Received: January2023

DOI 10.17677/fn20714807.2023.01.03

Fluorine Notes, 2023, 146, 5-6

QUANTUM-CHEMICAL STUDY OF STRUCTURE OF FLUOROALCOHOLATE ANIONS GENERATED FROM POLYFLUORINATED ALCOHOLS

S. V. Kudashev¹, V. A. Babkin², D. S. Andreev², A. V. Ignatov², N. V. Kuznetsova¹, V. F. Zheltobryukhov¹, E. A. Matushkin¹, V. N. Arisova¹, A. A. Kudasheva³

¹Volgograd State Technical University,400005 Volgograd, Lenin av., 28.

e-mail: kudashev-sv@yandex.ru

² Volgograd State Technical University (Sebryakovsky br.), 403343 Volgograd Region, Mikhailovka, Michurina st., 21.

³ Volgograd State Medical University, 400131 Pavshikh Bortsov sq., 1.

Annotation. Structure of H(CF₂CF₂)_nCH₂O^– (n = 1-6) anions formed from corresponding polyfluorinated alcohols was studied by DFT-PBE0/6-311g** quantum-chemical method. The optimal geometric and electronic structure of fluoroalcoholate anions has been obtained. The conformations of studied particles, which are characterized by the lowest value of total energy, are determined. The contribution of proton-donor and proton-acceptor interactions to stabilization of anion particles is shown.

Keywords: polyfluorinated alcohols, alcoholate anions, fluoropolymers, quantum chemical calculation, DFT method, structure, intramolecular interactions.

Introduction

Modifying additives based on poly- and perfluorinated compounds contribute to improvement of complex of properties of polymers. Using of polyfluorinated alcohols H(CF₂CF₂)_nCH₂OH (n = 1-6) and montmorillonite clay makes it possible to increase the thermal, fire and light resistance of resulting polymer composite materials [1-3]. Using a complex of instrumental analytical methods, it was shown [4] that immobilization of polyfluorinated alcohols on indicated layered aluminosilicate contributes to the partial displacement of polysilicic and carbonic acids from salts, as well as the reaction of metal oxides included in clay mineral base with alcohols, which leads to formation of alcoholates [H(CF₂CF₂)_nCH₂O]_yM_x (М = Na⁺ (predominantly), K⁺, Ca²⁺, Al³⁺ , etc.).

The presence of metal fluoroalcoholates in composition of considered organoclays ensures their participation in mechanism of opening the ε-caprolactam ring during preparation of polycaproamide, increasing the molecular weight of product. In this connection, the establishment of electronic and geometric structure of H(CF₂CF₂)_nCH₂O^– anions will allow us to further evaluate their reactivity in above mechanism and optimize the compositions of organoclays (ratio of alcohol and alcoholate phases) based on polyfluorinated alcohols and montmorillonite.

The aim of this paper is a quantum-chemical study (by DFT-PBE0/6-311g** method) of structure of fluoroalcoholate anions generated from polyfluorinated alcohols.

Results and discussion

The geometric and electronic structure of H(CF₂CF₂)_nCH₂O^–anions (charge = -1, multiplicity = 1) was studied by semi-empirical quantum-chemical method DFT-PBE0/6-311g** (that built into Firefly program and partially based on GAMESS source code [5-7]) in approximation of isolated particle in gas phase and with geometry optimization in all parameters by standard gradient method. Structures of studied particles optimized in all parameters were obtained (see Fig. 1-6 and Table 1-6).

Figure 1. Geometrical and electronic structure of HCF₂CF₂CH₂O^–anion (total energy (Е₀) = -1549485 kJ/mol).

Table 1 - Optimized bond lengths, bond anglesand atomic charges of HCF₂CF₂CH₂O^–anion.

Figure 2. Geometric and electronic structure of HCF₂CF₂CH₂O^–– anion (Е₀ = -2797037 kJ/mol).

Table 2. Optimized bond lengths, bond anglesand atomic charges of HCF₂CF₂CH₂O^–anion.

Figure 3. Geometrical and electronic structure of HCF₂CF₂CH₂O^–anion (Е₀ = -4044571 kJ/mol).

Table 3. Optimized bond lengths, bond angles and atomic charges of HCF₂CF₂CH₂O^–anion.

Figure4. Geometrical and electronic structure of H(CF₂CF₂)₄CH₂O^–– anion (Е₀ = -5292102 kJ/mol).

Table 4. Optimized bond lengths, bond anglesand atomic charges of H(CF₂CF₂)₄CH₂O^–anion.

