SYNTHESIS AND STUDY OF MIXED-LIGAND COMPLEX COMPOUNDS BASED ON ALANINE AND 3d-METAL BENZOATES

ABSTRACT

In this study, the synthesis of mixed-ligand complex compounds based on alanine and 3d metal benzoates was made and analyzed by the physicochemical method.

АННОТАЦИЯ

В данном исследовании был сделан синтез смешанно-лигандных комплексных соединений на основе аланина и бензоатов 3d металлов и проведён анализ физико-химическим путём.

Keywords:  сoordination compounds, 3d-metals, ligands, metal benzoates, derivatogram, Chem Office Ultra.

Ключевые слова: комплексные соединения, 3d-металлы, лиганды, бензоаты металлов, дериватограммы  Chem Offise Ultra.

Importance of the research. Today, the synthesis of complex compounds of organic compounds with 3d-metals and the study of their structure and properties is one of the promising areas of inorganic chemistry, in particular, the chemistry of complex compounds. This is due to the great potential of the complexes for use in chemical technology, analytical chemistry, medicine, and various sectors of the national economy. The study of complex compounds is relevant not only in practice, but also in solving such fundamental problems as the nature and structure of chemical bonds in compounds.

The structure of complexes of d-metals with amino acids are convenient objects for studying the effect of complex compounds of  biometals with bioligands on coordination, physicochemical, catalytic, and other properties; therefore, these issues are topical problems of biocoordination chemistry.

The purpose of the study. Development and synthesis of methods for the synthesis of mixed-ligand complex compounds based on metal and amino acid benzoates, study of the structure and composition of the obtained complex compounds.

To achieve these goals, it is necessary to solve such issues as the preparation of bivalent benzoates of Cu, Co, Mn, and Zn, the synthesis of new mixed-ligand complexes with the amino acid alanine based on the obtained metal benzoates, and the study of the composition and structure. new complexes using physical and chemical research methods.[1-3]

The complexes were synthesized in two stages. At the first stage, 0.01 M zinc acetate hydrate was added to 10 ml of a 0.02 M solution of benzoic acid in 10 ml of ethanol until the reaction system was completely dissolved with stirring with a magnetic burner and heated for 15 minutes. The reaction mixture was cooled to room temperature, the precipitated fine crystals were filtered off, the precipitated crystals were washed with ethanol and dried in the open air. Based on this method, Cu, Co, and Mn benzoates were obtained.

Second step: 0.001 mol of Cu, Co, Mn and Zn benzoates were added dropwise to 10 ml of ethanol by mixing 0.002 mol of alanine in 10 ml of ethanol solution. Then cooled to room temperature, filtered and left to crystallize. After 5 days, the precipitate was separated, washed with ethanol, and dried.

Mixed-ligand complexes were obtained according to the following scheme:

Me(CH₃COO)₂ + 2C₆H₅COOH = Me(C₆H₅COO)₂ + 2CH₃COOH

Me(C₆H₅COO)₂ + 2СH₃NH₂CH₂COOH=Me(C₅H₄NCOO)₂(C₃H₇O₂N)₂

According to the results of atomic emission analysis of mixed-ligand complexes, the metal content is as follows: copper 12.501%; cobalt 11.323%; manganese was 9.481%, and zinc was 10.420%, and, accordingly, the empirical formulas were obtained: C₁₈H₂₈O₁₀N₂Cu, C₁₈H₃₀O₁₁N₂Co, C₁₈H₃₀O₁₁N₂Mn and C₁₈H₂₆O₉N₂Zn.[3-4]

Experiments to test the solubility of the obtained compounds in solvents showed that all the resulting complexes are readily soluble in water and alcohols.

Table 1.

Description of the synthesized mixed-ligand complexes

The development of quantum chemical calculations made it possible to plan in advance work in the field of coordination chemistry, and based on the results of quantum chemical calculations, it became possible to predict centers that may encounter competitive coordination in multifunctional ligands.

Quantum chemical analysis of the ligands was carried out using the ChemOffice Ultra mathematical modeling program.

According to the results of quantum chemical calculations, the largest values of the negative effective charge in the alanine molecule occur at the nitrogen atom of the amino group (-0.265 eV), at the carbon atom of the carboxyl group (-0.374 eV) and in the oxygen atom of the OH group (-0.287 eV). Thus, it was theoretically concluded that the amino group of alanine in complex formation reactions could participate in the coordination of the nitrogen atom, the carbonyl oxygen atom of the carboxyl group with the metal atom to form a chelate.

To study the structure of the synthesized compounds, IR spectroscopy was used, which makes it possible to determine the nature of the bond between the donor atom of the ligand and the metal, and the structure of the metal chelate. The results of the analysis of the IR spectra of the synthesized mixed-ligand complexes and starting materials are given in table -1.

