Vol.2, No.9, 1035-1043 (2010) Natural Science
http://dx.doi.org/10.4236/ns.2010.29127
Copyright © 2010 SciRes. OPEN ACCESS
Spectroscopic, thermal and magnetic properties of
some transition metal complexes derived from
1-Phenyl-3-Substituted-4-Nitroso-5-Pyrazolones
Samir A. Abdel-Latif1*, Yousry M. Issa2
1Chemistry Department, Faculty of Science, Helwan University, Helwan, Egypt; *Corresponding Author: salatif_1@yahoo.com
2Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt
Received 25 June 2010; revised 28 July 28 2010; accepted 5 August 2010.
ABSTRACT
Complexes derived from some 1-Phenyl-3-meth-
yl-4-nitroso-5-pyrazolone (L1), 1,3-diphenyl-4-
nitroso-5-pyrazolone (L2) and 1-phenyl-3-anilino-
4-nitroso-5-pyrazolone (L3) with Mn2+, Co2+, Ni2+,
Cu2+ and Zn2+ metal ions have been prepared.
Structural investigation of the ligands and their
complexes has been made based on elemental
analysis, infrared (FT-IR), ultraviolet and visible
spectra (UV-Vis.), proton nuclear magnetic reso-
nance (1H NMR), magnetic susceptibility (eff.)
and thermal analysis (TG and DTG). The effect
of solvents has been carried out in organic
solvents of varying polarity. The observed tran-
sition energy and oscillator strengths were also
calculated. The data obtained show that all of
the prepared complexes contain water mole-
cules in their coordination sphere. The investi-
gated ligands acts as neutral bidentate ligands
bonded to the metal ions through the two oxy-
gen atoms of the carbonyl and nitroso groups.
The isolated complexes behave as non-electro-
lyte in DMF solution. The Mn2+, Co2+, Ni2+ and
Cu2+ complexes show high spin configurations
as the ground state. The high spin values of ma-
gnetic susceptibility may be due to the ligands
being weak ligands. The Mn2+, Co2+, Ni2+, Cu2+
and Zn2+ complexes exhibit an octahedral or
distorted octahedral coordination with the in-
vestigated ligands.
Keywords: Nitrosopyrazolones; Transition Metal
Complexes; Spectroscopic; Thermal; Magnetic
studies
1. INTRODUCTION
Pyrazolones and their pyrazol derivatives are formed by
the reaction between hydrazines and -keto esters e.g.
3-methy-1-phenylpyrazolone was prepared from phenyl-
hydrazine and ethyl acetoacetate. This on methylation
gives antipyrine which is used in medicine as an antipy-
retic [1]. Nitrosopyrazolones are used as analytical re-
agents. Pyrazolone derivatives are capable of forming
complexes with a large number of transition metal ions
[2-5]. The formed complexes are characterized by their
high stability due to the formation of six-membered
rings. 4-Nitroso-2-pyrazolin-5-one derivatives have sig-
nificant activity against Pyricularia oryzae [6,7]. Com-
plexation behaviour of 4-hydroxy-2,2,6,6-tetramethylpi-
pridine-1-oxyl, oximido-benzotetronic acid and 4-nitroso-
3-methyl-1-phenyl-2-pyrazoline-5-one each containing
the same NO coordination group was complexed with
some transition metal ions [8]. 1,3-Dimethyl-4-nitrosopy-
razol-5-ol dissolved in methanol or DMSO together with
small amount of H2O2 gives rise to nitroxide radicals
when irradiated by UV light [9]. Nitrosation at C-4 of
1-n-alkyl-3-methyl-5-pyrazolone was achieved with so-
dium nitrite in hydrochloric acid medium. A tautomeric
equilibrium in solution with a proton moving from OH
at C-5 to nitrosated pyrazolones was proposed [10]. The
structure and relative stabilities of the tautomers and
isomers of 4-nitroso-pyrazolones were investigated at
HF, DFT and MPn (n = 2, 4) quantum chemical levels.
1H, 13C and 15N NMR chemical shielding and coupling
constants were calculated [11].
The present study deals with the preparation of Mn2+ ,
Co2+, Ni2+, Cu2+ and Zn2+ complexes with the investi-
gated ligands (L1-L3). The complexes obtained were
subjected to many analytical tools such as elemental
analysis, infrared (FT-IR), thermogravimetric (TG) and
derivative thermogravimetric analysis (DTG), molar
conductance, magnetic susceptibility (eff.) and elec-
tronic spectra to throw some light on the bonds formed
and on their structure.
