THERMAL ANALYSIS STUDY OF COPPER AND CALCIUM-CONTAINING PHTHALOCYANINE PIGMENT

ABSTRACT

This article presents the results of a study on the synthesis of a new organic pigment-copper-calcium phthalocyanine that incorporates macroheterocyclic compounds. The research focuses on examining how the methods of pigment synthesis in both liquid and solid phases influence its physicochemical properties, intensity, and thermal stability. The article includes the chemical formula of the pigment and outlines its potential application areas. To evaluate the thermal stability of this highly intense organic pigment, thermal analyses were performed using a LabSys Evo instrument manufactured by Setaram (France). This enabled comparison with a structurally related compound, copper phthalocyanine. During the study, exothermic and endothermic processes were observed in the temperature range of 25 to 500 °C, and data were obtained regarding the mass loss of the pigment during heating. The results indicate that the synthesized organic pigment demonstrates high thermal resistance and color intensity, primarily attributed to the presence of phosphorus-containing compounds. This research provides a valuable scientific foundation for the practical application of the newly synthesized organic material.

АННОТАЦИЯ

В данной статье представлены результаты исследования по синтезу нового органического пигмента медно-кальциевого фталоцианина, содержащего макрогетероциклические соединения. В работе рассматривается влияние методов синтеза пигмента в жидкой и твёрдой фазах на его физико-химические свойства, интенсивность окраски и термическую стабильность. В статье приводится химическая формула пигмента, а также обозначены возможные области его применения. Для оценки термической стабильности данного высокоинтенсивного органического пигмента были проведены термические анализы с использованием прибора LabSys Evo Setaram, произведённого французской компанией. Это позволило провести сравнение с близким по структуре соединением - медным фталоцианином. В ходе исследования в диапазоне температур от 25 до 500 °C были зафиксированы экзотермические и эндотермические процессы, а также получены данные об изменении массы пигмента при нагревании. Результаты показали, что синтезированный органический пигмент обладает высокой термостойкостью и интенсивностью окраски, что в первую очередь объясняется присутствием соединений фосфора. Настоящее исследование создаёт прочную научную основу для практического применения вновь синтезированного органического материала.

Keywords: physicochemical, phthalocyanine, phthalic anhydride, derivatogram, calcium chloride, exothermic and endothermic.

Ключевые слова: физико-химические свойства, фталоцианин, фталевый ангидрид, дериватограмма, хлорид кальция, экзотермический и эндотермический процессы.

Introduction

Phthalocyanines  can form with many metals. The most common metals that form complexes with phthalocyanines include aluminum, zinc, copper, iron, cobalt, nickel, and magnesium [1]. However, to date, phthalocyanine complexes are known with nearly all metals from the periodic table. When examining the electronic structure of metal phthalocyanine complexes, it has been established that for complexes with metals that do not possess unpaired d-electrons, there is no exchange interaction between the metal’s electrons and the π-electrons of the phthalocyanine macro heterocycle. As a result, long-lived excited triplet states are generated. This phenomenon makes such metal complexes promising candidates for photocatalytic applications [2-3].

The electronic absorption spectra of metal phthalocyanine complexes are among their most important characteristics. These spectra reveal the structure and reflect the intramolecular energy state of the molecules [4]. The electronic transition in phthalocyanine metal complexes corresponds to an absorption band at 660–670 nm (Q-band). The electronic-vibrational structure of the spectrum is typically not observed for phthalocyanines.

Additionally, the inclusion of more than seventy different metal ions into the central cavity provides opportunities to enhance physical properties tailored to specific applications. Among these derivatives, copper phthalocyanine is particularly noteworthy, as it exhibits exceptional qualities such as lightfastness, coloring power, hiding power, and resistance to both alkali and acid, making it a significant member of the dye family [5-6].

The introduction of the cis-(phenoxy phenyl) diazenylbenzoic acid residue at different positions (Figure 1) led to changes in the spectral properties of the zinc phthalocyanine complex [7]. The electronic spectra of metal complexes 1 and 3 are characteristic of unsubstituted complexes, whereas for compounds 2 and 4, a change in the shape of the Q-band was observed, which is typical of H-aggregates. Additionally, compounds 3 and 4, unlike compounds 1 and 2, showed higher solubility in DMSO, DMF, water, methanol, and ethanol. This is likely due to the incorporation of four octa (cis-phenoxy phenyl) diazenylbenzoic acid residues into the macrocyclic ring.

Figure 1. Derivatives of the zinc phthalocyanine complex containing octa (phenoxy phenyl) diazenylbenzoic acid residues

Materials and Methods

In our approach to synthesizing the organic metal phthalocyanine pigment, we thoughtfully combined 15 g of phthalic anhydride, 25 g of anhydrous copper (II) sulfate, 11 g of calcium chloride, 90 g of urea, 69 g of N.P.K. fertilizer, and a suitable catalyst within a high-temperature-resistant 400 ml beaker. The ingredients were carefully stirred at a lower temperature until a complete dissolution was achieved. We then proceeded with the reaction at temperatures ranging from 200 to 220 °C, aiming for a uniform and homogeneous system. The result of this meticulously conducted reaction was a blue-colored heavy pigment. Following the reaction, the mixture was allowed to cool to room temperature and then placed in a vacuum oven for 120 minutes to ensure proper heating. Upon removal from the oven, the pigment was cooled further and subsequently treated with sulfuric acid to remove any unreacted components. Concentrated sulfuric acid was introduced slowly along the walls of the beaker, and once a homogeneous substance was formed, boiling water was added. This procedure effectively rendered the pigment medium acidic, which was then neutralized by washing with distilled water. Following filtration, the pigment was dried in a drying oven at a controlled temperature between 60 and 80 °C. The newly synthesized pigment is distinguished by its remarkable properties, including high heat resistance, outstanding durability against sunlight, and vibrant coloring capabilities, which significantly enhance its potential applications. Additionally, we are pleased to report that the yield of the pigment achieved at the conclusion of the reaction was an impressive 80%.

