Synthesis, characterization, thermal, and electrochemical properties of Co(II) and Cu(II) pseudohalide complexes with 2-mercapto-3-phenyl-quinazolin- 4(3H)-one and ethylendiamine or 1,10-phenanthroline as ligands

Article abstract of DOI:10.1080/15533174.2010.509296

Several complexes of the type [M(L)(en or phen)(H₂O)X] (1a-4a and 1b-4b); where M = Co(II) and Cu(II); L = 2-mercapto-3-phenyl-quinazolin- 4(3H)-one; en = ethylenediamine, phen = 1,10-phenanthroline; X = N-3 and NCS- have been prepared and characterized. The complex formation occurred through both nitrogen and sulphur atom of the ligand L. Electronic spectra and magnetic moment values suggest octahedral geometry for all complexes. The thermal behavior of the complexes revealed that the phen complexes are thermally more stable than the en complexes. The electrochemical behavior of the Cu(II) complexes showed that phen complexes appeared at more positive potential than corresponding en complexes. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2010.509296

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:592–600, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.509296
Synthesis, Characterization, Thermal, and Electrochemical
Properties of Co(II) and Cu(II) Pseudohalide Complexes
with 2-mercapto-3-phenyl-quinazolin-4(3H)-one and
ethylendiamine or 1,10-phenanthroline as Ligands
Vaishali A. Sawant, Sanjay S. Chavan, and Vasant B. Helavi
Department of Chemistry, Shivaji University, Kolhapur, India
to react readily with transition metal ions to form stable com-
plexes withunusual structural andchemical properties. Owingto
their versatile bioactivities and the potential applications in var-
ious fields, the coordinating behavior of quinazolinone ligands
with transition metal ions has been studied extensively.[14−17]
Ethylenediamine and 1,10-phenanthroline chelators are also
good nitrogen donors, and the complexes formed serve as build-
ing blocks for the synthesis of metallodendrimers, as a molecu-
lar scaffolding for supramolecular assemblies, and in analytical
chemistry, catalysis, electrochemistry, ring-opening metathe-
sis polymerization.[18−21] They also act as potential antitumor
agents and show better antitumor activity if they form water
soluble neutral complexes with transition metal ions.[22] Pseu-
dohalides, especially azide (N−3 ) and thiocynate (NCS−), are
known for construction of monomeric, dimeric, or polymeric
complexes because of their versatile coordination modes and
ability to mediate strong magnetic coupling.
Several complexes of the type [M(L)(en or phen)(H2O)X]
(1a-4a and 1b-4b); where M = Co(II) and Cu(II); L = 2-mercapto-
3-phenyl-quinazolin-4(3H)-one; en = ethylenediamine, phen =
1,10-phenanthroline; X = N−3 and NCS− have been prepared and
characterized. The complex formation occurred through both ni-
trogen and sulphur atom of the ligand L. Electronic spectra and
magnetic moment values suggest octahedral geometry for all com-
plexes. The thermal behavior of the complexes revealed that the
phen complexes are thermally more stable than the en complexes.
The electrochemical behavior of the Cu(II) complexes showed that
phen complexes appeared at more positive potential than corre-
sponding en complexes.
Keywords mixed ligands, quinazolinone derivatives, thermal studies,
cyclic voltammetry
INTRODUCTION
In continuation of our earlier work on structural characteri-
zation of transition metal complexes containing quinazolinone
ligands,[23] here we report the synthesis, properties and molec-
ular structure of Co(II) and Cu(II) complexes of 2-mercapto-3-
phenyl-quinazolin-4(3H)-one (L) with ethylenediamine (en) or
1,10-phenanthroline (phen) and N−3 or NCS− as coligands. The
complexes were characterized on the basis of elemental analysis,
molar conductance, magnetic moment, spectroscopic (IR, UV-
visible and ESR), and thermal studies. The redox behavior of
Cu(II) complexes has also been studied by cyclic voltammetry.
