Spectroscopic, thermal and toxicity studies of some 2-amino - 3- cyano - 1, 5 -diphenylpyrrole containing Schiff bases copper (II) complexes

Article abstract of DOI:10.2478/s11532-010-0046-7

Two novel Schiff base ligands of 2-amino-3-cyano-1,5-diphenylpyrrole and salicylaldehyde (HL¹) or 2- hydroxy1-naphthylaldehyde (HL²) and their copper(II) complexes have been synthesized and characterized by elemental analyses, spectr

Full text of DOI:10.2478/s11532-010-0046-7

Cent. Eur. J. Chem. • 8(4) • 2010 • 820–833
DOI: 10.2478/s11532-010-0046-7
Central European Journal of Chemistry
Spectroscopic, thermal and toxicity studies of
some 2-amino - 3- cyano - 1, 5 –diphenylpyrrole
containing Schiff bases copper (II) complexes.
Research Article
Hanaa A. El-Boraeya*, Randa M. Abdel-Rahmanb, Ensaf M. Atiaa,
Khalid H. Hilmya
aDepartment of Chemistry, Faculty of Science, Menoufia University,
Shebin El-Kom 23511, Egypt
bDepartment of Pest Physiology, Plant Protection Research Institute,
Agricultural Research Center, Dokki 12611, Giza, Egypt
Received 5 December 2009; Accepted 8 March 2010
Abstract:Two novel Schiff base ligands of 2-amino-3-cyano-1,5-diphenylpyrrole and salicylaldehyde (HL1) or 2- hydroxy1-naphthylaldehyde
(HL2) and their copper(II) complexes have been synthesized and characterized by elemental analyses, spectral (UV–Vis, IR, EPR,
Mass (for ligands)), thermal (DTA-TGA) methods, magnetic and conductance measurements. IR results demonstrate the bidentate
binding of the Schiff base ligands involving azomethine nitrogen, phenolic or naphtholic oxygen and suggest the presence of HL2 and
complexes (1, 2, 4 and 8) in enolimine-ketonamine tautomeric forms in the solid state. The EPR spectral data of complexes (2, 5, 6)
show that the metal – ligand bonds have considerable covalent character. The thermal studies show that complexes (1, 2, 4 and 8) that
are present in enolimine-ketonamine tautomeric forms exhibit lower thermal stability. The effect of synthesized ligands (HL1, HL2) and
complexes (1, 5) were tested on the mortality of entomopathogenic nematodes (EPN) (Heterorhabditis bacteriophora and Steinernema
carpocapsae). The study shows that the mortality of the nematodes increased with increasing concentrations of copper(II) ion, ligands
and complexes. Copper(II) ion was the most toxic for EPN.
Keywords: Copper(II) complexes • EPR spectra • Schiff base ligands • Thermal analysis (DTA/TG) • Nematodes
© Versita Sp. z o.o.
In addition, copper(II) complexes possess a wide range
of biological activity and are among the most potent anti-
1. Introduction
viral, anti-tumor and anti-inflammatory agents; they also
Schiff bases have been extensively employed in the
understanding of molecular processes occurring in
biochemistry, materialscience, catalysis, encapsulation,
activation, transport and separation phenomena,
hydrometallurgy, etc. [1-5]. Schiff bases play an
important role in inorganic chemistry as they easily form
stable complexes with most transition metal ions. The
development of the field of bioinorganic chemistry has
increased the interest of Schiff base complexes, since it
has been recognized that many of these complexes may
serve as models for biologically important species [6-11].
play a central role in biological redox metal enzymes
like plastocyanin, hemocyanin, azurin, galactose
oxidase and others [12]. In recent years, considerable
interest has developed in copper complexes with
mixed donor ligands as structural models for the
active site of copper proteins [13,14] and, moreover,
copper is an essential micronutrient for feeding as
well as a cofactor of several enzymes involved in
oxidative metabolism like β-hydroxylases, quercetinase,
ceruloplasmine, cytochromoxidase, monoaminoxidase,
superoxydismutase,
ascorbic acid oxidase and
* E-mail: helboraey@yahoo.com
820

