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<p>Three new Co(II) (<b>1</b>), Ni(II) (<b>2</b>), and Cu(II) (<b>3</b>) binuclear complexes with versatile azide bridges and Schiff base derived from 2-hydroxy-1-naphthaldehyde and 2-aminothiophenol have been synthesized. Compounds <b>1</b>–<b>3</b> were characterized using various techniques, including microanalysis (CHNS), molar conductance, FTIR, UV–visible, 1H-NMR, mass spec, photoluminescence (PL) spectroscopy, thermogravimetric analysis (TGA-DTG), scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX) techniques. Molar conductance values of the newly synthesized complexes indicate that the complexes are electrolytes in solution. Spectroscopic results suggest that the Schiff base acts as a tridentate ligand, bonding to the metal using imino nitrogen, thiol sulphur, and hydroxy oxygen atoms. Upon the incorporation of the azide pseudohalide, the <i>µ -1, 1</i> bridge are proposed for all the complexes. Electronic spectra of <b>1</b>–<b>3</b> suggest an octahedral environment around the metal ions. Schiff base exhibited fluorescence originating from intra-ligand (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\varvec{\pi}}\to {{\varvec{\pi}}}^{\boldsymbol{*}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mi mathvariant="bold-italic">π</mi> </mrow> <mo stretchy="false">→</mo> <msup> <mrow> <mrow> <mi mathvariant="bold-italic">π</mi> </mrow> </mrow> <mrow> <mrow /> <mo mathvariant="bold">∗</mo> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation>) transitions with a quantum yield value of (9 ± 1) %, while the metal complexes exhibited reduced photoluminescence intensity and quantum yield (0.5 – 3.80%) relative to the Schiff base. These results suggest that the Schiff base has a specific recognition for transition metals. It can be used as a <i>turn-off</i> fluorescence sensor specifically for Cu<sup>2+</sup> ions with a fluorescence quenching efficiency of (94 ± 2) %.</p>

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Synthesis, Characterization, and Photoluminescence Properties of Binuclear Co(ll), Ni(ll) and Cu(ll) Schiff Base Complexes with μ -1, 1 Azide Bridges

  • 期刊论文

  • 发表日期：

    2025年6月16日

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  • Jocelyn N. Kuate,
  • Maurice Kuate,
  • Awawou G. Paboudam,
  • Adrien P. Yepseu,
  • Viorel Cîrcu,
  • Sunder N. Dhuri,
  • Peter T. Ndifon

摘要

Three new Co(II) (1), Ni(II) (2), and Cu(II) (3) binuclear complexes with versatile azide bridges and Schiff base derived from 2-hydroxy-1-naphthaldehyde and 2-aminothiophenol have been synthesized. Compounds 1–3 were characterized using various techniques, including microanalysis (CHNS), molar conductance, FTIR, UV–visible, 1H-NMR, mass spec, photoluminescence (PL) spectroscopy, thermogravimetric analysis (TGA-DTG), scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX) techniques. Molar conductance values of the newly synthesized complexes indicate that the complexes are electrolytes in solution. Spectroscopic results suggest that the Schiff base acts as a tridentate ligand, bonding to the metal using imino nitrogen, thiol sulphur, and hydroxy oxygen atoms. Upon the incorporation of the azide pseudohalide, the µ -1, 1 bridge are proposed for all the complexes. Electronic spectra of 1–3 suggest an octahedral environment around the metal ions. Schiff base exhibited fluorescence originating from intra-ligand ( \({\varvec{\pi}}\to {{\varvec{\pi}}}^{\boldsymbol{*}}\) π → π ∗ ) transitions with a quantum yield value of (9 ± 1) %, while the metal complexes exhibited reduced photoluminescence intensity and quantum yield (0.5 – 3.80%) relative to the Schiff base. These results suggest that the Schiff base has a specific recognition for transition metals. It can be used as a turn-off fluorescence sensor specifically for Cu2+ ions with a fluorescence quenching efficiency of (94 ± 2) %.