The coordination chemistry of transition metal complexes
with hybrid ligands are of current interest because they can
provide new materials with useful properties such as magnetic
exchange,[1,2] electrical conductivity,[3] photoluminescence,[4]
nonlinear optical property,[5] and antimicrobial activity.[6]
Among various ligands quinazolinone containing nitrogen, sul-
phur donor atoms have received much attention in recent years.
These compounds exhibit varieties of biological properties, es-
pecially anti-inflammatory,[7] anticonvulsant,[8] antihyperten-
sive,[9] anticancer,[10,11] antimalarial,[12] antibacterial,[13] etc.
The presence of endocyclic hard N-donor and exocyclic soft
S-donor atoms in the backbone of these ligands enable them
EXPERIMENTAL
Reagents
All the chemicals used were pure and of analytical
Received 29 January 2010; accepted 8 July 2010.
One of the authors (VAS) is thankful to Council of Scientific and grade. 2-mercapto-3-phenyl-quinazolin-4(3H)-one was syn-
thesized by reported method.[24] Cu(NO3)2·3H2O (E-Merk
Industrial Research (CSIR), New Delhi for awarding Senior Research
Fellowship. Authors are also thankful to Regional Sophisticated Instru-
India), Co(NO3)2·6H2O (E-Merk India), NaN3 (Aldrich,
mentation Centre (RSIC), IIT Mumbai for providing ESR facilities.
USA), NH4NCS (Aldrich, USA), ethylenediamine, 1,10-
Address correspondence to Sanjay S. Chavan, Department of
phenanthroline (Alfa Aesar) were purchased from the respective
concerns and were used as received.
Chemistry, Shivaji University, Kolhapur (MS) India–416 004. E-mail:
sanjaycha2@rediffmail.com
592

PROPERTIES OF PSEUDOHALIDE COMPLEXES
593
tion at 77K on Varian E-112 spectrometer using TCNE as the
standard marker. Thermal analysis of the complexes was carried
out on a Perkin Elmer thermal analyzer in nitrogen atmosphere at
a heating rate of 10◦C/min. Cyclic voltammetry measurements
were performed with Electrochemical Quartz Crystal Microbal-
ance CHI-400. A standard three electrode system, consisting
of Pt disk working electrode, Pt wire counter electrode, and
Ag/AgCl reference electrode containing aqueous 3M KCl were
used. All potentials were converted to SCE scale.
O
O
N
N
N
S
N
S
N
X
M
X
M
NH
2
H O
H O
2
2
N
H N
2
Synthesis of Complexes
Preparation of Azido Complexes (1a-4a)
To a methanolic solution (5 mL) of appropriate metal salt
(1 mmol, 0.291 g, Co(NO3)2.6H2O, 0.241 g Cu(NO3)2.3H2O),
a methanolic solution of L (1 mmol, 0.256 g) was added while
stirring. To this, a methanolic solution (5 mL) of en (1 mmol,
0.060 g) or phen (1 mmol, 0.198 g) was added, followed by the
addition of NaN3(1 mmol, 0.065 g) in warm methanol. The re-
sultant mixture was refluxed for 3 h. The solid product obtained
was filtered, washed with methanol, and dried under vacuum
over CaCl2.
3a-b and 4a-b
1a-b and 2a-b
FIG. 1. Proposed molecular structure of the complexes (M = Co(II) or Cu(II);
X = N3 or NCS).