H. A. El-Boraey et al.
tyrosinase [15-17]. The catalytic role of these enzymes
is a two-step process, i.e., the reduction of Cu2+ ion
to Cu+ ion and the fixation of molecular oxygen [18].
The rutine-Cu(II) complex shows their higher activity
as antioxidants and anti-free radical agents than free
rutine [19-21]. A survey of the literature reveals that
no work has been carried out on the synthesis of metal
complexes with Schiff bases derived from 2-amino-3-
cyano-1,5-diphenylpyrrole. The present manuscript is
devoted to the synthesis, spectroscopic, thermal and
toxicity studies of new Schiff base ligands of 2-amino-
2.2. Analytical and physical measurements
The elemental analysis (C and H) were carried out at the
Micro Analytical Center, Cairo University, Giza, Egypt.
Copper(II) content in the complexes was determined
via iodometric method. Halide ions were determined
by Volhard’s method, and qualitative tests for chloride
in complex (5) indicated no chloride ions. The FT-IR
measurements were performed (4000-400 cm-1) in
KBr discs using Nenexeus-Nicolidite-640-MSA FT-IR,
Thermo-Electronics Co. The UV-Visible absorption
spectra were measured in both methanol and in Nujol
mullusing4802UV/Visdoublebeamspectrophotometer.
The EPR spectra were recorded using a Varian E-109C
model X-band spectrometer. The magnetic field
modulation frequency was 100 KHz and the microwave
power was around 10 mW. Mass spectra were recorded
at 70 eV and 3000C on an MS 5988 Hewlett-Packard
massspectrometer. Molarconductivitiesweremeasured
in methanol or acetonitrile solution of the complexes
(10-3 M) using Cyber Scan CON/510 Conductivity/
TDS/0C/F0 meterUmedic/Germany(EUTECH).Magnetic
susceptibilities of the complexes were measured by the
modified Gouy method at room temperature using a
Magnetic Susceptibility Johnson Matthey Balance. The
effective magnetic moments were calculated using the
relation μeff = 2.828(χmT)1/2 B.M., where χm is the molar
susceptibility corrected for diamagnetism of all atoms
in the compounds using Selwood [31] and Pascal’s
constants. Thermal analysis (DTA /TGA) were obtained
by using a Shimadzu DTA/TG-50 Thermal analyzer with
a heating rate of 10 0C min-1 in a nitrogen atmosphere
with a following rate of 20 mL min-1.
3-cyano-1,5-diphenylpyrrole
and
salicylaldehyde
(HL1) or 2-hydroxy1-naphthylaldehyde (HL2) and their
copper(II) complexes. Entomopathogenic nematodes
(Heterorhabditidae and Steinernematidae) have been
studied extensively for biological control of numerous
insect pests in a wide range of commodities [22,23] and
are promising alternatives to synthetic insecticides [24].
These nematodes are unique because they possess
many important traits: they are environmentally safe,
easy to apply, have a wide host range including the
majority of insect orders and families, kill insects within
24-48 h, and form a durable infective juvenile stage
which can persist in nature. In addition, they are safe
to vertebrates, plants and non-target organisms [25,26].
Also, they are compatible with many chemical pesticides
[27,28]. Many biotic and abiotic soil components affect
nematode activity; among them is copper(II) ion. Copper
is an essential element and required by all organisms.
However, elevated concentrations of copper in soils
are toxic and may result in a range of effects including
reduced biological activity and subsequent loss of
fertility [29]. Toxicity studies of Cu(II) ion, ligands and
complexes (1,5) on Heterorhabditis bacteriophora and
Steinernema carpocapsae juveniles were evaluated via
the effect of all tested materials on mortality of EPN.
For toxicity studies, one Egyptian Heterorhabditis
species and one imported Steinernema species were
used. The Heterorhabditis species was defined as
Heterorhabditis bacteriophora [32]. The Steinernema
species was Steinernema carpocapsae (ALL) strain
obtained from Germany.
2. Experimental Procedures
2.3. Preparation of the Schiff bases (HL1
and HL2)
2.1.Material
All organic compounds and solvents were purchased
from Fluka and Merck. The metal salts CuCl2•2H2O,
Cu(NO3)2•3H2O, Cu(CH3COO)2•H2O and CuBr2 were
obtained from Fluka and used for complex preparation
without further purification. 2-amino-3-cyano-1,5-
diphenylpyrrole was synthesized following the reported
procedures [30].
The Schiff base ligands were prepared by the
condensation of equimolecular amounts of 2-amino-
3-cyano-1,5-diphenylpyrrole
with
salicylaldehyde
(HL1) or 2-hydroxy 1- naphthylaldehyde (HL2) in
25 mL absolute ethanol and a trace amount of P4O10
was added. The resulting mixture was refluxed for
1-4 h. The solid products (yellow or orange for HL1 and
HL2, respectively), were filtered off, washed several
times with ethanol and vacuo dried over P4O10. (M.P =
210, 2220C for HL1, HL2, respectively).
821

