O.A.M. Ali et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 651–660
655
ether, and methylene chloride but are readily soluble in DMF and
Table 5
Fluorescence data of ligand and its complexes.
DMSO. The analytical data along with some physical properties
of Schiff base ligand and its complexes are summarized in Table 1.
The results obtained are in good agreement with those calculated
for the suggested formula.
Compound
kExcitation
Fluorescence emission band (nm)
L
310
294
294
374
295
302
298
308
294
347
347
347
No emission
346
346
348
349
355
[Cu(L)(Cl) ]H O
2
2
[
[
[
[
[
[
Ni(L)(Cl)
Fe(L)(Cl)
Co(L)(Cl)
2
]2H
O]H
(H O)
Zn(L)(AcO) ]H
Hg(L)(AcO) ]H
La(L)(NO ]NO
2
O
3
H
2
2
O
2
2
2 2
]2H O
2
2
O
IR spectra and mode of bonding
2
2
O
3
)
2
3
H
2
O
The IR spectra provide valuable information regarding the nat-
ure of functional groups attached to the metal atom. The main
infrared spectral bands of the ligand and its metal complexes are
[Sm(L) ](ClO ) ꢁH O
3
4
3
2
presented in Table 2. The IR spectrum of Schiff base (L) (Fig. 1)
1H NMR spectra
ꢂ1
was displayed a band at 1603 cm assigned to
m(C@N) [30]. On
complexation, this band was shifted to the frequency range
1
The H NMR spectrum of the free ligand (L) (Fig. 2) exhibited a
ꢂ1
1
644–1599 cm indicating the participation of the azomethine
2
broad single signal at 12.94 ppm corresponded to NH proton [44].
The signal observed at 8.32 ppm was referred to azomethine pro-
ton, AN@C(H)A, while the multiple signals appeared in the region
.29–7.99 ppm were assigned to the chemical shifts for hydrogen
of the aromatic and furan species. The H NMR spectra of Ni(II),
Zn(II), Hg(II) and La(III) complexes in DMSO showed signals indi-
cating their diamagnetic properties. The chemical shifts of the dif-
group in coordination to the metal ions through the lone pair of
electrons on the nitrogen (Table 2). The two bands at 3315 and
ꢂ1
3
282 cm in Schiff base ligand is due to the asymmetric and sym-
6
metric vibrations of
complexes exhibited
assigned to
m
(NH
a
2
), respectively, [31]. The IR spectra of the
broad band around 3418–3171 cm
1
ꢂ1
m
(OH) of crystalline and/or coordinated water mole-
cules associated with the complex. This band may be overlapped
with the bands corresponding to the stretching vibrations of
1
ferent types of protons in the H NMR spectra of the L ligand and its
complexes are listed in Table 3. The complexes displayed broad
signals corresponding to NH proton of L, probably due to some
types of inter- and intra-hydrogen bonding with oxygen [45]. The
exchange rate of hydrogen between oxygen and nitrogen atoms
could be very fast leading to the collapse of the signal as shown
for zinc and nickel complexes. The H NMR spectra of mercuric
and lanthanum complexes displayed a broad signal due to NH pro-
ton without shift with respect to that of the ligand confirming the
non-bonding of NH nitrogen to metal. The azomethine proton of
2
the reported complexes showed singlets at 7.85–8.14 ppm with
up field shift with respect to that of the ligand indicating the coor-
dination of azomethine nitrogen to the metals [46,47]. The H NMR
spectra of the complexes exhibited signals corresponded to phenyl
and furan moieties with the proper shifts.
m
NH
2
group. Upon complex formation, the band due to
m
(CAOAC)
ꢂ1
stretching vibration of furan moiety at 1240 cm was shifted to
1
ꢂ1
258–1235 cm suggesting the coordination of ligand to metal
through furan oxygen atom [32–34]. Non ligand bands appeared
ꢂ1
in the spectra of complexes in the ranges of 479–444 cm and
1
ꢂ1
5
46–464 cm
corresponding to mMAN and mMAO vibrations,
respectively [35]. In Zn(II) and Hg(II) complexes, the chelating
ꢂ
bidentate CH
3
COO group was supported by bands located at
ꢂ1
1
509–1496 and 1448–1405 cm . These two bands are due to
m
as(-
ꢂ
ꢂ
COO ) and
m
s
(COO ), respectively. The separation of the two bands,
ꢂ1
D
m
=
m
as
–m
s
= 61–91 cm is comparable to the values cited for the
1
bidentate character of the acetate group [36]. La(III) complex
showed four bands at 1461(
m
1
), 1145 (
m
2
), 814(
m
3
) and 1331(
m
4
4
)
)
ꢂ1
cm . The separation of the two highest frequency bands (
m
1
–m
ꢂ1
ꢂ
is approximately 130 cm and accordingly the coordinated NO
3
EPR study
ion in the complex is a bidentate ligand [37–40]. In addition, the
ꢂ1
band at 1384 cm in the spectrum of the La(III) complex indicates
X-band ESR spectrum of Cu(II) complex (Fig. 3) was recorded in
the solid state at 25 °C. The spectrum of the complex exhibits one
broad band with g = 1.97. The shape of the spectrum is consistent
with the square-planar geometry [48].
the existence of free nitrate group [41]. In Sm(III) complex, the
ꢂ1
strong band at 1102 cm
assigned to m(ClAO) indicating the
ꢂ
non-coordinated (ionic) nature of the ClO
ure is further supported by the appearance of a band at 623 cm
43].
4
ion [42]. The ionic nat-
ꢂ1
[
Mass spectra analysis
Mass spectrometry as a powerful structural characterization
technique in coordination chemistry has been successfully used
to confirm the molecular ion peaks of L Schiff base and its com-
plexes. The mass spectrum of the ligand showed a molecular ion
peak at m/z = 186 corresponding to its molecular weight,
+
[
C
11
H
10
N
2
O] , (Fig. 4). This peak confirms the purity of the ligand,
L. Mass spectra of Cu(II), Ni(II), Zn(II) and La(III) complexes have
also been recorded (Fig. 5). The most prominent mass spectral
peaks of the reported complexes are given in Table 4.
Molar conductivity measurements
The Molar conductance of metal complexes are measured using
ꢂ3
1
0
M DMF solvent, the obtained values (Table 1) suggested the
presence of a non-electrolytic nature except La(III) and Sm(III)
complexes. The electrical conductance value of La(III) complex is
87 ohm mol cm indicating 1:1 electrolyte [49]. Sm(III) chelate
Fig. 6. Emission spectra of: (1) [Sm(L)
O; (4) [La(L)(NO ] NO O; (5) [Zn(L)(AcO)
7) [Ni(L)(Cl) ]2H O (8) [Cu(L)(Cl) O.
]ꢁH
3
](ClO
4
)
3
H
2
O; (2) Ligand; (3) [Hg(L)(AcO)
2
]-
O;
H
(
2
3
)
2
3
H
2
2
]H O; (6) [Co(L)(Cl) (H O) ]2H
2
2
2
2
2
ꢂ1
ꢂ1
2
2
2
2
2