Determination of New IR and UV/VIS Spectroscopic Parameters of the C 84 -D 2 :22 Isomer for Its Quantitative Assessment, Identiﬁcation and Possible Applications

: The stable isomers of the higher fullerenes C 76 -D 2 and C 84 -D 2 :22, as well as fullerenes C 60 and C 70 were isolated from carbon soot by the new and improved extraction and chromatographic methods and processes. Characterizations of the C 84 -D 2 :22 isomer in this study were performed by infrared and electronic absorption spectroscopy. All of the experimentally observed IR and UV/VIS bands were in excellent agreement with the semi-empirical, DFT and TB potential theoretical calculations for this molecule. The molar extinction coefﬁcients and the integrated molar extinction coefﬁcients of the observed larger number of completely separated infrared absorption maxima and shoulders of fullerene C 84 -D 2 :22, as well as of its main convoluted maxima, in different and new relevant entire integration ranges, including neighboring, and all surrounding absorption shoulders were determined and their relative intensities compared. In addition, the molar absorptivity of the electronic absorption bands of this carbon cluster was found. The new IR and UV/VIS spectroscopic parameters that are signiﬁcant for the quantitative determination, identiﬁcation and numerous possible applications of C 84 -D 2 :22 are obtained and their changes compared to C 76 -D 2 observed. Isolated and characterized C 84 -D 2 :22, as well as other fullerenes from this research can be used in electronic, optical, chemical and biomedical devices, superconductors, semiconductors, batteries, catalysts, polymers, sensors, solar cells, nanophotonic lenses with better optical transmission, refraction and wettability, diagnostic and therapeutic pharmaceutical substances, such as those against diabetes, cancer, neurodegenerative disorders, free radical scavenging, radio nuclear, antibacterial and antiviral agents that can inhibit HIV 1, HSV, COVID-19, inﬂuenza, malaria and so forth.

The aim of this study was to determine the new IR and UV/VIS spectroscopic parameters that are important for the quantitative assessment, as well as for the identification and possible applications of the higher fullerene C 84 -D 2 : 22. The IR spectrum of the sample of C 84 -D 2 :22, isolated in one of the original advanced processes [36], recorded in the absorption mode on a Thermo Scientific FT-IR spectrometer, over the relevant region from 400 to 2000 cm −1 , and the UV/VIS spectrum recorded on a GBC Cintra spectrophotometer, from 200 to 900 nm, previously applied for its identification [26,27,39], were used and presented in this article for determination of the new parameters.
In addition, the molar extinction coefficients and the integrated molar extinction coefficients of several main and characteristic absorption maxima of these fullerenes, in the appropriate, different integration ranges were reported and their relative intensities compared [20][21][22][23].
In this article, the molar absorptivity and the integrated molar absorptivity of the main convoluted absorption maxima of C 84 -D 2 :22, in new, proportionally larger integration ranges, compared to previous measurements for this molecule [20,21], including neighboring, and all surrounding absorption shoulders were determined. The relative intensities of the main, completely convoluted infrared absorption maxima, computed from ε λ and from ψ λ , were compared.
It is important to mention that excellent agreement is found between the relative intensities of the molar absorptivity and integrated molar absorptivity of the main, completely convoluted infrared absorption maxima of C 84 -D 2 :22, with all surrounding absorption shoulders, in the applied corresponding new entire, proportionally larger integration ranges in this article, in comparison to previous measurements [20,21].
Excellent agreement was also found between the relative intensities of several main and characteristic IR absorption bands of this fullerene, computed from ε λ and from ψ λ values, in the previous work [20,21], in the appropriate, proportionally smaller integration ranges.
The molar extinction coefficients and the integrated molar extinction coefficients in the applied integration ranges in the previous [20,21] and this study of the corresponding IR and UV/VIS bands in all the obtained spectra of the chromatographically isolated C 84 -D 2 :22 samples from this research [20,21,26,27,[36][37][38][39][40][41]43] are in excellent agreement.
The obtained novel IR and UV/VIS spectroscopic parameters for the higher fullerene C 84 -D 2 :22 are significant for its quantitative assessment, as well as for the identification and numerous possible applications.
Further changes of its spectral properties and parameters, in comparison to C 76 -D 2 [20][21][22][23], can be used for its incorporation in nanophotonic materials and devices, such as special lenses [22,23] with improved optical absorption in the UV region and transmission in the visible part, refraction features and wettability.

