Introduction

Heterocyclic compounds are importance in organic chemistry because of their biological activities [1]. Pyrazol is doubly unsaturated 5 membered ring compound with 3 C atoms and 2 N atoms. Many pyrazoline substitution productions are useful in medical [2]. 4-Aminoantipyrine (4-AAP) is one of the heterocyclic compounds containing 2 N atoms in its ring, linked with a more reactive amine and carbonyl functional groups. The existence of hetero atoms affects the redistribution of electrons and thus exhibits aromatic character, which is designated as heteroatom effect [3] that imparts the reactivity, chelating effect, etc. Because of this, it is individually useful in research areas such as analytical, modern organic, bioorganic and medicine chemistry [4, 5]. 4-Aminoantipyrine (4-AAP), an anti-pyretic agent, is one of the pyrazole derives [6]. Many preparation compounds containing pyrazole have drawn attention in the field of medicine chemistry because of their pharmacological, photographic, catalytic and liquid crystal application [7, 8]. Its metallic complexes have some applications in analytic and pharmacologic fields [9]. The transition metals complexes of 4-aminoantipyrine (4-AAP) and its derived have been extensive examined related to their many applications in different areas such as biological, analytical and therapeutically [10].

Materials and Methods

Experimental

Melting point for prepared compounds were measured by using digital melting point apparatus Stuart Melting Point. IR spectra of the ligand and its complexes were measured using a Shimadzu (FT-IR)–8400S spectrophotometer at range 400-4000 cm^–1. The U.V spectra of the compounds were using U.V-Vis spectrophotometer kind double beam at range 200-1000 nm, Shimadzu UV160A nm; the standard solutions was 0.001 mol/L in dimethyl sulfoxide solvent and the cell is one cm long, which is made from quartz. The ¹H-NMR and ¹³C-NMR spectra of compounds were recorded on Brucker DRX kind system (500 MHz) in TMS as a standard in Dimethyl sulfoxide-d₆ solution. Mass spectra for ligand was recorded by (EI) mass spectroscopic using MS Model: 5973 Network Mass Selective Detector. TGA analysis of some compounds was carried out using a STA PT-1000 Linseis company /Germany. Molar conductivity measurements for complexes were measured at (27 °C) of 0.001 mol/ L solution for complexes in DMSO using a Jenway Ltd. 4071 digital conductivity meter. The magnetic sensitiveness for some complexes was checked using in Balance Johnson Mattey. The elemental micro analysis of ligand and its complexes were measured in Euro vector model (EA3000). Metals content of compounds were recorded using Shimadzu atomic absorption spectrophotometer 680G. Potentiometry titrations methods were used to determined chloride content of compounds using a 686-titro processor-665 Dosimat-Metrohm Swiss. Agar diffusion was used to test antibacterial activity.

Synthesis of Schiff base ligand (L2)

0.203 g was dissolved of 4-AAP (1 mmol) in 20 mL absolute ethanol and added to a solution of anthrone (0.194 g, 1 mmol) mixed with 60 mL absolute ethanol and 60 mL glacial acetic acid. The mixture was refluxing for 24 h with stirring. Brown precipitate formed which was washed by ethanol and recrystallized with methanol to get a pure product and dried at room temperature [11]. The melting point of Schiff base ligand was prepared at 205-207 °C, molecular weight: 379 g/mol (C₂₅H₂₁N₃O), Yield: 93%, Scheme 1.

Scheme 1: Synthetic route for ligand L2

Preparation of L2 complexes

0.179 g was dissolved of manganese (II) chloride tetra hydrate (1 mmol) in 20 mL of absolute ethanol and added drop wise to a solution of L2 dissolved in 25 mL of absolute ethanol. The mixture was refluxed for 1 h with stirring. Brown precipitate was produced, washed several times with absolute ethanol to get a pure sample and dried [12]. Using a similar method of Mn(II) complex, we synthesized the complexes MCl₂.nH₂O, M(II)=[Co (n=6),Cu (n=2) ions, Ni (n=6) ion ,Zn (n=0), Cd (n=2) and mercury (n=0) ions] (Schemes 2-4).

Results and discussion

The physical properties, C.H.N analysis, metal content and chloride content data are listed in Table 1.

Characterization of ligand L2

FT-IR spectra

The FT-IR spectrum of L2 (Figure S1) shows new peak at 1658 cm^-1 due to imine group (C=N) stretching vibration [13]. The ligand spectrum did not show the appearance of two bands of υ asy: NH₂, υ sy; NH₂ for 4-amino antipyrine and band of C=O of anthrone and appearance of imine group indicate the formation of Schiff base L2 [14].

