Synthesis, characterization and biological studies of a mannich base N-[Phenyl(pyrrolidin-1-yl)methyl]acetamide and its VO(IV), Mn(II) and Fe(II) complexes

Article abstract of DOI:10.14233/ajchem.2013.13389

N-[Phenyl(pyrrolidin-1-yl)methyl]acetamide was synthesized using Mannich reaction. The complexes of oxovanadium(IV), manganese(II) and iron(II) with this Mannich base were prepared and characterized by elemental analysis and spectral measurements. The spectral data reveal that the ligand acts as bidentate coordination to the metal ion through the CNC nitrogen and carbonyl oxygen atoms. Based on the UV spectral and magnetic moment data, octahedral geometry is assigned for all the complexes. The antimicrobial screening shows that the complexes are more active than the ligand.

Full text of DOI:10.14233/ajchem.2013.13389

Asian Journal of Chemistry; Vol. 25, No. 4 (2013), 2189-2191
http://dx.doi.org/10.14233/ajchem.2013.13389
Synthesis, Characterization and Biological Studies of a Mannich Base
N-[Phenyl(pyrrolidin-1-yl)methyl]acetamide and Its VO(IV), Mn(II) and Fe(II) Complexes
1,*
2
1
L. MURUGANANDAM , K. KRISHNA KUMAR and K. BALASUBRAMANIAN
1Department of Chemistry, Saranathan College of Engineering, Tiruchirapalli-620 012, India
2Department of Chemistry, National Institute of Technology, Tiruchirapalli-620 015, India
*Corresponding author: E-mail: lmuruganandam@yahoo.co.in
(Received: 5 January 2012;
Accepted: 17 October 2012)
AJC-12310
N-[Phenyl(pyrrolidin-1-yl)methyl]acetamide was synthesized using Mannich reaction. The complexes of oxovanadium(IV), manganese(II)
and iron(II) with this Mannich base were prepared and characterized by elemental analysis and spectral measurements. The spectral data
reveal that the ligand acts as bidentate coordination to the metal ion through the CNC nitrogen and carbonyl oxygen atoms. Based on the
UV spectral and magnetic moment data, octahedral geometry is assigned for all the complexes. The antimicrobial screening shows that
the complexes are more active than the ligand.
Key Words: VO(IV), Mn(II), Fe(II), Complexes, Mannich base, Disc diffusion, Octahedral geometry, Biological study.
Antibacterial and antifungal screening: Antibacterial and
antifungal activities of the ligand as well as the metal complexes
were tested in vitro against six bacterial species viz. E. coli, P.
aeruginosa, S. typhi, B. subtilis, S. pyogenes, S. aureus and the
two fungal species A. niger and A. flavus by disc diffusion method
using agar nutrient as medium and gentamycin as control.
INTRODUCTION
Due to strong basic character1, the carbonyl group in
acetamide is known to form metal complexes. They behave as
antimicrobial2, antirheumatic3, antipyretic4, analgesic and anti-
cancer5 drugs. In continuation of our earlier work reported6,7 on
Mannich base derivatives of acetamide and their transition metal
complexes, we are presenting here our extended studies.
RESULTS AND DISCUSSION
Infrared spectrum of PBA shows a sharp band at 3306
cm-1 is assigned to ν(NH) stretching vibration of the secondary
amide group9. The strong band at 1646 cm-1 may be attributed
to the ν(C=O) stretching mode. The medium absorption band
appears at 1149 cm-1 may be assigned to the new C-N-C bond
formed, due to the formation of Mannich base by the insertion
of pyrrolidinobenzyl group on acetamide.
EXPERIMENTAL
High purity acetamide(Merk), benzaldehyde(Merk),
pyrrolidine(Merk) were used as supplied. All other solvents
and metal salts used were of A.R. grade and used as such.
Synthesis of the ligand and complexes: N-[Phenyl-
(pyrrolidin-1-yl)methyl]acetamide (PBA) was synthesized by
employing the Mannich condensation8 reaction between
acetamide, benzaldehyde and pyrrolidine in 1:1:1 mol ratio.
The ethanolic solution of acetamide (5.90 g) was mixed with
benzaldehdye (10 mL) and pyrrolidine (7.1 mL) with constant
stirring in an ice bath. After 12 days, a pale yellow solid was
obtained. It was washed with water and acetone, dried and
recrystallized from ethanol. The yield of the compound was
78 %. (m.p: 120-124 ºC).
1
The H NMR spectrum10 shows a signal at δ 8.42 ppm,
which may be assigned to the secondary amide NH proton.
The methyl proton shows a singlet at δ 1.89 ppm. The multiplet
in the range δ 7.39-7.26 ppm is attributed to the protons of the
benzene ring. The protons of N(CH2)2 occurs at δ 2.51 and
1.65 ppm for α, α' and β, β' groups of pyrrolidine ring.
13
According to the C NMR spectrum obtained, the carbonyl
carbon shows a signal at δ 169.62 ppm. The signals observed
between δ 141.62-127.68 ppm are due to aromatic carbons of
phenyl group. The signals observed at δ 49.23 and 23.59 ppm
is due to at α, α' and at β, β' carbons of pyrrolidine ring.
UV-visible spectrum in DMF registers an intense split
bands centered at 287 and 226 nm which are presumably due
The hot methanolic solution of the metal salts was added
slowly with constant stirring to the hot ethanolic solution of
the ligand in 2:1 mol ratio. The insoluble complexes formed
were filtered, washed with methanol and ethanol to remove
the unreacted metal and ligand. They were dried in an air oven
at 80 ºC.

2190 Muruganandam et al.
Asian J. Chem.
TABLE-1
ANALYTICAL, CONDUCTANCE AND MAGNETIC MOMENT DATA FOR V(IV), Mn(II) and Fe(II) complexes of PBA
M (ohm-1
Elemental analysis (%): Found (calcd.)
Colour
(µeff. B.M)
Λ
Complex
cm2 mol-1)
C
H
N
M
SO4
VOSO4.PBA.H2O
32.08 (31.90)
3.51 (3.68)
3.41 (3.77)
4.72 (5.04)
5.89 (5.73)
6.21 (5.87)
7.50 (7.84)
10.65 (10.42)
11.95 (11.52)
8.08 (7.82)
19.13 (19.63)
19.80 (20.13)
13.28 (13.45)
06.22
Dark Green (1.73)
Colourless (5.31)
Brown (2.50)
MnSO4.PBA.2H2O 32.50 (32.70)
FeSO4.2PBA 44.30 (43.70)
15.43
31.59
to n→π* transition of the carbonyl group and π→π* transition
of the carbonyl group and the benzene ring. The mass spectrum
was obtained on electron ionization mode11. It shows a very
weak molecular ion peak at m/z = 218, which confirms the
molecular mass to this Mannich base (Fig. 1).
The electronic spectrum of Mn(II) shows the three
absorption bands at 18021, 24967 and 28305 cm-1 are attri-
6
butable to the three spin allowed transitions viz., A1g→4T1g,
6A1g→4Eg + 4A1g and 6A1g → 4T2g. The magnetic moment value
was found to be 5.31 B.M., suggest a hexa coordinate environ-
ment around Mn(II) ion (Fig. 3).
O
N
O
O
S
CH3
NH
O
O
H2O
Fig. 1. N-[Phenyl(pyrrolidin-1-yl)methyl]acetamide (PBA)
Mn
OH2
O
N
To find out the stoichiometry of the complexes, the
percentage of the metal ions, anions and CHN were determined.
The molar conductance values confirm that all the complexes
are non-electrolytes (Table-1). In the IR spectra of all the PBA
complexes, the stretching frequencies of C=O and C-N-C
bonds are lowered. This indicates that both carbonyl oxygen
and CNC nitrogen atoms are coordinated to the metal ions.
The bands at the ranges of 1150, 1000 and 900 cm-1 are due to
'SO' stretching mode; the 'OSO' bending mode splits up into
650, 600 and 580 cm-1 in the complexes. The frequencies
750(ν1) and 500(ν2) cm-1 observed are due to coordinated
sulphato group associated with bidentate chelation12. The bands
around 3500-3300, 1630-1600, 880-820, 705-620 and
540-520 cm-1 found only in the spectra of VO and Mn(II)
sulphato complexes indicates the presence of coordinated water
molecule.
CH3
NH
(M = Mn)
Fig. 3. MnSO4.PBA.2H2O
The UV-visible spectrum of Fe(II) registers highly intense
CT band at 39942 cm-1, which obscures the other very low
intensity d-d absorption bands. The µeff. value of 2.50 B.M. points
to a low spin octahedral structure for the complex (Fig. 4).
H3C
O
NH
O
S
O
O
O
The UV-visible spectrum of oxovanadium(IV) sulphato
complex shows a broad band at 17915 cm-1 due to the 2B2→2B1
transition and the one at 23184 cm-1 is ascribed to the 2B2→2A1
transition. The bands at 31976 and 39245 cm-1 are due to charge
transfer from ligand to metal. The EPR spectrum13 of this
complex do not show any resolution at g|| region, so it can be
assumed that gx and gy are same or nearly the same. The G
value of 1.9704 indicates strong interaction between the ligand
and the metal ion. The magnetic moment value is 1.73 B.M.,
which suggests a hexa coordinate geometry (Fig. 2).
Fe
N
O
N
CH3
NH
Fig. 4. FeSO4.2PBA
Antibacterial screening: Among the various complexes,
the VO(IV) sulphato complex was found to be the most active
against all the species. This pronounced activity may be
explained as follows. The lipids and polysaccharides are
important constituents of the cell wall and membrane, which
are very much preferred for the metal ion interaction. The cell
also contains many aminophosphates and carbonyl and
cysteinyl ligands, which maintain the integrity of the membrane
by acting as a diffusion barrier and also provide suitable sites
for binding. Since theVO(IV) sulphato complex has one labile
water molecule and coordinately unsaturated, the metal center
in this complex can exchange water molecules for biological
binding sites14. As a result of chelation, the polarity of the
O
O
S
V
O
O
OH2
O
O
N
CH3
NH
Fig. 2. VOSO4.PBA.H2O

Vol. 25, No. 4 (2013)
Studies of a Mannich Base N-[Phenyl(pyrrolidin-1-yl)methyl]acetamide and Its Metal(II) Complexes 2191
metal ion is reduced and the increased lipophilic character
favours the interaction of metal complexes of the cell, resulting
in interference with the normal cell processes.
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