SYNTHESIS AND THERMAL ANALYSIS OF MIXED-LIGAND COMPLEXES OF POTASSIUM 2-(4-ISOBUTYLPHENYL) PROPANOATE WITH 3D-METAL NITRATE SALTS AND ACETAMIDE

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 45 SYNTHESIS AND THERMAL ANALYSIS OF MIXED-LIGAND COMPLEXES OF POTASSIUM 2-(4-ISOBUTYLPHENYL) PROPANOATE WITH 3D-METAL NITRATE SALTS AND ACETAMIDE B.D. Rakhimov1, Sh.B. Khasanov2, O.I. Khudoyberganov3, A.D. Kudiyarova4 PhD student the Khorezm Ma’mun Academy1 Deputy Chairman (PhD), Khorezm Ma’mun Academy for Scientific Affairs2 PhD., Senior Scientific Researcher, Khorezm Ma’mun Academy3 Associate Professor, Department of Organic and Inorganic Chemistry, Karakalpak State University4 https://doi.org/10.5281/zenodo.17744407 Abstract. This study reports the synthesis, structural characterization, and thermal analysis of mixed-ligand complexes formed between potassium 2-(4-isobutylphenyl) propanoate (the potassium salt of ibuprofen), 3d-metal nitrates (Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)), and acetamide. The complexes were synthesized under mild, reproducible conditions in ethanol through coordination interactions between the ligands and the metal centers. The resulting compounds were characterized using elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric/differential scanning calorimetry (TGA/DSC) techniques. Shifts in the ν(C=O) and ν(C–O) stretching frequencies in the IR spectra confirmed the coordination of carboxylate oxygen atoms to the metal ions. Thermal analysis revealed that the complexes lost their crystal water molecules at 100–150 °C, followed by decomposition of the organic ligands between 250–450 °C. The final residues were identified as corresponding metal oxides (MnO, CoO, NiO, CuO, ZnO). These results demonstrate the successful formation of thermally stable mixed-ligand complexes based on ibuprofen potassium salt. The synthesized complexes show promising structural and thermal stability, indicating their potential as drugdelivery carriers or biologically active materials. Keywords: potassium ibuprofenate, mixed-ligand complex, 3d-metal, acetamide, IR spectroscopy, thermal analysis. Introduction In recent years, the synthesis of coordination compounds containing biologically active ligands has become one of the most promising areas of inorganic chemistry. In particular, complexes formed between metal ions and carboxylate-containing nonsteroidal anti-inflammatory drugs (NSAIDs) have attracted increasing attention as potential sources of new bioactive materials with enhanced pharmacological properties. Among these, potassium 2-(4-isobutylphenyl) propanoate (the potassium salt of ibuprofen) stands out due to its well-known anti-inflammatory, analgesic, and antipyretic effects. The coordination of this salt with metal ions can significantly alter its physicochemical characteristics, including solubility, thermal stability, and biological activity. 3d-metal ions such as Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) possess diverse coordination numbers and geometrical configurations, providing an opportunity to form mixed-ligand SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 46 complexes based on ibuprofen potassium salt with unique structural and chemical properties. In mixed-ligand systems, an additional donor-type ligand — such as acetamide — can enrich the coordination sphere of the metal center, enhance complex stability, and influence its electronic environment. Furthermore, thermal analysis (TGA/DSC) of such complexes provides valuable insights into their decomposition stages, the presence of crystalline water, thermal resistance, and the nature of the residual phase (metal oxide). Therefore, the synthesis and thermal characterization of mixed-ligand complexes involving potassium ibuprofenate, 3d-metal nitrates, and acetamide are of both scientific and practical importance. The main aim of this research is to synthesize these complexes, investigate their structural and thermal stability properties, and elucidate the nature of coordination bonding within the obtained compounds. Literature review. The synthesis and properties of mixed-ligand complexes, especially those containing biologically active ligands and transition metals, represent one of the most relevant areas of coordination chemistry. Ibuprofen [1], a nonsteroidal anti-inflammatory drug, and its salts — particularly potassium 2-(4-isobutylphenyl) propanoate — are considered effective ligands due to the strong coordinating ability of their carboxylate groups toward metal