Ionic liquid functionalized magnetic organosilica nanocomposite: A powerful and efficient support for manganese catalyst

Journal Pre-proof Ionic liquid functionalized magnetic organosilica nanocomposite: A powerful and efficient support for manganese catalyst Maryam Neysi, Dawood Elhamifar, Meysam Norouzi PII:

S0254-0584(19)31399-9

DOI:

https://doi.org/10.1016/j.matchemphys.2019.122589

Reference:

MAC 122589

To appear in:

Materials Chemistry and Physics

Received Date: 15 April 2019 Revised Date:

5 November 2019

Accepted Date: 26 December 2019

Please cite this article as: M. Neysi, D. Elhamifar, M. Norouzi, Ionic liquid functionalized magnetic organosilica nanocomposite: A powerful and efficient support for manganese catalyst, Materials Chemistry and Physics (2020), doi: https://doi.org/10.1016/j.matchemphys.2019.122589. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.

Graphical abstract

Ionic liquid functionalized magnetic organosilica nanocomposite: A powerful and efficient support for manganese catalyst

Maryam Neysi, Dawood Elhamifar* and Meysam Norouzi

Department of Chemistry, Yasouj University, Yasouj, 75918-74831, Iran E-mail: [email protected]

Abstract: A novel Mn-containing ionic liquid and ethyl based magnetic organosilica with coreshell structure (Fe3O4@OS/IL-Mn) is prepared, characterized and applied as powerful and recoverable nanocatalyst. The Fe3O4@OS/IL-Mn was prepared via simultaneous coating of tetramethoxysilane

(TMOS)

and

1,2-bis(triethoxysilyl)ethane

(BTEE)

over

magnetite

nanoparticles (MNPs) followed by treatment with ionic liquid and manganese acetate. This catalyst was characterized using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), energy dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (PXRD), vibrating sample magnetometer (VSM) and FT-IR spectroscopy. The Fe3O4@OS/ILMn was used as an efficient catalyst for the one-pot preparation of biologically useful 2Hindazolo-[2,1-b]-phthalazin-trions under green conditions. The recoverability, reusability and durability of the designed catalyst have also been studied under applied conditions.

Keywords: Magnetic organosilica, Core-shell nanostructure, Supported ionic liquid, 2Hindazolo[2,1-b]phthalazin-triones, Green synthesis

1

1. Introduction Magnetic iron oxides are among the best important particles in catalytic world due to their paramagnetic properties, low toxicity, surface modification ability, easy preparation and low cost [1-7]. Today, in a variety of medical fields including cell and protein sorting, tumor treatment and control of the genes, magnetic nanoparticles are used due to their small size, high activity and high level of contact as well as penetrate easily into cells and tissues[8]. The strategy of magnetically recoverable of magnetic nanocatalysts has attracted much attention over other methods such as filtration and centrifugation due to this is economical, easy, saves time and energy as well as prevents the catalyst losing. Recent advances in the synthesis of these particles have led to their widespread use in oxidation, reduction, coupling reactions and so on[9, 10]. However, the Fe3O4 nanoparticles have great tendency to aggregate and deform in some organic solvents during applied conditions. These particles are also unstable in both acidic and basic media[11, 12]. Due to these problems, the unmodified MNPs are usually used in higher amount in catalytic organic transformations [13, 14]. To overcome these restrictions, surface modification of the MNPs by surfactants, carbon, silica and metal oxides have been recently reported [15-20]. Among these, silica is the most commonly used material to cover the Fe3O4 NPs, due to its high ability to prevent magnetic accumulation in solution, high chemical stability, its high ability to modification with different functional groups, tuning its structural order, low toxicity, low cost, high thermal stability and environmental compatibility[5, 21-30]. Especially, the use of organosilica precursors to modify magnetic Fe3O4 NPs is more attracted, due to the corresponding magnetic core-shells have advantages of both MNPs and supported organic functional groups as well as have high hydrophobicity to adsorb chemicals and catalyze organic transformations. To obtain organosilica-coated magnetic NPs with core-shell structure, the simultaneous co-condensation of mono- or bis(trialkoxysilyl)organic units and tetraalkoxysilanes 2