Results and Discussion

Figure 2. Derivatogram of the copper calcium pigment

The thermal properties of the CuCaPc (copper–calcium phthalocyanine) pigment have been examined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The findings suggest that as the temperature increases, the sample undergoes several stages of weight loss. The initial weight loss was identified at 25.84 °C, representing 0.787% of the mass, which seems to be associated with the release of adsorbed moisture or low-volatility components. A noteworthy stage of weight loss was recorded at 222.04 °C, resulting in a mass reduction of 17.83%. This stage is likely indicative of the thermal decomposition of unreacted organic components or molecules that did not form stable complexes. Further stages of weight loss of 2.12% at 349.62 °C and 4.14% at 475.15 °C were observed, reflecting partial degradation of the pigment molecule. The most significant decomposition occurred at 626.47 °C, leading to a mass loss of 22.67%, which suggests the breakdown of the core phthalocyanine ring structure. A final weight loss of 9.22% was measured at 763.36 °C, signaling the conclusion of the thermal degradation process. In total, the sample experienced a cumulative weight loss of 56.77%, with the remaining residue accounting for 43.23%. This residue may comprise oxidized forms of copper and calcium, as well as thermally stable carbonaceous remnants. Furthermore, the DSC spectrum exhibited several exothermic peaks, which indicate the decomposition of the pigment components under heat and possible phase transitions. It is noteworthy that the exothermic events observed within the 200–500 °C range may be related to structural transformations of the pigment or the breaking of chemical bonds.

Table 1.

Comparative thermal analysis of the copper calcium phthalocyanine pigment obtained as a control

Received 45 mg of pigment CuCaPc with a total mass

The derivatogram results suggest that the primary mass loss of the synthesized CuCaPc pigment takes place within the temperature range of 150 to 470 °C. Conversely, mass loss observed between 50 and 150 °C appears to be minimal.

Conclusion

A novel type of pigment, known as copper calcium phthalocyanine (CuCaPc), has been synthesized through two distinct methodologies: one involves the liquid phase with dimethyl sulfoxide, while the other utilizes the solid phase through high-temperature heating of the components. The liquid-phase synthesis achieved a commendable pigment yield of 93%; however, it was noted that the intensity was relatively low. In contrast, the solid-phase synthesis yielded a pigment with enhanced intensity, albeit at an 80% yield. A comprehensive comparison has been made between the physicochemical properties of this newly synthesized pigment and those of its closest analogue, copper phthalocyanine. Encouragingly, the new pigment exhibits high thermal stability, and various potential applications in the national economy have been identified for its use.

References:

1. Grin, M.A. Bacteriochlorophyll, and its derivatives: сchemistry and perspectives for cancer therapy / M.A. Grin, A.F. Mironov, A.A. Shtil // Anti-Cancer Agents in Medicinal Chemistry. – 2008. – Vol. 8. – No. 6. – PP. 683-697.
2. Nefedova, I.V. Synthesis and structure of homo- and heteronuclear rare earth element complexes with tetra-15-crown-5-phthalocyanine / I.V. Nefedova, Yu.G. Gorbunova, S.G. Sakharov, A. Yu. Tsivadze // Mend. Comm. – 2006. – Vol. 16. – PP. 67-69.
3. Premkumar, J. Photoreduction of dioxygen to hydrogen peroxide at porphyrins and phthalocyanines adsorbed Nafion membrane / J. Premkumar, R. Ramaraj // J. Molecul. Catal. – 1999. – Vol. 142. – No. 2. – PP. 153-162.
4. Akçay, H.T. Synthesis, electrochemical and Spectro electrochemical properties of peripherally tetra-imidazole substituted metal free and metal-phthalocyanines / H.T. Akçay, R. Bayrak, Ü. Demirbaş, A. Koca, H. Kantekin, I. Değirmencioğlu // Dyes and Pigments. – 2013. – Vol. 96. – No. 2. – PP. 483-494.
5. Yusupov, M., & Kadirkhanov, J. (2023). In E3S Web of Conferences (Vol. 390). EDP Sciences.
6. M. Yusupov, O. Kayumjanov. Synthesis of metal phthalocyanine pigment based on calculation of particle size using the Debye Scherrer equation / Scientific and Technical Journal of Namangan Institute 2024. – PP. 122-126.
7. Ağirtaş, M.S. New water soluble phenoxy phenyl diazinyl benzoic acid substituted phthalocyanine derivatives: Synthesis, antioxidant activities, atypical aggregation behavior and electronic properties / M.S. Ağirtaş, M. Çelebi, S. Gümüş, S. Özdemir, V. Okumuş // Dyes and Pigments. – 2013. – Vol. 99. – No. 2. – PP. 423-431.