Synthesis and spectral studies on metal complexes of s-triazine based ligand and non linear optical properties

Article abstract of DOI:10.1016/j.molstruc.2014.08.012

A series of transition metal complexes of type [ML] and [ML₂]Cl₂(where M = Cu(II), Ni(II), Co(II) have synthesized from 2-phenylamino-4,6-dichloro-s-triazine and 3,5-dimethyl pyrazole; their characteristics have been investigated by

Full text of DOI:10.1016/j.molstruc.2014.08.012

Journal of Molecular Structure 1076 (2014) 606–613
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis and spectral studies on metal complexes of s-triazine based
ligand and non linear optical properties
b
c
R. Shanmugakala a, , P. Tharmaraj , C.D. Sheela
⇑
a Department of Chemistry, Velammal College of Engineering & Technology, Madurai, India
b Department of Chemistry, Thiagarajar College, Madurai, India
c Department of Chemistry, The American College, Madurai, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
ꢀ
Metal complexes of two different
geometry are synthesized from novel
triazine ligand.
ꢀ
Ligand coordinates with metal ions
through pyrazolyl nitrogen and
triazine ring nitrogen.
ꢀ
ꢀ
The title compound can be applied in
the development of NLO materials.
The antimicrobial activity against 15
bacterial and 4 fungal strains shows
good results.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 May 2014
Received in revised form 3 August 2014
Accepted 3 August 2014
Available online 20 August 2014
A series of transition metal complexes of type [ML] and [ML2]Cl2 (where M = Cu(II), Ni(II), Co(II) have syn-
thesized from 2-phenylamino-4,6-dichloro-s-triazine and 3,5-dimethyl pyrazole; their characteristics
have been investigated by means of elemental analyses, magnetic susceptibility, molar conductance,
IR, UV–Vis, Mass, NMR and ESR spectra. The electrochemical behavior of copper(II) complexes we have
studied, by using cyclic voltammetry. The ESR spectra of copper(II) complexes are recorded at 300 K
and 77 K and their salient features are appropriately reported. Spectral datas, we found, show that the
ligand acts as a neutral tridentate, and coordinates through the triazine ring nitrogen and pyrazolyl ring
nitrogen atoms to the metal ion. Evident from our findings, the metal(II) complexes of [ML] type exhibit
square pyramidal geometry, and that of [ML2]Cl2 exhibit octahedral geometry. The in vitro antimicrobial
activities of the ligand and its complexes are evaluated against Bacillus subtilis, Micrococcus luteus,
Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans, Escherichia coli, Enterobacter
aerogenes, Klebsiella pneumoniae, Proteus vulgaris, Cryptococcus neoformans, Pseudomonas aeruginosa,
Salmonella typhi, Serratia marcescens, Shigella flexneri, Vibrio cholera, Vibris parahaemolyticus, Aspergillus niger,
Candida albicans and Penicillium oxalicum by well-diffusion method. The second harmonic generation
efficiency of the ligand and its complexes are determined and compared with urea and KDP.
Ó 2014 Elsevier B.V. All rights reserved.
Keywords:
s-Triazine
3,5-Dimethyl pyrazole
Metal(II) complexes
NLO activity
Spectral and antimicrobial activity
Introduction
anti-malarial, anti-inflammatory and promising recently, anti-
cancer, anti-leukemia and anti-HIV activities [1–6]. Several triazine
S-triazine and its derivatives, quite known, come with a broad
spectrum of pharmacological advantages: anti-bacterial, anti-viral,
analogues are utilized as a building block for the construction of
multisite ligand systems [7,8]. Some pyrazolyl derivatives,
we learnt from our study, have attracted attention for their
applicability as potential ligands, and are reported to be friendly
⇑
Corresponding author.
http://dx.doi.org/10.1016/j.molstruc.2014.08.012
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

R. Shanmugakala et al. / Journal of Molecular Structure 1076 (2014) 606–613
607
with biological, pharmacological and analytical applications [9,10].
A number of triazine analogues examined for metal ion extraction
we have reviewed as well [11,12]. Some triazine derivatives with
pyrazole, functioning at the least conventional habiliments, are
screened and identified as potential inhibitors of photosynthetic
electron transport [13].
