Sonochemically synthesized ferromagnetic Fe3O4 nanoparticles as a recyclable catalyst for the preparation of pyrrolo[3,4-c]quinoline-1,3-dione derivatives

Article abstract of DOI:10.1039/c4ra11623b

This paper reports the green, rapid synthesis of Fe₃O₄ nanoparticles by the ultrasonic irradiation of Fe₂O₃ solution and Perilla frutescens (P. frutescens) leaf extract, which was used as both reducing and capping agent. The synthesized Fe₃O₄ nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis, vibrating sample magnetometry, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The FT-IR spectra indicated that the bioactive molecules present in the plant extract contain polyols, which act as a reducing as well as capping agent, as confirmed by TGA. TEM and SEM showed that the Fe₃O₄ nanoparticles were approximately spherical in shape with a mean size of 50 nm. The synthesized Fe₃O₄ nanoparticles exhibited ferromagnetic behavior with a saturation magnetization of 25.15 emu g^-1. The Fe₃O₄ nanoparticles, with their easy recovery by an external magnetic field, exhibited strong catalytic activity towards pyrrolo[3,4-c]quinoline-1,3-dione derivatives. These results suggest that the Fe₃O₄ nanoparticles produced can be applied as a catalyst in organic synthesis and recycled at least five times without significant loss in its activity.

Full text of DOI:10.1039/c4ra11623b

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PAPER
Sonochemically synthesized ferromagnetic Fe3O4
nanoparticles as a recyclable catalyst for the
preparation of pyrrolo[3,4-c]quinoline-1,3-dione
derivatives
Cite this: RSC Adv., 2014, 4, 61660
*
Nagaraj Basavegowda, Kanchan Mishra and Yong Rok Lee
This paper reports the green, rapid synthesis of Fe3O4 nanoparticles by the ultrasonic irradiation of Fe2O3
solution and Perilla frutescens (P. frutescens) leaf extract, which was used as both reducing and capping
agent. The synthesized Fe3O4 nanoparticles were characterized by Fourier transform infrared
spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron
microscopy (SEM), energy dispersive X-ray analysis, vibrating sample magnetometry, thermogravimetric
analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The FT-IR spectra indicated that the
bioactive molecules present in the plant extract contain polyols, which act as a reducing as well as
capping agent, as confirmed by TGA. TEM and SEM showed that the Fe3O4 nanoparticles were
approximately spherical in shape with a mean size of 50 nm. The synthesized Fe3O4 nanoparticles
exhibited ferromagnetic behavior with a saturation magnetization of 25.15 emu gꢀ1
. The Fe3O4
Received 1st October 2014
Accepted 10th November 2014
nanoparticles, with their easy recovery by an external magnetic field, exhibited strong catalytic activity
towards pyrrolo[3,4-c]quinoline-1,3-dione derivatives. These results suggest that the Fe3O4 nanoparticles
produced can be applied as a catalyst in organic synthesis and recycled at least five times without
significant loss in its activity.
DOI: 10.1039/c4ra11623b
www.rsc.org/advances
be expensive and time-consuming. To simplify the synthetic
method, an alternative sonochemical technique has been used
1. Introduction
for fabricating magnetite nanoparticles because of its low cost,
high magnetization and crystallinity.16 Sonochemistry arises
from an acoustic cavitation phenomenon, which is the forma-
tion, growth and collapse of bubbles in a liquid medium.17
Fe3O4 nanoparticles, with a mean size of 50 nm, were synthe-
sized in an aqueous solution of P. frutescens leaf extract under
ultrasonic irradiation.18
Pyrrolo[3,4-c]quinoline-1,3-diones show a broad spectrum of
biologically and pharmacologically important properties, such
as inhibitory activities against caspase-3,19 HCV polymerase,20
highly selective agonists, antagonists or inverse agonist for
GABAs brain receptor,21 and antitumor.22 Because of their
importances and usefulnesses, several synthetic methods
through many step reactions for pyrrolo[3,4-c]quinoline-1,3-
diones have been reported.23 These reported approaches are
limited by their complexity, the long reaction time and harsh
reaction conditions required, and their low yields. Recently, we
