Spectral and thermal studies of divalent transition metal with indole-2-carboxylic acid and 4-substituted hydrazinethiocarbamide

Article abstract of DOI:10.1016/j.saa.2005.07.081

Ternary complexes of Co(II), Ni(II) and Cu(II) with indole-2-carboxylic acid (A) and 4-substituted hydrazinethiocarbamide (L) [4-phenylhydrazinethiocarbamide (L¹), 4-benzylhydrazinethiocarbamide (L²) and 4-(2-propenyl)hydrazinethiocarb-amide (L³) were prepared. The structure of the complexes was characterized by microchemical analysis, molar conductance, electronic, IR, ¹H-NMR, mass spectra as well as thermogravimetric studies. An octahedral structure is suggested for Co(II), Ni(II) and Cu(II) ternary complexes.

Full text of DOI:10.1016/j.saa.2005.07.081

Spectrochimica Acta Part A 65 (2006) 5–10
Spectral and thermal studies of divalent transition metal with
indole-2-carboxylic acid and 4-substituted hydrazinethiocarbamide
Iman T. Ahmed
Chemistry Department, Faculty of Science, El-Minia University, El-Minia 61519, Egypt
Received 31 January 2005; accepted 29 July 2005
Abstract
Ternary complexes of Co(II), Ni(II) and Cu(II) with indole-2-carboxylic acid (A) and 4-substituted hydrazinethiocarbamide (L) [4-
phenylhydrazinethiocarbamide (L1), 4-benzylhydrazinethiocarbamide (L2) and 4-(2-propenyl)hydrazinethiocarb-amide (L3) were prepared. The
1
structure of the complexes was characterized by microchemical analysis, molar conductance, electronic, IR, H-NMR, mass spectra as well as
thermogravimetric studies. An octahedral structure is suggested for Co(II), Ni(II) and Cu(II) ternary complexes.
© 2005 Published by Elsevier B.V.
Keywords: Indole-2-carboxylic acid; Hydrazinethiocarbamide; Ternary metal complexes; Electronic spectra (IR, 1H-NMR) and mass spectroscopy
1. Introduction
hydroxyquinoline [23,24], creatinine [25], mercaptobenzazoles
[26]andthiosemicarbazideaswellasdithiocarbazatederivatives
[21]. The present investigation deals with synthesis and spectral
characterization of ternary metal complexes M(II)-4-substituted
hydrazinethiocarbamides-indole-2-caboxylic acid. It is hoped
that such study may give further insight into the type of coordi-
nation of these ligands with Co(II), Ni(II) and Cu(II).
Thiourea and hydrazinethiocarbamide derivatives have long
history as ligands in coordination to a metal via either sulphur
or nitrogen [1]. Hydrazinethiocarbamide is an interesting lig-
and not only for the structural chemistry of its multifunction
coordination modes but also for the formation of complexes
with antifungal, antimicrobial and antitumor properties [2–4].
Although metal complexes of hydrazinethiocarbamide deriva-
tives have been reported either in enol or keto form [5–13], there
are no reports available in the literature on synthesis or spectral
studies of their mixed ligand complexes with the polyfunctional
donating indole-2-carboxylic acid. Singh and Parkash [14,15]
have been isolated and characterized the complexes of Fe(III),
Cu(II), Hg(II), Pb(II) and Ag(I) with indole-2-carboxylic acid.
The analytical studies for complexes isolated showed the stoi-
chiometry 1:3, 1:2, 1:2, 1:2 and 1:1 (metal:ligand) for the Fe(III),
Cu(II), Hg(II), Pb(II) and Ag(I) complexes, respectively [14,15].
It seems that the reaction of transition metals with substituted
hydrazinethiocarbamides and indole-2-carboxylic acid is rather
complicated and reaction products depend on the type of ligand
used (Fig. 1). Therefore, as a part of our program of the synthe-
sis of several ternary complexes, we have recently reported the
ternary complexes of divalent transition metal ions with the bio-
logically active N-(2-acetamido)iminodiacetic acid [16–22], 8-
2. Experimental
2.1. Materials and reagents
The metal salts cobalt(II) chloride, nickel(II) chloride
and copper(II) chloride as well as indole-2-carboxylic acid
were analytical grade (Aldrich) products of a high purity.
4-Substituted hydrazinethiocarbamides were prepared accord-
ing to literature as were 4-phenyhydrazinethiocarbamide (L1)
[27,28], 4-benzylhydrazinethio-carbamide (L2) [28,29] and 4-
(2-propenyl)hydrazinthiocarbamide (L3) [29,30], the purity of
these compounds was verified by thin layer chromatography
(TLC). Spectroscopic grade DMSO purchased from Aldrich was
used for electronic spectral measurements.
2.2. Synthesis of ternary metal complexes
In a round bottomed flask an ethanolic solution (10 ml)
containing 5 mmol (0.806 g) of ligand A was added to an
E-mail address: h imanth124@yahoo.com.
1386-1425/$ – see front matter © 2005 Published by Elsevier B.V.
doi:10.1016/j.saa.2005.07.081

