Asymmetric Schiff base ligand enables synthesis of fluorescent and near-IR emitting lanthanide compounds

Abstract

In this paper, the HYDRAVH2 ligand as an asymmetric fluorescence Schiff base ligand was used to produce a series of new lanthanide complexes (HYDRAV-Ln(III), Ln: Yb, Er, Gd and Dy). The structures of the Schiff base complexes are characterized using Fourier transform infrared spectroscopy (FT-IR), MALDI-TOF mass spectrometry, CHN elemental analysis, Ultraviolet-Visible (UV-Vis), fluorescence, near-infrared (NIR) and thermogravimetric analysis (TGA). The photoluminescence properties show that the energy transfer from HYDRAVH2 to Ln(III) ions is effective and the energy levels of HYDRAVH2 and Ln(III) ions match well, therefore the Ln-compounds exhibit emission in the visible region. The result of the photophysical properties of HYDRAV-Ln(III) also indicates that strong and characteristic Near-IR luminescence for HYDRAV-Yb and HYDRAV-Er are observed, which are attributed to the antenna effect of the HYDRAVH2 ligands that harvest the light and transfer it to the metal centers. Based on the above results, the ligand and its complexes (HYDRAV-Ln(III)) have remarkable optical features that could be of great utility in optoelectronic devices.