(TMOS or TEOS) over magnetic Fe3O4 NPs is an effective and desirable approach. To date a number of magnetic organocsilica particles have been prepared and applied as catalyst and/or support in chemical processes. Some of recently developed catalytic systems are Fe3O4@PhSO3H[31], Cu/SB-Fe3O4[32], Fe3O4@MCM-41-SO3H[33], Fe3O4@MCM-41-Im@MnPor[34], AIL-SCMNPs[35],PdCu@GQD@Fe3O4[36],

Fe3O4@SiO2–PEG/NH2[37],

MNPs–ligand–

Cu[38] and PPY/Fe3O4/CNT[39]. On the other hand, the heterocycles are an important class of organic compounds that have a wide range of applications in biological, chemical and industrial processes[40-42]. Due to many uses of heterocyclic compounds in the daily life, so much efforts have been made to design and synthesize of them in recent years[43-47]. The 2H-indazolo[2,1-b]phthalazin-triones are one of the most important compounds of heterocycles that have several biological and morphological properties including antibacterial, anticancer, antimicrobial, anticonvulsant, anti-inflammatory and cardiovascular activity[48-53]. According to these facts, the preparation of 2H-indazolo[2,1b]phthalazin-triones is one of very important subject in organic chemistry. To date many catalytic systems have been reported for the preparation of these compounds under different conditions. A number of recently heterogeneous catalytic systems applied in this matter are silica sulfuric acid[50], SBA-15-Ph-SO3H[54], MNPs-guanidine[55], PMA-SiO2[56], Fe3O4@silica sulfuric acid[57]and IL@nano-SiO2[58]. The use of water as solvent in organic reactions has also attracted a great deal of interest from both economical and industrial point of view, due to the water is a green, nontoxic, easily available, environmentally friendly and safe solvent. Moreover, for some organic reactions, water shows better selectivity and reactivity than organic solvents[59].

3

According to aforementioned notes as well as the importance of biologically active 2Hindazolo[2,1-b]phthalazin-triones and in continuous of our recent studies in the preparation and applications of supported catalytic systems [31, 60-65], herein, we have reported the preparation and characterization of a novel magnetic bifunctional ethyl-based organosilica supported alkylimidazolium ionic liquid/manganese complex (Fe3O4@OS/IL-Mn). The Fe3O4@OS/IL-Mn was successfully applied as an efficient and recoverable nanocatalyst in the synthesis of 2Hindazolo[2,1-b]phthalazin-triones in water as green solvent.

2. Experimental section 2.1. General All chemicals including iron (II) chloride tetrahydrate (99%), iron (III) chloride hexahydrate (98%),

ammonia

(25%),

bis(triethoxysilyl)ethane

concentrated

(BTEE),

HCl,

Mn(OAc)3.2H2O,

tetramethoxysilane dimethyl

(TMOS),

sulfoxide,

toluene

1,2and

benzaldehyde derivatives were purchased from Fluka and Merck companies. The IR spectra were obtained using FT-IR JASCO-Model 680 spectroscopy. The surface morphology of the synthesized nanoparticles was measured by scanning electron microscopy (SEM) model EM3200. The thermal gravimetric analysis (TGA) was measured from room temperature to 800 °C by NETZSCH STA 409 PC/PG. The powder X-ray diffraction (PXRD) analysis was performed using the Philips XPert Pro X-ray diffractometer. The EDX analysis was performed using EDS Sirius SD. Transmission electron microscopy (TEM) image was taken on a FEITECNAI 12 BioTWIN microscope. Ultrasonic model KMM1-120WE301 was used to disperse the particles and to perform the reactions.