Electronic spectrum

The Ultraviolet-visible (UV-Vis) spectrum of L2 (Figure S2) exhibited two absorption peaks; the first strong peak at 301 nm and 332 cm^–1 refers to π → π* electronic transition. The other weak band at 400 nm (25000) cm^-1 is attributed to n→π* electronic transitions [15].

¹H-NMR spectrum

¹H-NMR spectrum for L2 is displayed the resonance at chemical shift δ_H = 7.03-7.98 ppm related to protons of aromatic ring Ar-CH. The spectrum displayed chemical shifts at δ_H = 4.48 ppm attributed to protons of CH₂ group of anthrone [11]. The manifestation of these protons as a multi are attributed to mutual coupling. The spectrum showed chemical shifts at δ_H = 2.49-2.51 ppm and 3.15 ppm pointing to Dimethyl sulfoxide and existence of water molecule HOD in solvent, respectively [16]. The spectrum showed chemical shifts at δ_H = 2.39 and 3.19 ppm, which are assignable to protons of C-CH₃ and N-CH₃ groups, respectively (Figure S3) [13].

¹³C-NMR spectrum

The ¹³C-NMR spectrum of L2 in dimethyl sulfoxide-d₆ solvent showed chemical shift at range δ = 124.1-129.8 ppm pointing to aromatic carbons atoms [11]. The chemical shifts at δ = 182.9 ppm were due to C=O carbon atom (C₁₆), while the chemical shifts at δ = 160 ppm were due to C=N carbon atom (C₁₃) [17]. The chemical shifts at δ = 32.5 ppm were due to methylene group (C₁₄). The chemical shifts at δ = 133.4 ppm were due to (C₂₃) [11].  Chemical shifts at δ = 10.7 ppm and 32.5 ppm were assigned to methyl group carbon atoms (C₂₀, ₂₂), respectively (Figure S4) [18].

Mass spectra

The mass spectrum for L2 is shown in Figure S5. The molecular ion peak of ligand appearing at m/z⁺ = 379 [M]⁺ C₂₅H₂₁N₃O requires = 379 [19].

Table 1: Analysis data and Physical properties for ligand and its metals complexes

Scheme 5: The suggested mass fragmentation of (L2)

The other peaks detected at m/z⁺ = 366-52 correspond to [C₂₄H₂₀N₃O]⁺- [C₃O]⁺. The suggested mass fragmentation of L2 is shown in Scheme 5.

Characterization of complexes

FT-IR spectra

The assignment of the characteristic peaks for functional grope of complexes are presented in Table 2 (Figure 1 and 2).  The peak at 1635 cm^-1 is assigned to the stretching frequency for azomethine group C=N of the free ligand. This band was shifted to lower or higher frequency at range 1589-1650 cm^-1 in spectra of all prepared complexes; this shift may be due to involved nitrogen atom of azomethine group in coordination with metal ions [11]. The peak at 1678 cm^-1 stretching vibration refers to C=O for carbonyl grope of free ligand was shifted at range 1649-1674 cm^-1 in spectra of all complexes, displaying coordination between oxygen atom of this group and metal ions [20]. At the lower frequency region, the IR spectra of all synthesized complexes showed new bands, not present in the spectrum of the free ligand; these bands are located at 495-505 cm^-1, 455-464 cm^-1 due to M-N, M-O, respectively [21, 22]. The band at 3365 cm^-1 in spectrum of complex [Ni(L)₂] Cl₂.H₂O is due to H₂O hydrated [23], while the stretching bands at range 3062-3431 cm^-1 and at range 910-920 cm^-1 in spectrum for complexes were due to coordination of H₂O (aqua) [24].

Figure 1: FT-IR spectrum for [Ni(L²)₂]Cl₂.H₂O

Figure 2: FT-IR spectrum for [Cu(L²)₂( H₂O)₂]Cl₂

Table 2: FT-IR data (cm-1) of Schiff base (L2) complexes

Electronic Spectra

The electronic spectra data of synthetic complexes are listed in Table 3 with electronic transition and suggestion geometries (Figure S6 and S7). The electronic spectra of prepared complexes showed two-four absorption bands at range 272-393 nm and 36765-25445   cm^-1 which were attributed to the intra-ligand [25]. New absorption peak at range 392-420 nm and 25510-23810 cm^-1 in spectra for complexes can be assigned to MLCT [23].

Table 3: Electronic spectral data for complexes

Molar conductance

The molar conductivity values of Schiff base ligand complexes in DMSO (10⁻³M solution) at room temperature are listed in Table 4. The molar conductivity values of complexes [Mn(L2)₂ (H₂O)₂] Cl_2, [Co(L2)₂ (H₂O)₂] Cl₂ and [Cu(L2)₂(H₂O)₂] Cl₂ are 1:2 electrolytic natures. The molar conductivity values of complexes [Zn(L2) (H₂O)(Cl)] Cl, [Cd(L2) (H₂O)(Cl)] Cl and  [Hg(L2) (H₂O)(Cl)] Cl are1:1 electrolytic natures.