Physical Measurements
Elemental analysis (C, H, N and S) were performed on a
Thermo Finnigan FLASH EA-112 CHNS analyzer. Molar con-
ductance (ꢀM) was measured on the Elico (CM-185) conduc-
tivity bridge using ca. 10−3 M DMF solution. Electronic spectra
were recorded on a Shimadzu 3600 UV-visible-NIR spectropho-
tometer. Magnetic susceptibility was measured on Gouy bal-
Preparation of Thiocyanato Complexes (1b-4b)
A methanolic solution (5 mL) of ligand L (1 mmol, 0.256 g)
ance at room temperature using Hg[Co(NCS)4] as a calibrant. was added drop wise to a solution (5 mL) of appropri-
IR spectra were recorded on Perkin Elmer FT-IR spectrometer ate metal salt (1 mmol, 0.291 g, Co(NO3)2.6H2O, 0.241 g
2000 as KBr pellets in the 4000–400 cm−1 spectral range. The Cu(NO3)2.3H2O) in the same solvent followed by addition of
X-band ESR spectra of Cu(II) complexes have been recorded in en (1 mmol, 0.060 g) or phen (1 mmol, 0.198 g) and NH4NCS
the polycrystalline state at room temperature and in DMF solu- (1 mmol, 0.076 g) in warm methanol. The resultant mixture was
FIG. 2. ESR spectrum of 4b in DMF solution at 77 K.

594
V. A. SAWANT ET AL.
FIG. 3. TG, DTG and DTA curves of 4b.
refluxed for 3 h. The product obtained was filtered, washed with
methanol and dried under vacuum over CaCl2.
Infrared Spectra
The main stretching frequencies of the IR spectra of the
complexes are presented in Table 2. In the IR spectra of L,
ν(NH) band appear at 3248 cm−1 and absence of ν(SH) band
near 2600 cm−1 indicates the thione structural form of the lig-
and in solid state. The absence of ν(NH) band in the spectra
of all the complexes provides strong evidence for involvement
of ligand coordination in deprotonated form.[25] The charac-
teristic ν(C O) frequency of ligand L occurs at 1680 cm−1
remains unaltered in all complexes, ruling out the possibility
of coordination through carbonyl group of quinazoline lig-
and. The ligand L contains a thioamide group (-HN-C S)
and gives rise to four characteristic thioamide bands (I-IV)
RESULTS AND DISCUSSION
The reaction of ligand L with metal(II) salts in presence of
ethylenediamine or 1,10-phenanthroline and NaN3 or NH4NCS
yielded the complexes of the type [M(L)(en or phen)(H2O)(N3
or NCS)], as shown in Figure 1. The general reaction for the
formation of the complexes is shown as
M(NO3)2·nH2O + L + en or phen + NaN3 →[M(L)(en or
phen)(H2O)(N3)] (1a–4a)
M(NO3)2·nH2O + L + en or phen + NH4NCS →[M(L)(en
or phen)(H2O)(NCS)] (1b–4b)
M = Co(II) {n = 6} and Cu(II) {n = 3}; L = 2-mercapto-3-
phenyl-quinazolin-4(3H)-one; en = ethylenediamine, phen =
1,10-phenanthroline
The results of the elemental analysis of all the complexes
are in good agreement with those required by the proposed for-
mula. The complexes are insoluble in common organic solvents
except DMF and DMSO. The molar conductivity values of the
compounds in DMF (10−3mol dm−3) (Table 1) indicates that
they are non-electrolytic in nature.
at 1533, 1339, 988, and 842 cm−1 [26]
The thioamide band-
.
I [δ(NH) + δ(C-N)] observed at 1533 cm−1 in L splits up in
the spectra of the complexes suggest the coordination through
imino nitrogen atom of L. The two bands appearing at the
frequency 1339 cm−1 [ν(C N) +δ(NH) +δ(CH) +ν(C S)]
thioamide band-II and 842 cm−1 [ν(C S)] thioamide band-IV
in the spectra of L shifted to lower frequencies in the range
1305–1326 cm−1 and 832–839 cm−1 indicating coordination
of thione/thiolato sulfur. The thioamide band-III observed at

595

