CC BY
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ISSN 2522-1841 (Online) ISSN 0005-2531 (Print)
UDC 543.3+615.3; 66.096.4
SYNTHESIS AND CHARACTERIZATION OF NEW METAL COMPLEXES WITH TRIDENTATE HYDRAZONE LIGAND
G.G.Abbasova, A.M.Pashajanov, M.I.Ganbarova, S.M.Gasanova, Z.A.Mammadova,
A.M.Nasibova
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan veliyeva_g23@yahoo.com
Received 09.02.2023 Accepted 29.03.2023
Considering necessity of application of Schiff base ligands, containing hydrazone moiety, there were synthesized 2-hydroxy-1-naphtaldehyde acetylhydrazone and its metal complexes. A tridentate ligand with hydrazone moiety was synthesized on the basis of acetylhydrazine and 2-hydroxy-1-naphthoic aldehyde. The characterization and structure of it was identified by IR, UV- and NMR-spectroscopy. The electronic absorption spectrum of the ligand shows absorption bands in the range of Xmax 237-320 nm. 1H NMR (300 MHz, CD4O): 8 6.90-8.21, 9.31, 10.52. Recrystallization occured from an ethanol. Melting point of the ligand was 215+3°C. Yield was 80%. There were acquired complexes of the Schiff base ligand with zinc and manganese. Colored solid complexes of zinc and manganese (II), respectively, yellow and brown colors with the obtained ligand were synthesized in ethanol medium. Yield for complexes was 75 and 73 %, respectively for zinc and manganese complex. The molar ratio of ligand and metal in the complex was 2:1. The structure of the complexes was confirmed by elemental analysis, IR-, UV-, and thermogravimetric analysis.
Keywords: Hydrazones, 2-hydroxy-l-naphthoic aldehyde, acetylhydrazine, Schiff base, complexing. doi.org/10.32737/0005-2531-2023-4-84-90
Introduction
In recent decades, hydrazone moiety containing Schiff base ligands have attracted much attention. Though, compounds containing a hydrazone group have various advantageous properties. This class of compounds is very popular in synthetic organic chemistry due to the ease of the preparation and biological activity [1-3]. Hydrazones contain drug-acting systems, which selective affect on cancer cells [4]. Hence these compounds, especially their copper complexes showing anti-cancer and anti-microbial effect can be applied for medical purposes [5-6]. Copper complexes of hydrazones are the best alternative to cis-platin complexes due to their biocompatibility. In biological systems copper compounds can pass through the membranes of cells and penetrate to cancerous cells by accumulation [7, 8]. Numerous of studies have been devoted to the synthesis, characterization of a novel Schiff base and obtaining its copper complexes. In addition to results were studied anticancer effects of synthesized compounds against human breast cancer [9, 10]. That is why synthesized compound can be applied in breast cancer therapy as an anticancer drug.
In addition to medical properties, Schiff bases have another characteristic property - a luminescent property. It was clarified, that the luminescent properties of these compounds with lanthanides are more attractive than other metals. Since, a remarkable emission properties, very large shift, narrow-band emission, and long lifetimes of these complexes determines their use as a luminescent materials, as probes and labels in biological and chemical applications for sensitive and selective detection [11-13].
From electroluminescent materials as dyes, metal complexe and polymers the most widely used are metal complexes in organic light emitting diodes and the latest flat panel displays. Because the metal complexes are applied dissolved in the solvent and can form a thin layer after the solvent evaporates [14]. Due to necessity Schiff base complexes has been studied even in the reduction form of the azomethine bond by sodium borohydride [15, 16]. It needs to note that their studying on the luminescent properties is still very rare and limited. From this point, a number of practically useful properties provide Schiff bases broad-spread use for research purposes. Due to the
actuality of the application of these compounds there have to be paid more attention to their synthesis methods.
The present work is devoted to the synthesis of target ligand containing hydrazone moiety (LH2) and its complexes with metals.
