Synthesis, Characterization and Biological Study of New Schiff Bases

The condensation of primary amines and carbonyl compounds results in the formation of a Schiff base. A Schiff base is characterized by the general formula R¹R²C═N-R and is also referred to as an imine. Recently there has been great interest in the synthesis of Schiff base derivatives due to their application in different fields, such as their importance in pharmaceutical and biological fields^1,2, the synthesis of some Schiff's base improves drug discovery efforts for Alzheimer’s potentially improving patient outcomes, showed anticancer activity and their use as intermediates in the synthesis of different aromatic compounds.³ The presence of an azomethine bond (N═CH) and the lone pair of the nitrogen atom, along with heterocyclic in one molecule,  it often boosts how well the compound works biologically.⁴. Our aim of this study is to synthesize the new compounds including heterocyclic moiety. Heterocyclic compounds have several applications, including agrochemical and pharmaceutical.

 

The significance of heterocyclic compounds has been recognized in the synthesis of copolymers. These compounds are present in various applications, including sanitizers, antioxidants, dyestuffs, and corrosion inhibitors.⁵ Schiff bases that incorporate heterocyclic moieties have demonstrated physiological and pharmacological activities, highlighting their potential in the development of new drug derivatives. Additionally, many natural compounds, antibiotics, and pharmaceuticals contain heterocyclic rings within their structures.⁶

For example some marketed drugs including heterocycles and azomethin bonds in their structures, are Dantrolene®, Nitrofurantoin^® and Nifurtimax,There are other  example of Schiff bases  that showed antibacterial activity ,antioxidant activity and  acted as potent  urease inhibitor.⁷

   This study was conducted at college of pharmacy / Hawler medical university between 1 of October 2024 to   30 of June 2025, by using different substituted aromatic aldehydes, and heterocyclic aldehydes and two types of amine 2(4-aminophenyl)-6-methylbenzothiazole and 3-aminoacetophenone. Electrothermal melting point apparatuses from Stuart Scientific was used for determination of melting points (Table 1). The infrared spectra   were recorded using A spectroscopy –specific Jasco FT-IR 4600 Spectrometer at the college of pharmacy/ Hawler medical university. ¹H-NMR and ¹³C-NMR spectra were measured using a Bruker 400 MHz with internal TMS as reference (Day petronic Company, Iran) and NMR: Bruker analytic, 400MHz, Photon Center for Nano Development and Research.

 

Synthesis of 3-Nitrobenzyloxy benzaldehyde⁸

6.106 g (0.05 mol) of 4-hydroxybenzaldehyde dissolved in 5ml ethanol and 15.203 g (0.11 mol) of K₂CO₃ were dissolved in 5 ml of absolute ethanol mixed , stirred at room temperature for 2 hours. Afterward, 8.579 g (0.05 mol) of 3-nitrobenzyl chloride was added to the mixture, which was then heated under reflux for 7 hours. Following the heating, the mixture was cooled, treated with ice, and recrystallized using a suitable solvent.

 

A general  method for synthesis of Schiff bases compounds (3a-d) ⁹

The synthesis  involved  dissolving and mixing of substituted aromatic aldehydes (0.01 mol)  in 10ml of  absolute ethanol with (1.3516 g 0.01 mol) of  3-aminoacetophenone  in absolute  ethanol (10 mL) and adding 2 to 3 drops of glacial acetic acid to acidify it as catalyst. The mixture was heated under reflux conditions for 6 to 8 hours. The reaction process was monitored using thin layer chromatography (TLC). After cooling, recrystallization was performed with an appropriate solvent. The physical properties of the resulting compound are summarized in Table 1.

 

Synthesis of (E)-3-(((3-acetylphenyl) amino) methylene)-2-ethoxychroman-4-one (3e)¹⁰ Ethanolic solution of 4-H-1-Benzopyran -3-carbaldehyde (1.74.15g,0.01mol) and (1.3516 g ,0.01 mol) of 3-aminoacetophenone were mixed together and stirred for 3hr at 30-35 ºC, after that  cooled    to room temperature. The yellow precipitate was filtered off and recrystallized from ethanol. The physical properties are described in Table 1

Synthesis of Schiff bases of compounds (6a-e)⁸

0.01 mol of 3-nitrobenzyloxybenzaldehyde was dissolved in 10 mL of absolute ethanol and then mixed with a solution containing 0.01 mol of amine compounds. The resulting mixture was heated under reflux conditions for 6 to 7 hours and subsequently cooled to room temperature. After cooling, the mixture was filtered and recrystallized using absolute ethanol. The physical properties are detailed in Table 2.

