Schiff base complexes derived from salicylaldehyde with amine, [Ni(1,2-pn)2Cl2]·3H2O and [Cu(1,2-pn)2]SO4·2H2O, as complex ligands

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SCHIFF BASE COMPLEXES DERIVED FROM
SALICYLALDEHYDE WITH AMINE, [Ni(1,2-pn)2Cl2]·3H2O
AND [Cu(1,2-pn)2]SO4·2H2O, AS COMPLEX LIGANDS
Saied M. E. Khalil a , Shaker L. Stefan a & Khaled A. Bashir a
a Department of Chemistry, Faculty of Education , Ain Shams University , Cairo, Egypt
Published online: 15 Feb 2007.
To cite this article: Saied M. E. Khalil , Shaker L. Stefan & Khaled A. Bashir (2001) SCHIFF BASE COMPLEXES DERIVED FROM
SALICYLALDEHYDE WITH AMINE, [Ni(1,2-pn)2Cl2]·3H2O AND [Cu(1,2-pn)2]SO4·2H2O, AS COMPLEX LIGANDS, Synthesis and
Reactivity in Inorganic and Metal-Organic Chemistry, 31:6, 927-951, DOI: 10.1081/SIM-100105251
To link to this article: http://dx.doi.org/10.1081/SIM-100105251
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 31(6), 927±951 (2001)
SCHIFF BASE COMPLEXES DERIVED
FROM SALICYLALDEHYDE WITH
AMINE, [Ni(1,2-pn)2Cl2]Á3H2O AND
[Cu(1,2-pn)2]SO4Á2H2O, AS COMPLEX
LIGANDS
Saied M. E. Khalil,* Shaker L. Stefan,
and Khaled A. Bashir
Department of Chemistry, Faculty of Education, Ain
Shams University, Cairo, Egypt
ABSTRACT
Schi€ base complexes known as complex ligands were
prepared by the condensation of dichlorobis(1,2-diamino-
propane)nickel(II), [Ni(1,2-pn)2Cl2]ÁH2O, or bis(1,2-diamino-
propane)copper(II) sulphate, [Cu(1,2-pn)2]SO4ÁH2O, with
salicylaldehyde producing the Schi€ base complex ligands
[ML] (M ˆ Ni or Cu). The complex ligands [ML] act as
bidentate ligands through the bridged di-m-phenoxy oxygen
atoms. These Schi€ base complexes react with transition
metal ions yielding homo- and heteronuclear complexes
of the types [MLM0Cl2] or [(ML)2M0Cl2], [(ML)2M0]Cl2,
*Corresponding author. E-mail: smekhalil@yahoo.com
927
Copyright # 2001 by Marcel Dekker, Inc.
www.dekker.com

928
KHALIL, STEFAN, AND BASHIR
[(ML)2M0](ClO4)2 and [(ML)2M0(NO3)2](NO3)n, M ˆ Ni or
Cu; M0 ˆ Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II),
Ce(III) and Th(IV). The complexes were characterized by
elemental analyses, thermal analyses, IR, visible and ESR
spectra, magnetic susceptibility measurements as well as mass
spectra. Magnetic moments were altered by the introduction
of additional metal cations besides the one already present in
the complex ligands. The M0 cations were linked to the outer
1
2
phenoxo oxygen atoms in the [NiL] Á H2O and [CuL]ÁH2O
complex ligands. All homo- and hetero bi- and tri-nuclear
complexes show antiferromagnetic interactions which are
attributed to inter- or intramolecular interactions of the metal
cations. Mass spectra of the complex ligands and selected
homo- and hetero bi- and trinuclear complexes support the
formula weights of these complexes. Visible and ESR spectra
as well as magnetic moments indicated that the parent
mononuclear complex ligands [ML] have square-planar geo-
metry. The binuclear and trinuclear complexes have similar or
di€erent geometries, octahedral or square-planar. The octa-
hedral con®guration is completed by chlorine atoms, nitrate
groups and=or solvent molecules.
INTRODUCTION
Multimetallic complexes constitute an important part of modern
inorganic chemistry due to the nature of these compounds as active sites in a
variety of metalloenzymes1,2 and play a signi®cant and expanding role in
industrial catalysis3 and materials chemistry477. The experimental study of
multimetallic complexes dates backto 1704 with the discovery of Prussian
blue. The synthesis of complexes which contain two or more metal ions each
with appropriate complement of external ligands8 and one or more shared
entities are referred to as bridging groups in macrocyclic and macro-
acyclic9712
.
One e€ective method for the synthesis of macrocyclic complexes
involves the presence of a metal ion in the cyclization reaction. The metal
ion plays an important role in directing the reaction, and this e€ect has been
termed the metal-template e€ect. This reaction depends on the size of the
cation used as a template and the solvent employed in the condensation and
its purity13. In case of the larger Schi€ base macrocycles, transition metal
cations are ine€ective as templates. Consequently the use of alkaline earth,