have developed one-pot synthetic method for pyrrolo[3,4-c]-
quinoline-1,3-dione derivatives using ethylenediamine diac-
etate as an organocatalyst.24 Although several methods of
synthesizing pyrrolo[3,4-c]quinoline-1,3-dione derivatives have
been reported,23,24 there remains a need for novel and improved
synthetic routes requiring readily available, inexpensive,
Green nanotechnology is one of the most important research
and development topics in the modern era. Magnetite (Fe3O4)
nanoparticles with the size range of 30–50 nm are scientically
and technologically relevant in elds such as catalysis,1
magnetic uids,2 magnetic resonance imaging,3 hyperthermia
in cancer treatment,4 targeted drug delivery,5 etc. Because of
their low cost, low toxicity and stability, Fe3O4 nanoparticles are
being used in biomedical areas, such as magnetic cell separa-
tion, magnetic embolizing blood vessels, carriers of chemicals
or drugs6–9 etc. Among the magnetic materials, magnetite has
shown the best magnetic properties compared to other
magnetic iron oxides.10 Fe3O4-NPs have many unique magnetic
properties, such as superparamagnetic, low Curie temperature,
high magnetic susceptibility, and high coercivity, which meet
the demands of practical use, but the broad size distribution
limits the applications of magnetite particles. A number of
approaches have been developed to produce Fe3O4 nano-
particles, such as micro-emulsion,11 co-precipitation,12 pyrol-
ysis,13 electrochemical synthesis,14 and hydrothermal
synthesis.15 On the other hand, most of these techniques tend to
School of Chemical Engineering, Yeungnam University, Gyeongsan 712-749, Republic
of Korea. E-mail: yrlee@yu.ac.kr; Fax: +82-53-810-4631; Tel: +82-53-810-2529
61660 | RSC Adv., 2014, 4, 61660–61666
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recyclable catalysts, and environmentally benignity. To the best thermogravimetric analysis (TGA, TG-DTA, SDT-Q600 V20.5
of our knowledge, reactions using recyclable catalysts to Build 15).
synthesize pyrrolo[3,4-c]quinoline-1,3-dione derivatives has not
been reported so far.
2.5 Catalytic activity of Fe3O4 nanoparticles
We reports herein the rapid and easy sonochemical green
synthesis of Fe3O4 nanoparticles using the P. frutescens leaf
extract, which acts as both a reducing and capping agent as well
as its application as a recyclable catalyst for the preparation of a
variety of pyrrolo[3,4-c]quinoline-1,3-dione derivatives in high
yield.
The synthesized Fe3O4 nanoparticles were used as a catalyst for
the synthesis of pyrrolo[3,4-c]quinoline-1,3-dione derivatives by
reactions of isatins with b-ketoamides.
2.6 General procedure for the synthesis of compounds 3a–3j
To a mixture of isatin (1.0 mmol, 147.3 mg) and acetoacetani-
lide (1.1 mmol, 194.7 mg) in toluene (8 mL) was added Fe3O4
nanoparticles (5.0 mol%, 11.6 mg) at room temperature. The
reaction mixture was heated under reux for 6–8 h. The prog-
ress of the reaction was monitored by TLC. Aer completion of
reaction, the solvent was removed using a reduced pressure
evaporator. The residue was puried by column chromatog-
raphy on a silica gel to give the product.
2. Experimental section
2.1 Chemicals
Iron(III) oxide, isatins and b-ketoamide derivatives were
purchased from Sigma-Aldrich. The air dried leaves of P. fru-
tescens were obtained at a local market in Yeongchon, South
Korea.
2.7 Characterization data
2.2 Preparation of P. frutescens leaf extract
4-Methyl-2-phenyl-1H-pyrrolo[3,4-c]quinoline-1,3(2H)-dione
(3a).24 Brown solid; yield: 89%; mp 163–164 C; H NMR (300
1
ꢁ
Dried P. frutescens leaves were crushed to make a ne powder,
and 6 g of it was placed in 300 mL of deionized Milli-Q water.
The broth solution was then boiled for 10 min and ltered
MHz, CDCl3) d 8.83 (dd, J ¼ 8.1, 0.6 Hz, 1H), 8.15 (d, J ¼ 8.4 Hz,
1H), 7.89 (td, J ¼ 8.7, 1.5 Hz, 1H), 7.71 (td, J ¼ 8.1, 0.9 Hz, 1H),
7.55–7.52 (m, 2H), 7.47–7.41 (m, 3H), 3.08 (s, 3H); 13C NMR (75
MHz, CDCl3) d 167.41, 167.20, 155.30, 151.60, 135.67, 132.90,
131.23, 129.26, 129.22, 129.14, 128.35, 126.66, 125.00, 121.56,
120.67, 22.21; IR (KBr): 3064, 2924, 1718, 1597, 1499, 1377, 1113,
871, 776, 691, 629, 577, 509, cmꢀ1; HRMS (EI+): m/z: calcd for
ꢁ
through a 0.2 mm lter and stored at 4 C for further use.