Antibacterial study

The antibacterial activity of the Schiff bases was studied using the well diffusion method.^11-12

against two types of bacteria, gram-positive S. aureus and gram-negative bacteria E. coli. We performed the well diffusion test by making nutrient agar plates and adding a specific amount of bacteria to them. Muller-Hinton agar and nutrient agar were used for the preparation of medium for maintenance of pure culture. Using a clean loop, we spread a standardized bacterial culture on the nutrient agar plates, and we tested three different concentrations 250 μg/ml,500 μg/ml ,1000 μg/mlof each compound mixed in DMSO. A sterile cork borer (8 mm) was used to prepare cups constructed on petri plates,  each  well filled with 0.1 ml of each tested compound .We then incubated the bacterial plates at 37°C for 24 hours. The assessment of antibacterial activity was done by measuring the diameter of clear zones of inhibition in millimeters.

Two series of Schiff bases were prepared, specifically compounds 3a-f and 6a-e. The initial step of this research involved synthesizing Schiff bases derived from 3-aminoacetophenone (1). All synthesized compounds were obtained as powder, crystallized from an appropriate solvent, and yielded satisfactory results. The subsequent step focused on synthesizing Schiff base compounds derived from 3-Nitrobenzyloxy benzaldehyde (4). The comprehensive preparation of compounds 3a-f and 6a-e demonstrates effective methodologies and underscores the robustness of the employed processes, as indicated by their satisfactory crystallization yields. This study not only contributes to the current collection of Schiff bases but also opens avenues for further exploration of their potential applications across various scientific fields. The insights gained from this research establish a solid foundation for future investigations into the properties and functionalities of these versatile compounds. Additionally, 3-nitrobenzyloxy benzaldehyde was synthesized using the Williamson ether synthesis method, which involved the reaction of 4-hydroxy benzaldehyde with 3-nitrobenzyl chloride in the presence of K₂CO₃. This compound served as the substituted benzaldehyde in the preparation of Schiff bases for compounds 6a-e. The melting points, percentage yields, and other physical properties are presented in Tables 1 and 2.

Table 1: Some physical constants of the synthesized   compounds (3a-f)

Table 2: Some physical constants of the synthesized  compounds (6a-e)

Compound No.	Ar-	Chemical formula	MP ºC	Yield%	Color
4	3-NO2-C6H4-C6H4CHO	C14H11NO4	53-56	80	Yellow
6a		C22H18N2O3	106-108	40	White
6b		C27H21N3SO3	264-265	65	Green
6c		C23H17N4SO56	195-200	82	Yellow
6d		C17H14N3O4	163-164	75	White
6e		C28H20N2O3	148-150	60	Dark pinkish

    The formation of Schiff bases was confirmed by the disappearance of the characteristic carbonyl group band of the aldehyde compounds at 1689-1693 cm⁻¹, along with the two peaks of the amino group (NH₂) observed at 3460, 3285cm⁻¹. These peaks correspond to the symmetric absorption bands of both amine compounds, confirming the reaction of amines in compounds 1 and 4 with the aldehyde compounds. New peaks associated with the azomethine (CH═N) group characteristic vibration appeared in the region between 1573 and 1627 cm⁻¹ for compounds 3a to g, while the IR spectra of compounds 6a to g showed this peak at 1581-1631 cm⁻¹, indicating the successful formation of the desired compounds. The vibration frequency of the carbonyl group (C═O) in compounds 3a-g was noted at 1658-1673 cm⁻¹. Absorption in the range of 2850 to 2981 cm⁻¹ corresponded to C-H aliphatic, whereas C-H aromatic absorption was observed at 3050-3179 cm⁻¹.

