SYNTHESIS AND INVESTIGATION OF MIXED BIOLIGAND COMPLEXES WITH MELAMIN AND GLYCINE

ABSTRACT

In this investigation are mentioned the method of synthesis of ligand complexes of Co (II) acetate with melamine and glycine, the conditions of synthesis and the solid composition of the newly synthesized complex compounds on the basis of modern physical and chemical research methods.

АННОТАЦИЯ

В данном исследовании упоминаются метод синтеза лигандных комплексов ацетата Со (II) с меламином и глицином, условия синтеза и твердый состав вновь синтезированных комплексных соединений на основе современных физико-химических методов исследования.

Keywords: Co (II), melamine, glycine, IR spectroscopy, X-ray phase analysis, thermal analysis, complex, bioligands.

Ключевые слова: Co (II), меламин, глицин, ИК-спектроскопия, рентгенофазовый анализ, термический анализ, комплекс, биолиганды

Importance of the research. Mixed complex compounds consisting of triazine derivatives, amino acids, and d-metal systems have not been virtually explored yet.[1-2] Taking into account the high biological activity of triazine derivatives and amino acids, accomplishing the synthesis of complex compounds with bioelements, investigating their composition and structure areconsidered actual issuessince they are used to solve not only critical problems of coordination compound’s chemistry, but also to create several chemicals that can be applied in practice.

Object and subject of the research. Objects of scientific research are triazine derivative, glycine amino acid and Co (II) acetate salts.[3-5] The subject of research is the synthesis and study of complex compounds of intermediate metals with melamine and glycine, which are derivatives of triazine.

The purpose of the work. Synthesis of ligand complexes of Co (II) acetate mixed with melamine and glycine, study of their composition and structure.[3]

Tasks of the research.

-  Development and synthesis of methods for the synthesis of ligand complexes of Co (II) acetate mixed with melamine and glycine.

- Determination of the composition and structure of mixed ligand complexes synthesized using modern physicochemical methods.

Scientific novelty of the work. Based on the research, a method for the synthesis of a ligand complex of Co (II) acetate mixed with melamine and glycines was developed and new complexes were synthesized [1-4]. The composition and structure of the obtained complex compounds were studied using modern physicochemical methods, differential thermal analysis, X-ray phase analysis, IR spectroscopy and quantum chemical calculation methods, and the initial configuration and individuality of the obtained compounds were determined.

Research methods. Semi-empirical PM 3 calculation method from differential thermal analysis, X-ray phase analysis, IR spectroscopy, quantum chemical calculation methods.[4]

Experimental part. Synthesis of a ligand complex of Co (II) acetate mixed with glycine and melamine [5] 2.13 g of Co(CH₃COO)₂ × 2H₂O was dissolved in a small amount of hot water and a solution containing 1.26 g of melamine (alcohol) and 0.75 g of glycines (aqueous) were added to it (in a 1: 1: 1 mol ratio). The resulting solution was left at low pressure at room temperature in a vacuum desiccator containing anhydrous CaCl₂. As a result of the solvent evaporating slowly over several days, light red crystals were formed and they were quickly filtered, washed with bidistilled water, and the crystal precipitate was placed in a vacuum desiccator containing anhydrous CaCl₂ for drying. The yield of the new complex was 78%. The resulting crystals are stable in air, non-hygroscopic, soluble in hot water, ethanol, poorly soluble in cold water, insoluble in ordinary organic solvents, and liquefaction temperature is 295⁰C [6].

Quantum chemical evaluation of the reactivity of ligands. Quantum chemical analysis of the ligands was performed in the ChemOffise Ultra program. According to the results of quantum chemical calculations, melamine is involved in the formation of the donor-acceptor bond with nitrogen in the cycle, which has the highest negative charge (-0.332 eV). Glycine is involved with the complex-forming ion with nitrogen, which has the highest negative charge in the amino group (-0.326 eV). The obtained theoretical results are then verified on the basis of X-ray phase analysis and analysis of IR spectra of the composition and structure of ligand complexes of the selected metals mixed with melamine and glycine.

Figure 1. L¹ (melamine) Ligand electron density distribution diagram in PM3

Figure 2. Electron density distribution in the melamine molecule

Analysis of thermal stability of the obtained complexes. Thermal analysis was studied the sample weight, mass loss rate and thermal properties when the temperature was increased in a straight line in the systemof Paulik G., Paulik J., Erdey Z. Taken from thermal analysis: the nature of the thermal effects, temperature ranges, and mass reduction are shown in the following figures and table.