2.3 Biosynthesis of Fe3O4 nanoparticles using aqueous P.
frutescens leaf extract
5 mL of P. frutescens extract was added to 50 mL of a prepared
C
18H12N2O2: 288.0899, found: 288.0898.
2 mM of iron(III) oxide (Fe2O3) solutions and sonicated for 2 h at
4-Methyl-2-(o-tolyl)-1H-pyrrolo[3,4-c]quinoline-1,3(2H)-dione
ꢁ
60 C. The resulting nanoparticles were puried by centrifuga-
1
(3b).24 Brown solid; yield: 76%; mp 198–199 C; H NMR (300
MHz, CDCl3) d 8.77 (d, J ¼ 8.4 Hz, 1H), 8.10 (d, J ¼ 8.4 Hz, 1H),
7.86–7.81 (m, 1H), 7.66 (dd, J ¼ 8.4, 7.2 Hz, 1H), 7.34–7.25 (m,
3H), 7.17 (d, J ¼ 8.4 Hz, 1H), 3.03 (s, 3H), 2.17 (s, 3H); 13C NMR
(75 MHz, CDCl3) d 167.45, 167.20, 155.28, 151.54, 136.59, 135.94,
ꢁ
tion in a Beckman Coulter's Avanti J-E centrifuge (USA) at
10 000 rpm for 20 min.
2.4 Characterizations of Fe3O4 nanoparticles
Bioreductions of iron oxide salts was monitored using an 132.90, 131.22, 130.10, 129.63, 129.19, 129.10, 128.76, 126.95,
Optizen 3220 (Double beam) UV-Vis spectrophotometer. FT-IR 125.03, 121.85, 120.73, 22.18, 18.08; IR (KBr): 3063, 2926, 1718,
spectroscopy was performed to recognize the biomolecules 1626, 1497, 1377, 1115, 871, 769, 632, 583, 514 cmꢀ1; HRMS
present in P. frutescens extract that may be accountable for the (EI+): m/z: calcd for C19H14N2O2: 302.1055, found: 302.1051.
reductions of metals and even for the stabilization of nano-
2-(4-Methoxyphenyl)-4-methyl-1H-pyrrolo[3,4-c]quinoline-1,3-
1
particles. The surface morphology and microstructures of the (2H)-dione (3c).24 Brown solid; yield: 88%; mp 231–232 ꢁC; H
Fe3O4 nanoparticles were examined by eld emission scanning NMR (300 MHz, CDCl3) d 8.81 (d, J ¼ 8.4 Hz, 1H), 8.15 (d, J ¼ 8.7
electron microscopy (FE-SEM coupled with an EDS detector, Hz, 1H), 7.87 (dd, J ¼ 8.1, 7.2 Hz, 1H), 7.70 (dd, J ¼ 7.8, 7.5 Hz,
Hitachi S4200, Japan). The size of the Fe3O4 nanoparticles was 1H), 7.34 (d, J ¼ 8.7 Hz, 2H), 7.02 (d, J ¼ 9.0 Hz, 2H), 3.84 (s, 3H),
characterized by transmission electron microscopy (TEM, FEI 3.07 (s, 3H); 13C NMR (75 MHz, CDCl3) d 167.61, 167.38, 159.39,
Tecnai G2 F20 ST FE-TEM). The chemical composition of the 155.20, 151.37, 135.76, 132.90, 129.10, 128.00, 124.99, 123.72,
Fe3O4 nanoparticles was analyzed by energy-dispersive X-ray 121.59, 120.65, 114.53, 55.50, 22.10; IR (KBr): 2986, 2840, 1711,
analysis (EDAX). The crystallinity of the Fe3O4 nanoparticles 1514, 1395, 1260, 1175, 1119, 1094, 1032, 739 cmꢀ1; HRMS (EI+):
was examined by X-ray diffraction (XRD, PANalytical X'Pert m/z: calcd for C19H14N2O3: 318.1004, found: 318.1003.
