Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic β-diketone with various primary amine and 2,2′-bipyridyl

Article abstract of DOI:10.1016/j.saa.2011.03.008

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO₄ was synthesized by reaction of Mn(OAc)₃·2H₂O with HPMFP and 2,2′-bipyridyl. The corresponding Schiff base complexes were prepared by condensation of [Mn(bipy)(HPMFP)(OAc)]ClO₄ with ethylenediamine, ethanolamine and glycine (where HPMFP = 1-phenyl-3methyl-4- formyl-2-pyrazolin-5one, bipy = 2,2′-bipyridyl). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and ¹H and ¹³C NMR, FT-IR, mass spectrometry. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese(III) ion. The thermal stabilities, activation energy E^*, entropy change ΔS ^*, enthalpy change ΔH^* and heat capacity of thermal degradation for these complexes were determined by TGA and DSC. The in vitro antibacterial and antifungal activity of four coordination compounds and ligand HPMFP were investigated. In vitro activates of Bacillus subtillis (MTCC-619), Staphylococcus aureus (MTCC-96), Escherichia coli (MTCC-722) and Klebsiella pneumonia (MTCC-109) bacteria and the fungus Candida albicans (ATCC-90028) were determined. All the compounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff base.

Full text of DOI:10.1016/j.saa.2011.03.008

Spectrochimica Acta Part A 79 (2011) 272–277
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectroscopy and biological investigations of manganese(III) Schiff
base complexes derived from heterocyclic ˇ-diketone with various primary
ꢀ
amine and 2,2 -bipyridyl
∗
Kiran R. Surati
Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar 388120, Anand, Gujarat, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 September 2010
Received in revised form
The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO was synthesized by reaction
4
ꢀ
of Mn(OAc)3·2H2O with HPMFP and 2,2 -bipyridyl. The corresponding Schiff base complexes were
prepared by condensation of [Mn(bipy)(HPMFP)(OAc)]ClO4 with ethylenediamine, ethanolamine and
2
1 December 2010
ꢀ
glycine (where HPMFP = 1-phenyl-3methyl-4-formyl-2-pyrazolin-5one, bipy = 2,2 -bipyridyl). All the
Accepted 7 March 2011
compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry mea-
1
13
surements and H and C NMR, FT-IR, mass spectrometry. Electronic spectral and magnetic susceptibility
measurements indicate square pyramidal geometry around manganese(III) ion. The thermal stabilities,
Keywords:
Spectroscopy
Manganese(III) complexes
Thermal behaviour
Antimicrobial
*
*
*
activation energy E , entropy change ꢀS , enthalpy change ꢀH and heat capacity of thermal degradation
for these complexes were determined by TGA and DSC. The in vitro antibacterial and antifungal activity
of four coordination compounds and ligand HPMFP were investigated. In vitro activates of Bacillus subtil-
lis (MTCC-619), Staphylococcus aureus (MTCC-96), Escherichia coli (MTCC-722) and Klebsiella pneumonia
(MTCC-109) bacteria and the fungus Candida albicans (ATCC-90028) were determined. All the com-
pounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff
base.
©
2011 Elsevier B.V. All rights reserved.
1
. Introduction
using tumor cell lines. Recently Liguori et al. reported the non clas-
sical anticancer agents and its synthesis and biological evolution of
ꢀ
The chemistry of pyrazolone derivatives has attracted schol-
Zn(II) complexes derived from N,N-chelating ligands (4,4 -dinonyl-
ꢀ
arly attention because of its structures and application in diverse
areas [1–4]. Pyrazolone are key structure in numerous compound
of therapeutic importance [5], compounds containing this ring sys-
tem are known to display diverse pharmacological activities such
as inhibitors of mycobacterium tuberculosis [6], potent activity
of inhibiting protease-resistant prion protein accumulation [7],
anti-tumor necrosis factor activity [8,9] and inhibition of human
telomerase [10]. Recently Botta et al. reported synthesis, biolog-
ical evaluation and structure–activity relationship (SAR) analysis
of this class of compounds [11]. Recently many other researchers
are extensively working on pyrazolone based coordination com-
pounds and its antibacterial and anticancer activity [12,13]. Caruso
et al. [14] reported the synthesis, structure, and antitumor activity
of coordination complex cyclo-tetrakis[bis(1-phenyl-3-methyl-
2,2 -bipyridine) and diketonates [15]. Due to large diversity and
importance of pyrazolone based compounds many reviews avail-
able to explore the chemistry of pyrazolone, structures and its
applications [16,17].
