Synthesis, Crystal Structures and Photoluminescent Properties of One-Dimensional Europium(III)- and Terbium(III)-Glutarate Coordination Polymers, and Their Applications for the Sensing of Fe3+ and Nitroaromatics

Sajjad Hussain,William T A Harrison,David Awoyelu,Saeed Ahmad,Shujun Li,Xuenian Chen,Shabbir Muhammad,Mark R J Elsegood

doi:10.3389/fchem.2019.00728

Abstract

Two lanthanide–glutarate coordination polymers, viz. : {[Eu(C5H6O4)(H2O)4]Cl}n, (1) and [Tb(C5H7O4)(C5H6O4)(H2O)2]n, (2) have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and X-ray crystallography. In 1, the Eu(III) ions are coordinated by four O atoms from two bidentate chelating carboxylate groups, one O atom from a bridging carboxylate group and four O atoms from water molecules adopting an EuO9 distorted tri-capped trigonal prismatic coordination geometry. In 2, the Tb(III) ions are coordinated by six O atoms from three bidentate chelating carboxylates, one O atom from a bridging carboxylate and two O atoms from water molecules to generate distorted tri-capped trigonal prismatic TbO9 polyhedron. In both compounds, the metal polyhedra share edges, producing centrosymmetric Ln2O2 diamonds, and are linked into [001] chains by bridging glutarate di-anions. The crystal structures are consolidated by O–H···O and O–H···Cl hydrogen bonds in 1, and O–H···O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the 5D0 → 7FJ (J = 1–4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the 5D4 → 7FJ (J = 0–6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe3+ ions due to luminescence quenching compared with other metal ions, which include; Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+. Compounds 1 and 2 also show high luminescence quenching sensitivity for 4-nitrophenol over the other aromatic and nitroaromatic compounds, namely; bromobenzene, 1,3-dimethylbenzene, nitrobenzene, 4-nitrotolune, 4-nitrophenol, 2,6-dinitrophenol and 2,4,6-trinitrophenol.

Highlights

To further explore the luminescent behavior of such complexes and as a part of our ongoing research on lanthanide complexes (Hussain et al, 2014, 2015a,b, 2018, 2019) we report the structural characterization and photoluminescent properties of two one-dimensional Eu(III) and Tb(III) coordination polymers based on the glutarate ligand
In the preparation of complex 1, where more amount of NaOH was added as base, the ligand was fully deprotonated to produce glutarate di-anions, while in case of 2, the lower pH resulted in the partial deprotonatation of the ligand and produced hydrogen-glutarate anion (HGlut−)
The compounds exhibited good luminescence in various solvents except dichloromethane and acetone. Both complexes exhibit a strong quenching effect on emission intensity when brought into contact with Fe3+ ions and 4-nitrophenol as compared with the other metal ions and nitroaromatics

Summary

INTRODUCTION

Lanthanide coordination compounds have attracted great interest from the scientific community in the last two decades due to their potential as an emerging type of multifunctional luminescent materials in areas such as telecommunications, optical amplifiers, immunoassays, and sensors (Werts, 2005; Binnemans, 2009; Armelao et al, 2010; Bünzli, 2010, 2015; Zhang et al, 2010; Azab et al, 2013; Feng and Zhang, 2013; Heffern et al, 2013; Xiang et al, 2017). Choosing appropriate ligands to increase the excited state lifetime and quantum yield (the light output) of lanthanide(III) complexes is essential for the development of improved luminescent materials (Li and Yan, 2012) In this regard, aromatic carboxylic acids such as, terephthalic acid (Daiguebonne et al, 2008; Wang et al, 2012) benzene-carboxylic acids (Yan et al, 2005; Wang et al, 2010b, 2012; Zhuravlev et al, 2011; Gai et al, 2013), and pyridine-dicarboxylic acid (Reinhard and Güdel, 2002; Huang et al, 2008; Zhu et al, 2009; Song et al, 2016; Xiang et al, 2017; Kumar et al, 2018) have been used to design luminescent lanthanide coordination polymers. 2 was assessed by the gradual addition (10–250 μL) of 4-nitrophenol (0.001 M in ethanol) to 0.5 mg of 2 suspended in 3 mL of methanol

RESULTS AND DISCUSSION

CONCLUSIONS

DATA AVAILABILITY STATEMENT