596
V. A. SAWANT ET AL.
TABLE 2
Infrared spectral data of metal complexes
Thioamide bands
II III IV
Selected
ν(phen)
Compound
νH2O
νNH2
νC O
νN3/νNCS
I
νM-N
1a
2a
3a
4a
1b
2b
3b
4b
3447, 816 3237, 3296 1704
3479, 818 3243, 3292 1675
2056, 1345
2057, 1346
2046, 1344
2056, 1342
1562, 1543 1317 988 839
1573, 1540 1320 986 835
1573, 1540 1314 979 838 1506, 1434, 848, 716 472
1568, 1542 1310 978 836 1505, 1445, 847, 719 464
-
-
469
465
3442, 816
3428, 820
-
-
1688
1707
3430, 816 3242, 3308 1693 2071, 764, 499 1562, 1534 1317 978 832
3489, 817 3243, 3292 1675 2073, 762, 485 1573, 1526 1305 976 835
-
-
469
469
3407, 819
3422, 819
-
-
1688 2070, 759, 495 1573, 1540 1326 974 832 1513, 1423, 845, 724 469
1698 2076, 762, 489 1578, 1542 1316 978 835 1510, 1426, 845, 724 454
Thioamide bands: Band-I (δNH + δC-N) Band-II (νC N + δNH + δCH + νC S) Band-III (νC S + νC N) Band-IV (νC S)
988 cm−1 in L also reduced in intensity on coordination with
to those reported for the unpaired electrons of Co(II) ion in
metal ion.[27]
an octahedral environment.[31] The electronic spectra of Cu(II)
The spectra of mixed en complexes (1a, 1b, 2a and 2b)
shows two characteristic bands at around 3232 and 3300 cm−1
assigned to νsym and νasymvibration of NH2 suggesting coordi-
nation through NH2.[28] The bands observed at around 1510,
1426, 845, and 720 in the mixed phen complexes (3a,3b, 4a
and 4b) due to ν(C N), ν(C C) and out-of-plane CH stretch-
ing vibrations of 1,10-phenanthroline, confirms the presence
of phen ligand in the coordination sphere of the complexes.
The azido complexes (1a–4a) show a sharp band at ∼2055
cm−1 and a strong band at ∼1346 cm−1. These are assigned
to υa and υs vibrations of the coordinated azido group.[29] The
thiocynate complexes (1b–4b) exhibit a strong sharp band at
∼2075 cm−1, a weak band at ∼762 cm−1 and another weak
band at ∼485 cm−1, which can be attributed to υ(CN), υ(CS)
and υ(NCS), respectively. These values are typical for N-bonded
thiocynate complexes.[30] In the spectra of all the complexes, a
broad band centered at ∼3440 cm−1 together with a new band
at ∼820 cm−1 indicates presence of water molecules in the
coordination sphere of the complexes.
complexes (2a, 2b, 4a, and 4b) shows a broad band centered
2
2
at around 690 nm that may be due to Eg → T2g transition
in octahedral environment. The observed magnetic moment of
1.84–1.89 µB for all the Cu(II) complexes support octahedral
geometry around Cu(II).[32]
ESR Spectra
The X-band ESR spectra of the Cu(II) complexes were
recorded in polycrystalline state at room temperature and in
DMF solution at 77 K. The ESR spectral assignments of the
complexes along with the spin Hamiltonian and orbital reduc-
tion parameters are summarized in Table 4.