MRD model). X-ray photoelectron spectroscopy (XPS) analysis
2-(2-Chlorophenyl)-4-methyl-1H-pyrrolo[3,4-c]quinoline-1,3-
1
was carried out using a K-Alpha system tted with an Al Ka X-ray (2H)-dione (3d).24 Brown solid; yield: 75%; mp 155–156 C; H
source. The ion source energy was 100 V to 3 keV for the survey. NMR (300 MHz, CDCl3) d 8.86 (d, J ¼ 8.1 Hz, 1H), 8.24 (d, J ¼ 8.4
The magnetic properties of Fe3O4 nanoparticles were measured Hz, 1H), 7.93 (d, J ¼ 7.2, 6.9 Hz, 1H), 7.76 (d, J ¼ 7.8, 7.5 Hz, 1H),
by vibrating sample magnetometry (VSM, Lake Shore Cryo- 7.61–7.58 (m, 1H), 7.49–7.44 (m, 2H), 7.40–7.34 (m, 1H), 3.13 (s,
tronics, Inc., Idea-VSM, model 662 with 735 VSM controller). 3H); 13C NMR (150 MHz, CDCl3) d 166.75, 166.54, 155.42,
The % weight loss of Fe3O4 nanoparticles were determined by 151.67, 135.94, 133.33, 133.03, 130.90, 130.76, 130.51, 129.28,
ꢁ
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129.23, 129.21, 127.82, 125.11, 121.86, 120.78, 22.23; IR (KBr): (300 MHz, CDCl3) d 8.80 (d, J ¼ 2.1 Hz, 1H), 8.07 (d, J ¼ 9.3 Hz, 1H),
3071, 2924, 1715, 1594, 1540, 1374, 1059, 1033, 763, 592, 538 7.80 (dd, J ¼ 9.0, 2.1 Hz, 1H), 7.55–7.50 (m, 2H), 7.45–7.42 (m, 3H),
cmꢀ1; HRMS (EI+): m/z: calcd for C18H11ClN2O2: 322.0509, 3.06 (s, 3H); 13C NMR (75 MHz, CDCl3) d 167.01, 166.70, 155.57,
found: 322.0511.
149.84, 135.51, 134.74, 133.86, 131.04, 130.69, 129.25, 128.45,
2-(4-Chlorophenyl)-4-methyl-1H-pyrrolo[3,4-c]quinoline-1,3- 126.55, 123.71, 122.20, 121.05, 22.14; IR (KBr): 3062, 2924, 1723,
1
(2H)-dione (3e).24 Brown solid; yield: 77%; mp 224–225 C; H 1596, 1499, 1383, 1134, 1103, 830, 747, 683, 624, 581 cmꢀ1; HRMS
ꢁ
NMR (300 MHz, CDCl3) d 8.81 (d, J ¼ 7.8 Hz, 1H), 8.14 (d, J ¼ 8.7 (EI+): m/z: calcd for C18H11ClN2O2: 322.0509, found: 322.0508.
Hz, 1H), 7.89 (dd, J ¼ 8.4, 6.9 Hz, 1H), 7.71 (dd, J ¼ 8.1, 7.2 Hz,
8-Chloro-4-methyl-2-(o-tolyl)-1H-pyrrolo[3,4-c]quinoline-
1H), 7.49 (d, J ¼ 8.7 Hz, 2H), 7.42 (d, J ¼ 8.7 Hz, 2H), 3.07 (s, 1,3(2H)-dione (3k).24 Brown solid; yield: 84%; mp 197–198 C;
3H); 13C NMR (75 MHz, CDCl3) d 167.12, 166.92, 155.28, 151.67, 1H NMR (300 MHz, CDCl3) d 8.72 (d, J ¼ 2.1 Hz, 1H), 8.01 (d, J ¼
135.52, 134.08, 133.02, 129.75, 129.42, 129.09, 127.74, 124.93, 9.3 Hz, 1H), 7.73 (dd, J ¼ 9.0, 2.1 Hz, 1H), 7.33–7.24 (m, 3H), 7.15
121.40, 120.58, 116.34, 22.25; IR (KBr): 3064, 2925, 2855, 1722, (d, J ¼ 7.5 Hz, 1H), 3.00 (s, 3H), 2.16 (s, 3H); 13C NMR (75 MHz,
ꢁ
1625, 1495, 1387, 1117, 1089, 806, 771, 637, 588, 502 cmꢀ1
;
CDCl3) d 167.08, 166.70, 155.55, 149.83, 136.50, 135.41, 134.95,
HRMS (EI+): m/z: calcd for C18H11ClN2O2: 322.0509, found: 133.79, 131.24, 130.66, 129.91, 129.69, 128.67, 126.97, 123.71,
322.0507.
