Five Dinuclear Lanthanide Complexes Based on 2,4-dimethylbenzoic Acid and 5,5'-dimethy-2,2'-bipyridine: Crystal Structures, Thermal Behaviour and Luminescent Property.

Jia-Yuan Zhao,Kun Tang,Jian-Jun Zhang,Ying-Ying Zhang,Ning Ren

doi:10.3389/fchem.2021.726813

Abstract

A series of new complexes, [Ln (2,4-DMBA)3(5,5′-DM-2,2′-bipy)]2 (Ln = Sm(1), Eu (2)), [Pr (2,4-DMBA)3 (5,5′-DM-2,2′-bipy)]2·0.5(C2H5OH) (3), [Ln (2,4-DMBA)3 (5,5′-DM-2,2′-bipy)]2·0.5(2,4-DMBAH)·0.25(5,5′-DM-2,2′-bipy) (Ln = Tb (4), Dy (5)) (2,4-DMBA = 2,4-dimethylbenzoate, 5,5′-DM-2,2′-bipy = 5,5′-dimethy-2,2′-bipyridine) were synthesized via hydrothermal reaction conditions. The complexes were characterized through elemental analysis, Infrared spectra (IR), Raman (R) spectra, UV-Vis spectra, single X-ray diffraction. Single crystal data show that complexes 1–5 are binuclear complexes, but they can be divided into three different crystal structures. The thermal decomposition mechanism of complexes 1–5 were investigated by the technology of simultaneous TG/DSC-FTIR. What’s more, the luminescent properties of complexes 1–2 and 4 were discussed, and the luminescence lifetime (τ) of complexes 2 and 4 were calculated.

Highlights

In recent years, the synthesis and construction of metal complexes and supramolecular complexes have attracted extensive attention (Feng et al, 2010)
Lanthanide ions have unique 4f electronic structure, which leads to long luminescence lifetimes, narrow luminescence emission peaks and large Stokes shifts (Zheng et al, 2019)
Lanthanide ions as metal center ions have the advantages of large radius, high coordination number and diverse coordination environment (Soek et al, 2019)

Summary

INTRODUCTION

The synthesis and construction of metal complexes and supramolecular complexes have attracted extensive attention (Feng et al, 2010). Lanthanide ions with special electronic structure are preferred in the selection of metal ions, which makes the complexes have excellent optical properties and can be used in the fields of luminescent materials, biological imaging, biological response probes and sensors (Liu et al, 2014a; Abbas et al, 2017; Gu et al, 2018). The introduction of aromatic carboxylic acid ligands can sensitize the fluorescence of lanthanide ions. It is well known that the antenna effect is a popular method to improve the luminescent properties of lanthanide elements. It includes the effective absorption of incident light through organic chromophores and the corresponding sensitization of lanthanide metal ions through ligand to metal energy transfer (Ahmed and Iftikhar, 2010; Fomina et al, 2012; Carter et al, 2016). The disorder solvent molecule for complex 2 is interpreted as two water molecules

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT