The influence of distribution of hydroxyl groups on vibrational spectra of fullerenol C60(OH)24 isomers: DFT study

Structure and Vibrational Spectroscopy of C82 Fullerenol Valent Isomers: An Experimental and Theoretical Joint Study

Gd@C₈₂O_xH_y endohedral complexes for advanced biomedical applications (computer tomography, cancer treatment, etc.) were synthesized using high-frequency arc plasma discharge through a mixture of graphite and Gd₂O₃ oxide. The Gd@C₈₂ endohedral complex was isolated by high-efficiency liquid chromatography and consequently oxidized with the formation of a family of Gd endohedral fullerenols with gross formula Gd@C₈₂O₈(OH)₂₀. Fourier-transformed infrared (FTIR) spectroscopy was used to study the structure and spectroscopic properties of the complexes in combination with the DFTB3 electronic structure calculations and infrared spectra simulations. It was shown that the main IR spectral features are formed by a fullerenole C₈₂ cage that allows one to consider the force constants at the DFTB3 level of theory without consideration of gadolinium endohedral ions inside the carbon cage. Based on the comparison of experimental FTIR and theoretical DFTB3 IR spectra, it was found that oxidation of the C₈₂ cage causes the formation of Gd@C₈₂O₂₈H₂₀, with a breakdown of the integrity of the parent C₈₂ cage with the formation of pores between neighboring carbonyl and carboxyl groups. The Gd@C₈₂O₆(OOH)₂(OH)₁₈ endohedral complex with epoxy, carbonyl and carboxyl groups was considered the most reliable fullerenole structural model.

Laboratory IR Spectra of the Ionic Oxidized Fullerenes C60O+ and C60OH. J Phys Chem A 2022;126:2928-2935. [PMID: 35533303 PMCID: PMC9125688 DOI: 10.1021/acs.jpca.2c01329]

We present the first experimental vibrational spectra of gaseous oxidized derivatives of C₆₀ in protonated and radical cation forms, obtained through infrared multiple-photon dissociation spectroscopy using the FELIX free-electron laser. Neutral C₆₀O has two nearly iso-energetic isomers: the epoxide isomer in which the O atom bridges a CC bond that connects two six-membered rings and the annulene isomer in which the O atom inserts into a CC bond connecting a five- and a six-membered ring. To determine the isomer formed for C₆₀O⁺ in our experiment—a question that cannot be confidently answered on the basis of the DFT-computed stabilities alone—we compare our experimental IR spectra to vibrational spectra predicted by DFT calculations. We conclude that the annulene-like isomer is formed in our experiment. For C₆₀OH⁺, a strong OH stretch vibration observed in the 3 μm range of the spectrum immediately reveals its structure as C₆₀ with a hydroxyl group attached, which is further confirmed by the spectrum in the 400–1600 cm^–1 range. We compare the experimental spectra of C₆₀O⁺ and C₆₀OH⁺ to the astronomical IR emission spectrum of a fullerene-rich planetary nebula and discuss their astrophysical relevance.

The strong interaction of actinyl ions with fullerenol driven by multiple hydrogen bonds

The removal of actinides from radioactive wastewater is an important subject with the continuous application of nuclear energy. All-electron density functional theory (DFT) calculations were carried out to understand the adsorption behaviors of actinyl ions on C₆₀(OH)₂₄ fullerenol in this work. The outer-sphere (OS) bonding mode is more stable than the inner-sphere one because of the formation of multiple hydrogen bonds in the OS mode. The actinyl(VI) ions can be more efficiently absorbed by fullerenol than actinyl(V) ones. The bonding nature of actinyl ions with C₆₀(OH)₂₄ was revealed by various electron density topological analyses. Multiple hydrogen bonds formed in the OS complexes show moderate bond strength with partial covalent nature and are responsible for their high stability. IR spectra were fingerprinted to distinguish the interaction modes of actinyl ions with C₆₀(OH)₂₄.

Surface functionalization of chitosan with 5-nitroisatin

Several possible configurations (CS/NI1-10) for the surface adsorption of 5-nitroisatin (NI) on the chitosan polymer (CS) were investigated using quantum mechanical methods in the gas and solution phases. The values of the binding energies indicate the energetic stability of these configurations. The solvation energies demonstrate that the solubility of NI and CS increases in the presence of each other. The role of hydrogen bonds in noncovalent surface functionalization was determined by AIM analysis. The mechanism of covalent surface functionalization and the explicit solvent effects (methanol) in this mechanism were investigated and it was determined that the covalent functionalization through Schiff base formation is possible. These findings, in addition to the biological applications of the chitosan Schiff bases and their complexes, led us to synthesize a new Schiff base from condensation reaction of CS and NI (CSB) together with its Ni(II) and Cu(II) complexes. The synthesized compounds were characterized by the elemental analysis, infrared spectroscopy (IR), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Also, optimized geometries, assignment of the IR vibrational bands as well as exploring of the frontier orbitals of the synthesized compounds have been calculated using density functional levels of theory.