Manganese(III) complexes have also merited much attention
in the field of biological study and application [18,19]. Recently
Pandya et al. reported the synthesis, characterization and antibac-
terial activity of Schiff base pyrazolone derivatives with transition
metal ions [20].
Taking into account of manganese(III), pyrazolone base
compounds and their therapeutic importance, here we use
pyrazolone derivatives as chelating agent with biologically rich
transition metal ion manganese(III). All these reports encour-
aged us to study the coordination chemistry and biological
behaviour of Schiff base complexes of manganese(III) though
there are fewer studies on the biological activities of man-
ganese(III) Schiff base complexes derived form pyrazolone based
moiety.
4
-benzoylpyrazolone-5-ato)␮-oxotitanium(IV)]. The antitumor
activity of this compound, encapsulated in a dipalmitoylphos-
phatidylcholine liposome, has been reported in vitro and in vivo
Our interest in this area is focused for a considerable time on
the investigation of coordination chemistry of transition metal
with using pyrazolone based ligand [21–26]. To gain more infor-
∗ Tel.: +91 09904368680; fax: +91 02692 236475.
E-mail address: kiransurati@yahoo.co.in
1
386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.03.008

K.R. Surati / Spectrochimica Acta Part A 79 (2011) 272–277
273
Fig. 1. General structure of Schiff base Mn(III) complexes.
mation about the structure and stereochemistry of such type
2.1. Preparation of the mononuclear mixed ligand complex
2.1.1. Preparation of Schiff base complexes
The Schiff base complexes were prepared by 1:1 interaction
of mixed ligand complex and ethylenediamine ethanolamine or
glycine (Fig. 1).
To the mixed ligand complex of Mn(III) (7.12 g, 0.0125 mol)
25 cm3 methanol was added ethylenediamine (0.75 g, 0.0125 mol),
ethanolamine (0.76 g, 0.0125 mol) or glycine (0.93 g, 0.0125 mol).
The solution was allowed to stand for 10 min at room temperature
and then refluxed for 2 h on a water bath. The solution was reduced
to 1/3 volume and allowed to stand overnight at room temperature.
A solid mass separated, was collected and washed by ether. Crys-
tallization was done with methanol and the complexes dried over
CaCl2 (Fig. 2).
of complexes, a detailed investigation on a new mono and
binuclear manganese(III) complexes with a ligand involving imine-
nitrogen, phenolic oxygen as donors has been initiated on our
part [23].
In present work, we report here the synthesis and charac-
terization of Schiff base complexes of manganese(III) derived
from the mononuclear mixed ligand complexes [23]. All
the compounds tested and discussed their in vitro activates
with bacteria Bacillus subtillis (MTCC-619), Staphylococcus
aureus (MTCC-96), Escherichia coli (MTCC-722) and Kleb-
siella pneumonia (MTCC-109) and the fungus Candida albicans
(
ATCC-90028).
2
. Experiment
2.2. Microbiological studies
The solvents were used after purification by the stan-
dard method described in the literature [27,28]. 1-Phenyl-3-
methyl-2-pyrazoline-5-one (E-Merck); ethylenediamine (BDH);
and ophenylenediamine (Fluka A.G., Switzerland) were used
as received. Mn(OAc) ·2H O was prepared by the oxida-
2.2.1. Test microorganism and medium
The bacterial subcultures for B. subtillis (MTCC-619), S. aureus
(MTCC-96), E. coli (MTCC-722) and K. pneumonia (MTCC-109) were
obtained from central diagnostic laboratory, Surat, Gujarat, India.
An antifungal susceptibility test was used C. albicans (ATCC-90028).
S. aureus, E. coli, K. pneumonia and C. albicans were cultured on
Brain Heart Infusion Broth (BHI) for the antibacterial and antifungal
activity.
3
2
tion of [Mn (␮ -O)(OAc) (H2O) ]·3H O using Gündüz’s method
3
3
6
3
2
[
29]. 1-Phenyl-3methyl-4-formyl-2-pyrazolin-5-one was syn-
thesized and characterized previously [25,30] by condensa-
tion of 1-phenyl 3-methyl-2-pyrazoline 5-one with DMF and
POCl3.
