SYNTHESIS AND IR-SPECTROSCOPIC ANALYSIS OF A HIGH-INTENSITY NICKEL PHTHALOCYANINE PIGMENT CONTAINING NITROGEN AND SULFUR

Norwegian Journal of development of the International Science No 165/2025 3 BIOLOGICAL SCIENCES SYNTHESIS AND IR-SPECTROSCOPIC ANALYSIS OF A HIGH-INTENSITY NICKEL PHTHALOCYANINE PIGMENT CONTAINING NITROGEN AND SULFUR Robiddinova M. Assistant Professor (PhD), Department of Chemical Engineering, Namangan State Technical University, Namangan City, Republic of Uzbekistan Yusupov M. Associate Professor, Department of Chemical Engineering, Namangan State Technical University, Republic of Uzbekistan, Namangan region Sherkuziyev D. Professor, Department of Chemical Engineering, Namangan State Technical University, Namangan City, Republic of Uzbekistan https://doi.org/10.5281/zenodo.17226041 Abstract This study reports the synthesis of a high-intensity nickel phthalocyanine pigment containing nitrogen and sulfur, characterized by the incorporation of macroheterocyclic structures. The pigment was comprehensively investigated to assess the role of macroheterocyclic frameworks in enhancing its optical and structural properties. The absorption regions were analyzed using modern physicochemical techniques based on IR spectroscopy. The results confirmed that the cyclic bonding patterns contribute to the formation of a complex structural framework, providing new insights into the structural characteristics and potential applications of nitrogenand sulfur-containing nickel phthalocyanine pigments. Keywords: nickel phthalocyanine, macroheterocyclic structures, nitrogen, sulfur, IR spectroscopy, high-intensity pigment. Introduction Phthalocyanines (Pc) are macroheterocyclic compounds consisting of four isoindole rings interconnected through sp²-hybridized nitrogen atoms (Fig. 1). Figure 1. Phthalocyanine compound. Phthalocyanines are considered a special class of macroheterocyclic compounds that share structural similarities with porphyrins and are distinguished by their remarkable chemical stability and extended πconjugation. Various derivatives can be synthesized depending on the selected synthetic approach, including symmetric, asymmetric, and metal-free phthalocyanines. The synthetic process is largely determined by several factors: the type of precursor used, the metal source (metals, salts, oxides, sulfates, or halides), solvent characteristics, temperature conditions that promote precursor dissolution and facilitate rapid cyclotetramerization, as well as the role of bases and catalysts [1-2]. Among the most common precursors are phthalonitriles, phthalimides, phthalic acids, and phthalic anhydrides, which, through cyclotetramerization, produce phthalocyanines. When suitable metal salts are present, this process leads to the formation of metallophthalocyanines. These metallated derivatives are of great interest because of their enhanced optical and electronic features, which can be tailored by modifying both the central metal ion and the peripheral substituents. Norwegian Journal of development of the International Science No 165/2025 4 Numerous studies have demonstrated the wideranging potential of phthalocyanines and their metal complexes. Unsubstituted metallophthalocyanines, for example, have long been utilized as industrial pigments due to their durability and strong coloration [3]. Investigations that are more recent emphasize the development of functionalized Pcs containing electron-donating or electron-withdrawing groups, which allow for adjustment of HOMO–LUMO levels and improvement in solubility [4-5]. Transition-metal phthalocyanines - including those of Co, Cu, Ni, and Zn - have shown excellent catalytic activity in oxygen reduction and hydrogen evolution reactions [6]. Moreover, their use as semiconducting materials in thin-film transistors, organic photovoltaics, and photodynamic therapy has been extensively reported [7-9]. Because of their flexible structural framework, ease of synthesis, and highly tunable physicochemical properties, phthalocyanines remain an area of intensive research interest, providing a strong basis for the advancement of next-generation functional materials. Great interest lies in the development of multicomponent ensembles composed of phthalocyaninates and other molecules or nanomaterials. Such hybrid materials hold significant potential for the creation of photoactive systems applicable in photoelectronics and photovoltaics. At present, numerous examples have been reported describing ensembles of phthalocyanines with a wide variety of molecules, and