Spectroscopic and magnetic investigations of some transition metal complexes with N-4-methoxyphenyl-N-4-chlorobenzoyl hydrazide as ligand

Article abstract of DOI:10.1016/S0022-2860(98)00930-2

The preparation, spectroscopic and magnetic properties of ML₂Cl₂ (M = Cu(II), Mn(II), Ni(II)) and [ML₃]Cl₃ (M = Fe(III), Cr(III)), L = N-4- methoxyphenyl-N-4-chlorobenzoyl hydrazide are reported. In all the studied complexes the N-4-methoxyphenyl-N-4-chlorobenzoyl hydrazide acts as a neutral bidentate chelating ligand with coordination involving the carbonyl oxygen and nitrogen atom of the secondary hydrazide group. The complexes appear to have an pseudo-octahedral stereochemistry. ESR parameters (g₁ = 4.432, g₂ = 1.991, D = 0.096 cm^-1) and μ(elf) = 3.55 μ(B) obtained for [CrL₃]Cl₃ also suggest the possibilities of magnetic dipole-dipole coupling interactions between Cr(III) ions.

Full text of DOI:10.1016/S0022-2860(98)00930-2

MOLSTR 10785
Journal of Molecular Structure 482–483 (1999) 149–152
Spectroscopic and magnetic investigations of some transition metal
complexes with N-4-methoxyphenyl-N-4-chlorobenzoyl hydrazide
as ligand
a,
b
a
c
a
a
*
L. David , M. Rusu , O. Cozar , D. Rusu , M. Todica , C. Balan
a‘‘Babes-Bolyai’’ University, Department of Physics, 1 Kogalniceanu, 3400 Cluj-Napoca, Romania
b‘‘Babes-Bolyai’’ University, Deptartment of Chemistry, 3400 Cluj-Napoca, Romania
cMedical and Pharmaceutical University, Department of Chem.-Phys., 3400 Cluj-Napoca, Romania
Received 24 August 1998; received in revised form 30 November 1998; accepted 4 December 1998
Abstract
The preparation, spectroscopic and magnetic properties of ML2Cl2 (M ˆ Cu(II), Mn(II), Ni(II)) and [ML3]Cl3 (M ˆ Fe(III),
Cr(III)), L ˆ N-4-methoxyphenyl-N-4-chlorobenzoyl hydrazide are reported. In all the studied complexes the N-4-methox-
yphenyl-N-4-chlorobenzoyl hydrazide acts as a neutral bidentate chelating ligand with coordination involving the carbonyl
oxygen and nitrogen atom of the secondary hydrazide group. The complexes appear to have an pseudo-octahedral stereo-
chemistry. ESR parameters (g1 ˆ 4.432, g2 ˆ 1.991, D ˆ 0.096 cmϪ1) and meff ˆ 3.55 mB obtained for [CrL3]Cl3 also suggest
the possibilities of magnetic dipole–dipole coupling interactions between Cr(III) ions. ᭧ 1999 Elsevier Science B.V. All rights
reserved.
Keywords: Hydrazide; Metal complexes; IR spectra; ESR spectra; Magnetic moment
1. Introduction
2. Experimental
The ligand N-4-methoxyphenyl-N-4-chlorobenzoyl
hydrazide (L) (Fig. 1) has anti-inflammatory and
weakly analgesic activities. Because the metal
complexes of many drugs exhibit a greater biological
activity than the ligands themselves [1] the ML2Cl2
(M ˆ Cu(II), Mn(II), Ni(II)) and [ML3]Cl3 (M ˆ
Fe(III), Cr(III)) complexes were synthesized and
investigated by spectroscopic and magnetic measure-
ments for obtaining further informations about the
local structure around the metal ions
The N-4-methoxyphenyl-N-4-chlorobenzoyl hydra-
zide is obtained by the Fischer method [2].
The ligand was characterized by NMR and GC-MS.
1
The H NMR spectrum (CDCl3, d ppm) of the ligand
presents: (3.69 (s) 3H, OCH3), (4.83 (s) 2H, NH2) and
(6.68–7.29 8H aromatic). The 13C NMR spectrum
(CDCl3, d ppm) presents 10 signals, one corre-
sponding to the C atom from the methoxy group
(OCH3) at 55.47; eight signals in the aromatic region
(4CH: 114.6; 127.66; 128.40; 130.27 and 4C substi-
tuted ipso 129.0; 133.25; 136.0; 136.5) and a signal
corresponding to the C atom from the carbonyl group,
at 158.6 ppm. The m/z ˆ 276 and 137 signals in the
GC-MS spectrum confirm the proposed formula.
* Corresponding author. Tel.: ϩ 40 64 194315; fax: ϩ 40 64
191906.
E-mail address: leodavid@hera.ubbcluj.ro (L. David)
0022-2860/99/$ - see front matter ᭧ 1999 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(98)00930-2