Spectroscopic, thermal and toxicity studies
of some 2-amino - 3- cyano - 1, 5 –diphenylpyrrole
containing Schiff bases copper (II) complexes
2.4. Preparation of solid complexes
3.1. IR spectra
The solid complexes were prepared by mixing hot The mode of binding of both Schiff base ligands to the
alcoholic solutions of copper(II) salts (chloride, nitrate, copper(II) ion was elucidated by recording the IR spectra
acetate or bromide for complexes 1, 2, 3 and 4, of the complexes as compared with the spectra of the
respectively) with either HL1 or HL2 ligand under study free ligands (Table 2). The spectra of both free ligands
(1:1 molar ratio). The reaction mixture was magnetically HL1 and HL2 show strong bands at 1621 and 1620 cm−1
stirred for 3-8 days. Petroleum ether (60-80) was added (characteristics of the ν(C=N) (azomethine) stretching
to assist precipitation. The solid complexes were filtered mode for HL1 and HL2) respectively [12,36,37] indicating
off, washed several times with ethanol and vacuo dried. theformationoftheSchiffbases.Thesebandsareshifted
Attempts to prepare nickel(II) and cobalt(II) complexes towards lower frequencies in the spectra of all copper(II)
were unsuccessful.
complexes, 1585-1565 and 1615–1601 cm−1 compared
with the free Schiff bases indicating the involvement of
the azomethine nitrogen in chelation with the copper(II)
ion [38]. The broad band at 3422-3124 cm−1 in the
IR spectra of ligands HL1 and HL2 was assigned to
ν(O–H) (phenolic or naphtholic) of the aldehyde moiety
[39,40]. The observed low value of this band is due to
the intramolecular hydrogen bonding between the
hydrogen atom of the –OH group and the azomethine
nitrogen atom, ν(OH…N = C). This band was shifted to
lower frequencies in all copper(II) complexes (except
for complex 5), suggesting the involvement of the –OH
group in coordination. For complex 5, the ν(O–H) for
the ligand disappears, suggesting coordination through
deprotonated naphtholic oxygen. The Ar–O stretching
frequency appears as a strong band within the 1318-
1277 cm-1 as reported for similar ligands [41]. The Ar–O
stretching frequency is shifted to a lower frequency in
the 1310-1230 cm-1 which confirms the participation of
the oxygen atom of the aldehyde moiety in coordination
to the copper(II) ion. [36]. The coordination of the
azomethine nitrogen and phenolic or naphtholic oxygen
are further supported by the appearance of two peaks at
2.5. Preparation of the tested samples for
toxicity study
The hydrated copper(II) chloride (CuCl2•2H2O) was
dissolved in distilled water. Redistilled water was used
for the control. Ligands (HL1 and HL2) and complexes (1,
5) were dissolved in distilled water and dimethylsulfoxide
(DMSO) in a ratio of (1000 mL: 5 mL), respectively
at the following concentrations (1.5, 7.5, 11 mg L-1).
Redistilled water and DMSO were used for the control.
2.6. Toxicity study
The toxicity study was performed according to
Jawraska et al. [33].
2.7. Data analysis
Data expressed in percentages were transformed to
arcsinevaluestoensurenormality.Statisticalsignificance
was determined by analysis of variance (Duncan’s
multiple range tests and T- test to differentiate between
the means at P<0.05) using software package Costat
(Cohort Inc., Berkeley, CA, USA). Results are recorded
as mean ± standard deviation (SD) [34].
-1
663-564 cm and 540-409 cm-1 due to ν(Cu–O) and
ν(Cu–N) stretching vibrations [42,43] that are not
observed in the infrared spectra of the free ligands.
For HL2 ligand, new bands appear at 3300, 1677 and
1597 cm-1 attributable to ν(NH), ν(C=O) and δ(NH)
vibration modes, respectively, suggesting the presence
of the HL2 ligand in an enolimine-ketonamine tautomeric
interconversion form [40,44,45]. The lower value of
ν(C=O) is due to the intramolecular hydrogen bonding
between the hydrogen atom of the –NH group and the
oxygen atom of the naphtholic moiety, ν(NH…O = C)
(Scheme 1). The free ligands exhibit a strong band at
2213 cm-1, assigned to ν(C≡N) at the 3-position of the
pyrrole ring [46]. In all the copper(II) complexes, no
significant change was observed, symbolizing that the
cyano nitrogen was not involved in the coordination.
In addition, the presence of ν(C≡N) at the same
position rules out the possibility of its change to CO-
NH2 by promotion of water to the cyano group [47]. For
3. Results and Discussion
The ligands (HL1, HL2) and their copper(II) complexes
(Scheme 1) have been synthesized and characterized by
elemental analyses, molar conductivity measurements,
magnetic susceptibility measurements, EPR, mass
spectra (for ligands), electronic and IR spectral data
and thermal analysis (DTA/TGA). The complexes are
air stable, non- hygroscopic, soluble in MeOH and/or
CH3CN but insoluble in most common organic solvents,
and freely soluble in coordinating solvents such as
DMF, DMSO. TLC of the complexes and their elemental
analyses were satisfactory evidence for their purity. The
molar conductivity values (Table 1) of 10-3 M solution
indicate that the complexes are non-electrolytes [35].
822