SCHIFF BASE COMPLEXES
929
lanthanides and main group templating agents had enabled the generation
of the corresponding transition metal complexes through the transmetalla-
tion reaction14.
In this study, another method is reported for the synthesis of Schi€
base complexes from their corresponding amine complexes, known as
complex ligands (mononuclear complexes) abbreviated as [ML] where
M ˆ Ni(II) or Cu(II), shown in Fig. 1. It was found that the metal ions are
bonded to the N2O2 sites in the complex ligands. The complex ligands [ML]
react with
a
metal(II) chloride or perchlorate, M0Cl2ÁxH2O or
M0(ClO4)2Á6H2O, providing various products of homo- and hetero bi- and
trinuclear complexes. M0 occupies the O,O sites of the m-phenoxo oxygen
atoms of the ligands and completes the preferred geometry by chloride,
nitrate ions and=or solvent molecules.
Figure 1. Formation of the complex ligands.

930
KHALIL, STEFAN, AND BASHIR
EXPERIMENTAL
Materials
FeCl3Á6H2O, CoCl2Á6H2O,
MnCl2Á4H2O,
Co(ClO4)2Á6H2O,
NiCl2Á6H2O, CuCl2Á2H2O, Cu(ClO4)2Á6H2O, CuSO4Á5H2O, ZnCl2,
Ce(NO3)3Á6H2O, Th(NO3)4Á5H2O and UO2(NO3)2Á6H2O, 1,2-diaminopro-
pane, salicylaldehyde were BDH, Analar or Merckchemicals. The solvents
used were absolute and 95% ethanol, methanol, dimethylformamide
(DMF), acetone and diethyl ether. Concentrated hydrochloric and
nitric acids were used. These solvents and acids were reagent grade
chemicals.
Preparation of the Complex Ligands from Amine Complexes
1
2
Complex Ligand [NiL]Á H2O (2)
A solution of 8.25 g, 67.6 mmol of salicylaldehyde in ethanol was
added to 10 g, 33.8 mmol of the blue amine complex, [Ni(1,2-pn)2Cl2] in
ethanol15. The solution was re¯uxed for 3 h. The red solid nickel complex
was formed. The mixture was allowed to cool slowly to room tempera-
ture and collected by ®lteration, washed with ethanol then ether and
®nally air-dried. Yield 11.22 g, (95%). The complex is soluble in DMF.
The ®ltrate contained the soluble by-product (NH3CH2-CH(CH3)-
NH3)Cl2 as shown in Fig. 1. It was obtained by concentrating the ®ltrate
and ®ltering the white solid which was then air-dried. Yield 3.1 g,
(85.4%).
Complex Ligand [CuL]ÁH2O (16)
A solution of 2.25 g (18.5 mmol) of salicylaldehyde in ethanol was
added to 3 g (9.25 mmol) of the blue amine complex, [Cu(1,2-
pn)2]SO4ÁH2O, in ethanol16. The solution was re¯uxed for 3 h. The colour
of the solution changed from blue to deep violet and a white precipitate
appeared. The white precipitate was obtained by ®ltration and the ®lterate
was evaporated to near dryness then re®ltered to obtain the complex
ligand, [CuL]ÁH2O, washed with small amounts of ethanol then ether and
®nally air-dried. The yield was 2.45 g (74%). It was found that the white
precipitate is the amine sulphate (NH3CH2-CH(CH3)-NH3)SO4 according
to Fig. 1.

