Near-Infrared Emitting Heterobimetallic Zn-4f Schiff Base Complexes with Visible Excitation Wavelength
Résumé
Herein, we report the synthesis and characterization of heterobimetallic Zn‐4f complexes formed by the “valnap” ligand (L1) with extended aromaticity, thereby acting as visibly absorbing antenna for generating the near‐infrared (NIR) luminescence of three different lanthanide(III) ions (Ln3+). The series of new Zn(py)L1Ln(NO3)3 complexes [Ln = Yb (1), Nd (2), Er (3)] have been characterized by single‐crystal X‐ray diffraction and were found to be isotypic, with a variation in the Ln3+ coordination number (CN = 9–11) in line with increasing atomic radius. Absorption spectra recorded for L1, ZnL1, and complexes 1–3 display ligand‐based absorption bands in the UV (λmax ≈ 320 nm) and visible regions (λmax ≈ 430 nm) with molar absorption coefficients up to 6.3 × 104 and 3.9 × 104 m–1 cm–1, respectively. Upon excitation into ligand‐centered absorption bands in the visible range, characteristic NIR emission signals of Yb3+ (1), Nd3+ (2), and Er3+ (3) have been obtained. Quantum yields measured under visible excitation at 430 nm (QLnL) and observed luminescence lifetimes (τobs) reflecting the excited states attributed to the 2F5/2 (Yb3+), 4F3/2 (Nd3+) and 4I13/2 (Er3+) levels have been determined. These data quantifying the luminescence properties of this family of complexes and absorption bands in the visible range with large molar absorption coefficients make complexes 1–3 of potential interest for biological applications where UV light is inappropriate.
Domaines
Sciences du Vivant [q-bio]
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