Experimental part
Materials and Methods
All reactants for the synthesis and solvents were purchased from commercial suppliers and were reagent grade. Hydrazine and acetyl chloride were purchased from Sigma-Aldrich Co. and were used without further purification.
1H and 13C NMR spectra were recorded on a Bruker (300 MHz) spectrometer in CD4O. Electronic absorption spectra were recorded on a UV-VIS spectrophotometer Evolution 60S in ethanol. Infrared spectra (KBr pellets) were recorded on a spectrophotometer Nicolet IS10 in the range 5004000 cm-1. Thermogravimetric analysis was performed using a NETZSCH STA 449F3 deri-vatograph. The elemental analyses were performed in the analytical laboratory Tubitak, Ankara, using the LECOCHNS 932 analyzer.
Synthesis of 2-hydroxy-1-naphthalde-hyde acetylhydrazone (LH2)
For the synthesis of LH2 at the outset there were obtained acetyl hydrazide from ace-tyl chloride and hydrazine. For this aim, there was added 4 ml of triethylamine to 10 ml of anhydrous hydrazine in a 100 ml beaker and was stirred with a magnetic stirrer. To the mixture in the beaker was added 14.4 ml of acetyl chloride 1 drop in every 5 seconds using a dropping funnel. The reaction mixture is cooled under ice conditions to avoid overheating. The resulting white slurry was recrystallized from ethanol to give pure needle acetylhydrazine. M.p. 70±3°C. The preparation of 2-hydroxy-1-naphthoalde-hyde based on naphthol was carried out according to the method [17]. To obtain the target Schiff base 2-hydroxy-1-naphthoic0 aldehyde and acetylhydrazine was taken in a ratio of 1:1. 516.5 mg (3 mmol) of 2-hydroxy-1-naphthoic aldehyde was dissolved in 5 ml of ethanol and 133.2 mg (3 mmol) of a solution of acetylhy-drazine in water was added to it with stirring
and heating to 600C. From the resulting yellowish homogenous solution precipitated bright yellow slight needle crystals within 1 day. Acquired precipitate was filtered, recrystallized from an ethanol and dried over CaCl2 in a desiccator. M.p.: 215±3°C. Yield was 80%. Anal. calcd for Ci3HI2N2O2: C 68.44; H 5.27; N 12.28%. Found: C 68.55, H 5.40, N11.95%. 1H NMR (300 MHz, CD4O): 5 6.90-8.21 (6H at naphthoic ring), 9.31(s, 1H;NH), 10,52 (s,1H; OH).
Preparation of Zinc complex with LH2
For the synthesis of zinc complexe with 2-hydroxy-1 -naphthaldehyde acetylhydrazone, there was taken 183.41 mg (1,0 mmol) Zn(CH3COO)2 and dissolved in 5 ml methanol. Then 456.28 mg (2.0 mmol) 2-hydroxy-1-naphthaldehyde acetylhydrazone was dissolved in 10 ml ethanol. Both solutions were stirred upon mild heating. After heating, the solution of Zn(CH3COO)2 was added to a solution of ligand. After a day, bright yellow zinc complexe precipitated from the resulting yellowish homogeneous solution. The obtained precipitate was filtered, washed with distilled water, and then with alcohol.
NMR spectroscopic studies
Acquired zinc complexe was dried over CaCl2 in a desiccator until a constant weight was reached. M.p. > 2800C. Yield: 75%. Calculated for Zn(C13HuN2O2)2 C 60.09; H 4.23; N 10.78%. Found: C 60.03; H 4.17; N 10.23%.
Preparation of Manganese (II) complex with LH2
A manganese (II) complex with 2-hydroxy-1-naphthaldehyde acetylhydrazone at a ratio of 1:2 (M: L) was prepared as the same as described above. There was taken 244.97 mg (1.0 mmol) Mn(CH3COO)2-4H2O and 456.28mg (2,0 mmol) Schiff base. They were dissolved in 5 ml methanol and in 10 ml etha-nol, respectively. Melting point of acquired brown complex was over 2900C. Yield: 73%. Calculated for Mn(C13HuN2O2)2 C 61.33; H 4.32; N 11.00%. Found: C 61.27; H 4.30; N 10.80%.