In recent years, quest to design and develop the non-linear
optical materials, have increased, to meet the current demand
due to their widespread advantage in many high-profile areas
such as high-speed information processing, optical communica-
tions and optical data storage. Researches, of late, suggest that
the criterion for the compound to exhibit NLO activity is non-
its complexes were determined by the modified version of powder
technique at IISc, Bangalore.
Synthesis of ligand (L)
2-Phenylamino-4,6-dichloro-s-triazine [19] (0.001 mol, 2.4 g)
in 20 ml of ethanol was added drop wise to an ethanolic solution
of 3,5-dimethyl pyrazole (0.002 mol, 2.12 g). The mixture was
refluxed on water bath for 4 h and the reaction was monitored
by TLC. The solution was allowed to stand at room temperature
and the solid obtained was washed with ethanol and recrystallized
from ethanol (Yield 75%) (Fig. 1).
centrosymmetric and D–p–A system. In addition to organic
materials, transition metal complexes have also been found to
be effective in this regard [14]. Taking into perspective of the
aforementioned advantages, spotlight is now on s-triazine’s
derivatives owing to their impeccable hyperpolarizabilities and
better transparency [15]. Besides, the easily polarizable aromatic
Synthesis of [ML] and [ML2]Cl2 type metal complexes: general
procedure
Hot ethanolic solution of ligand (0.001 mol/0.002 mol) and hot
ethanolic solution of the corresponding metal(II) chlorides
(0.001 mol) were added together with constant stirring. The
mixture was refluxed for 6 h at 70–80 °C. On cooling, characteristic
colored solid metal complexes of type [ML] and [ML2]Cl2 were
precipitated out. The precipitated metal complexes were filtered,
washed with cold ethanol and dried under vacuum. Purity of the
complexes was checked by TLC (Fig. 2).
p-system, another matchless feature of s-triazine is that due to
its -deficient nature, it can act as an auxiliary acceptor in NLO
p
chromophores [16]. Further advantages in considering the s-tri-
azine as central moiety is its symmetric nature by which it will
be possible to chemically tune its NLO nature by mono- or
di- substitution [17,18]. Hence s-triazine derivatives, we regard,
a first choice.
In order to promote the NLO response of s-triazine,3,5-dimethyl
pyrazole is introduced into triazine core. Hence the ligand 4,6-
bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-phenyl-1,3,5-triazin-2-amine,
we have synthesized by the condensation of 2-phenylamino-4,
6-dichloro-s-triazine and 3,5-dimethyl pyrazole reveals NLO prop-
erty and its pharmacological significance. This paper reports, the
spectroscopic characteristics of 4,6-bis(3,5-dimethyl-1H-pyrazol-
1-yl)-N-phenyl-1,3,5-triazin-2-amine chelated metal(II) complexes
and their NLO activity and biological screening.
Nonlinear optical property
The SHG efficiency of the ligand and its metal(II) complexes
were determined by the modified version of the powder
technique developed by Kurtz and Perry [20]. The samples were
ground into powder and packed between two transparent glass
slides. An Nd:YAG laser beam of wavelength 1064 nm was passed
through the sample cell. The transmitted fundamental wave was
absorbed by a copper(II) sulphate solution, which removes the
incident 1064 nm light and Filter BG-38 removing any residual
1064 nm light. Interference filter band width was 4 nm and for
central wavelength of 532 nm. Green light was finally detected
by the photomultiplier tube and displayed on the oscilloscope.
The second harmonic signal was detected by a photomultiplier
tube and displayed on a storage oscilloscope. The efficiency of
the sample was compared with microcrystalline powder of KDP
and urea. The input energy used in this particular set-up was
2.2 mJ/pulse.
