La(III) complex involving the O,N-donor environment of quinazoline-4(3H)- one Schiff's base and their antimicrobial attributes against methicillin-resistant Staphylococcus aureus (MRSA)

Article abstract of DOI:10.1016/j.saa.2014.03.115

The incidence of methicillin-resistant Staphylococcus aureus increased during the past few decades, so there is an urgent need of new antimicrobial agents if public health is concerned. Though the Schiff's bases and La(III) complex have enormous biological activity, but less attention was given in their synthesis. In the present investigation, we synthesized a new (E)-3-((2-hydroxynaphthalen-1-yl) methyleneamino)-2-methylquinazoline-4(3H)-one HNMAMQ Schiff's base by the condensation of 3-(2-aminophenyl) quinazolin-2-methyl-4(3H)-one and 2-hydroxy-1-naphthaldehyde. The Schiff's base HNMAMQ and its La(III) complex were characterized by elemental analyses, IR, NMR, mass spectra, and thermal studies. The newly synthesized Schiff's base HNMAMQ and its La(III) complex were evaluated for their antimicrobial activity against methicillin-resistant Staphylococcus aureus isolated from the Gulbarga region in India. The Schiff's base HNMAMQ and its La(III) complex showed good antimicrobial activity and thus represents a potential new drug of choice.

Full text of DOI:10.1016/j.saa.2014.03.115

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 634–638
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
La(III) complex involving the O,N-donor environment of
quinazoline-4(3H)-one Schiff’s base and their antimicrobial attributes
against methicillin-resistant Staphylococcus aureus (MRSA)
a
b
K. Siddappa a, , Sunilkumar B. Mane , Deene Manikprabhu
⇑
a Department of Post-Graduate Studies and Research in Chemistry, Gulbarga University, Gulbarga 585 106, Karnataka, India
b Department of Microbiology, Gulbarga University, Gulbarga 585 106, Karnataka, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
Synthesis and characterization of new
quinazoline-4(3H)-one Schiff’s base
and its La(III) complex.
Methicillin-resistant Staphylococcus
aureus were isolated from Gulbarga
region, India.
La(III) complex shows enhanced
antimicrobial activity over Schiff’s
base.
a r t i c l e i n f o
a b s t r a c t
Article history:
The incidence of methicillin-resistant Staphylococcus aureus increased during the past few decades, so
there is an urgent need of new antimicrobial agents if public health is concerned. Though the Schiff’s
bases and La(III) complex have enormous biological activity, but less attention was given in their
synthesis. In the present investigation, we synthesized a new (E)-3-((2-hydroxynaphthalen-1-yl) meth-
yleneamino)-2-methylquinazoline-4(3H)-one HNMAMQ Schiff’s base by the condensation of 3-(2-ami-
nophenyl) quinazolin-2-methyl-4(3H)-one and 2-hydroxy-1-naphthaldehyde. The Schiff’s base
HNMAMQ and its La(III) complex were characterized by elemental analyses, IR, NMR, mass spectra,
and thermal studies. The newly synthesized Schiff’s base HNMAMQ and its La(III) complex were evalu-
ated for their antimicrobial activity against methicillin-resistant Staphylococcus aureus isolated from
the Gulbarga region in India. The Schiff’s base HNMAMQ and its La(III) complex showed good antimicro-
bial activity and thus represents a potential new drug of choice.
Received 1 November 2013
Received in revised form 21 March 2014
Accepted 29 March 2014
Available online 16 April 2014
Keywords:
Quinazoline-4(3H)-one
Antimicrobial activity
Methicillin-resistant Staphylococcus aureus
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
tance rhythm of this organism against different antibiotics [1].
Today’s challenging task is to synthesize a new antimicrobial agent
Staphylococcus aureus (S. aureus) resistant to methicillin is a
major problem that the world is now facing. The antibiotic era,
barely 60 years old, is also threatened because of increase resis-
that does not generate microbial resistant so, studies in finding out
new antimicrobial agents against methicillin-resistant Staphylococ-
cus aureus (MRSA) are desperately required if public health crisis is
to be averted. MRSA were isolated at low levels, a decade ago, but
is currently widespread [2] due to the development of resistant to
methicillin antibiotic which exponentially increased high
⇑
Corresponding author. Tel.: +91 9845644075.
