Revolutionizing acridine synthesis: novel core-shell magnetic nanoparticles and Co-Zn zeolitic imidazolate framework with 1-aza-18-crown-6-ether-Ni catalysts

Abstract

Nanoparticles have emerged as a critical catalyst substrate due to their exceptional features, such as catalytic efficiency, high stability, and easy recovery. In our research, we have developed an innovative and environmentally friendly magnetic mesoporous nanocatalyst. Using the co-precipitation method, we produced magnetic nanoparticles (Fe₃O₄) and coated them with Zeolitic imidazolate frameworks (ZIFs) to enhance their surface area and chemical stability. The resulting substrate was functionalized with 1-aza-18-crown-6-ether and nickel metal. Our prepared catalyst has been rigorously evaluated using advanced techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmet-Teller (BET), vibrating sample magnetometry (VSM), scanning electron microscopy and energy dispersive X-ray (SEM-EDS), inductively coupled plasma (ICP), elemental mapping analysis (EMA), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). By synthesizing acridine derivatives, we have demonstrated the exceptional efficiency of our catalyst in organic compound synthesis. Through optimization, we have established the ideal parameters for catalytic processes, including catalyst amount, temperature, time, and ultrasonic use. Our catalyst has been proven to exhibit remarkable physical and chemical properties, such as porosity, temperature resistance, and recyclability. Notably, our heterogeneous nanocatalyst has shown outstanding performance and can be recycled six times without any loss in efficiency, affirming its potential in acridine.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-024-75591-y.

Introduction

The critical properties of nanomaterials that cause the creation of technology and economic and industrial growth in this field draw attention to engineered nanomaterials and their widespread use¹. Numerous diverse nanocatalysts are favored for their non-toxic, eco-friendly, and cost-efficient attributes, resulting in high yields of desired products. Convenient separation and reusability further elevate their appeal over homogeneous catalysts^2,3. Homogeneous catalysts are difficult to use because they are homo-phases with the reaction system⁴. There is great interest in the design of catalysts easily separated from the system of critical organic reactions. Developing recyclable magnetic catalysts could be a solution for proper separation and high recycling ability⁵. Catalysts are vital for synthesizing chemical compounds, but using them in large quantities can be challenging. Economic and environmental factors drive the need for selective heterogeneous catalysts to reduce production costs and minimize the disposal of catalyst waste in liquid-phase reactions⁶. The heterogeneous catalyst is environmentally friendly because it is easily separated from the reaction vessel and reused multiple times. And it has attracted a lot of attention^7,8.

Magnetic nanoparticles and heterogeneous catalytic systems are important branches in synthesizing organic compounds in the liquid phase⁹. Due to their excellent catalytic properties, environmental friendliness, and large surface area, nanocatalysts have an essential impact on organic chemistry¹⁰. Despite limited atom economy, harsh reaction conditions, and significant chemical waste, sustainability has been overlooked in the face of transformative discoveries. Nonetheless, we are delighted that modern chemistry is evolving, with a growing emphasis on minimizing harmful environmental impacts in reaction designs^11,12. Crystalline porous materials made of metal cations and anions of organic ligands are called metal-organic frameworks (MOFs)^13,14. Due to their robustness, easy tuneability, exceptional porosity, defined structure, geometry, and architecture control, these structures are becoming one of the newest materials in chemistry^15,16. Recently, many MOFs have been synthesized due to the essential features of these materials, which have great potential for use in gas storage¹⁷, water purification¹⁸, catalysts¹⁹, sensors²⁰, biomedical²¹, and electronics²², energy conversion and storage²³. Zeolitic imidazolate frameworks made of cobalt and zinc metal cations and 2-methylimidazole organic ligands are a porous structure of MOFs that have suitable properties for catalysts in producing organic compounds^24–26. ZIF67 and ZIF8 have comprehensive chemical active sites. For example, catalysts based on ZIF8 have many active sites, high surface area, and high-temperature resistance, while catalysts based on ZIF67 have a higher degree of surface modification and excellent biocompatibility^27,28.