Experimental Methods
Measurement of the Molar Absorptivity, and Integrated Molar Absorptivity of Deconvoluted and Convoluted Absorption Bands of C 84 -D 2 :22. The IR spectrum of the C 84 -D 2 :22 sample, isolated in one of the original, advanced extraction and chromatographic processes [36], was measured on a Thermo Scientific FT-IR spectrometer Nicolet IR-6700, by the KBr pellet technique, in the region from 400 to 2000 cm −1 , at a resolution of 1 cm −1 and room temperature, in the absorption mode, in order to find the new parameters for its quantitative assessment, as well as in the transparency mode previously [43] for its qualitative detection.
Sample of C 84 -D 2 :22 (0.312 mg) was mixed with 76.3 mg of KBr, the resulting powder was compressed into a pellet with the hydraulic Perkin Elmer press, at 4 t/cm 2 and placed in the FT-IR spectrometer.
In this article, the molar absorptivity and the integrated molar absorptivity of the observed series of a larger number, compared to the previous study [20,21], of completely separated infrared absorption maxima and shoulders from the presented spectrum of the isolated sample of C 84 -D 2 :22 were measured on a Thermo Scientific FT-IR spectrometer with the OMNIC software and automatic subtraction of the baseline.
In addition, the molar absorptivity of the main convoluted absorption maxima of this molecule, in different and new relevant entire, proportionally larger integration ranges, compared to previous measurements [20,21], including neighboring, and all surrounding absorption shoulders was measured on the same spectrometer.
In the previous study, the molar extinction coefficients and the integrated molar extinction coefficients of the main and characteristic infrared maxima, inadequate, proportionally smaller integration ranges, compared to this study, were determined from the presented spectrum of the sample of C 84 -D 2 :22 [20,21], isolated in another original, advanced process [38], recorded in a-mode on a Thermo Scientific FT-IR spectrometer [20,21].
The mass of the obtained KBr pellet in this work, with the applied sample of C 84 -D 2 :22, was 76.6 mg, and the percentage of carbon determined by the elemental analysis was 0.407%. Its measured thickness (b) was 0.72 mm, ∼0.07 cm, diameter (R) was 0.7 cm and the half diameter (r) was 0.35 cm, similarly to the previously obtained KBr pellet with the C 76 -D 2 sample [22,23].
The volume of this pellet (V), determined from the abovementioned parameters by the equation V = r 2 πb was 0.0278 cm 3 . Concentration (c) of fullerene C 84 -D 2 :22 in this pellet computed from the above-mentioned mass of C 84 -D 2 :22 in the pellet, its molar mass of 1008.84 g/mol, and the volume of the pellet was 0.01 mol/L. The (bc) −1 value determined for the applied C 84 -D 2 :22 sample in KBr pellet from the abovementioned experimental parameters was 1428.6 L cm −1 mol −1 , ca 1429 L cm −1 mol −1 . The (bc) −1 value for the applied C 76 -D 2 sample in the previous IR study [22,23] was obtained by a similar procedure. The above-mentioned infrared spectroscopic parameters that were investigated and presented for the isolated C 76 -D 2 :22 previously [20][21][22][23] showed distinct properties.
Measurement of the Molar Absorptivity of Absorption Bands of C 84 -D 2 :22. The electronic absorption spectrum of the C 84 -D 2 :22 sample was measured on the GBC Cintra 40 spectrophotometer, in the range of 200-900 nm, at a resolution of 1 nm, at ambient condi-tions, for its qualitative detection previously [26,27,39], and presented for the determination of the new parameters for its quantitative assessment in this study.
Solutions of fullerene C 84 -D 2 :22 in hexane, conc. 10 −5 mol/dm 3 were used. The thickness of the cuvette was 1 cm. The (bc) −1 value determined for the C 84 -D 2 :22 sample from the above-mentioned parameters was 100.000 L cm −1 mol −1 . The (bc) −1 value for the applied C 76 -D 2 sample in the previous UV/VIS study [22,23] was obtained by a similar procedure. The molar extinction coefficients of absorption bands of C 76 -D 2 [22,23] showed distinct properties.

Results and Discussion
The new IR and UV/VIS spectroscopic parameters that are important for the quantitative assessment, as well as for the identification and possible applications of the higher fullerene C 84 -D 2 :22 were determined in this study.
In the previous [22,23] and this article, the molar absorptivity and the integrated molar absorptivity of the observed entire new series of a larger number, then formerly [20,21], of various characteristic, completely deconvoluted IR absorption bands of the isolated C 76 -D 2 [22,23] and C 84 -D 2 :22 isomer were determined.
Besides that, the molar extinction coefficients and the integrated molar extinction coefficients of several main and characteristic absorption maxima of these carbon clusters, in the appropriate, different integration ranges were reported [20][21][22][23].