 

Table (3): The FTIR spectral data presents the characteristic frequencies of the synthesized compounds, measured in cm⁻¹.(3a-f)

 

Compound  No.	ʋNH	ʋC-H aromatic	ʋC-H aliphatic	ʋC═O	ʋC═N	ʋNO2 as. str.	ʋNO2 s. str.
1	3463 3263	3050	2977	1662
3a		3070	2977	1673	1627
3b		3050	2935	1658	1592
3c
3d		3070	2981	1666	1573
3e		3081	2973 2904	1681 1643	1581
3f				1673	1592

 

Table (4): Assignment of characteristics frequencies ʋ (cm^-1) of IR spectral data of the synthesized compounds(6a-e)

Table 5: The ¹H-NMR spectral data for some of the synthesized compounds(3a-e), and (6a-e)

S=singlet, d=doublet, t= triplet, m = multiplet

 

Table (6): The¹³C-NMR Spectral data of some of the synthesized compounds

Antibacterial study

The antibacterial activity of  the Schiff bases  was studied using the well diffusion method.^11-13

Choosing two kinds of bacteria, gram-positive S. aureus and gram-negative bacteria E. coli. We performed the well diffusion test by making nutrient agar plates and adding a specific amount of bacteria to them of each compound mixed in DMSO. The assessment of antibacterial activity was conducted by measuring the diameter of clear zones of inhibition in millimeters. he negative control used was DMSO, while the positive control was ciprofloxacin. The synthesized compounds were evaluated in comparison to ciprofloxacin and amikacin. Ciprofloxacin demonstrated greater activity compared to the synthesized compounds. Additionally, the synthesized compounds exhibited higher reactivity against E. coli than against S. aureus. However, compound 6e showed no reactivity. The antibacterial result of amikacin was closest to that of the synthesized compounds.

Table (7):   The diameter of inhibition zones in millimeters of the synthesized compounds (3a-g and 6c-g)) for assaying the antibacterial activity.

Zone of inhibition after 24 hrs, zone size 10-14 mm = +  15-19 mm = ++ , 20-25 = +++

Two series of Schiff bases were prepared, specifically compounds 3a-f and 6a-e. The initial step of this research involved synthesizing Schiff bases derived from 3-aminoacetophenone (1). All synthesized compounds were obtained as powder, crystallized from an appropriate solvent, and yielded satisfactory results. The subsequent step focused on synthesizing Schiff base compounds derived from 3-Nitrobenzyloxy benzaldehyde (4). The comprehensive preparation of compounds 3a-f and 6a-e demonstrates effective methodologies and underscores the robustness of the employed processes, as indicated by their satisfactory crystallization yields. This study not only contributes to the current collection of Schiff bases but also opens avenues for further exploration of their potential applications across various scientific fields. The insights gained from this research establish a solid foundation for future investigations into the properties and functionalities of these versatile compounds. Additionally, 3-nitrobenzyloxy benzaldehyde was synthesized using the Williamson ether synthesis method, which involved the reaction of 4-hydroxy benzaldehyde with 3-nitrobenzyl chloride in the presence of K₂CO₃. This compound served as the substituted benzaldehyde in the preparation of Schiff bases for compounds 6a-e. The melting points, percentage yields, and other physical properties are presented in Tables 1 and 2.

Table 1: Some physical constants of the synthesized   compounds (3a-f)

Table 2: Some physical constants of the synthesized  compounds (6a-e)

Compound No.	Ar-	Chemical formula	MP ºC	Yield%	Color
4	3-NO2-C6H4-C6H4CHO	C14H11NO4	53-56	80	Yellow
6a		C22H18N2O3	106-108	40	White
6b		C27H21N3SO3	264-265	65	Green
6c		C23H17N4SO56	195-200	82	Yellow
6d		C17H14N3O4	163-164	75	White
6e		C28H20N2O3	148-150	60	Dark pinkish

    The formation of Schiff bases was confirmed by the disappearance of the characteristic carbonyl group band of the aldehyde compounds at 1689-1693 cm⁻¹, along with the two peaks of the amino group (NH₂) observed at 3460, 3285cm⁻¹. These peaks correspond to the symmetric absorption bands of both amine compounds, confirming the reaction of amines in compounds 1 and 4 with the aldehyde compounds. New peaks associated with the azomethine (CH═N) group characteristic vibration appeared in the region between 1573 and 1627 cm⁻¹ for compounds 3a to g, while the IR spectra of compounds 6a to g showed this peak at 1581-1631 cm⁻¹, indicating the successful formation of the desired compounds. The vibration frequency of the carbonyl group (C═O) in compounds 3a-g was noted at 1658-1673 cm⁻¹. Absorption in the range of 2850 to 2981 cm⁻¹ corresponded to C-H aliphatic, whereas C-H aromatic absorption was observed at 3050-3179 cm⁻¹.