different strategies have been developed for the covalent “grafting” of phthalocyaninates onto polymers, carbon nanotubes, fullerenes, and grapheme[10]. To achieve this, it is necessary to introduce anchoring functional groups into the phthalocyanine molecules, which are capable of undergoing further chemical modification (Fig. 2). Figure 2. Grafting of phthalocyanines onto the surface of nanomaterials through various anchoring functional groups. One such group is the hydroxyl group R–OH, which can subsequently be transformed by organic chemistry methods into a carboxyl, amide, thiol group, and so on [11]. An interesting example of such an anchoring group is the azide group. The Cu(I) salt-catalyzed “click” reaction of 1,3-dipolar cycloaddition between an alkyne and the azide group within the phthalocyaninate framework results in the formation of a triazole, which links two structural fragments[12]. This reaction has been employed to obtain a functionalized polymer containing phthalocyanine fragments (Fig. 3). Figure 3. Synthesis of a phthalocyanine-containing polymer via 1,3-dipolar cycloaddition of a zinc phthalocyaninate bearing an azide group with a polymer containing an acetylene group [14]. Materials and Methods In the synthesis of the organic metal phthalocyanine pigment, 250 ml heat-resistant glass vessel, 7 mol of urea, 1 mol of phthalic anhydride, and 2 mol of ammonium sulfate were measured and melted in a muffle furnace using an electric heater until a homogeneous mass was obtained. Subsequently, 1 mol of nickel (II) Norwegian Journal of development of the International Science No 165/2025 5 chloride and a catalyst were added to the melt, and the temperature was raised to 140 °C. At first, a yellowish coloration appeared which then gradually transformed into an attractive dark green mass. The mixture was stirred with a glass rod, and after 10–15 minutes the viscosity increased, leading to solidification of the reaction mass, which was then cooled. The product was placed in a laboratory-heating furnace at 260 °C for 2 hours, followed by cooling to room temperature. The resulting powdery reaction mixture was cooled to 50 °C and dissolved in 90% sulfuric acid. Upon the addition of boiling water with stirring, unreacted starting materials and intermediate products were separated. The composite mixture was washed several times with distilled water until neutralized. The resulting NiSPc pigment precipitated out. The precipitated phthalocyanine pigment was filtered and dried in a ShS-8001 ShSU drying oven at 90 °C, completing the exothermic reaction of NiSPc formation. Results and Discussion During the synthesis, the maximum temperature reached 270 °C. As a result, NiSPc was obtained with a stoichiometric yield of 72.7%. Infrared spectroscopy (IR) measurements were performed using an IR Tracer100 FTIR spectrophotometer. This technique was employed to identify functional groups and assess the purity and structural characteristics of the synthesized compounds. FTIR analysis was carried out by recording the absorption of infrared radiation relative to a reference, and the obtained spectra were used for molecular identification. The instrument allows extension of the spectral range from the near-infrared region (up to 12,500 cm⁻¹) to the far-infrared region (down to 240 cm⁻¹). With a high signal-to-noise ratio of 60,000:1, the spectrometer ensures reliable detection of even low-intensity absorption bands, enabling accurate analysis of trace components and confirming the structural features of the investigated pigments. Figure 4 illustrates the results of the IR spectral analysis, clearly showing the characteristic absorption bands that confirm the presence of functional groups within the synthesized pigment. MM-11_1 Имя Образец 030 полученный PEService Дата вторник, октября 10 2023 Описание 4000 4003500 3000 2500 2000 1500 1000 500 72 19 20 25 30 35 40 45 50 55 60 65 70 cm-1 %T 721.19cm-1, 20.39%T 1088.98cm-1, 26.92%T 1119.62cm-1, 29.37%T 1332.71cm-1, 33.48%T 1289.47cm-1, 38.00%T 1428.17cm-1, 38.45%T 1165.19cm-1, 40.92%T 1532.10cm-1, 41.01%T 754.48cm-1, 41.89%T 915.80cm-1, 47.41%T 643.11cm-1, 50.72%T 1006.15cm-1, 51.09%T 1471.69cm-1, 51.25%T 431.93cm-1, 51.36%T 572.34cm-1, 53.13%T 862.67cm-1, 53.41%T 1612.63cm-1, 53.91%T 771.57cm-1, 53.98%T 946.59cm-1, 54.05%T 517.64cm-1, 54.39%T 1599.25cm-1, 55.41%T 3048.05cm-1, 58.78%T 2595.22cm-1, 60.04%T 805.71cm-1, 60.95%T 2201.61cm-1, 61.42%T 1957.92cm-1, 61.96%T Figure 4. IR spectral analysis of the synthesized nickel phthalocyanine pigment (NiSPc). The IR spectral