ions. In recent years, the synthesis, structural characterization, and biological activity of ibuprofen complexes with metals such as copper(II), zinc(II), and nickel(II) have been investigated [2,3]. These studies indicate that the carboxylate ligand often coordinates in a bidentate manner, forming stable metallacyclic structures. Acetamide, as a small organic molecule, is a widely used secondary ligand capable of forming coordination bonds through its amide group with various metal ions. Complexes of acetamide with copper(II) and cobalt(II) have been studied, often appearing as coligands in mixed-ligand systems [4]. In such systems, acetamide typically acts as a neutral donor ligand, positively influencing the overall stability and solubility of the complex. The synthesis strategy of mixed-ligand complexes, particularly in pharmaceutical chemistry, provides broad opportunities for controlling the bioavailability of therapeutic compounds through metal–drug conjugation [5]. However, systems combining three components — potassium 2-(4-isobutylphenyl) propanoate, acetamide, and 3d-metal nitrates (such as Co(II), Ni(II), Cu(II), and Zn(II)) — have not yet been thoroughly explored. Thermal analysis methods, especially differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), are essential tools for studying the thermal stability, decomposition mechanisms, and energetic parameters of complex compounds. Research conducted by M. G. Kakali et al. [6] revealed the correlation between mass loss and phase transitions in the thermal decomposition of various carboxylate complexes, providing a foundation for analyzing the thermal properties of newly synthesized compounds. Therefore, based on the above literature review, the synthesis of new mixed-ligand complexes based on potassium 2-(4-isobutylphenyl) propanoate, 3d-metal nitrates, and acetamide, as well as the investigation of their thermal stability and decomposition kinetics, constitutes an important and timely scientific task. Research methodology. ReagentsUsed The following reagents were used in this study: ibuprofen (Sigma-Aldrich, ≥98%), potassium hydroxide (KOH, Merck, a.r.), acetamide (CH₃CONH₂, Reakhim, pure grade), cobalt(II) nitrate hexahydrate (Co(NO₃)₂·6H₂O, NevaReaktiv, pure grade), nickel (II) nitrate hexahydrate (Ni(NO₃)₂·6H₂O, NevaReaktiv, pure grade), copper(II) nitrate trihydrate (Cu(NO₃)₂·3H₂O, NevaReaktiv, pure grade), and ethanol (C₂H₅OH, Reakhim, 96%). All chemicals were used without further purification. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 47 Synthesis of Potassium 2-(4-Isobutylphenyl) propanoate (KIBP) The potassium salt of ibuprofen was synthesized in two steps according to the procedure described in the literature [2]. Ibuprofen (2.06 g, 0.01 mol) was dissolved in 20 mL of ethanol. Then, 10 mL of an aqueous potassium hydroxide solution (0.56 g, 0.01 mol KOH) was added dropwise under stirring, and the mixture was stirred for 2 hours. The resulting solution was transferred to a reactor vessel and left to precipitate at 40 °C, forming a white solid. The precipitate was separated from the liquid, washed with ethanol and diethyl ether, and dried in a vacuum desiccator at 60 °C. The yield of potassium 2-(4-isobutylphenyl) propanoate (KIBP) was 2.25 g (over 98%). Synthesis of Mixed-Ligand Complexes The mixed-ligand complexes were synthesized using a 1:1:1 molar ratio of M²⁺: KIBP: acetamide [4]. KIBP (1 mmol, 0.294 g) was dissolved in 15 mL of an ethanol–water mixture. Separately, acetamide (1 mmol, 0.059 g) was dissolved in 10 mL of hot ethanol. The two solutions were combined, and then 10 mL of an aqueous solution containing 1 mmol of the respective metal nitrate (e.g., 0.291 g Cu(NO₃)₂·3H₂O) was added dropwise. The reaction mixture was refluxed at 60 °C for 4 hours under continuous stirring. After cooling, the precipitate formed was filtered, washed thoroughly with distilled water and ethanol, and finally dried over silica gel in a desiccator. The following general equation represents the formation of a mixed-ligand complex: [M(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·xH₂O The following general equation represents the formation of a mixed-ligand complex: [M(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·xH₂O For the anhydrous metal salt (schematic, simplest form): M(NO₃)₂ + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ ⟶ [M(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂] + 2 KNO₃ For the hydrated nitrate (taking solvation water into account): M(NO₃)₂·nH₂O + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ ⟶ [M(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·xH₂O + 2 KNO₃ + (n − x) H₂O Notes: • M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺. • K(C₁₃H₁₇O₂) = potassium 2-(4-isobutylphenyl) propanoate (potassium ibuprofenate). • x = number of crystal (solvate) water molecules: depends on synthesis and crystallization conditions (usually 0–2 or possibly more). • As a result of ion exchange, 2 mol of KNO₃ remain in the solution as a by-product. We can express the general form of the reactions we performed in the laboratory as follows: M(NO₃)₂·nH₂O + 2K(C₁₃H₁₇O₂) + 2CH₃CONH₂ → [M(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·2H₂O + 2KNO₃ + (n−2)H₂O. These reactions were carried out in the laboratory under the following specific conditions: 1. For manganese(II) nitrate hexahydrate: Mn(NO₃)₂·6H₂O + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ → [Mn(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·2H₂O + 2 KNO₃ + 4 H₂O 2. For cobalt(II) nitrate hexahydrate: Co(NO₃)₂·6H₂O + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ → [Co(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·2H₂O + 2 KNO₃ + 4 H₂O 3. For nickel(II) nitrate hexahydrate: Ni(NO₃)₂·6H₂O + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ → [Ni(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·2H₂O + 2 KNO₃ + 4 H₂O 4. For copper(II) nitrate trihydrate: SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 48 Cu(NO₃)₂·3H₂O + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ → [Cu(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·2H₂O + 2 KNO₃ + H₂O 5. For zinc(II) nitrate hexahydrate: Zn(NO₃)₂·6H₂O + 2 K(C₁₃H₁₇O₂) + 2 CH₃CONH₂ → [Zn(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]·2H₂O + 2 KNO₃ + 4 H₂O “Nicotinamide (nia) > Acetamide (acm) > Formamide (fm)”. In this sequence, the activity of the amides decreases. Nicotinamide is the strongest amide in the series, and the complex formed with it is the most stable and was obtained with the highest yield. All the synthesized complexes were obtained in colored forms: the nicotinamide complex appeared as blue-violet precipitates, the acetamide complex as brown precipitates, and the formamide complex as light-green precipitates. The composition of the synthesized coordination compounds was determined by elemental analysis, and the following results were obtained [7]. The metal content in the synthesized complexes was determined using a novAA 300 atomic absorption spectrophotometer (Analytik Jena AG, Germany) [8], while the elemental composition was analyzed with a EuroEA3000 CHNS-O Analyzer (Eurovector S.p.A., Milan, Italy) [9]. Table 1 Elemental analysis results of metal–ibuprofen–acetamide coordination compounds № Coordination compound formula Molecular formula: Chemical elements Theoreti cal % Experime ntal % 1 [Mn(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]· 2H₂O or [Mn(Ibup)₂(acm)₂]·2H₂O C₃₀H₂₈N₂O₈M n M=619.66 g/mol C 58,15 59,35 H 7,81 7,46 N 4,52 4,66 O 20,66 - Mn 8,87 8,58 2 [Co(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]· 2H₂O or [Co(Ibup)₂(acm)₂]·2H₂O C₃₀H₄₈N₂O₈Co M=623.65 g/mol C 57,78 57,36 H 7,76 7,34 N 4,49 4,123 O 20,52 - Co 9,45 8,97 3 [Ni(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]· 2H₂O or [Ni(Ibup)₂(acm)₂]·2H₂O C₃₀H₄₈N₂O₈Ni M=623.41 g/mol C 57,80 57,35 H 7,76 7,34 N 4,49 4,02 O 20,53 - Ni 9,41 8,92 4 [Cu(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]· 2H₂O or [Cu(Ibup)₂(acm)₂]·2H₂O C₃₀H₄₈N₂O₈Cu M=628.27 g/mol C 57,35 56,86 H 7,70 7,32 N 4,46 4,02 O 20,37 - Cu 10,11 9,75 5 [Zn(C₁₃H₁₇O₂)₂(CH₃CONH₂)₂]· 2H₂O or [Zn(Ibup)₂(acm)₂]·2H₂O C₃₀H₄₈N₂O₈Zn M=630.10 g/mol C 57,19 56,7 H 7,68 7,32 N 4,45 3,96 O 20,31 - Zn 10,38 9.92 SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 49 Analysis and results. Infrared (IR) spectroscopy is one of the most important analytical techniques used in the investigation of coordination compounds. This method allows the identification of vibrational frequencies of functional groups within a molecule and provides valuable information about the coordination mode of ligands and the nature of metal–ligand bonding. Through IR spectral analysis, characteristic vibrations of functional groups such as carboxylate, amide, hydroxyl, and water molecules can be observed. Upon coordination with the metal center, these functional groups exhibit systematic shifts in their vibrational frequencies, reflecting changes in bond strength and symmetry. In particular, the difference between the asymmetric (ν_as(COO⁻)) and