Spectral, ligating properties, and electrical conductivity of some azo-nitroso metal complexes

Article abstract of DOI:10.1080/15533174.2013.776589

Synthesis and characterization of new complexes derived from the interaction of 2,4-dinitrosoresorcinol (DNR) and 6-(o-substituted phenylazo)-2,4-dinitrosoresorcinol (X = -H, -OH, -COOH) with metal [Cr(III), Fe(III), Co(II), Ni(II) and Cu(II)] salts are r

Full text of DOI:10.1080/15533174.2013.776589

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 44:402–412, 2014
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.776589
Spectral, Ligating Properties, and Electrical Conductivity
of Some Azo-Nitroso Metal Complexes
Mamdouh S. Masoud,1 Ekram A. Khalil,1 Ahmed M. Ramadan,1,2
Samah A. Mokhtar,1 and Osama F. Hafez1,3
1Faculty of Science, Department of Chemistry, Alexandria University, Alexandria, Egypt
2Faculty of Science, Department of Chemistry, King Khalid University, Abha, 5 Saudi Arabia
3Faculty of Medicine, Chemistry Department, Dammam University, Dammam, Saudi Arabia
light on the mechanism of the electrical conductivity of the
ligands and their metal complexes and relate the mechanism
to their physicochemical properties, and (d) study the thermal
behavior of iron complexes.
Synthesis and characterization of new complexes derived
from the interaction of 2,4-dinitrosoresorcinol (DNR) and 6-
(o-substituted phenylazo)-2,4-dinitrosoresorcinol (X = -H, -OH,
-COOH) with metal [Cr(III), Fe(III), Co(II), Ni(II) and Cu(II)]
salts are reported. The structures of the complexes are achieved
based on elemental analysis, spectral (UV, visible, and IR). The
electrical conductivity of some ligands and their complexes favored
their semiconducting properties. The thermodynamic parameters
of thermal decompositions are evaluated.
EXPERIMENTAL
Synthesis of the Ligands
2,4-dinitrosoresorcinol (DNR) I (Scheme 1) was prepared as
reported.[9] 6-(o-substituted phenylazo)-2,4-dinitrosoresorcinol
compounds II (Scheme 1) were prepared by direct diazotiza-
tion of aniline (X = -H) and its derivatives (o-aminophenol,
o-amino benzoic acid X = -OH, -COOH respectively) followed
by coupling with DNR.
Keywords azo-nitroso, conductivity, metal complexes, spectral mea-
surements, thermal analysis
INTRODUCTION
In view of the role played by nitroso complexes in body
systems, delineation of the nature of the metal binding and the
stereochemistry in nitroso complexes seems to be interesting.
The azo group has great interest for various reasons, as models
of biological systems, antifungals, and analytical reagent.[1,2]
The rich chemistry of the azo compounds is associated with
several important biological reactions such as protein synthesis,
carcinogenesis, azo reduction monoamine oxidase inhibition
mutagenic, immunochemical affinity labeling, nitrogen fixation,
and important medical and industrial uses.[3] This article is part
of a continuing investigation of the ligating properties of com-
pounds containing both azo and nitroso chromophoric groups
with different transition metals.[4–8] The major interest of this
study was (a) synthesis of the entitled ligands and their com-
plexes, (b) assigning the structures of the complexes based on
spectroscopic measurements and elemental analysis, (c) throw
Synthesis of Transition Metal Complexes
The complexes of the chromium(III) chloride, iron(III) chlo-
ride, and the acetates of cobalt(II), nickel(II), and copper(II)
were prepared by mixing the required weights of the metal salts
(except Cr complex) with the corresponding ligand in ethanol.
In case of Cr(III) complexes, both the metal salt and the lig-
and were dissolved in dioxane. The formed complexes were
filtered, washed several times with alcohol, and dried in a vac-
uum desiccator over P4O10. The metal content [Fe(III), Co(II),
Ni(II), and Cu(II)] were determined by usual complexometric
titration procedures.[10] The Cr(III) content was determined us-
ing Perkin-Elmer 2380 Atomic Absorption Spectrophotometer.
Carbon, hydrogen, nitrogen, and halogen contents were deter-
mined. The analytical data suggest a range of stoichiometries
1:1, 1:2, 1:3, and 2:1 (M:L; Table 1, Schemes 2–5).
Spectral Measurements
The KBr disc infrared spectra of the ligands and their com-
plexes were measured in the range 200–4000 cm−1 using a
Perkin-Elmer 1430 spectrophotometer.[11] The Nujol mull elec-
tronic spectral measurements were made using Unicam SP 1750
Ultraviolet spectrophotometer.[12]
Received 2 November 2011; accepted 10 February 2013.
Address correspondence to Ahmed M. Ramadan, Faculty of Sci-
ence, Department of Chemistry, Alexandria University, Alexandria,
Egypt. E-mail: dramramadan@yahoo.com
402

403

404
M. S. MASOUD ET AL.
SCH. 1. The structure of the ligands.
0.12 mm thickness. The samples were hold between two cop-
Conductivity Measurements
per electrodes with a silver paste in-between and then inserted
with the holder vertically into a cylindrical electric furnace. The
circuit used to measure the electrical conductivity consists of
These were measured in the temperature range 294–435 K.
The samples were prepared in the form of tablets at a pres-
sure of 4 tons cm−2. The tablets were of an area 1.37 cm2 and
SCH. 2. The structure of H2L1 complexes.

SPECTRAL STUDIES OF SOME AZO-NITROSO METAL COMPLEXES
405
SCH. 3. The structure of H2L2 complexes.
d.c. regulated power supply Heath Kit (0–400 volts) and Keith- potential drop across the sample of the cross-section area a and
ley multimeter for measuring current with a sensitivity up to thickness d.
10−15 amp. The temperature of the sample was measured within
Thermal Analysis
Differential thermal analysis of iron complexes was per-
formed on Dupont 9900 computerized thermal analyzer. A
0.1◦ by means of copper constant thermocouple. The conduc-
tivity of the sample was obtained using the general equation:
σ = I d / Vc a, where I is the current in ampere, Vc is the
SCH. 4. The structure of H3L3 complexes.

406
M. S. MASOUD ET AL.
SCH. 5. The structure of H3L4 complexes.
60 mg sample was placed in a platinum crucible. Dry nitro-
All the ligands gave νNO overlapped with νN=N at
gen was flowed over the sample at a rate 15 cm3 min−1 and a (1483–1484, 1388–1390) cm−1 and δNO at (843–844) cm−1
chamber cooling water flow rate was 10 L h−1.The speed was to suggest the presence of different tautomers: azo-nitroso phe-
5 mm min−1. The heating rate of the DTA was 10◦/min−1
.
nol, azo-keto oxime and azo-nitroso oxime.[13] The pattern goes
parallel to that of the dinitrosoresorcinol (DNR).
IR Studies of the Complexes
RESULTS AND DISCUSSION
IR Studies of Ligands
The infrared spectra of the metal complexes (Table 2) com-
pared with those of the free ligands, Figure 1 as an exam-
The free DNR ligand (Table 2) gave well-defined ir bands[13] ple, showed that the vibrational frequencies of coordinated
that indicated the presence of equilibrium of nitoso-phenol functional groups (e.g., νOH, νC=O, νCOO-, νN=N, νNO, δNO
,
↔ keto-oxime involving intramolecular hydrogen bonding ac- and νNOH) are affected with different degrees depending on
companied by the possible existence of cis and trans iso- the strength of the π-interaction occurring between the metal
mers.[14] Similarly, the ir spectra of -H, -OH, and -COOH ion and π-electrons of the functional groups.[15–21] Some of
.
o-substituted phenylazo ligands (Table 2) gave well-defined the νC=O, νC=N, and νNOH disappeared and others are slightly
bands in the frequency range 3512–3531 cm−1 (νOH of oxime), shifted, probably due to tautomerization to the nitrosophenol
3391–3393 cm−1 (νOH of phenolic OH). The other two bands at tautomer. νOH, νC-O, νNO, and δNO are disappeared and others
(3161–3162) and (2749–2759) cm−1 are due to phenolic -OH are slightly shifted, probably due to tautomerization to the keto-
involved in hydrogen bonding.
oxime form. The νN=N is nearly unaffected in all complexes
Different types of hydrogen bonding are possible[5]: (a) H- except in Ni, Cu[-H3L3]; Co, Ni, and Cu[-H3L4]. So, the azo
bonding of the O-H. . .N type between the -OH and the -N = N- group may participate in complexation.
groups, (b) H-bonding of the O-H. . .O type between the oximic-
Most DNR nuclei coordinate only with the metal ion where
OH and the ketonic oxygen in the oxime structure, and (c) the mode of bonding proceeds via the phenolic oxygen and ni-
intermolecular hydrogen bonding of the O-H. . .O or O-H. . .N troso or oxime group. In most azo-nitroso complexes, where the
types. The appearance of a band at (822–992) cm−1 in the H3L4 azo group was affected, the mode of bonding proceeds through
ligand indicated the presence of intermolecular hydrogen bond- phenolic oxygen and azo group for the bidentate ligand. How-
ing between the carboxylic groups of two different molecules.
ever, in the Ni[-H3L3, -H3L4] complexes, the mode of bonding

407

408
M. S. MASOUD ET AL.
[-H3L4], the ligand acts as a tridentate through phenolic oxygen
and one nitroso group in the keto-oxime form to the first M(II),
while the second M(II) coordinates via keto oxygen, azo group,
and carboxy group (substituent).
Nujol Mull Electronic Spectral Measurements
The μeff (298 K) and nujol mull electronic spectra of com-
plexes (Table 1) typified that all the Cr(III) are of octahedal ge-
4
ometry with 4A2g → T1g transition. However, all Fe, Co[DNR,
H2L2, H3L3, -H3L4], and Ni[DNR, -H2L2) are of octahedral ge-
5
5
4
4
3
ometry with E2g → T2g, T1g (F) → T1g (p), and T2g
→
3T1g(p) transition for iron, cobalt, and nickel, respectively. The
Ni[DNR, -H2L2) and Cu[DNR, -H3L4) are of square planar ge-
ometry with transitions 1A1 (F) → B1 (G) and 2B1g → B2g for
Ni(II) and Cu(II), respectively, while the Cu[H3L3, H3L4] are of
tetrahedral structure. The Mo¨ssbauer parameters[4] for the com-
plex Fe-DNR (1:3) gave two bands, each of doublet nature to
assign the presence of high-spin iron(III) and low-spin iron(II).
These observations led us to suggest the occurrence of a partial
reduction of the iron during the progress of complexation of
iron salt with the nitroso ligands.
1
2
Electrical Conductivity Measurements
The temperature dependence of the electrical conductivity
of the organic ligands (DNR, H2L2, H3L3, and H3L4) and their
Fe(III), Co(II), Ni(II), and Cu(II) complexes obeys the follow-
ing equation[22]: σ = σ◦ exp –DE / 2KT, where σ and ꢀE are
the specific conductivity and the activation energy, respectively.
σ◦ is a pre-exponential constant term, and K is Boltzmann con-
stant. The ꢀE and log σ◦ value are evaluated and correlated
(Table 3) to assign semiconducting trend.[23,24] The log σ – 1/T
relationship for the metal-free ligands is shown in Figure 2 as
an example.
The curves showed more than one straight line intersect with
each other at a characteristic transition temperature (four re-
gions: A, B, C, D) for DNR; (three regions: A, B, C) for H3L3,
H3L4 and (two regions: A, B) for -H ligand. All the regions are
with positive temperature coefficient conductivity except the
regions (B, C; B) are with a negative temperature coefficient
FIG. 1. Infrared spectra of H2L2 ligand and its metal complexes.
proceeds via the (keto or phenolic oxygen) and azo group where for DNR and H2L2, respectively, while region B behaves as an
the ligand is of tridentate attachment. In case of bimetallic com- insulator in case of H3L3, H3L4 compounds.
plexes 2:1 (M:L) Ni-H3L3; Ni, Cu[-H3L4], the ligands act as a
The negative temperature coefficient of regions B, C is char-
bi-tridentate and tri-tridentate bonding, respectively. In the Co- acterized by the decrease of conductivity as the temperature
H3L4 complex, the ligand is bonded through keto-oxygen, azo increased. This results of scattering of carriers by photons,
group, and two carboxy groups (substituent and acetate groups) due to lattice vibrations within the temperature range, [DNR
where the latter group is of a bidentate behavior. In case of the (60–100◦C); (100–120◦C), H2L2 (50–130◦C], covering this re-
ligand [-H2L2], the new ir bands appeared at 368 cm−1 and at gion.[4]
316 cm−1 for Cr(III), Fe(III), Co(II), and Cu(II) complexes are
due to νM-O and νM-N, respectively.
The region A exhibits an increase of conductivity as the
temperature is increased with a relatively low activation energy
The overlapping region (νN=N and νNO) are nearly unaffected [DNR (0.232 eV), H2L2 (0.218 eV), H3L3 (0.317 eV), H3L4
in Fe(III) complexes (i.e., the azo group is not involved in Fe(III) (0.187 eV)], due to the activation from the donor level to the
complexes, and the ligand is of bidentate bonding). However, in conduction band (i.e., an extrinsic behavior). However, region
case of Co(II), Ni(II), and Cu(II), the azo group is affected with C in the H3L4 compounds has a positive temperature coefficient
different degree. But in case of Ni(II) and Cu(II) complexes with with an activation energy higher than that of region A (0.548 eV).

SPECTRAL STUDIES OF SOME AZO-NITROSO METAL COMPLEXES
409
TABLE 3
Electrical conductivity data of ligands and their complexes
−log σ◦
Transition
Compound
Region
ꢀE (eV)
(ohm−1 cm−1
)
Temperature (◦K)
σ (ohm−1 cm−1
)
DNR (H2L1)
A
B
C
D
A
B
C
A
B
A
B
C
A
B
A
B
A
B
C
D
A
B
C
A
B
A
B
A
B
C
A
B
C
A
B
A
B
A
B
C
A
B
C
A
B
A
B
C
0.232
−0.113
−1.724
1.580
05.29
10.55
30.05
12.46
03.68
13.17
01.74
04.43
15.15
03.89
07.69
03.58
07.33
14.12
05.69
09.93
04.29
23.38
07.98
02.81
03.74
09.26
03.57
05.98
13.79
09.21
13.26
3.323
—
5.050
14.59
17.54
10.47
06.49
10.59
07.57
11.52
07.13
10.23
14.18
05.88
—
333
373
393
1.46×10−9
7.08×10−10
1.29×10−8
Fe(HL1)3
0.313
333
353
3.7×10−9
−0.313
2×10−9
0.492
Co(H2L1)(HL1)Ac
Ni(HL1)Ac. H2O
0.297
333
383
333
363
9.77×10−10
1.86×10−10
2.82×10−9
3.02×10−9
−0.412
0.310
0.056
0.352
0.134
[Cu(H2L1).2Ac] 2H2O
H2L2
343
403
323
4.9×10−10
1.12×10−10
7.94×10−10
−0.328
0.218
−0.054
0.238
Fe(HL2)2Cl .H2O
323
343
363
9.55×10−9
1.26×10−9
1.4×10−9
−0.981
0.062
0.435
0.317
Co(H2L2)(HL2)Ac
333
363
3.05×10−9
−0.049
2.69×10−9
0.355
Ni(HL2). Ac
Cu(HL2). Ac
H3L3
0.168
323
323
2.4×10−9
1.8×10−9
−0.341
−0.030
−0.285
0.317
—
0.215
−0.386
−0.575
0.097
323
—
343
323
343
5.89×10−9
—
5.89×10−9
3.02×10−9
8.91×10−10
[Fe(H3L3)(H2L3)2] Cl. H2O
Co(H2L3)Ac. 2H2O
Ni2(H2L3).3Ac. 4H2O
[Cu(H2L3).Ac] 3H2O
0.109
323
6.31×10−9
−0.152
0.052
333
353
323
343
4.47×10−9
2.95×10 − 9
2.09×10−9
1.7×10−9
−0.209
0.099
−0.099
−0.367
0.187
—
0.548
−0.484
−0.074
0.275
H3L4
383
—
403
343
4.57×10−9
—
01.48
16.17
10.17
04.35
12.02
05.31
4.57×10−9
[Fe(H3L4)(H2L4)2] Cl
Co(H2L4)Ac
8.51×10−10
333
393
2.88×10−9
1.26×10−9
−0.237
0.278

410
M. S. MASOUD ET AL.
TABLE 3
Electrical conductivity data of ligands and their complexes (Continued)
- log σ◦
Transition
Compound
Region
ꢀE (eV)
(ohm−1 cm−1
)
Temperature (◦K)
σ (ohm−1 cm−1
)
Ni2L4.Ac. 5H2O
A
B
C
A
B
0.079
−0.611
−0.135
0.097
07.44
18.27
11.19
07.05
12.66
323
343
2.09×10−9
5.88×10−10
[Cu2(HL4).2Ac.H2O] .2H2O
333
3.02×10−9
−0.273
This assigns an intrinsic region of conductivity, where the con-
duction is from the valence to the conduction bands.[4] While
region C in the -OH compounds has a positive temperature co-
efficient with an activation energy (0.215 eV) lower than that
of region A, probably due to the presence of extrinsic behavior
rather than intrinsic one.
On dealing with the electrical conductivity properties of the
metal complexes compared with their metal-free ligands (DNR,
H2L2, H3L3, H3L4), Figure 3 as an example.
FIG. 3. Temperature dependence of the electrical conductivity of DNR and its
complexes.
FIG. 2. Temperature dependence of the electrical conductivity of different
ligands.

SPECTRAL STUDIES OF SOME AZO-NITROSO METAL COMPLEXES
411
The magnitudes of the conductivities of the ligands and their
Thermal Studies
The DTA data of the prepared iron complexes of DNR, H2L2,
H3L3, and H3L4 ligands and all the thermodynamic values and
assignments are given in Table 4. Based on least square calcu-
lations, the Ln ꢀT versus 1000/T plots for all complexes, for
each DTA curve, gave straight lines from which the activation
energies were calculated according to the methods of Piloyan
et al.[25] The slope is of Arrhenius type and equals–E / R.
The thermal properties of iron complexes gave a number of
exothermic peaks. The first peak in all complexes is assigned to
a dehydration process. Once desolvated, the complexes are sub-
jected to decomposition of nearly the same manner and all ended
with the formation stable metal oxide (Fe2O3).[26] The thermo-
dynamic parameters of the decomposition are calculated. The
fraction appeared in the calculated order of the thermal reac-
tions, n, confirmed that the reactions proceeded in complicated
mechanisms.
metal complexes along with the values of the energy gaps fa-
vor assignment to a faint semiconducting behavior rather than
metallic conductors where the metal ion forms a bridge to fa-
cilitate the flow of the current (Table 3). However, promotion
of electrons from ground to excited states may be necessary
before conduction occurs. Hence, the electrons in the available
orbitals of the complexes are not of high mobility. In general, the
lower conductivity weakens the conjugation in the chelate rings
involved in the complex formation due to packing property.[4,24]
The breaks in the conductivity curves of the metal-free lig-
ands is retained in their metal chelate complexes where log σ
– 1000/T relationship showed two, three, or four segments with
variable activation energies (Table 3) probably due to different
crystallographic or phase transitions.[4,24]
The Cu-DNR and Co-DNR complexes reveal no change in
conductivity with increasing temperature within the temperature
range (130–150◦C, 110–140◦C) to be of an insulator properties.
The regions A and C has a positive temperature coefficient
in all complexes [except for (Cu-H2L2, Fe-H3L3, Fe-H3L4) and
(Cu-H3L3, Ni-H3L4)], as a result of scattering of carriers by
photons, due to lattice vibrations within the temperature range
covering this region.[4]
The octahedral Fe-DNR complex, [1:3], gave a horizontal
line extending up to 433.0 K showing its great stability up to
this temperature. The band at 486.7 K is corresponding to the
decomposition start of the complex.
A well noticeable observation is recorded for nitroso com-
plexes where many DTA peaks have high values of energy of
activation (Table 4). This is probably due to complicated de-
composition of such complexes and oxidation of the organic
matter with the formation of different products (e.g., nitrogen
oxides [NO, NO2], metal oxides, organic products).[27] Also, the
trend goes in harmony with the increasing molecular weights
of the complexes because as the molecular weight increases the
energy for decomposition increases.
The straight line relation of ꢀE versus log σ◦ (Figure 2) as-
sists the deduction of empirical equations based on least square
method of calculations as follows:
ꢀEi = 0.067 log σ◦ + 0.741 For DNR, H2L2, H3L3, H3L4
i
ligands
ꢀEi = 0.067 log σ◦ + 0.602 for iron complexes
ꢀEi = 0.066 log σ◦i + 0.550 for cobalt complexes
ꢀEi = 0.065 log σ◦i + 0.561 for nickel complexes
ꢀEi = 0.066 log σ◦ii + 0.578 for copper complexes
The position of the peak is defined by the peak temperature,
Tm, at which the peak maximum or minimum occurs. The values
of the decomposed substance fraction αm, at maximum devel-
TABLE 4
Thermal properties of iron complexes of DNR (H2L1), H2L2, H3L3, and H3L4 ligands
Ea
ꢀS#
ꢀH#
Complex
Fe(HL1)3
Tm ◦K KJ mol−1
n
αm
KJK−1mol−1 KJ mol−1 Z s−1
Assignment
486.7
504.2
397.3
489.5
511.9
166.28
388.26
374.13
192.88
99.77
1.22 0.59
0.82 0.67
1.19 0.60
0.63 0.71
0.81 0.67
0.69 0.70
−0.241
−0.238
−0.235
−0.240
−0.243
−0.244
−117.3
−120.0
−093.4
−117.5
−124.4
−116.6
2.75
3.73
4.34
2.89
2.30
1.80
Decomposition of the complex
Formation of Fe2O3
Loss of H2O
Decomposition of the complex
Formation of Fe2O3
Loss of H2O
Fe(HL2)2Cl .H2O
[Fe(H3L3)(H2L3)2] 478.0
Cl. H2O
38.41
499.9
520.0
62.11
20.79
41.57
0.79 0.68
1.06 0.62
1.08 0.62
−0.243
−0.246
−0.241
−121.5
−127.9
−92.8
2.03
1.50
1.96
Decomposition of the complex
Formation of Fe2O3
Dehydration reaction
[Fe(H3L4)(H2L4)2] 385.0
Cl
497.6
525.0
187.07
166.28
0.57 0.73
1.11 0.61
−0.240
−0.242
−119.4
−127.1
2.84
2.67
Decomposition of the complex
Formation of Fe2O3

412
M. S. MASOUD ET AL.
opment of the reaction were calculated from the equation[28]
:
7. Masoud, M.S.; El-Merghany, A.; Abd El-Kaway, M.Y. Synth. React. Inorg.
Met.-Org. Nano-Met. Chem. 2009, 39, 537.
8. Masoud, M.S.; Hagagg, S.S.; Ali, A.E.; Nasr, N.M. J. Mol. Struct. 2012,
1014, 17.
9. Orndorff, W.K.; Nichols, M.L. J. Am. Chem. Soc. 1923, 45, 1536.
10. Schwarzenbach, G. In Complexometric Titration, H. Irving (Ed.); Methuen,
London, 1957.
(1 – αm) = n1/1– n
It is of nearly the same magnitude and lies within the range
0.59–0.73.
The values of collision factor, Z, can be obtained in case of
Horowitz Metzger by making the use of the relation[29]
:
11. Nakamoto, K. Infrared Spectra of Inorganic and Coordination compounds;
ꢀ
ꢁ
ꢀ
ꢁ
Wiley, New York, 1963.
E
E
RTm2
KTm
h
ꢀS#
R
12. Lee, R.H.; Griswold, E.; Kleinberg, J. Inorg. Chem. 1964, 3, 1278.
13. El-Tabl, A.S.; El-Saied, F.A.; Al-Hakimi, A.N. Transition Met. Chem. 2007,
32, 689.
Z =
φ exp
=
exp
RTm
Where ꢀS# is the entropies of activation. R represents molar
gas constant, φ is rate of heating (K s−1), k is the Boltzmann
constant, and h is the Planck’s constant. The calculated values
of the collision number, Z (Table 4), showed a direct relation to
Ea. The change in enthalpy (ꢀH#) for any phase transformation
taking place at any peak temperature, Tm, can be given by the
following equation[30]: ꢀS# = ꢀH# / Tm
14. Lemos, A.; Lourenco, J.P. Tetrahedron Lett. 2009, 50, 1311.
15. Manoj, E.; Kurup, M.R.P.; Punnoose, A. Spectrochim. Acta Part A 2009,
72, 474.
16. Refat, M.S.; El-Korashy, S.A.; Ahmed, A.S. Spectrochim. Acta A 2008, 71,
1084.
17. Nakamoto, K.; Rundle, R.E. J. Am. Chem. Soc. 1956, 78, 1113.
18. Masoud, M.S.; Soayed, A.A.; Ali, A.E. Spectrochim. Acta Part A 2004, 60,
1907.
19. Masoud, M.S.; Khalil, E.A.; Hafez, A.M.; El-Husseiny, A.F. Spectrochim
Acta Part A 2005, 61, 989.
Change of entropy values, ꢀS#, for all complexes are nearly
of the same magnitude and lie within the range −0.235 to
−0.246 kJ K−1. So, the transition states are more ordered (i.e.,
in a less random molecular configuration than the reacting com-
plexes).
20. Yoshino, J.; Kano, N.; Kawshima, T. Tetrahedron 2008, 64, 7774.
21. Mondal, T.K.; Dinda, J.; Cheng, J.; Lu, T.H.; Sinha, C. Inorg. Chim. Acta
2008, 361, 2431.
22. Emmert, F.L.; Thomas, J.; Hon, B.; Gengenbach, A.J. Inorg. Chim. Acta
2008, 361, 2243.
23. Kala, U.L.; Suma, S.; Kurup, M.R.P.; Krishnan, S.; John, R.P. Polyhedron
2007, 26, 1427.
24. Garrett, C.G.B. Organic semiconductors. In Semiconductors, N.B. Hannay
REFERENCES
1. Zhang, B.; Cox, S.B.; McMurry, S.T.; Jackson, W.A.; Cobb, G.P.; Anderson,
(Ed.); Reinhold, New York, 1959.
T.D. Environ. Pollut. 2008, 153, 658.
2. Okada, Y.; Hihara, T.; Morita, Z. Dyes Pigments 2008, 78, 179.
3. Lohse, E. Pharmazie 1986, 41, 815.
4. Masoud, M.S.; Abou El-Enein, S.A.; El-Shereafy, E. J. Therm. Anal. 1991,
37, 365.
5. Masoud, M.S.; Hindwvey, A.M.; Mostafa, M.A.; Ramadan, A.M. Spec-
trosc. Lett. 1997, 30, 1227.
6. Masoud, M.S.; Soayed, A.A.; Ali, A.E.; Sharsherh, O.K. J. Coord. Chem.
2003, 56, 725.
25. Piloyan, G.O.; Ryabchikov, I.D.; Novikova, O.S. Nature 1966, 212, 1229.
26. Stefan, S.L. J. Therm. Anal. 1994, 42, 1299.
27. Masoud, M.S.; Haggag, S.S.; Ramadan, A.M. Transition Met. Chem. 1998,
23, 343.
28. Oswald, H.R.; Dubler, E. In Thermal Analysis, H.G. Wiedemann (Ed.),
Birkhauser, Basel, Switzerland, 1972.
29. Horowitz, H.; Metzger, G. Anal. Chem. 1963, 35, 1464.
30. Dhar, M.L.; Singh, O. J. Therm. Anal. 1991, 37, 259.

Copyright of Synthesis & Reactivity in Inorganic, Metal-Organic, & Nano-Metal Chemistry
is the property of Taylor & Francis Ltd and its content may not be copied or emailed to
multiple sites or posted to a listserv without the copyright holder's express written permission.
However, users may print, download, or email articles for individual use.