 

Table (3): The FTIR spectral data presents the characteristic frequencies of the synthesized compounds, measured in cm⁻¹.(3a-f)

 

Compound  No.	ʋNH	ʋC-H aromatic	ʋC-H aliphatic	ʋC═O	ʋC═N	ʋNO2 as. str.	ʋNO2 s. str.
1	3463 3263	3050	2977	1662
3a		3070	2977	1673	1627
3b		3050	2935	1658	1592
3c
3d		3070	2981	1666	1573
3e		3081	2973 2904	1681 1643	1581
3f				1673	1592

 

Table (4): Assignment of characteristics frequencies ʋ (cm^-1) of IR spectral data of the synthesized compounds(6a-e)

Table 5: The ¹H-NMR spectral data for some of the synthesized compounds(3a-e), and (6a-e)

S=singlet, d=doublet, t= triplet, m = multiplet

 

Table (6): The¹³C-NMR Spectral data of some of the synthesized compounds

Antibacterial study

The antibacterial activity of  the Schiff bases  was studied using the well diffusion method.^11-13

Choosing two kinds of bacteria, gram-positive S. aureus and gram-negative bacteria E. coli. We performed the well diffusion test by making nutrient agar plates and adding a specific amount of bacteria to them of each compound mixed in DMSO. The assessment of antibacterial activity was conducted by measuring the diameter of clear zones of inhibition in millimeters. he negative control used was DMSO, while the positive control was ciprofloxacin. The synthesized compounds were evaluated in comparison to ciprofloxacin and amikacin. Ciprofloxacin demonstrated greater activity compared to the synthesized compounds. Additionally, the synthesized compounds exhibited higher reactivity against E. coli than against S. aureus. However, compound 6e showed no reactivity. The antibacterial result of amikacin was closest to that of the synthesized compounds.

Table (7):   The diameter of inhibition zones in millimeters of the synthesized compounds (3a-g and 6c-g)) for assaying the antibacterial activity.

Zone of inhibition after 24 hrs, zone size 10-14 mm = +  15-19 mm = ++ , 20-25 = +++

        The first step of this work was the synthesis of Schiff bases derived from 3-aminoacetophenone (1) The traditional method of condensation reaction, which involves reflux conditions and the use of glacial acetic acid as a catalyst, was applied to various substituted aromatic aldehydes, however, the heterocyclic aldehydes   reacted at lower temperature. The Schiff base was synthesized successfully and characterized based on its physical properties using instrumental techniques such as IR, ¹H-NMR, and ¹³C-NMR, as illustrated in Scheme 1

Scheme 1: Synthesis of 1-(substituted benzylidene)3-amminoacetophenones derivatives(3a-F)

Spectroscopic analysis of compound 3a Figure (4) presents the IR spectrum of compound 3a, emphasizing an absorption band at 1623 cm⁻¹ corresponding to the imine CH═N bond. Notably, there is a disappearance of the symmetric stretching vibration of the amine (N-H) at 3463 and 3263 cm⁻¹, as well as C-H stretching in the aromatic region at 3070 cm⁻¹. Furthermore, the carbonyl (C═O) absorption in the Schiff base is observed at a higher frequency of 1677 cm⁻¹. Table (3). The ¹H-NMR spectrum in DMSO  of  all  of the compounds showed signals related to the solvent at δ 2.5 ppm and δ 3.3 ppm for the water of the solvent,  the compound  3a Figure (7) reveals a singlet signal for the CH₃ group of acetophenone at δ 2.64 ppm, and a multiplet of 8 protons in the aromatic region from δ 7.66 to 8.7, attributed to the presence of two phenyl rings. The singlet at δ 8.913 ppm, which corresponds to the CH═N bond, confirms the formation of the desired product.

The ¹³C-NMR spectrum   analysis of compound 3a (Figure 3) displayed a signal at δ 27.42 ppm corresponding to CH₃ group, along with 12 signal for the two phenyl groups in the aromatic region at δ 121.12-151.36 ppm; additionally, the carbons of the azomethine group (C═N) and carbonyl (C═O) appeared at δ 160.66 and 198.24 ppm, respectively. Figure 7, Table 5 and 6

 

Figure (3): structure of compound (3a)

     The IR spectrum analysis of compound (3e) showed two new absorption bands for the carbonyl group stretching at 1681 cm⁻¹ and 1643 cm⁻¹. These bands correspond to the carbonyl group of acetophenone and the C═O group of the pyran ring. Following the formation of the Schiff base, the absence of the C═C bond absorption band associated with the pyran moiety facilitated a 1,4-conjugate addition (Michael addition) to the chromone system. This was followed by a rearrangement that resulted in the formation of compound through electron transfer to the  imine bond C═CH-NH (3e).The spectra illustrated in Figure 8 and 9.