S. A. Abdel-Latif et al. / Natural Science 2 (2010) 1035-1043
Copyright © 2010 SciRes. OPEN ACCESS
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2. EXPERIMENTAL
All chemicals used in this work were chemically pure,
obtained from BDH chemicals. They include MnCl2.
4H2O, CoCl2.6H2O, NiCl2.6H2O, CuCl2.2H2O and ZnCl2,
NH4OH, sodium nitrite, ethyl acetoacetate, phenylhy-
drazine, ethyl benzoylacetate, 1-phenyl-3-amino-5-pyra-
zolone, aniline, sodium ethoxide, ethyl cyanoacetate. The
solvents used were methanol, ethanol, deutrated dimethyl
sulfoxide (d6-DMSO), dimethyl formamide (DMF), chl-
oroform, cyclohexane, isopropanol, dioxane, hydrochlo-
ric acid and sodium hydroxide.
2.1. Synthesis of the Ligands
The 1-phenyl-3-methyl-5-pyrazolone was prepared from
ethyl acetoacetate and phenylhydrazine according to the
method described by Vogel [12], m.p. 127. 1,3-Dip-
henyl-5-pyrazolone was prepared from ethyl benzoy-
lacetate and phenylhydrazine [12]. 1-Phenyl-3-anilino-
5-pyrazolone was obtained by the method described by
Weissberger [13] from a mixture of 1-phenyl-3-amino-5-
pyrazolone and aniline, m.p. 221. The investigated
ligands were prepared [14] as follows, the nitrosation
reactions were carried out by acidifying the cold aqueous
solution of 1-phenyl-3-substituted-5-pyrazolone deriva-
tives (0.1 mol) at 0 in sodium hydroxide solution con-
taining equivalent amount of sodium nitrite (0.1 mol)
with hydrochloric acid. The precipitated ligands were
filtered off, washed several times with water and recrys-
tallized from ethanol. The purity of the compounds was
determined from the results of elemental analysis and are
summarized in Table 1, IR and 1H NMR spectra. The
resulting ligands have the following general formulae:
R
N
NO
NO
where R = CH3-, (1-phenyl-3-methyl-4-nitroso-5-pyra-
zolone), (L1)
R = C6H5-, (1,3-diphenyl-4-nitroso-5-pyrazolone), (L2)
R = C6H5-NH-, (1-phenyl-3-anilino-4-nitroso-5-pyrazo-
lone), (L3)
2.2. Synthesis of the Complexes
The 1:1 or 1:2 complexes were prepared by mixing a hot
alcoholic solution of the investigated ligands (0.001 or
0.002 mol) with the calculated (0.001 mol) of metal salt
solution. The reaction mixture was refluxed for 4 h. The
pH of the solution was maintained at a value of 5.0-6.0
by the addition of dilute ammonia solution (1:10). The
solid complexes were dried on a steam bath with stirring,
then filtered off and washed several times with etha-
nol-water mixture, (1:1 v/v) till a colorless filtrate was
obtained. The solid complexes were dried by suction and
finally kept in vacuum desiccators.
2.3. Physical Measurements
The FT-IR spectra were recorded in the range 4000-400
cm-1 on a Jasco FT-IR spectrophotometer as KBr discs.
The NMR spectra were measured using Varian Gemini
200-200 MHz spectrometer and the spectra were re-
corded from 0-15 ppm using TMS as an internal stan-
dard in dimethylsulfoxide (d6-DMSO) as the solvent.
Thermal analyses (TG and DTG) were obtained in a
nitrogen atmosphere using a type TGA 50 of Shimadzu
derivatograph thermal analyzer. The molar conductivi-
ties were carried out using a Jenway 4310 conductivity
meter. Electronic spectra were recorded in the range
200-800 nm, on Jasco V-530 UV-Vis. spectrophotometer.
Magnetic susceptibility values were obtained at room
temperature using magnetic susceptibility balance (Sher-
wood scientific), Cambridge Science Park, Cambridge,
England.
3. RESULTS AND DISCUSSION
3.1. Characterization of the Ligands
The structures of the investigated ligands (L1-L3) were
established by the use of elemental analysis in Table 1,
IR, UV-Vis and 1H NMR spectra.
3.1.1. Infrared Studies
The infrared spectra of the investigated ligands and the
most important IR band assignments that affect the
structural features are listed in Table 2. The NH ap-
pears as a medium broad one at 3210 cm-1 for ligand L3.
The band appearing at 1705, 1678 and 1688 cm-1 are
ascribed to the stretching frequency of the C=O group
for ligands L1-L3, respectively. The band observed
within the range 1410-1359 cm-1 assigned to N = O
[14].
