Mechanistic Insight of Sensing Hydrogen Phosphate in Aqueous Medium by Using Lanthanide(III)-Based Luminescent Probes

Jashobanta Sahoo; Santlal Jaiswar; Pabitra B Chatterjee; Palani S Subramanian; Himanshu Sekhar Jena

doi:10.3390/nano11010053

Mechanistic Insight of Sensing Hydrogen Phosphate in Aqueous Medium by Using Lanthanide(III)-Based Luminescent Probes

Nanomaterials (Basel). 2020 Dec 28;11(1):53. doi: 10.3390/nano11010053.

Authors

Jashobanta Sahoo^{1

2

3}, Santlal Jaiswar⁴, Pabitra B Chatterjee^{2

5}, Palani S Subramanian^{1

2}, Himanshu Sekhar Jena⁶

Affiliations

¹ Inorganic Materials and Catalysis Division, Central Salt and Marine Chemicals Research Institute (CSIR-CSMCRI), Bhavnagar, Gujarat 364 002, India.
² Academy of Scientific and Innovative Research (AcSIR), CSIR-CSMCRI, Bhavnagar, Gujarat 364 002, India.
³ Department of Chemistry, Hindol College, Khajuriakata, Higher Education Department, State Government of Odisha, Bhubaneswar, Odisha 751001, India.
⁴ Discipline of Marine Biotechnology and Ecology, CSIR-CSMCRI, Bhavnagar, Gujarat 364 002, India.
⁵ Analytical Discipline and Centralized Instrument Facility, CSIR-CSMCRI, Bhavnagar, Gujarat 364 002, India.
⁶ Department of Chemistry, Ghent University, Krijgslaan 281-S3 B, 9000 Ghent, Belgium.

Abstract

The development of synthetic lanthanide luminescent probes for selective sensing or binding anions in aqueous medium requires an understanding of how these anions interact with synthetic lanthanide probes. Synthetic lanthanide probes designed to differentiate anions in aqueous medium could underpin exciting new sensing tools for biomedical research and drug discovery. In this direction, we present three mononuclear lanthanide-based complexes, EuLCl₃ (1), SmLCl₃ (2), and TbLCl₃ (3), incorporating a hexadentate aminomethylpiperidine-based nitrogen-rich heterocyclic ligand L for sensing anion and establishing mechanistic insight on their binding activities in aqueous medium. All these complexes are meticulously studied for their preferential selectivities towards different anions such as HPO₄^2-, SO₄^2-, CH₃COO^-, I^-, Br^-, Cl^-, F^-, NO₃^-, CO₃^2-/HCO₃^-, and HSO₄^- at pH 7.4 in aqueous HEPES (2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid) buffer. Among the anions scanned, HPO₄^2- showed an excellent luminescence change with all three complexes. Job's plot and ESI-MS support the 1:2 association between the receptors and HPO₄^2-. Systematic spectrophotometric titrations of 1-3 against HPO₄^2- demonstrates that the emission intensities of 1 and 2 were enhanced slightly upon the addition of HPO₄^2- in the range 0.01-1 equiv and 0.01-2 equiv., respectively. Among the three complexes, complex 3 showed a steady quenching of luminescence throughout the titration of hydrogen phosphate. The lower and higher detection limits of HPO₄^2- by complexes 1 and 2 were determined as 0.1-4 mM and 0.4-3.2 mM, respectively, while complex 3 covered 0.2-100 μM. This concludes that all complexes demonstrated a high degree of sensitivity and selectivity towards HPO₄^2-.

Keywords: lanthanides; luminescence; nitrogen-rich ligand; phosphate sensing; quenching.

Abstract

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