As an appropriate and clean method, multicomponent reactions (MCRs) have been readily available to produce a wide range of organic materials in recent years. The reaction occurs in a reaction vessel composed of three or more reactants. Due to the favorable economic conditions and time savings, MCRs are a popular option^29,30. Using MCR reactions reduces the number of steps required to reach the product. Therefore, these reactions are compatible with the environment and have high efficiency³¹. There has been a significant increase in the use of ultrasound technology for modifying chemical reactions, particularly organic reactions. Ultrasonic waves in the liquid phase produce cavitation, including nucleation, growth, and collapse of bubbles. Millions of places across the liquid medium experience bubble bursting, which creates supercritical conditions with temperatures as high as 5000 K and pressures as high as 1000 atm^32–34. Ultrasonic technology is revolutionizing organic reactions due to its numerous advantages over traditional methods. These include milder reaction conditions, higher yields, faster reaction times, and cleaner reactions^35,36.

Acridine derivatives, as an essential class of heterocyclic compounds, have been investigated due to their high potential in biological activities and the treatment of several diseases, such as antimalarial³⁷, antibacterial³⁸, cytotoxic³⁹, antiviral⁴⁰, and cancer treatment by binding to DNA⁴¹ (Fig. 1). Today, many scientists are looking for new and effective drugs that are less toxic because many people in the world have cancer and viral, bacterial, and genetic diseases⁴². Acridine derivatives are an important class of nitrogen-containing heterocycles. A three-ring aromatic system that is a derivative of anthracene. Acridine forms a wide range of drugs with chemical and physical properties, low toxicity, and practical efficacy^43,44. The traditional method of synthesizing organic compounds without catalysts presents several drawbacks, such as low efficiency, prolonged reaction times, increased costs, and the use of hazardous solvents. By employing catalysts in conjunction with microwave and ultrasound waves, a more suitable and efficient approach to organic compound synthesis can be achieved. Notably, recent advancements have shown successful synthesis of acridines using microwaves and ultrasound^45,46.

Fig. 1.

Examples of acridine structures with medicinal applications.

Catalysts based on nanomaterials are one of the important components of green chemistry, especially catalysts based on magnetic nanoparticles, which are used in synthesizing organic compounds such as acridine derivatives due to their efficient recycling. To protect magnetic nanoparticles, the physical and chemical stability of colloidal systems, improve their surface, and increase their dispersion in aqueous environments, they need to modify the surface for proper performance as a catalyst^47–49. In this research, ZIF67 and ZIF8 were used to modify the surface of magnetic nanoparticles due to their suitable chemical and physical properties and high porosity and contact surface. MOFs were considered suitable coatings for heterogeneous catalysts and magnetic cores that easily separated from the reaction medium. Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni nanocatalyst is of great interest due to its excellent catalytic properties, compatibility with the environment, and large surface area due to the use of separable magnetic. The core of magnetic nanoparticles was used for easy separation of the catalyst, and the zeolite frameworks of imidazolate and 1-aza-18-crown-6-ether with a large surface area and many holes were used to modify the surface of magnetic nanoparticles nickel as an active metal was used l in catalytic processes.

Following up on our research on catalysts^50–55, we introduce Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni as a novel and green nanocatalyst for the impressive manufacturing of acridines in a one-pot reaction. As a result, this catalyst offers excellent performance, a large surface area, a reusable form, easily removed, and a simple process (Fig. 2).

Fig. 2.

Schematic of obtaining acridine derivatives via three-component reactions of aryl glyoxal, ammonium acetate, and cyclic 1,3-dione using a novel nanoporous and heterogeneous separable catalyst.

Experimental

Chemicals and instrumentations

All materials were acquired from Merck and Aldrich without any purification. Thermogravimetric analysis (TGA) was carried out on a TA Q600. X-ray diffraction (XRD) was assayed on a Philips PW1730. Morphology and elemental analysis were provided via FESEM and EDS using the MIRA III. The BET and BJH analysis were used to measure the pore volume, particle size, and surface area using a BELSORP MINI II. Infra-red spectra were obtained with a Thermo-Nicolet Nexus 670 device. VSM evaluated the magnetic properties using a Lake Shore VSM 7410. TEM micrograph was performed using a Philips CM30 instrument. The NMR spectra were provided using DRX-300 from Bruker company.