3.1.2. 1H NMR Spectra
The different types of protons in DMSO of the investi-
gated ligands (L1-L3) were obtained. The spectra of the
ligands L1-L3 exhibit a sharp singlet signal at 2.23 ppm.
This signal is assigned to the aliphatic proton at position
number 4 [15,16] as shown in Figure:
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Table 1. Elemental analyses and magnetic moments for Mn2+, Co2+, Ni2+, Cu2+ and Zn2+ complexes with the investigated ligands
(L1-L3).
Ligands and
Complexes Tentative Formula M:L m.p
C
H
% Calculated
N
(found)
Cl
M
eff.
L1 C10H9N3O2 -- 155 59.11 (59.3) 4.43(4,2) 20.68 (20.4)-- -- --
L2 C15H11N3O2 -- 235 67.64 (67.8) 4.15 (4.5) 15.84 (15.6)-- -- --
L3 C15H12N4O2 -- 241 64.28 (64.2 4.24 (4.3) 20.00 (19.8)-- -- --
Mn-L1 [MnC10H21N3O8Cl2] 1:1 325 27.52 (27.5) 4.81 (4.3) 9.63 (9.4) 16.05 (16.3) 12.59 (13.0)5.94
Mn-(L1)2 [MnC20H20N6O6] 1:2 330 48.49 (48.2) 4.04 (3.9) 16.97 (17.2)-- 11.09 (10.8)5.86
Co-L1 [CoC10H15N3O5Cl2] 1:1 345 31.09 (30.9) 3.88 (3.7) 10.88 (11.1)18.13 (18.5) 15.26 (14.9)3.91
Co-(L1)2 [CoC20H24N6O8] 1:2 344 44.86 (44.4) 4.48 (4.5) 15.70 (15.9)-- 11.01 (10.9)3.98
Ni-L1 [NiC10H29N3O12Cl2] 1:1 343 23.45 (23.2) 5.66 (5.8) 8.20 (8.4) 13.67 (13.8) 11.47 (11.1)3.12
Ni-(L1)2 [NiC20H22N6O7] 1:2 335 46.44 (46.4) 4.25 (4.1) 16.25 (16.2)-- 11.36 (11.4)3.10
Cu-L1 [CuC10H17N3O6Cl2] 1:1 305 29.37(28.9) 4.16 (4.3) 10.28 (10.4)17.13 (16.9) 15.54 (15.8)1.99
Cu-(L1)2 [CuC20H26N6O9] 1:2 343 43.04 (43.2) 4.66 (4.2) 15.06 (15.2)-- 11.39 (11.5)2.10
Zn-L1 [ZnC10H15N3O5Cl2] 1:1 335 30.58 (30.7) 3.82 (3.9) 10.70 (10.9)17.83 (17.9) 16.66 (16.8)--
Zn-(L1)2 [ZnC20H22N6O7] 1:2 355 45.85 (45.9) 4.20 (4.1) 16.04 (16.3)-- 12.49 (12.8)--
Mn-L2 [MnC15H19N3O6Cl2] 1:1 342 38.96 (38.5) 4.11( 4.0) 9.09 (8.9) 15.15 (15.3) 11.88 (11.7)5.84
Mn-(L2)2 [MnC30H28N6O8] 1:2 320 54.97 (55.1) 4.27 (4.4) 12.82 (12.8)-- 8.38 (8.6) 5.66
Co-L2 [CoC15H17N3O5Cl2] 1:1 328 40.18 (40.4) 3.97 (3.6) 9.37 (9.2) 15.62 (15.4) 13.15 (12.8)3.81
Co-(L2)2 [CoC30H28N6O8] 1:2 335 54.63 (54.6) 4.24 (4.4) 12.74 (12.5)-- 8.93 (8.7) 3.78
Ni-L2 [NiC15H17N3O5Cl2] 1:1 350 40.20 (40.6) 3.79 (3.9) 9.38 (9.5) 15.63 (15.7) 13.11 (13.4)2.99
Ni-(L2)2 [NiC30H28N6O8] 1:2 337 54.65 (54.7) 4.25 (4.4) 12.75 (13.1)-- 8.91 (8.6) 3.00
Cu-L2 [CuC15H17N3O5Cl2] 1:1 281 39.77 (39.8) 3.75 (3.9) 9.28 (9.4) 15.46 (15.7) 14.03 (14.4)2.05
Cu-(L2)2 [CuC30H26N6O7] 1:2 290 55.77 (55.4) 4.02 (4.1) 13.01 (13.1)-- 9.83 (9.9) 1.98
Zn-L2 [ZnC15H17N3O5Cl2] 1:1 355 39.61 (39.4) 3.74 (3.8) 9.24 ( 9.4) 15.40 (15.6) 14.39 (14.5)--
Zn-(L2)2 [ZnC30H28N6O8] 1:2 334 54.10 (54.3) 4.20 (4.3) 12.62 (12.7)-- 9.82 (9.7) --
Mn-L3 [MnC15H28N4O10Cl2] 1:1 341 32.79 (32.6) 5.10 (5.3) 10.20 (9.9) 12.75 (13.2) 10.00 (9.8) 5.74
Mn-(L3)2 [MnC30H30N8O8] 1:2 327 52.56 (52.6) 4.38 (4.9) 16.35 (17.2)-- 8.01 (7.82 5.86
Co-L3 [CoC15H20N4O6Cl2] 1:1 348 37.42 (37.7) 4.15 (4.3) 11.64 (11.9)14.55 (14.8) 12.24 (12.4)3.87
