Issue 6, 2019

Syntheses, crystal structures and magnetic properties of a series of luminescent lanthanide complexes containing neutral tetradentate phenanthroline-amide ligands

Abstract

A series of lanthanide (Ln) compounds, [EuIII(L)2(MeOH)(H2O)](ClO4)3 (1), [TbIII(L)2(H2O)](Cl3) (2) and [MIII(L)2(NO3)](ClO4)2 (M = Eu (3); Sm (4); Tb (5); Dy (6)), have been prepared by the treatment of a neutral tetra-dentate ligand (N2,N9-dibutyl-1,10-phenanthroline-2,9-dicarboxamide, L) with various Ln(III) salts in MeOH. All of the compounds have been structurally characterized by X-ray crystallography. It is noted that the anions of the Ln(III) salts play crucial roles in the solid-state structures and the properties of the resulting complexes. In compounds 1 and 2, the metal centres are 10- and 9-coordinated, respectively, which are surrounded by two L ligands and solvent molecules. When the nitrate salts are used instead, four isostructural 10-coordinate Ln(III) compounds are obtained. The photophysical properties show that most of the compounds exhibit the characteristic emission peaks of Ln(III). Ligand L acts as a very good ‘antenna’ to sensitize the Eu(III) emission, but not for other Ln(III) emissions. The quantum yield of 3 is 75.4%, which is much higher than that of 1 (17.6%) due to the –OH oscillators of the coordinated H2O and MeOH molecules in 1. The magnetic properties of the Tb(III) compounds 2 and 5 and the Dy(III) compound 6 were investigated in detail as a natural extension of our previous study of the effect of high-coordination number on the single-ion magnet (SIM) behaviour of 3d compounds. The results show that subtle changes in the coordination environment have significant effects on the magnetic behaviour. The 9-coordinate compound 2 is not a single ion magnet (SIM), but both 10-coordinate compounds 5 and 6 exhibit field-induced SIM behaviour. It is also interesting to note that, upon the application of a small dc field, 5 exhibits two distinct relaxation processes, which is uncommon in Ln-based SIMs.

Graphical abstract: Syntheses, crystal structures and magnetic properties of a series of luminescent lanthanide complexes containing neutral tetradentate phenanthroline-amide ligands

Supplementary files

Article information

Article type
Research Article
Submitted
12 Mar 2019
Accepted
11 Apr 2019
First published
12 Apr 2019

Inorg. Chem. Front., 2019,6, 1442-1452

Syntheses, crystal structures and magnetic properties of a series of luminescent lanthanide complexes containing neutral tetradentate phenanthroline-amide ligands

Q. Su, K. Fan, X. Jin, X. Huang, S. Cheng, L. Luo, Y. Li, J. Xiang, C. Ko, L. Zheng and T. Lau, Inorg. Chem. Front., 2019, 6, 1442 DOI: 10.1039/C9QI00238C

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