E-mail address: siddappa_65@rediffmail.com (K. Siddappa).
http://dx.doi.org/10.1016/j.saa.2014.03.115
1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

K. Siddappa et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 634–638
635
morbidity and mortality [1,3] so there is an urgent need of a new
antimicrobial agent who does not generate resistance against
MRSA.
oxazin-4-one. The second step involves the reaction between
2-methyl-4H-benzo [d] [1,3] oxazin-4-one and hydrazine hydrate
in 20 mL hot methanol to afford 3-amino-2-methylquinazoline-
4(3H)-one [18]. Finally, in the third step the simple condensation
reaction between 3-amino-2-methyl quinazoline-4-one and
2-hydroxy-1-naphthaldehyde results in the formation of the
Schiff’s base (E)-3-((2-hydroxynaphthalen-1-yl) methyleneami-
no)-2-methylquinazoline-4(3H)-one HNMAMQ as presented in
supplementary file Fig. S1. The progress of the reaction was contin-
uously monitored by the aid of thin layer chromatography (TLC) on
a silica gel-G coated aluminum plates (Merck) and spots were visu-
alized by exposing the dry plates to iodine vapors.
Alternate to antibiotics are the Schiff’s base and its metal com-
plexes [4] at present, playing a key role in the development of coor-
dination chemistry, especially the quinazoline-4(3H)-one [5,6]
having vast applications in the field of medical microbiology such
as anti-cancer and anti-viral activities. Further, its metal com-
plexes have been widely studied because of their anti-fungal, anti-
bacterial, anti-tubercular activities, herbicidal applications, and
cheating abilities which attracted remarkable attention [7].
Recently, there has been growing interest in the lanthanide-
Schiff’s base complexes owing to the important applications of
both metals and ligands [8]. Lanthanides are the rare earth com-
plexes [9] discovered in the 19th century and form the longest ser-
ies of the periodic table. They are the best ions form, highly stable
complexes because of their nature with a high coordination num-
ber [10]. Initially coordination chemistry of lanthanides was lim-
ited as a strongly chelating ligands but, with the development of
new complex forming compounds, a significant number of lantha-
nide complexes with various types of ligands were synthesized and
characterized [11] and showed a wide variety of medicinal and bio-
chemical applications. In particular, they are used as a diagnostic
tool in biomedical analysis as MRI contrast agents [12,13], in Flu-
oro-immuno assays [14], as an anti-cancer, and antimicrobial
agent [15].
In the light of above vast applications of lanthanide complexes,
their scanty reports when compared to d-block transition metal
complexes [16] and in continuity our work on chemistry of quinaz-
oline-4(3H)-one Schiff’s base and its metal complexes [17] in the
present study, we made an attempt to solve challenging task,
‘‘methicillin drug resistant problem’’ in this regard, we synthesized
a new lanthanide [La(III)] complex derived from (E)-3-((2-hydrox-
ynaphthalen-1-yl) methyleneamino)-2-methylquinazoline-4(3H)-
one HNMAMQ and assayed their antimicrobial activity against
MRSA isolates collected from various hospitals and health care
centers in the Gulbazzrga region.
Chemistry of HNMAMQ
Obtained as yellowish green solid has a Molecular formula
C
20H15N3O2, Yield 85%, mp. 270 °C. Anal. (%): Calcd. C, 72.94; H,
4.59; N, 12.76. Found: C, 72.24; H, 4.12; N, 11.97. IR (KBr, cmÀ1):
3385 (OH), 1580; (˜C@N), 1690;
(˜C@O). 1H NMR (DMSO-d6,
m
m
m
d ppm): 10.61, (s, 1H, OH); 8.35, (s, 1H, ˜C@N); 2.41–2.43, (s, 3H,
CH3); 6.82–8.54, (m, 10H, ArAH). MS m/z: 329 [M+].
Synthesis of La(III) complex
The method used for the synthesis of metal complex involves
the interaction of metal salt with ligand in
a molar ratio
(M:L = 1:1). A hot methanolic solution (30 mL) of the Schiff’s base
HNMAMQ was added to a stirred solution of La(III) chloride in
methanol (20 mL) having a required molar ratio of M:L (1:1). The
mixture was refluxed for about 3 h at a temperature of ꢁ78 °C.