Co-(L3)2 [CoC30H26N8O5Cl2] 1:2 345 50.92 (50.6) 3.67 (3.4) 15.84 (15.9)9.90 (9.8) 8.33 (8.1) 3.91
Ni-L3 [NiC15H16N4O4Cl2] 1:1 345 40.47 (40.3) 3.59 (3.3) 12.59 (13.4)15.74 (16.3) 13.19 (12.7)2.90
Ni-(L3)2 [NiC30H36N8O10Cl2] 1:2 335 45.18 (45.6) 4.51 (4.6) 14.05 (13.9)8.78 (9.5) 7.36 (6.9) 2.88
Cu-L3 [CuC15H16N4O4Cl2] 1:1 295 40.04 (40.6)3.55 (3.9) 12.45 (12.8)15.57 (15.2) 14.12 (14.3)1.99
Cu-(L3)2 [CuC30H28N8O7] 1:2 306 53.29 (53.4) 4.14 (4.3) 16.58 16.7) -- 9.40 (9.7) 1.84
Zn-L3 [ZnC15H16N4O4Cl2] 1:1 338 39.87 (40.3) 3.54 (3.6) 12.40 (11.9)15.50 (15.3) 14.48 (15.0)--
Zn-(L3)2 [ZnC30H30N8O8] 1:2 357 51.76 (51.6) 4.31 (4.2) 16.10 (16.4)-- 9.40 (9.5) --
S. A. Abdel-Latif et al. / Natural Science 2 (2010) 1035-1043
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Table 2. IR band assignments for the investigated ligands
(L1-L3).
L1 L2 L3 Band assignment
-- -- 3210 m NH
3050 m 3048 m 3070 m CH
1705 w 1678 w 1688 w C=O
1652 m 1595 m 1629 m C=N
1499 m 1493 m 1494 m C=C
1410 s 1414 s 1395 s N=O
R
1
2
34
5
N
NO
NO
H
For ligand L1, a singlet observed at 2.40 ppm is as-
signed to CH3 protons (the integration curve shows three
protons). The signals observed at 7.23-7.84, 7.20-8.17
and 7.03-7.87 ppm are assigned to the aromatic hydro-
gen protons (the integration curve shows five and ten
protons for the investigated ligands L1-L3, respectively).
The spectrum of ligand L3 exhibits a singlet signal ob-
served at 6.43 ppm is assigned to NH proton (the inte-
gration curve shows one proton).
3.1.3. Electronic Spectral Studies
The electronic spectral band of the investigated ligands
scanned in different organic solvents are depicted in Ta-
ble 3. In methanol solution, ligands L1 and L2 show
three bands, the first one at 253-268 nm referred to -*
transition within the phenyl rings. The second band ob-
served at 317-321 nm is ascribed to n-* transition of
the carbonyl group. The third band at 385-400 nm arises
from a transition involving electron migration along the
entire conjugate system of the ligand i.e. comprises
charge transfer (CT) from phenyl ring to the carbonyl
group by resonance and from hetero ring by induction
[17]. In case of chloroform, cyclohexane, isopropanol
and dioxane, the spectra show two bands within the
range 260-423 nm. The first band at 260-263 nm is as-
signed to -* transition within the phenyl rings. The
second band at 403-423 nm is ascribed to charge transfer
interaction from the phenyl ring to the carbonyl group.
For ligand L3 only one absorption band observed at
248-259 nm which may be ascribed to the high energy
-* transition within the phenyl rings.
The ionization potential (Ip) of the investigated
ligands (L1-L3) is calculated from their electronic spec-
tral data applying the relationships previously applied
[18-20]. The value of the experimental transition ener-
gies (ECT) and oscillator strengths (f) were calculated
from max of the electronic spectra applying the equa-
tions previously reported [18-20].