Experimental
Materials and methods
Reagents such as Cyanuric chloride and various metal(II) chlo-
rides were of Merck products. Elemental analyses were performed
by the use of Perkin-Elmer CHN analyzer. The EI-mass spectra were
recorded on Jeol-GC MATE-2 Instrument. 1H NMR spectrum of the
ligand was recorded at 300 MHz on Bruker DRX-300 spectrometer
in DMSO-d6 by employing TMS as internal standard. IR spectra of
the samples were recorded on Jasco FT-IR spectrophotometer in
4000–400 cmꢁ1 range using KBr pellet. The UV–Vis spectra were
obtained on a Jasco V-530 spectrophotometer using DMSO as a sol-
vent. The ESR spectra of powder copper(II) complexes were
recorded with Varian, USA-E-112 ESR Spectrometer at 300 and
77 K by using DPPH (Diphenylpicrylhydrazyl) as the g-marker.
Magnetic susceptibility of the complexes was determined by MS1
Mark Guoy balance using copper sulphate as calibrant. Effective
Antibacterial and antifungal activity
The biological screening effects of the synthesized compounds
were evaluated by well diffusion method [21]. Bacillus subtilis,
Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermi-
dis, Streptococcus mutans, Escherichia coli, Enterobacter aerogenes,
Klebsiella pneumoniae, Proteus vulgaris, Cryptococcus neoformans,
Pseudomonas aeruginosa, Salmonella typhi, Serratia marcescens,
Shigella flexneri, Vibrio cholera, Vibris parahaemolyticus, were used
for bacterial test. Antifungal activity was evaluated against
Aspergillus niger, Candida albicans, Penicillium oxalicum and
Candida neoformans. All the bacterial strains mentioned above
were incubated in Nutrient Broth (NB) at 37 °C for 24 h and fungal
isolates were incubated in PDA broth at 28 °C for 2–3 days. The
wells each of 5 mm in diameter were made in Muller Hinton
magnetic moments were calculated using the formula
leff = 2.28
(v
MT)1/2, where vM is the corrected molar susceptibility. Cyclic
voltammetry measurements were carried out at room temperature
by model CH 608 C instrument in DMSO under nitrogen atmo-
sphere using three electrode cell containing a Ag/AgCl reference
electrode, platinum wire auxiliary electrode and a glassy carbon
working electrode with tetrabutylammonium perchlorate (TBAP)
as supporting electrolyte. The molar conductance of the complexes
was carried out using a Systronic conductivity bridge at room tem-
perature in DMSO. The antimicrobial activities of the ligand and its
metal complexes were carried out by well-diffusion method. The
SHG (Second Harmonic Generation) efficiency of the ligand and
agar using cork borer. The test solution was prepared in 10ꢁ3
concentration (DMSO) and then 100 of the solution was
transferred into each well. The plates were incubated for 24 h at
37 °C and examined for clear inhibition zone around the well.
The assay was carried out in duplicate for all the test organisms.
M
ll

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R. Shanmugakala et al. / Journal of Molecular Structure 1076 (2014) 606–613
Fig. 1. Synthesis of ligand.
spectrum of the ligand showed a peak at m/z 360 corresponding to
the molecular ion peak (Fig. 3). The molecular ion peak for the cobal-
t(II) complex (6), observed at m/z 849 confirms the stoichiometry of
metal complexes as [M(L)2]Cl2.
1H NMR spectra
The 1H NMR spectrum of the ligand recorded in DMSO (Fig. 4)
exhibits aromatic signals in the region 6.77–7.76 ppm correspond-
ing to the phenyl ring system and the singlet at 6.05 ppm,
7.92 ppm corresponding to AC@CHA proton of pyrazolyl ring
and ANH proton respectively and the singlet at 2.11 ppm and
2.69 ppm attributed to ACH3 protons.
Fig. 2. Structure of metal complex.
Infrared spectra
In order to study the binding mode of the ligand to the metal in
complexes, the IR spectrum of the free ligand was compared with
the spectra of the metal(II) complexes (Table 2). The IR spectrum of
the ligand (Fig. 5) shows a strong band at 1437 cmꢁ1 assigned to
Results and discussion
The analytical data and physical properties of ligand and meta-
l(II) complexes are in good agreement with calculated values and
are summarized in Table 1. The molar conductance measurement
implies that the complexes of [ML] type are non-electrolytes [22]
and of [ML2] type are 1:2 electrolytes [13]. Thus, the complexes
of [ML] and [ML2] type may be formulated as [MLCl2] and [ML2]Cl2
respectively, where M = Cu(II), Ni(II), Co(II).
m
(C@N) group of triazine [23]. This band is shifted to lower
frequency in the spectra of all the complexes (1429–1419 cmꢁ1
)
indicates the coordination of triazine ring nitrogen to the metal
[24]. The band observed at 1597 cmꢁ1 in the ligand is assigned to
m
(C@N) of pyrazolyl ring is shifted to lower frequency
(1592–1567 cmꢁ1) upon complexation, suggesting the coordina-
tion of pyrazolyl nitrogen to the metal center [25]. Moreover, the
m
(NAN) of the pyrazolyl ring obtained at 1033 cmꢁ1 is shifted to
Mass spectra
higher frequencies in the case of complexes. This shift in frequency
may be due to the reduction of lone pair lone pair repulsive forces
in the adjacent nitrogen atoms upon complexation [26].