Subsequently, sodium acetate was added to adjust the pH 6.0–
7.0. The solid, intense colored complex formed was immediately
precipitated out. The precipitated complex was further refluxed
for about 1 h to check its stability. Later it was filtered off, washed
thoroughly with water along with little warm methanol for appar-
ent dryness and finally dried in a vacuum over fused CaCl2.
The chemistry of La(III) complex
Obtained as white solid has a Molecular formula [La(C20H14N3-
O2)Cl2H2O] Yield 78%, mp. 296 °C. Anal. (%): Calcd. C, 43.19, H, 2.90,
N, 7.56, M, 24.98, Cl, 12.75. Found: C, 43.08, H, 2.52, N, 7.28, M,
Materials and methods
24.74, Cl, 12.54. IR (KBr, cmÀ1): 1566,
m(˜C@N); 1675, m(˜C@O),
Blood agar, Mannitol salt agar, Mueller Hinton agar (MHA) and
Mueller Hinton Broth (MHB) were procured from Hi-media. Ele-
mental analysis (C, H and N) were carried out using micro analyt-
ically Perkin Elmer 240C Instrument. IR spectra of the Schiff’s base
HNMAMQ and its La(III) complex in KBr pellets were recorded on
Perkin Elmer Spectrum one FT-IR spectrometer in the spectral
range 4000–350 cmÀ1. The 1H NMR spectra were recorded on
AMX-400 NMR spectrometer, using Tetramethylsilane [TMS] as
an internal standard and dimethyl sulphoxide [DMSO] as a solvent.
Mass spectra were recorded with a JEOL GCMATE II GC–MS mass
spectrometer. Magnetic susceptibilities were measured on a Gouy
balance at room temperature using Hg[Co(NCS)4] as calibrant.
Thermal analyses were measured from room temperature to
1000 °C in N2 on a Perkin Elmer, Diamond TG/DTA model thermal
analyzer with a heating rate of 10 °C minÀ1. The molar conduc-
tance data were recorded on the ELICO-CM-82T conductivity
bridge in DMF solution at concentration ꢁ10À3 M.
3395 (H2O). 1H NMR (DMSO-d6, d ppm): 8.42, (s, 1H, ˜C@N);
2.64–2.67, (s, 3H, CH3); 2.71 (s, 1H, H2O), 6.97–8.72 (m, 10H,
ArAH). MS m/z: 556 [M+], 558 [M + 2] and 560 [M + 4].
Isolation and identification of MRSA
Samples like blood, pus and other exudates were obtained from
different hospitals and health care centers of the Gulbarga region
in India. Initially, all the samples were first inoculated onto blood
agar plates. The plates were incubated at 37 °C for 24–48 h. Fur-
ther, the colonies obtained on blood agar after incubation was
again inoculated onto mannitol salt agar; the plates were once
again incubated at 37 °C for 24–48 h. The preliminary identifica-
tion of S. aureus were detected by change in color of the medium
from red to yellow due to mannitol fermentation. Further, the S.
aureus were identified based on morphological, microscopic and
biochemical tests [1] among the identified S. aureus, MRSA were
detected phenotypically by means of antibiotic susceptibility test
as per the guidelines recommended by the Clinical and Laboratory
Standards Institute (CLSI-2012) [19].
Chemistry of Schiff’s base HNMAMQ and its La(III) complex synthesis
Easy and efficient strategy was undertaken to synthesize the
target quinazoline Schiff’s base which involves the following three
steps. In the first synthesis step, a warm solution of methyl anthra-
nilate reacts with acetic anhydride in 20 mL methanol, results in
the formation of a cyclic compound 2-methyl-4H-benzo [d] [1,3]
Antimicrobial activity against MRSA
The antibacterial activities of newly synthesized Schiff’s base
HNMAMQ and its La(III) complex against MRSA were evaluated

636
K. Siddappa et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 634–638
on MHA by making a lawn of MRSA (0.5 McFarland) with the aid of
sterile cotton swabs, wells of 6 mm diameter were punched care-
fully with the help of a cork borer. Further, the wells were loaded
thalene moiety. The absence of this band upon complexation, in
other words proton substitution by cation coordination to the oxy-
gen atom of the Schiff’s base HNMAMQ reveals the participation of
phenolic oxygen in bonding with La(III) ion via deprotonation [23].