150
L. David et al. / Journal of Molecular Structure 482–483 (1999) 149–152
3. Results and discussion
Partial assignments of the IR absorption bands
observed for the free ligand and the metal complexes
are given in Table 2.
The IR spectrum of the ligand shows an absorption
band centered at 1660 cmϪ1 characteristic for the
n(CyO) stretching vibration. In the IR spectra of the
complexes this band is shifted to the lower frequen-
cies suggesting the coordination of carbonyl oxygen
atom to the metal ions. The stretching vibration bands
n(NH2) are significantly shifted in the spectra of the
metal complexes indicating the involvment of the
nitrogen atom of the secondary hydrazide group in
the coordination.
Fig. 1. The structural formula of N-4-methoxyphenyl-N-4-chloro-
benzoyl hydrazide.
The complexes were obtained by adding to a solu-
tion of appropriate metal salts [CuCl2·2H2O (0.17 g,
1 mmol), MnCl2·4H2O (0.19 g, 1 mmol), CoCl2·6H2O
(0.23 g, 1 mmol), NiCl2·6H2O (0.23 g, 1 mmol),
FeCl3·6H2O (0.27 g, 1 mmol), CrCl3·6H2O (0.26 g,
1 mmol) in hot 50 ml MeOH the hydrazide ligand
(0.55 g (2.2 mmol) for M(II) complexes, and 0.83 g
(3 mmol) for M(III) complexes)]. The solutions were
stirred for 30 min and left at room temperature for
24 h. The complexes were purified by repeated
washing with acetone. The crude products were
recrystallized from methanol. Some analytical data
of the prepared compounds are given in Table 1.
Electronic spectra in absorption of methanol solu-
tions were registered with a Specord UV-VIS spectro-
meter. IR spectra were registered with a Specord IRA-
75-ZEISS spectrometer, using the KBr pellet tech-
nique. NMR spectra of the ligand dissolved in deut-
erated chloroform were registered with a Varian
Gemini-300 spectrometer. EPR spectra were recorded
at 9.4 GHz (X band) using a standard JEOL-JES-3B
equipment with a magnetic field modulation of
100 kHz. Room temperature magnetic susceptibility
measurements were made on powdered samples
using a Faraday type balance.
The deformation bands d(NH2) (1618 cmϪ1),
t(NH2) (1320 cmϪ1), g(NH2) (1040–1030 cmϪ1
)
and d(HNN) (1250 cmϪ1) are shifted insignificantly
in the IR spectra of the complexes because of the
disappearance of hydrogen bonds between CyO and
NH2.
The amide II band centered at 1515 cmϪ1 remains
approximately unchanged. The presence of this band
in the spectra of complexes proves the ketonic form of
the ligand.
From a consideration of the IR spectra it is clear
that in these complexes N-4-methoxyphenyl-N-4-
chlorobenzoyl hydrazide acts as a bidentate neutral
ligand through the carbonyl oxygen and nitrogen
atoms of the secondary hydrazide group.
The electronic spectrum of the ligand presents two
absorption bands at n1 ˆ 47 620 cmϪ1 and n2
35 087 cmϪ1. The n1 band is assigned to p –p* tran-
sitions in conjugated organic systems, which is over-
lapped by the p –p* transition in the carbonyl group.
The n2 band is characteristic for the p –p* transitions
ˆ
42 553 cmϪ1, respectively and a shoulder at n3
ˆ
Table 1
Analytical and physical data for the synthesized compound
Complexes
Color
Melting point (ЊC)
%C
%H
%N
Calculated
Found
Calculated
Found
Calculated
Found
CuL2Cl2
MnL3Cl2
NiL2Cl2
FeL3Cl3
CrL3Cl3
Green
Beige
Blue
Red
Green
153
146
153
167
162
48.83
49.49
49.40
50.81
51.01
48.54
49.20
49.00
50.46
50.89
3.78
3.83
3.81
3.96
3.95
4.01
4.05
4.02
4.15
4.17
8.14
8.25
8.20
8.47
8.50
7.98
7.86
8.24
8.32

