Pyrene aggregation at unprecedented low concentrations in (lanthanide metal salt + urea) deep eutectic solvents

Khokhar, Vaishali; Kumar, Manish; Pandey, Siddharth

doi:10.1039/d2cp05155a

Cited by 4 publications

(2 citation statements)

References 23 publications

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“…Herein, we report our findings of exceptionally high probe-reported polarity exhibited by a set of type IV DESs constituted of hydrated lanthanide metal salts as HBA and urea as prototypical HBD [14]. These DESs have recently shown to support probe aggregation at unprecedented low concentrations [20]. Specifically, three (3) HBD urea-based DESs containing HBA metal salts lanthanum nitrate hexahydrate (La : U), cerium nitrate hexahydrate (Ce : U), and gadolinium nitrate hexahydrate (Gd : U), respectively, are found to exhibit some of the highest probereported polarities in terms of empirical Kamlet-Taft parameters of dipolarity/polarizability (π*) [21] and HBD acidity (α) [22] along with ET values [22].…”

Section: Introductionmentioning

confidence: 91%

Unprecedented High Probe-Reported Polarity of Deep Eutectic Solvents Composed of Lanthanide Salts and Urea

Patra,

Khokhar,

Pandey

2024

Preprint

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Deep eutectic solvents (DESs) have emerged as viable alternatives to the toxic organic solvents. The most intriguing aspect of these solvents is perhaps the widely varying physicochemical properties emerging from the changes in the constituents that form DESs along with their composition. Based on the constituents, a DES can be hydro-philic/polar or hydrophobic/non-polar rendering vastly varying spectrum of polarity a possibility. DESs formed by mixing urea (U) with hydrated lanthanide salts, lanthanum nitrate hexahydrate (La : U), cerium nitrate hexahydrate (Ce : U), and gadolinium nitrate hexahydrate (Gd : U), respectively, exhibit very high polarity as manifested via probe-reported empirical parameters dipolarity/polarizability (π*). The highest π* of 1.70 exhibited by the DES (Gd : U) in 1 : 2 molar ratio is unprecedented. The π* ranges from 1.50 to 1.70 for these DESs, which is almost the highest reported for any solvent system. The π* decreases with increasing urea in the DES, however, the anomalous trends in H-bond donating acidity (α) and H-bond accepting basicity (β) appear to be due to the hydrated water of the lanthanide salt. The emission band maxima of fluo-rescence probe of “effective” dielectric constant (εeff) of the solubilizing media, py-rene-1-carboxaldehyde (PyCHO), in salt-rich DESs reflect higher cybotactic region di-polarity than even that offered by water. Probe Nile red aggregates readily in these DESs to form non-fluorescent H-aggregates; a characteristic of highly polar solvents. Behavior of probe pyranine also corroborates these outcomes as the (lanthanide salt : urea) DES system supports the formation of deprotonated form of the probe in the excited-state. The (lanthanide salt : urea) DES system offers solubilizing media of exceptionally high polarity, which is bound to expand their application potential.

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Section: Introductionmentioning

confidence: 91%

Unprecedented High Probe-Reported Polarity of Deep Eutectic Solvents Composed of Lanthanide Salts and Urea

Patra,

Khokhar,

Pandey

2024

Preprint

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“…More recently, Pandey et al observed that pyrene exhibits an intermolecular excimer at low concentrations (20 mM) in deep eutectic solvents constituted of hydrated lanthanide salts and urea. 75 Thus, spectroscopic analysis is the preferred analytical technique to identify the aggregation behaviour of pyrene-based luminogens.…”

Section: The Aggregation Behaviour Of Pyrene-based Emitters In Solutionmentioning

confidence: 99%

Aggregation behaviour of pyrene-based luminescent materials, from molecular design and optical properties to application

Feng,

Wang,

Redshaw

et al. 2023

Chem. Soc. Rev.

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Unprecedented High Probe-Reported Polarity of Deep Eutectic Solvents Composed of Lanthanide Salts and Urea

Patra,

Khokhar,

Pandey

2024

Liquids

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Deep eutectic solvents (DESs) have emerged as viable alternatives to toxic organic solvents. The most intriguing aspect of these solvents is perhaps the widely varying physicochemical properties emerging from the changes in the constituents that form DESs along with their composition. Based on the constituents, a DES can be hydrophilic/polar or hydrophobic/non-polar, rendering a vastly varying spectrum of polarity a possibility. DESs formed by mixing urea (U) with hydrated lanthanide salts, lanthanum nitrate hexahydrate (La : U), cerium nitrate hexahydrate (Ce : U), and gadolinium nitrate hexahydrate (Gd : U), respectively, exhibit very high polarity as manifested via the probe-reported empirical parameters of dipolarity/polarizability (π*). The highest π* of 1.70 exhibited by the DES (Gd : U) in a 1 : 2 molar ratio is unprecedented. The π* ranges from 1.50 to 1.70 for these DESs, which is almost the highest reported for any solvent system. The π* decreases with an increasing amount of urea in the DES; however, the anomalous trends in H-bond donating acidity (α) and H-bond accepting basicity (β) appear to be due to the hydrated water of the lanthanide salt. The emission band maxima of the fluorescence probe of the “effective” dielectric constant (εeff) of the solubilizing media, pyrene-1-carboxaldehyde (PyCHO), in salt-rich DESs reflect higher cybotactic region dipolarity than that offered by water. Probe Nile red aggregates readily in these DESs to form non-fluorescent H-aggregates, which is a characteristic of highly polar solvents. The behavior of probe pyranine also corroborates these outcomes as the (lanthanide salt : urea) DES system supports the formation of the deprotonated form of the probe in the excited state. The (lanthanide salt : urea) DES system offers solubilizing media of exceptionally high polarity, which is bound to expand their application potential.

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Pyrene aggregation at unprecedented low concentrations in (lanthanide metal salt + urea) deep eutectic solvents

Abstract: We report intermolecular excimer formation by a common and popular polycyclic aromatic hydrocarbon pyrene at very low concentrations (low µM) when dissolved in deep eutectic solvents constituted of hydrated lanthanide...

Cited by 4 publications

References 23 publications

Unprecedented High Probe-Reported Polarity of Deep Eutectic Solvents Composed of Lanthanide Salts and Urea

Unprecedented High Probe-Reported Polarity of Deep Eutectic Solvents Composed of Lanthanide Salts and Urea

Aggregation behaviour of pyrene-based luminescent materials, from molecular design and optical properties to application

Unprecedented High Probe-Reported Polarity of Deep Eutectic Solvents Composed of Lanthanide Salts and Urea

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