A Systematic Study of the Optical Properties of Mononuclear Hybrid Organo-Inorganic Lanthanoid Complexes

A series of hybrid organo-inorganic mononuclear lanthanoid complexes, [n-NBu4]3[LnH(PW11O39)(phen)2]·H2O, denoted as LM4-1-Ln (Ln = DyIII, TbIII, EuIII, NdIII, ErIII, HoIII and GdIII), were synthesized via hydrothermal synthesis and were structurally characterized by X-ray diffraction. The optical properties of all complexes have been investigated in the solid state. The temperature-dependent emission spectra of LM4-1-Dy, LM4-1-Tb and LM4-1-Eu complexes show intense lanthanoid emissions in the visible region, while LM4-1-Nd shows near-infrared (NIR) luminescence. The EuIII complex shows typical strong red emissions from the 5D0 ? 7F0,1,2,3,4 transitions, with the CIE colour coordinates (0.631,0.364), the colour purity value of 83.9% and a quantum yield of up to 4.3%, suggesting that the organic fragment has an effect on the optical properties compared to fully inorganic systems, making this complex very attractive as a red component of light-emitting diodes. The luminescence decays of LM4-1-Dy, LM4-1-Tb and LM4-1-Eu exhibit a biexponential behaviour, with tAV = 4.1(7) µs, 0.35(2) ms and 0.94(3) ms, respectively. The values obtained for Judd-Ofelt intensity parameters O2 and O4 support the interaction between the EuIII and the ligands. Furthermore, those with ErIII and HoIII present weak emissions in the visible region. The T-dependent photoluminescence results show that the LM4-1-Dy, LM4-1-Tb and LM4-1-Nd complexes have good temperature sensitivity, demonstrating that the materials have the potential to be used as a sensing element for luminescent thermometers in different temperature ranges. © 2020 the Partner Organisations.