O
OH
O
NH
,-NH-K -
CH
CH
OH
1
2
3
Scheme 1. Synthesis of Schiff base ligand. 1. 2-hydroxy-1- naphthoic aldehyde; 2. Acetylhydrazine; 3. LH2.
range of ^max 237-320 nm.
Bands, which appears at 320 nm and corresponds to low energy side, is considered to be
*
n-rc transition of conjugation between the lone pair of electrons of nitrogen atom in azomethine group and a conjugated rc bond of naphthoic ring. The rest two bands, appearing at higher
energies of 239 and 252 nm, are associated with
* *
rc-rc and n-rc transitions of carbonyl moiety, naphthoic ring and amide bonds [10, 14]. Com-plexation of ligand with metal ions results in a bathocromic shift of the 320 nm to 332 and 339 nm, respectively for Mn and Zn complexes. Except these bands in case of complexes there were observed bathochromic shift of the 252 nm to 265 and 285 nm, and gypsochromic shift of the 239 nm to 231 and 232 according to Mn and Zn. These shifts were originated due to the coordination and the formation of a larger conjugated chelate rings in the complexes [20].
220 240 260 280 300 320 340 360 380 400
X, nm
Fig. 1. UV-spectra of LH2 and complexes: 1 - LH2; 2 - Zn complex; 3 - Mn (II) complex. AZERBAIJAN CHEMICAL JOURNAL № 4 2023
Discussion of results
Based on acetylhydrazine and 2-hydroxy-1- naphthoic aldehyde, a new polydentant ligand containing a hydrazone fragment was obtained. The synthesis reaction is presented as the following scheme (Scheme 1).
The nuclear magnetic resonance spectrum of the derived Schiff base ligand consistent with literature data. In the 1H NMR spectrum of the ligand peaks in the range of 6.90-8.21 ppm are accepted as naphtoic ring protons. Except these peaks, there were observed peaks in the 9.31 and 10.52 ppm which are suitable for the hydrogen atoms in the NH and OH groups.
Electronic spectra
Electronic absorption spectra of the lig-and and their metal complexes were carried out in ethanol in the UV region at room temperature (Figure 1). The electronic absorption spectrum of the ligand shows absorption bands in the
IR spectroscopy
The main absorption bands of Schiff base ligand and its complexes with metals are presented in the Figure 2. The bands observed at 3185 and 720 cm-1 are respectively associated to stretching and out of plane bending vibrations of OH, while in the spectrum of copper complex these bands appeared at 3447 and 739 cm-1, respectively [9].
As can be seen from the spectra, a very strong peak is observed in the absorption band of the ligand at 3175 cm-1, which corresponds to the non-coordinated hydroxyl group. The corresponding peak is observed in the spectra of zinc and manganese complexes at frequencies corresponding to the coordinated hydroxyl group, 3362 cm-1 and 3364 cm-1, respectively, for zinc and manganese. It indicates that OH group of naphthoic ring takes part in the coordination with metal. Stretching vibration bands C=N group are observed at 1590-1604cm-1 [18]. Another intensive band due to CN stretching vibration is also present in the spectra of the complexes and ligand (1618, 1620 and 1600 cm-1,
respectively for zinc, manganese complexes and a ligand). This band is observed in shifted form comparatively with the ligand due to involvement of the iminic nitrogen atom in coordination [12]. The bands which are characteristic for the peptide bonds in the 1655-1630 cm-1 [19] due to the coupled vibrations 5(NH)+v(CN) in the spectrum of complexes (1735 and 1740 cm-1, respectively for zinc and manganese) are shifted comparatively to the bands in the spectrum of the ligand (1640 cm-1). This proves that the oxygen atom bonding with the peptide group is involved in coordination. There is a medium absorption band in the range of 2930 cm-1 which may be attributed to stretching vibration v(NH) in the spectrum of the Schiff base. In spite of medium intensity this band is an important band which was observed in the spectra of complexes also. It proves that NH group was not involved in coordination. This band also shows that ligand present in coordination in the keto tautomeric form (Scheme 2).