4

2.2. Preparation of Fe3O4 supported ethyl-based organosilica (Fe3O4@OS) For this, firstly magnetic Fe3O4 NPs were prepared according to our previous procedure with a slight modification [31]. Then, Fe3O4 (0.25 g) was dispersed in a solution of water (20 mL) and EtOH (75 mL) at room temperature for 30 min in an ultrasonic bath. Next, ammonia (2 mL, 25%) was added and it was sonicated. To the resulting mixture, TMOS (0.4 mL) and BTEE (0.4 mL) were added dropwise and simultaneously. The resulting combination was stirred for 16 hours at room temperature. After these steps, the obtained product was separated using an external magnet, washed several times by ethanol and water and dried at 70 °C for 12 h. The final material was denoted as Fe3O4@OS. 2.3. Preparation of Fe3O4@OS modified with ionic liquid groups (Fe3O4@OS/IL) For the preparation of Fe3O4@OS/IL, magnetic Fe3O4@OS nanoparticles (0.25 g) were added in toluene and sonicated for 20 min at room temperature. Then, 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride (0.33 mmol) was added and the resulting mixture was refluxed under argon atmosphere for 24 h. After cooling this mixture to room temperature, the obtained material was magnetically separated, washed several times with ethanol and dried at 70 °C for 12 h. The final material was denoted as Fe3O4@OS/IL.

2.4. Preparation of Fe3O4@OS supported ionic liquid/manganese complex (Fe3O4@OS/ILMn) In order to preparation of manganese containing Fe3O4@OS/IL nanocatalyst, Fe3O4@OS/IL (0.25 g) was added in DMSO (20 mL) and completely dispersed at room temperature for 20 min

5

in an ultrasonic bath. Next, Mn(OAc)3.2H2O (1.5 mmol) was added into reaction vessel and the resulting mixture was stirred at room temperature for 24 h. This combination was then stirred at 80 °C for 2 h. The obtained product was magnetically separated, washed completely with DMSO, dried at 70 °C for 12 h and denoted as Fe3O4@OS/IL-Mn. According to EDX and ICP analyses the loading of manganese onto material surface was calculated to be 0.44 mmol Mn/g.

2.5. Procedure for the synthesis of 2H-indazolo[2,1-b]phthalazin-triones in the presence of Fe3O4@OS/IL-Mn catalyst To do this, 0.7 mol% of the Fe3O4@OS/IL-Mn catalyst was added into a reaction vessel containing aldehyde (1 mmol), phthalhydrazide (1 mmol), dimedone (1.5 mmol) and water (5 mL). The resulting mixture was sonicated at 50 °C in an ultrasonic bath and the reaction progress was monitored by TLC. After completion of the reaction, hot ethanol (10 mL) was added into the reaction vessel and the catalyst was removed using an external magnet. The catalyst-free solution was placed into an ice bath to precipitate and/or crystalize desired products. Pure products were obtained after recrystallization in EtOH.

2.6. Procedure for the recovery of the Fe3O4@OS/IL-Mn catalyst To do this, the Fe3O4@OS/IL-Mn catalyst was added into a mixture of aldehyde, phthalhydrazide, dimedone and water at 50 °C in an ultrasonic bath. The reaction progress was monitored by TLC. After completion of the reaction, the catalyst was separated using an external magnet. The pure product was obtained as previous procedure and the yield was calculated. The

6

recovered catalyst was then dried and subsequently reused under the similar conditions as the first step. These steps were repeated several times and the corresponding yields were calculated. 3. Results and discussion In order to synthesize the Fe3O4@OS/IL-Mn catalyst, magnetite nanoparticles were first modified with a mixture of bis(triethoxysilyl)ethane and tetramethoxysilane to deliver Fe3O4@OS nanomaterial. The Fe3O4@OS was then reacted with alkyl-imidazolium ionic liquid and manganese acetate to give Fe3O4@OS/IL-Mn catalyst (Scheme 1). According to our previous studies, the XPS analysis should two signals at bending energies of 654.2 and 642.6 eV corresponding to Mn 2P1/2 and Mn 2P3/2, respectively, conforming that the oxidation state of manganese is Ш [66, 67].