Assignments of the proposed coordination sites is further
supported by the appearance of medium bands in metal complexes
The purity of the ligand and metal complexes are confirmed
using electron impact mass spectrometry. The mass spectrum of
the ligand was compared with the cobalt(II) complex (6) to
obtain the stoichiometry composition of metal chelate. The mass
at 429–454 cmꢁ1 which could be attributed to
m(MAN) [27].

R. Shanmugakala et al. / Journal of Molecular Structure 1076 (2014) 606–613
609
Table 1
Analytical data and physical characterization of ligand and its metal(II) complexes.
Compound
m.p (°C)
Yield%
km
X
ꢁ1 cm2 molꢁ1
Experimental analysis found (Calc.)
%C
%H
%N
%M
-
12.82 (12.87)
12.52 (12.55)
12.20 (12.26)
7.42 (7.44)
C
19H20N8 (L)
220
87
81
80
83
84
80
82
–
63.30 (63.33)
46.44 (46.41)
46.66 (46.62)
46.59 (46.53)
53.51 (53.52)
53.53 (53.52)
53.64 (53.67)
5.54 (5.55)
4.02 (4.05)
4.06 (4.08)
4.06 (4.08)
4.64 (4.68)
4.65 (4.69)
4.76 (4.70)
31.14 (31.11)
22.67 (22.69)
22.89 (22.86)
22.94 (22.90)
26.27 (26.24)
26.27 (26.29)
26.39 (26.36)
[Cu(L)Cl2] (1)
[Ni(L)Cl2] (2)
[Co(L)Cl2] (3)
[Cu(L)2]Cl2 (4)
[Ni(L)2]Cl2 (5)
[Co(L)2]Cl2 (6)
>360
>360
>360
>360
>360
>360
15
17
19
95
87
93
7.25 (7.21)
6.96 (6.94)
Fig. 3. Mass spectrum of ligand.
Fig. 4. NMR spectrum of ligand.

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R. Shanmugakala et al. / Journal of Molecular Structure 1076 (2014) 606–613
Table 2
IR spectral data of ligand and its metal(II) complexes .
Compound
IR spectra (cmꢁ1
(CH@N) of pyrazole
)
m
m
(NAN)
m
(CH@N) of triazine
m
(NAH)
m
(MAN)
Ligand
(1)
(2)
(3)
(4)
1597
1583
1582
1567
1575
1584
1592
1033
1050
1047
1038
1047
1027
1052
1437
1422
1420
1425
1419
1426
1429
3137
3183
3192
3205
3203
3172
3187
–
429
432
441
454
437
448
(5)
(6)
Fig. 5. IR spectrum of ligand.
Electronic absorption spectra and magnetic moment
complex (2) appeared at 10,373, 18,227, 23,364 cmꢁ1 due to
3B1(F) ? 3E(F), 3B1(F) ? 3A2(P), 3B1(F) ? 3E(P) transitions indicates
square pyramidal geometry [30,31]. Co(II) complex (3) displays
three absorption bands at 10,881, 17,847, 20,008 cmꢁ1 which are
assigned to (4A2 + 4E ? 4B1, 4A2 + 4E ? 4E(P), 4A2 + 4E ? 4A2(P))
transitions arises from square pyramidal geometry [32]. Co(II)
and Ni(II) complexes have magnetic moment values 4.90 and
3.02 B.M. respectively, confirms square pyramidal geometry
[33,34].
The electronic absorption spectral data of the ligand and its
metal(II) complexes are given in Table 3. The ligand shows an
absorption band at 26,007 cmꢁ1 which is due to intra-ligand
charge transfer transition. The copper(II) complex (1) shows three
absorption bands at 11,006, 14,920, 17,006 cmꢁ1 assignable to
(2B1 ? 2A1, 2B1 ? 2B2, 2B1 ? 2E) transitions are characteristic of
square pyramidal geometry [28]. The magnetic moment of (1) is
found to be 1.99 B.M. suggestive of a five coordinate square
pyramidal geometry [29]. The absorption bands for the nickel(II)
In the electronic absorption spectrum of copper(II) complex (4),
the observed d–d transition at 11,876 cmꢁ1 due to (2Eg ? 2T2g
)
Table 3
Magnetic moment and electronic spectral data of metal(II) complexes.