The 1H NMR spectrum of the La(III) complex shows the disappear-
ance of AOH proton signal at d 10.61 ppm (s, 1H) (D2O exchange-
able) of the Schiff’s base HNMAMQ upon complex formation,
further support the participation of phenolic oxygen in coordina-
tion via deprotonation. In the IR spectrum of the Schiff’s base
HNMAMQ a characteristic high intense band was appeared in the
with 150 lg/mL (in DMSO as a solvent) of different investigated
test compounds. The plates were incubated at 37 °C for 24 h. Anti-
bacterial activity was determined by measuring the zone of
inhibition.
Determination of minimum inhibitory concentration (MIC)
The MIC is defined as the lowest concentration of an antimicro-
bial agent that will inhibit the visible growth of microorganisms. To
determine MIC different volumes of investigating test compounds
region of 1598–1592 cmÀ1 due to azomethine
m(˜C@N), which
experiences a negative shift of 15–20 cmÀ1 in La(III) complex,
mainly due to the drift of the lone pair density of azomethine nitro-
gen towards the metal ions, indicates coordination of azomethine
nitrogen with the metal ions [24]. Further, this was confirmed by
1H NMR spectra, owing to the downfield shift of the azomethine
proton signal from d 8.35 ppm (s, 1H, ˜CH@N) of the Schiff’s base
HNMAMQ to d 8.42 ppm (s, 1H, ˜CH@N) in La(III) complex, shows
the involvement of ˜CH@N nitrogen in coordination. In the IR spec-
trum of the Schiff’s base HNMAMQ, a high intense, strong band in
the region of 1720–1715 cmÀ1 was assigned to the carboxyl group
of quinazoline ring (˜C@O). However, upon complex formation
shows a downfield shift of 20–30 cmÀ1 indicates the participation
of carboxylic oxygen [25]. The low frequency skeletal vibrations
(5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 lg/mL) and MRSA culture
(0.5 McFarland) was added into MHB and were incubated at 37 °C
for 18 h. The last tube with no growth of microorganism was
recorded to represent the MIC. The antibacterial activities of test
compounds were compared with standard methicillin antibiotic.
Results and discussion
Based upon the analytical and physical data it was clearly
revealed that, all the synthesized compounds were very stable
for a long period of time and non hygroscopic in nature at room
temperature. The complex was sparingly soluble in common
organic solvents, however completely soluble in DMF and DMSO.
The synthesized compounds were characterizations via their
physical, analytical, and spectral data. The stoichiometry reaction
between the La(III) ion and the Schiff’s base HNMAMQ in a molar
ratio of M:L (1:1) resulted in the formation of the metal complex
of type ML [where M = La(III)] exhibiting octahedral geometry
through the involvement of azomethine nitrogen and carboxylic
oxygen with metal ion as shown in Fig. 1. The observed molar con-
ductance values were in the range of 55–57 OhmÀ1 cm2 molÀ1 in
DMF, indicates the electrolytic nature of metal complex [20]. The
metal and chloride contents were determined as per standard pro-
cedure [21]. The magnetic moment of the La(III) complex was con-
sistent with the presence of unpaired 4f electrons and close to the
values for the free metal ions as reported by Van Vleck and Frank
[22]. These observations suggest that the 4f electrons of the La(III)
do not take part in bond formation in these species suggesting its
diamagnetic nature.