7

1)H2O, EtOH, 30 min 2)NH3, RT

Fe3O4

Toluene, IL

Fe3O4

3)TMOS, BTEE, 16 h

100 oC, 24 h

Fe3O4@OS

1) DMSO, RT, 20 min 2) Mn(OAc)3.2H2O, RT, 24 h

Fe3O4

3) 80 oC, 2 h

Fe3O4@OS/IL

Fe3O4 Fe3O4

Fe3O4@OS/IL-Mn

TMOS: Tetramethoxysilane BTEE: 1,2-Bis(triethoxysilyl)ethane IL: (MeO)3Si

N

N

Cl Me

: -CH2CH2:

O O O

Si

N

N

[Cl Mn(OAc)3] Me

Scheme 1. Preparation of the Fe3O4@OS/IL-Mn nanocatalyst The chemical and structural properties of the Fe3O4@OS/IL-Mn nanocatalyst were investigated using FTIR, VSM, SEM, TGA, EDX and PXRD analyses. The FT-IR spectra of Fe3O4, Fe3O4@OS and Fe3O4@OS/IL-Mn materials are seen in Figure 1. As shown, for all samples a signal is observed at 588 cm-1 that is assigned to Fe-O bond of magnetic particles. Moreover, the broad peak observed about 3419 cm-1 is due to stretching vibration of O-H bonds of adsorbed water and also OH bonds of Si-OH moieties. For Fe3O4 and Fe3O4@OS samples, the new peaks observed at 923 and 1078 cm-1 are related to the symmetric and asymmetric stretching vibration of Si-O-Si bonds. For the latter materials, the signal observed at 2923 cm-1 is corresponded to 8

stretching vibration of aliphatic C-H bonds. For the Fe3O4@OS/IL-Mn, the peaks cleared at 1417 and 1623 cm-1 are, respectively, related to C=C and C=N bonds of imidazolium rings. These results confirm the successful incorporation/immobilization and high stability of ethyl and ionic liquid groups into/onto material framework.

Figure 1. FTIR spectra of Fe3O4 (a), Fe3O4@OS (b) and Fe3O4@OS/IL-Mn (c) materials

The wide angle powder X-ray diffraction (PXRD) analysis showed that the Fe3O4@OS, Fe3O4@OS/IL and Fe3O4@OS/IL-Mn materials have a standard crystalline structure, the same as magnetite nanoparticles (Figure 2). As shown, for all samples seven spinel peaks are observed at 2θ of 30.30, 36, 43.5, 54.5, 57.5, 63 and 75 degrees corresponding to the Miller indices of 220,

9

311, 400, 422, 511, 440 and 533, respectively. This XRD pattern is in good agreement with the pattern of Fe3O4 nanoparticles confirming high stability of these NPs during preparation of catalyst. Also, the decrease in the intensity of PXRD peaks for Fe3O4@OS, Fe3O4@OS/IL and Fe3O4@OS/IL-Mn indicates successful immobilization of organic and Mn(OAc)3 species on the Fe3O4 support.

Figure 2. The powder X-ray diffraction pattern of a) Fe3O4, b) Fe3O4@OS, c) Fe3O4@OS/IL and d) Fe3O4@OS /IL-Mn materials

10

The scanning electron microscopy (SEM) analysis showed the presence of spherical particles with the average size of 92 nm for the catalyst (Figure 3). These type nanoparticles are important candidates in the fields of adsorption, catalysis and also chromatography.

Figure 3. The SEM image of the Fe3O4@OS/IL-Mn nanocatalyst

The TEM image of the designed catalyst also showed spherical particles with core-shell structure (Figure 4). As shown, this image indicates black cores (magnetite NPs) surrounded with gray shell (organosilica layer).

