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

Article abstract of DOI:10.1016/j.saa.2009.09.015

Some mixed ligand Cu(II) complexes of the type [Cu(L)(en)X₂] (1a-3a), [Cu(L)(en)](ClO₂)₂ (4a), [Cu(L)(phen)X ₂] (1b-3b) and [Cu(L)(phen)](ClO₄)₂ (4b) [where L = 2-phenyl-3-(benzylamino)-1,2

Full text of DOI:10.1016/j.saa.2009.09.015

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
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 March 2009
Received in revised form 7 August 2009
Accepted 12 September 2009
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−, N3 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.
Keywords:
Mixed ligands
Quinazoline derivatives
Ethylenediamine
1,10-Phenanthroline
Thermal analysis
Cyclic voltammetry
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
potent phosphodiesterase inhibitory activity, which is potentially
useful in the treatment of asthma [18]. They can form different
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
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.
∗
Corresponding author. Tel.: +91 231 2609164; fax: +91 231 2691533.
E-mail address: sanjaycha2@rediffmail.com (S.S. Chavan).
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
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 C23H25N5OCl2Cu: 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, ꢂ−1 cm2 mol−1): 12.76; UV–vis (DMF, ꢃmax nm): 670; mass
spectrum: m/z = 522 [C23H25N5OCl2Cu]+, 368 [C11H15N5OCl2Cu]+,
297 [C11H15N5OCu]+, 124 [C2H8N2Cu]+; magnetic moment: ꢄB,
1.89. 1b Yield 67%; mp > 300 ◦C; Anal. found: C, 61.34; H, 3.49; N,
11.21; Calcd. for C33H25N5OCl2Cu: 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, ꢂ−1 cm2 mol−1): 27.49; UV–vis (DMF,
ꢃmax nm): 666; mass spectrum: m/z = 642 [C33H25N5OCl2Cu]+, 488
[C21H15N5OCl2Cu]+, 376 [C20H14N3OCu]+, 244 [C12H8N2Cu]+; mag-
netic moment: ꢄB, 1.81.
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.
10−3 M 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−1 spectral 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.
2.3.2. 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 C23H25N11OCu; C, 51.63; H, 4.71; N, 28.80;
IR (KBr, cm−1): ꢁ(NH) 3292, ꢁ(NH2) 3236, 3292, ꢁ(C O) 1613,
ꢁ(HC N) 1578, ꢅ(N3) 2059, 1354, ꢁ(Cu–N) 531, ꢁ(Cu–O) 472;
ꢀm (DMF, ꢂ−1 cm2 mol−1): 33.33; UV–vis (DMF, ꢃmax nm): 668;
mass spectrum: m/z = 536 [C23H25N11OCu]+, 451 [C23H25N5OCu]+,
256 [C10H14N3OCu]+, 124 [C2H8N2Cu]+; magnetic moment: ꢄB,
1.83. 2b Yield 67%; mp > 300 ◦C; Anal. found: C, 60.13; H, 3.47;
N, 23.87; Calcd. for C33H25N11OCu; C, 60.50; H, 3.85; N, 23.52;
IR (KBr, cm−1): ꢁ(NH) 3292, ꢁ(C O) 1607, ꢁ(HC N) 1587, ꢅ(N3)
2057, 1343, ꢁ(Cu–N) 535, ꢁ(Cu–O) 476; ꢀm (DMF, ꢂ−1 cm2 mol−1):
16.69; UV–vis (DMF, ꢃmax nm): 680; mass spectrum: m/z = 655
[C33H25N11OCu]+, 571 [C33H25N5OCu]+, 376 [C20H14N3OCu]+, 244
[C12H8N2Cu]+; magnetic moment: ꢄB, 1.79.
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, 0.151 g) 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.
L Yield 86%; mp 166 ◦C; Anal. found. C, 76.68; H, 4.87; N,
13.17 Calcd. for C21H17N3O; 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): ı 9.22 (s, HC N), ı 6.69–7.97 (m, Ar–H), ı 6.29 (d,
C–H), ı 4.89 (s, NH); mass spectrum: m/z = 327 (C21H17N3O)+, 223
(C14H11N2O)+, 119 (C7H5NO)+, 104 (C7H4O)+, 77 (C6H5)+.