Complex
kmax (cmꢁ1
)
Transition
Geometry
leff (B.M.)
(1)
11,006
14,920
17,006
2B1
2B1
2B1
?
?
?
2A1
2B2
2E
Square pyramidal
1.99
(2)
(3)
10,373
18,227
23,364
3B1 (F) ? 3E (F)
3B1(F) ? 3A2(P)
3B1 (F) ? 3E (P)
Square pyramidal
3.02
10,881
17,847
20,008
4A2
4A2
4A2
+
+
+
4E ? 4B1
4E ? 4E(P)
4E ? 4A2(P)
Square pyramidal
4.90
1.84
(4)
(5)
11,876
19,407
2Eg
?
2T2g
Distorted Octahedral
INCT
9727
13,440
24,096
3A2g(F) ? 3T2g(F)
3A2g(F) ? 3T1g(F)
3A2g(F) ? 3T1g(P)
4T1g(F) ? 4T2g(F)
4T1g(F) ? 4A2g(F)
4T1g(F) ? 4T1g(P)
Distorted Octahedral
Distorted Octahedral
2.94
4.71
(6)
9569
16,260
21,413

R. Shanmugakala et al. / Journal of Molecular Structure 1076 (2014) 606–613
611
The observed spectral parameter for copper(II) complex (4)
A||(156.8) > A\(58.8) and g||(2.28) > g\(2.10) indicates that the
complex exerts an octahedral geometry [40]. The observed value
of G for the copper(II) complex (G = 2.84) implies that the exchange
coupling is present and misalignment is appreciable. The giso value
less than 2.3 indicates the covalent character of the metal ligand
bond and the a2 value (0.795) suggestive of in-plane covalency.
The calculated value of g||/A|| (145 cm) for the complex is consistent
with slightly distorted structure. The orbital reduction factors
K|| and K\ were estimated from the expression, K|| = (g||ꢁ2.0023)
D
E/8k, K\ = (g\ꢁ2.0023)
D
E/8k, k = ꢁ828 cmꢁ1 (spin–orbit
coupling constant for the free ion) and K|| (0.49) > K\ (0.17) shows
poor in plane g-bonding.
Redox studies
Fig. 6. ESR spectrum of (4).
The redox behavior of Cu(II) complexes (1) and (4) has been
studied through cyclic voltammetry in DMSO (Fig. 7). The cop-
per(II) complex (1) shows a well-defined redox process corre-
sponding to the formation of Cu(II)/Cu(I) couple at Epa = 0.380 V
transition which favors the splitting of 2Eg level by Jahn–Teller dis-
tortion in octahedral geometry and the same is further confirmed
by its magnetic moment value (1.84 B.M.) [35]. The nickel(II) com-
plex (5) exhibits three d–d bands at 9727, 13,440, 24,096 cmꢁ1
and Epc = 0.187 V. This couple is quasireversible with
DEp = 0.183 V
and the ratio of cathodic to anodic peak currents (Ipc/Ipa ꢂ 1)
corresponding to a simple one-electron process [41]. The cyclic
voltammogram of (4) has cathodic reduction peak at Epc =
ꢁ0.086 V and anodic oxidation peak at Epa = 0.284 V. The mea-
3
3
assigned to (3A2g(F) ? 3T2g(F), A2g(F) ? 3T1g(F), A2g(F) ? 3T1g(P))
transitions which strongly favors an octahedral geometry around
metal ion and the magnetic moment value 2.94 B.M. obtained is
the normal range of octahedral symmetry [36]. The electronic
absorption spectrum of cobalt(II) complex (6) gives absorption
sured
DEp value (0.370 V) clearly indicates that the redox couple
is quasi reversible in nature and the ratio of cathodic to anodic
peak currents Ipc/Ipa corresponds to one electron transfer process.
bands at 9569, 16,260, 21,413 cmꢁ1 due to (4T1g(F) ? 4T2g(F), T1g
4
(F) ? 4A2g(F), and T1g(F) ? 4T1g(P)) transitions suggestive of octa-
4
Nonlinear optical property
hedral geometry which is also supported by its magnetic moment
value (4.71 B.M.) [37].