SCHIFF BASE COMPLEXES
931
Preparation of the Homo- and Heteronuclear Metal Complexes
A solution of the metal chloride, nitrate or perchlorate in ethanol was
added to the complex ligand dissolved in ethanol in the molar ratio 1:1. The
solutions were re¯uxed for 273 h on a water-bath. The solid metal complexes
were precipitated after cooling and collected by ®ltration, washed with etha-
nol, then ether and ®nally air-dried. The products of the reactions using metal
perchlorates were washed with water prior to washing with ethanol to insure
that the prepared complexes are not contaminated with the starting metal salt.
The following detailed preparation of the complexes are given as
examples, the other metal complexes were prepared similarly.
Preparation of [(NiL)2Co](ClO4)2 Complex (9)
An ethanolic solution (30 mL) of Co(ClO4)2Á6H2O (0.54 g, 1.48 mmol)
was added to an ethanolic solution (40 mL) of the complex ligand
1
[NiL]Á H2O (1 g, 2.96 mmol). The solution was re¯uxed for 2 h. On cooling
2
to room temperature, the formed precipitate was ®ltered, washed several
times with water, ethanol then ether and ®nally air-dried. Yield 1.2 g (87%).
Preparation of (NiL)2FeCl2]ClÁ4H2O, Complex (7)
An ethanolic solution (30 mL) of FeCl3Á6H2O (0.399 g, 1.48 mmol) was
1
2
added to 1.0 g (2.96 mmol) of the complex ligand [NiL]Á H2O dissolved in
40 mL of ethanol. The solution was re¯uxed for 3 h and a reddish-brown
precipitate appeared. The solution was allowed to cool to room tempera-
ture. The solid product was obtained by ®ltration, washed with ethanol then
ether and ®nally air-dried. Yield 0.757 g (56%).
Analyses and Physical Measurements
Electronic spectra of the metal complexes, as DMF solutions, were
recorded on a Jasco 550 spectrophotometer. IR spectra of the ligands and
their metal complexes, as KBr discs, were recorded on a Perkin-Elmer 598
spectrometer. Polystyrene was used as a calibrant. ESR spectra of the metal
complexes were recorded as polycrystalline samples at room temperature on
a JEOL microwave unit, JES-FE2XG spectrometer at the Central Labora-
tories, Tanta University, Tanta, Egypt. The magnetic ®eld was calibrated
with a 2,2-diphenyl-1-picrylhydrazyl sample purchased from Aldrich.

932
KHALIL, STEFAN, AND BASHIR
Magnetic susceptibilities of the complexes were measured by the Gouy
method at room temperature using a model MKI Johnson Matthey, Alfa
Products, UK, magnetic susceptibility balance. Hg[Co(SCN)4] was used as a
calibrant. Diamagnetic corrections were calculated from Pascal's constants.
E€ective magnetic moments were calculated from the expression
me€. ˆ 2.828 (wMT)1=2, where wM is the molar magnetic susceptibility cor-
rected for diamagnetism of the constituting atoms. Mass spectra of the
ligands were recorded on a Hewlett-Packard MS 5988 mass spectrometer at
the Microanalytical Center, Cairo University, Giza, Egypt. The fragmen-
tation was carried out at 300 ꢀC and 70 eV. TGA, DTG and DTA mea-
surements were carried out on a Shimadzu-50 thermal analyzer.
Microanalyses of carbon, hydrogen, nitrogen, sulfur and chlorine were
carried out at the Microanalytical Center, Cairo University, Giza, Egypt.
Analyses of metals were carried out on an Optima 3000 Perkin-Elmer
inductivity coupled plasma instrument (ICP).
RESULTS AND DISCUSSION
The complex ligands were synthesized by the condensation of an
ethanolic solution of salicylaldehyde with a suspension of the amine com-
plexes, [Ni(1,2pn)2Cl2]ÁH2O or [Cu(1,2pn)2]SO4ÁH2O, in ethanol.
The reaction of the complex ligands with various metal ions produce a
new series of either binuclear complexes such as [CuLFeCl3(H2O)]Á3H2O
and
[NiLUO2(NO3)]NO3
or
trinuclear
[(ML)2Ce(NO3)2]NO3,
complexes
such
as,
[(NiL)2FeCl2]ClÁ4H2O,
[MLZn2Cl4]ÁnH2O,
[(ML)2CdCl2]ÁnH2O, [(ML)2Th(NO3)2](NO3)2ÁnH2O, M ˆ Ni(II) or Cu(II).
The elemental analyses correspond to the formulae of the complexes given
in Table I. Examples of the reactions of the transition and actinide metal
salts with the complex ligands are indicated by the following equations:
2‰NiLŠ ‡ MnCl2 Á4H2O ! ‰ꢁNiL†2MnClꢁH2O†ŠClÁH2O ‡ 2H2O
2‰NiLŠ ‡ FeCl3 Á6H2O ! ‰ꢁNiL†2FeCl2ŠClÁ4H2O ‡ 2H2O
‰CuLŠ ‡ FeCl3 Á6H2O ! ‰CuLFeCl3ꢁH2O†ŠÁ3H2O ‡ 2H2O
2‰NiLŠ ‡ 2ZnCl2 ! ‰NiLZn2Cl4Š
2‰NiLŠ ‡ CeꢁNO3†3 Á6H2O ! ‰ꢁNiL†2CeꢁNO3† ŠꢁNO3† ‡ 6H2O
2
2‰CuLŠ ‡ CdCl2 ÁH2O ! ‰ꢁCuL†2CdCl2ŠÁH2O
2‰CuLŠ ‡ ThꢁNO3† Á5H2O ! ‰ꢁCuL†2ThꢁNO3† ŠꢁNO3† ‡ 5H2O
2
2
‰NiLŠ ‡ UO ꢁNO3†4 Á6H2O ! ‰NiLUO2ꢁNO3†ŠNO3 ‡ 6H2O
2
2