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.
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.
3a Yield 66%; mp 238 ◦C; Anal. found: C, 52.47; H, 4.21; N, 17.61;
Calcd. for C25H25N7OS2Cu: C, 52.94; H, 4.44; N, 17.25; IR (KBr,
cm−1): ꢁ(NH) 3294, ꢁ(NH2) 3243, 3294, ꢁ(C O) 1609, ꢁ(HC N)
1573, ꢅ(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, ꢂ−1 cm2 mol−1): 26.51; UV–vis (DMF, ꢃmax nm): 660; mass
spectrum: m/z = 567 [C25H25N7OS2Cu]+, 451 [C23H25N5OCu]+, 256
[C10H14N3OCu]+, 124 [C2H8N2Cu]+; magnetic moment: ꢄB, 1.89.
3b Yield 68%; mp > 300 ◦C; Anal. found: C, 60.87; H, 3.36; N, 14.58;
Calcd. for C35H25N7OS2Cu; C, 61.16; H, 3.67; N, 14.27; IR (KBr,
cm−1): ꢁ(NH) 3285, ꢁ(C O) 1616, ꢁ(HC N) 1578, ꢅ(NCS) 2079,
767, 485, ꢁ(Cu–N) 530, ꢁ(Cu–O) 474; ꢀm (DMF, ꢂ−1 cm2 mol−1):
38.40; UV–vis (DMF, ꢃmax nm): 662; mass spectrum: m/z = 687
[C35H25N7OS2Cu]+, 571 [C33H25N5OCu]+, 376 [C20H14N3OCu]+, 244
[C12H8N2Cu]+; magnetic moment: ꢄB, 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 C23H25N5O9Cl2Cu: 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, ꢂ−1 cm2 mol−1): 144.36; UV–vis (DMF, ꢃmax nm): 630; mass
spectrum: m/z = 650 [C23H25N5O9Cl2Cu]+, 451 [C23H25N5OCu]+,
256 [C10H14N3OCu]+, 124 [C2H8N2Cu]+; magnetic moment: ꢄB,
1.92. 4b Yield 67%; mp > 300 ◦C; Anal. found: C, 51.03; H, 2.99;
N, 9.27; Calcd. for C33H25N5O9Cl2Cu; 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, ꢂ−1 cm2 mol−1):
147.31; UV–vis (DMF, ꢃmax nm): 638; mass spectrum: m/z = 770
[C33H25N5O9Cl2Cu]+, 571 [C33H25N5OCu]+, 376 [C20H14N3OCu]+,
244 [C12H8N2Cu]+; magnetic moment: ꢄB, 1.89.
Fig. 3. Proposed molecular structure of mixed ligand complexes.
and L with those of isolated metal complexes indicate the mode of
bonding. The medium intensity band at 3283 cm−1 observed in the
IR spectrum of free ligand L is due to the ꢁ(NH) of the quinazoline
ring. This band shifted to higher energies, by 11–15 cm−1 in all of the
complexes indicates noninvolvement of the N–H in coordination.
The characteristic ꢁ(C O) frequency of ligand L occurs at 1660 cm−1
shifted to lower frequency by 34–53 cm−1 in 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−1 in 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−1 in complexes due to ꢁ(Cu–N).
The spectra of mixed en complexes (1a–4a) show two char-
acteristic bands at around 3235 and 3300 cm−1 assigned to ꢁsym
and ꢁasym vibration of NH2 suggesting coordination through NH2
[31]. In the spectra of mixed phen complexes (1b–4b), the bands
of phen free ligand at 740 cm−1 are shifted to higher frequencies
around 777 cm−1. The azido complexes 2a and 2b show sharp band
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 [C−u(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 10−3 M 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.
at 2059 and 2057 cm−1 and strong band at 1354 and 1343 cm−1
,
respectively. These are assigned to ꢅa and ꢅs vibrations 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−1 and another weak band at 488
and 485 cm−1, respectively, which can be attributed to ꢅ(CN),
ꢅ(CS) and ꢅ(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-acti−ve normal modes
for D4h symmetry suggesting that these ClO4 anions are not
coordinated to the copper atom [33].
