C. Anitha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 98 (2012) 35–42
39
Table 3
EPR spectral parameters of VO(II) and copper(II) complexes.
Compound
g
g\
giso
a2
b2
A
(10ꢁ4 cmꢁ1
)
A\ (10ꢁ4 cmꢁ1
)
Aiso (10ꢁ4 cmꢁ1
)
g /A (cm)
K
k
K\
l (B.M.)
k
k
k
k
[VOL2]SO4
[CuL2ꢀCl2]
1.92
2.23
1.96
2.10
1.94
2.14
1.02
0.82
1.09
0.36
164
185
55
30
91.33
81.86
117
120
1.07
0.72
1.03
0.44
1.76
1.81
base suggesting the coordination of the azomethine nitrogen to
Zn(II) ion.
Mass spectra
The mass spectra of the ligand (CDHBPC) and its complexes are
recorded. The molecular ion peak for the Schiff base was observed
at 508 m/z. which are in good agreement with the suggested
molecular formula indicated from elemental analyses. The molec-
ular ion peak of Cu(II) complex was observed at 1149 m/z, which
confirm the stoichiometry of the metal complexes to be [ML2Cl2]
(Supplementary material, Figs. S1 and S2).
Electronic spectra and magnetic moment
The electronic spectra were recorded in DMSO and the Cu(II)
complex shows absorption at 13,698, 15,250 and 24,325 cmꢁ1
,
which may be assigned to 2B1g ? 2A1g (dx2ꢁy2 ? dz2
2B1g ? 2B2g, (dx2ꢁy2 ? dzy) ( 2), 2B1g ? 2Eg (dx2ꢁy2 ? dzy, dyz) (m3
transitions and the magnetic susceptibility value (1.93 B) con-
) (m1),
Fig. 5. EPR spectrum of [C58H42Cl2N8O11SV] at 300 K in DMSO.
m
)
l
firms the octahedral geometry [26]. The bands at 9407, 16,625
4
4
and 18,241 cmꢁ1 assigned to T1g(F) ? 4T2g(F) [
m
1], T1g(F) ? 4A2g
Table 4
4
2] and T1g(F) ? 4T2g(P) [
m
3] transitions indicates octahedral
Antimicrobial activity of the azo Schiff base ligand and its metal (II) complexes.
(F) [m
Compound Diameter of the inhibition zone (in mm)a against
geometry of the Co(II) complex and the magnetic moment value
4.86 B.M confirms the same [27]. The magnetic moment value
3.26 B.M. for Ni(II) complex as well as the electronic spectrum
S. aureus E. coli S. enterica typhi B. subtilis Candida albicans
Standard
CDHBPC
[VOL2]SO4 15
[CoL2Cl2]
[NiL2Cl2]
[CuL2Cl2]
[ZnL2Cl2]
7
7
5
7
10
11
8
5
9
18
9
5
7
11
9
25
21
13
24
3
centered around 9690, 16332 and 23,750 cmꢁ1 assigned to A2g
10
13
R
3
3
(F) ? 3T2g(F) [ 1], A2g(F) ? 3T1g(F) [ 2] and A2g(F) ? 3T1g(P) [m3
m m ]
R
transitions, confirm octahedral geometry around the Ni(II) ion.
The octahedral geometry of Co(II) and Ni(II) complexes is further
supported by the ratio m2/m1 which lies around 1.7 and 1.6 [28].
18
19
20
16
21
20
R
19
17
23
17
The absorption spectrum of vanadyl complex shows absorption
at 12,554, 17,452 and 24,180 cmꢁ1 due to 2B2 ? 2E1, 2B2 ? 2B1,
2B2 ? 2A1 transitions, indicating the square pyramidal geometry
and the same is further confirmed from its magnetic moment
1.79 B.M. [29]. The Zn(II) complex is diamagnetic and an
octahedral geometry for Zn(II) [30].
a
All values are the mean (n = 3) with a standard deviation of <3%; R = Resistant.
Standard = (ciprofloxacin and cephalosporin).
complexes did not show any frequency shift of the –N@N– band,
which may be explained by non-participation in complex forma-
tion [24]. The proof of N and O coordination is demonstrated by
bands in the spectra of complexes in the regions 570–592 cmꢁ1
EPR spectra
and 408–422 cmꢁ1 assigned to
m(M–N) and m(M–O) modes, respec-
The EPR spectrum of the Cu(II) complex was recorded in DMSO
at 300 and 77 K (Fig. 4) and the spin Hamiltonian parameters cal-
culated are given in Table 3. The observed spectral parameters
tively. The IR spectra of the metal complex show bands in the re-
gion 360–383 cmꢁ1 assigned to M–Cl bond formation [25]. In the
vanadyl complex, a new band appears at 943 cmꢁ1 is attributed
to V = O frequency [26].
show g (2.23) > g\ (2.10) > ge (2.0023) which is the characteristic
k
of an octahedral geometry [31] The observed value for the ex-
change interaction parameter for the Cu(II) complex (G = 2.3) sug-
gests that the significant exchange coupling is present and the
misalignment is appreciable. The observed value of a2 (0.82) of
the complex is less than unity, which indicates the covalent char-
acter [32]. The magnetic moment of the copper (II) complex is
found to be 1.81 B.M. indicative of an unpaired electron. The orbital
reduction factors K and K\ estimated from the expression, K =
1H NMR spectra
The 1H NMR spectrum of ligand recorded in DMSO has the fol-
lowing signals confirming the structure of the ligand: 10.3 ppm (H,
s, OH); 8.3 ppm (H, s, –HCa@N-azomethine proton); 8.8 ppm (H, s,
–HCb@N-azomethine proton); 6.17–7.90 (m, aromatic protons);
The 1H NMR spectrum of zinc(II) complex in DMSO shows the pres-
ence of OH proton signal indicating the non involvement of the hy-
droxyl group in complexation to the metal. However, the
resonance signals obtained for azomethine proton (–HCa@N–)
shifted to downfield as compared to the proton NMR of azo Schiff
k
k
(g ꢁ2.0023)
D
E/8k, K\ = (g\ ꢁ2.0023)
D
E/2k, k = ꢁ828 cmꢁ1
k
(spin–orbit coupling constant for the free ion). In case of a pure
r
bonding K ffi K\ 0.77 whereas K < K\ implies considerable
k
k
in-plane
p
-bonding while for out of p bonding K > K\. For this
k
complex, K > K\ indicating poor in-plane
p
-bonding which is also
k
reflected in b2 values. For oxovanadium complex the calculated