# Supramolecular Binding and Extraction of Phosphate, Phosphite and Fluorophosphate Anions from Water by Nanojars

## TL;DR

This paper explores how nanojars can bind and extract specific phosphate and fluorophosphate anions from water, using a combination of spectroscopic and structural techniques.

## Contribution

The study introduces nanojars as effective supramolecular hosts for selective anion extraction and reveals their structural and magnetic properties.

## Key findings

- Nanojars selectively bind HPO4²⁻, HPO3²⁻, and FPO3²⁻ anions with distinct structural and magnetic behaviors.
- X-ray diffraction and NMR spectroscopy reveal detailed host-guest interactions and solution structures.
- Nanojars successfully extract target anions from water into organic solvents via liquid-liquid extraction.

## Abstract

In this work, the
supramolecular binding of HPO4
2–, HPO3
2– and FPO3
2– ions by nanojars of the general formula
[XPO3
2–⊂{cis-CuII(μ-OH)­(μ-pz)}
n
]2– (Cu

n

XPO

3
; X = HO, H, F; n = 27–33; pz = pyrazolate) was explored. The nanojar
hosts, which consist of stacks of three Cu
x
(x = 6–14, except 11) metallamacrocycles,
were studied in solution by electrospray-ionization mass spectrometry,
variable-temperature, paramagnetic 1H NMR and UV–vis
spectroscopy, whereas the entrapped anion was probed using 19F and 31P NMR spectroscopy. In the solid state, X-ray
diffraction on nine different single-crystals offers valuable information
about the structure of the host–guest complexes (Cu

7+13+9

HPO

4
, Cu

8+13+8

HPO

4
, Cu

8+13+8

HPO

3
, and three pseudopolymorphs
each for Cu

8+14+9

HPO

3
and Cu

8+14+9

FPO

3
) and details of the
supramolecular binding of the different phosphorus anions. Multinuclear
NMR studies reveal that the different XPO3
2– ions induce dramatic changes in the magnetism of a given nanojar,
despite a less striking difference observed in their respective crystal
structure, pointing to significantly different solution structures.
The formation of HPO3
2– and HPO4
2– nanojars by anion exchange from CO3
2– was also studied, along with the effects of
NH3 and Ba2+ ions on nanojar composition and
thermal stability in solution. Furthermore, the liquid–liquid
extraction of the HPO4
2–, HPO3
2– and FPO3
2– anions
from water into an organic solvent was demonstrated using nanojars
as extractants.