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-
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 → T2g transitions in strong octahedral environment. It can
2
Fig. 2. Scheme of preparation of complexes.
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 ꢄB range, which is very close to the spin only value of
1.73 ꢄB for d9 typical value of s = (1/2)Cu(II). On the other hand,
the electronic spectra of 4a and 4b showed a broad band at 630
2
2
and 638 nm, respectively can be attributed to A1g → B1g 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 ꢄB, respectively which
is in harmony with the reported value for the square-planer Cu(II)
complex [34].
3.3. ESR spectra
Fig. 4. ESR spectrum of 2a in DMF solution at 77 K.
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.
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/ − 8ꢃ˛2
The following simplified expressions were used to calculate the
bonding parameters [39,40]:
K|2| = (g|| − 2.00277)Ed–d/ − 8ꢃ
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.
K⊥2 = (g⊥ − 2.00277)Ed–d/ − 2ꢃ
where K|2| = ˛2ˇ2 and K⊥2 = ˛2ꢆ2, K and K are orbital reduction
||
⊥
factors and ꢃ0 represents the spin–orbit coupling constant which
equals −828 cm−1. According to Hathaway [41], K ≈ K⊥ ≈ 0.77 for
||
⊥
||
The geometric parameter G, which is measure of exchange inter-
pure in-plane ␴-bonding and K < K for in-plane ␲-bonding, while
||
⊥
action between the copper centers in polycrystalline compound,
for out of plane ␲-bonding K > K . In all the Cu(II) complexes, it
|| ⊥
is calculated using the equation G = (g − 2.0023)/(g⊥ − 2.0023). If
is observed that K < K which indicates the presence of signifi-
|| ⊥
||
G > 4, the exchange interaction between Cu(II) centers is negligible
and if G < 4, a considerable exchange interaction is indicated in the
cant in-plane ␲-bonding. The values of bonding parameters ˛2, ˇ2
and ꢆ2 < 1.0 indicate significant in-plane ␴-bonding and in plane
␲-bonding.
solid complex [35]. In all the Cu(II) complexes g > g > 2.0023 and
||
⊥
G values within the range 2.95 and 4.05 are consistent with dx
ground state [36].
The Fermi contact hyperfine interaction term K may be obtained
from [42]
2
2
−y
The ESR spectra of all the Cu(II) complexes in DMF solution
at 77 K (Fig. 4) showed well resolved hyperfine spectra giving
Aav
Pˇ2
gav − 2.00277
K =
+
ˇ2
g > g > 2.0023, corresponding to the presence of an unpaired elec-
||
⊥
tron in the dx
orbital. For a Cu(II) complex, g is a parameter
2
where P is the free ion dipolar term and its value is 0.036. K is
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 K values obtained for all the complexes
are in agreement with those estimated by Assour [43] and Abragam
and Pryce [44].
2
||
−y
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, ˇ2 and ꢆ2, 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 ˛2 and ˇ2 was estimated from
the following expression [37,38] where ˛2 = 1.0 indicates complete
ionic character, whereas ˛2 = 0.5 denotes 100% covalent bonding,
3.4. Thermal studies
The thermal decomposition studies of all Cu(II) complexes
except 4a and 4b, were carried out up to 1200 ◦C in N2 atmo-
Table 1
ESR spectral assignments for Cu(II) complexes in polycrystalline state at (298 K) and solution at (77 K).