bands in La(III) complex assigned to
m(MAO) and m(MAN) were
appeared in the region of 557–550 cmÀ1 and 452–445 cmÀ1
respectively, which further support the coordination of the Schiff’s
base HNMAMQ through the nitrogen of azomethine, carboxylic
and phenolic oxygen with La(III) ion [26]. The
m(MAN) band was
usually sharp and strong while, the (MAO) band was broad, since
m
a large dipole moment change was involved in the vibrations of the
MAO bond comparison to that of the MAN bond. Hence it was
expected that the
in compared to that of the
length was shorter than the MAN bond length and this also sup-
ports the occurrence of the (MAO) band at a higher energy in
comparison to that of the (MAN) band. Moreover, a weak band
was observed in the range of 355–350 cmÀ1 assigned to
(MACl),
m(MAO) band should appear at a higher energy
m(MAN) band [27]. The MAO bond
m
m
m
characteristic of the chloride atom in La(III) complex and was fur-
ther confirmed by quantitative chloride estimation. In comparison
with Schiff’s base HNMAMQ, the La(III) complex shows the appear-
ance of broad band around 3405–3395 cmÀ1 attributed to the
The elemental analysis (C, H, and N) data of the Schiff’s base
HNMAMQ and its La(III) complex were in good agreement with
proposed molecular formula.
m
(OH) stretching frequencies shows the existence of coordinated
water molecules and the appearance of characteristic rocking fre-
quency at 810 cmÀ1 [28] which was further confirmed through
thermal analysis study. The remaining signals were appeared in
their expected regions. A new characteristic singlet proton signal
at d 2.72 ppm owing to the presence of a coordinated water mole-
cule was obtained. Hence, from the above observations, it was evi-
dently concluded that the total number of protons calculated from
the integration curves and the values obtained from their C, H, and
N analysis is in agreement with each other thereby reflecting the
purity of compounds.
The infra red spectrum of the Schiff’s base HNMAMQ displays a
broad band in the region of 3385 cmÀ1 owing to
m(AOH) of naph-
The mass spectra of newly synthesized compounds were in
agreement with their structures. The proposed molecular formula
of each compound was confirmed by its molecular formula weight
with m/z values. The mass spectra of the Schiff’s base HNMAMQ
showed the formation of a molecular ion peak at m/z 329 [M]+,
whereas the La(III) complex shows the formation of a molecular
ion peak along with an isotopic peak at m/z 556, 558 and 560
[M]+, [M + 2]+ and [M + 4]+ corresponding to their molecular
formula.
Thermal gravimetrical analysis (TGA) for the La(III) complex
was carried out within
a temperature range from room
temperature up to 1000 °C under nitrogen atmosphere with a heat-
ing rate of 10 °C per min. The La(III) complex does not show weight
Fig. 1. Proposed structure of La(III) complex.

K. Siddappa et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 634–638
637
loss below 120 °C indicates the absence of lattice water. However,
it undergoes four stages of decomposition as follows:
thermal studies which explain the participation of azomethine
nitrogen, carboxylato oxygen and phenolic oxygen with La(III)
ion. Upon complex formation, the Schiff’s base HNMAMQ exhibit
octahedral geometry with La(III) ion. The antimicrobial activity of
the Schiff’s base HNMAMQ and its La(III) complex were evaluated
against clinically isolated MRSA, the MIC of the Schiff’s base
1. The initial weight loss of 3.28% (Cal. 3.23%) in the temperature
range of 195–220 °C account for the loss of coordinated water
molecule [29].
2. In the second step the resultant intermediate complex formed
above, underwent further degradation with weight loss in the
temperature range of 220–350 °C owing to the removal of chlo-
ride molecules (Obs. 13. 52%; Cal. 13.19%).
3. The third decomposition occurred with weight loss in the range
of 350–420 °C corresponds to the loss of AC9 H7N2O species
(Obs. 34.10%; Cal. 34.04%).
4. The fourth decomposition occurred in the temperature range of
420–625 °C with a weight loss of 8.80% (Cal. 8.76%) which
account for the loss of AHCN species.
HNMAMQ was estimated 35
of the Schiff’s base HNMAMQ and its La(III) complex increased the
antimicrobial activity with MIC 15 g/mL this could be explained
due to chelation theory. The Schiff’s base HNMAMQ alone and in
combination with La(III) complex showed excellent antimicrobial
activity the same can be used as a new antimicrobial agent to
decrease the MRSA incidence and also may be in future, useful in
the developing prospective pharmaceutical, and physiological
implications in the field of medicinal chemistry.
lg/mL, moreover the synergetic effect
l
Acknowledgement
Finally, the most stable oxide was formed, on further heating up
to 1000 °C. The weight of the residue corresponds to the formation
of the La2O3.