Magnetic properties

The X_M, X_A, and μ_eff of the complex were calculated using the Xg value obtained and theoretically calculated D. The magnetic moments of complexes are listed in Table 4.

Thermal Analysis

Thermal Analysis of [Mn(L2)₂(H₂O)₂]Cl₂

The thermo gram for [Mn(L2)₂(H₂O)₂]Cl₂ is shown in Figure S8. In TGA, peak recognized at 106.25 ºC is pointing to loss (H₂O) portions, (W.t = 0.1890 mg, 1.95 %). The second step at 317.291 °C that specific to loss (H₂O, Cl₂, 2CH₃, C₆H₅, C₂CON₂) fragment, (W.t = 2.90 mg, 30 %). The third step at 546.708 °C pertains to loss (C₁₄H₁₀N) fragment, (W.t = 2.02 mg, 20.86 %). The fourth step at 899.958 °C is designated to the loss of (CH₄, H₂, C₆H₅, CO) fragment, (W.t = 1.43 mg, 14.78 %). The final remainder of the compound that appeared above 900 ºC is assignable to (MnC₁₇H₁₀N₂), (W.t = 3.14 mg, 32.41 %) [26].

Thermal Analysis of [Zn(L2) (H₂O) (Cl)]Cl

The thermo gram for [Zn(L2) (H₂O)(Cl)]Cl is shown in Figure S9. In TGA, band recognized at 334.125 °C is specific to loss (H₂O, Cl₂, 2CH₃, C₆H₅) portions, (det. =2. 20 mg, 36. 74 %). The second step at 899.958 °C pertains to loss (C₁₄H₆) fragment, (obs. = 1.95 mg, 32.63 %). The final remainder for compound that appeared above 900 °C is specific to (ZnC₄H₆N₂O), (W.t = 1.83, 30.63 %) [27].

Biological activity of Schiff base (L2) and its complexes

The prepared of ligand L2 and its metal complexes of this study were tested against types from bacteria gram negative such as Bacillus (Figure 3) and Escherichia coli (Figure 4) and gram positive such as Pseudomonas auroginosa (Figure 5) and Staphylococcus aurus (Figure 6). The ligand and its complexes showed activity against both gram-positive and gram-negative bacteria; some complexes showed better antibacterial activity than the identical ligand [28], but there are other reports in which the ligand has had higher activity than its complexes [29]. The higher activity for complexes is usually expressed mainly based on the Tweedy’s chelation theory [30]; the measured areas of inhibition against the growth of various microorganisms are shown in Table 5.

Table 4: The molar conductivity of Schiff bases ligand complexes

Figure 3: Biological activity of Schiff bases ligand and their complexes against Bacillus bacteria

Figure 4: Biological activity of Schiff bases ligand and their complexes against Escherichia coli bacteria

Figure 5: Biological activity of Schiff bases ligand and their complexes against Pseudomonas auroginosa bacteria

Figure 6: Biological activity of Schiff bases ligand and their complexes against Staphylococcus aurus bacteria

Table 5: Bacterial activity for ligand (L2) and its complexes

Conclusion

1. The ligand (L2) acted in the form of bi dentate ligand through a nitrogen in imine and oxygen in (C=O) grope with metallic ions M(II): Manganese, Cobalt, Nickel,Cupper, Zink, Cadmium and mercury .
2. The octahedral shape structure is suggested for prepared complexes except complex [Ni(L)₂] Cl₂.H₂O showing the shape square planer and complexes Cd(II), Hg(II) and Zn(II). It showed the shape tetrahedral.
3. The synthesized ligand and its complexes have had biological activity against some types of bacteria such as Bacillus, Escherichia coli, Pseudomonas auroginosa and Staphylococcus aurus.

Acknowledgments

I would like to express my sincere thanks with my appreciation to my supervisor Prof. Dr. Sajid Mahmood Lateef. I would also like to thank the residents for my research for their efforts in correcting it.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions

All authors contributed toward data analysis, drafting and revising the paper and agreed to responsible for all the aspects of this work.

Conflict of Interest

We have no conflicts of interest to disclose.

ORCID

Weaam A. Mahmood

https://www.orcid.org/0000-0002-1026-3475

Supporting Information

The Supporting Information is available of http://www.chemmethod.com/article_150040.html 

HOW TO CITE THIS ARTICLE

Weaam A.M. Al-Shammari, M. Lateef, Synthesis, Structural, Thermal and Biological studies of ligand derived from Anthrone with 4-Aminoantipyrine and its metallic complexes. Chem. Methodol., 2022, 6(7) 548-559

https://doi.org/10.22034/CHEMM.2022.339536.1499

URL: http://www.chemmethod.com/article_150040.html