SHG efficiency measurements reveal that the ligand is 3.5 times
more active than that of urea and 4.3 times more active than KDP
(Table 5). Metal(II) complexes show SHG intensity as high as 4.5–
6.7 times as that of urea and 5.1–7.2 times than that of KDP. From
the results obtained, we may conclude that metal(II) complexes
exhibit better SHG efficiency than the ligand. Obviously, the sym-
metric ligand is proved to be a larger g-conjugate system and an
effective SHG chromophore [42,43]. Hence the D–g–A structure
and thermal stability of the ligand favors the large second order
polarisability and makes such kind of structure a promising strat-
egy for the second order NLO material.
ESR spectra
The ESR spectra of copper(II) complexes (1) and (4) in solid state
(Fig. 6) were recorded at 300 and 77 K and the observed spin Ham-
iltonian parameters are given in Table 4. The ESR spectrum of Cu(II)
complex (1) shows g||(2.18) > g\(2.07) value is characteristic of an
axially elongated square pyramidal geometry [38]. The covalent
character of metal–ligand bond is inferred from the giso value
2.14, which support the fact that the unpaired electrons lies in
dx2–y2 orbital. The calculated magnetic moment for the copper(II)
complex (1.83 B.M) as per the relation
l
2 = 3/4 g2 is indicative of
Biological activity
an unpaired electron. The poor in-plane g-bonding in the complex
is reflected in their b2 values. The molecular orbital coefficients a2
b2 were calculated using the following equations.
,
The ligand and its metal(II) complexes were evaluated for
antibacterial activity against five Gram positive bacteria, ten Gram
negative bacteria and four fungi by using well diffusion method and
the results were presented in Tables 6a–c. Amikacin and ketokonaz-
ole were used as references for antibacterial and antifungal studies.
Antimicrobial studies were performed in triplicate and the average
was taken as the final reading. Error limits are indicated in the
respective table. In vitro antifungal activity data of the ligand and
its metal(II) complexes against fungal organisms display significant
activity with a wide degree of variation. It is found that all the
derived compounds exhibit higher activity against C. albicans and
C. neoformans and significant activity against P. oxalicum than the
standard. Ni(II) complex (5) exhibits significant activity against
a2 ¼ A =P þ ðg ꢁ 2:0023Þ þ 3=7ðg? ꢁ 2:0023Þ þ 0:04
k
k
b2 ¼ ðgk ꢁ 2:0023ÞE=ðꢁ8ka2
Þ
The calculated value of (g||/A||) 177 cm for the complex is character-
istic of distorted structure [39]. The geometric parameter G is
estimated from the expression
G ¼ ðgk ꢁ 2:0023Þ=ðg? ꢁ 2:0023Þ
The observed value of G for (1) is 2.3, suggesting an exchange
coupling is present and misalignment is appreciable.
Table 4
ESR spectral parameters of Cu(II) complexes.
Complex
g||
g\
A|| ꢃ 10ꢁ4 cmꢁ1
A\ ꢃ 10ꢁ4 cmꢁ1
a2
b2
g||/A||cm
K||
K\
(1)
(4)
2.18
2.28
2.07
2.1
123.5
156.8
50.6
58.8
0.59
0.79
0.77
1.31
177
145
0.29
0.49
0.11
0.17

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R. Shanmugakala et al. / Journal of Molecular Structure 1076 (2014) 606–613
Table 6c
Antifungal activity data of the ligand and its metal(II) complexes.
Compounds
Zone of inhibition (in mm)a
C. albicans
C. neoformans
A. niger
P. oxalicum
Ligand
20
22
24
26
21
24
21
20
16
18
19
18
16
18
17
17
10
13
12
11
14
16
11
12
15
17
14
15
16
16
12
18
[Cu(L)Cl2] (1)
[Ni(L)Cl2] (2)
[Co(L)Cl2] (3)
[Cu(L)2]Cl2 (4)
[Ni(L)2]Cl2 (5)
[Co(L)2]Cl2 (6)
Ketokonazole
a
The test was done using 10ꢁ3 M concentration of synthesized compounds by
well diffusion technique. The values are mean of three replications.