Elemental analyses (C, H, N) were performed at CDRI, Lucknow.
Solid-state infrared spectra were recorded with a Perkin-Elmer IR
spectrophotometer using KBr pellets at SICART, Vallabh Vidyana-
2.2.2. Method
The compounds were tested for their antimicrobial activity
by the minimum inhibitory concentration (MIC) [31] of mononu-
clear complexes and their corresponding Schiff base complexes of
Mn(III). Each compound was dissolved in DMF or DMSO or appro-
priate solvent at different concentrations of 2.5, 5, 10, 15, 20, 25,
30, 35, 40, 45 and 50 ␮g/mL. The solutions of standard drug, Strep-
tomycin was prepared in the same concentrations. Inoculums of
the bacterial culture were prepared. To a series of tubes containing
1 mL each of Mn(III) complexes solution with different concen-
trations and 0.2 mL of inoculum was added. Further 4.0 mL of the
sterile water was added to each of the test tubes. These test tubes
1
13
gar, Anand.
H
and
C NMR spectra were recorded with
JEOL-GSX-400 using CDCl3 as a solvent and TMS as an internal ref-
erence at Department of Chemistry, S.P. University, Anand. Mass
spectra (EI) were obtained on a JEOL D-300 mass spectrometer at
SAIF, IIT Madras, Chennai. The FAB mass spectra were recorded on
a JEOL SX 102 mass spectrometer using Argon/Xenon (6 kV, 10 mA)
as the FAB gas. The accelerating voltage was 10 kV and the spec-
tra were recorded at room temperature by using m-nitrobenzyl
alcohol (NBA) as matrix. Electronic spectra in the 200–800 nm
range were obtained in acetone on “SHIMADZU” UV 160A using
3
quartz cell of 1 cm . Magnetic measurements were carried out at
room temperature by the Gouy method using Hg[Co(SCN) ] as cal-
4
ibrant at Department of chemistry, Vallabh Vidyanagar, Anand.
Molar conductance of the mixed ligand Schiff base complexes
was measured on Systronics direct reading conductivity meter
type CM-82T. TGA/DTA was carried out on universal V3.0G TA
◦
◦
instrument in the range 0–700 C at a heating rate of 10 C/min
under nitrogen at Department of Chemistry, Vallabh Vidyanagar,
Anand. DSC was carried out on universal V3.0G TA instrument in the
◦
range 0–300 C at Department of Chemistry, Vallabh Vidyanagar,
Anand.
Fig. 2. Mass spectra of ligand PMFP.

2
74
K.R. Surati / Spectrochimica Acta Part A 79 (2011) 272–277
Table 1
Analytical and physical data of PMFP ligand and Schiff base complexes.
◦
Compounds
Colour (% yield)
m.p./ C
Elemental analysis; experimental (calculated) %
ꢁeff/B.M.
Conductance/
−
1
2
−1
ꢂ
cm mol
C
H
N
Mn
–
Cl
–
Ligand
HPMFP(C11H10N2O2)
Yellow
176
193
166
65.92 (65.3)
5.04 (4.9)
12.97 (13.0)
–
–
[
Mn(PMFP)(dipy)(OAc)]ClO4 Brown
C23H20MnN4O8Cl)
Mn(PMFP-en) (dipy)
48.30 (48.38)
48.91 (48.98)
3.50 (3.53)
4.23 (4.28)
9.80 (9.82)
9.61 (9.62)
8.95 (8.96)
6.20 (6.21)
5.81 (5.78)
5.02
4.97
107
116
(
[
Brown
13.69 (13.71)
(
(
OAc)]ClO
C25H26MnN6O7Cl)
[
[
Mn(PMFP-EA)
Brown
172
192
48.43 (48.90)
47.74 (47.73)
4.03 (4.10)
3.66 (3.56)
11.30 (11.41)
11.14 (11.15)
8.87 (8.95)
8.75 (8.64)
5.80 (5.78)
5.60 (5.65)
5.03
5.10
122
126
(
(
dipy)(OAc)]ClO4
C25H25MnN5O8Cl)
Mn(PMFP-Gly)
Dark brown
(
(
dipy)(OAc)]ClO4
C25H26MnN5O9Cl)
appeared at 1624 cm 1 is assigned to ꢃC O which is shifted to
−
were incubated for 24 h and observed for presence of turbidity. This
method was repeated by changing compounds with standard drug
lower wave number because of intramolecular hydrogen bonding.