The room temperature ESR spectra of all the Cu(II) com-
plexes (2a, 2b, 4a and 4b) in the polycrystalline state show
typical axial behavior with slightly different g and g val-
ꢀ
⊥
ues. The geometric parameter G, which is a measure of ex-
change interaction between the copper centers in polycrystalline
TABLE 3
Electronic spectra and magnetic moment values of the metal
complexes
Electronic Spectra and Magnetic Moments
The electronic spectra in dimethylformamide (10−4 mol
dm−3) and magnetic moment values of the metal complexes
are listed in Table 3. The transitions below 400 nm observed in
complexes may be attributed to usual π → π* and n → π*
transitions occurring within ligand orbitals. The electronic spec-
tra of Co(II) complexes (1a, 1b, 3a and 3b) display two bands
in the range of 652–698 and 484–496 nm that may be assigned
π → π∗and n → π*
d → d
transitions
(nm)
transitions and charge
Compound µeff µB transfer transitions (nm)
1a
2a
3a
4a
1b
2b
3b
4b
4.83
1.89
4.88
1.87
4.88
1.87
4.79
1.84
262, 299, 348
274, 304, 350
260, 304, 364
264, 296, 374
258, 274, 336
274, 296, 393
266, 304, 348
278, 304, 392
492, 662
704
496, 698
694
486, 652
726
484, 688
698
4
4
to 4T1g(4F) → A2g(4F) (ν2) and 4T1g(4F) → T1g(4P) (ν3), indi-
cating octahedral configuration around Co(II). The absorption
band due to 4T1g(4F) → T2g(4F) (ν1) is not often observed. This
4
might be due to presence of this band near IR region around
1237–1242 nm. The µeff value measured for the Co(II) com-
plexes are in the range 4.79–4.88 µB, which is fairly close

PROPERTIES OF PSEUDOHALIDE COMPLEXES
597
out-of-plane π-bonding, respectively, and orbital reduction fac-
tor K. The values of bonding parameters α2, β2 and γ 2 < 1.0
indicate significant in-plane σ-bonding and in-plane π-bonding.
The value of K and K which are the parallel and perpendic-
ꢀ
⊥,
ular components of orbital reduction factor, also provides in-
formation about the nature of bonding in the complexes. The
complexes show the value of K and K in order K < K which
ꢀ
⊥
ꢀ
⊥,
suggest the considerable in-plane π-bonding in the complexes.
The Fermi contact hyperfine interaction term K were ob-
tained from the equation.[34]
K = Aav/Pβ2 + (gav − 2.00277)/β2
where P is the free ion dipolar term and its value is 0.036. K is
dimensionless quantity and is generally found to have a value
of 0.30. The K values obtained for all the complexes are in
agreement with those reported for Cu(II) complexes.[35,36]
Thermal Analysis
The thermal decomposition studies of all Cu(II) complexes
were carried out up to 1200◦C under N2 atmosphere. Typical
TG, DTG, and DTA curves of 4b are presented in Figure 3, and
FIG. 4. Cyclic voltammogram of 4a.
compound, is calculated using the equation G = (g − 2.0023)/ thermal analysis data is summarized in Table 5.
ꢀ
⊥
(g > 2.0023). In all the Cu(II) complexes, g > g > 2.0023
The thermal decomposition process of azide complexes 2a
⊥
ꢀ
and G values within the range 3.69–4.04 are consistent with the and 4a involves four decomposition stages. The first stage takes
dx2−y2 ground state.[33]
place in the range 158–189◦C and 179–213◦C, with endother-
The ESR spectra of all the Cu(II) complexes in DMF solution mic DTA peaks at 176◦C (2a) and 201◦C (4a), respectively,
at 77K (Figure 2) possesses well resolved hyperfine spectra that corresponding to mass loss 4.57 and 3.62% of coordinated wa-
was unresolved at room temperature suggesting that complexes ter molecule (Calc. % = 4.12 and 3.23). The second stage occurs
are monomer. No band corresponding to forbidden magnetic in the range 189–276◦C and 213–354◦C accompanied by a mass
dipolar transition (ꢂMs = 2) was observed in the spectra loss of 9.87 and 7.71%, respectively, and may be attributed to
of the complexes also support the complexes are mononuclear. the decomposition of the azide ion with endothermic DTA peaks
The spectra presents four lines in the g region giving g > g
⊥
2.0023, corresponding to the presence of an unpaired electron third stage corresponding to the mass loss of 31.26 and 46.08%
>
at 228◦C (2a) and 296◦C (4a) (Calc. % = 9.61 and 7.54). The
ꢀ
ꢀ
in the dx2−y2 orbital. The g values for all the Cu(II) complexes may be attributed to the decomposition of half molecule of the
ꢀ
are less than 2.3, which is an indication of significant covalent ‘L’ and ethylenediamine or 1,10-phenanthroline (Calc. % =
bonding in these complexes.
