RESEARCH OF SOME 3d - COMPLEX COMPOUNDS OF METALS BASED ON 3-ACETYLAMINOTRIAZOLE

ABSTRACT

Complex compounds of 3-acetylaminotriazole with chlorides of Mn (II), Ni(II) and Co(II) were synthesized and their composition and structure were studied using modern physic-chemical methods, such as element (SEM), thermal and IR-spectroscopic analysis. It was found that the ligand 3-acetylaminotriazole is coordinated through the second nitrogen in the triazole ring and oxygen atoms in the acetamide group in the reaction of complex formation.

АННОТАЦИЯ

Синтезированы комплексные соединения 3-ацетиламинотриазола с хлоридами Mn(II), Ni(II) и Co(II) и изученыих состав и строение с использованием современных физико-химических методов, таких как элементный (СЭМ), термический и ИК-спектроскопический анализ. Установлено, что в реакциях комплексообразования лиганд 3-ацетиламинотриазол координируется через второй азот триазольного кольца и атомы кислорода ацетамидной группы.

Keywords: 3-acetylaminotriazole, manganese chloride, ligand, infrared spectroscopy, X-ray structural analysis, thermal analysis.

Ключевые слова: 3-Ацетиламинотриазол, хлорид марганца, лиганд, инфракрасная спектроскопия, рентгеноструктурный анализ, термический анализ.

Introduction.The chemistry of heterocyclic compounds, especially triazole coordination compounds, is of great importance in the field of pharmaceuticals [1]. 3-acetylaminotriazoles is an important class of compounds for elaboration of new drugs[2-3]. They are a source of biologically active complex compounds that replenish the deficiency of essential substances in the body. The presence of nitrogen atoms and an acetamide group in the triazole ring promote to formation of coordination compounds of various structures.Acylated derivatives of 3-amino-1,2,4-triazole with nucleophilic centers are important for practical and fundamental chemistry. Acylation of 3-amino-1,2,4-triazole increases it's ability to coordinate metal ions and ensures the formation of stable complex compounds. In order to study the coordination abilities and properties of obtained as a result of acylation of 3-amino-1,2,4-triazole, synthesis reactions were carried out with salts of intermediate metals at various conditions.

The purpose of this invertigation is the synthesis, study of the structure and properties of  new complexes containing triazole derivatives as a ligand.

Experimental

Materials and physical measurements. 3-acetylaminetriazole was synthesized at the Department of Inorganic Chemistry of the National University of Uzbekistan. Other reagents are of analytical grade and used without purification.

IR spectra of the complexes were recorded on a Perkin Elmer FT-IR spectrophotometer from 4000 to 400 cm^-1 using KBr pellets. Elemental composition of metals, carbon and nitrogen were determined by Japan Jeol JSM-IT200LA analyzer. Thermogravimetric analysis (TGA) experiments were performed on a Shimadzu simultaneous DTG-60A compositional analysis instrument from room temperature to 1000 ^oC under N₂ atmosphere at a heating rate of 5⁰C/min.

The results obtained and their discussion: method for the synthesis of biometallic complex compounds of Mn(II), Ni(II) and Co(II) chlorides with 3-acetylaminotriazole (L) has been elaborated and the composition and structure of the synthesized complex compounds have been studied using modern physico-chemical methods.

Synthesis of complexes of 3-amino 1,2,4-triazole with Mn(II), Ni(II) and Co(II) salts; 0.002 mol of 3-acetylaminotriazole was dissolved in ethanol and stirred in a magnetic stirrer. An aqueous (hot) solution of 0.001 mol of Mn(II), Ni(II) and Co(II) salts was added dropwise and stirred at room temperature for 3 hours. Then the mixture was filtered. The resulting solution was left at room temperature. As a result of slow evaporation of the solvent over several days, colored crystals were formed. The yield of the obtained complex compounds was 73, 71 and 82%, respectively and T_liquid were equaled 258, 252 and 269⁰С. The synthesized complex compounds are soluble in water and ethanol, insoluble in non-polar solvents.

Study of the resulting complexes using SEM. The amounts of elements (carbon, oxygen, nitrogen and metals) in the synthesized complexes were studied using a scanning electron microscope (SEM) (Fig. 1). On the obtained data of the analysis, the composition of elements (mas. %) in the complexes was determined. This made it possible to derive the gross formula of the complexes. Based on the given formulas, the composition of the complexes was determined.

Results and their discussion. To establish the coordination center, IR spectrums of the ligand and the complex based on it were taken (Fig. 2-3). The study of the composition and structure of complex compounds formed by a metal atom with a ligand in the composition of complex compounds requires a number of studies. In this work the IR spectrums of complex compounds of 3-acetylaminotriazole with Mn(II), Ni(II) and Co(II) were studied.