In this article, the molar absorptivity of the main convoluted absorption maxima of C 84 -D 2 :22, including neighboring, and all surrounding absorption shoulders was determined, in new entire, proportionally larger integration ranges, compared to previous measurement [20,21]. The molar extinction coefficients of the UV/VIS absorption bands of C 76 -D 2 [22,23] and C 84 -D 2 :22 were also found.
The new, characteristic infrared spectrum of the sample of C 84 -D 2 :22, isolated in one of the original, advanced processes [36], was recorded in the absorption mode, on a Thermo Scientific FT-IR spectrometer, Figure 1, for determination of the abovementioned novel parameters for its quantitative assessment, as well as in transparency mode previously [43] for its qualitative detection.
The main absorption bands [43] in this spectrum appear in the region relevant for the identification of C 84 -D 2 :22 [41], from ca. 1050 to 1800 cm −1 . The dominant absorption maximum is observed at 1384. 6 [41] in the spectrum, shown in Figure 1, correspond to C-C vibration modes that are in agreement with the theoretical predictions for C 84 -D 2 :22 [59][60][61].
From the IR absorption spectra presented in the recent article [22,23], and in this article in Figure 1, the values of absorbance A λ were determined for all the separated absorption maxima and shoulders of C 76 -D 2 [22,23] and C 84 -D 2 :22. Determination of molar extinction coefficients of separated infrared bands of C 76 -D 2 [22,23] and of C 84 -D 2 :22 was achieved according to Lambert and Beer law, using the absorbance A λ read at a given wave number, through the Equation (1) [74], which was also applied in the previously mentioned investigations [15][16][17][18][20][21][22][23]. In the previous [22,23] and this article also, the integrated molar absorptivity of deconvoluted absorption maxima and shoulders, as well as of convoluted absorption maxima, with neighboring, and all surrounding shoulders, in the entire integration range, was determined from the presented infrared absorption spectra of the isolated C 76 -D 2 [22,23] and of the sample of C 84 -D 2 :22, Figure 1. The integrated intensity expressed in cm mol −1 or 10 −5 Km mol −1 was computed by Equation (2) [72], applied in the previous studies [15][16][17][18][20][21][22][23].
The molar extinction coefficients and the integrated molar extinction coefficients in adequate integration range, calculated by the Equations (1) and (2), of deconvoluted infrared absorption bands of C 76 -D 2 were presented previously [22,23] and of the observed separated absorption bands of C 84 -D 2 :22 in the presented spectrum, Figure 1, in this article in Table 1. The integrated molar absorptivity of several absorption maxima with neighboring absorption shoulders of C 84 -D 2 :22 are also reported in this table. The molar absorptivity and the integrated molar absorptivity were calculated by the Equations (1) and (2) for the main convoluted absorption maxima of C 76 -D 2 [20][21][22][23] and of C 84 -D 2 :22, in adequate integration ranges applied previously [20,21], as well as in the new integration ranges in this study, with all surrounding absorption shoulders, from the presented spectrum in Figure 1, and reported in Table 2. The relative intensities of the main, completely convoluted C 84 -D 2 :22 maxima, computed from ε λ and from ψ λ values are compared in this table. It can be seen from the table that excellent agreement is found between the relative intensities of the main, completely convoluted infrared absorption maxima of C 84 -D 2 :22, computed from ε λ and from ψ λ , in the applied new entire, larger integration ranges, then in previous studies [20,21], taking as 100 the most intense band at 1384.6 cm −1 with a shoulder at 1399.8 cm −1 , Table 2.
Excellent agreement was also found in the previous article [20,21] between the relative intensities of several main and characteristic IR absorption maxima of this molecule, calculated from ε λ and from ψ λ , in the appropriate, proportionally smaller integration ranges [20,21], compared to this study, taking as 100 the most intense band at 1384.5 cm −1 in the spectrum of the C 84 -D 2 :22 sample [20,21].
In the former study, the original, characteristic electronic absorption spectrum of the chromatographically isolated C 76 -D 2 sample was used [22,23], and in this study, the UV/VIS spectrum of the isolated C 84 -D 2 :22 sample, previously applied for its identification [26,27,39], is presented in Figure 2, for determination of the above-mentioned novel parameters for its quantitative assessment. A series of the electronic absorption maxima attributed to C 84 -D 2 :22 appears in this spectrum [26,27,39] in the UV region, from 200 to 400 nm, at 200.00, 230.11, 239.34, 251.19, 261.03 and 272.12 nm, followed by the bands at 287. 19, 305.10, 318.40, 333.65 and 357.39 nm, as well as weak decreasing absorption in the visible part extended to 900 nm. The electronic absorption bands in the spectrum [26,27,39], shown in Figure 2, correspond to the electronic transitions from HOMO to LUMO that are in agreement with the theoretical calculations for this molecule [60][61][62].
