Synthesis, Characterization And Properties Of Lanthanide Luminescent Complexes Containing 4-Pyridinyl Terpyridine Derivatives Ligands

As a result of their unique photonic properties and variantmolecular structures, the lanthanide luminescent complexes containing the terpyridine ligand are widely applied in the industrial, agricultural and military fields. In order to enrich the class of the rare earth luminescent complexes and to construct lanthanide coordination complexes with excellent photophysical properties, two known compounds of 4’-(N-benzyl-4-pyridine)-2,2’:6’,2"-terpyridine (L1) and 4’,4"-(1,4-bis (N-benzyl-4-pyridine)benzene)-bis(2,2’:6’,2"-terpyridine)(L2) and two new compounds of 4’-(N-benzyl methyl-4-pyridine)-2,2’:6’,2"-terpyridine (L3) and 4’-(N-benzyl nitro-4-pyridine)-2,2’:6’,2"-terpyridine (L4) were synthesized. Then,28 new lanthanide luminescent complexes were obtained by reactions of the four ligands (L1, L2, L3, L4) with the rare earth nitrate salts, respectively. All of them were characterized by elemental analysis, IR,1H NMR, MS and thermal gravimetric analysis. The luminescent properties of these complexes were also investigated by UV-vis, fluorescence spectroscopy and phosphorescence spectral.First of all,21 mononuclear lanthanide complexes [Ln(L1)(NO3)3·xH2O] (Ln=Sm 1a, Eu 1b, Tb lc, Dy 1d, Nd le, Yb If, Er 1g), [Ln(L3)(NO3)3·xH2O] (Ln=Sm 3a, Eu 3b, Tb 3c, Dy 3d, Nd 3e, Yb 3f, Er 3g), [Ln(L4)(NO3)3·xH2O] (Ln=Sm 4a, Eu 4b, Tb 4c, Dy 4d, Nd 4e, Yb 4f, Er 4g) were obtained by reactions of L1, L3, L4 with Ln(NO3)3·xH2O under the ratio of 1:1. The fluorescence spectroscopies of these complexes reveal that L1 and L3 can sensitize the luminescence of Sm3+、Eu3+、Tb3+、Dy3+in the visible region and Nd3+、Yb3+and Er3+ in the NIR region. While the ligand L4 can sensitize the luminescence of Sm3+、Eu3+、 Tb3+、Dy3+inthe visible region and Nd3+and Yb3+in the NIR region.Furthermore, the reactions of symmetrical bisterpyridine L2 with Ln(NO3)3·xH2O at a ratio of 1:2, affording seven bimetallic complexes [Ln2(L2)(NO3)6] (Ln=Sm2a, Eu2b, Tb2c, Dy2d, Nd2e, Yb2f, Er2g). The fluorescence spectroscopies of the complexes demonstrate that L2 can sensitize the luminescence of Sm3+、Eu3+、Tb3+and Nd3+. The phosphorescence spectrals of Gd-L1 complexes provide the theoretical basis on the energy transfer of the ligand L1.Finally, the discussion on the luminescent intensity, fluorescent lifetime and quantum yields of the four different series compounds were carried out from the viewpoint of structures of L1-L4 and their energy transfer efficiency. The compound Eu-L3 shows long fluorescent lifetimeabout 1.75 millisecondsand the quantum yields reach 51.96%, which has significant values on the preparation of photo-luminescent materials.