−
The pyrazoline ring ꢃC N and ꢃC C are observed at 1541 cm
1
(
Streptomycin) for comparison. The minimum inhibitory concen-
−
1
−
1
tration at which no growth was observed was taken as the MIC
values.
and 1510 cm respectively. The bands observed at 1397 cm and
−
1
794 cm
can be assigned to in-plane and out of plane bending
modes of aldehydic C–H [32]. The medium-sharp band observed at
−
1
3
. Results and discussion
845 cm is attributed to out-of-plane bending of the bonded –OH
group. All the data indicate that the PMFP is an enol form only.
The FT-IR spectral data of the Mn(III) mononuclear complex and
the Schiff base complexes are given in Table 2. The Mn(III) mononu-
clear mixed ligand complexes does not show a band between
The newly synthesized ligand PMFP and their mixed ligand
complexes were stable. They were soluble in organic solvents like
methanol, ethanol, acetone, DMF and DMSO. The analytical data
agreed were in good agreements with the proposed structure of
ligand and its mixed ligand complexes (Table 1).
−
1
3600 and 3400 cm
the fifth position is deprotonated after complexation. A new band
indicating the –OH hydrogen of PMFP at
−
1
in all complexes at 1328–1353 cm
is due to the enolic group
3
.1. NMR spectra
ꢃC–O [25,33]. On coordination ꢃC N shifts to lower wavenum-
−
1
−1
from 1640 to 1660 cm for free C N. The
ber 1600–1620 cm
The 1H NMR spectrum of ligand shows a broad singlet at ı
.49 ppm due to –OH proton, indicating that the ligand is in the
−1
×
band at 3320 cm show that NH2 group of ethylendiamine Schiff-
base complex is not coordinated to the metal ion. The sharp band
8
−
1
enol form [24]. The spectrum also shows the phenyl multiple at ı
.3–7.9 ppm, asharpsinglet at ı 1.2 ppm assignedtomethyl protons
at 3515 cm in ethanolamine complex of Mn(III) correspond to
free –OH of ethanolamine. In the glycine complex broad bands
7
−
1
−1
of the pyrazoline ring, and the aldehyde proton at 9.85 ppm. HPMFP
is in the enol form only. The 13C NMR spectrum of ligand show
characteristic peck for C3, C4 and C5 due to which pyrazolone ring
carbon atoms resonates at ı 131.5, 110.2 and 152.4. The formation
of aldehyde was confirmed with the carbon resonate at ı 192.1 for
at 3350–3100 cm and 1666 cm are assigned for undissociated
carboxylic group of glycine. In all the complexes, a weak band is
−
1
obtained at 1566–15491 cm region. This may be due to asym-
metric COO stretching of the acetate group. The symmetric COO
stretching band appeared at 1433–1423 cm region [33,34]. The
presence of counter ion perclorate (ClO4 ) is confirmed through a
weak band at 914 cm due to the symmetrical stretching mode
−1
−
C
O. Other phenyl ring and methyl carbon atoms are observed in
−
1
the range of ı 121.1–126.5 and 8.1 respectively.
−
1
(
IR-forbidden) and an asymmetrical stretching mode at 1100 cm
(IR-allowed). This shows that (ClO4 ) has Td symmetry [25,35,36].
−
3.2. Infrared spectra
The IR spectra of ligand show characteristics band at
−1
3.3. Magnetic measurement
3
3
400–3300 cm due to ꢃ(OH). Free ꢃ(OH) is generally observed at
−1
500–3600 cm ; the observed lower value is due to intramolecu-
The magnetic moment of the mononuclear mixed ligand com-
lar and intermolecular H-bonding [24,25]. The IR spectrum of the
lignad shows doublet at 2755 and 2816 cm
assigned to the aldehydic ꢃC–H, whereas two moderately intense
bands are observed at 3020 cm and 2877 cm , due to aromatic
−1
plex and its Schiff base complexes of Mn(III) show ꢁeff in the range
(Fermi resonance)
4
4
.97–5.10 B.M., indicating that Mn(III) chelates are high spin d
3
1
−1
−1
configuration (t2g , eg ). This value is expected for four unpaired
electrons and lack of any kind of exchange interaction [23].
and aliphatic ꢃC–H respectively. The very sharp absorption band
Table 2
FT-IR and electronic spectral data of complexes and their assignments.