The authors are thankful to the Chairman, Department of
Chemistry, Gulbarga University, Gulbarga for providing laboratory
facilities, Chairman, Department of Microbiology, Gulbarga Univer-
sity, Gulbarga for providing facilities to carry out antimicrobial
activity and to Director, Indian Institute of Technology, Madras,
Chennai for providing spectral data. One of author Sunilkumar B.
Mane is thankful to UGC MRP [F. No. 37-171/2009(SR)], New Delhi
for providing financial assistance.
Antimicrobial activity of the Schiff’s base HNMAMQ and its La(III)
complex against MRSA
The Schiff’s base HNMAMQ exhibit the good antimicrobial
activity against MRSA with a zone of inhibition (15 mm) however,
upon complex formation with La(III), its antimicrobial activity
increase with a zone of inhibition (22 mm) as presented in supple-
mentary file Figs. S2 and S3. From the results it was clear that the
Schiff’s base HNMAMQ alone and in complex formation with La(III)
shows excellent antimicrobial activity.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2014.03.115.
The MIC of the Schiff’s base HNMAMQ and its La(III) complex
were varied from 5 to 50
registered the MIC value at (15
bial agent over the Schiff base HNMAMQ (35
l
g/mL, which reveals that, La(III) complex
g/mL) as an excellent antimicro-
g/mL) as compared
g/mL), as presented
l
References
l
[1] D. Manikprabhu, K. Lingappa, J. Pharm. Res. 6 (2013) 255–260.
[2] T.P. Tim Cushine, J.L. Andrew, Int. J. Antimicrob. Age. 26 (2005) 343–356.
[3] D. Nelson, D.M. Priscyla, I.H.D. Gabriel, L.A. Oswaldo, E. Elisa, J. Biomed.
Nanotechnol. 3 (2007) 203–208.
[4] M.K. Muraleedharan Nair, P.S. Ajitha, P.K. Rejimon, Int. J. Med. Pharm. Res. 1
(2013) 185–191.
[5] A. Panagiotopoulos, T.F. Zafiropoulos, S.P. Perlepes, Inorg. Chem. 34 (1995)
4918–4920.
[6] K. Hemalatha, K. Girija, Int. J. Pharm. Pharm. Sci. 4 (2012) 99–103.
[7] M.A. El-Nawawy, R.S. Farag, I.A. Sabbah, A.M. Abu-Yamin, IJPSR 2 (2011) 3143–
3148.
[8] A.S. Ramasubramanian, B. Ramachandra Bhat, R. Dileep, Synth. React. Inorg.
Met.-Org. Nano-Met. Chem. 42 (2012) 548–553.
[9] R. Gupta, N. Agrawal, K.C. Gupta, Res. J. Pharm. Bio. Chem. Sci. 3 (2012) 50–56.
[10] Ali E. Sabik, M. Karabork, G. Ceyhan, M. Tumer, M. Dıgrak. Int. J. Inorg. Chem.,
http://dx.doi.org/10.1155/2012/791219.
[11] B.G. Kalagouda, C.H. Vidyadhar, A.P. Siddappa, R.P. Basavaraj, Met.-Based
Drugs, http://dx.doi.org/10.1155/2007/37348.
[12] C. Picard, N. Geum, I. Nasso, Bioorg. Med. Chem. Lett. 16 (2006) 5309–5312.
[13] S. Aime, S.G. Crich, E. Gianolio, G.B. Giovenzana, L. Tei, E. Terreno, Coord. Chem.
Rev. 250 (2006) 1562–1579.
[14] Y. Zheng, L. Fu, Y. Zhou, J. Yu, Y. Yu, S. Wang, H. Zhang, J. Mater. Chem. 12
(2002) 919–923.
[15] R.C. Sharma, S.P. Thripathi, K.S. Kanna, R.S. Sharma, Curr. Sci. 50 (1981) 748–
750.
[16] Z. Rzaczynska, A. Ostasz, M. Sikorska-Iwan, H. Gluchowska, E. Olszewska, S.
Pikus, J. Therm. Anal. Calorim. 84 (2006) 575–579.
[17] K. Siddappa, B.M. Sunilkumar, D. Manikprabhu, Sci. World J., vol. 2014, 13p,
Article ID 817365, http://dx.doi.org/10.1155/2014/817365.