When comparing the IR spectra of the ligands, it was found that the absorption peaks of the carboxyl groups of benzoin and alanines differ in the high frequency region by 10–32 cm^–1. - Expansion of the absorption line in the region of 3630-3605 cm-1, corresponding to the stretching vibrations of the OH group, indicates the presence of moisture in complex compounds. In the regions of 3248–3215 cm^–1 and 1625–1605 cm^–1, a slight shift in the absorption line of the stretching vibration of the NH₂ group indicates a redistribution of electrons in the ligand molecule [6-7].

At 2850-2832 cm^-1 - symmetric stretching vibrations of the CH₂ group and at 1478-1465 cm^-1 - asymmetric stretching vibrations; 1684-1676 stretching vibrations of the carbonyl group (Ar-C=O) in the aromatic ring cm^-1; 1607-1601 cm^-1 Symmetrical fluctuations in the valency of the carbonyl group in saturated hydrocarbons (R-C=O); 780-762 cm^-1 and 734-731 cm^-1 - valence-symmetric and valence-asymmetric vibrations of the monoalternated benzene ring of benzoic acid.

In contrast to the IR spectra of benzoic acid and alanines, the spectra of the studied complexes exhibit new absorption lines in the region of 578-562 cm^-1. These are the absorption lines corresponding to the stretching vibrations of the O-Me bond and the stretching vibrations 522-526 cm^-1 - N-Me.[9-10]

According to the results of IR spectroscopy, it can be concluded that the coordination center in the ligand molecules is the oxygen atom of benzoic acid - the C-O bond and the nitrogen atom of alanine. According to the theoretically calculated results of elemental analysis, benzoic acid and alanine molecules are formed in the complexation reactions of copper with Co(II), Mn(II), Cu(II), and Zn(II). Mixed ligand complexes can have an octahedral structure.

Thermal Analysis Paulik G., Paulik J., Erdey Z. In a system with a linear increase in temperature, the mass of the sample, the rate of mass loss and thermal properties are simultaneously investigated. Thus, this analysis makes it possible to determine the number of coordinated water molecules in the complex [3-8], including the temperature line (T), differential thermal curve (DTA), and thermogravimetric curves (TG). The nature of thermal effects obtained as a result of thermal analysis, temperature ranges and mass reduction are shown in Figure 1.   On the DTA curve [CuL¹L²], we see five endothermic effects and three exothermic effects. The first endothermic effect is associated with the loss of hydrate molecules. It loses 16% of its mass, which is equal to the mass of two water molecules. The nature of subsequent thermal effects indicates the decomposition of the complex. The mass loss along the Tg curve at 20–860 ^оС is 60.42%. The nature of the latter effects indicates the decomposition of thermolysis products. Thermal analysis leads to the formation of CuO as the final product.

a)                                                               b)

Picture1. Derivatograms of [CuL¹L²] • 3H₂O (a) and [CoL¹L²] • 3H₂O (b) complexes

The DTA curve of [ZnL¹L²] showed one endothermic effect at 900°C and six exothermic effects at 183, 200, 295, 330, 590, and 820°C, respectively. The first endothermic effect is associated with the loss of hydrated water molecules. It loses 6.91% of its mass, which is equal to the weight of one molecule of water. The nature of subsequent thermal effects indicates the decomposition of the complex. The weight loss according to the TG curve at 20–860°C is 73.50%. As a result of thermal analysis, the final product is ZnO.

[CoL¹L²]. The thermal decomposition of the Co(II) complex at room temperature up to 800-900 0C was studied by thermal analysis. On the DTA curve of the Co(II) [CoL21L22] complex, four endothermic effects were observed at 117, 263, 321, and 498 ⁰C and two exothermic effects at 238 and 283 ⁰C, respectively. The first two effects are associated with a mass loss of 10.2% (crystallized and hydrated water molecules). The exo-effects at 216 and 323°C led to an 83.2% loss in the mass of the nucleus. The nature of the last two effects indicates that CoO is formed as a result of the decomposition and combustion of the thermolysis products. The total mass analyzed was 83 mg.[3-11]

According to the results of thermal analysis, complex compounds decompose in the temperature range of 60-860 ⁰C, unlike ligands. It should be noted that all synthesized complex compounds contain water of crystallization and are crystalline hydrates. If we summarize the results of thermal analysis, then the decomposition of all complex compounds occurs in one stage with the formation of oxides as a result of the combustion of organic matter and the oxidation of decomposition products. Thus, the results of thermal analysis expanded our understanding of the complexes and made it possible to present the following structural formula.[12-13]

Summary. Mixed complexing complexes were obtained by a two-stage synthesis method. First, metal benzoates were formed, and then complexes of ligands mixed with alanine. First, metal benzoates were obtained, and then mixed alanine complexes were synthesized so that the formation of a chelate-type complex through two donor centers in the alanine amino acid used as a ligand did not interfere with the formation of a mixed-ligand complex. Four new mixed complexes were obtained by this method.