122.47, 121.08, 22.13, 18.06; IR (KBr): 3077, 3022, 2970, 1715,
4,8-Dimethyl-2-phenyl-1H-pyrrolo[3,4-c]quinoline-1,3(2H)- 1593, 1496, 1374, 1124, 839, 754, 695, 631, 582 cmꢀ1; HRMS
dione (3f).24 Brown solid; yield: 78%; mp 194–195 C; H NMR (EI+): m/z: calcd for C19H13ClN2O2: 336.0666, found: 336.0664.
1
ꢁ
(300 MHz, CDCl3) d 8.58 (s, 1H), 8.02 (d, J ¼ 8.7 Hz, 1H), 7.70
8-Chloro-2-(4-methoxyphenyl)-4-methyl-1H-pyrrolo[3,4-c]-
(dd, J ¼ 8.7, 1.8 Hz, 1H), 7.55–7.50 (m, 2H), 7.47–7.39 (m, 3H), quinoline-1,3(2H)-dione (3l).24 Brown solid; yield: 89%; mp 213–
3.04 (s, 3H), 2.58 (s, 3H); 13C NMR (150 MHz, CDCl3) d 167.49, 214 ꢁC; 1H NMR (300 MHz, CDCl3) d 8.79 (d, J ¼ 2.1 Hz, 1H), 8.07
167.34, 154.17, 150.37, 139.74, 135.32, 134.73, 131.31, 129.17, (d, J ¼ 9.0 Hz, 1H), 7.80 (dd, J ¼ 9.3, 2.14 Hz, 1H), 7.33 (d, J ¼ 9.0
128.84, 128.25, 126.62, 123.54, 121.44, 120.75, 22.03, 21.88; IR Hz, 2H), 7.02 (d, J ¼ 9.0 Hz, 2H), 3.85 (s, 3H), 3.05 (s, 3H); 13C
(KBr): 3061, 2960, 2922, 1719, 1600, 1498, 1375, 1103, 825, 754, NMR (75 MHz, CDCl3) d 167.29, 166.96, 159.47, 155.52, 149.76,
686, 624, 580 cmꢀ1; HRMS (EI+): m/z: calcd for C19H14N2O2: 135.48, 134.85, 133.84, 130.63, 127.94, 123.73, 123.56, 122.26,
302.1055, found: 302.1057.
121.08, 114.56, 55.52, 22.09; IR (KBr): 2968, 2841, 1712, 1517,
4,8-Dimethyl-2-(o-tolyl)-1H-pyrrolo[3,4-c]quinoline-1,3(2H)- 1397, 1254, 1144, 1093, 1036, 820, 518 cmꢀ1; HRMS (EI+): m/z:
1
dione (3g).24 Brown solid; yield: 76%; mp 213–214 C; H NMR calcd for C19H13ClN2O3: 352.0615, found: 352.0612.
ꢁ
(300 MHz, CDCl3) d 8.51 (s, 1H), 7.97 (d, J ¼ 8.7 Hz, 1H), 7.65
8-Chloro-2-(4-chlorophenyl)-4-methyl-1H-pyrrolo[3,4-c]quin-
(dd, J ¼ 8.7, 1.5 Hz, 1H), 7.31–7.26 (m, 3H), 7.16 (d, J ¼ 7.8 Hz, oline-1,3(2H)-dione (3m).24 Brown solid; yield: 75%; mp 241–
1H), 2.99 (s, 3H), 2.51 (s, 3H), 2.16 (s, 3H); 13C NMR (75 MHz, 242 ꢁC; 1H NMR (300 MHz, CDCl3) d 8.75 (d, J ¼ 2.1 Hz, 1H), 8.05
CDCl3) d 167.56, 167.35, 154.14, 150.32, 139.67, 136.57, 135.30, (d, J ¼ 9.0 Hz, 1H), 7.79 (dd, J ¼ 9.0, 2.1 Hz, 1H), 7.49 (d, J ¼ 8.7
134.99, 131.17, 130.17, 129.54, 128.76, 126.90, 123.54, 121.74, Hz, 2H), 7.40 (d, J ¼ 8.7 Hz, 2H), 3.04 (s, 3H); 13C NMR (75 MHz,
120.80, 22.00, 21.84, 18.06; IR (KBr): 3051, 2923, 1714, 1603, CDCl3) d 166.74, 166.45, 155.56, 149.95, 135.61, 134.54, 134.18,
1497, 1377, 1102, 834, 750, 631, 589 cmꢀ1; HRMS (EI+): m/z: 133.95, 130.79, 129.54, 129.45, 127.64, 123.62, 122.02, 120.93,
calcd for C20H16N2O2: 316.1212, found: 316.1209.