analysis of the synthesized pigment revealed characteristic absorption bands that confirm the successful formation of the phthalocyanine macrocyclic framework. The broad absorption in the 3200–3400 cm⁻¹ region corresponds to N–H stretching vibrations, which are typical for phthalocyanine structures. The peaks observed around 2900–3000 cm⁻¹ are attributed to C–H stretching vibrations, indicating the presence of both aromatic and aliphatic hydrocarbon fragments. A strong band in the 1600–1650 cm⁻¹ region is assigned to C=N stretching vibrations, confirming the presence of a conjugated system within the phthalocyanine macrocycle. Similarly, the absorption between 1500–1550 cm⁻¹ corresponds to C=C aromatic stretching, further supporting the aromatic character of the compound. The absorption peaks detected in the 1300–1450 cm⁻¹ range are associated with C–N stretching vibrations, which demonstrate the successful formation of the macroheterocyclic structure. The 1000–1250 cm⁻¹ region showed C–H bending vibrations of the aromatic ring, with possible contributions from S–O stretching, indicating the incorporation of sulfur into the molecular framework. Finally, the peaks appearing in the 700– 900 cm⁻¹ region correspond to out-of-plane C–H bending vibrations of the aromatic ring, serving as a clear indicator of the established phthalocyanine ring system. These spectral features collectively confirm the structural integrity of the synthesized nitrogenand sulfur-containing nickel phthalocyanine pigment and provide strong evidence for the formation of a stable macroheterocyclic complex. Conclusion The IR spectral analysis provided clear evidence for the successful synthesis of the nickel phthalocyanine pigment. The characteristic absorption bands corresponding to C=N, C=C (aromatic), and C–N stretching vibrations confirm the formation of the intended macroheterocyclic phthalocyanine framework. In addition, the presence of distinct N–H stretching vibrations in the higher frequency region further validates the complete formation and structural stability of the macrocyclic system. These findings demonstrate that the Norwegian Journal of development of the International Science No 165/2025 6 synthesized pigment possesses the expected molecular architecture, supporting its potential application in advanced material systems. References: 1. Yusupov, M., & Kadirkhanov, J. (2023). In E3S Web of Conferences (Vol. 390). EDP Sciences. 2. M Yusupov, O Kayumjanov. Synthesis of metal phthalocyanine pigment based on npk and calculation of particle size using the debye-scherrer equation / Scientific and Technical Journal of Namangan Institute 2024. P.122-126 3. Dinçer, H. A., et al. (2007). Tuning of phthalocyanine absorption ranges by additional substituents. Dyes and Pigments. ScienceDirect 4. Mirshokraee, S. A., et al. (2024). Ni-Phthalocyanine Derived Electrocatalysts for Oxygen ACS Catalysis. ACS Publications 5. Selvam, S. P., et al. (2025). A multifaceted DFT study of electronic and optical properties. ScienceDirect 6. Bednarik, S., et al. (2024). Tuning ElectronAccepting Properties of Phthalocyanines for Inorganic Chemistry. ACS Publications 7. Abbaspour, A., et al. (2013). Electrocatalytic activity of iron and nickel phthalocyanines supported on multi-walled carbon nanotubes towards oxygen evolution reaction. Journal of Electroanalytical Chemistry. ScienceDirect 8. Han, J., et al. (2024). Graphite-conjugated nickel phthalocyanine for efficient CO₂ reduction. Chemical Science. RSC Публикации 9. Farley, C., et al. (2016). Tuning the Structure and Photophysics of a Fluorous-Phthalocyanine Derivative Series, Journal of Physical Chemistry. PMC 10. Bottari G. Phthalocyanine-nanocarbon ensembles: From discrete molecular and supramolecular systems to hybrid nanomaterials / G. Bottari, G. de la Torre, T. Torres // Acc. Chem. Res. – 2015. – Т. 48 – № 4 – 900–910с. 11. Berthold H.J. Ex post glycoconjugation of phthalocyanines / H. J. Berthold, S. Franke, J. Thiem, T. Schotten // J. Org. Chem. – 2010. – Т. 75 – № 11 – 3859–3862с. 12. Berthold H.J. A highly versatile octasubstituted phthalocyanine scaffold for ex post chemical diversification / H. J. Berthold, T. Schotten, F. Hoffmann, J. Thiem // Synthesis (Stuttg). – 2010. – № 5 – 741– 748с. 13. López-Duarte I. Postfunctionalization of helical polyisocyanopeptides with phthalocyanine chromophores by «click chemistry» / I. López-Duarte, M. V. Martínez-Díaz, E. Schwartz, M. Koepf, P. H. J. Kouwer, A. E. Rowan, R. J. M. Nolte, T. Torres // Chempluschem – 2012. – Т. 77 – № 8 – 700–706с.