The calculated ECT values, as well as, the correspond-
ing ionization potential (Ip) of the investigated ligands
L1-L3 in different organic solvents are listed in Table 3.
The variation in Ip values was found to follow the same
order as max of the CT band.
3.2. Characterization of the Complexes
The solid complexes were subjected to elemental analy-
sis and metal content, infrared (FT-IR), ultraviolet and
visible spectra (UV-Vis.), magnetic susceptibility (eff.)
and thermal analysis. The results of elemental analysis
are given in Table 1 and are in good agreement with
those calculated by the proposed formulae for 1:1 and
1:2 (M:L) solid complexes.
3.2.1. Conductimetric Measurements
Conductimetric titrations of Mn2+, Co2+, Ni2+, Cu2+ and
Zn2+ metal ions with the investigated nitrosopyrazolone
derivatives (L1-L3) were obtained by plotting the calcu-
lated molar ratio [L]/[M] against the corrected molar
conductance values. The results indicate that the con-
ductance increases with the addition of the metal ion
solution due to the release of the highly conducting hy-
drogen ions which may be present in nitroso-oxime
tautomers as a result of chelation [10,16]. The titration
curves show the presence of two distinctive breaks at
metal to ligand 1:1 and 1:2 (M:L), respectively.
The prepared solid complexes of Mn2+, Co2+, Ni2+,
Cu2+ and Zn2+ metal ions with the investigated ligands
(L1-L3) were subjected to elemental analysis for their C,
H, N, Cl and metal content [21], infrared (FT-IR), ultra-
violet and visible spectra (UV-Vis.), magnetic suscepti-
bility (eff.) and thermal analysis.
3.2.2. Infrared Studies
Infrared spectral data of the investigated complexes dis-
play interesting changes which may give a reasonable
idea about these complexes. However, if these changes
were interpreted in relation to elemental analysis in Ta-
ble 1, also the thermogravimetric analysis, molar con-
ductance, electronic spectra and magnetic susceptibility
measurements, the structure of the solid complexes may
be clarified.
In the spectra of the complexes (Table 4) the band
observed within the range 1410-1395 cm-1 [14] assigned
to N=O in the free ligands shiftes to lower wave num-
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Table 3. The transition energy (ECT), ionization potential (IP), oscillator strengths (f) and molar absorptivity () derived from the elec-
tronic spectra of ligands L1 and L2 in different organic solvents.
Ligand Solvent Absorbance max, nm ECT I
P f max x 10-4
Chloroform 0.06 403 3.07 7.30 0.02 0.12
Cyclohexane 0.06 403 3.07 7.30 0.02 0.13
Isopropanol 0.08 403 3.07 7.23 0.03 0.16
Dioxane 0.06 414 2.99 7.21 0.02 0.12
L1
Methanol 0.12 385 3.22 7.39 0.04 0.24
Chloroform 0.07 423 2.93 7.16 0.06 0.28
Isopropanol 0.30 326 3.80 7.84 0.12 1.20
Dioxane 0.07 411 3.01 7.23 0.05 0.28
L2
Methanol 0.10 400 3.09 7.29 0.06 0.40
ber indicating the involvement of the N=O group in
chelation. Also, the shift of N = O group indicated that it
is a center of chelation as it loses its double bond char-
acter. The band observed within the range 1705-1678
cm-1 assigned to C=O in the free ligands shiftes to
lower wave number (1610-1650 cm-1) indicating the
involvement of the C=O group in chelation as it also
loses its double bond character [14]. The OH stretching
frequency appears within the range 3336-3447 cm-1 for
1:1 and 1:2 complexes as broad band. This is due to the
presence of water of hydration and/or coordinated water
molecules. In some complexes, a sharp band appears
within the range 3423-3640 cm-1 ascribed to chelated
OH-, which replace the Cl- ion in coordination sphere.
The OH frequency will be masked under the previously
detected broad band [16]. The spectra of the metal com-
plexes exhibit bands in the range 478-550 cm-1 that may
be assigned to M-O stretching frequency [22,23]. These
bands are not observed in the spectra of the free ligands
and are possibly due to the formation of coordinated
bond (MO) or (M-O).
3.2.3. Thermal Analysis
TG analyses are very useful method for investigating the
thermal decomposition of solid substances involving
simple metal salts [24], as well as for complex com-
pounds [25,26]. The thermogram follows the decrease in
sample weight with the linear increase in heat treatment
temperature (10 min-1) up to 800. The aim of the
thermal analysis is to obtain information concerning the
thermal stability of the investigated complexes as seen in
Table 5 and Figure 1, to decide whether water mole-
cules are inside or outside the coordination sphere.