S. aureus and B. subtilis respectively. All the derived compounds
display least activity against S. typhi. E. Coli was found to be more
susceptible than rest of the other strains of bacteria, among them
(3) and (6) showing significant activity. Compound (6) exhibits
higher activity against V. cholera compared to standard reference
and all other compounds have exhibited significant to moderate
activity. Such increased activity of the metal(II) complexes over
the ligand can be explained on the basis of Overton’s concept [44]
and chelation theory [45,46]. The variation in the activity of
different metal complexes against different microorganisms
depends on either the impermeability of the cells of the microbes
or the differences in ribosomes in microbial cells.
Fig. 7. Cyclic voltammogram of (1).
Table 5
Nonlinear optical data of ligand and metal complexes.
Compound
Urea
KDP
Ligand
(1)
(2)
(3)
(4)
3.5
4.3
5.2
4.7
3.9
3.7
4.8
4.3
4.9
6.7
5.1
4.6
4.5
5.3
(5)
(6)
Conclusions
Table 6a
Antibacterial activity data against gram positive organisms.
Novel triazine based pyrazolyl ligand, 2,4-bis(3,5-dimethyl-1H-
pyrazol-1-yl)-N-phenyl-1,3,5-triazin-6-amine L and its transition
metal complexes of [MLCl2] and [ML2]Cl2 types have been synthe-
sized and characterized by spectral and analytical techniques.
Based on the analytical and spectral data, it is concluded that the
ligand act as tridentate forming octahedral geometry with metal
ions in case of [ML2]Cl2 type and square pyramidal geometry in
[MLCl2] type metal(II) complexes. The electrochemical properties
of the copper(II) complexes investigated in DMSO shows the most
significant feature is the Cu(II)/Cu(I) couple. The ligand and its
metal(II) complexes are found to exhibit considerable nonlinear
optical properties in comparison with urea and KDP. Most of the
metal(II) complexes show better antimicrobial activity than the
free ligand. It is suggested that chelation of ligand with different
metal ions make them stronger bacteriostatic agents, thus
inhibiting the growth of bacteria and fungi more than the parent
ligand. Therefore, they seem to be really promising compounds
for their antimicrobial activities.
Compounds
Zone of inhibition (in mm)a
B. subtilis S. aureus S. epidermidis S. mutans M. luteus
Ligand
11
12
14
R
10
13
R
11
13
10
12
16
11
10
15
12
12
13
14
22
14
16
12
15
15
12
15
28
14
12
16
14
16
16
15
22
[Cu(L)Cl2] (1)
[Ni(L)Cl2] (2)
[Co(L)Cl2] (3)
[Cu(L)2]Cl2 (4) 13
[Ni(L)2]Cl2 (5) 14
[Co(L)2]Cl2 (6) 16
Amikacin
18
a
The test was done using 10ꢁ3 M concentration of synthesized compounds by
well diffusion technique. The values are mean of three replications.
A. niger and whereas all other compounds achieved substantial
activity against the same species.In vitro antibacterial activity data
reveals that all the newly synthesized compounds display moderate
to significant activity in comparison to standard. It is found that
cobalt (II) complex (6) shows significant activity against B. subtilis
when compared to other complexes. Metal complexes (3), (4) and
(6) are equipotent against S. mutans and (2), (4) and (5) are
equipotent against M. luteus and the rest of the compounds exhibit
substantial activity. Complexes (2) and (3) are inactive towards
Acknowledgements
Authors thank the Management of Thiagarajar College, Madurai
and one of the authors (PT) thanks the Defence Research and
Table 6b
Antibacterial activity data against gram negative organisms.
Compounds
Zone of inhibition (in mm)a
E. aerogenes
E. coli
K. pneumonia
P. vulgaris
P. aeruginosa
V. cholerae
V. parahaemoly
S. flexneriticus
S. marcescens
S. typhi
Ligand
13
14
17
R
13
R
14
13
16
19
14
13
18
20
R
8
8
7
7
8
9
15
9
10
8
9
11
9
14
13
11
12
11
12
12
16
10
11
11
11
12
14
16
12
11
14
12
18
15
17
13
22
12
15
12
14
18
13
17
18
13
10
16
13
11
12
13
17
R
7
7
7
6
R
8
14
[Cu(L)Cl2] (1)
[Ni(L)Cl2] (2)
[Co(L)Cl2] (3)
[Cu(L)2]Cl2 (4)
[Ni(L)2]Cl2 (5)
[Co(L)2]Cl2 (6)
Amikacin
13
22
11
10
a
The test was done using 10ꢁ3 M concentration of synthesized compounds by well diffusion technique. The values are mean of three replications.

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