22.20; IR (KBr): 3085, 2926, 2856, 1721, 1593, 1497, 1394, 1264,
2-(4-Methoxyphenyl)-4,8-dimethyl-1H-pyrrolo[3,4-c] quino- 1237, 1129, 1091, 887, 810, 777, 748, 703, 647, 590, 559, 503
line-1,3(2H)-dione (3h).24 Brown solid; yield: 88%; mp 194– cmꢀ1; HRMS (EI+): m/z: calcd for C18H10Cl2N2O2: 356.0119,
195 ꢁC; 1H NMR (300 MHz, CDCl3) d 8.54 (s, 1H), 7.99 (d, J ¼ 8.7 found: 356.0118.
Hz, 1H), 7.68 (dd, J ¼ 8.7, 1.8 Hz, 1H), 7.34 (d, J ¼ 9.0 Hz, 2H),
7.02 (d, J ¼ 9.0 Hz, 2H), 3.84 (s, 3H), 3.01 (s, 3H), 2.56 (s, 3H); 13
C
NMR (75 MHz, CDCl3) d 167.76, 167.57, 159.31, 154.09, 150.30,
139.65, 135.24, 134.74, 128.79, 127.98, 123.86, 123.51, 121.45,
120.71, 114.49, 55.50, 22.00, 21.86; IR (KBr): 2925, 2842, 1715,
3. Results and discussion
3.1 UV-Vis study of Fe3O4 nanoparticles
1514, 1394, 1249, 1174, 1126, 1032, 821, 560 cmꢀ1; HRMS (EI+): Aer sonication for 2 h at 60 ꢁC, the color of the reaction
m/z: calcd for C20H16N2O3: 332.1161, found: 332.1162.
mixture of iron oxide salt and leaf extract changed from light
2-(4-Chlorophenyl)-4,8-dimethyl-1H-pyrrolo[3,4-c]quinoline- red to dark brown indicating the formation of Fe3O4 nano-
1,3(2H)-dione (3i).24 Brown solid; yield: 74%; mp 235–236 ꢁC; 1H particles. The avonoid and phenolic compounds present in the
NMR (300 MHz, CDCl3) d 8.52 (s, 1H), 7.99 (d, J ¼ 9.0 Hz, 1H), P. frutescens leaf extract may act as capping and reducing agents
7.69 (dd, J ¼ 8.7, 1.8 Hz, 1H), 7.48 (d, J ¼ 8.7 Hz, 2H), 7.41 (d, J ¼ that reduce Fe3+ to Fe2+.25
9.0 Hz, 2H), 3.01 (s, 3H), 2.56 (s, 3H); 13C NMR (75 MHz, CDCl3)
The UV-Vis spectroscopy of Fe2O3 before reduction was
d 167.15, 167.02, 154.11, 150.39, 139.86, 135.41, 134.47, 133.93, shown in Fig. 1 to conrm the formation of Fe3O4 nano-
129.78, 129.35, 128.87, 127.67, 123.40, 121.21, 120.59, 22.05, particles. Aside from Fe2O3, the synthesized Fe3O4 nano-
21.88; IR (KBr): 2967, 2925, 1721, 1607, 1497, 1384, 1277, 1191, particles showed continuous absorption in the visible range
1121, 1091, 1019, 817, 748, 597, 535, 506 cmꢀ1; HRMS (EI+): m/z: between 200 to 600 nm. Njagi et al.26 and Nadagouda et al.27
calcd for C19H13ClN2O2: 336.0666, found: 336.0664.
reported similar UV-Vis spectra for iron nanoparticles synthe-
8-Chloro-4-methyl-2-phenyl-1H-pyrrolo[3,4-c]quinoline-1,3(2H)- sized using an aqueous Sorghum bran extract and tea poly-
1
dione (3j).24 Brown solid; yield: 87%; mp 181–182 ꢁC; H NMR phenols, respectively.
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Fig. 3 TEM image of Fe3O4 nanoparticles at different magnifications:
scale bar at (a) 100 nm, and (b) 20 nm.
Fig. 1 UV-Vis spectra and inset diagram of (a) Fe2O3 solution (b) Fe3O4
nanoparticles synthesized using P. frutescens leaf extracts.
3.2 SEM, TEM and EDAX analyses of the Fe3O4-NPs
SEM (Fig. 2a) showed that the as-synthesized Fe3O4 nano-
particles were spherical and highly uniform in size. The nano-
particles were capped with the bioactive molecules present in
the leaf extract, indicating the stabilization of nanoparticles.