Absorbance A λ of the electronic absorption bands was determined from the UV/VIS spectrum of C 76 -D 2 previously [22], and from the UV/VIS spectrum of C 84 -D 2 :22 [26,27,39], presented in Figure 2, in the current study. Molar absorptivity E λ was calculated according to Equation (1) for C 76 -D 2 [22] and for C 84 -D 2 :22, and reported for this molecule in Table 3.
The appearance of a larger number of characteristic, intense and pronounced absorption bands in the mentioned spectral regions, fine structure, as well as a general increase in molar absorptivity and integrated molar absorptivity in the IR and UV/VIS spectra of C 84 -D 2 :22, in relation to C 76 -D 2 and basic fullerenes [15][16][17][18][20][21][22][23]44,45] indicate a decrease in the symmetry of C 84 -D 2 :22 compared to these fullerenes. The aforementioned changes of the spectroscopic parameters of C 84 -D 2 :22, in comparison to C 76 -D 2 [20][21][22][23] can also lead to further changes and improvement of the refraction and wettability features. This can be used for its applications in nanophotonic materials and devices, such as special lenses with improved optical absorption of UV rays, transmission in the visible part, and other physical properties. Recent investigations [22][23][24][25][75][76][77] indicate that incorporation of fullerene-based materials in standard polymers for the rigid and soft contact lenses generally enhances their optoelectronic and mechanical properties.
The infrared spectrum of the sample of C 84 -D 2 :22, isolated in one of the original advanced processes [36], recorded in the absorption mode on a Thermo Scientific FT-IR spectrometer, over the relevant region from 400 to 2000 cm −1 , and the electronic absorption spectrum recorded on a GBC Cintra spectrophotometer, from 200 to 900 nm, previously applied for its identification [26,27,39], were presented in this study for determination of new parameters for its quantitative assessment, as well as identification and possible applications.
In the previous [22,23] and this article, the molar absorptivity and the integrated molar absorptivity of the observed entire series of a larger number, then formerly [20,21], of various characteristic and new, completely deconvoluted IR absorption maxima and shoulders of the isolated C 76 -D 2 [22,23] and C 84 -D 2 :22 isomer were determined.
In addition, the molar extinction coefficients and the integrated molar extinction coefficients of several main and characteristic absorption maxima of these molecules in the appropriate, different integration ranges were determined and reported together with the relative intensities [20][21][22][23].
In this article, the molar absorptivity and the integrated molar absorptivity of the main convoluted absorption maxima of C 84 -D 2 :22, in new, proportionally larger integration ranges, compared to the previous studies [20,21], including neighboring, and all surrounding absorption shoulders were determined and their relative intensities compared.
It is important to emphasize that in this article the excellent agreement is obtained between the relative intensities of the main, completely convoluted IR maxima of C 84 -D 2 :22, with all surrounding absorption shoulders, in the applied new entire, proportionally larger integration ranges, then previously [20,21], computed from the ε λ and from the ψ λ values, taking as 100 the most intense vibration mode of this fullerene at 1384.6 cm −1 , with a neighboring shoulder at 1399.8 cm −1 .
Excellent agreement was also found in the previous article [20,21] between the relative intensities of several main and characteristic IR absorption maxima of this molecule, calculated from ε λ and from ψ λ , in adequate, proportionally smaller integration ranges, taking as 100 the most intense band at 1384.5 cm −1 in the presented spectrum of the isolated sample of C 84 -D 2 : 22. It should be mentioned that the molar extinction coefficients and the integrated molar extinction coefficients in the applied integration ranges in the previous [20,21] and this study of the corresponding main and characteristic absorption bands in all the IR and UV/VIS spectra of the chromatographically purified C 84 -D 2 :22 samples from this research [20,21,26,27,[36][37][38][39][40][41]43] are in excellent agreement.
The new spectroscopic results and parameters obtained for this carbon cluster are significant for its quantitative assessment, as well as for the identification and numerous possible applications. The observed further changes of its spectral properties and parameters, compared to C 76 -D 2 [20][21][22][23], can be useful for the applications in optoelectronic materials and devices with advanced properties, such as nanophotonic lenses with improved optical absorption in the UV region and transmission in the visible part, as well as with enhanced refraction and wettability features.
Additional Points: Figure