Microwave solid phase synthesis, characterization and antimicrobial activities of manganese(II) complex with 2-((furan-3-ylmethylimino)methyl)phenol

Article abstract of DOI:10.14233/ajchem.2015.17584

Mononuclear complex of manganese (1) has been designed and synthesized by 2-((furan-3-ylmethylimino)methyl)phenol (L) with MnCl₂·₄H₂O in microwave radiation. The complex was characterized by X-ray crystallography, confirmi

Full text of DOI:10.14233/ajchem.2015.17584

Asian Journal of Chemistry; Vol. 27, No. 5 (2015), 1735-1738
A
SIAN
J
OURNAL OF HEMISTRY
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http://dx.doi.org/10.14233/ajchem.2015.17584
Microwave Solid Phase Synthesis, Characterization and Antimicrobial Activities
of Manganese(II) Complex with 2-((Furan-3-ylmethylimino)methyl)phenol
*
SUO-PING XU , TING-TING CAO, SI-JIA WANG, WEI-QING MIAO, SHU-JIE WU and YA-NAN ZHU
Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University, Xuzhou 221116, P.R. China
*Corresponding author: Fax: +86 516 83500366; Tel: +86 516 83403165; E-mail: xsp62@jsnu.edu.cn
Received: 11 March 2014;
Accepted: 16 May 2014;
Published online: 20 February 2015;
AJC-16881
Mononuclear complex of manganese (1) has been designed and synthesized by 2-((furan-3-ylmethylimino)methyl)phenol (L) with
MnCl2·4H2O in microwave radiation. The complex was characterized by X-ray crystallography, confirming that the central mangances(II)
was coordinated by two oxygen atoms and two nitrogen atoms from two L. The complex was assayed for in vitro antibacterial (B. subtilis,
S. aureus, S. faecalis, P. aeruginosa, E. coli and E. cloacae ) activities and showed better antimicrobial activity against Gram positive
strains than Gram negative strains.
Keywords: Microwave solid phase synthesis, 2-((Furan-3-ylmethylimino)methyl)phenol ligand, Mononuclear mangancse(II) complex
Elemental analyses were performed on a CHN-O-Rapid
instrument and were within 0.4 % of the theoretical values.
Melting points were measured on a Boetius micro melting
point apparatus.
Synthesis of compound L and complex 1: Compound
L was designed and synthesized from salicylaldehyde and
furfurylamine in ethanol. The ligand and MnCl2·4H2O were
mixed together and microwave radiated 3 min in 250 W. The
green powder was dissolved in ethanol/DMF(1/1) and afforded
bis(2-((furan-3-ylmethylimino)methyl)phenol)-manganese(II)
(1) (Scheme-I).
INTRODUCTION
Salicylaldehyde type's Schiff base and the metal complexes
thereof show a wide spectrum of antimicrobial properties1-7.
Several researchers8-12 studied the synthesis, characterization
and structure-activity relationship (SAR) of Schiff bases.
Although these methods synthesize reliable routes for the
preparation of Schiff base type's complexes, most of them
follow lengthy procedures and time. Therefore, the develop-
ment of direct and efficient procedures for these classes of
compounds from materials has been the target of synthetic
organic chemistry. In this paper, one mononuclear complex
(1) was synthesized by 2-((furan-3-ylmethylimino)- methyl)-
phenol (L) with MnCl2·4H2O in microwave radiation assis-
tance. The complex were assayed for antibacterial activities
against three Gram positive bacterial strains (Bacillus subtilis,
Staphylococcus aureus and Streptococcus faecalis) and three
Gram negative bacterial strains (Escherichia coli, Pseudomonas
aeruginosa and Enterobacter cloacae ) by the 3-(4,5-dimethyl-
2-triazyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT)
method.
NH
O
O
2
O
N
+
OH
OH
L
O
O
N
O
1
N
MW 250W
3 min
Mn
O
+
MnCl2.4H2O
N
OH
EXPERIMENTAL
O
All chemicals were of reagent grade and used as received.
UV spectra were recorded on a U-3000 spectrophotometer.
IR spectra were recorded on a Nexus 870 FT-IR. 1H NMR spectra
were recorded on a Bruker DPX 300 model spectrometer
(Bruker Bioscience,USA) in CDCl3. ESI-MS spectra were
recorded on a Mariner System 5304 mass spectrometer.
Scheme-I: synthesis of L and 1
Synthesis of compound L: A mixture of salicylaldehyde
(20 mmol) and furfurylamine (20 mmol) in 30 mL ethanol
was refluxed for 2 h. After filtration, the yellow solid was
washed with athanol and water, dried and recrystallized from