11

Figure 4. The TEM image of the Fe3O4@OS/IL-Mn nanocatalyst

The energy-dispersive X-ray (EDX) spectroscopy of the Fe3O4@OS/IL-Mn nanocatalyst showed the signals of iron, oxygen, silicon, carbon, chlorine, nitrogen and manganese (Figure 5). These elements are corresponded to iron oxide, ethyl-based organosilica, ionic liquids and manganese complex confirming the high stability and well incorporation/immobilization of aforementioned species into/onto material network.

12

Figure 5. The EDX spectroscopy of the Fe3O4@OS/IL-Mn nanocatalyst

The vibrating sample magnetometer (VSM) analysis of Fe3O4@OS/IL-Mn was also performed to study the magnetic properties of the catalyst (Figure 6). This showed a magnetic saturation value of about 34 emu/g confirming good magnetic ability of designed catalyst as well as its easy separation and recoverability through a magnetic field. This is an excellent advantage especially in the catalytic processes.

13

Figure 6. The VSM analysis of the Fe3O4@OS/IL-Mn nanocatalyst

To study the thermal stability, in the next the thermal gravimetric analysis (TGA) of the catalyst was performed (Figure 7). The first weight loss observed at temperature below 150 °C (about 2%) is corresponded to removal of water and alcoholic solvents remained during catalyst preparation. The second weight loss observed at 250–370 °C (about 2%) is related to elimination of ionic liquid groups that are grafted on the material surface. The main weight loss cleared in the range of 380-520 °C (about 6%) is attributed to removal of ethyl moieties incorporated in the material framework. The small weight loss at temperature more than 530 °C is attributed to the ethyl group’s residue as well as water molecules produced via condensation of OH-surfaces at high temperatures. In the latter case, the Si-OH are condensed to form Si-O-Si bonds and water molecules. It is also important to note that the final product obtained after total thermal decomposition is Fe3O4@SiO2. 14

Figure 7. The TG analysis of the Fe3O4@OS/IL-Mn nanocatalyst

After successful characterization, the catalytic application of the Fe3O4@OS/IL-Mn was investigated in the synthesis of biologically active 2H-indazolo-[2,1-b]-phthalazin-trions. To optimize the reaction conditions, the effect of catalyst, solvent and temperature was investigated in the model reaction of benzaldehyde, dimedone and phthalhydrazide under ultrasonic waves (Table 1). As shown in Table 2, no product was obtained where the reaction was carried out under solvent-free conditions at room temperature in the presence of 1 mol% of catalyst (Table 1, entry 1). Where ethanol and toluene were used as solvent, a low yield was obtained under above mentioned conditions (Table 1, entries 2, 3). Interestingly in water, as green and environmentally friendly solvent, the best result was observed under these conditions (Table 1, 15

entry 4). With increasing temperature from room temperature to 50 °C, the reaction time reduced and the yield significantly increased (Table 1, entry 6). The study of effect of catalyst loading demonstrated that the best result is delivered in the presence of 0.7 mol % of desired catalyst (Table 1, entries 6-8). Accordingly, the use of 0.7 mol % of catalyst at 50 °C in water were selected as optimum conditions under ultrasonic irradiations. To study the neat effect of manganese species in the catalytic process, in the next the catalytic ability of Mn-free Fe3O4@OS and Fe3O4@OS/IL materials were investigated on the model reaction (Table 1, entries 9, 10). Interestingly, the Fe3O4@OS gave only 8% of desired product, while the Fe3O4@OS/IL furnished 17% of the corresponding product under the same conditions and time as Fe3O4@OS/IL-Mn. These confirm that the main catalytic process is performed through supported manganese species.

Table 1. The effect of solvent, catalyst loading and temperature in the synthesis of 2-Hindazolo[2,1-b]phthalazines using Fe3O4@OS/IL-Mn nanocatalysta

Entry

Solvent

Catalyst (mol%)

Temperature

Time

Yield (%)

1

-

1

25 °C

2h

N.R.