Figure 3. Derivatogram of the CoL¹L² (ATs)₂ complex

Study of complexes by IR spectroscopy. An attempt was made to evaluate the electron-conformational changes in the formation of the complex using the method of IR spectroscopy. Melamine obtained as a ligand has several functional groups [7]. Intensive asymmetric vibration frequencies of group C = N are observed in the area of ​​1732 cm^-1, and symmetrical vibration frequencies are observed in 1662 cm^-1. Symmetrical asymmetric, valence and deformation oscillations of the amino group are observed in the areas 3450, 3422, 3193, 1598 cm^-1, respectively. The valence oscillation of the C-N bond is located in the 1357 cm^-1 region. Glycine obtained for the synthesis of mixed ligand complexes has the following functional groups: C = O, NH₂, C-N. In the analysis of the IR spectrum of glycine, intense lines of symmetrical and asymmetric valence oscillations of the carbonyl group are observed in the fields 1670 and 1624 cm^-1. Symmetrical and asymmetric valence oscillations of the aminogroup are observed in the 3348 and 3442 cm^-1 region. The valence oscillation of the C-N bond was observed at 1464 cm^-1.

We can see that the IR spectra of melamine complexes with divalent cobalt, nickel, zinc, copper acetates shift the asymmetric and symmetric valence oscillation frequencies of the C = N group to 6-11 and 26-32 cm^-1 compared to the initial ligand spectrum. From this, complexes are formed by the double electrons of nitrogen in the heterocycle. The symmetrical and asymmetric valence oscillations of the amino group are also subject to change, which were assumed to be related to the redistribution of electrons when coordination compounds are formed. Expansion of the absorption lines in the range of 3000-3400 cm^-1 indicates the presence of moisture in the complexes. The appearance of new oscillation frequencies corresponding to the valence oscillation of the M-N bond in the area 429–427 cm^-1 is indicative of the formation of the complex. As a result of thermal analysis, 4 coordination complexes with monodentane ligand in a ratio of 1: 2 (M-L) containing crystallizing water were formed.

Figure 4. IR spectrum of the CoL¹L² (CH₃COO)₂ complex

Analysis of the IR spectra of mixed ligand complexes showed that the valence oscillations of the C = N group in the melamine molecule varied sharply from 1651 to 1679, 1677 cm^-1. The valence oscillations of the amino groups in melamine were almost unchanged from 3330 to 3321 cm^-1 in the complexes. The oscillation frequencies of the amino group in glycine ranged abruptly from 3169 to 3249 cm^-1. Characteristic valence oscillations of the COOH group in the glycine molecule were observed in the complexes without abrupt changes from 2807 to 2801 cm^-1.

In conclusion, it can be said that the coordination bond with the metal complexing agent in mixed complexes occurs from the endocyclic nitrogen atom in melamine and the nitrogen atom of the amino group in glycine. Another proof that the formation of a complex occurs precisely through nitrogen atoms is the appearance of new absorption lines in the IR spectrum of the complexes, which are not observed in the spectrum of ligands in the 465, 458 cm^-1 region. In contrast to the spectrum of ligands, new absorption lines were also observed in the spectrum of the complexes in the area of ​​1330–1344 cm^-1.

The fact that these lines belong to the absorption lines of acetate acidoligants, which are mainly bound to the literature [5-7], indicates that these acid residues are located in the inner sphere. Spectral results suggest that cobalt and nickel complexes contain water molecules.

From the analysis of IR spectra of ligands and mixed-base metal complexes based on them, it can be concluded that the polydenant ligands used in complex formation reactions are coordinated in a monodentate state to the central atom by nitrogen atoms. It can be noted that these findings confirmed the results of quantum chemical calculations. It was concluded that the structure of the synthesized complex compounds could be in a tetrahedral form.[11-12]

Based on physicochemical studies of the synthesized complex compounds, it was concluded that the composition of the complexes is 1: 1: 1 (M: L¹: L²), has an individual crystal lattice, cobalt and nickel complexes are mutually isostructural, and the structure of copper and zinc complexes differs from the above. Based on the results of thermal analysis, it was shown that all the complexes are in the crystalline hydrate state, and that the cobalt and nickel complexes contain coordination water molecules [8].

The results of spectroscopic analysis of the synthesized complexes revealed that the monodentate is coordinated by the nitrogen atoms in the ligands used, while the acidoligans are in the inner sphere. Based on the obtained results, an octahedral structure was proposed for cobalt and nickel complexes, and a tetrahedral structure for copper and zinc complexes [9-10].

The following structural formulas are given for complex compounds obtained on the basis of physicochemical analysis:

Me :  Co, Ni

Conclusions. A methodology for the synthesis of complexes of Co (II) acetate mixed with melamine and glycine was developed, and well-soluble complex compounds in fresh water were synthesized. The composition and structure of the complex compounds synthesized using physicochemical studies were studied. It was found that the mixed metal complexes obtained on the basis of melamine and glycine are combined in the ratio (M: L¹: L²) 1:1:1, have a thermally stable and specific crystal lattice relative to the ligands. According to the results of thermal analysis, the new complex of cobalt was found to contain both coordination and crystallization water molecules at the same time.

According to the results of IR spectroscopic analysis, polydenate ligands in the synthesized complexes show monodentality, the shape of the complexes depends on the nature of the metal, the complexes holding Co (II) have an octahedral shape.

References:

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