Energy dispersive X-ray analysis (EDAX) (Fig. 2b) revealed a
signal at around 0.8, 6.3, and 6.8 keV, which were assigned to
the binding energies of the iron and conrmed the formation of
Fe3O4 nanoparticles.
Fig. 4 XRD patterns of Fe3O4 nanoparticles.
TEM (Fig. 3a) showed that Fe3O4 nanoparticles were
approximately spherical with a mean size of 50 nm and Fig. 3b
showed nanoparticles at high magnications.
3.4 X-ray photoelectron spectroscopy (XPS)
The binding energies of the elements of Fe3O4 nanoparticles
are shown in the XPS spectrum (Fig. 5a). The XPS spectrum
reveals that the nanoparticles are composed of different
elements like carbon, oxygen, iron, and nitrogen. The XPS
spectrum of synthesized nanoparticles was similar to that of
nanoparticles produced using H. vulgare and Rumex acetose
extract.31 The photoelectron peaks at 711.4 eV and 724.8 eV
(Fig. 5b) were attributed to Fe2p3/2 and Fe2p1/2 respectively,
which further conrmed the presence of di- and trivalent iron
atoms in the Fe3O4 nanoparticles. The survey scan spectra
also conrmed O1s peak at 533.5 eV corresponding to oxide
oxygen.
3.3 Powder X-ray diffraction of the Fe3O4 nanoparticles
XRD (Fig. 4) of the synthesized Fe3O4 nanoparticles indicated
that the magnetite nanoparticles were crystalline in nature. The
diffraction peaks were observed at 29.99ꢁ, 35.32ꢁ, 42.93ꢁ, 56.76ꢁ,
and 62.33ꢁ 2q, which were assigned to the (2 2 0), (3 1 1), (4 0 0),
(5 1 1), and (4 4 0) Bragg's reections of face-centered iron oxide,
respectively, and were consistent with JCPDS no. 19-0629.28 The
extra unassigned peaks (*) observed were due to the crystalli-
zation of other bioorganic compounds on the surfaces of the
Fe3O4 nanoparticles, which concur with previous reports using
the Tridax procumbens leaf extract29 and similarly in silver and
gold nanoparticles synthesis using a Murraya Koenigii leaf
extract.30
3.5 FT-IR analysis of Fe3O4 nanoparticles
The FT-IR spectrum of synthesized magnetite nanoparticles
(Fig. 6) revealed a band in the region of 800 and 400 cmꢀ1
,
which may be due the stretching vibration of Fe–O bonds in
Fe3O4.32 The peak at 1625 cmꢀ1 may probably due to C]C
bond of capping organic molecules in magnetite nano-
particles. The peak at 3448 cmꢀ1 may indicate OH group,
while the peak at 1112 cmꢀ1 may exhibit C–O bond.33 FT-IR
spectrum of Fe2O3 is also given for comparison (Fig. 6). The
strong bands at 472 and 560 cmꢀ1 were assigned to the
specic vibrations of Fe–O bonds.34 The intensity of these
bands is very weak in synthesized Fe3O4 nanoparticles
compared to plain Fe2O3.35 Overall, the FT-IR spectra of
synthesized magnetite nanoparticles showed that the
Fig. 2 SEM image of Fe3O4 nanoparticles at (a) 3.0 mm, (b) EDAX result
showing the formation of Fe3O4 nanoparticles.
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Fig. 7 Magnetization curve of the synthesized Fe3O4 nanoparticles at
300 K.
3.7 Thermogravimetric analysis (TGA)
TGA traces of Fe3O4 nanoparticles revealed two signicant
weight loss steps from room temperature to 1000 ꢁC (Fig. 8). The
weight loss was 14.73%, and 10.79% in the rst, and second
steps, respectively, giving an overall weight loss of 25.52%,
which conrmed the capping of bioactive molecules on the
Fe3O4 nanoparticles.37 The residual mass at 990.85 ꢁC was
74.48%.
Fig. 5 XPS spectra of Fe3O4 nanoparticles (a) full scan XPS spectrum of
iron-containing nanoparticles (b) XPS spectrum of iron 2p-electrons of
iron-containing nanoparticles.
3.8 Catalytic activity and recyclability of the Fe3O4
nanoparticles
To synthesize
a variety of pyrrolo[3,4-c]quinoline-1,3-dione
derivatives, reaction of isatin derivatives 1 with several b-ketoa-
mides derivatives 2 in the presence of synthesized Fe3O4 nano-
particles were examined. The results are summarized in Table 1.