Figure 5. Geometrical and electronic structure of HCF₂CF₂CH₂O^–anion (Е₀ = -6539623 kJ/mol).

Table 5. Optimized bond lengths, bond angles and atomic charges of HCF₂CF₂CH₂O^–anion.

Figure 6. Geometrical and electronic structure of HCF₂CF₂CH₂O^– anion (Е₀ = -7787149 kJ/mol).

Table 6. Optimized bond lengths, bond angles and atomic charges of HCF₂CF₂CH₂O^–anion.

As can be seen, the chemical structure of HCF₂CF₂CH₂O^–anions have a decisive influence on their electronic and geometric structure. An increase in number of -CF₂CF₂- groups leads to a change in total energy of anions (decreases from 1549485 kJ mol 1 to 7787149 kJ mol^-1 when passing from n = 1 to n = 6), in negative oxygen atomic charges (increases from -0.653 to -0.628) and in positive hydrogen atomic charges of HCF₂ group (increases from 0.073 to 0.141). Stabilization of fluoroalcoholate anions is promoted by proton-donor and proton-acceptor interactions CF₂H^+δ···^–O–CH₂ and CH₂···F₂C, as well as interactions CF₂H···●O–CH₂ and CH₂···F₂C for radical species H(CF₂CF₂)_nCH₂O^● described in [4, 8, 9].

Conclusion

Using DFT-PBE0/6-311g** method, the electronic and geometric structure of HCF₂CF₂CH₂O^–– fluoroalcoholate anions was calculated, and optimized bond lengths, bond angles and atomic charges were determined. An increase in number of -CF₂CF₂-groups, as well as the proton-donor and proton-acceptor interactions between atoms in anion together ensure the stabilization of its structure.

References

1. Kudashev S. V., Methods for introducing poly- and perfluorinated fragments into macromolecular systems (Review), Fluorine notes, 2020, 3(130), 3-4.
2. Kudashev S. V., Daniel Z. M., Dauda F., Arisova V. N., Bogdanov A. I., Zheltobryukhov V. F., Fofonova A. A., Matushkin E. A., Preparation of organoclay based on 1Н,1Н,13Н-trihydroperfluorotridecan-1-ol and montmorillonite, Fluorine notes, 2022, 3(142), 1-2.
3. Kudashev S. V., Daniel Z. M., Dauda F., Arisova V. N., Bogdanov A. I., Zheltobryukhov V. F., Fofonova A. A., Matushkin E. A., X-ray study of montmorillonite modified with tetrafluorophthalic acid and its anhydride, Fluorine notes, 2022, 2(141), 1-2.
4. KudashevS. V., Modification of a number of heterochain polymers with compositions based on polyfluorinated alcohols and montmorillonite, Abstract of PhD thesis (in candidacy for a degree of PhD in Chemistry by specialty 02.00.06, VolgGTU, Volgograd, 2020, 48 p. (in Russian)
5. Granovsky A. A., Firefly version 8, 2013, Access mode: http://classic.chem.msu.su/gran/firefly/index.html.
6. Schmidt M. W., Baldridge K. K., Boatz J. A., Elbert S. T., Gordon M. S., Jensen J. H., Koseki S., Matsunaga N., Nguyen K. A., Su S. J., Windus T. L, Dupuis M., Montgomery J. A., General atomic and molecular electronic structure system, Journal of Computational Chemistry, 1993, 14, 1347-1363.
7. Bode B. M., Gordon M. S., MacMolPlt: A graphical user interface for GAMESS, Journal of Molecular Graphics and Modeling, 1998, 16(3), 133-138.
8. Kudashev S. V., Babkin V. A., Andreev D. S., Ignatov A. V., Kuznetsova N. V., Kosogorina M. D., Structure of paramagnetic centers generated from polyfluorinated alcohols, Fluorine Notes, 2020, 6(133), 1-2.
9. Kudashev S. V., Kondrasenko A. A., Matsulev A. N., Babkin V. A., Belousova V. S. Andreev., D. S, Zheltobryukhov V. F., Kuznetsova N. V., Modification of polycaproamide with a composition based on 1H,1H,13H-trihydroperfluorotridecan-1-ol and montmorillonite, Chemical fibers, 2021, 5, 3-7 (in Russian).

ARTICLE INFO
Received 30 January 2023
Accepted 13 February 2023
Available online February 2023

Recommended for publication by PhD O.V. Bryzgalova

eLIBRARY Document Number (EDN) WROKYV

Fluorine Notes, 2023, 146, 5-6