1736 Xu et al.
Asian J. Chem.
TABLE-1
ethanol. Yield: 78 %, m.p.: 65-68 °C. UV (l nm): 370; 256.
Selected IR data (KBr, νmax, cm-1): 3143(m), 3010(m), 2904(s),
1624(s), 1537(s), 1471(s), 1426(m), 1400(s), 1337(s),
1200(m), 1150(s), 1128(m), 1010(s), 902(s), 812(m), 749(m);
1H-NMR (CDCl3) δ ppm: 11.45 (s,1H), 8.20 (s, 1H), 7.45 (d,
J = 6.8 Hz, 1H), 7.23 (d, J = 7.2 Hz, 1H), 7.12 (s, 2H), 6.85
(m, J = 16.6 Hz, 1H), 6.74 (d, J = 8.2 Hz, 1H), 6.12 (d, J =
12.0 Hz, 1H), 4.83 (s, 2H). ESI-MS: 202.10 (C12H12NO2+, [M
+ H]+). Anal. Calcd for C12H11NO2(%): C, 71.63; H, 5.51; N,
6.96. Found (%): C, 71.60; H, 5.54; N, 7.00.
Synthesis of complex 1: Compound L (10 mmol) and
MnCl2·4H2O (5 mmol) were mixed together and microwave
radiated 3 min in 250 W. The green powder was dissolved in
ethanol/DMF(1/1).After standing for 7 days, the single crystals
of complex 1 were obtained, were separated by filtration,
washed with ethanol thrice and dried.Yield: 70 %, m.p.: 249-
251 °C. UV (l nm): 375; 252. Selected IR data (KBr, νmax, cm-1):
3019(m), 2924(s), 1613(s), 1540(s), 1471(m), 1453(m), 1429(m),
1329(s), 1211(s), 1149(m), 1127(s), 1076(m), 1009(s), 971(m),
903(m), 818(m), 761(m), 751(m).Anal. Calcd for C24H20N2O4Mn
(%): C, 63.30; H, 4.43; N, 6.15. Found (%): C, 63.36; H, 4.40;
N, 6.17.
Crystal structure determinations and refinements: The
crystallographic date for 1 was collected on a Bruker Smart
1000 CCD area detector diffractometer equipped with MoKα
(λ = 0.71073 Å) radiation using ω-scan mode. Empirical
absorption correction was applied to the data. Unit cell dimen-
sions were obtained with least-squares refinements and all
structures were solved by direct methods with SHELXL-97.
All non-hydrogen atoms were located from the trial structure
and then refined anisotropically.All hydrogens were generated
in idealized positions. All calculations were performed with
SHELXL-97 programs13. Other relevant parameters of the
crystal structure are listed in Table-1.
CRYSTALLOGRAPHIC AND EXPERIMENTAL
DATA FOR COMPLEX 1
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
C24H20N2O4Mn
455.36
Monoclinic
C2/c
20.302(3)
5.7528(8)
17.357(2)
90
94.790(3)
90
2020.1(5)
4
296(2)
1.497
0.689
β (°)
γ (°)
V (Å3)
Z
T (K)
Density (g/cm3)
µ (mm-1)
F(000)
Data/restrains/parameters
θ range (°)
Reflections collected/unique
Rint
Final R indices [I >2σ(I)]
(∆ρ)max, (∆ρ)min (e/Å3)
940
2367/0/142
2.01 to 27.85
13014/2367
0.0247
R1 = 0.0512, wR2 = 0.1701
0.733 and -0.613
aR= ∑Fo–Fc/∑Fo, bwR = [∑[w(Fo2–Fc2)2]/∑[w(Fo2)2]]1/2
plates, 50 mL of PBS (phosphate buffered saline 0.01 mol/L,
pH 7.4: Na2HPO4·12H2O 2.9 g, KH2PO4 0.2 g, NaCl 8 g, KCl
0.2 g, distilled water 1000 mL) containing 2 mg/mL of MTT
was added to each well. Incubation was continued at room
temperature for 4-5 h. The content of each well was removed
and 100 mL of isopropanol containing 5 % 1 mol/L HCl was
added to extract the dye. After 12 h of incubation at room
temperature, the optical density (OD) was measured with a
microplate reader at 570 nm. The observed MICs were pre-
sented in Table-2.
Antimicrobial activity: The antibacterial activity of L
and 1 was tested against B. subtilis, S. aureus, S. faecalis, P.
aeruginosa, E. coli and E. cloacae using MTT medium. The
MICs of the test complexes were determined by a colourimetric
method using the dye MTT14. A stock solution of the synthe-
sized complex (50 µg/mL) in DMSO was prepared and graded
quantities of the test complexes were incorporated in specified
quantity of sterilized liquid medium. A specified quantity of
the medium containing the complex was poured into micro-
titration plates. Suspension of the microorganism was prepared
to contain approximately 105 cfu/mL and applied to micro-
titration plates with serially diluted complexes in DMSO to
be tested and incubated at 37 °C for 24 h for bacterial. After
the MICs were visually determined on each of the microtitration
RESULTS AND DISCUSSION
The Mn(II) complex having m.f. C24H20N2O4Mn was
prepared in moderate yield (70 %). IR spectra of compound L
show four bands at 3143 and 1624 cm-1, characteristic of the
mixed modes of vibrations arising from normal coordinates
having contributions from ν(OH) and ν(C=N)15. The infrared spectra
of complex 1 (KBr pellets) display an intense absorption band
at about 1613 cm-1 attributable to the ν(C=N) shifted ca. 11 cm-1
lower wave-number compared with 1624 cm-1 of L. The UV
spectra of the complex display an intense absorption peak at
*
*
252 nm (π→π ) and 375 nm (n → π ). The structure of complex
1 were confirmed by a single-crystal X-ray diffraction and is
shown in Figs. 1 and 2. The crystal structure consists of
TABLE-2
MICS (MINIMUM INHIBITORY CONCENTRATIONS) OF THE SYNTHETIC COMPOUNDS
Microorganisms MICs (µg/mL)
Compound
Gram positive
Gram negative
B. subtilis
3.125
12.5
S. aureus
S. faecalis
6.25
12.5
P. aeruginosa
E. coli
E. cloacae
12.5
6.25
25
12.5
25
6.25
12.5
1
L
25
Penicillin
Kanamycin
1.562
0.39
1.562
1.562
1.562
3.125
6.25
3.125
6.25
3.125
3.125
1.562