Figure 2. IR spectrum of 3-acetylaminotriazole

The IR spectrums of the ligand and it's complexes with Mn(II), Ni(II) and Co(II) show that the frequency of stretching vibrations of the C=N bond shifts to the high-frequency region by 15-55%. 55 cm^-1 upon transition from L to complexes [4-6]. In addition, as a result of coordination, the asymmetric stretching vibrations of the (C=O) group in complexes other than L decreased from 1624 cm^–1 to 1533–1567 cm^–1. All this showed that the ligand molecule is bidentately coordinated to the central atom through the second nitrogen atom in the ring and the oxygen atoms of the acetamide group. In addition, absorption maximums in the regions of 3331, 3337 and 3346 cm^-1, corresponding to the hydroxyl group (OH), which is not found in the ligand; water molecules are directly associated with the metal and are located in the internal coordination sphere of the complex (table 1). New absorption lines were also observed at 419, 420 and 499 cm^-1, not observed in the L spectrum, associated with the symmetrical stretching vibrations of Me-N bonds.

Figure 3: IR spectrum of the complex [NiL₂(H₂O)_2]Cl₂

Table 1.

Basic assignments of absorption bands in the IR spectrums of the ligand and complexes based on it (cm^-1)

Based on the results of IR spectroscopic analysis, it was established that metal salts form complex compound through the second nitrogen atom in the triazole ring and oxygen atoms in the acetamide group. It was concluded that salts of Mn(II), Ni(II), Co(II) form complex compounds with the 3-acetylaminotriazole ligand in  M:L ratio 1:2 and have an octahedral structure.

In order to determine the thermal stability of complexes of Mn(II), Ni(II), Co(II) salts with 3-acetylaminotriazole and the presence of water molecules in their composition thermal analysis was carried out.

Thermal analysis is carried out in a thermal analytical device - a derivatograph and at the same time the rate of decrease in the mass of the sample, the mass of decomposition of the complex and thermal stability were determined. As a result of thermal analysis the decomposition and liquefaction of complexes, the quality of coordination and non-coordination of ligands, and the final products of complexes are determined [7-8].

The results of thermal analysis: the nature of the thermal effect accompanying the thermal decomposition of compounds, the intervals of temperature impact and their nature, the decrease in mass (mg) are presented figures 4 (a, b).

Figure 4(A). Thermogram of the complex compound [MnL₂(H₂O)₂]Cl₂

The derivatogram of the complex compound [MnL₂(H₂O)₂]Cl₂ consists of 3 curves (DTA, TG, DTGA). Differential thermogravimetric analysis shows that the DTGA curve corresponds to the temperature range of 200-800⁰C and the overall decomposition range. During thermal decomposition of the complex, exothermic effects were observed at 207, 258, 335, 457, 553, 576 and 769⁰C. At heating to 207⁰C, coordination water is released from [MnL₂(H₂O)₂]Cl₂. The endoeffect 258⁰C is associated with liquefaction of the complex; subsequent endoeffect correspond et to the releasation of chlorine ions dissociation of the ligandwas observed at 145⁰C. The presence of exo-effects, corresponded to the general decomposition of the complex, the combustion of thermolysis products and the formation of manganese chloride, and the mass loss of TG in the temperature range 207 – 769⁰C was 72.87%.

Figure 4(B). Thermogram of the complex compound [NiL₂(H₂O)₂]Cl₂

Analysis of the differential thermo gravimetric curves of the [NiL₂(H₂O)₂]Cl₂ complex shows that the DTGA curve corresponds to the temperature range of 205-666°C. Four exothermic effects were observed on the heating curve of the complex at 205, 357, 421 and 666°C, which are explained by the stepwise decomposition of the complex. Lost according to the TG curve at 357°C 46.363%, 4.354 mg of the bulk. MnCl₂ remained as thermolysis product. In conclusion, as a result of derivatographic analysis of complexes, it was found that the mass of the sample, the mass of decomposition of the complexes and their thermal stability have changed with increasing temperature. It was concluded that metal oxides and chlorides remain products of thermolysis.

Conclusion. At studying the composition, structure and properties of the synthesized complex compounds by modern physico-chemical methods, the influence of the nature of metals in the composition of the complex compounds was not observed. It was shown that in the synthesized complex compounds two molecules of 3-acetylaminotriazole are bound and the acidoligands form a stable complex in the monodentate state. It was found that in complex compounds the chlorine molecule is located in the outer sphere. Based on physico-chemical studies it was concluded that the structure of the complex compounds includes metal and 3-acetylaminotriazole in a ratio 1:2, and the structure of the synthesized complex compounds can be presented asfollows:

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