SCHIFF BASE COMPLEXES
933

934
KHALIL, STEFAN, AND BASHIR

SCHIFF BASE COMPLEXES
935

936
KHALIL, STEFAN, AND BASHIR
Characterization of the Complex Ligands
Elemental analyses, IR and electronic spectra as well as magnetic
moments indicated that the reaction of the amine complexes with salicy-
laldehyde yielded the complex ligands [ML] (M ˆ Ni(II) or Cu(II)) as shown
in Fig. 1.
IR spectra of the amine complexes showed the appearance of the NH2
stretching vibrations at 320073330 cmÀ1 and the NH2 degenerate deforma-
tion (scissor) at 164071650 cmÀ1, these bands disappeared after the con-
densation with salicylaldehyde and new bands appeared at 161571625 cmÀ1
attributed to the stretching vibration of the azomethine group, n(CˆN), in
addition to a band at 7607910 cmÀ1 assigned to the a-substituted phenyl ring.
It is worth noting that the reaction of the amine complex [Cu(1,2pn)2]-
SO4ÁH2O with salicylaldehyde in the molar ratio 1:4 yielded two products, the
®rst is the amine sulphate (H3N-CH2-CH(CH3)-NH3)SO4Á3H2O which is
soluble in cold water. The IR spectrum of this compound shows a broad band
at 3400 cmÀ1, attributed to n(OH) of water molecules, and another broad band
at 114071025 cmÀ1 which is assigned to the ionic sulfate group similar to that
observed in the starting amine complex, [Cu(1,2pn)2]SO4ÁH2O. The second
product was the complex ligand [CuL]ÁH2O
1
1
2
The HNMR spectrum of the diamagnetic complex ligand [NiL]Á H2O
did not show a signal due to the phenolic OH group which supports the
absence of the n(OH) frequency in its IR spectrum. These observations
support the route of the reaction as shown in Fig. 1 and excluded the
condensation of the four amino-groups with salicylaldehyde as previously
reported in the case of using 1,3-diaminopropane17.
Electronic and ESR Spectra and Magnetic Moments of the Complex
Ligands
The electronic spectra and the magnetic moments of the parent amine
complexes and complex ligands are shown in Table II. The complex ligands
showed two bands at 2807415 nm which would be assigned to p ? p*
transitions of the aromatic rings overlapping with the absorption due to the
azomethine groups.
A square-planar geometry for the Ni(II) and Cu(II) complex ligands,
1
1
[NiL]Á H2O and [CuL]ÁH2O, is suggested. [NiL]Á H2O is diamagnetic and
2
2
showed a band at 542 nm in its visible spectrum similar to that reported for
[Ni(acacen)]18 (acacen ˆ N,N0-ethylenebis(acetylacetoneimine). [CuL]ÁH2O
showed a band at 570 nm in its visible spectrum indicative of a square-
planar geometry19 and its magnetic moment is 1.81 B.M. which supports