The analysis of the ¹H-NMR and ¹³C-NMRin DMSOd₆ spectra indicated the formation of the expected product. The solvent molecule participated in the reaction pathway, and the process was carried out in ethanol at 30-35°C without the use of a catalyst. The ¹H -NMR spectrum in DMSOd₆ exhibited signals as a triplet and quartet at δ 1 ppm and δ 3.7 ppm, corresponding to CH₃ and CH₂ groups for the added ethoxy group. The appearance of the doublet at δ 11.9 ppm, attributed to NH, suggested that a 1,4-addition occurred at position 2 of the pyran ring base, with electron transfer occurring between the carbon atom of the pyran ring and the carbon atom of the azomethine (C═N) bond ¹⁴. With good resolution, it is sometimes possible to observe splitting of the humps of N-H by the protons on adjacent carbon atoms.¹⁵ Additionally, the ¹H-NMR spectrum displayed a multiplet signal with 9H at δ 7-8.26, which refers to the phenyl group, the benzene ring, and the C═CH group. The proton attached to this carbon was observed as a singlet at δ 6 ppm.

 

The structure of the expected product, as confirmed by the ¹³C-NMR spectrum (Figures 4 and 10), displayed 14 lines in the aromatic region ranging from 100 to 156.11 ppm. The characteristic signals were found at δ 15.68, 27.40, 63.51 and100.52. ppm, which correspond to the CH₃, CH₃, CH₂, C-H, groups, respectively. Additional lines observed in the spectrum were attributed to the two carbonyl (C═O) groups of the acetophenone keto group and pyran, appearing at δ 198 ppm and δ 180.76 ppm. The signals belonging to aromatic region as δ 104 to156 indicated the presence of 13 C while the The ═CH observed at δ 140ppm.¹⁴ Table (5 and 6)

Figure (4): Structure of compound 3e

The second step of this work included the synthesis of Schiff bases derived from compound (4) through the condensation of some heterocyclic amines without addition of catalyst using reflux condition for 6 hours’ scheme (2)

Scheme (2): The synthetic pathway of Schiff bases compounds ( 6a-e)

The structure of the products was confirmed using spectroscopic data (IR, ¹H-NMR, and ¹³C-NMR). For instance, in the case of compounds 6a,6b,6d the disappearance of the NH₂ group and the appearance of peaks associated with the CH═N at 1600,1608,1604 cm⁻¹along with two absorption bands in the region of 1515-1527 cm^-1 and 1342-1349 cm⁻¹ for the asymmetric and symmetric stretching vibrations of the nitro group; additionally, a strong C─O─C absorption bands were noted at 1249-1257 cm⁻¹ , and the disappearance of carbonyl group in the IR spectrum of Compound 4 at 1681.62cm-1 Figure (5,12,14).The ¹H-NMR spectrum  of compound (6a) in  DMSOd₆ Figure (13) indicated the formation of the product through the appearance of the three singlet signals at chemical shifts 2.64 ppm, 5.37 ppm, and 8.62 ppm, attributed to the CH₃, CH₂─O, and CH═N groups, respectively. ⁸

         The ¹³C NMR analysis corroborated the findings from the IR and ¹H NMR spectral data, indicating the presence of 20 distinct lines. These lines correspond to the CH₃ at δ 27.37, the O-CH₂ at δ 68.58ppm, the C═NH at 161.22ppm, and the carbonyl group at 198.29ppm. The remaining lines are associated with three aromatic rings (Ar), spanning from 115.63 to 166.43 for a total of 16 carbon atoms, as illustrated in Figure. (13). The ¹H-NMR spectrum of compound(6d)) showed the same signals at δ2.43ppm, 5.39ppm, ,6.49ppm and 8.36ppm related to appearance of CH_3,CH₂─O,CH,CH═N   with displaying of 8H for two phenyl groups,  Figure (15).¹³C-NMR spectrum showed 16 lines   for 16 carbon atoms corresponds to the carbons of the expected product , confirmed through the signals belongs to CH2-O carbons in all the synthesized compounds16 as   illustrated in   Figure (16) Table (5)

Figure (5); Structure of compound (6a)

 

 

Antibacterial activity

   The antibacterial activity was assessed against two type of bacterial strains: Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. This evaluation utilized the well diffusion method^11-13 at  different concentrations, 1000 μg/ml, 500 μg/ml, and 250 μg/ml. The activity was qualitatively determined based on the presence and size of inhibition zones. Amikacin and ciprofloxacin served as positive controls.