Synthesis Fe₃O₄ nanoparticles

The co-precipitation procedure was utilized to produce Fe₃O₄ in this study: A solution of FeCl₃·6H₂O (3.0 g) and FeCl₂·4H₂O (1.5 g) in H₂O (50 mL) was provided. Afterward, the mixture was sonicated for 75 min in the ultrasonic processor. NH₄OH (25%, 10 mL) was added drop-by-drop into the past solution after 15 min of starting ultrasonication (TOPSONICS ultrasonic liquid processor, made in Iran, 50 W). Subsequently, a uniform black precipitate was obtained, which was separated using a magnet. The obtained compound was rinsed in EtOH/H₂O and dried (at 60 °C).

Fabrication of Fe₃O₄@ZIF67@ZIF8

Fe₃O₄@ZIF67@ZIF8 was prepared using a sonochemical process. Co(NO₃)₂·6H₂O (2.94 g) was dissolved in methanol (35 mL), and the magnetic nanoparticles obtained from the previous step were mixed with ultrasonication for 15 min, followed by Sonication (80 W) for 30 min after the addition of 2-methylimidazole. Zn(NO₃)₂·6H₂O (2.89 g) was added to the ultrasonicated solution, and the Sonication was maintained for 30 min. The resulting product was collected with the help of an external magnet, rinsed several times with methanol, and dried at 60 °C for 6 h⁵⁶.

Preparation of Fe₃O₄@ZIF67@ZIF8@-(CH₂)₃-Cl

Fe₃O₄@ZIF67@ZIF8 (1.9 g) synthesized in the previous step was added to EtOH (40 mL) with CPTMS (3-chloropropyl-tri-methoxysilane) (2.1 g), followed by the reaction under reflux for 24 h at 60 °C. After that, the obtained product was rinsed with EtOH, and finally, Fe₃O₄@ZIF67@ZIF8@-(CH₂)₃-Cl was collected using an external magnet and dried.

Fabrication of support Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether

Fabrication of preservative with 1-aza-18-crowne-6-ether: The substance obtained from the previous step (1.1 g) was dissolved in ethanol (30 mL). Then, 1-aza-18-crowne-6-ether (1 g) was added to the solution. Finally, triethylamine (2 mL) was added to the reagent and underwent reflux for 20 h. Then dried at 70 °C for 12 h.

Fabrication of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni

Fabrication of metal catalyst: Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether (1.1 g) was dissolved with nickel salt (NiSO₄·6H₂O) at a ratio of 1 to 0.5 in ethanol (30 mL). It was placed under reflux at 60 °C for 24 h, then collected and dried.

Provision of acridines 4a–j

A round-bottom flask with a magnet was used to dissolve 2 mmol dimedone in 20 mL H₂O at 75 °C. Then, arylglyoxal (1 mmol) was added to the mixture. Ammonium acetate (1 mmol) and nanocatalyst Fe₃O₄@ZIF-67@ZIF-8@1-aza-18-crown-6-ether-Ni (10 mg) were added to the reaction medium for several minutes. The obtained solution was subjected to ultrasonication for three minutes. After three minutes of ultrasonication, the reaction medium was allowed to cool to room temperature. TLC was used to determine whether the one-pot reaction was complete. As a black deposit, a magnetic nanocatalyst was made. It was drawn apart by the magnet, yielding acridines 4a–j (75–98%) as the desired product (Table 1; Fig. 2). FT-IR, ¹H-NMR, ¹³C-NMR and the melting temperatures of the end compounds were used to identify them (The FT-IR, ¹H-NMR, and ¹³C-NMR spectra were inserted in a supplementary file).

Table 1.

Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni as a catalyst for obtaining compounds^a4a–j.

Entry	X	R	Product	Time (min)	Yieldb(%)	M.p. (oC)50,51
1	H	H	4a	4	98	247
2	4-Br	H	4b	4	96	246
3	4-Me	H	4c	5	92	251
4	4-MeO	H	4d	4	94	233
5	4-NO2	H	4e	4	91	294
6	H	CH3	4f	3	98	152–155
7	4-Br	CH3	4g	4	97	156–158
8	4-Me	CH3	4h	4	92	141–143
9	4-MeO	CH3	4i	5	98	110–113
10	4-NO2	CH3	4j	5	95	176–179

^aReaction status: Ammonium acetate (1 mmol), cyclic 1,3-dione (2 mmol), aryl glyoxal (1 mmol), H₂O (20 mL), and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (10 mg) in EtOH (5 mL) under ambient status.