SCHIFF BASE COMPLEXES
937

938
KHALIL, STEFAN, AND BASHIR

SCHIFF BASE COMPLEXES
939
this geometry and the visible spectral data are similar to that reported for
20
1
2
[Cu(acacen)] . TGA of the complex ligands, [NiL]Á H2O and [CuL]ÁH2O,
showed that they contain water molecules which were lost at 1007110 ꢀC.
The ESR spectrum of the cystalline copper complex ligand,
[CuL]ÁH2O, (Fig. 5), in the powder form has been recorded at room tem-
perature and exhibits a signal at g ˆ 1.81 and a shoulder at 1.84 which
indicates that the geometry around the Cu(II) ion is square-planar21.
Mass Spectra of the Complex Ligands
The mass spectra of the complex ligands showed that the parent peaks
compare well with their formula weights. The mass spectrum of the complex
ligand [CuL]ÁH2O (F.W. ˆ 361.9) is presented in Fig. 2. The parent peakat
m=e ˆ 343 compares well with the calculated formula weight of the anhy-
drous complex ligand [CuL] (F.W. ˆ 343.9).
Conductance of the Starting Amine Complexes and Their Complex
Ligands
The parent amine complexes showed high values of electrical con-
ductance (Table II). This agrees with the ionic nature of these compounds.
The magnetic moment of the parent amine complex, [Cu(1,2pn)2]SO4ÁH2O,
is 1.91 B.M. and its visible spectral band at 546 nm agrees with a square-
planar geometry of the [Cu(1,2-pn)2]2‡ cation. However, the Ni(II) complex
is expected to be octahedral with the two chloride ions coordinated to the
metal cation as indicated from the value of the magnetic moment
(2.61 B.M.) and its visible spectral band at 580 nm is due to an
3A2g ? 3T1g(F) electronic transition. Its conductance would thus be due to
the replacement of the chloride ions by DMF solvent molecules in the
complex. The complex ligands, [ML], are non-conducting which agrees with
their proposed molecular structures in Fig. 1.
Homo- and Heteronuclear Metal Complexes
1
2
The complex ligands [NiL]Á H2O and [CuL]ÁH2O have di-m-phenoxy
oxygen bridges which act as O,O coordinating sites. These complex ligands
can thus be used as chelating agents toward metal cations such as Mn(II),
Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ce(III), Th(IV) and UO2(VI). A
variety of bi- and trinuclear complexes were prepared.

940
KHALIL, STEFAN, AND BASHIR
Figure 2. The mass spectrum of the complex ligand [CuL].
The elemental analyses of the metal complexes in Table I are con-
sistent with the proposed structures in Figs. 3, 4 and 5. It was found that the
molecular formulas of the products are [MLM0Cl2], [(ML)2M0Cl2],
[(ML)2M0(NO3)2] and [(ML)2M0](ClO4)2.
IR Spectra
The IR spectra of the homo- and heteronuclear metal complexes
showed a shift of the phenolic n(C-O) to lower frequencies, ꢂ30 cmÀ1, as

SCHIFF BASE COMPLEXES
941
Figure 3. The proposed structures of homo- and heteronuclear metal complexes of
the complex ligands [ML].
Figure 4. The proposed structures of the binuclear complex (21) and trinuclear
complex (26).