L. David et al. / Journal of Molecular Structure 482–483 (1999) 149–152
151
Table 2
IR absorption bands (cmϪ1
)
nas(NH2)
ns(NH2)
n(CO) amide I
das(NH2)
n(CO) amide II
ds(NH2)
d(HNN)
L
3360 3260
3200
3175
2995
1660
1620
1625
1630
1630
1620
1620
1618
1585
1605
1605
1605
1605
1605
1515
1510
1512
1515
1513
1515
1515
1030
1010
1030
1030
1030
1030
1030
685
670
675
685
680
685
685
CuL2Cl2
MnL2Cl2
CoL2Cl2
NiL2Cl2
FeL3Cl3
CrL3Cl3
3260 3225
3225 3020
3170 3120
3195
3360 3090
3100 3030
3125
3030
in aromatic systems. The appearance of a shoulder at
n2 ˆ 35 087 cmϪ1 is caused by the p ! n transitions
in the carbonyl group.
CuO3N3 chromophore [3]. The magnetic moment of
meff ˆ 1.83 mB at room temperature is normal for
mononuclear complexes having no appreciable inter-
action between the metal ions.
The UV absorption spectra of the metal complexes
are similar. The presence of different cations leads to a
weak shift towards higher energies in these spectra.
These modifications might be correlated with the
involvement of N and O atoms from the ligand in
the coordination, which causes a strengthening of
CyO and in –NH2 bonds involved in the charge
transfer processes. UV absorption bands of synthe-
sized compounds are presented in Table 3 and confirm
the bidentate character of the ligand.
The absorption spectrum of NiL2Cl2 shows the
presence of three bands assigned to the following tran-
3
sitions in increasing order of energy: A2g(F) !
3
3T2g(F) at 13 500 cmϪ1
,
3A2g(F) ! T1g(F) at
16 200 cmϪ1 and A2g(F) ! T1g(P) whose corre-
3
3
sponding band is obscured by the charge transfer
edge. The magnetic moment of NiL2Cl2 meff
3.15 mB is in the range normally observed for octahe-
dral nickel(II) complexes [4].
ˆ
The electronic spectra in the visible region were
recorded in order to obtain some informations on
the coordination mode of metal cations to the hydra-
zide ligand.
The electronic spectrum of MnL2Cl2 in methanol
solution shows a charge transfer band Mn2ϩ ! L up
to Ϸ 16 000 cmϪ1. The absence of appreciable absorp-
tion at lower energy than the charge transfer edge is
consistent with a pseudo-octahedral environment
The electronic absorption spectra of CuL2Cl2 in the
visible region show one absorption band at
2
2
13 200 cmϪ1 assigned to a Eg(D) ! T2g(D) transi-
tion. The charge transfer band reaches up to
Ϸ 20 000 cmϪ1 and the charge transfer band of the
ligand overlaps it. The g ˆ 2.134 value of the
isotropic spectrum of the CuL2Cl2 is typical for a
Table 3
Absorption bands (cmϪ1) in the electronic spectra of complexes
(sh ˆ shoulder)
Complexes
n1 (cmϪ1
)
n2 (cmϪ1
)
n3 (cmϪ1
)
L
47620
47692
47634
47676
47648
47692
42553
43000
42942
42984
42956
43000
35087sh*
36462sh
36405sh
36442sh
36418sh
36462sh
CuL2Cl2
MnL3Cl2
[CrL3]Cl3
NiL2Cl2
FeL3Cl3
Fig. 2. Powder ESR spectrum of [CrL3]Cl3 complex at room
temperature.