^b The yields corresponded to the isolated product.

Results and discussion

The heterogeneous catalyst was prepared with magnetic nanoparticles coated with Co/Zn-ZIFs and placed 1-aza-18-crown-6-ether-Ni on them. Necessary investigations were done to identify the structure of this catalyst. Then, the prepared catalyst was used to prepare acridines, and various parameters such as solvent effect, amount of catalyst, temperature, and time were investigated and optimized. A brief pathway of the catalyst synthesis state is presented in Fig. 3.

Fig. 3.

Stepwise synthesis of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Catalyst characterization

The morphological and chemical structure, thermal, and magnetic virtues of nanocatalyst were successfully assessed by various techniques, including FT-IR, XRD, TGA, BET, SEM-EDS, EMA, TEM, ICP, and VSM.

FTIR spectroscopy analysis

First, the type of bonds among components and function groups have been defined by the interaction of IR light with the material. FT-IR spectroscopy is the analysis of infrared light interacting with a molecule. Organic compounds absorb red light radiation that corresponds to these vibrations in terms of energy. Figure 4 is an infrared spectrum obtained, a graph of the intensity of the infrared spectrum measured against the wavelength of light. Information on group function and interactions between molecules has been obtained by measuring the vibrations of atoms. Figure 4a is related to magnetic nanoparticles synthesized in the first step. The vibration in 558 cm⁻¹ is related to Fe–O, and the bands of 1613 and 3414 cm⁻¹ are related to bending and stretching O–H connections, which are placed on the surface of Fe₃O₄ nanoparticles, confirming the formation of Fe₃O₄ nanoparticles^57,58. According to Fig. 4b of the spectrum after coating magnetic nanoparticles with Co/Zn-ZIFs, a band at 2920 cm⁻¹ can be assigned to the C–H bond vibration characteristic. The characteristic absorption bands at 1570 cm⁻¹ for C = N and 1136, 430, 559, and 685 cm⁻¹ correspond to C–N, Fe–O, N-Zn, and N-Co, respectively, which indicates the existence of Co/Zn-ZIFs compounds⁵⁹. C–H Stretching vibrations appeared in Fig. 4c at 2927 cm⁻¹. A band relevant to Si–O and C–Cl connections was confirmed at 820 and 681 cm^−1, indicating the linker’s successful connection (CPTMO). According to Fig. 4d, related to ligand binding1-aza-18-crown-6-ether, the curve associated with group N–H stretching and bending was seen in 1579 cm⁻¹. Moreover, the peaks observed at wavelengths 1173 and 1209 cm⁻¹ are related to the stretching vibrations of C–N. After connecting the crown ether to carbon, the peak at 680 cm⁻¹, corresponding to C–Cl, was not observed to show that the correct connection of crown ether to carbon was observed. Finally, the peaks observed in Fig. 4e curve Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni at the wavelengths of 598 and 692 cm⁻¹ correspond to Ni–O and N–Ni respectively, confirming the metal’s successful stabilization on the ligand⁵⁴. The changes in the spectrum during the synthesis of different catalyst stages with the increase of various compounds confirm the change in the structure and proper obtaining of the catalyst.

Fig. 4.

Infra-red spectra acquired for Fe₃O₄ (a), Fe₃O₄@ZIF-67@ZIF-8 (b), Fe₃O₄@ZIF67@ZIF8@-(CH₂)₃-Cl (c), Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether (d), and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (e).

X-Ray diffraction analysis

X-ray diffraction is a non-destructive and widely accepted method of determining the crystal structure of materials, providing vital information on their properties. In the XRD pattern of Fe₃O₄ (Fig. 5a) structure with inverted spinel structure, the six peaks appeared at around 2θ = 30°, 35°, 43°, 54°, 57°, and 63°, which correspond to diffraction of the (158), (445), (109), (37), (81), and (115). Figure 5b demonstrates the XRD results for the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni, indicating that six peaks at values of 7.5°, 10°, 13°, 14°, 15°, 18°, 22°, 23°, and 35°, refer to (217), (162), (127), (165), (150), (256), (78), (79), (117) crystal surface, respectively. In addition, the presence of Fe₃O₄@ZIF67@ZIF8 in the compound structure has been confirmed. Collected coherently scattered peak intensities agree with the crystalline spinel form of Fe₃O₄ nanoparticles (JCPDS Card No. 01-1111) and ZIF67@ZIF8 (JCPDS Card No. 00-062-1030). The results show that the crystal anatomy stable tetrahedral magnetic nanoparticles were maintained after surface modification. With the appearance of the peaks related to ZIF67 and ZIF8, based on the results and the structure of Fe₃O₄@ZIF67@ZIF8, the crystal structure of the catalyst has been confirmed^59,60.