31.39 and 46.19) in the 276–568◦C and 354–673◦C range, re-
The ESR parameters g , g ,gav, A and A and the energies spectively. The DTA curve gives endothermic peaks at 380 and
ꢀ
⊥
ꢀ
⊥
of the d-d transitions were used to evaluate the bonding param- 457◦C for complex 2a and at 454 and 562◦C for 4a. In the
eters α2, β2 and γ 2, which may be regarded as measures of fourth stage (568–1070 and 673–1182◦C), a mass loss of 40.24
covalency of the in-plane σ-bonding, in-plane π-bonding and and 31.46% corresponding to the decomposition of the rest of
TABLE 4
ESR spectral assignments for Cu(II) complexes in polycrystalline state (298 K) and solution (77 K)
Polycrystalline state (298 K)
DMF solution (77 K)
Aaꢀ Aa⊥ Aaav α2
Complex
g
ꢀ
g
⊥
gav
g
ꢀ
g
⊥
gav
G
β2
γ 2
K
K
K
ꢀ
⊥
2a
2b
4a
4b
2.239 2.066
2.208 2.056
2.167 2.053
2.271 2.066
2.124
2.107
2.091
2.134
2.271 2.073 2.139 158.9 18.7 65.4 3.80 0.780 0.738 0.777 0.575 0.606 0.43
2.227 2.063 2.118 163.6 15.8 65.1 3.69 0.746 0.657 0.713 0.490 0.531 0.45
2.249 2.066 2.127 163.6 21.5 68.8 3.82 0.768 0.668 0.699 0.513 0.537 0.47
2.263 2.066 2.132 154.3 18.7 65.4 4.04 0.756 0.745 0.741 0.563 0.560 0.42
a
Expressed in units of cm−1multiplied by a factor of 10−4
.

598
V. A. SAWANT ET AL.
TABLE 5
Thermal behavior of Cu(II) complexes
Thermogravimetry (TG)
Mass loss (%)
found calculated
Compound
Stage
Temp. range (◦C)
DTA peak (◦C)
Decomposition product loss
2a
I
II
III
IV
I
158–189
189–276
276–568
568–1070
147–194
194–288
288–547
547–1064
179–213
213–354
354–673
673–1182
161–225
225–373
373–679
679–1152
176
228
380, 457
985
168
212
334, 496
870
201
4.57
9.87
31.26
40.24
3.84
12.94
30.19
38.73
3.62
4.12
9.61
31.39
40.32
3.97
12.82
30.27
38.89
3.23
H2O
N3
C2H8N2, C6H5
C8H4N2OS
H2O
2b
4a
4b
II
NCS
III
IV
I
C2H8N2, C6H5
C8H4N2OS
H2O
II
296
7.71
7.54
N3
III
IV
I
II
III
IV
454, 562
1107
210
304
412, 552
1090
46.08
31.46
3.09
10.07
44.77
30.62
46.19
31.62
3.14
10.13
44.89
30.74
C12H8N2, C6H5
C8H4N2OS
H2O
NCS
C12H8N2, C6H5
C8H4N2OS
the molecule of ‘L’ was obtained leaving anhydrous CuO (Calc.
% = 40.32 and 31.62).