H. A. El-Boraey et al.
Table 1.Color, elemental analysis and molar conductivity for ligands (HL1) and (HL2) and their copper(II) complexes
Analysis
Yield
Calc. (F) %
No
Compound
Color
ΛM•
Decomp.
Temp./ oC
(%)
C
H
M
HL1
84.1
Yellow
210m
100
80.00 (80.10)
4.68 (4.40)
ــ
ــ
1
[Cu (HL1)(Cl)2]
73.3
Brownish green
57.88 (58.37)
3.42 (3.00)
12.8 (12.9)
43.79•
2
3
4
[CuHL1(NO3)2]• H2O•EtOH
[Cu(HL1)(L1)2]
70.7
82.3
65.4
Brownish green
Brownish red
Dark green
131
310
151
50.77 (51.06
75.09 (76.40)
43.74 (43.76)
4.08 (4.00)
4.26 (4.30)
3.79 (3.88)
10.3 (10.1)
5.5 (5.9)
9.6 (9.9)
20.94•
3.22o
[Cu HL1(Br)2]•4H2O
18.87•
Orange
222m
270m
77.19 (77.60)
75.71 (74.42)
5.81 (5.70)
4.06 (4.29)
ــ
ــ
HL2•1.5 EtOH
[Cu(L2)2]
89.3
77.4
5
6
Dark green
7.2 (7.3)
5.55o
[Cu(HL2)(L2)NO3]
76.4
Brownish green
284m
70.69 (70.75)
3.89 (4.67)
6.7 (6.4)
3.18o
7
8
[Cu(HL2)(L2)(OAc)]
75.9
81.5
Dark brown
Dark brown
331m
95
73.45 (72.86)
50.05 (49.21)
4.22 (4.23)
3.74 (3.79)
6.7 (6.5)
9.1 (9.4)
3.49o
[CuHL2(Br)2]•2H2O•1/2 EtOH
15.29o
o
• Ohm-1 cm2 mol-1 in 10-3 M.sol.; • in MeOH; in CH3CN; m Melting
the complexes (1, 2, 4 and 8), the IR spectra show
additional bands at 3228-3196, 1680-1675 and 1618-
1581 cm-1 attributable to ν(NH), ν(C=O) and δ(NH)
vibration modes, respectively, suggesting the presence
of these complexes also in an enolimine-ketonamine
tautomeric interconversion form (Scheme 1), which is
further supported by their lower thermal stability (vide
thermal analysis). The IR spectra of the nitrato
complexes (2, 6) show bands due to NO3− stretching
vibrations at (1386-1369) cm−1 (ν5), (1298-1255) cm−1
(ν1), (1139-1052) cm−1 (ν2) and (836- 833) cm−1 (ν3).
The values of (ν5− ν1) i.e. (88,114) cm−1 suggest the
monodentate coordination of NO3− ions [21, 48-50]. The
cetate complex (7) shows bands at 1570 and 1369 cm-1
assigned to νas(OAc) and νs(OAc), respectively, with a
difference of 201 cm−1 indicating a monodentate manner
[51,52]. The spectra of some complexes show a very
broad band observed in the region between 3500-2905
cm-1 comprising of both –OH (aldehyde moiety, solvent)
and –NH stretching absorptions. Bands in the region
1585-1559 cm-1 are due to aromatic (C=C) stretching
absorption. From the IR spectra, we can conclude
that both Schiff base ligands act as monobasic or
neutral bidentate ligands, coordinating to copper(II) ion
through the oxygen of the aldehyde moiety and imine
nitrogen.
3.2. Mass spectroscopy
The EI mass spectra of free ligands, HL1, HL2
confirm their proposed formulae by showing a molecular
ion peak at 363 and 413 amu (calculated 363 and
413 amu), with an abundance of 80.1% and 80.01%
for HL1 and HL2 respectively, which coincides with their
formulae weight. Their proposed pathway fragmentation
pattern is depicted in Scheme 2.
3.3. Electronic
susceptibility
spectra
and
magnetic
The electronic spectra of the ligands in methanol and
their copper(II) complexes in mulls are summarized in
Table 2. The band at 475-460 nm in the spectrum of
HL2 ligand may be assigned to enolimine-ketonamine
tautomeric equilibria [44]. All the complexes show an
intense band in the 350–300 nm range which is assigned
to n-π* transition associated with the azomethine
linkage [53]. The spectra of the complexes show intense
bands at the high-energy region (in the 487–358 nm
range), which can be assigned to charge transfer. The
electronic spectra of Cu(II) complexes (1, 2, 4 and 8)
exhibit a broad band at 680-800 nm indicating square
planar geometry [52,54-56]. In the case of complex (3),
two transitions were observed at 740 and at 545-450 nm
823