For Mn-L3 (1:1) complex, a mass loss occurred within
the temperature range 34-106 corresponding to the
loss of 3.25% (Calcd 3.27%) for one molecule of water
Figure 1. Thermogravimetric and derivative thermal analyses
curves of Ni-L1 (a), Co-L2 (b) and Mn-L3 (c) 1:1 complex.
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1040
Table 4. IR band assignment of Mn2+, Co2+, Ni2+, Cu2+ and Zn2+ complexes with the investigated ligands (L1-L3).
Complex M:L
(OH-) (OH) (H2O) (NH) (C=O) (C=N) (N=O) (M-O)
[Mn(L1)(Cl)2(H2O)2]. 4H2O 1:1 -- 3430 s -- 1636 w 1593 m 1335 s 500 m
[Mn(L1)2(OH)2] 1:2 3465 s 3435 s -- 1637 w 1523 m 1340 s 508 m
[Co(L1)(Cl)2(H2O)2]. H2O 1:1 -- 3400 s -- 1630 w -- 1350 s 505 m
[Co(L1)2(OH)2]. 2H2O 1:2 3552 s 3398 s -- 1635 w 1499 w 1340 s 509 m
[Ni(L1)(Cl)2(H2O)2]. 8H2O 1:1 -- 3425 s -- 1631 w -- 1353 s 550 m
[Ni(L1)2(OH)2]. H2O 1:2 3463 s 3418 s -- 1631 w -- 1340 s 510 m
[Cu(L1)(Cl)2(H2O)2]. 2H2O 1:1 -- 3352 s -- 1623 w 1488 w 1375 s 530 m
[Cu(L1)2(OH)2]. 3H2O 1:2 3435 s 3358 s -- 1646 w -- 1408 s 509 m
[Zn(L1)(Cl)2(H2O)2]. H2O 1:1 -- 3362 s -- 1637 w 1527 m 1365 s 509 m
[Zn(L1)2(OH)2]. H2O 1:2 3444 s 3396 s -- 1637 w 1535 m 1340 s 510 m
[Mn(L2)(Cl)2(H2O)2]. 2H2O 1:1 -- 3360 s -- 1632 w 1580 m 1356 s 509 m
[Mn(L2)2(OH)2]. 2H2O 1:2 3500 s 3397 s -- 1632 w 1595 m 1356 s 500 m
[Co(L2)(Cl)2(H2O)2]. H2O 1:1 -- 3405 s -- 1627 m 1595 m 1358 s 488 m
[Co(L2)2(OH)2]. 2H2O 1:2 3630 s 3360 s -- 1627 m 1595 w 1357 s 500 m
[Ni(L2)(Cl)2(H2O)2]. H2O 1:1 -- 3433 s -- 1632 w 1596 w 1359 s 478 w
[Ni(L2)2(OH)2]. 2H2O 1:2 3640 s 3405 s -- 1632 w 1596 w 1359 s 487 w
[Cu(L2)(Cl)2(H2O)2]. H2O 1:1 -- 3369 s -- 1620 w 1532 m 1421 s 486 m
[Cu(L2)2(OH)2]. H2O 1:2 3610 s 3289 s -- 1624 w 1610 m 1419 s 486 m
[Zn(L2)(Cl)2(H2O)2]. H2O 1:1 -- 3402 s -- 1635 m 1612 m 1378 s 507 w
[Zn(L2)2(OH)2]. 2H2O 1:2 3630 s 3388 s -- 1615 m 1614 m 1380 s 497 w
[Mn(L3)(Cl)2(H2O)2]. 6H2O 1:1 -- 3445 s 3350 m 1619 w 1570 m 1377 s 505 w
[Mn(L3)2(OH)2]. 2H2O 1:2 3423 s 3340 s 3220 m 1650 w 1631 m 1361 s 504 w
[Co(L3)(Cl)2(H2O)2]. 2H2O 1:1 -- 3447 s 3335 m 1620 w 1575 w 1378 s 510 w
[Co(L3)2(Cl)2]. H2O 1:2 -- 3336 s 3210 m 1627 w 1570 w 1362 s 508 w
[Ni(L3)(Cl)2]. 2H2O 1:1 -- 3344 s 3200 m 1621 w 1600 m 1390 s 510 m
[Ni(L3)2(Cl)2]. 6H2O 1:2 -- 3344 s 3200 m 1621 w 1563 m 1390 s 510 m
[Cu(L3)(Cl)2]. 2H2O 1:1 -- 3348 s 3220 m 1610 w 1580 m 1365 s 510 m
[Cu(L3)2(OH)2]. H2O 1:2 3446 s 3348 s 3230 m 1612 w 1550 m 1360 s 511 m
[Zn(L3)(Cl)2(H2O)2] 1:1 -- 3354 s 3227 m 1624 w 1567 w 1394 s 494 w
[Zn(L3)2(OH)2]. 2H2O 1:2 3552 s 3364 s 3245 m 1618 w 1615 w 1401 s 497 w
s: strong, m: medium, w: weak
and at the temperature range 108-170 another loss of
2.88% (Calcd. 3.20%) for another one water molecule. In
the temperature range 170-256 a mass loss of 14.44%
(Calcd. 14.03%) corresponding to four water molecules.