The electrochemical potentials of the Cu(II) complexes were
characterized by well-defined redox process in positive potential
In thiocynate complexes 2b and 4b, the first stage takes place side. Since the ligand used in this work is not reversibly oxidized
in the 147–194◦C and 161–225◦C range, corresponding to mass or reduced in the applied potential range, the redox processes
loss of 3.84 and 3.09%, respectively, due to loss of coordinated are assigned to the metal centers only. In positive potential side,
water molecule (Calc. % = 3.97 and 3.14) with endothermic all the complexes exhibit reduction peak at Epc, 1.021 to 1.058
DTA peaks at 168◦C (2b) and 210◦C (4b). The second stage oc- V with direct re-oxidation peak at Epa, 1.001 to 1.026 V cor-
curs in the 194–288◦C and 225–373◦C range accompanied by responding to the Cu(II)/Cu(III) couple. The values of the lim-
a mass loss of 12.94 and 10.07%, respectively, corresponding iting peak-to-peak separation (ꢂEp) ranging from 0.012–0.036
to the decomposition of the thiocynate ion (Calc. % = 12.82 V reveal that the process is reversible as the limiting peak po-
and 10.13) with endothermic DTA peaks at 212◦C (2b) and tential is lower than 59 mV. Further, the redox processes for
304◦C (4b). The third stage takes place in the 288–547◦C and Cu(II) complexes of phen (4a and 4b) appear at more positive
373–679◦C range, corresponding to the mass loss of 30.19 and potential (1.022 to 1.042 V) as compared to those for corre-
44.77%, respectively, and may be attributed to the decomposi- sponding en complexes 2a and 2b (1.013 to 1.021 V). This trend
tion of half molecule of the ‘L’ and ethylenediamine or 1,10-
phenanthroline (Calc. % = 30.27 and 44.89). The DTA curve
TABLE 6
gives two endothermic peaks at 334 and 496◦C for complex 2b
Electrochemical data of Cu(II) complexes
and 412 and 552◦C for 4b. The fourth stage takes place in the
547–1064 and 679–1152◦C range corresponding to the mass
loss of 38.73 and 30.62%, respectively, corresponding to the
decomposition of the remaining half molecule of ‘L’, leaving
anhydrous CuO (Calc. % = 38.89 and 30.74).
Metal oxidation
Ligand reduction
Epa
Epc
(V)
ꢂEp E1/2
(V) (V)
Epa
(V)
Epa
(V)
Compound (V)
2a
2b
4a
4b
1.001 1.025 0.024 1.013 −0.140 −0.961
1.009 1.021 0.012 1.021 −0.056 −1.034
1.004 1.040 0.036 1.022 −0.076 −0.941
1.026 1.058 0.032 1.042 −0.020 −0.953
Cyclic Voltammetry
Electrochemical properties of the Cu(II) complexes (2a, 2b,
4a and 4b) were investigated in DMF solutions (10−3mol dm−3
)
at room temperature in the potential range +1 to −1.5 V with
scan rate 50 mVs−1. Typical cyclic voltammogram (CV) of
complex 4a is shown in Figure 4 and the electrochemical data
obtained is represented in Table 6.
Supporting electrolyte: n-Bu4NClO4 (0.05 M); complex: 0.001 M;
solvent: DMF; ꢂEp = Epa- Epc where, Epa and Epc are anodic and
1
cathodic potentials, respectively; E1/2 = / ( E + E ); scan rate: 50
2
pa
pc
mVs−1
.

PROPERTIES OF PSEUDOHALIDE COMPLEXES
599
may be due to the strong σ-donor tendency of the ethylene- 15. Gudasi, K.B., Patil, S.A., Vadavi, R.S., Shenoy, R.V., and Nethaji,
M. Crystal structure of 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-
methoxybenzylamino]-1,2-dihydro-quinazolin-4(3H)-one and the synthe-
sis, spectral and thermal investigation of its transition metal complexes.
Transition Met. Chem., 2006, 31(5), 586–592.
diamine moiety and the strong π-acceptor ability of 1,10-
phenanthroline ligand. These results are consistent with those
reported in the literature.[18]
16. EI-Mehasseb, I.M., Ramadan, A.M., and Issa, R.M. Catecholase
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17. Gudasi, K.B., Patil, S.A., Vadavi, R.S., Shenoy, R.V., and Nethaji, M.
Transition metal complexes of a potential anticancer quinazoline ligand.
Transition Met. Chem., 2009, 34(3), 325–330.
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