Spectroscopic, thermal and toxicity studies
of some 2-amino - 3- cyano - 1, 5 –diphenylpyrrole
containing Schiff bases copper (II) complexes
CN HO
CN
N
CN
O
HO
Ph
N
N
HC
HL1
Ph
N
HC
Ph
N
N
H
C
H
Ph
Ph
Ph
HL2
Ketonamine
Enolimine
H
O
X
X
X
O
Cu
NC
Cu
NC
H
N
N
C
H
y
X
C
H
N
Ph
N
Ph
Ph
Ph
(1) = X = Cl
y = nill
(2) = X = NO3 y = H2O.EtOH
(4) = X = Br
y = 4H2O
Ph
CN
H
N
Ph
Ph
N
NC
C
O
C
H
N
O
H
Ph
N
Cu
Cu
NC
C
Ph
N
O
N
C
H
O
H
O
N
NC
N
C
H
Ph
N
Ph
N
Ph
NC
Ph
Ph
(5)
(3)
Ph
N
Ph
H
O
NC
C
X
N
H
Cu
N
C
H
O
NC
N
Ph
Ph
(6) = X = NO3
(7) = X = OAc
H
Br
O
N
Br
O
1
Cu
Cu
H
.
.2H2O
EtOH
2
Br
N
C
H
Br
N
C
H
NC
NC
Ph
N
Ph
Ph
Ph
(8)
Scheme 1. Suggested structures of the ligands (HL1, HL2) and their Cu(II) complexes (1-8)
824

H. A. El-Boraey et al.
Table 2.Infrared spectral bands (cm-1), magnetic moment (BM) and electronic spectral data (nm) for (HL1) and (HL2) ligands and their copper(II)
complexes.
No.
Compound
ν(OH) /
ν(H2O,EtOH)
µeff(BM)
(d-d)
transition
mulls(nm)
ν(C=N) δ(N-H) ν(M-O) ν(M←N)
ν
ν(C=O)
(N-H) (tout.)
HL1
3124(m)
-
-
1621(s)
-
-
-
-
-
1
2
[Cu (HL1)(Cl)2]
800, 520, 415, 370
3338
3204
3196
1680(s)
1680(s)
1582(sh)
1585(sh)
1618(s)
1618(s)
635(w)
643(sh)
540(sh)
460(w)
2.0
[Cu(HL1)(NO3)2]•
H2O•EtOH
3375, 2932
700, 510, 490, 480
740, 545,450
2.0
1.9
3100
3
4
[Cu(HL1)(L1)2]
-
-
1599(s)
-
663(w)
566(sh)
522(m)
409(sh)
800, 475,
455-400
[Cu( HL1)(Br)2]• 4H2O
3500-3414
3228
1675(sh)
1583(sh)
1614(s)
1.98
-
HL2•1.5 EtOH
3500-3422,
2905
3300
-
1677(m)
-
1620 (s)
1597(m)
-
-
-
-
5
6
[Cu(L2)2]
-
1615 (sh)
564(m)
502(m)
2.0
700, 480, 460
[Cu(HL2)(L2)NO3]
[Cu(HL2)(L2)(OAc)]
4000-3300
3400
-
-
1601(m)
-
565(m)
500(m)
2.0
900, 740, 620
7
8
-
-
1601(m)
1602(sh)
-
565(m)
583(w)
500(m)
495(sh)
2.0
1.9
910,729,580
680, 470-405
[Cu(HL2)(Br)2]•2H2O•
3413-3350,
2935
3200
1581(sh)
1679(w)
1/2 EtOH
(sh) shoulder; (s) strong; (m) medium; (w) weak
Table 3. EPR parameters of copper(II) complexes.
No.
Compound
g║
g┴
giso
G
A||
A┴
Aiso
g║/ A|| cm
α2
2
[CuHL1(NO3)2] •H2O•EtOH
2.18
2.05
2.09
3.67
190
25
112
0.774
80
80
5
6
[Cu(L2)2]
2.25
2.25
2.05
2.04
2.11
2.11
5
190
120
25
10
112
178
0.805
0.637
[Cu(HL2)(L2)NO3]
6.25
46.66
825

