluorophore xanthene onto the dipyridyl substituted triazole ligand and construct a new Fe-based SCO material, {FeII(ddxc-abpt)2[N(CN)2]2} (1, ddxc-abpt: (E)-4-(((3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)imino)methyl)-N,N-diethyl-2,3-dihydro-1H-xanthen-6-amine). Magnetic studies indicate that compound 1 exhibits thermally induced SCO property in both the solid and solution state. Variable-temperature fluorescence emission spectra reveal a remarkable 7-fold increase in photoluminescence intensity upon the transition from the low-spin state at 110 K to the high-spin state at 280 K, which is the record of all reported coupled fluorescence-SCO materials. Variable-temperature ultraviolet-visible (UV-Vis) absorption spectra show a significant change in absorption intensity within the fluorescence emission window, consistent with the Förster resonance energy transfer (FRET) mechanism. Time-dependent density functional theory (TD-DFT) calculations demonstrate that the strong coupling is attributed to disrupted energy transfer between the xanthene fluorophore and high-spin FeII center. Our work provides a feasible approach for expanding the synergetic SCO-fluorescence materials to the NIR-I wavelength region, and hopefully contributes to the applications of tunable NIR-SCO molecule-based sensors and devices.