EL-BORAEY
niazide and the appropriate aldehyde in (1:1:1) mole ra-
nol/naphthol moiety, respectively [17]. The careful in-
vestigation of the spectra of the complexes and their
corresponding ligands indicated that:
tio. A precipitate was formed after stirring in air for 1 h.
Petroleum-ether (60–80) was added to assist a good pre-
cipitation. The precipitate obtained was filtered off,
washed subsequently by EtOH several times and dried
over CaCl2/P4O10. Elemental analyses (C, H and N)
were carried out at the microanalytical centre, Cairo
University, Egypt. Metal(II) contents were determined
by standard complexometric titration. KBr-IR spectra
were recorded using a Perkin-Elmer 1430 spectro-
photometer. Electronic spectra were measured in Nujol
mulls using a Perkin-Elmer Lambda-4B spectrophoto-
meter. Magnetic susceptibility measurements were car-
ried out at room temperature on a modified Gouy-type
magnetic balance, Herts SG8 5HJ England. Diamag-
netic corrections were calculated from the values given
by Selwood and Pascall’s constants [14]. The molar
conductivity measurements were done in DMF (10–3 M)
using a Tacussel conducometer type CD6N. The ther-
mal analyses (TG and DTA) were carried out using a
• The bands of νNH and amide II appear in the spec-
tra of both ligands and complexes at the same posi-
tion, confirming that NH moiety does not partici-
pate in the coordination. The observed minor shift
to lower frequency of δNH (amide II) for some
complexes may be due to its presence in chelate
system rather than the open system of the ligands.
• The bands of amide I, and νC=N (sometimes
screened by the strong band of pyridine/phenyl or
naphthyl rings at 1600 cm–1 are shifted to lower fre-
quency on complexation, due to their participation in
the mode of coordination. Cu(II) complex 2 is charac-
terized by the appearance of an additional strong
band at 1725 cm–1 due to ν(C=O) of ketoenamine tau-
tomer of phenolic ring of the tautomerism of the
Schiff’s base, the data suggest the presence of such
complex in a mixture of two tautomeric forms [18].
For HLIII, the δ(C–OH) of naphtholic skelton
at 1330 cm–1 and C–OH deformation of naphtholic
skelton at 690 cm–1 disappeared on complexation, con-
firming the deprotonation of naphtholic (OH) through
the coordination with metal ions. This was also con-
firmed by the observed shift of ν(C–O) of naphtholic
skelton from 1160 cm–1 (in the ligand) to 1140 cm–1 (in
the complexes). This behaviour was not observed in
the spectra of complexes of p-hydroxybenzaldehyde
moiety (LI), instead, the above three bands appear in
their normal positions. This indicates that HLIII be-
haves as monobasic tridentate ligand whereas LI be-
haves as a neutral bidentate ligand.
• For HLII, the spectra display two bands at 1330
and 1300 cm–1 due to δ(C–OH of the phenolic
skelton), two bands at 700 and 650 cm–1 (γC–OH)
and two bands at 1170 and 1130 cm–1 (νC–O). This
doublet nature of the peaks for each type is due to the
presence of two phenolic (–OH) substituents on the
phenyl ring [19]. On complexation, the two bands
at 1300 and 650 cm–1 of δ(C–OH) and (γC–OH) dis-
appeared, whereas the bands at 1330 and 700 cm–1
still present. This indicates that one phenolic –OH is
deprotonated (o-substituent) whereas the other one
does not (p-substituent). On the other hand, one of the
two νC–O of phenol (1170 cm–1) appears nearly in its
position as for the ligand, whereas the other shifts to
lower frequency, (from 1130 for ligand to 1090 cm–1
for complexes). This behaviour indicates that HLII
behaves as monobasic tridentate ligand and has free
p-OH group. Furthermore, the bands at 570–470,
460–420 and 340–305 cm–1 which are not present in
the spectra of the free hydrazones are assigned to
ν(M–O), ν(M–N) and terminal ν(M–Cl), respec-
tively [20]. The dimeric nature of the complexes was
Shimadzu DTA/TG-50 with
a heating rate of
10°C min–1, in presence of nitrogen atmosphere. The
flowing rate of N2 was 30 cm3 min–1.
Results and discussion
The prepared complexes are stable in air at room tem-
perature. Generally, they are sparingly soluble in most
organic solvents. Complexes 1–3 and 5 have an appre-
ciable solubility in hot DMF. The molar conductance
value of these complexes are considerably lower than
those of univalent electrolytes in that solvent, indicat-
ing coordination of the chloride ions [15]. Com-
plexes 4, 6–8 are sparingly soluble or insoluble in hot
DMF. This behaviour may be attributed to their
dimeric nature in the solid-state.
IR spectra
IR spectral data of the free Schiff’s bases and their
metal complexes are given in Table 2. The spectra of
ligands HLII and HLIII display a splitted band in the
range 3230–2600 cm–1 that is assigned to ν(OH---N) or
ν(NH---O) [16], which confirms the tautomerism in
these ligands. Ligand LI displays a medium band at
ca. 3230 cm–1 is assigned to νNH of secondary amide.
The spectra of all ligands display also bands in the re-
gions 1680–1650, 1630–1620, 1610–1580 and
1560–1550 cm–1 due to amide I, ν(C=N) (azomethine
of aromatic Schiff’s bases), ν(C=C) of pyridine/phenyl
or naphthyl rings and amide II, respectively [17]. The
bands at 1330–1290, 1170–1130 and 700–650 cm–1 are
assigned to δ(C–OH) of phenol or naphthol moiety,
ν(C–O) of phenol/naphthol moiety and γC–OH of phe-
340
J. Therm. Anal. Cal., 81, 2005