Spectroscopic, thermal and toxicity studies
of some 2-amino - 3- cyano - 1, 5 –diphenylpyrrole
containing Schiff bases copper (II) complexes
Table 4.DTA and TG data of the investigated copper(II) complexes.
Temp. /Co
Wt loss/ %
DTA
No.
Compound
Leaving species
Reaction
Calc.(F)
TGA
HL1
.-
200 -216*(Max=210)
216 - 800*•
-
-
c
216 - 624
100 (100)
gradual decomposition
d
2HCl
100 - 270•*
270 - 800•
100 - 230
230 - 800
at 800
14.5 (14.7)
69.5 (69.0)
16.0 (16.3) o
d
d
1
2
[Cu (HL1)(Cl)2]
gradual decomposition.
≡ CuO
27 – 110
110 - 130
131 – 550
at 550
7.5 (7.7)
2.9 (2.8)
b
c
EtOH
27 - 110*
110 - 130*
131 - 800•*
[CuHL1(NO3)2]•
H2O•EtOH
H2O
76.6 (76.2)
13.0 (13.3)o
d
gradual decomposition.
≡ CuO
310 - 450•*
450 - 730•
Pyrrole moiety(C18H12N3)
completion of the decomposition
process
310 - 450
450 - 650
23.5 (23.7)
68.9 (68.1)
[Cu(HL1)(L1)2]
d
d
3
4
at 650
7.6 (8.2)o
≡ CuO1.5
30 - 150*
151 - 370*
370-800•
30 -150
151- 370
370-1000
at 1000
10.9 (10.6)
12.3 (12.2)
55.0 (55.4)
21.8 (21.8)o
a
d
d
4H2O
HBr
[Cu HL1(Br)2]• 4H2O
gradual decomposition.
≡ CuBr
140 -160*
210 -230*max=222
231 -520•*
140-160
161-230
231 -520
520-713
-
-
c+ b
d
phase change
1.5 EtOH
pyrrole moiety(C17H11N3)
naphthyl moiety(C11H9O)
14.3 (14.3)
53.3 (53.3)
32.4 (32.4)
100 (100)
HL2•1.5 EtOH
520 -800•
d
203*
270 - 800*•
-
-
c
d
-
5
6
[Cu(L2)2]
270 - 800
64.8 (65.6)
decomposition
230 *
-
-
c
d
d
-
284 - 490•
491 - 700•*
284 - 490
491 - 680
at 680
54.1 (53.7)
32.7 (33.0)
13.2 (13.3)o
2 pyrrole moiety(C34H22N6)
2 naphthyl moiety(C22H15O2)
≡ Cu(NO3)
[Cu(HL2)(L2) NO3]
-
c
d
d
-
230 *
-
331 – 620
620 -760
at 760
2 pyrrole moiety(C34H22N6)
2 naphthyl moiety(C22H15O2)
≡ Cu(OAc)
7
8
[Cu(HL2)(L2)(OAc)]
331 - 550*•
550 - 760•*
54.3 (54.8)
32.8 (32.5)
12.9 (12.7) o
[CuHL2(Br)2]•2H2O•
1/2 EtOH + 2H2O
HBr
gradual decomposition.
≡ CuBr
26 - 94*
95 -200•
200 -800*
26 - 94
95 - 200
200 -800
at 800
8.5 ( 8.6)
11.6 (11.8)
59.3 (57.8)
20.6 (21.4) o
a + b
d
d
1/2 EtOH
* Endo; • Exo; o Final product percent; a Dehydration; b Desolvation; c Melting; d- decomposition, HL1= (C24H17N3O); HL2 = (C28H19N3O)
826

H. A. El-Boraey et al.
12
Conc. 1.5 mg/l
Conc. 7.5 mg/l
Conc. 11.0 mg/L
a
b
a
a
10
8
b
c
e
e
c
b
6
d
d
4
g
2
0
Copper (II) ion, Ligands and complexes
Figure 1. Mortality of Heterorhabditis bacteriophora after 48 h as a function of different concentrations of Cu(II) ion, ligands ( HL1,
complexes (1, 5).
HL2) and
18
Conc. 1.5 mg/l
Conc. 7.5 mg/l
Conc. 11.0 mg/l
a
16
14
12
10
8
a
b
a
c
b
d
e
d
c
c
b
c
6
4
d
2
0
Copper (II) ion,Ligands and complexes
Figure 2. Mortality of Heterorhabditis bacteriophora after 96 h as a function of different concentrations of Cu(II) ion, ligands ( HL1, HL2) and
complexes (1, 5).
indicating octahedral geometry [57,58]. The electronic normal for monomeric Cu(II) complexes with an S =
reflectance spectra of the copper(II) complexes (6, 7) 1/2 spin state and did not indicate anti-ferromagnetic
were analyzed to three Gaussian components which coupling of spin at this temperature. The slightly higher
were consistent with square-pyramidal copper(II) magnetic moment observed for some complexes could
complexes (Table 2). In the C4V symmetry the three be associated with spin-orbital contribution [61].
2
2
bands are assigned B1→2E1 (Δ1), B1→2B2 (Δ2) and
2B1→ 2A1 (Δ3) transition, respectively [59,60]. The room 3.4. Electron Paramagnetic Resonance (EPR)
temperature magnetic moments were measured for The X-band EPR spectra of copper(II) complexes (2,
all complexes and are summarized in Table 2. The 5, 6) have been recorded in the solid state at room
observed values (ranging from 1.98 to 2.0 BM) are temperature. The various Hamiltonian parameters have
827

Spectroscopic, thermal and toxicity studies
of some 2-amino - 3- cyano - 1, 5 –diphenylpyrrole
containing Schiff bases copper (II) complexes
7
6
5
4
3
2
1
0
a
Conc. 1.5 mg/l
Conc. 7.5 mg/l
Conc. 11.0 mg/l
a
a
b
d
b
Copper (II) ion, Ligands and complexes
Figure 3. Mortality of Steienernema carpocapase after 48 h as a function of different concentrations of Cu(II) ion, ligands ( HL1, HL2) and
(1, 5).
complexes
9
a
Conc. 1.5 mg/l
Conc. 7.5 mg/l
Conc. 11.0 mg/l
8
7
6
5
4
3
2
1
0
a
a
c
d
c
d
Copper (II) ion, Ligands and complexes
Figure 4. Mortality of Steienernema carpocapase after 96 h as a function of different concentrations of Cu(II) ion, ligands ( HL1, HL2) and
complexes (1, 5)
The columns followed by the same letter are not significantly different but the columns followed by different letters
are significantly different (P=0.05) according to the Duncan multiple-range test (Figs.1-4).
828

H. A. El-Boraey et al.
HO
HC
CN
N
Ph
N
C N
N
Ph
C N
M/Z = 363
HL1
N
Ph
N
Ph
Ph
M/Z = 181
M/Z = 243
+
M/Z = 77
C N
HO
Ph
N
N
C
H
Ph
M/Z = 413
HL2
C N
N CH
C
H
Ph
N
Ph
M/Z = 270
M/Z = 140
+
N
Ph
M/Z = 77
M/Z = 140
Scheme 2. The fragments observed in mass spectra of HL1 and HL2.
829

Spectroscopic, thermal and toxicity studies
of some 2-amino - 3- cyano - 1, 5 –diphenylpyrrole
containing Schiff bases copper (II) complexes
been calculated [62,63] (Table 3). In all complexes, this peak may be assigned to an enolimine-ketonamine
the g|| values are less than 2.3 with the trend g|| tautomeric equilibria. The DTA curve shows a second
> g┴ > 2.0023. This result shows that the complexes endo peak at 2220C, with mass loss (estimated mass
are largely covalent [64] and that the dx2-y2 is in the loss 14.3%; theoretical 14.3%) This result is in good
ground state with d9 [Cu2+] configuration i.e (eg)4, agreement with the loss of one and a half molecules of
(a1g)2 (b2g)2 (b1g)1. Further, the values are consistent with ethanol per ligand molecule along with the melting point
Cu-N and Cu-O bonded copper complexes [65]. The of the organic ligand. These results are in accordance
empirical factor F = g||/A|| cm values were considered with the composition of the ligand determined by
as a diagnostic of stereochemistry. The g||/A|| cm ratios elemental analysis and IR spectroscopy. The Schiff
for complexes (2, 5) in this study (112 cm) are within the base ligand HL2 refers to two stages of mass loss
105–135 cm range seen for square planar complexes at the temperature range between 231–7130C. These
[66]. On the other hand, the ratio calculated is stages involved mass loss of 100.0% (found 100.0%)
178 cm for complex (6) which lies within the range 150- for the first and second steps of decomposition,
250 cm expected for tetragonal distorted complexes. respectively. These mass losses may be due to the
Apart from this, the covalency parameter (α2) has been successive losses of C28H19N3O molecule as gases at
calculated using Kivelson and Neiman equations [67]. the given temperature range.
The covalency parameter (α2 = 0.805 – 0.637) indicates
considerable covalent character for the metal–ligand 3.5.2. Complexes
bond [68]. The giso values and the geometric parameter The thermal analysis data are presented in Table 4.
G, i.e., the measurement of exchange interaction The correlations between the different decomposition
between the copper centers were evaluated by using steps of the complexes with their corresponding mass
the expressions:
loss are discussed in terms of the proposed formulae
of the complexes. DTA curves of complexes (2, 4, 8)
are generally characterized by endothermic peaks in the
temperature range of 26–150°C, assigned to loss of
solvents for crystallization, which results from TG mass
loss in that temperature range. The lower and wide
range of temperature of desolvation indicates that,
the solvents of crystallization are physically bound
[69-72]. As shown from DTA curves, the desolvation
process was followed by other asymmetric endo and/
or exothermic peaks, that are assigned to material
decomposition, as indicated from TG mass loss
g
2g
g
_
+
2.003
2.003
I
-
II
II
g
,
=
G=
iso
g
_ -
3
I
The complexes in the present study show the
value of G = 3.67-6.25, which indicates no effective
interaction. Thus, based on the spectral and analytical
data (Table 1,2,3), tentatively proposed structures
of the ligands and their copper(II) complexes are
depicted in Scheme 1.
3.5. Thermal analysis
The thermal properties of the studied ligands HL1, in that temperature range. The thermal behavior
HL2 and their copper(II) complexes were investigated of complexes (1, 2, 4 and 8) that are present in the
by thermogravimetric analysis (TGA) and differential enolimine-ketonamine tautomeric forms are almost the
thermal analysis (DTA), under nitrogen atmosphere from same, and the DTA/TGA curves are very similar to each
25 to 8000C; important data are summarized in Table 4. other and display a lower thermal stability (95-1510C).
The lower thermal stability of these complexes may
3.5.1.Ligands HL1, HL2
be due to the pseudo removal of the aromaticity
For the Schiff base ligand HL1, the DTA curve of the phenolic or naphtholic moiety in the ketonamine
shows an endothermic peak at 2100C due to the form and confirms the presence of these complexes
melting of the organic ligand. It can be seen that in enolimine-ketonamine tautomeric forms. As the
the TGA curve of HL1 shows no mass loss up to 2160C, temperature is increased, the DTA /TGA curves exhibit a
indicating the absence of water molecule and/or any gradual decomposition over a large temperature range.
other adsorptive solvent molecules. The thermogram The thermal behavior of the complexes (3, 5-7) are also
shows one decomposition step that begins at 2160C almost the same; the DTA/TGA curves are very similar
with a total mass loss of 100.0% (found 100.0%). This to each other and display one or two decomposition
mass loss may be due to the successive losses of steps with a higher thermal stability (270-3310C). The
C24H17N3O molecule as gases at the given temperature higher thermal stability of HL1 complex (3) (3100C)
range. The DTA curve of Schiff base ligand HL2 shows may be due to the presence of three six membered
a weak endothermic peak at 1500C, and the TGA chelate rings around Cu(II) ion. For HL2 complexes (5-7),
thermogram shows no mass loss at that temperature; the observed higher thermal stability may be due to the
830

H. A. El-Boraey et al.
presence of two six membered chelate rings in each concentration in HL1 (Fig. 3). For HL2, the toxicity started
complex. Complex (5) is thermally less stable (2700C) only at higher concentrations. All the tested complexes
than the nitrato complex (6) which in turn thermally less (1, 5) have no effect on mortality on S. carpocapsae
stable (2840C) than the cetate complex (7) (3310C). This (Fig.3). The same rank of mortality at 48 h occurred at
reflects the effect of the type and the presence of the 96 h with increasing values of percent mortality of the
anions on the thermal stability of complexes. The final nematode juveniles (Fig. 4). The increased mortality
solid thermoproduct was examined by IR spectroscopy of S. carpocapsae observed for Cu(II) ion at high
and it is likely to be CuO for complexes (1, 2), CuO1.5 concentration occurred randomly in nature. Unlike the
for complex (3), CuBr for complex (4, 8), Cu(NO3) for finding of Jaworska et al. [33] in which H. bacteriophora
complex (6), and Cu(OAc) for complex (7).
was more resistant than S. carpocapsae to copper(II)
ions, the reverse was found in the present study
where S. carpocapsae was more resistant to Cu(II)
ion, ligands and complexes than H. bacteriophora. An
elevated copper(II) ion concentration has been shown
to reduce beneficial mycorhizal association [73]. Also,
it has been noted that earth worms exhibit chronic toxic
responses at relatively low concentrations of copper
(<4-16 mg kg-1) [74].
3.6. Toxicity study
The effect of the tested copper(II) ion, ligands and
complexes (1, 5) on Heterorhabditis bacteriophora
mortality after 48 h were highly variable. The Cu(II) ion
followed by HL2 appeared to be toxic for H.bacteriophora
juveniles. The mortality of the nematodes increased and
the increase was gradual with increasing concentrations
for all the tested materials except for complex (1),
where a sharp increase in mortality was cleared from
median concentration to high concentration. At low
concentration, Cu(II) ion appeared to be the most toxic
for the nematode juveniles followed by HL2, complex
(5), then HL1. Complex (1) showed no toxicity at low
and median concentration but toxicity appeared at high
concentration. The rank of toxicity slightly differed at
higher concentrations. Cu(II) ion also scored the highest
toxicity followed by HL2, HL1, complex (5) then complex
(1) (Fig. 1). The percent mortality of the juveniles
increased at 96 h of exposure to Cu(II) ion, HL2, HL1,
complex (5) and complex (1) with the same rank of
48 h (Fig. 2) .
4. Conclusions
Novel copper(II) complexes of bidentate Schiff base
ligands obtained by the condensation of salicylaldehyde
or 2-hydroxy-1-napthaldehyde with 2-amino-3-cyano-
1,5-diphenylpyrrole have been isolated and studied. As
demonstrated from IR spectroscopy, complexes (1, 2,
4, 8) are present in enolimine-ketonamine tautomeric
form and thermal analysis shows that these complexes
have lower thermal stability. EPR spectral data of
complexes (2, 5, 6) indicate that the metal-ligand bonds
have considerable covalent character. The toxicity
study results indicate that copper pollutants affect
nematode density and biological activity in the natural
environment, but combinations of copper with ligands to
form complexes reduce this harmful effect.
For Steinernema carpocapsae at 48h, Cu(II) ion
was the only toxic species for the juveniles at low
concentration. This toxicity increased with increasing
concentrations. The mortality appeared at the median
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