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Kumar M, Pandey S. n-Perfluorooctane versus n-Octane: Pyrene Fluorescence to Compare and Contrast Solute Solvation. J Phys Chem B 2024. [PMID: 39129264 DOI: 10.1021/acs.jpcb.4c03854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/13/2024]
Abstract
Fluorous solvents may offer distinctly different solvation environments to a solute compared to their hydrocarbon analogues due to the inherently high electronegativity associated with fluorine. Solute solvation within n-perfluorooctane (PFO) is compared with that in n-octane using the well-established polycyclic aromatic hydrocarbon (PAH) fluorescence probe pyrene in the temperature range of 288 to 318 K. Both density (ρ) and dynamic viscosity (η) of PFO are considerably higher than those of n-octane. UV-vis molecular absorbance, fluorescence emission/excitation, and excited-state emission intensity decay reveal the cybotactic region of pyrene to be more nonpolar in PFO than that in n-octane. Bimolecular quenching rate constants (kq) for the pyrene-nitrobenzene fluorophore-quencher pair adhere to the Stokes-Einstein formulation; however, they are considerably higher than the estimated rate constants for the diffusion-controlled process (kdiff). This is due to the high electron affinity of nitrobenzene leading to aromatic π-π interactions between pyrene and nitrobenzene. For a nonaromatic low electron affinity quencher, such as nitromethane, while kq < kdiff in n-octane, kq > kdiff in PFO. This is due to the fact that highly electronegative fluorines on PFO stabilize the partial positive charge (δ+) that develops on excited pyrene during electron/charge transfer to the quencher nitromethane, facilitating quenching in the process. Exciplex formation between pyrene and triethylamine (TEA) is more favored in PFO as opposed to n-octane although ηPFO > ηn-octane. The developing charge on the exciplex is stabilized by the electronegative fluorines of the PFO. The pyrene-TEA exciplex appears to form exclusively in the excited state of pyrene, and the kinetics of exciplex formation is in the subnanosecond regime. On the contrary, the efficiency of exciplex formation between pyrene and N,N-dimethylaniline (DMA) is comparable in PFO and n-octane, and the kinetics is slower in comparison to that of the pyrene-TEA exciplex. Certain ground-state heterogeneity is detected for the pyrene-DMA system in PFO due to the low solubilizing ability of the fluorous solvent. Highly electronegative fluorines on perfluorohydrocarbon solvents are found to offer unusual and unique solvation characteristics.
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Affiliation(s)
- Manish Kumar
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Siddharth Pandey
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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Kumar M, Anjali, Dhingra D, Yadav A, Pandey S. Effect of lithium salt on fluorescence quenching in glycerol: a comparison with ionic liquid/deep eutectic solvent. Phys Chem Chem Phys 2021; 24:459-467. [PMID: 34897318 DOI: 10.1039/d1cp03678e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It was reported earlier that the addition of LiCl to the deep eutectic solvent (DES) ChCl:Urea (composed of the salt choline chloride and the H-bond donor urea in 1 : 2 molar ratio) and the addition of LiTf2N [Tf2N:(CF3SO2)2N] to the ionic liquid (IL) [C2C1im][Tf2N] ([C2C1im]:1-ethyl-3-methylimidazolium), respectively, results in an increase in the dynamic viscosity of the medium. However, as the concentration of the Li salt is increased, instead of decreasing, the bimolecular quenching rate constant (kq) for the quenching of pyrene fluorescence by nitromethane is observed to first increase and only then decreases within both media. This unusual initial increase in quenching is hypothesized to be due to structural changes in the DES ChCl:Urea and the IL [C2C1im][Tf2N], respectively, as the Li salt is added. We tested this hypothesis by comparing the physical properties and fluorescence quenching behavior between 1 wt% water in glycerol solution which has similar viscosity to that of the DES ChCl:Urea with the aforementioned DES and IL in the presence of lithium salt as media. In complete contrast, irrespective of the temperature, kq is found to decrease monotonically with increasing concentration of LiCl within 1 wt% water in glycerol media. These findings therefore highlight the unusual characteristics of ILs and DESs as solubilizing media. The ionic nature of the IL and the high concentration of ions in the DES are deemed responsible for these outcomes.
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Affiliation(s)
- Manish Kumar
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India.
| | - Anjali
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India.
| | - Divya Dhingra
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India.
| | - Ankit Yadav
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India.
| | - Siddharth Pandey
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India.