152
L. David et al. / Journal of Molecular Structure 482–483 (1999) 149–152
about the metal ions. All d–d transitions for an octa-
hedral d5 ion are spin-forbidden and therefore any
absorption bands will be extremely weak [5]. The
ESR spectrum of MnL2Cl2 is characterized by a
quasi-isotropic g tensor with principal values close
to the spin-only value (g ˆ 2.002). The magnetic
moment meff ˆ 5.97 mB confirms the high-spin form
of the complex [6].
magnetic moment meff ˆ 5.81 mB is consistent with
the high-spin state.
4. Conclusions
In the ML2Cl2 complexes the divalent metal ion is
coordinated by two N-4-methoxyphenyl-N-4-chloro-
benzoyl hydrazide neutral bidentate chelating ligands
with chlorine atoms completing a pseudo-octhaedral
structure. The [FeL3]Cl3 and [CrL3]Cl3 complexes
contain three bidentate N-4-methoxyphenyl-N-4-
chlorobenzoyl hydrazide ligands giving a pseudo-
octahedral environment around the metal ions.
The UV-VIS electronic spectra, ESR spectra and
magnetic moments confirm the pseudo-octahedral
structure.
The electronic spectrum of [CrL3]Cl3 exhibits three
absorption bands at: 17 700 cmϪ1, assigned to the
4
4
transition T2g(F) ← A2g(F), at 23 300 cmϪ1 and
4
4T1g(F) ← A2g(F), at 36 400 cm1, that forms part of
the charge transfer band. Two absorption bands at g1 ˆ
4.432 and g2 ˆ 1.991 were observed in the EPR
spectra of the Cr(III) complexes at room temperature
(Fig. 2). The low-field absorption could be assigned to
isolated Cr(III) ions coordinated in a pseudo-octahe-
dral geometry (mononuclear species), whereas the
strong band could be associated to coupled Cr(III)
ions, i.e. dimeric or polynuclear species [7, 8]. The
In the case of the [CrL3]Cl3 complex a dipole–
dipole coupling interaction between Cr(III) ions is
possible.
large width of the geff ˆ 2 band absorption (DBpp
ˆ
References
470 G) indicates that the dominant coupling interac-
tion between Cr(III) ions is of the dipole–dipole type.
The value of the magnetic moment meff ˆ 3.55 mB is
lower than expected for octahedral Cr(III) ions and
confirm the possibilities of interactions between the
metal centers. The calculated value of zero-field split-
ting parameter (D ˆ 0.096 cmϪ1) [9] suggests a small
distortion from the octahedral environment of Cr(III).
The electronic spectrum of the complex [FeL3]Cl3
shows two shoulders at 26 540 cmϪ1 and
27 530 cmϪ1 that forms part of the charge transfer
band [10]. The ESR spectrum of [FeL3]Cl3 is almost
isotropic (g ˆ 2.002) and confirms the high-spin form
(S ˆ 5/2) as ground state. The presence of a small
signal at g ˆ 4.27 suggests a little distortion of the
octahedral symmetry around the metal ions [3]. The
[1] J.R.J. Sorenson, in: H. Sigel (Ed.), Metal Ions in Biological
Systems, 14, Marcel Dekker, New York, 1982, pp. 77.
[2] E. Fischer, Liebigs Ann. Chem. 199 (1879) 281.
[3] A. Bencini, D. Gatteschi, Transition Met. Chem. 1 (1980) xxx.
[4] A. Bury, A.E. Underhill, D.R. Kemp, N.J. O’Shea, J.P. Smith,
P.S. Gomm, Inorg. Chim. Acta 138 (1987) 85.
[5] C.K. Jorgensen, Absorption Spectra and Chemical Bonding in
Complexes, Addison-Wesley, Reading, MA, 1962.
[6] B.N. Figgis, J. Lewis, Progr. Inorg. Chem. 6 (1964) 37.
[7] M. Vicens, J.J. Fiol, A. Terron, V. Moreno, D.M.L. Good-
game, R.N. Sheppard, Inorg. Chim. Acta 192 (1992) 139.
[8] M. de la Fuente, O. Cozar, L. David, R. Navarro, A. Hernanz,
I. Bratu, Spectrochim. Acta PartA 53 (1997) 637.
[9] F.E. Mabbs, D. Collins, Electron Paramagnetic Resonance of
d Transition Metal Compounds, Elsevier, Amsterdam, 1992.
[10] D.D. Harrison, R. Thomas, A.E. Underhill, J.K. Fletcher, P.S.
Gomm, F. Haleway, Polyhedron 4 (1985) 4.