Vol. 27, No. 5 (2015)
Microwave Solid Phase Synthesis, Characterization and Antimicrobial Activities of Mn(II) Complex 1737
TABLE-3
SELECTED BOND LENGTHS (Å) AND BOND ANGLES (°) OF COMPLEX 1
Bond
Mn(1)-O(1)
Mn(1)-N(1)#1
O(1)-C(2)
Dist.
1.829(3)
1.920(2)
1.308(4)
(°)
Bond
Mn(1)-O(1)#1
N(1)-C(7)
O(2)-C(12)
Angle
Dist.
1.829(3)
1.288(4)
1.382(9)
(°)
Bond
Mn(1)-N(1)
N(1)-C(8)
Dist.
1.920(2)
1.498(4)
Angle
Angle
(°)
O(1)-Mn(1)-O(1)#1
O(1)-Mn(1)-N(1)#1
C(7)-N(1)-Mn(1)
180.000(1)
87.77(11)
124.8(2)
O(1)-Mn(1)-N(1)
O(1)#1-Mn(1)-N(1)#1
C(8)-N(1)-Mn(1)
92.23(11)
92.23(11)
120.3(2)
O(1)#1-Mn(1)-N(1)
N(1)-Mn(1)-N(1)#1
C(2)-O(1)-Mn(1)
87.77(11)
180.00(14)
129.5(2)
Symmetry transformations used to generate equivalent atoms: #1 -x + 1/2, -y + 1/2, -z + 2
mononuclear complex. The molecular structure of complex 1
crystallize in triclinic with space group C2/c; bond distances
and angles are provided in Table-3. The complex 1 is electro-
nically neutral mononuclear compound. The central metal
(Mn), on an inversion center, are in quadrilateral coordination
geometry with oxygen and nitrogen donors from two L. The
general Mn-O and Mn-N bond lengths are in the range 1.829(3)
Å and 1.920(2) Å, unexceptional and similar to the corres-
ponding bonds in other manganese Schiff base complexes16,17
.
As shown in Table-4, intermolecular H-bonds (C-H…O)
formed between adjacent molecules.
TABLE-4
HYDROGEN BONDS FOR COMPLEX 1 [(Å) AND (°)]
D-H...A
d(D-H)
0.97
d(H...A)
2.17
d(D...A)
2.6996
∠(DHA)
113
C(8)-H(8A)...O(1)
From MIC values, the complex was more toxic towards
Gram positive strains than Gram negative strains when compared
to the positive controls penicillin and kanamycin, respectively
(Table-2). The reason may be the difference in the structures
of the cell walls18. The walls of the Gram negative cells are
more complex than those of Gram positive cells. Lipopoly-
saccharides form an outer lipid membrane and contribute to
the complex antigenic specificity of Gram negative cells.Anti-
microbial activity of complexes is due to either killing the
microbes or inhibiting their multiplication by blocking their
active sites19. Since the molecular structure is quite similar,
the antibacterial activity of complex 1 is quite similar.
Fig. 1. Crystal structure of complex 1, showing 30 % probability
displacement ellipsoids (arbitrary spheres for the H atoms)
ACKNOWLEDGEMENTS
The work was co-financed by grants from a Project Funded
by PriorityAcademic Program Development of Jiangsu Higher
Education Institutions, P.R. China.
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