At the temperature 256-351 a loss of 8.10% (Calcd.
8.16%) for two coordinated water molecules. At higher
temperature range 353-585 a loss of 23.40% (Calcd.
23.78) and at the temperature range 585-797 a loss of
11.68% (Calcd. 11.88%) corresponding to a loss of the
organic moiety as an intermediate species. At the end of
the thermogram at higher temperature the metal oxide and
chloride residues MnO and MnCl2 are formed as final
S. A. Abdel-Latif et al. / Natural Science 2 (2010) 1035-1043
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Table 5. Thermogravimetric results of Mn2+, Co2+ and Ni2+ complexes with the investigated ligands (L1-L3).
Calcd. Found Assignment
Complex M. Wt.
Temp. loss % loss %
[Mn(C15H12N4O2)(Cl)2 (H2O)2]. 6H2O 548.9 34-105 3.27 3.25 H2O
[Mn(C15H12N4O2)(Cl)2 (H2O)2]. 5H2O 530.9 105-170 3.39 2.88 H2O
[Mn(C15H12N4O2)(Cl)2 (H2O)2]. 4H2O 512.9 170-256 14.03 14.44 4 H2O
[Mn(C15H12N4O2)(Cl)2 (H2O)2] 440.9 256-351 8.16 8.10 2 coordinated H2O
[Mn(C15H12N4O2)(Cl)2] 404.9 353-585 23.78 23.40 -NHPh, NO
[Mn(C12H6O)(Cl)2] 282.9 585-797 11.88 11.68 3 C, H, N2
800 35.66 35.71 MnCl2 + MnO
[Co(C15H11N3O2)(Cl)2(H2O)2]. H2O 447.9 79-213 12.05 11.90 H2O, 2 coordinated H2O
[Co(C15H11N3O2)(Cl)2] 393.9 213-460 61.84 61.00 2Ph, Cl2, C-CH, CO
[Co(N3O)] 116.9 461-721 12.94 13.00 NO, N2
721-800 16.72 16.50 CoO
[Ni(C10H9N3O2)(Cl)2(H2O)2]. 8H2O 511.7 37-144 7.03 6.50 2 H2O
[Ni(C10H9N3O2)(Cl)2(H2O)2]. 6H2O 475.7 146-370 28.14 28.90 6 H2O, 2 coordinated H2O
[Ni(C10H9N3O2)(Cl)2] 331.7 372-607 24.62 24.60 N2, C-CH, NO, CH3, CO
607-800 39.71 39.99 NiCl2 +NiO
product, the remainder is 35.71% (Calcd. 35.66%).
For Ni-L1 (1:1) complex, a mass loss occurred within
the temperature range 36-144 corresponding to the
loss of 6.5% (Calcd. 7.03%) for two hydrated water mo-
lecules and at the temperature range 146-370 corre-
sponding to a loss of 28.90% (Calcd. 28.14%) for hy-
drated and two coordinated water molecules. In the
temperature range 372-607 a mass loss of 24.60%
(Calcd. 24.62%) corresponding to the formation of in-
termediate species through the decomposition of the
organic moiety of the complex [15] and this continues
till a constant weight is obtained where a mixture of
nickel chloride and nickel oxide residue are formed, the
remainder is 39.99% (Calcd. 39.71%).
For Co-L2 (1:1) complex, a mass loss occurred within
the temperature range 79-213 corresponding to a loss
of 11.90% (Calcd. 12.05%) for three water molecules. At
the temperature range 213-460 a loss of 61.00%
(Calcd. 61.84%) and at the temperature range 461-721
a loss of 13.00% (Calcd. 12.94%) corresponding to the
formation of intermediate species. At higher temperature
more than 721 and at the end of the process a metallic
oxide residue CoO is formed, the remainder is 16.50%
(Calcd. 16.72%).
3.2.4. Molar Conductance Measurements
The molar conductivities of 1 mM in DMF (10-3 M) of
some of the given complexes show that the investigated
complexes are neutral in nature since the values obtained
are 7.45-37.7 ohm-1 cm2 mol-1. These values were small
to account for ionic complexes of the investigated metal
ions.
