7
8
L. Guofa et al./Journal of Molecular Structure 412 (1997) 75–81
Table 2
Infrared frequencies, activity and assignment for the NO
−
3
ion
−1
Type
Activity
Frequencies (cm
)
Assignment
AЈ
AЉ
EЈ
EЈ
1
2
ia
a
a
n
n
n
n
1
2
3
4
ca. 1050
ca. 831
ca. 1390
ca. 720
N–O stretching
NO
NO
2
deformation
antisymmetric stretch
2
a
2
ONO planar rocking
a = active ia = inactive
−
1
is in the range 1641–1643 cm . This band is shifted
to higher wavenumbers in the complexes. It shows
that the nitrogen of the azomethine group is coordi-
nated to the rare earth ion. The phenolic OH stretching
D , are listed in Table 2 with the vibration types,
3h
activity and assignments. Its infrared spectrum
shows four absorption bands, where three (n , n and
2
3
n ) are active, one (n ) normally is inactive, but some-
4
1
−1
vibration frequency of the Schiff base in at 3443 cm .
In the complexes this band is in the range 3394–3419
cm . The absorption band shifted to the lower fre-
quencies, indicating that oxygen of the phenolic OH is
coordinated to the rare earth ion. The absorption
times becomes weakly active through crystal field
interactions. n (EЈ) and n (EЈ) are doubly degenerate.
3
4
−1
In the complexes the nitrate ion acts as a monodentate
or bidentate coordination, and they both belong to the
point group C . Their vibration types and properties
2
v
−1
bands, near 477 and 496 cm , are due to symmetrical
and antisymmetrical stretching vibrations of M–O
are listed in Table 3. Under C2v symmetry the n (AЈ )
1 1
[10]. There are two M–O bands, since the nitrate
group is coordinated in a bidentate fashion [11].
The yC–O stretching vibration of phenol and phe-
nolic OH deformation in-plane are all shifted to the
lower frequencies, since the phenolic OH is coordi-
nated to rare earth ion (Table 1) [12]. The CyC
stretching vibration of aryl ring, the C–H out-of-
plane bend vibration of naphthalene and the yC–O–
C antisymmetric stretching vibration of aryl ether do
not basically change [12,13]. The bands in the range
mode becomes active n (A ) mode and the E(n , n )
2
1
3
4
mode splits into A (n , n ) and B (n , n ) components,
1
1
3
1
4
5
so that the spectrum now ideally have six bands,
all being active in the infrared spectrum. Under C2v
symmetry, three of the modes belong to the totally
symmetric irreducible representation 3A , and remain
1
−1
2
834–2984 cm are assigned to C–H stretching
three are no totally symmetric (2B + B ). The band
1
2
mode of methoxy group, therefore, in the range
splittings for the bidentate coordination are larger in
magnitude than those for monodentate coordination.
The n and n , n and n absorption bands in Table 3
−1
3005–3094 cm to aryl group.
The n –n absorption bands in Table 1 are due to
1
6
1
4
3
5
the coordinated nitrate group. The infrared absorption
are splitting bands. The magnitude of n − n for the
4 1
bidentate mode is in general more than 180 cm and
−
−1
frequencies for NO , which belongs to the point group
3
Table 3
Infrared frequencies, activity and assignment for the coordination nitrate group
−1
Type
Activity
Frequencies (cm
)
Assignment
A
A
A
B
B
B
1
1
1
2
1
1
a
a
a
a
a
a
n
n
n
n
n
n
3
1
2
6
4
5
ca. 753
ca. 1306
ca. 1035
ca. 792
ca. 1520
ca. 717
NO
NO
2
2
bending
symmetric stretch
N–O stretch
ONO nonplanar rocking
NO antisymmetric stretch
ONO planar rocking
2
2
2
Guofa, Liu