Complex
Polycrystallinestate(298 K)
DMF solution (77 K)
a
a
a
2
g
||
g
⊥
gav
g
||
g
⊥
gav
A
||
A
⊥
Aav
G
˛
ˇ2
ꢆ2
K
||
K
⊥
K
1a
2a
3a
4a
1b
2b
3b
4b
2.224
2.208
2.186
2.096
2.066
2.066
2.138
2.113
2.106
2.076
2.119
2.0723
2.091
2.073
2.220
2.255
2.271
2.223
2.241
2.216
2.208
2.208
2.076
2.067
2.073
2.059
2.065
2.060
2.060
2.053
2.124
2.129
2.139
2.113
2.124
2.112
2.109
2.104
174.8
168.3
168.3
182.3
177.6
187.0
177.65
172.9
32.7
80.1
72.92
74.8
82.58
71.69
72.71
74.5
2.95
3.90
3.77
3.90
3.80
3.70
3.56
4.05
0.672
0.726
0.737
0.668
0.693
0.652
0.674
0.684
0.728
0.821
0.833
0.794
0.783
0.749
0.695
0.711
0.987
0.841
0.882
0.813
0.825
0.809
0.78
0.49
0.57
0.61
0.53
0.54
0.48
0.46
0.48
0.66
0.59
0.65
0.54
0.57
0.52
0.52
0.47
0.47
0.41
0.46
0.42
0.40
0.41
0.45
0.46
25.24
28.09
32.72
18.7
15.57
23.3
2.239
2.149
2.167
2.060
2.034
2.053
37.4
82.56
0.701
a
Expressed in units of cm−1 multiplied 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.
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 CuCl2 as 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 L and 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)
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
Table 2
Thermal behaviour of Cu(II) complexes.
Compound
Thermogravimetry (TG)
DTG peak (◦C)
DTA peak (◦C)
Mass loss (%)
Found
Decomposition product loss
Stage
Temp. range (◦C)
Calculated
1a
I
II
III
180–264
264–596
596–1118
240
492
1001
220
305, 440, 522
870
37.82
26.10
11.64
37.40
25.31
11.51
C13H11N2
C8H7NO
C2H8N2
2a
3a
1b
2b
3b
I
II
III
173–248
248–610
610–1080
228
486
1030
208
440, 537
985
51.89
24.53
11.35
52.19
24.69
11.23
C13H11N2, 2N3
C8H6NO
C2H8N2
I
II
III
165–250
250–588
588–1073
232
483
1046
212
380, 512
924
54.04
22.67
10.46
54.90
23.29
10.59
C13H11N2, 2NCS
C8H6NO
C2H8N2
I
II
III
280–490
490–660
660–1198
452
577
1101
324, 429, 452
520–660 (multiplet)
1081
38.23
12.25
27.74
39.00
11.99
28.07
C
15H12N3O
C6H5
C
12H8N2
I
II
III
268–460
460–680
680–1175
380
620
1130
310
650
1020
46.74
15.67
25.97
46.91
15.89
27.51
C14H13N3, 2N3
C7H4O2
C12H8N2
I
II
III
253–455
455–668
668–1157
389
589
1113
298, 432
455–660 (multiplet)
1064
44.93
18.76
26.14
45.30
19.22
26.23
C13H11N2, 2NCS
C8H6NO
C12H8N2

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).
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].
The isothiocynate complexes 3a and 3b, there is no mass loss up
to165and 253 ◦C, respectively revealing theabsenceofeither 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 L and 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).
4. Conclusions
Some mixed ligand Cu(II) complexes (1a–4a and 1b–4b) of 2-
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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The electrochemical properties of the ligand L and its Cu(II) com-
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Electrochemical data for L and its Cu(II) complexes.
Compound
Reduction potentials (V)
Epa (V)
Epc (V)
ꢇEp (V)
E1/2 (V)
L
−0.400
−0.693
−0.710
−0.847
−0.729
−0.700
−0.500
−0.721
−0.580
−1.170
−1.170
−1.320
−1.248
−1.373
−0.625
−0.630
−0.618
−0.940
–
–
1a
2a
3a
4a
1b
2b
3b
4b
0.477
0.610
0.401
0.644
0.075
0.130
0.103
0.360
−0.931
−1.015
−1.048
−1.051
−0.662
−0.565
−0.669
−0.760
Supporting electrolyte: n-Bu4NClO4 (0.05 M); complex: 0.001 M; solvent: DMF;
ꢇEp = Epa − Epc, where Epa and Epc are anodic and cathodic potentials, respectively;
E1/2 = (1/2)(Epa + Epc); scan rate: 50 mV s−1
.

1106
V.A. Sawant et al. / Spectrochimica Acta Part A 74 (2009) 1100–1106
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