Fig. 5.

The XRD pattern of Fe₃O₄ (a) and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (b).

Thermal gravimetric analysis

Using thermal gravimetric analysis, the changes in the weight of the catalyst were recorded due to temperature changes (Fig. 6). Furthermore, it was presented as two graphs (TGA-DTG) as output. The results of the TGA analysis were reported as a curve of weight changes according to temperature changes (25–800 °C). The results obtained from these curves were expressed in two forms of the initial report. At each stage of the weight change, the initial and final temperatures were determined as the starting and ending temperatures of the thermal event. The amount of weight loss in each event was expressed as a percentage. The first 10% of the weight loss is due to the removal of absorbed organic solvents below 200 °C. 10% mass reduction before 200 degrees indicates the thermal stability of the synthesized catalyst up to 200 degrees. The weight loss (20%) between 200 and 600 degrees is related to the removal of organic substances and the removal of bonds Fe₃O₄@Co/Zn-ZIFs and nickel complexes. The last weight loss at 605.47 °C can be related to catalytic decomposition and the change of crystal phase probability. Therefore, it can be concluded that organic agents cover the sample’s surface, and a 31% reduction in the weight of the sample up to a temperature of 600 degrees indicates the appropriate temperature resistance that the sample shows.

Fig. 6.

Thermal gravimetric analysis of the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

N2-physical adsorption

A method capable of absorption was considered to determine the porosity of the catalyst. The volumetric method was used to measure the adsorption isotherm. The results of this measurement have been announced as a graph showing the relationship between the amount of absorption in terms of pressure at constant temperature. According to the type of graph, the absorption isotherm is type IV (Fig. 7). There is a relationship between the sample and the porosity of the firm and mesoporous adsorbent at (P/P_o = 0.02–0.99) with H₂-type hysteresis loops. The pore volume (0.1035 cm³.g⁻¹), the surface area (40.411 m² g⁻¹), and the related pore diameter (10.247 nm) of the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni catalyst were obtained from the by BET/BJH analyses. Today, due to the widespread use of porous materials and incredibly porous nanostructures, it has become a necessary tool in the field of catalysts. Due to the substantial porosity in the zeolite imidazolate frameworks and the addition of nanoparticles, the porosity and surface area in the catalyst increased. The corresponding pore diameter distribution in nanometer wavelength was determined, which confirms the nanoporous structure⁶¹.

Fig. 7.

Represents the nitrogen adsorption and desorption isotherms of the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Vibrating sample magnetometry analysis

A vibrating sample magnetometer was utilized to estimate the magnetic attributes of the catalyst. The VSM device works based on Faraday’s law of induction. This law states that a change in the magnetic field creates an electric field. By measuring the induced electric field, it is possible to acquire information about the changes in the magnetic field. In the diagram presented, the horizontal axis H is Oe with an Oersted unit, and the vertical axis M is an emu g⁻¹ unit (Fig. 8). According to the results shown in the diagram, the magnetic saturation of Fe₃o₄ and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni is evaluated. The value of Ms for Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni is 28 emu g⁻¹. The Ms value for the catalyst was lower than that of the uncoated magnetic nanoparticles (22 emu g⁻¹). This result seems to confirm Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni that surrounds the Fe₃O₄ surface. Therefore, this reduction is for the Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni coating on the surface of the primary magnetic nanoparticles for the catalyst. According to the magnetic saturation diagram, the hysteresis loop is not formed, and the sample is paramagnetic. In the presence of an external magnet, paramagnetic materials become magnetized on a macroscopic scale due to the alignment of the magnetization of the constituent particles with the direction of the external magnet.

Fig. 8.