The alanine ligand used in the synthesis of complexes can exhibit polydenate in complexation reactions due to the presence of 3 donor atoms. The PM-3 method, a semi-empirical quantum chemical calculation method, was used to determine the competitive coordination of donor centers within a ligand.

The results of the calculations revealed the presence of high values of the negative effective charge of the oxygen atoms of nitrogen and the carbonyl groups of the amino group in the alanine molecule.

On the basis of physicochemical studies of the synthesized complex compounds, it was concluded that the composition of the resulting complexes is 1:2:2 M:L¹:L², has an individual crystal lattice, and the resulting complexes are mutually isostructural.

Based on the results of thermal analysis, it was shown that all complexes are in the crystalline hydrate state.

The results of spectroscopic analysis of the synthesized complexes showed that the bidentate is coordinated by nitrogen and oxygen atoms in the ligand used.

Based on the results obtained, the octahedral structure of all synthesized complexes was proposed.

For complex compounds obtained on the basis of physicochemical analysis, the following structural formula is proposed:

Here M-Mn(II), Co(II), Cu(II), Zn(II); n = 1, 2, 3

References:

1. Melamine bridged polymeric complex of copper(II)// ZHurn. struktur. him. 2011. -T.52. -№6. -P.1152-1156. [in English]
2. Bairi Partha, Roy Bappaditya, Nandi Arun. Gidrogeli koordinacionnogo polimera serebro (I)-melamin// J.Mater. Chem.-2011.-21,№32, c 11747-11749. [in English]
3. Erali Buvrayev, Shahnoza Kadirova, Sanjar Tillayev, Gulnoza Abilkasimova, Nilufar Tursunova.  Synthesis and investigation of mixed bioligand complexes with melamin and glycine. // Universum. Химия и Биология №10(88) октиябрь 2021 г. [in Russian]
4. Semenova M.G., Kornev V.I. Complexonates of cobalt (II) and nekel (II) in aqueous solutions of oxalic acid. // Chemical physics and mesoscopy.-2010.-T. 12, -№. 1.-C. 131-138. [in English]
5. Franceva YU.V. Raschet himicheskih ravnovesij v sisteme geparin-ion Co²⁺ - glicin // ZHurnal fizicheskoj himii. 2013. T. 87. № 8. S. 1432-1434. [in English]
6. Primova M.A., Kadirova Sh.A. , Ziyayev A.A. ,Buvrayev E.R. Co (II) va V (V) ning 5-(fenil)-1,3,4-oksadiazol-2tion asosidagi aralash metalli kompleks birikmasini antioksidantlik faolligini o’rganish. // Samarqand davlat universiteti ilmiy axborotnomasi - 2020 yil 1-son. [in Uzbek].
7. Nakamoto K. IR spectra of inorganic and coordination compounds. - M .: Mir, 1996. - 204 p. [ in Russian]
8. Buvrayev E.R.  , Kadirova  Sh.A ., Normuradov Z.N., Samarova Sh.M..    Synthesis and Study of Mixed Ligand Complexes of Nickel (II) with Cysteine   and Thiamine //Journal of Advanced Research in Dynamical & Control Systems, 2020. -Vol. 12, 05-Special Issue. [in English]
9. Amerhanova Sh.K.  , Golovanova O.A., Uali A.S.  , Shlyapov R.M.  . Adsorbciya nekotoryh aminokislotnyh kompleksov ionov Cu²⁺, Zn²⁺, Fe²⁺, Co²⁺, Ni²⁺ iz rastvorov na digidrofosfate kal'ciya // Vestnik Omskogo universiteta. - 2015. № 4.- S. 50–53.[ in Russian]
10. Buvraev E., Tillaev S., Samarova SH.M., Tilyabov M.U. Mis (II) acetatning melamin va glicin bilan aralash ligandli   kompleksi: sintez, tarkibi va tuzilishi // Innovacionnoe razvitie nauki i obrazovaniya. Mezhdunarodnaya nauchno-prakticheskaya konferenciya. Sbornik nauchnyh publikacij. - Kazahstan. Pavlodar. 2020. Iyun' .  48-53 s. [in Uzbek].
11. Buldakova N.S. Proteoliticheskie i koordinacionnye ravnovesiya obrazovaniya poliyadernyh geteroligandnyh kompleksonatov nikelya (II) v vodnyh rastvorah organicheskih aminov // avtoref.diss… kand.him.nauk. - Izhevsk. 2015. [ in Russian]
12. S.B. Zeynalov, S.K. Sharifova. Synthesis and study of complex compounds based on ferric chloride (FeCI3) reactions with amino acids // Chemical Problems 2020 no. 2 (18) [in Uzbek].
13. Eddie L. Chang, Christa Simmers, D. Andrew Knight. Cobalt Complexes as Antiviral and Antibacterial Agents // Pharmaceuticals 2010, 3, 1711-1728; doi:10.3390/ph3061711 [in English]