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Chakraborty M, Barik S, Mahapatra A, Sarkar M. Effect of Lithium-Ion on the Structural Organization of Monocationic and Dicationic Ionic Liquids. J Phys Chem B 2021; 125:13015-13026. [PMID: 34788041 DOI: 10.1021/acs.jpcb.1c07442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In recent times, ionic liquid-based (ILs) electrolytic system has emerged as suitable alternative to the conventional organic solvent-based electrolytic system. However, since, anion of ILs is known to form aggregates in the presence of lithium-ions (Li+), and this can influence the transport properties of Li+ ion in a significant manner, it is, therefore, important to understand how lithium-ions influence the structure and dynamics of ILs. With this objective, in the present study, intermolecular interaction, structural organization, and dynamics of monocationic ILs (MILs) and dicationic IL (DIL) have been studied in the absence and presence of lithium salt. Specifically, for this purpose, two MILs, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([C3C1im][NTf2]), 1-hexyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([C6C1im][NTf2]), and a DIL, 1,6-bis(3-methylimidazolium-1-yl)hexane bis(trifluoromethylsulfonyl)amide ([C6(mim)2][NTf2]2) have been chosen in such a way that either the alkyl chain of MILs becomes equal or half of the spacer chain length of DIL. To understand the effect of the addition of lithium-ion on the structural organization of MILs and DIL, steady-state absorption and fluorescence spectroscopies, time-resolved fluorescence anisotropy and nuclear magnetic resonance (NMR) techniques have been used. Structural organization in the apolar and polar domains of ILs has been probed by following the rotational diffusion of suitably chosen solute in the concerned media through time-resolved fluorescence anisotropy (TRFA) measurements. TRFA studies have revealed that with the addition of Li+ ion, coordination between the Li+ ions and anions of MILs and DILs takes place in the ionic region leading to a change in the structural organization of the apolar regions of the respective medium. In fact, upon adding lithium-ions, a reduction in the packing of alkyl chains has also been observed for the MILs. However, not much change in the structural organization of the apolar region of the DIL has been observed when Li+ ion is added to it. In the presence of Li+ ions, a similar trend in the change of structural organization of polar regions for both MILs and DIL has been observed. Further, measurements of the self-diffusion coefficient through NMR have also supported the observation that Li+ ion also perturbs the nanostructural organization of the MIL in a significant manner than that it does for the DIL. The behavior of DIL in the presence of Li+ ion, as revealed by the present study, has been rationalized by considering the folded arrangement of DIL in the fluid-structure. Essentially, all of these investigations have suggested that the addition of lithium-ion significantly alters the microscopic behavior of MILs in comparison to that of DIL. The outcome of this study is expected to be helpful in realizing the potentials of these media as electrolytes in battery applications.
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Affiliation(s)
- Manjari Chakraborty
- School of Chemical Sciences, National Institute of Science Education and Research, Bhubaneswar, Bhimpur-Padanpur, Jatani, Khordha-752050, Odisha, India.,Homi Bhabha National Institute (HBNI), Mumbai, 400094, India
| | - Sahadev Barik
- School of Chemical Sciences, National Institute of Science Education and Research, Bhubaneswar, Bhimpur-Padanpur, Jatani, Khordha-752050, Odisha, India.,Homi Bhabha National Institute (HBNI), Mumbai, 400094, India
| | - Amita Mahapatra
- School of Chemical Sciences, National Institute of Science Education and Research, Bhubaneswar, Bhimpur-Padanpur, Jatani, Khordha-752050, Odisha, India.,Homi Bhabha National Institute (HBNI), Mumbai, 400094, India
| | - Moloy Sarkar
- School of Chemical Sciences, National Institute of Science Education and Research, Bhubaneswar, Bhimpur-Padanpur, Jatani, Khordha-752050, Odisha, India.,Homi Bhabha National Institute (HBNI), Mumbai, 400094, India
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Wang YL, Li B, Sarman S, Mocci F, Lu ZY, Yuan J, Laaksonen A, Fayer MD. Microstructural and Dynamical Heterogeneities in Ionic Liquids. Chem Rev 2020; 120:5798-5877. [PMID: 32292036 PMCID: PMC7349628 DOI: 10.1021/acs.chemrev.9b00693] [Citation(s) in RCA: 192] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/11/2022]
Abstract
Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.
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Affiliation(s)
- Yong-Lei Wang
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Bin Li
- School
of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, P. R. China
| | - Sten Sarman
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Francesca Mocci
- Department
of Chemical and Geological Sciences, University
of Cagliari, I-09042 Monserrato, Italy
| | - Zhong-Yuan Lu
- State
Key Laboratory of Supramolecular Structure and Materials, Institute
of Theoretical Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Jiayin Yuan
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- State
Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
- Centre of
Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania
- Department
of Engineering Sciences and Mathematics, Division of Energy Science, Luleå University of Technology, SE-97187 Luleå, Sweden
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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Dhingra D, Bhawna, Pandey A, Pandey S. Fluorescence Quenching by Nitro Compounds within a Hydrophobic Deep Eutectic Solvent. J Phys Chem B 2020; 124:4164-4173. [DOI: 10.1021/acs.jpcb.0c02231] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Divya Dhingra
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Bhawna
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Ashish Pandey
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Siddharth Pandey
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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Dhingra D, Bhawna, Pandey A, Pandey S. Pyrene Fluorescence To Probe a Lithium Chloride-Added (Choline Chloride + Urea) Deep Eutectic Solvent. J Phys Chem B 2019; 123:3103-3111. [DOI: 10.1021/acs.jpcb.9b01193] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Divya Dhingra
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Bhawna
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Ashish Pandey
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Siddharth Pandey
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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