Complex
ꢃCOO
Str.
ꢃC N coord.
ꢃC N (cyclic)
ꢃC–O
Str.
d–d (cm−1)
Charge transfer
−
1
band (cm
)
[
[
[
[
Mn(PMFP)(dipy)(OAc)]ClO4
1566, 1360
1550, 1368
1549, 1368
1550, 1369
–
1600
1620
1609
1593
1596
1598
1599
1353
1328
1353
1353
23,529
48,543, 41,034
42,016, 36,496
42,372, 36,101
42,372, 36,231
Mn(PMFP-en) (dipy) (OAc)]ClO4
Mn(PMFP-EA) (dipy)(OAc)]ClO 4
Mn(PMFP-Gly) (dipy)(OAc)]ClO4
25,063, 20,080, 13,559
26,343, 13,568
26,666

K.R. Surati / Spectrochimica Acta Part A 79 (2011) 272–277
275
Fig. 3. Mass spectra of Schiff base complex [Mn(PMFP-en) (dipy) (OAc)]ClO4.
3.4. Electronic spectra
Prominent peaks for (C H5N)+ and (C H5)+ ions are observed
6 6
at m/e = 91 and 77. Molecular mass of all the metal complexes
performed with FAB mass spectrometer. A FAB mass spectrum
(Fig. 4) of representative complex [Mn(PMFP-en) (dipy) (OAc)]ClO4
was recorded. The Schiff base complexes [Mn(PMFP-en) (dipy)
(OAc)]ClO4 shows characteristic molecular ion peak at m/z = 612
UV–visible spectra of mononuclear manganese(III) complexes
and their Schiff base complexes were carried out in methanol. The
data are summarized in Table 2.
The absorption spectra of mononuclear mixed ligand com-
−
1
−1
+
+
plexes show an intense band at 36,496 cm
and 23,502 cm
[M] . One other peak observed at m/z = 614 [M+2] may be due to
isotopic abundance peak for Cl atom. The peak observed at 571 m/z
due to interligand transition and d–d transition respectively. The
absorption spectra of Schiff base chelates exhibit (LMCT) band
ꢀ
and 470 m/z are due to removal of fragment acetate (OAc) and 2,2 -
−
1
between 33,445 and 36,496 cm whereas d–d transition at 25,063,
bipyridine respectively. Other fragments are in good agreement
with the complexes structure [21,25].
−1
−1
−1
−1
2
0,080, 13,559 cm , 18,182 cm and 23,809 cm , 13,559 cm
in ethylenediamine, ethanolamine and glycine Schiff base com-
5
5
plexes respectively. These can be assigned to B → E(ꢃ ),
1
3
3.6. Thermogravimetric analysis
5
5
5
5
B → B (ꢃ ) and B → A (ꢃ ) respectively. Since, Mn(III) ion
1
2
2
1
2
1
is easily reducible, charge transfer will be from ligand to metal
The thermal study of complexes and its kinetic parameter
were determined. The kinetics of heterogeneous condensed phase
reactions that occur under nonisothermal conditions is usually
(
LMCT) correspond to ␲ → t2 transition [21,35]. Keeping in view
the monoanionic, bidentate nature of PMFP and their Schiff base
ligands, bidentate nature of 2,2 -dipyridyl and monodentate coor-
ꢀ
dinating behaviour of the acetate group, a square-pyramidal
structure seems to be the most probable one. It is further evidenced
−
1
by the presence of a ligand field band around 18,000–20,000 cm
diagnostic of C4V symmetry [37].
3.5. Mass spectra
Mass spectra of all the compounds stand in good agreement
with proposed structure, the representative mass spectra shown
in Figs. 3 and 4. The EI mass spectra of ligand PMFP and FAB mass
spectra of Schiff base complexes [Mn(PMFP-en) (dipy) (OAc)]ClO4
are carried out. Cleavage taking place in the HPMFP ligands and
fragments observed were in good agreement with structure of lig-
and [38,39]. Here the molecular ion peak and base peak at 202 m/z
is same, which is confirmed from abundance of molecular ion peak
[
39].
PMFP is characterized by mass spectral studies with a molec-
+
ular ion peak at 202(M ). A weak peak at m/e 201 is due to the
formation of (C11H N O ) , elimination of H from the molecule.