The VSM data for Fe₃O₄ (a) and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (b).

Energy-dispersive spectroscopy

EDS analysis confirmed the presence of Iron, Nickel, Nitrogen, Carbon, Oxygen, Silicon, Cobalt, and Zinc elements in the catalyst structure. In Fig. 9, the presence of elements C (16.34), Fe (25.56), N (3.95), Si (2.48), O (47.44), Ni (2.23), Co (2.30), and Zn (2.17) was confirmed. According to the FTIR analysis, the presence of peaks related to Ni and O bond and nickel on the catalyst’s surface using EDS and ICP-OES determined the characteristic value of nickel to be 3.2%. The catalyst preparation has been completed because nickel metal and other elements have a suitable weight% and proper dispersion.

Fig. 9.

EDX results of the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Scanning electron microscope

A scanning electron microscope was utilized to record the image using electrons, with high magnification and precision, and to determine the morphology and surface characteristics in nanometer dimensions. Images from the external surface of the sample were captured as two-dimensional images. The photos are presented in 195–501 nm and 5 μm scales. Using SEM results, morphological characteristics such as the structure of pores and cavities were investigated. According to Fig. 10a, the samples of newly synthesized magnetic nanoparticles have a uniform spherical shape with a particle size of 15 nm. SEM microscopic images of the catalyst sample (Fig. 10b-d( show the particle size of 23–50 nm in cloud state. For the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni, the spherical particles have increased in size and have a cloud state due to the modification of the surface of the magnetic nanoparticles by binding the ligand Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni to the Fe₃O₄ nanoparticles. By examining the SEM results of the sample surface with diverse magnifications and comparing them with the image Fe₃O₄, it can be observed that the contact surface of the catalyst increases with the increase in particle size. The attendance of holes and the spherical structure of the catalyst were confirmed.

Fig. 10.

SEM image of Fe₃O₄ (a) and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (b–d).

Transmission electron microscopy

A TEM microscope with an electron beam was used to create high-resolution images at the nanoscale to observe the fine details, precise structure, and different catalyst components. The uniform size and morphology of the prepared substances, as shown in the obtained image (Fig. 11), demonstrate the significance of the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni nanocatalyst procedure and its application to advance the fabrication of acridines. It has also shown that, within a reasonable period, the production with homogeneous morphology was successfully achieved. The particle size distribution of Fe3O4@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni shows that the average size is around 10–22 nm (Fig. 11). The similarity between the newly produced catalyst’s TEM images and those obtained after six recycling steps demonstrates the nanocatalyst structure’s durability and the particles’ efficient dispersion. Thus, different structures in Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni can be identified by their dark regions covered in brilliant outer layers and their cross-linking distances, which result in the appearance of holes.

Fig. 11.

TEM image of synthesized Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Fabrication of acridine-1,8(2H,5H)-diones by catalytic amounts of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni

From the structural studies of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni, we’ve expected that this reagent could serve as a suitable catalyst for the acridine derivatives synthesized using aryl glyoxal, ammonium acetate, and cyclic 1,3-dione.

For this purpose, the model reaction was selected, and its various conditions were optimized under the impact of diverse empirical parameters containing various temperatures, the amount of newly synthesized catalyst, the solvent, and ultrasound. The results obtained are outlined in Table 2. The reaction was conducted without a catalyst at the reaction vessel for 23 h (entry 1, Table 2).

Table 2.

Various parameters for the establishment of 4a.

Entry	Catalyst loading (mg)	Solvent	Temperature (°C)	Time (min)	Yield (%)
1	0	H2O	75	23 h	Trace
2	5	H2O	75	68	88
3	10	H 2 O	75	5	97
4	10	H 2 O	75	3	98
5	15	H2O	75	30	90
6	20	H2O	75	18	94
7	10	Ethanol	90	80	75
8	10	Toluene	110	45	85
9	10	n-Hexane	85	60	80

^aReaction status: Ammonium acetate (1 mmol), cyclic 1,3-dione (2 mmol), aryl glyoxal (1 mmol), H₂O (20 mL), and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (10 mg) in EtOH (5 mL) under ambient status.

^bThe yields corresponded to the isolated product.