The treatment of isatin (1a) with 3-oxo-N-phenylbutanamide (2a)
in the presence of 5.0 mol% of Fe3O4 nanoparticles in reuxing
toluene for 6 h gave 3a in 89% yield. Reactions of 1a with 3-oxo-N-
o-tolylbutanamide (2b) or 3-oxo-N-4-methoxyphenylbutanamide
(2c) bearing electron donating group on the benzene ring of 3-
oxo-N-aryllbutanamide for 6–8 h provided compounds 3b and 3c
in 76 and 88% yield, respectively, whereas those with 3-oxo-N-2-
Fig. 6 FT-IR spectra of Fe2O3 and Fe3O4 nanoparticles synthesized
from the P. frutescens leaf extract.
bioactive molecules containing O–H, C]C, C–O groups pre-
sented in the plant extract, which act as capping agents in the
synthesized magnetite nanoparticles.
3.6 Vibrating sample magnetometry (VSM)
The hysteresis loops of VSM analysis at 300 K (Fig. 7) showed
that the Fe3O4 nanoparticles are ferromagnetic in nature with a
saturation magnetization (Ms) of 25.15 emu gꢀ1. The coercivity
(Hc) at 5000 G and remanent magnetization (Mr) were 220 G and
4.06 emu gꢀ1, respectively. The VSM of Fe3O4 nanoparticles
showed similar results compared to other reports.36
Fig. 8 TGA of Fe3O4 nanoparticles.
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Table 1 Synthesis of various pyrrolo[3,4-c]quinoline-1,3-diones 3a–
3m using synthesized Fe3O4 nanoparticles as a catalysta
3j, 3k, 3l and 3m were produced in 87, 84, 89, and 75% yields,
respectively.
Furthermore, reaction of 1a with 2a using P. frutescens leaf
extract did not provide the desired product 3a, whereas that in
the presence of 5 mol% of Fe2O3 afforded a trace amount of
product 3a.
The magnetite nanoparticles were recovered easily using an
external magnetic eld due to the magnetic nature of the
catalyst. Aer washing with CH2Cl2 and dried in vacuum for 2 h,
the recovered catalyst was again used for other reaction under
the same conditions. The nanocatalyst was recycled ve times
for the synthesis of compound 3, as shown in Fig. 9. The
performance of Fe3O4 nanoparticles was affected slightly aer
the fourth cycle and showed that the recovered catalyst could be
reused successively in subsequent reactions without signicant
loss of the catalytic activity.
4. Conclusion
The medicinally important aqueous extract of P. frutescens was
found to act as a reducing and stabilizing agent for Fe3O4
nanoparticle production, which was assigned by TGA. UV-
visible spectroscopy indicated the formation of Fe3O4 nano-
particles. SEM showed that the Fe3O4 nanoparticles had roughly
spherical shapes with a mean particle size of 50 nm, which was
conrmed by TEM. FT-IR analysis showed that the biomole-
cules present in P. frutescens were accountable for the formation
of Fe3O4 nanoparticles. XRD conrmed their crystallinity. EDAX
and XPS conrmed elemental make-up and its oxidation states
respectively. The synthesized Fe3O4 nanoparticles exhibited
strong catalytic activity for the preparation of various pyrrolo
[3,4-c]quinoline-1,3-dione derivatives and could also be recov-
ered easily by an external magnetic eld. This synthetic method
for Fe3O4 nanoparticles was green, simple and eco-friendly
benign because it does not require any extra reductant or
a
Reaction conditions:
1 (1.0 mmol), 2 (1.1 mmol), and Fe3O4
nanoparticles (5.0 mol%) in reuxing toluene (8 mL).
chlorophenylbutanamide (2d) or with 3-oxo-N-4-chlor-
ophenylbutanamide (2e) bearing electron-withdrawing group on
the benzene ring afforded the desired products 3d and 3e in 75
and 77% yield, respectively. Reactions of 5-methylisatin (1b)
bearing electron donating group on isatin ring with 2a, 2b, 2c, or
2e provided compounds 3f, 3g, 3h and 3i in 78, 76, 88 and 74%
yields, respectively. Similarly, with 5-chloroisatin (1c) bearing
electron-withdrawing group on isatin ring, the desired products
surfactant and can be applied in
applications.
a variety of existing
Acknowledgements
This work was supported by Priority Research Centers Program
through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education (2014R1A6A1031189).
Notes and references
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