For Mn-L1 (1:2), Co-L1 (1:1), Ni-L1 (1:1) and (1:2),
Cu-L1 (1:2) and Zn-L1 (1:2), the values were 20.30,
17.29, 7.45, 13.88, 19.46 and 17.20 ohm-1 cm2 mol-1,
respectively.
For Mn-L2 (1:2), Co-L2 (1:2), Ni-L2 (1:2) and Cu-L2
(1:2) the values were 16.74, 10.25, 13.85 and 11.17
ohm-1 cm2 mol-1, respectively.
For Mn-L3 (1:1), Co-L3 (1:2), Ni-L3 (1:1) and (1:2),
Cu-L3 (1:1) and Zn-L3 (1:1), the values were 25.30,
37.70, 20.90, 24.30, 32.7 and 13.25 ohm-1 cm2 mol-1,
respectively. These low conductivity values may be as-
cribed to the coordination of chloride ions, if present,
rather than the ionic association to the metal ions during
complex formation. This directly supports the fact that
all of the investigated complexes are non-ionic in nature.
3.2.5. Electronic Spectral and Magnetic Studies
The Mn2+, Co2+, Ni2+ and Cu2+ complexes (Table 1)
show a high spin value d5, d3, d2 and d1 configurations as
the ground state, the magnetic susceptibility (eff. =
5.66-5.94 B. M.), (eff. = 3.78-3.98 B. M.), (eff. =
2.88-3.12 B. M.) and (eff. = 1.84-2.10 B. M.) with the
ligands (L1-L3), respectively, indicating (32
2
te
g
g), (3
2
te
g
g),
(2
2
te
g
g) and (1
2
te
g
g). The high spin values of magnetic
susceptibility may be due to the ligands being weak
ligands [27].
S. A. Abdel-Latif et al. / Natural Science 2 (2010) 1035-1043
Copyright © 2010 SciRes. OPEN ACCESS
1042
Electronic absorption spectra of the free ligands and
some of their chelates were recorded in DMF. In the free
ligands the CT band appears in the range 385-400 nm for
the ligands L1-L3. A shift to longer wavelength is ob-
served on complex formation. This may be attributed to
the ML charge transfer CT spectra. A band of low in-
tensity is observed at 460 nm for Co-L1 (1:1), and 458
nm for Co-L3 (1:2) which is typical for six-coordinate
high-spin Co2+ complexes. The corresponding bands in
the octahedral [Co(H2O)6]2+ ion have been assigned to
4T1g4T2g (F), 4T1g2A1g (F) and 4T1g4T1g (P) transi-
tions, respectively [28]. The absorption spectral bands of
Ni-L3 (1:1) at 458 nm and 450 for Ni-L2 (1:2) are as-
signed to the 3A2g3T1g (F) and 3A2g3T1g (P) transi-
tions, respectively, in an octahedral geometry [29] and is
almost identical with that of the octahedral [Ni(H2O)6]2+
ion [30]. It is difficult to relate spectra with the structure
of Cu2+ complexes, especially in view of the distorted
geometry observed for its complexes [28].
Based on the above results the suggested structures of
the 1:1 and 1:2 (M:L) complexes between the metal ions
and the ligands can be represented as follows:
M
Cl
Cl
R
H2O
H2O
N
N
O
NO
(1:1) complexes
(1:2) complexes
X = OH in all cases except for Co2+ and Ni2+ with ligand L3
R = CH3-, Ph- and PhNH-, (1:2) complexes
4. CONCLUSIONS
In the present paper, the data obtained from elemental
analysis, FT-IR, electronic absorption spectra, thermal
analyses, molar conductivities and magnetic susceptibil-
ity measurements show that the complexes of Mn2+,
Co2+, Ni2+, Cu2+ and Zn2+ metal ions with the investi-
gated ligands L1-L3 may be formulated, where bonding
in case of 1:1 and 1:2 complexes are formed through
coordination with oxygen of the carbonyl group and
nitroso group. The complexes obtained contain water of
coordination in their sphere. The investigated ligands act
as neutral bidentate ligands. The solid complexes pre-
pared behave as non-electrolytes in DMF solution. The
electronic spectra of the investigated ligands exhibits a
CT band appears in the range 385-400 nm for the ligands
L1-L3. A shift to higher wavelength is observed on
complex formation which may be attributed to ML
charge transfer spectra. The bands observed at higher
wavelengths which are not observed in the spectra of the
free ligands may be ascribed to d-d electronic transition
within the metal ions. The complexes exhibit an octahe-
dral or distorted octahedral (Cu2+ complexes) coordina-
tion with the investigated ligands.
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