4000
3200
2400
1800
1400
1000
600
Wave number, cm"
Fig. 2. IR spectra of the ligand and complexes: 1 - Schiff base ligand, 2 - Complex of manganese(II), 3 - Complex of zinc).
3
2
1
M=Zn; Mn
Scheme 2. Tautomeric forms of LH2 and suggested structure for the presented complexes.
Thermogravimetric analysis According to the data of thermogravimet-ric analysis, the thermal decomposition of the obtained complexes was studied in the temperature range 25-9950C with a heating rate of 40.000C/min. There are shown the TG and DTA curves for the zinc (Figure 3).
For the zinc complex thermogravimetric analysis data show that the decomposition of the complex occurs in three stages. The first weight loss 26.88% lies in the temperature range 150-2000C, corresponds to the elimination of the crystalline water. The second stage of decomposition occurs in the temperature range of 200 to 4000C with a weight loss of 46.985%, due to the elimination of carbonyl group and coordination
bond between nitrogen and metal. At the last stage decomposition started at the temperature of 4000C, lasted until 9000C and weight loss (15.227%) is accompanied by complete destruction of the organic ligand. The remaining mass (~11%) corresponded to the zinc oxide in the sample. Metal percentages calculated from ther-mogravimetric curves corresponded to the results of elemental analyses.
The study of numerous published works gives reason to think about the composition and structure of the complexes. Referring to the literature data [10-14] and spectral data it can be proposed formulae for the metal complexes as following Scheme 2.
Fig. 3. Derivatogram of the complex of zinc with LH2
Conclusion
We have synthesized a new Schiff base ligand which contains hydrazone moiety and its complexes with manganese, zinc and copper. The lig-and and complexes were characterized by different physicochemical methods. Metal to ligand stoichi-ometry in the composition of complexes was found as 1:2. Relying on spectral studies has been offered structural formulae of acquired complexes.
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TRiDENTAT HiDRAZON LiQANDI iLO YENi METAL KOMPLEKSLORiNiN SiNTEZi VO
XARAKTERiSTiKASI
G.Q.Abbasova, A.M.Pa$acanov, M.LQanbarova, S.M.Hasanova, Z.A.Mamm3dova, A.M.Nasibova
Tarkibinda hidrazon fraqmenti olan §iff asasli liqandlann istifada zaruratini nazara alaraq 2-hidroksi-1-naftaldehidasetilhidrazon va onun metal komplekslari sintez edilmi§dir. Hidrazon fraqmenti olan tridentat liqand asetilhidrazin va 2-hidroksi-1-naftoaldehid asasinda sintez edilmi§dir. Onun xususiyyatlari va qurulu§u IR, UV va NMR spektroskopiyasi ila muayyan edilmi§dir. Liqandin elektron udma spektri Xmax 237-320nm diapazonunda udma zolaqlarina malikdir. 1H NMR (300 MHz, CD4O): 8 6.90-8.21, 9.31, 10.52. Liqandin tamizlanmasi yenidan kristalla§ma ila etanoldan aparilmi§dir. Liqandin arima temperaturu 215+30C-dir. Qixim 80% olmu§dur. §iff asasli liqandin sink va manqan ila komplekslari alinmi§dir. Sink va manqanin (II), sari va qahvayi rangli bark komplekslari etanolda sintez edilmi§dir. Komplekslara uygun olaraq gixim sink va manqan kompleksi ugun muvafiq olaraq 75 va 73% ta§kil etmi§dir. Kompleksda liqand va metalin molyar nisbati 2:1 nisbatindadir. Komplekslarin strukturu element analizi, iQ, UB- va termogravimetrik analiz naticalari ila tasdiq edilmi§dir.
Agar sozlzr: hidrazonlar, 2-hidroksi-1-naftoaldehid, asetilhidrazin, §iff asasi, komplekcsmslsgslms.