942
KHALIL, STEFAN, AND BASHIR
Figure 5. The proposed structures of the heterotrinuclear metal complexes (10),
(11), (24) and (25).
compared to its location in the parent complex ligands. Such a shift is
expected in the case of complexes where m-phenoxy oxygen atoms bridge
other metal cations (M0).
The IR spectra of the complexes (9), (18) and (23) show the char-
acterestic strong and broad absorption band at 1060 cmÀ1 which is attrib-
uted to the non-coordinated ClOÀ4 ion22. The appearance of new bands
around 138071435 cmÀ1 in the IR spectra of the nitrato complexes con-
®rmed the monodentate nature of this group22.
The IR spectra of the UO2(VI) complex (14) shows a strong absorp-
tion band at 930 cmÀ1 which is assigned to the antisymmetric n3(OˆUˆO)
vibration.
The IR spectra of the complexes showed broad bands at
332073460 cmÀ1 which could be assigned to n(OH) of water molecules
associated with the complex formation. Also, the existence of new bands at
8407870 cmÀ1 and 6307660 cmÀ1 is attributed to d(H2O) and r(H2O),
respectively22, suggesting the presence of coordinated water molecules to the
metal ions.
Electronic and ESR Spectra and Magnetic Moments
of the Homo- and Heteronuclear Metal Complexes
Electronic spectra of the homo- and heteronuclear complexes were
measured in DMF and are given in Table II. The re¯ectance spectrum of the
homotrinuclear complex [(NiL)2NiCl2]Á2H2O (3), shows two bands at 761
3
and 424 nm. The band at 761 nm is due to the characteristic A2g ? 3T1g(F)
electronic transition in octahedral geometry for the middle Ni(II) ion (O2O2

SCHIFF BASE COMPLEXES
943
sites). The magnetic moment of the trinuclear complexes (3) at room tem-
perature is 2.6 B.M. supports this geometry and thus lower value may be due
to intermolecular interactions. The band at 424 nm assigned to d7d tran-
sitions in square-planar geometry for the inner Ni(II) ions (N2O2 sites). The
magnetic moment of the trinuclear complex (4) at room temperature is
2.0 B.M. which is consistent with the value for a combination of low-spin
and a high-spin nickel(II) centres. This behaviour is similar to that reported
for homodinuclear nickel(II) complexes23. The visible spectrum of the het-
erobinuclear complex [NiLCuCl2]ÁH2O (5) shows two bands at 848 and
585 nm due to d7d transitions of Cu(II) ions in a tetrahedral geometry and
the Ni(II) ion in a square-planar geometry, respectively. The magnetic
moment of this complex (5) is 1.84 B.M. due to the unpaired electron of the
Cu(II) ion while the nickel ion is spin-paired. These observations are similar
to those reported for heteronuclear Cu(II) and Ni(II) Schi€ base com-
plexes24,25
.
The visible spectra of the heterotrinuclear complexes (6) and (10)7(14),
show one d7d transition band at 5237534 nm which would be due to the
Ni(II) cation only similar to that observed for the complex ligand, the other
accompanying cations, Mn(II), d5, Zn(II) and Cd(II) d10, Ce(III), Th(IV)
and UO2(VI), do not interfere. The visible spectrum of the heterotrinuclear
complex [(NiL)2FeCl2]ClÁ4H2O (7) shows a charge transfer band at 500 nm
(e ˆ 2000) thus masking the Ni(II) absorption band.
1
2
The magnetic moment of the complex ligand [NiL]Á H2O is diamag-
netic, d8 system in square-planar geometry, so any magnetic moment of the
heteronuclear species should arise from the other coordinated metal ions via
the di-m-phenoxo bridges. Based on this assumption, the observed magnetic
moments of the heteronuclear complexes Ni(II)-Mn(II) (6) and Ni(II)-
Fe(III) (7), 5.9 and 6.1 B.M., are those expected for an isolated d5 system in
octahedral geometry, Fig. 3(b). Also, the observed magnetic moments of the
heteronuclear complexes Ni(II)-Th(IV) (11) and Ni(II)-UO2(VI) (14), 2.68
and 1.34 B.M., can be assigned to the distortion of the geometry of Ni(II)
from square-planar towards tetrahedral as a result of introducing the large
Th(IV) and UO2(VI) cations.
The visible spectra of the heteronuclear complexes [(NiL)2Co]Cl2 (8)
and [(NiL)2Co](ClO4)2 (9) show two d7d bands at 674 (e ˆ 728), 528
(e ˆ 444) and 677 (e ˆ 540), 532 (e ˆ 320) nm, respectively. The ®rst band
of each complex is attributed to d7d transition of the Co(II) ion in
tetrahedral geometry while the second band is due to a d7d transition of
the Ni(II) ion in square-planar geometry and similar to that of the
1
2
complex ligand, [NiL]Á H2O. The magnetic moments of the complexes (8)
and (9) are 4.6 and 3.83 B.M., respectively, while the expected values for
tetrahedral complexes are 4.474.8 B.M. The low value of the magnetic