+
9
2
2
One intense peak at m/e 185 is due to removal of OH and forma-
Fig. 4. Thermal analyses of Mn(III) complexes where (1 = [Mn(PMFP)
(dipy)(OAc)]ClO4; 2 = [Mn(PMFP-en) (dipy) (OAc)]ClO4; 3 = [Mn(PMFP-EA)
(dipy)(OAc)]ClO 4; 4 = [Mn(PMFP-Gly) (dipy)(OAc)]ClO4).
+
tion of (C11H ON ) , a distinct but less abundant peak observed at
8
2
(
m/e = 174) due to elimination of CO from the parent compound.

2
76
K.R. Surati / Spectrochimica Acta Part A 79 (2011) 272–277
Table 3
The TG data for mononuclear Mn(III) complexes and its Schiff base complexes.
◦
◦
Complex
First step/ C
Mass loss, ꢀm
Second step/ C
Mass loss, ꢀm
Residue
Calc. (found) %
found/(calc.) %
found/(calc.) %
[
[
[
[
Mn(PMFP)(dipy)(OAc)]ClO4
129.6–184.0
128.1–190
129.0–198.0
131.1–188.6
9.18 (10.3)
10.12 (9.64)
9.92 (9.52)
11.2 (9.38)
216.5–488.46
240.2–465.9
258.1–476.9
228.1–484.0
80.72 (82.94)
81.28 (84.27)
80.10 (84.26)
81.29 (84.85)
MnO2
MnO2
MnO2
MnO2
13.21(15.25)
12.26 (14.28)
15.14 (14.03)
15.28 (13.83)
Mn(PMFP-en) (dipy) (OAc)]ClO4
Mn(PMFP-EA) (dipy)(OAc)]ClO 4
Mn(PMFP-Gly) (dipy)(OAc)]ClO4
Table 4
Kinetic data of the thermal decomposition of Mn(III) complexes.
−
1 ◦ −1
◦
◦
◦
◦
*
−1
*
−1 −1
E*/kJ mol−1
Complex
Cp/J g
C
TS/ C
T1/ C
T2/ C
TP/ C
ꢀH /kJ mol
ꢀS /kJ mol
K
Cs
[
[
[
[
Mn(PMFP)(dipy)(OAc)]ClO4
1.36
1.67
1.54
2.38
121.2
128.1
129.0
131.1
136.3
148
149.54
174.96
178.2
161.2
47.23
58.10
70.44
0.210
0.132
0.158
0.279
22.56
23.40
28.84
18.96
0.36
0.31
0.29
0.37
Mn(PMFP-en) (dipy) (OAc)]ClO4
Mn(PMFP-EA) (dipy)(OAc)]ClO4
Mn(PMFP-Gly) (dipy)(OAc)]ClO4
182.76
195.24
229.64
166.16
172.34
192..17
130.20
described by the equation [40].
thermal decomposition and its kinetic parameter were summa-
rized in Table 4.
ꢀ
ꢁ
∂
˛
T
E
ˇ
= A (˛) exp
−
f
∂
RT
3.7. Antimicrobial activities
where ˛ is the degree of conversion, ˇ is the linear heating rate,
Af(˛) is the differential conversion function. Each step of decom-
position in most of the reactions of the solids follows the trend
In vitro activates of B. subtillis (MTCC-619), S. aureus (MTCC-
6), E. coli (MTCC-722) and K. pneumonia (MTCC-109) bacteria
9
and the fungus C. albicans (ATCC-90028) were carried out for
mononuclear complex [Mn(bipy)(PMFP)(OAc)]ClO4 and their cor-
responding Schiff base complexes. The susceptibilities of certain
strains of bacteria and a fungus to the mononuclear complexes and
their corresponding Schiff base complexes were evaluated by mea-
suring the minimum inhibitory concentration at which no growth
was observed was taken as the MIC values. The results are given in
Table 5 for all the complexes. Comparison of MIC values (in ␮g/mL)
of Mn(III) complexes and standard drugs against different bacteria
are presented in Table 5.
In the literature, most of the Schiff base derivatives are
reported to be more active against representative bacteria and
fungus than their complexes under identical condition [41,42].