Carrying out the reaction with less than 10 mg (entries 2, Table 2) is associated with a long reaction time and a low yield percentage. Without using ultrasonic, the reaction time is longer than when using ultrasonic (entry 3, Table 2). The best conditions were created for preparing acridines when the reaction was performed in 3 min in the presence of the green solvent of water and at a temperature of 75 ^oC using 10 mg of catalyst and under ultrasonic radiation (power of 85 W, entry 4, Table 2). According to the reaction conditions and its repetition with a different amount of catalyst, the amount of catalyst more than 10 mg did not increase the reaction yield (entries 5 and 6, Table 2). The reaction with organic solvents has been checked using ethanol, toluene, and n-hexane, respectively (Table 2 and entries 7–9). The temperature increases to 110 degrees, indicating a high reaction time and a low percentage of the product produced for non-aqueous solvents.

By obtaining the right amount of catalyst, the time, temperature of the reaction, and the proper solvent to carry out the reaction, this reaction was carried out with different reagents of aryl glyoxal (electron-donating and electron-drawing substituents) with cyclic 1,3-dione and ammonium acetate. (Table 1)

The reaction mechanism of obtaining acridine derivatives using the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni catalyst is shown in Fig. 12. According to the proposed mechanism, firstly, the C = O of aryl glyoxal 1a–e activated with nanoparticles; after the Knoevenagel condensation among the enolic form of cyclic 1,3-dione 2a, b and activated aryl glyoxal 1a–e by dewateration occurs, and generate I. Afterward, the second enolic form of cyclic 1,3-dione 2a, b via Michael reaction was added to I to produce II. In the next stage, due to the reaction of II with CH₃CO₂NH₄ (3), dehydration generates III. Afterward, the intramolecular nucleophilic assail of the –NH₂ group on the carbonyl group with the effect of the catalyst causes the fabrication of a ring, and eventually, intramolecular cyclization with the water-removal was done, and the favorable products 4a–j and catalyst was obtained^54,62.

Fig. 12.

Mechanistic pathway representing the synthesis of compounds 4a–j.

Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni was compared to other published literature to assess the system’s capabilities and efficiencies in the preparation of acridines (Table 3). According to the results obtained from this comparison, Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni catalyst performed better and was more suitable in the presence of green water solvent.

Table 3.

Comparison of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni with other published data.

Entry	Catalyst	Solvent	Time (min)	Yield (%)	Reference
1	Alginic acid	Ethanol	6 h	83	63
2	MW	H2O	3 h	81–90	64
3	Ru-doped hydrotalcite	H2O	36 h	90	65
4	MSrGO NCs	Solvent-free	2.5 h	91	66
5	Pt NPs@GO	DMF	1 h	93	67
6	Fe3O4	Solvent-free	25	85	68
7	Nickel cobalt ferrite	Ethanol/H2O	25	95	69
8	Fe 3 O 4 @Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni	H 2 O	3	98	This research

^aReaction status: Ammonium acetate (1 mmol), cyclic 1,3-dione (2 mmol), aryl glyoxal (1 mmol), H₂O (20 mL), and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (10 mg) in EtOH (5 mL) under ambient status.

^bThe yields corresponded to the isolated product.

To investigate the role of Ni metal as an active metal in the catalyst structure, the model reaction was carried out in the presence of Fe₃O₄, Fe₃O₄@ZIF67@ZIF8, Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether, and Ni(NO₃)₂.6H₂O as a catalyst (Table 4), with Examining the results of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni containing Ni metal is the best catalyst for the preparation of acridine.

Table 4.

The catalytic role of metal (ni) in reactions in the presence of the catalyst.

Entry	Catalyst	Solvent	Time (min)	Yield (%)
1	Fe3O4	H2O	120	83
2	Fe3O4@ZIF67@ZIF8	H2O	120	75
3	Fe3O4@Co/Zn-ZIFs@1-aza-18-crown-6-ether	H2O	100	85
4	Fe3O4@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni	H2O	3	98
5	Ni(NO3)2.6H2O	H2O	60	90

^aReaction status: Ammonium acetate (1 mmol), cyclic 1,3-dione (2 mmol), aryl glyoxal (1 mmol), H₂O (20 mL), and Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni (10 mg) in EtOH (5 mL) under ambient status.

^bThe yields corresponded to the isolated product.

