Perfluorobutyric acid

The MDA was determined by the thiobarbituric acid method, referring to the method of Zhou [38 (link)], and the relative conductivity was determined by a portable DDG-2080-S conductivity meter (DDG-2080-S, Anhui, China). The contents of amino acids, soluble sugar, betaine, and superoxide dismutase (SOD) were determined with ELISA kits (Shanghai Enzyme-linked Biotechnology Co., Ltd., Shanghai, China). The contents of Na⁺ and K⁺ were measured by a DX-300 ion chromatograph (DIONEX Sunnyvale, USA), and the contents of organic acid were determined by ion chromatography (DX-300 ion chromatography system produced by DIONEX, Sunnyvale, CA, USA, with perfluorobutyric acid as the mobile phase), referring to the method of Guo et al. [39 ].

The IR spectra were registered on a Varian 3100 FTIR spectrometer (Digilab LLC, Marlborough, MA, USA) in 4000–400 cm⁻¹ range with the sample as a thin film or tablet (KBr).
The ¹H, ¹³C and ¹⁵N NMR spectra were run in CDCl₃ at room temperature on Bruker DPX-400 and AV-400 spectrometers (Bruker BioSpin GmbH, Rheinstetten, Germany) (400.13, 100.61 and 40.56 MHz, respectively). Chemical shifts were referred to TMS (¹H, ¹³C) and nitromethane (¹⁵N).
Mass spectra were recorded on an HR-TOF-ESI-MS Agilent 6210 with the registration mode of positive ions with acetonitrile as a solvent (in case of poor solubility by ultrasound) and 0.1% perfluorobutyric acid as an ionizing agent.
X-ray Diffraction Analysis. The single crystals of compounds 6 and 12 were grown by the slow evaporation of chloroform solutions at room temperature. The X-ray diffraction data were collected with a Bruker D8 VENTURE diffractometer (Bruker Optik GmbH, Ettlingen, Germany) (PHOTON III CMOS detector, Mo IµS3.0 X-ray source, Montel mirror-focused MoKα radiation λ = 0.71073 Å, N₂-flow cryostat) via 0.5° ω- and φ-scan techniques. Data were corrected for absorption effects using the multi-scan method (SADABS) [41 (link)]. The structure was solved and refined using the Bruker SHELXTL Software Package [42 (link)].
Elemental analysis was performed on a Thermo Scientific Flash 2000 Elemental Analyzer (Thermo Fisher Scientific Inc., Milan, Italy). Melting points were determined on a Kofler Hot-Stage Microscope PolyTherm A apparatus (Wagner & Munz GmbH, München, Germany).
The spectrophotometric determination of the elements was carried out on Specol-10 spectrophotometers and a KFK-2 photocolorimeter using appropriate techniques [43 (link)].
The morphology of the surfaces was determined with scanning electron microscopy using a Hitachi TM3000 electron microscope (Hitachi High-Technologies Corporation, Tokyo, Japan) with a magnification up to 30,000× and a resolution up to 25 nm. The experiments were performed at 5 kV. Surface elements were established by analysis of energy-dispersive X-ray spectra (EDX) (Quantax 70). The samples were scanned on a Quanta 200 FEI SEM-EXD electron microscope (Quanta 200 FEI, Hillsboro, OR, USA).

The organic solvents were dried and purified using standard procedures. Acrylonitrile, methylacrylate, ethylacrylate, methyl(meth)acrylate, acrylamide, and N-phenylmaleimide were purchased from Sigma Aldrich.
Target compounds 2–7 were isolated in pure form via recrystallization from a mixture of chloroform/hexane (1:3).
IR spectra were registered on a Varian 3100 FTIR spectrometer in the 4000–400 cm⁻¹ range with the sample as a thin film or tablet (KBr).
¹H, ¹³C, and ¹⁵N NMR spectra were performed in CDCl₃ at room temperature on Bruker DPX-400 and AV-400 spectrometers (400.13, 100.61, and 40.56 MHz, respectively).
Chemical shifts were referred to TMS (¹H and ¹³C) and nitromethane (¹⁵N).
Mass spectra were recorded on HR-TOF-ESI-MS Agilent 6210 equipment with the registration mode of positive ions with acetonitrile as a solvent (in case of poor solubility via ultrasound) and 0.1% perfluorobutyric acid as an ionizing agent.
To perform X-ray diffraction analysis, single crystals of compounds 2a and 2b were grown via the slow evaporation of chloroform solutions at room temperature. The X-ray diffraction data were collected with a Bruker D8 VENTURE diffractometer (PHOTON III CMOS detector, Mo IµS3.0 X-ray source, Montel mirror-focused MoKα radiation λ = 0.71073 Å, N₂-flow cryostat) via 0.5° ω- and φ-scan techniques. Data were corrected for absorption effects using the multi-scan method (SADABS) [51 (link)]. The structure was solved and refined using the Bruker SHELXTL Software Package (Sheldrick, 2008) [52 (link)].
The major non-H atoms were located from the electron density map and refined in anisotropic approximation. The positions of minor conformation (ca. 13% occupancy) of the disordered silotrane fragment in the 2b crystal structure and all H atoms of ordered parts of the structures were located from the difference electron density map. The atoms of the minor conformation were refined isotropically with equal atomic displacements (EADP) and restraints on the similarity of equivalent bond distances (SADI). The H atom located on N2 in 2a was refined without geometrical restraints; the other H atoms were refined in the riding model. Isotropic displacements of the H atoms were assigned as 1.2Ueq of the pivot atoms.
Crystal data, data collection, and structure refinement details are summarized in Table 5. Atomic coordinates, bond lengths, bond angles, and atomic displacement parameters for the crystal structures of 2a and 2b have been deposited with the Cambridge Crystallographic Data Centre (CCDC) with deposition numbers CCDC 2263862 and 2263863. These data can be obtained free of charge from the CCDC via URL: https://www.ccdc.cam.ac.uk/structures/ (accessed on 18 May 2023).
Elemental analysis was performed on a Thermo Scientific Flash 2000 Elemental Analyzer (Thermo Fisher Scientific Inc., Milan, Italy). Melting points were determined on a Kofler Hot-Stage Microscope PolyTherm A apparatus (Wagner & Munz GmbH, München, Germany).
General Procedure for the Synthesis of Silatranes 2–7.
A mixture of silatrane 1 (1 mmol) and corresponding acrylate (1 or 2 mmol) in 10 mL of methanol was stirred at 50 °C for 2 h in an inert atmosphere (N₂) or in air. The solvent was removed under reduced pressure. The residue was washed many times with ether, dried, and the products 2–7 were obtained. If necessary, the resulting powder or oil was recrystallized from a mixture of chloroform/hexane (1:3).