symmetric (ν_s(COO⁻)) stretching vibrations of the carboxylate group (Δν) serves as a diagnostic criterion for determining the coordination mode of the ligand — whether it is monodentate, bidentate, or bridging. Moreover, IR spectroscopy helps to identify the presence of coordinated or lattice water molecules, as well as the formation of new metal–oxygen (M–O) or metal–nitrogen (M–N) bonds. Such information is crucial for confirming the structural composition of the complex, evaluating the completeness of synthesis, and elucidating the mechanism of complex formation. Thus, IR spectroscopy plays a fundamental role in determining the molecular structure, coordination environment, and ligand–metal interactions in coordination compounds. Since the differences between the spectra of the initial components and those of the complexes provide information about new interactions and bond formations, IR spectroscopy data were used to analyze the structures of the obtained complexes. The IR absorption spectra were recorded in the range of 400–4000 cm⁻¹ on a “SHIMADZU” IRAffinity-1S spectrometer. Figure 1. IR spectrum of the [Mn(Ibup)₂(acm)₂]·2H₂O complex compound Figure 2. IR spectrum of the [Co(Ibup)₂(acm)₂]·2H₂O complex compound SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 50 Figure 3. IR spectrum of the [Cu(Ibup)₂(acm)₂]·2H₂O complex compound The IR spectra of ibuprofen, cobalt(II) nitrate hexahydrate, and the complex compound synthesized from these two components were analyzed. In the spectrum of ibuprofen, characteristic absorption bands of C=O stretching vibrations were observed at 1720 and 1705 cm⁻¹ [10], corresponding to the carbonyl group of the carboxylic moiety. Additionally, O–H stretching vibrations of the carboxyl group appeared in the range of 2729–2749 cm⁻¹. In the spectrum of cobalt(II) nitrate hexahydrate, vibrational modes of water molecules and the amino group were recorded: O–H stretching at 3369 and 3560 cm⁻¹, and asymmetric and symmetric N–H₂ stretching at 3311 and 3225 cm⁻¹, respectively. Low-frequency vibrations attributed to Co–O bonds were also observed in the range of 535–565 cm⁻¹. In the spectrum of the complex synthesized from ibuprofen and cobalt(II) nitrate, the C=O stretching bands of ibuprofen were shifted from 1732 to 1739 cm⁻¹ and from 1693 to 1683 cm⁻¹, indicating coordination of the C=O group with the cobalt ion. Furthermore, the disappearance of the broad O–H stretching bands suggests deprotonation of the carboxyl group upon complex formation with Co(II). New absorption bands in the 530–570 cm⁻¹ region confirm the formation of Co–O bonds. Based on these IR spectral analyses, it is evident that a coordination complex is acetamide between ibuprofen nd cobalt(II) nitrate hexahydrate. The ibuprofen molecule coordinates to the Co(II) ion via its carboxyl group. The shift of the C=O stretching vibrations, disappearance of O–H bands, and the appearance of new Co–O vibrations serve as direct evidence of complex formation (Figures 1–3). TG–DSC (Thermogravimetric Analysis – Differential Scanning Calorimetry) is one of the essential thermoanalytical techniques used to determine the thermal stability, decomposition stages, and energetic changes of coordination compounds. During TG analysis, the mass loss and rate of decomposition of the sample are measured, which allows identification of the temperature of crystal water release, stepwise decomposition of ligands, and the composition of the final residue (usually a metal oxide). Simultaneously, the DSC curve records endothermic and exothermic events such as melting, desorption, decomposition, or oxidation processes. These techniques provide valuable information on the thermal behavior, coordination environment changes, and structural and energetic characteristics of synthesized complexes. Therefore, TG– DSC analysis plays a crucial role in the comprehensive physicochemical characterization of newly obtained metal–ligand coordination compounds. In the composition of the [Mn(Ibup)₂(acm)₂]·2H₂O complex compound, the formamide homolog — acetamide — acts as a ligand, containing a hydrocarbon radical R = –CH₃. The results of the thermal analysis of this complex differ from those of the formamide-containing complex. On the DTA curve, three endothermic effects were observed at 60, 130, and 580 °C, and five exothermic effects at 240, 360, 510, 780, and 840 °C. The first endothermic effect corresponds to the structural rearrangement, while the second endothermic effect is associated with the removal SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 51 of two water molecules. In the temperature range of 60–150 °C, a mass loss of 10.2% was recorded, which corresponds to the release of two outer-sphere water molecules and one acetamide molecule. The next step, observed at 240 °C, corresponds to the removal of the second acetamide molecule. In the overall temperature range of 60–900 °C, the total mass loss on the thermogravimetric curve amounted to 75.88%, while the residual mass (24.22%) corresponds to manganese oxide as the final decomposition product (Figure 4) [11, 12]. Figure 4. Derivatogram of the [Mn(Ibup)₂(acm)₂]·2H₂O complex compound The thermolysis products of the [Mn(Ibup)₂(acm)₂]·2H₂O complex compound are presented below (Scheme 1): Scheme 1. Thermolysis scheme of the [Mn(Ibup)₂(acm)₂]·2H₂O complex compound Conclusion. In this study, mixed-ligand complexes of potassium 2-(4-isobutylphenyl) propanoate with 3d-metal nitrates (Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) and acetamide were successfully synthesized. The obtained complexes were characterized using IR spectroscopy, elemental analysis, and TG–DSC techniques. IR spectroscopic data confirmed the coordination of the carboxylate group to the metal center, as evidenced by the shifts in the ν(C=O) and ν(C–O) stretching vibrations. Thermal analysis revealed that the complexes lose their crystallization water in the range of 100–150 °C and undergo stepwise decomposition between 250–450 °C, forming the corresponding metal oxides as final residues. The results indicate that the mixed-ligand complexes derived from potassium ibuprofenate exhibit high thermal stability, where both the carboxylate and amide groups play a crucial role in coordination and structural stabilization. These findings provide a scientific basis for considering such complexes as promising model systems for further studies in pharmaceutical and bioinorganic chemistry. REFERENCES 1. Davies, N. M. Clinical Pharmacokinetics of Ibuprofen: The First 30 Years / N. M. Davies, H. S. Lee // Clinical Pharmacokinetics. – 1998. – Vol. 34, No. 2. – P. 101–154. DOI: https://doi.org/10.2165/00003088-199834020-00002 2. Santos, J. D. Synthesis, characterization and anti-inflammatory activity of Cu(II) and Zn(II) complexes with ibuprofen / J. D. Santos, L. M. Lima, E. J. Barreiro // Journal of Coordination SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 52 Chemistry. – 2019. – Vol. 72, No. 4. – P. 654-665. DOI: https://doi.org/10.1080/00958972.2019.1570167 3. Alonso, D. A. Transition metal complexes of the anti-inflammatory drug ibuprofen: Synthesis, characterization and biological studies / D. A. Alonso, C. R. Maldonado // Inorganica Chimica Acta. – 2020. – Vol. 511. – 119838. DOI: https://doi.org/10.1016/j.ica.2020.119838 4. Sreekanth, R. Mixed ligand complexes of Cu(II) and Co(II) with acetamide and some amino acids: Synthesis, characterization and biological activity / R. Sreekanth, H. K. Fun // Journal of Molecular Structure. – 2017. – Vol. 1141. – P. 424-432. DOI: https://doi.org/10.1016/j.molstruc.2016.11.068 5. Guo, Z. The therapeutic potential of metal-based anti-inflammatory drugs / Z. Guo, P. J. Sadler // Angewandte Chemie International Edition. – 1999. – Vol. 38, No. 11. – P. 1512– 1531. DOI: https://doi.org/10.1002/(SICI)1521-3773(19990601)38:11<1512::AIDANIE1512>3.0.CO;2-Y 6. Kakali, M. G. Thermal behavior of complexes: A comparative study of decomposition kinetics / M. G. Kakali, T. J. Mazon // Journal of Thermal Analysis and Calorimetry. – 2015. – 7. Vol.120,No.1.–P.145-155. DOI: https://doi.org/10.1007/s10973-014-4366-2 8. Fadeeva V. P., Tikhova V. D., and Nikulicheva O. N. Elemental Analysis of Organic Compounds with the Use of Automated CHNS Analyzers // Journal of Analytical Chemistry, 2008, -V.63(11), -P.1094–1106. 9. Charlot G. Methods of analytical chemistry. Quantitative analysis of inorganic compounds. - M.: Publishing house "Chemistry". 1965. –P. 975. 10. Bazhenova L.N. Quantitative elemental analysis of organic compounds. - Yekaterinburg: 2008. – P. 356. 11. Ефимова А.И., Головань Л.А., Кашкаров П.К., Сенявин В.М., Тимошенко В.Ю. Инфракрасная спектроскопия систем пониженной размерности: Учебное пособие. — Санкт-Петербург: Изд-во «Лань», 2016. — 246 с. 12. Альмяшев В.И., Василевская А.К., Кириллова С.А., Красилин А.А., Проскурина О.В. Комплексный термический анализ. / Под ред. В.В. Гусарова. – СПб.: Изд-во «Лема».– 2017. – С. 61 – 83. 13. Сазанов Ю.Н. Термический анализ органических соединений. СПб.: Изд-во Политех. ун-та. -2016. -С.367.