In our work, we also observed that the Schiff bases complexes
are more active against bacteria and fauns. From these results,
Heat
Solid 1−→ Solid 2 + Gas
This process comprises several stages, such as the chemical act
of breaking of bonds, breakdown of the solid 1 crystal lattice, forma-
tion of the crystal lattice of the solid 2 [40], absorption–desorption
of the gaseous products, diffusion of gas and heat transfer. The TG
curves show two step degradation first removals of one coordinated
acetate ion and second due to pyrolysis of organic ligand molecules.
Thermal stability of the complexes evaluated from the TG curves
shown in (Fig. 4) and order of stability as follows.
[
Mn(PMFP-en)(dipy)(OAc)]ClO4 > [Mn(PMFP-EA)(dipy)(OAc)]ClO4
>
[Mn(PMFP-Gly)(dipy)(OAc)]ClO4 > [Mn(PMFP)(dipy)(OAc)]ClO4
it is evident that [Mn(PMFP-Gly)(dipy)(OAc)]ClO , [Mn(PMFP-
4
From DSC it is confirmed that the complexes exhibited an
EA) (dipy)(OAc)]ClO4 and [Mn(PMFP-en) (dipy) (OAc)]ClO4 show
superior activity when compared to Streptomycin and towards
inhibiting all tested bacterial strains. The rest mononuclear com-
plex [Mn(bipy)(PMFP)(OAc)]ClO4 and ligand PMFP are less active
compared with Streptomycin. It is very interesting that introduc-
tion of Schiff base (azomethine) enhance the activity against the
bacteria and fungi, further it also creates the effect of metal ions on
the normal cell membrane. Schiff base complexes bear polar and
nonpolar properties together; this makes them suitable for per-
meation to the cells and tissues. Changing the hydrophilicity and
lipophilicity probably leads to bring down the solubility and per-
endothermic process. The area of the endothermic peak cor-
responding to the heat of fusion and the peak temperature
corresponds to the melting point. The melting (Tp), transition tem-
perature (T , T ), heat of reaction (ꢀH), and entropy (ꢀS) of the
1
2
complexes were calculated from DSC results and are given in
Table 3. The heat capacities Cp of the complexes were calculated
from DSC results and are given in Table 3. From the TG ther-
mal stability temperature (Ts) and removal of –COOCH3 group are
observed form the TG curves, further it is confirmed with DSC [25].
The final solid product of thermal decomposition is MnO . All the
2
Table 5
Minimum inhibitory concentration of the Mn(III) complexes and Streptomycin.
Complexes and standard
Range of concentration (2.5–50 ␮g/mL)
MTCC-619
MTCC-96
MTCC-722
MTCC-109
ATCC-90028
Ligand HPMFP
25
20
10
5.0
2.5
10
30
15
10
5.0
2.5
15
25
20
2.5
15
10
20
30
20
15
10
5.0
15
20
15
10
5.0
5.0
10
[
[
[
[
Mn(PMFP)(dipy)(OAc)]ClO4
Mn(PMFP-en) (dipy) (OAc)]ClO4
Mn(PMFP-EA) (dipy)(OAc)]ClO 4
Mn(PMFP-Gly) (dipy)(OAc)]ClO4
Streptomycin (standard)

K.R. Surati / Spectrochimica Acta Part A 79 (2011) 272–277
277
meability barrier of cell, which in turn enhances the bioavailability
of chemotherapeutics on one hand and potentiality at another
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[
[
[
[
43,44].
3.8. Molar conductance
The observed molar conductances of the manganese(III) com-
−
2
plexes (Table 1) in 10 M DMF solution are in the range
1
−1
2
−1
07–126 ꢂ cm mol . The molar conductance values are consis-
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[
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. Conclusion
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site from ˇ-diketone and N,N contributed from the neutral lig-
2
(
909–2945;
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ꢀ
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[
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from the FT-IR and thermal study it indicates coordination with
metal ion. Electronic spectra, magnetic moment and conductance
studyevidence thefactof square pyramidal geometryofcomplexes.
Moreover biological screening state that Schiff base complexes
enhance the activity against the bacteria and fungi due to Schiff
base complexes bear polar and nonpolar properties together; this
makes them suitable for permeation to the cells and tissues.
[
20] A.S. Thakar, K.K. Singh, K.T. Joshi
(4) (2010) 1396–1406.
§
, A.M. Pancholi , K.S. Pandya*, E-J. Chem. 7
§
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[
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