The results indicated that the most effective compounds against Staphylococcus aureus were 3a, 3c, 3d, and 6c at the highest concentration of 1000 μg/ml. Compound 3d showed consistent activity (+++) at 1000 μg/ml, suggesting a strong antibacterial effect against E. coli. This effect is attributed to the substituted NO₂ group in the para position, which enhances binding affinity to the bacterial target, along with the hydrophilicity and lipophilicity of the overall compound influencing the bacterial cell wall (peptidoglycan).¹⁷Among the tested compounds, 3a, 3b, and 3c demonstrated moderate activity against E. coli at  the concentrations of 250 μg/ml, , and 500 μg/ml and 1000 μg/ml, respectively. In contrast, compounds 3a and 3b exhibited weak activity against both bacterial strains. Compounds 6e were found to be inactive against both strains. Compound 6c showed moderate activity against S. aureus at the 1000 μg/ml whereas displayed excellent activity at a concentration of 1000 μg/ml against E .coli.

 

The antibacterial tests suggested that specific structural features of the compound 3 derivatives were more effective against Gram-positive bacteria compared to the series 6 compounds, likely due to better interaction with the thicker peptidoglycan layer of S. aureus.

 

The slightly improved efficacy of some compounds against E. coli indicates that certain modifications may enhance membrane penetration or interaction with Gram-negative bacterial targets. This may reflect an optimal balance between hydrophilic and hydrophobic regions that supports the antibacterial effect. Meanwhile, the standard drugs ciprofloxacin and amikacin produced significantly larger zones of inhibition.

 

Figure( 6):IR spectrum of compound (3a )

Figure (7 ): ¹H-NMR and ¹³C-NMR spectra of  compound (3a)

 

 

 

Figure (8): IR spectrum of 4-Oxo-4-H-1-Benzopyrane-3-carboaxldehyde

Figure (9):  The IR spectrum of compound (3e)

Figure (10):   The ¹H-NMR  spectrum ¹³C-NMR spectra of compound 3e

Figure(11): IR Spectrum of compound 6a               Figure(12) IR  spectrum of compound (4)

Figure (13): The ¹H-NMR   and ¹³ C-NMR spectra of Compound (6a)

Figure (14): IR spectrum of compound (6d)

          

Figure (15): ¹H-NMR spectrum of compound(6d)  Figure (16): ¹³C-NMR spectrum of (6d)

Two series of Schiff bases were prepared, specifically compounds 3a-e and 4a-e. The first step of this research study involved synthesizing Schiff bases derived from 3-aminoacetophenone. All synthesized compounds were obtained as powders, crystallized from suitable solvents, and yielded satisfactory results. The second step focused on synthesizing Schiff base compounds derived from3-NO2-Benzyloxybenzaldehyde. The successful synthesis of these Schiff bases, including both the 3-aminoacetophenone (1) derivatives and those derived from 3-nitrobenzyloxy benzaldehyde (4). The comprehensive preparation of compounds 3a-f and 6a-e demonstrates effective methodologies and underscores the robustness of the employed processes, as indicated by their satisfactory crystallization yields. This study not only contributes to the current collection of Schiff bases but also opens avenues for further exploration of their potential applications across various scientific fields. The insights gained from this research establish a solid foundation for future investigations into the properties and functionalities of these versatile compounds.

 

Among all tested compounds, 3d demonstrated the most promising antibacterial activity, particularly against E. coli, followed by 3c and 6c. The inactivity of compound 6e highlights the importance of specific structural features for antibacterial action. While none of the synthesized molecules matched the efficacy of ciprofloxacin, some displayed moderate activity worthy of further investigation and optimization.

 

Acknowledgement

 I would like to express my sincere gratitude to Dr. Sarbast Muhamed Ahmad at the College of Pharmacy and the Day Petronic Company in Iran, as well as the Photon Center for Nano Development and Research, for their assistance in measuring the IR spectra, 1H-NMR spectral data, and 13C-NMR spectral data for this study. Furthermore, I appreciate Dr. Rebwar at the College of Education for conducting the measurements related to biological activity.

Competing  interest: No competing  of interests

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