944
KHALIL, STEFAN, AND BASHIR
moment of complex (9) would point to the fact that the geometry of
Co(II) is not purely tetrahedral and may tend towards square-planar
which complexes have lower magnetic moments (2.172.8 B.M.)26. The
visible spectra of the heterotrinuclear complexes [(CuL)2Co]Cl2Á5H2O (22)
and [(CuL)2Co](ClO4)2 (23) are 572 (e ˆ 386), 648 (e ˆ 250) and 572
(e ˆ 322), 650 nm (e ˆ 290), respectively. The ®rst band at 572 nm is similar
to that of the parent complex ligand [CuL]ÁH2O while the second band at
6487650 nm (e ˆ 2507290) is due to the Co(II) ion in tetrahedral geo-
metry. It was well known that the electronic spectra in an octahedral
Co(II) complexes, which are usually high-spin ones, lead to a weakband
(e < 10) near 500 nm while for tetrahedral complexes a much stronger
band (e < 100) at 6007700 nm is expected27. Magnetic moments and ESR
spectra support these geometries. The magnetic moments of the two
previous complexes are 4.94 and 4.1 B.M., respectively. These values
would indicate antiferromagnetic interaction between Cu(II)-Co(II) ions.
The ESR spectrum of [(CuL)2Co]Cl2Á5H2O (22) measured at room tem-
perature exhibits a signal with g ˆ 1.81, Fig. 6, similar to that observed
for the complex ligand [CuL]ÁH2O in square-planar geometry and other
signals at g ˆ 1.85, 1.89, 1.90, 1.91 and a shoulder at 1.93 attributed to
Co(II) in tetrahedral geometry. The splitting of the latter signal is due to
the interaction between the electrons and the 59Co nuclei which have a
nuclear spin I ˆ 7=2.
The visible spectra of the homotrinuclear complex (19) and the
heteronuclear complexes (20) and (24)7(27) show one absorption band
which would be due to the d7d transition of the Cu(II) cation as that
observed in the case of the complex ligand [CuL]ÁH2O, the other
accomanying cations, Mn(II), d5, Zn(II) and Cd(II), d10, Ce(III) and
Th(IV), do not interfere. The spectrum of [CuL3FeCl3(H2O)]Á3H2O (21)
shows bands at 525 and 475 nm, the former band was assigned to the
transition of the Cu(II) ion and is consistent with square-planar geometry
while the later band was assigned to the d7d transition of a Fe(III) ion
in an octahedral geometry26 (Fig. 4) which is achieved through the
chloride ions and a water molecule. The magnetic moment of the com-
plex is 5.6 B.M. which is lower than expected for Cu(II)-Fe(III) ions due
to strong antiferromagnetic interactions between the metal ions. The ESR
spectrum of the complex exhibits a signal with g ˆ 1.81 similar to that
observed for the complex ligand [CuL]ÁH2O in square-planar geometry
and another signal at g ˆ 1.84 and a shoulder at g ˆ 1.85 which are
attributed to Fe(III) ion.
The magnetic moment of the homotrinuclear complex [(CuL)2-
CuCl2]Á6H2O (19) is 2.81 B.M., and indicates antiferromagnetic coupling
which may be due to intermolecular and=or intramolecular interactions.

SCHIFF BASE COMPLEXES
945
Figure 6. ESR spectra of the parent amine complex, [Cu(1,2-pn)2SO4]ÁH2O (15);
the complex ligand [CuL]ÁH2O (16) and [(CuL)2Co]Cl2Á5H2O (22).