According to the analyses performed by SEM, TEM, FTIR, and XRD on the recovered catalyst (Fig. 13), the similarity of the structure and the results of the studies conducted after the recovery of the catalyst with the newly synthesized catalyst is of interest, and the recovery efficiency of the catalyst after six times of use is 80–82%.

Fig. 13.

Recycling of Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Recyclability

The reuse of catalysts leads to a significant reduction in industrial waste production, thereby mitigating environmental pollutants. This process reduces costs related to preparing and using new catalysts and industrial waste disposal and minimizes the energy required for producing new catalysts. In essence, catalyst recycling is instrumental in cost reduction, environmental protection, and enhancing manufacturing productivity.We investigated the reusability of the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni for the reaction between ammonium acetate, and cyclic 1,3-dione, aryl glyoxal under the selected status. The catalyst was magnetically isolated quickly and easily after the completion of the reaction by a magnet and H₂O-rinsed and dried at 75 °C. Finally, six new runs were conducted without losing catalyst properties using the awarded catalyst (Fig. 13). According to the information obtained from the recycling of the catalyst and product yield in the last cycle and the decrease in the percentage of the yield of the product compared to the previous stages, the reduction in the efficiency of the catalyst in the last stages of recycling can be attributed to the decrease in the amount of nickel on the surface of the catalyst due to washing. By examining the ICP analysis, the amount of nickel metal decreased to 2.5 after the recycling steps, which indicates the reduction of nickel metal. The result obtained from the TEM/SEM images, FT-IR spectrum, and XRD pattern showed that the recovered catalyst did not change and was similar to the structure of the new catalyst. (Fig. 14)

Fig. 14.

Image of analysis FTIR (a), XRD (b), SEM (c), and TEM (d) on the recovered Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Hot filtration

During the synthesis of acridines, a hot filtration was performed to evaluate the magnetic nanocatalyst’s heterogeneity and the Ni mixture’s leaching, as arylglyoxal, ammonium acetate, and cyclic 1,3-dione reacted. Furthermore, the product yield (33%) was obtained within 3 min of the reaction. The catalyst was then separated, filtered, and given a period to react. No further reactions were detected after the hot filtration. The fact that the reaction’s efficiency in this instance was 32% confirms minimal nickel leaching. (Fig. 15)

Fig. 15.

Hot filtration test for Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni.

Conclusion

In this research, we present a new heterogeneous catalyst Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni. XRD, TEM, TGA, FT-IR, BET, SEM-EDS, EDS, ICP, and VSM techniques have successfully evaluated the prepared catalyst. Acridine derivatives were synthesized in the presence of the catalyst to investigate the efficiency of the new catalyst in synthesizing organic compounds with high efficiency. Acridine derivatives were prepared through one-pot, multicomponent reactions of aryl glyoxals, ammonium acetate, and cyclic 1,3-dione in water under mild conditions using ultrasound radiation at 75 °C. Exceptional product yields of 98% are achieved within just 3 min. The Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Nicatalyst exhibits outstanding recyclability, maintaining its catalytic activity even after at least six reuse cycles. Energy sources were used to synthesize acridine derivatives, among which ultrasonic demonstrated the best efficiency. Indeed, ultrasonic irradiation demonstrating a synergistic effect with Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni nanocatalyst accelerates the reaction rate. According to the analyses performed by SEM, TEM, FTIR, and XRD on the recovered catalyst, the similarity of the structure and the results of the studies conducted after the recovery of the catalyst with the newly synthesized catalyst is of interest, and the recovery efficiency of the catalyst after six times of use is 80–82%. Some of the advantages of this catalyst are ease of use, high product yield with low catalyst consumption, environmental friendliness due to easy separation, and recycling several times without reducing efficiency. According to the investigations carried out in this research, the Fe₃O₄@Co/Zn-ZIFs@1-aza-18-crown-6-ether-Ni catalyst can be a suitable catalyst for obtaining acridines.

Electronic supplementary material

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Author contributions

Fatemeh Asadzadeh: Data curation, Investigation, Methodology, Writing–original draft. Ahmad Poursattar Marjani: Project administration, Conceptualization, Investigation, Supervision, Writing–review & editing.

Data availability

All data have been given in the article and supporting information.

Declarations

Competing interests

The authors declare no competing interests.