2

EtOH

1

25 °C

2h

25

3

Toluene

1

25 °C

2h

22

16

4

H2O

1

25 °C

2h

40

5

H2O

1.4

25 °C

2h

62

6

H2O

0.5

50 °C

20 min

77

7

H2O

0.7

50 °C

20 min

95

8

H2O

1

50 °C

20 min

95

9

H2O

Fe3O4@OS/ IL(0.016 g)

50 °C

20 min

17

10

H2O

Fe3O4@OS 50 °C 20 min 8 (0.016 g) a Reaction conditions: Benzaldehyde (1 mmol), phthalhydrazide (1 mmol), dimedone (1.5 mmol), ultrasonic irradiations.

With these conditions in hand, the substrate scope of this catalytic system was studied (Table 2). As

shown

benzaldehyde,

electron

donating-containing

aldehydes

(such

as

4-

methoxybenzaldehyde and 4-methylbenzaldehyde) and electron withdrawing-containing aldehydes (such as 3-nitrobenzaldehyde, 4-bromobenzaldehyde, 4-cyanobenzaldehyde, 2nitrobenzenealdehyde

and

2-chlorobenzaldehyde)

were

reacted

with

dimedone

and

phthalhydrazide delivering corresponding 2-H-indazolo[2,1-b]phthalazintriones in high to excellent yield. This shows the high efficiency of designed catalyst for the preparation of a wide range of biologically active 2-H-indazolo[2,1-b]phthalazintriones.

17

Table 2. Preparation of 2-H-indazolo[2,1-b]phthalazintriones in the presence of Fe3O4@OS/IL-Mn catalyst a Entry

Aldehyde

Time(min) Yield (%)

M. P.(Found)

M. P. [Reported]

1

C6H5 CHO

20

95

206-208

205-207[48]

2

p-CH3O C6H4CHO

8

97

228-230

220-222[49]

3

p-Me C6H4CHO

20

89

221-223

218-220[68]

4

m-NO2 C6H4CHO

12

90

265-267

267-269[68]

5

p-Br C6H4CHO

12

90

264-266

263-265[48]

6

p-CN C6H4CHO

10

87

225-227

226-228[48]

7

o-NO2 C6H4CHO

15

85

248-250

251-253[48]

8

o-Cl 20 79 257-260 260-262[68] C6H4CHO a Conditions: Aldehyde (1 mmol), dimedone (1.5 mmol), phthalhydrazide (1 mmol) catalyst (0.7 mol%), H2O, t= 50 °C under ultrasonic irradiations. In another study, the catalytic efficiency of the Fe3O4@OS/IL-Mn was compared with several recently catalysts applied in the synthesis of 2-H-indazolo[2,1-b]phthalazintriones . The model reaction of benzaldehyde, phthalhydrazide and dimedone was considered as a representative example (Table 3). The results showed that the present catalytic method is superior to some of the earlier methods in terms of reaction conditions, recycling times and yields. As shown, the present work is performed in the presence of 0.7 mol% of designed catalyst at relatively short

18

time in water under moderate temperature. While, the most of previous methods have been performed at high temperature in long reaction time. Moreover, the recycling times of our catalyst is much better than previous works. These results demonstrate the excellent efficiency, durability and stability of the Fe3O4@OS/IL-Mn nanocatalyst during applied conditions.

Table 3: Comparison of the catalytic activity of Fe3O4@OS/IL-Mn with several reported catalysts

Entry

Catalyst

Conditions

Recycling times

Yield (%)

Ref.