946
KHALIL, STEFAN, AND BASHIR
The visible spectra of the heterotrinuclear complexes [(CuL)2-
NiCl2]ÁH2O (17) and [(CuL)2Ni](ClO4)2 (18) show a single band at 570 nm
due to the overlap of the absorption bands of both Cu(II) and Ni(II) cations
in square-planar geometries. The values of the magnetic moments of these
complexes are 2.89 and 3.4 B.M., which is higher than the value expected for
the Cu(II) ion and suggest that the geometry of the Ni(II) ion is distorted
from square-planar towards tetrahedral.
Mass Spectra of Heteronuclear Metal Complexes
The mass spectra of the homo- and heteronuclear complexes provide
good evidence for the molecular formulas of these complexes. The hetero-
trinuclear complexes (7), (22), (20) and (21), [(NiL)2FeCl2]ClÁ4H2O (F.W.
912), [(CuL)2Co]Cl2Á5H2O (F.W. 907.7), [(CuL)2MnCl2] (F.W. 813.6) and
[CuLFeCl3(H2O)]Á3H2O (F.W. 578.1) as representative complexes, are
depicted in Figs. 7 and 8. The mass spectra of these complexes showed the
highest mass peaks at m=e 850, 817, 811 and 508, respectively, which agree
with the formula weights of the anhydrous complexes [(NiL)2FeCl2]Cl
(F.W. 840), [(CuL)2Co]Cl2 (F.W. 817.7), [(CuL)2MnCl2] (F.W. 813.6) and
[CuLFeCl3]Cl (F.W. 506.1). The fragmentation patterns of the former two
complexes show fragments at 338 and 343 due to the complex ligands [NiL]
and [CuL], respectively.
Conductance of the Homo- and Heteronuclear Metal Complexes
The molar conductance values (Table II) of the complex ligands
measured in DMF solutions lie in the range 6710 ohmÀ1 cmÀ2 molÀ1 sug-
gesting that they are non-electrolytes. The conductivity of the heteronuclear
complexes (7), (10), (14) and (24) are 62, 100, 50 and 62 ohmÀ1 cmÀ2 molÀ1
,
respectively, which suggest that these complexes are 1:1 electrolytes28. The
conductivity of the heterotrinuclear Ni(II)-Th(IV) (11) and Cu(II)-Th(IV)
(25) complexes are 201 and 200 ohmÀ1 cmÀ2 molÀ1, respectively, suggesting
that these complexes are 2:1 electrolytes. These results indicate that the
coordination geometry of both Ce(III) and Th(IV) is octahedral (Fig. 4).
Complexes (4), (9), (18) and (23) in Table II which contain two per-
chlorate anions showed lower values of conductivity, 38.57100 ohmÀ1
cm2 molÀ1, than those expected for 2:1 electrolytes. This would be due to the
bulky perchlorate anions which would have lower mobilities in their solutions.
On the other hand, the complexes that contain two chloride ions, (8) and (22),
are expected to have higher values of conductivity. However, their con-

SCHIFF BASE COMPLEXES
947
Figure 7. Mass spectra of the heterotrinuclear complexes [(NiL)2FeCl2]ClÁ4H2O (7)
and [(CuL)2Co]Cl2Á5H2O (22).

948
KHALIL, STEFAN, AND BASHIR
Figure 8. Mass spectra of heterotrinuclear complexes [(CuL)2MnCl2] (20) and
[CuLFeCl3(H2O)]Á3H2O (21).

SCHIFF BASE COMPLEXES
949
ductivities are 56 and 106 ohmÀ1 cm2 molÀ1, respectively, which indicate the
formation of ion-pairing in these solutions. The other complexes which con-
tain coordinated chloride ions are non-conducting or show a certain degree of
conductivity which would be due to their replacement by DMF solvent
molecules. Examples of the latter type are the complexes (3), (5), (6), (12), (13),
(17), (19), (20), (21), (26), (27) in Table II.
1
2
Its is worth noting that complex ligands similar to [NiL]Á H2O and
[CuL]ÁH2O previously have been used as chelating agents towards metal
cations29. However, the preparations of the present ligands are carried out
through a di€erent route and the products of the reactions of these complex
ligands with metal chlorides and perchlorates are new and to our knoweldge
have not been reported before. In addition, while the two types of complexes
in Fig. 2 have been previously reported, those of the type (b), Fig. 2, have
not been reported before. Besides, all the variety of the structures of the
complexes obtained in this workis quite obvious.
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Received August 17, 2000
Accepted March 30, 2001
Referee I: M. Lattman
Referee II: D. H. Williams