[18] A.A.H. Al-Amiery, Y.K. Al-Majedy, S.A. Abdulhadi, A.H. Sadoon, Afr. J. Pure Appl.
Chem. 3 (2009) 218–227.
with the standard methicillin antibiotic (15
in supplementary file Table S1.
l
The antimicrobial activity of the Schiff’s base was rationalized
due to presence azomethine (˜C@N) group which imports in eluci-
dating the mechanism of transamination and resamination reac-
tions in the biological system [30]. The formation of hydrogen
bonds through the azomethine group with the active centers of
various cellular constituents, resulting in interference with normal
cellular processes [31]. Furthermore, it has also been suggested
that the Schiff base ligands with nitrogen and oxygen donor sys-
tems might inhibit enzyme production causing cell death [32].
The enhanced activity of metal complex than Schiff’s base can
explained by Tweedy’s chelation theory, which suggest that the
chelation could allow for the delocalization of
p-electrons over
the entire chelate ring and enhances the lipophilicity of the com-
plexes. This increased lipophilicity facilitates the penetration of
the complexes into lipid membranes, further restricting prolifera-
tion of the microorganisms [33]. On the other hand, Chelation is
not only the principle factor for antimicrobial activity since; it is
expected to be a function of steric, electronic and pharmacokinetic
factors along with mechanistic pathway. Other factors such as sol-
ubility, conductivity, dipole moment, size of metal ions, stability
constants of the complexes and their magnetic moments are also
reported to influence the microbial activity of the complexes [34].
[19] CLSI, Performing Standards for Antimicrobial Susceptibility Testing: Twenty-
Second Informational Supplement, CLSI Document M100eS22, Clinical and
Laboratory Standards Institute, Wayne, PA, 2012.
Conclusion
[20] W. Geary, J. Coord. Chem. Rev. 7 (1971) 81–122.
[21] A.I. Vogel, A Text Book of Quantitative Inorganic Analysis, third ed., Longman
ELBS, London, 1968.
[22] J.H. Van Vleck, A. Frank, Phys. Rev. 34 (1929) 1494–1496.
[23] A.L. El-Ansary, N.S. Abdel-Kader. Int. J. Inorg. Chem., 2012, 13p, Article ID
901415, http://dx.doi.org/10.1155/2012/901415.
In conclusion, herein we report the synthesis of new Schiff’s
base HNMAMQ and its La(III) complex. Formation of the
compounds were confirmed through IR, NMR, mass spectra, and

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K. Siddappa et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 130 (2014) 634–638
[24] D.C. Dash, A.K. Panda, P. Jena, S.B. Patjoshi, A. Mahapatra, Indian J. Chem. Soc.
79 (2002) 48–50.
[30] P.P. Dholakiya, M.N. Patel, Synth. React. Inorg. Met.-Org. Chem. 34 (2004) 553–
563.
[25] P. Venketeswar Rao, A. Venkata Narasaiah, Indian J. Chem. 42A (2003) 1896–
1899.
[31] N. Dharmaraj, P. Viswanathamurthi, K. Natarajan, Transition Met. Chem. 26
(2001) 105–109.
[26] G.B. Bagihalli, S.A. Patil, P.S. Badami, J. Enzyme Inhib. Med. Chem. 24 (2009)
730–741.
[32] Z.H. Chohan, M. Arif, M.A. Akhtar, C.T. Supuran, Bioinorg. Chem. Appl. 2006
(2006) 1–13.
[27] N. Ohkaku, K. Nakamoto, Inorg. Chem. 10 (1971) 798–805.
[28] S. Belaid, A. Landreau, S. Djebbar, O. Benali-Baitich, G. Bouet, J.P. Bouchara, J.
Inorg. Biochem. 102 (2008) 63–69.
[33] R. Natarajan, J. Ramaraj, S. Mariyyappan, B. Raja, R.Y. Chithu, Chem. Pap. 64
(2010) 318–328.
[34] N. Raman, R. Jeyamurugan, M. Subbulakshmi, R. Boominathan, C.R. Yuvarajan,
Chem. Pap. 64 (2010) 318–328.
[29] K.R. Surati, Spectrochim. Acta A 79 (2011) 272–277.