1

ASA

Solvent free, cat (0.025 g), 110 °C, 14 min

-

85

[48]

2

SBA-pr-SO3H

Solvent free, cat (0.02 g), 80 °C, 5 min

-

90

[69]

3

Al-SBA-15TPI/H6P2W18O62

Solvent free, cat. (0.0 2g), 100 °C, 5 min

8

82

[70]

4

Silica-SO3H

Solvent free, cat. (0.025g), 100 °C, 8 min

5

87

[50]

5

Fe3O4@SiO2

Solvent free, cat (8 mol%), 120 °C, 12 min

5

96

[53]

19

6

Fe3O4@silica sulfuric acid

Solvent free, cat. (0.075g), 100 °C, 35 min

6

88

[57]

7

Fe3O4@OS/IL-Mn

H2O, cat. (0.7 mol%), 50 °C, 20 min

11

95

This work

ASA: Alumina sulforic acid, TPI: N-[3-(triethoxysilyl)propyl]isonicotinamide

In the next, the recoverability and reusability of the designed Fe3O4@OS/IL-Mn nanocatalyst were studied in the model reaction of p-MeO-benzaldehyde with phthalhydrazide and dimedone under ultrasonic conditions. To do this, the catalyst was added into a reaction vessel containing starting materials at 50 °C in an ultrasonic bath and the reaction progress was monitored by TLC. After completion of the reaction, the catalyst was magnetically separated, recovered and reused in the next run under the same conditions as the first run. These steps were repeated several times and the corresponding yields were calculated. The result showed that the catalyst could be recovered and reused at least 11 times with keeping its efficiency and stability (Figure 8).

20

Figure 8. The recoverability and reusability of the Fe3O4@OS/IL-Mn nanocatalyst

In the next study, a leaching experiment was performed on the reaction of benzaldehyde with dimedone and phtalhydrazide as a test model. To this end, after about 50 % of the reaction was completed, the catalyst was magnetically separated and removed. Then, the catalyst-free solution was allowed to continue under optimized conditions. After 1 h, only a trace conversion was found for the latter reaction. The atomic absorption spectroscopy also showed no-leaching of Mn-species in the reaction solution during process. These are in good agreement with the recovery test and confirm the catalyst is highly stable and operates in a heterogeneous manner. The high stability of the present catalytic system is attributed to supported ionic liquid groups that powerfully immobilize and stabilize the active manganese species against any leaching, agglomeration and deactivation.

21

4. Conclusion In summary, in this study a novel magnetic organosilica supported Mn-catalyst (Fe3O4@OS/ILMn) was prepared, characterized and applied in the synthesis of biologically useful 2Hindazolo[2,1-b]phthalazintrions. The FTIR, EDX and TGA analyses showed well incorporation and high stability of expected groups and elements into/onto catalyst framework. The SEM and TEM analyses showed that the synthesized nanoparticles have a uniform spherical shape. The wide angle PXRD and VSM analyses confirmed the presence of magnetic particles with high stability for the catalyst. This new nanocatalyst was successfully used in the one-pot preparation of 2-H-indazolo[2,1-b]phthalazintrions under ultrasonic conditions and gave products in high to excellent yields at short times. Some other advantages of this catalytic system are simple workup of reaction products, low loading of catalyst, easy catalyst recovery, low-temperature, the use of water as green solvent as well as high stability and durability of the catalyst under applied conditions. According to these benefits, some applications of this catalyst in other organic transformation are underway in our laboratory.

Acknowledgements The authors thank the Yasouj University and the Iran National Science Foundation (INSF) for supporting this work.

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Highlights 1. A novel magnetic ethyl-based organosilica supported ionic liquid/manganese complex (Fe3O4@OS@IL/Mn) was prepared 2. The Fe3O4@OS@IL/Mn was characterized using VSM, TGA, FTIR, SEM, PXRD and EDX analyses 3. The Fe3O4@OS@IL/Mn was applied as powerful nanocatalyst in the synthesis of 2Hindazolo-[2,1-b]-phthalazin-trions 4. The 2H-indazolo-[2,1-b]-phthalazin-trions were obtained in high to excellent yields under green conditions 5. The designed nanocatalyst was recovered and reused several times with keeping its efficiency

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: