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Spectrochimica Acta Part A 74 (2009) 1100–1106
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, structural characterization, thermal and electrochemical
studies of mixed ligand Cu(II) complexes containing
2-phenyl-3-(benzylamino)-1,2-dihydroquinazoline-4-(3H)-one
and bidentate N-donor ligands
V.A. Sawant, B.A. Yamgar, S.K. Sawant, S.S. Chavan ∗
Department of Chemistry, Shivaji University, Kolhapur (MS) 416 004, India
article info
Article history:
Received 4 March 2009
Received in revised form 7 August 2009
Accepted 12 September 2009
Keywords:
Mixed ligands
Quinazoline derivatives
Ethylenediamine
1,10-Phenanthroline
Thermal analysis
Cyclic voltammetry
abstract
Some mixed ligand Cu(II) complexes of the type [Cu(L)(en)X2](1a–3a), [Cu(L)(en)](ClO4)2(4a),
[Cu(L)(phen)X2](1b–3b) and [Cu(L)(phen)](ClO4)2(4b) [where L= 2-phenyl-3-(benzylamino)-1,2-
dihydroquinazoline-4-(3H)-one; en = ethylenediamine; phen = 1,10-phenanthroline; X = Cl−,N
3−and
NCS−] have been prepared. The complexes were characterized on the basis of elemental analysis, molar
conductance, magnetic moment, IR, UV–vis, mass, ESR and thermal studies. On the basis of electronic
spectral data and magnetic susceptibility measurement octahedral geometry has been proposed for
1a–3a and 1b–3b and square-planer geometry for 4a and 4b. The ESR spectral data of complexes
provided information about their structure on the basis of Hamiltonian parameters and degree of cova-
lency. The electrochemical behaviour of mixed ligand Cu(II) complexes was studied which showed
that complexes of phen appear at more positive potential as compared to those for corresponding en
complexes.
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
The studies of Cu(II) complexes have been widely explored for
the versatility of their coordination geometries, exquisite colours,
technical application dependent molecular structures, spectro-
scopic properties and their biochemical significance. Octahedral
Cu(II) complexes of ligands containing mixed electron donors have
been studied extensively due to their potential applications as
molecular materials [1–4]. In recent years considerable research
efforts have been focused on the synthesis and properties of
Cu(II) complexes of hybrid ligands because they can provide new
materials with useful properties such as magnetic exchange [5,6],
electrical conductivity [7], photoluminescence [8], nonlinear opti-
cal property [9] and antimicrobial activity [10]. Among the various
ligands quinazolines have received much more attention over the
past few years. Due to presence of pyrimidine nucleus in these
compounds they often shows very interesting biological and phar-
maceutical activities especially anti-inflammatory, anticonvulsant,
diuretic, antihypertensive, hypnotic, anti-malarial, antibacterial,
etc. [11–17]. Recently, the quinazolines have been found to possess
∗Corresponding author. Tel.: +91 231 2609164; fax: +91 231 2691533.
E-mail address: sanjaycha2@rediffmail.com (S.S. Chavan).
potent phosphodiesterase inhibitory activity, which is potentially
useful in the treatment of asthma [18]. They can form different
types of coordination compounds with transition metal ion due
to the several electron-rich donor centers with unusual structural
and chemical properties [19,20]. Because of the wide utility of
quinazoline derivatives in biological and pharmaceutical activi-
ties and its ability to act as polyfunctional ligand, many studies
on its metal complexes have been carried out [21–25]. Ethylene-
diamine and 1,10-phenanthroline chelators also act as potential
anti-tumor agents and they can show better anti-tumor activity if
they form water soluble neutral complexes with transition metal
ions [26,27].
Therefore, in continuation of our earlier work on structural
characterization of mixed ligand transition metal complexes
containing quinazoline ligands [28], here we report the syn-
thesis and characterization of mixed ligand Cu(II) complexes
derived from 2-phenyl-3-(benzylamino)-1,2-dihydroquinazoline-
4-(3H)-one (L) as primary ligand and ethylenediamine (en)or
1,10-phenanthroline (phen) as coligands. The complexes pre-
pared were characterized particularly by elemental analysis,
conductance, magnetic moment and spectral studies (IR, UV–vis,
mass and ESR). The relative thermal stabilities of the com-
plexes and their electrochemical behaviour have also been
discussed.
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.09.015
V.A. Sawant et al. / Spectrochimica Acta Part A 74 (2009) 1100–1106 1101
2. Experimental
2.1. Materials and methods
All chemicals used were of the analytical reagents grade (AR)
and of highest purity available. 2-Amino-benzoylhydrazide was
prepared by reported method in literature [29]. Microanalysis (C,
H and N) was performed on a Thermo Finnegan FLASH EA-112
CHNS analyzer. Electronic spectra were recorded on a Shimadzu
UV–visible NIR spectrophotometer. Molar conductance (M)was
measured on the ELICO (CM-185) conductivity bridge using ca.
10−3M solution in DMF. Magnetic susceptibility was measured on
Gouy balance at room temperature using Hg[Co(SCN)4] as calibrant.
Infrared spectra were recorded on PerkinElmer FT-IR spectrom-
eter as KBr pellets in the 4000–400 cm−1spectral range. Mass
spectra were measured on GCMS Shimadzu-2010. The ESR mea-
surements were performed in solid state at room temperature and
in solution at 77 K, on Varian E-112 spectrometer using TCNE as the
standard. Thermal analysis of the complexes was carried out on a
PerkinElmer thermal analyzer in nitrogen atmosphere at a heating
rate of 10 ◦C/min. Cyclic voltammetry measurements were per-
formed with Electrochemical Quartz Crystal Microbalance CHI-400.
A standard three electrode system, consisting of Pt disk working
electrode, Pt wire counter electrode and Ag/AgCl reference elec-
trode containing aqueous 3 M KCl were used. All potentials were
converted to SCE scale.
2.2. Synthesis of
2-phenyl-3-(benzylamino)-1,2-dihydroquinazoline-4-(3H)-one
(L)(Fig. 1)
2-Phenyl-3-(benzylamino)-1,2-dihydroquinazoline-4-(3H)-
one (L) was prepared by adopting and modifying the method
described in literature [30]. An intimate mixture of 2-amino
benzoylhydrazide (1 mmol, 0.151g) and benzaldehyde (2 mmol,
0.212 g) was suspended in ethanol (20 ml) and the mixture was
refluxed for 2 h. The separated solid was collected by filtration,
washed with ethanol and dried in vacuo to give the yellow product.
LYield 86%; mp 166 ◦C; Anal. found. C, 76.68; H, 4.87; N,
13.17 Calcd. for C21H17 N3O; C, 77.03; H, 5.23; N, 12.84; IR (KBr,
cm−1): (NH) 3283, (C O) 1660, (HC N) 1618; 1H NMR(CDCl3)
(400 MHz): ı9.22 (s, HC N), ı6.69–7.97 (m, Ar–H), ı6.29 (d,
C–H), ı4.89 (s, NH); mass spectrum: m/z= 327 (C21 H17N3O)+, 223
(C14H11 N2O)+, 119 (C7H5NO)+, 104 (C7H4O)+,77(C
6H5)+.
2.3. Synthesis of mixed ligand complexes
2.3.1. Copper(II) chloride complexes (1a and 1b)
To a methanolic solution (5 ml) of CuCl2·2H2O (1 mmol, 0.170 g),
a methanolic solution of ligand L(5 ml) (1 mmol, 0.327 g) was added
followed by addition of en (1 mmol, 0.060 g) or phen (1 mmol,
0.198 g) while stirring. The resultant mixture was refluxed for 3 h.
The product obtained was filtered, washed with methanol and
dried under vacuum over CaCl2.1a Yield 64%; mp 246 ◦C; Anal.
found: C, 52.38; H, 4.37; N, 13.17; Calcd. for C23H25 N5OCl2Cu: C,
52.93; H, 4.83; N, 13.42; IR (KBr, cm−1): (NH) 3298, (NH2) 3233,
3298, (C O) 1609, (HC N) 1589, (Cu–N) 529, (Cu–O) 468; m
(DMF, −1cm2mol−1): 12.76; UV–vis (DMF, max nm): 670; mass
spectrum: m/z= 522 [C23H25N5OCl2Cu]+, 368 [C11 H15N5OCl2Cu]+,
297 [C11H15 N5OCu]+, 124 [C2H8N2Cu]+; magnetic moment: B,
1.89. 1b Yield 67%; mp > 300 ◦C; Anal. found: C, 61.34; H, 3.49; N,
11.21; Calcd. for C33H25 N5OCl2Cu: C, 61.70; H, 3.92; N, 10.91; IR
(KBr, cm−1): (NH) 3310, (C O) 1620, (HC N) 1576, (Cu–N)
531, (Cu–O) 465; m(DMF, −1cm2mol−1): 27.49; UV–vis (DMF,
max nm): 666; mass spectrum: m/z= 642 [C33 H25N5OCl2Cu]+, 488
[C21H15 N5OCl2Cu]+, 376 [C20H14 N3OCu]+, 244 [C12H8N2Cu]+; mag-
netic moment: B, 1.81.
2.3.2. Copper(II) azido complexes (2a and 2b)
To a methanolic solution (5 ml) of Cu(NO3)2·6H2O (1 mmol,
0.240 g), a methanolic solution of L(1 mmol, 0.327 g) was added
while stirring. To this, a methanolic solution (5 ml) of en (5 ml)
(1 mmol, 0.060 g) or phen (1 mmol, 0.198 g) was added, followed
by the addition of NaN3(1 mmol, 0.130 g) in warm methanol. The
resultant mixture was refluxed for 3 h. The solid product obtained
was filtered, washed with methanol and dried under vacuum over
CaCl2.
2a Yield 64%; mp 230 ◦C; Anal. found: C, 51.23; H, 4.19; N,
28.34; Calcd. for C23H25 N11OCu; C, 51.63; H, 4.71; N, 28.80;
IR (KBr, cm−1): (NH) 3292, (NH2) 3236, 3292, (C O) 1613,
(HC N) 1578, (N3) 2059, 1354, (Cu–N) 531, (Cu–O) 472;
m(DMF, −1cm2mol−1): 33.33; UV–vis (DMF, max nm): 668;
mass spectrum: m/z= 536 [C23 H25N11 OCu]+, 451 [C23H25 N5OCu]+,
256 [C10H14 N3OCu]+, 124 [C2H8N2Cu]+; magnetic moment: B,
1.83. 2b Yield 67%; mp > 300 ◦C; Anal. found: C, 60.13; H, 3.47;
N, 23.87; Calcd. for C33H25 N11OCu; C, 60.50; H, 3.85; N, 23.52;
IR (KBr, cm−1): (NH) 3292, (C O) 1607, (HC N) 1587, (N3)
2057, 1343, (Cu–N) 535, (Cu–O) 476; m(DMF, −1cm2mol−1):
16.69; UV–vis (DMF, max nm): 680; mass spectrum: m/z= 655
[C33H25 N11OCu]+, 571 [C33 H25N5OCu]+, 376 [C20 H14 N3OCu]+, 244
[C12H8N2Cu]+; magnetic moment: B, 1.79.
2.3.3. Copper(II) isothiocynate complexes (3a and 3b)
A methanolic solution (5 ml) of ligand L(1 mmol, 0.327 g) was
added drop wise to a solution (5 ml) of Cu(NO3)2·6H2O (1 mmol,
0.240 g) in the same solvent followed by addition of en (1 mmol,
0.060 g) or phen (1 mmol, 0.198 g) and NH4NCS (1 mmol, 0.152 g)
in warm methanol. The resultant mixture was refluxed for 3 h. The
product obtained was filtered, washed with methanol and dried
under vacuum over CaCl2.
3a Yield 66%; mp 238 ◦C; Anal. found: C, 52.47; H, 4.21; N, 17.61;
Calcd. for C25H25 N7OS2Cu: C, 52.94; H, 4.44; N, 17.25; IR (KBr,
cm−1): (NH) 3294, (NH2) 3243, 3294, (C O) 1609, (HC N)
1573, (NCS) 2073, 762, 488, (Cu–N) 529, (Cu–O) 471; m
Fig. 1. Scheme of preparation of ligand L.
1102 V.A. Sawant et al. / Spectrochimica Acta Part A 74 (2009) 1100–1106
(DMF, −1cm2mol−1): 26.51; UV–vis (DMF, max nm): 660; mass
spectrum: m/z= 567 [C25 H25N7OS2Cu]+, 451 [C23 H25N5OCu]+, 256
[C10H14 N3OCu]+, 124 [C2H8N2Cu]+; magnetic moment: B, 1.89.
3b Yield 68%; mp > 300 ◦C; Anal. found: C, 60.87; H, 3.36; N, 14.58;
Calcd. for C35H25 N7OS2Cu; C, 61.16; H, 3.67; N, 14.27; IR (KBr,
cm−1): (NH) 3285, (C O) 1616, (HC N) 1578, (NCS) 2079,
767, 485, (Cu–N) 530, (Cu–O) 474; m(DMF, −1cm2mol−1):
38.40; UV–vis (DMF, max nm): 662; mass spectrum: m/z= 687
[C35H25 N7OS2Cu]+, 571 [C33H25 N5OCu]+, 376 [C20H14 N3OCu]+, 244
[C12H8N2Cu]+; magnetic moment: B, 1.87.
2.3.4. Copper(II) perchlorate complexes (4a and 4b)
To a methanolic solution (5 ml) of Cu(ClO4)2·6H2O (1 mmol,
0.370 g), a methanolic solution of L(5 ml) (1 mmol, 0.327 g) was
added followed by addition of en (1 mmol, 0.060 g) or phen
(1 mmol, 0.198 g) while stirring. The resultant mixture was stirred
for 3 h. The product obtained was filtered, washed with methanol
and dried under vacuum over CaCl2.
4a Yield 64%; mp 253 ◦C; Anal. found: C, 42.03; H, 3.11; N,
11.27; Calcd. for C23H25 N5O9Cl2Cu: C, 42.50; H, 3.88; N, 10.78;
IR (KBr, cm−1): (NH) 3292, (NH2) 3236, 3292, (C O) 1613,
(HC N) 1578, (ClO4) 1079, 621, (Cu–N) 528, (Cu–O) 488; m
(DMF, −1cm2mol−1): 144.36; UV–vis (DMF, max nm): 630; mass
spectrum: m/z= 650 [C23 H25N5O9Cl2Cu]+, 451 [C23 H25N5OCu]+,
256 [C10H14 N3OCu]+, 124 [C2H8N2Cu]+; magnetic moment: B,
1.92. 4b Yield 67%; mp > 300 ◦C; Anal. found: C, 51.03; H, 2.99;
N, 9.27; Calcd. for C33H25 N5O9Cl2Cu; C, 51.47; H, 3.27; N, 9.09;
IR (KBr, cm−1): (NH) 3298, (C O) 1626, (HC N) 1592, (ClO4)
1074, 625, (Cu–N) 533, (Cu–O) 482; m(DMF, −1cm2mol−1):
147.31; UV–vis (DMF, max nm): 638; mass spectrum: m/z= 770
[C33H25 N5O9Cl2Cu]+, 571 [C33H25 N5OCu]+, 376 [C20H14 N3OCu]+,
244 [C12H8N2Cu]+; magnetic moment: B, 1.89.
3. Results and discussion
The results of elemental analysis of the mixed ligand complexes
are in good agreement with those required by the proposed formula
(Fig. 3). The complexes presented by the formulae [Cu(L)(en)X2]
(1a–3a) and [Cu(L)(phen)X2](1b–3b) where X =Cl, N3−and NCS−
except 4a and 4b, but the complexes 4a and 4b turned out to
be [Cu(L)(en)](ClO4)2(4a), [Cu(L)(phen)](ClO4)2(4b) with the
perchlorate ion out of the coordination sphere. The generalized
equation for the reactions leading to the formation of the com-
plexes is shown in Fig. 2. All the complexes are insoluble in common
organic solvents except DMF and DMSO. The molar conductivity
values of the compounds 1a,2a,3a,1b,2b and 3b in 10−3M solu-
tion in DMF shows that they are non-electrolyte indicating that the
anions are coordinated to the central Cu(II) ion. But molar conduc-
tivity values of compounds 4a and 4b suggest that they are 1:2
electrolytes.
3.1. IR spectral studies
The structural elucidation of the complexes is also supports by
IR spectra and comparison of IR spectrum of the quinazoline lig-
Fig. 2. Scheme of preparation of complexes.
Fig. 3. Proposed molecular structure of mixed ligand complexes.
and Lwith those of isolated metal complexes indicate the mode of
bonding. The medium intensity band at 3283 cm−1observed in the
IR spectrum of free ligand Lis due to the (NH) of the quinazoline
ring. This band shifted to higher energies, by 11–15 cm−1in all of the
complexes indicates noninvolvement of the N–H in coordination.
The characteristic (C O) frequency of ligand Loccurs at 1660 cm−1
shifted to lower frequency by 34–53 cm−1in all complexes pro-
viding strong evidence for involvement of carbonyl oxygen in
complexation with metal ion [20]. The stretching vibration band
for (Cu–O) appears in the spectra of complexes at ∼476 cm−1. The
band at 1618 cm−1in the spectrum of free ligand L, attributed to the
azomethine (C N) group. In the spectra of the complexes this band
shifted to lower frequency as a result of coordination through the
azomethine nitrogen atom. This was also confirmed by the appear-
ance of new band at ∼530 cm−1in complexes due to (Cu–N).
The spectra of mixed en complexes (1a–4a) show two char-
acteristic bands at around 3235 and 3300 cm−1assigned to sym
and asym vibration of NH2suggesting coordination through NH2
[31]. In the spectra of mixed phen complexes (1b–4b), the bands
of phen free ligand at 740 cm−1are shifted to higher frequencies
around 777 cm−1. The azido complexes 2a and 2b show sharp band
at 2059 and 2057 cm−1and strong band at 1354 and 1343 cm−1,
respectively. These are assigned to aand svibrations of the
coordinated azido group. The isothiocyanato complexes 3a and
3b exhibit a strong and sharp band at 2073 and 2079 cm−1,a
weak band at 762 and 767 cm−1and another weak band at 488
and 485 cm−1, respectively, which can be attributed to (CN),
(CS) and (NCS), respectively [32]. These values are typical for
N-bonded isothiocynate complexes. The perchlorate complexes
4a and 4b exhibit broad band at 1079 and 1074 cm−1(3) and
strong band at 621 and 625 cm−1(4), respectively, is devoid of
any splitting and are consistent with the IR-active normal modes
for D4hsymmetry suggesting that these ClO4−anions are not
coordinated to the copper atom [33].
3.2. Electronic spectra and magnetic moments
The electronic transitions of all the complexes were recorded in
DMF (10−4) at 200–1100 nm. The electronic spectra of complexes
1a–3a and 1b–3b show broad band centered at ∼670 nm assigned
for 2Eg →2T2g transitions in strong octahedral environment. It can
be seen that the d–d absorption of isothiocynato complexes (660
V.A. Sawant et al. / Spectrochimica Acta Part A 74 (2009) 1100–1106 1103
and 662 nm) are blue shifted by 10–20 nm compare to azido com-
plexes (668 and 680 nm) may be suggestive of stronger distortion
compared to azido complexes. The room temperature magnetic
moment of the complexes in the polycrystalline state fall in the
1.79–1.89 Brange, which is very close to the spin only value of
1.73 Bfor d9typical value of s= (1/2)Cu(II). On the other hand,
the electronic spectra of 4a and 4b showed a broad band at 630
and 638 nm, respectively can be attributed to 2A1g →2B1g tran-
sition reveal the square-planer geometry around Cu(II) ion. The
square-planer geometry of 4a and 4b is confirmed by the measured
magnetic moment values of 1.92 and 1.89 B, respectively which
is in harmony with the reported value for the square-planer Cu(II)
complex [34].
3.3. ESR spectra
To obtain further information about the stereochemistry and
the site of the metal ligand bonding and to determine the magnetic
interaction in the metal complexes, the X-band ESR spectra of all
Cu(II) complexes have been recorded in the polycrystalline state at
room temperature and in DMF solution at 77 K using 9.5 GHz field
modulation and the g factors were quoted relative to the standard
marker TCNE (g= 2.00277). ESR spectral assignments of the Cu(II)
complexes along with the spin Hamiltonian and orbital reduction
parameters are summarized in Table 1.
The ESR spectra of the complexes 4a and 4b in polycrys-
talline state shows only one broad signal at g= 2.076 and 2.073,
respectively, due to dipolar broadening and enhanced spin lattice
relaxation. The spectra of the complexes 1a–3a and 1b–3b show
typical axial behaviour with slightly different g|| and g⊥values.
The geometric parameter G, which is measure of exchange inter-
action between the copper centers in polycrystalline compound,
is calculated using the equation G=(g|| −2.0023)/(g⊥−2.0023). If
G> 4, the exchange interaction between Cu(II) centers is negligible
and if G< 4, a considerable exchange interaction is indicated in the
solid complex [35]. In all the Cu(II) complexes g|| >g⊥> 2.0023 and
Gvalues within the range 2.95 and 4.05 are consistent with dx2−y2
ground state [36].
The ESR spectra of all the Cu(II) complexes in DMF solution
at 77 K (Fig. 4) showed well resolved hyperfine spectra giving
g|| >g⊥> 2.0023, corresponding to the presence of an unpaired elec-
tron in the dx2−y2orbital. For a Cu(II) complex, g|| is a parameter
sensitive enough to indicate covalence. The g|| values for all the
Cu(II) complexes are less than 2.3 is an indication of significant
covalent bonding in these complexes.
The ESR parameters g||,g⊥,gav ,A|| and A⊥and the energies of
the d–d transitions were used to evaluate the bonding parameters
˛2,ˇ2and 2, which may be regarded as measures of covalency
of the in-plane -bonding, in-plane -bonding and out of plane -
bonding, respectively. The value of ˛2and ˇ2was estimated from
the following expression [37,38] where ˛2= 1.0 indicates complete
ionic character, whereas ˛2= 0.5 denotes 100% covalent bonding,
Fig. 4. ESR spectrum of 2a in DMF solution at 77 K.
with the assumption of negligibly small values of the overlap inte-
gral.
˛2=−(A|| /0.036) +(g|| −2.0023) +(3/7)(g⊥−2.0023) +0.04
ˇ2=(g|| −2.0023)E/ −8˛2
The following simplified expressions were used to calculate the
bonding parameters [39,40]:
K2
|| =(g|| −2.00277)Ed–d/−8
K2
⊥=(g⊥−2.00277)Ed–d/−2
where K2
|| =˛2ˇ2and K2
⊥=˛22,K|| and K⊥are orbital reduction
factors and 0represents the spin–orbit coupling constant which
equals −828 cm−1. According to Hathaway [41],K|| ≈K⊥≈0.77 for
pure in-plane -bonding and K|| <K⊥for in-plane -bonding, while
for out of plane -bonding K|| >K⊥. In all the Cu(II) complexes, it
is observed that K|| <K⊥which indicates the presence of signifi-
cant in-plane -bonding. The values of bonding parameters ˛2,ˇ2
and 2< 1.0 indicate significant in-plane -bonding and in plane
-bonding.
The Fermi contact hyperfine interaction term Kmay be obtained
from [42]
K=Aav
Pˇ2+gav−2.00277
ˇ2
where Pis the free ion dipolar term and its value is 0.036. Kis
dimensionless quantity, which is a measure of the contribution of
s electrons to the hyperfine interaction and is generally found to
have a value of 0.30. The Kvalues obtained for all the complexes
are in agreement with those estimated by Assour [43] and Abragam
and Pryce [44].
3.4. Thermal studies
The thermal decomposition studies of all Cu(II) complexes
except 4a and 4b, were carried out up to 1200 ◦CinN
2atmo-
Table 1
ESR spectral assignments for Cu(II) complexes in polycrystalline state at (298 K) and solution at (77K).
Complex Polycrystalline state (298 K) DMF solution (77 K)
g|| g⊥gav g|| g⊥gav A||aA⊥aAav aG˛2ˇ22K|| K⊥K
1a 2.224 2.096 2.138 2.220 2.076 2.124 174.8 32.7 80.1 2.95 0.672 0.728 0.987 0.49 0.66 0.47
2a 2.208 2.066 2.113 2.255 2.067 2.129 168.3 25.24 72.92 3.90 0.726 0.821 0.841 0.57 0.59 0.41
3a 2.186 2.066 2.106 2.271 2.073 2.139 168.3 28.09 74.8 3.77 0.737 0.833 0.882 0.61 0.65 0.46
4a 2.076 2.223 2.059 2.113 182.3 32.72 82.58 3.90 0.668 0.794 0.813 0.53 0.54 0.42
1b 2.239 2.060 2.119 2.241 2.065 2.124 177.6 18.7 71.69 3.80 0.693 0.783 0.825 0.54 0.57 0.40
2b 2.149 2.034 2.0723 2.216 2.060 2.112 187.0 15.57 72.71 3.70 0.652 0.749 0.809 0.48 0.52 0.41
3b 2.167 2.053 2.091 2.208 2.060 2.109 177.65 23.3 74.5 3.56 0.674 0.695 0.78 0.46 0.52 0.45
4b 2.073 2.208 2.053 2.104 172.9 37.4 82.56 4.05 0.684 0.711 0.701 0.48 0.47 0.46
aExpressed in units of cm−1multiplied by a factor of 10−4.
1104 V.A. Sawant et al. / Spectrochimica Acta Part A 74 (2009) 1100–1106
Fig. 5. TG, DTG and DTA curves of 1a.
sphere. The perchlorate complexes 4a and 4b were not studied
for safety reasons. Typical TG, DTG and DTA curves of 1a is pre-
sented in Fig. 5 and the thermal analysis data is presented in
Table 2.
The thermal decomposition process of chloride complexes 1a
and 1b involves three decomposition steps. The complexes show
no mass loss up to 180 and 280 ◦C, respectively, revealing the
absence of either water or solvent molecules in these complexes.
The first decomposition step takes place in the temperature range
180–264 and 280–490 ◦C with endothermic DTA peaks at 220 ◦C
(1a) and 324, 429 and 452 ◦C(1b), respectively, corresponding
to the mass loss of 37.82 and 38.23% may be attributed to the
decomposition of half of the molecule L(Calcd.% = 37.40 and 39.00).
The second step occurs in the 264–596 and 490–660 ◦C range
accompanied by a mass loss of 26.10 and 12.25% respectively, cor-
responding to the decomposition of remaining half of the molecule
of L(Calcd.% = 25.31 and 11.99). The DTA curve gives peaks at 305
(exo), 440 and 522 ◦C (endo) for 1a and weak endothermic multi-
plet in the 520–660 ◦C range for complex 1b. The third step takes
place in the 596–1118 ◦C range for 1a corresponding to the mass
loss of 11.64% may be attributed to the decomposition of ethylene-
diamine (Calcd.% = 11.51), leaving CuCl2as residue. On the other
hand, for complex 1b the third step of decomposition which starts
at 660 ◦C is a continuous one. The steady mass loss observed in this
step may be due to the expulsion of 1,10-phenanthroline molecule
with the volatilization of the residue of anhydrous CuCl2.
The azide complexes 2a and 2b undergo decomposition in three
stages. There is no mass loss up to 173 and 268 ◦C, respectively
revealing the absence of either water or solvent molecules in these
complexes. The first stage corresponding to the mass loss of 51.89
and 46.74% may be attributed to the decomposition of half of the
molecule of Land two azide ions (Calcd.% = 52.19 and 46.91) in
the range 173–248 and 268–460 ◦C with endothermic DTA peak
at 208◦C for 2a and 310 ◦C for 2b. The second stage occurs in the
248–610 and 460–680 ◦C range and is accompanied by a mass loss
of 24.53 and 15.67% respectively, may be attributed to the decom-
position of the remaining half of the molecule of L(Calcd.% = 24.69
and 15.89) with endothermic DTA peaks at 440 and 537 ◦C(2a)
Table 2
Thermal behaviour of Cu(II) complexes.
Compound Thermogravimetry (TG) DTG peak (◦C) DTA peak (◦C) Mass loss (%) Decomposition product loss
Stage Temp. range (◦C) Found Calculated
1a I 180–264 240 220 37.82 37.40 C13 H11N2
II 264–596 492 305, 440, 522 26.10 25.31 C8H7NO
III 596–1118 1001 870 11.64 11.51 C2H8N2
2a I 173–248 228 208 51.89 52.19 C13 H11N2,2N
3
II 248–610 486 440, 537 24.53 24.69 C8H6NO
III 610–1080 1030 985 11.35 11.23 C2H8N2
3a I 165–250 232 212 54.04 54.90 C13H11 N2, 2NCS
II 250–588 483 380, 512 22.67 23.29 C8H6NO
III 588–1073 1046 924 10.46 10.59 C2H8N2
1b I 280–490 452 324, 429, 452 38.23 39.00 C15 H12N3O
II 490–660 577 520–660 (multiplet) 12.25 11.99 C6H5
III 660–1198 1101 1081 27.74 28.07 C12 H8N2
2b I 268–460 380 310 46.74 46.91 C14H13 N3,2N
3
II 460–680 620 650 15.67 15.89 C7H4O2
III 680–1175 1130 1020 25.97 27.51 C12 H8N2
3b I 253–455 389 298, 432 44.93 45.30 C13H11N2, 2NCS
II 455–668 589 455–660 (multiplet) 18.76 19.22 C8H6NO
III 668–1157 1113 1064 26.14 26.23 C12 H8N2
V.A. Sawant et al. / Spectrochimica Acta Part A 74 (2009) 1100–1106 1105
and 650 ◦C(2b). In the third stage (610–1080 and 680–1175 ◦C),
a mass loss of 11.35 and 25.97% corresponding to the decom-
position of ethylenediamine and 1,10-phenanthroline molecule,
respectively was obtained leaving anhydrous CuO (Calcd.% = 11.23
and 27.51).
The isothiocynate complexes 3a and 3b, there is no mass loss up
to 165 and 253 ◦C, respectively revealing the absence of either water
or solvent molecules in these complexes. The first stage takes place
in the 165–250 and 253–455 ◦C ranges corresponding to the mass
loss of 54.04 and 44.93% may be attributed to the decomposition of
half of the molecule Land two isothiocynate ions (Calcd.% = 54.90
and 45.30). The DTA curve gives a broad endothermic peak at 212 ◦C
for complex 3a and weak endothermic peaks at 298 and 432 ◦C
for complex 3b. The second stage takes place in the 250–588 and
455–668 ◦C range corresponding to the mass loss of 22.67 and
18.76% respectively, may be attributed to the decomposition of
the remaining half of the molecule of L(Calcd.% = 23.29 and 19.22).
The DTA curve gives two endothermic peaks at 380 and 512 ◦C for
complex 3a and weak endothermic multiplets in the 455–668 ◦C
for complex 3b. The third stage takes place in the 588–1073 and
668–1157 ◦C range, corresponding to the mass loss of 10.46 and
26.14% may be attributed to the decomposition of ethylenediamine
and 1,10-phenanthroline molecule, respectively leaving anhydrous
CuO (Calcd.% =10.59 and 26.23).
3.5. Electrochemical studies
The electrochemical properties of the ligand Land its Cu(II) com-
plexes have been examined cyclic voltammetrically in 10−3MDMF
solution containing 0.05 M n-Bu4NClO4as supporting electrolyte
and redox potentials are expressed with reference to Ag/AgCl. All
the measurements were carried out in the potential range +1.5 to
−1.5 V with scan rate 50mV s−1and are listed in Table 3.
The free ligand Ldisplayed waves at Epa values −0.40 V and Epc
value −1.17 V corresponding to irreversible reduction of the L. The
electrochemical potentials of the Cu(II) complexes were charac-
terized by well-defined waves in anodic region. Since the ligands
used in this work are not reversibly oxidized or reduced in the
applied potential range, the redox processes are assigned to the
metal centers only.
For all the Cu(II) complexes the reduction wave (Epc,−0.618 to
−1.1373 V) corresponding to reduction of Cu(II) to Cu(I) is obtained.
During the reverse scan the oxidation of Cu(I) to Cu(II) occurs in the
potential range (Epa,−0.50 to −0.847 V). The values of the limiting
peak-to-peak separation (Ep) ranging from 103 to 644 mV reveals
that this process can be quassireversible. The en complexes (1a–4a)
showed E1/2 lies at −1.015 to −1.051 V (Cu(II)/Cu(I)) while phen
complexes (1b–4b) showed well-defined waves E1/2 lies at −0.565
to −0.760 V (Cu(II)/Cu(I)). The redox processes for Cu(II) complexes
Table 3
Electrochemical data for Land its Cu(II) complexes.
Compound Reduction potentials (V)
Epa (V) Epc (V) Ep(V) E1/2 (V)
L−0.400 −1.170 – –
1a −0.693 −1.170 0.477 −0.931
2a −0.710 −1.320 0.610 −1.015
3a −0.847 −1.248 0.401 −1.048
4a −0.729 −1.373 0.644 −1.051
1b −0.700 −0.625 0.075 −0.662
2b −0.500 −0.630 0.130 −0.565
3b −0.721 −0.618 0.103 −0.669
4b −0.580 −0.940 0.360 −0.760
Supporting electrolyte: n-Bu4NClO4(0.05 M); complex: 0.001 M; solvent: DMF;
Ep=Epa −Epc, where Epa and Epc are anodic and cathodic potentials, respectively;
E1/2 = (1/2)(Epa +Epc); scan rate: 50 mV s−1.
of phen (1b–4b) appear at more positive potential (−0.565 to
−0.760 V) as compared to those for corresponding en complexes
(1a–4a)(−1.015 to −1.051 V). This trend may be due to the strong
-donor tendency of the ethylenediamine moiety and the strong
-acceptor ability of 1,10-phenanthroline ligand. These results are
consistent with those reported in the literature [45].
4. Conclusions
Some mixed ligand Cu(II) complexes (1a–4a and 1b–4b)of2-
phenyl-3-(benzylamino)-1,2-dihydroquinazoline-4-(3H)-one and
1,10-phenanthroline (phen) or ethylenediamine (en) have been
synthesized and characterized. On the basis of electronic spectral
data and magnetic susceptibility measurement octahedral geom-
etry has been proposed for 1a–3a and 1b–3b and square-planer
geometry for 4a and 4b. The ESR spectral data of the complexes
showed that the metal–ligand bonds have considerable covalent
character. The phen complexes (1b–4b) are found to be thermally
more stable than the en complexes (1a–4a). Further the electro-
chemical behaviour of mixed ligand Cu(II) complexes showed that
the complexes of phen (1b–4b) appear at more positive potential
as compared to those for corresponding en complexes (1a–4a).
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