6
I.T. Ahmed / Spectrochimica Acta Part A 65 (2006) 5–10
Fig. 1. The structure of the ligands.
ethanolic solution (10 ml) containing 5 mmol of each of the
following metal salts: CoCl2·6H2O (1.190 g); NiCl2·6H2O
(1.189 g); or CuCl2·2H2O (0.852 g). To this mixture were
added slowly with stirring an ethanolic solution (10 ml) con-
taining 5 mmol of the following 4-substituted hydrazine-thio-
carbamides: 4-phenylhydrazinethiocarbamide (L1) (0.836 g),
4-benzylhydrazine-thiocarbamide (L2) (0.906 g) or 4-(2-
propenyl)hydrazinethiocarbamide (L3) (0.656 g). The ternary
mixture was refluxed for 5 h and then evaporated to half of
its volume and left to cool. The ternary complexes precipitated
out, were filtered and washed thoroughly with distilled H2O and
EtOH and dried in vacuo over P4O10. The microanalytical data
of the isolated chelates along with their decomposition temper-
ature are listed in Table 1.
2.3. Physical measurements
Melting points have been determined in open glass capillaries
on Gallen Kamp melting point apparatus and are uncorrected.
The C, H, N, S and Cl contents of the prepared ternary complexes
were determined by the Microanalytical Unit at Cairo Univer-
sity. Molar conductance of DMSO solutions of the synthesized
ternary complexes were measured at 25 ◦C using a model 31 YSI
conductivity bridge with conductivity cell constant = 0.10 M.
Thermogravimetric (TG) analysis were performed automati-
cally using a Dupont 9000 thermal analyzer at a heating rate
of 10 ◦C min−1 in a dynamic air atmosphere. Infrared spec-
tra were recorded in the 4000–200 cm−1 range on FT-IR 1650
(Perkin Elmer) spectrophotometer using KBr disk technique. A
1
Bruker WM 300 instrument has been used to determine H-
NMR (300.1 MHz). Mass spectra have been obtained with a
Varian MAT 311 doubly focusing instrument. Electronic spec-
tra of freshly prepared solutions of the complexes in DMSO
were monitored at 25 ◦C in 300–1000 nm range by an Uni-
cam Scanning UV–vis spectrophotometer model UVA 1000E
with an accuracy of 1 nm using matched silica cells of 1.0 cm
path length. The spectrophotometer and its accessories were
controlled by software under Windows to provide advanced
operational facilities.
3. Results and discussion
3.1. Characterization of the ternary metal complexes
The analytical data listed in Table 1 clearly suggested two
formula [M(A)(L)Cl·H2O]H2O for the Co(II) and Ni(II) ternary
metal complexes and H[M(A)(L)Cl2] for Cu(II) ternary metal
complexes.

I.T. Ahmed / Spectrochimica Acta Part A 65 (2006) 5–10
7
The prepared ternary complexes were found to be insol-
uble in water as well as in most common organic solvents.
However, they are slightly soluble in DMF and DMSO. The
measured molar conductance values (Λmax) of 10−3 mol dm−3
DMSO solutions of Co(II) and Ni(II) ternary complexes are
in the range of 12–19 ꢀ−1 cm−1 mol−1 L indicating the non-
electrolytic nature of these complexes [31]. On the other hand,
the molar conductance values of the ternary Cu(II)-complexes
found to be in the range of 92–112 ꢀ–1 cm−1 mol−1 L is consis-
tent with a 1:1 electrolyte [31].
3.1.1. TG analysis
Thermogravimetric (TG) analysis of the various prepared
ternary complexes have been carried out to obtain diagnostic
structural evidence of the suggested molecular formula. Gen-
erally, the TG curves for Co(II) and Ni(II) ternary complexes
exhibit one weight loss step over the temperature range of
75–120 ◦C. This weight loss is in good agreement with the
removal of one water molecule. In addition, the prepared Co(II)
and Ni(II) ternary complexes display one weight loss step over
the range of 180–200 ◦C, which is consistent with the removal
of another water molecule Therefore, one can conclude that
the synthesized Co(II) and Ni(II) ternary complexes contain
one water molecule of hydration and one coordinated water
molecule. On the other hand, the TG curves of the synthe-
sized Cu(II)-ternary complexes do not display noticeable weight
losses up to the relatively high temperature (≈200 ◦C), where
one weight loss step is occurred. This behaviour reveals that such
complexes do not contain water either in the form of hydration or
coordination. This is in accordance with the results of the micro-
chemical analysis (Table 1) as well as with the infrared spectra
(Table 2). However, at high temperature (>300 ◦C) a weight loss
Fig. 2. TG and DTG curves of the [Co(A)(L1)Cl(H2O)]H2O ternary complex.
step is observed containing a rapid decomposition of the ternary
complexes.
In order to have an idea about the thermal decomposition
course of the complex under investigation, the thermogram
extended to a higher temperature measurement. Though the
TG with the corresponding DTG of Co(II)-indole-2-carboxylic
acid-phenylhydrazinethiocarbamide are shown in Fig. 2. The
TG curve indicates that the complex under investigation shows
a remarkable stability up to ≈200 ◦C. Above this temperature
the complex starts to decompose and the thermogram exhibits
three main distinct steps which are maximized at 274, 478 and
above 550 ◦C on DTG curve. The first main decomposition step
indicates that the complex suffers 25% weight loss through step
2 occurring at 200–300 ◦C, which corresponds to the loss of a
molecule of indole (calcd. 25.21%). The second step is accom-
Table 2
Assignment of the most important IR frequencies (cm−1) of the various synthesized ternary complexes
[M(II)-L1-A
Co(II)
M(II)-L2-A
Co(II)
M(II)-L3-A
Co(II)
Assignment of IR bands
Ni(II)
Cu(II)
Ni(II)
Cu(II)
Ni(II)
Cu(II)
3520
3360
3525
3355
–
3510
3370
3520
3330
–
3360
3500
3360
3495
3370
–
3350
␯(OH) of hydrated and coordinated H2O
␯(NH) asymm. stretching of
3330
indole-2-carboxylic acid
3280–3200 3265–3210 3280–3190 3260–3200 3245–3170 3270–3190 3280–3140 3275–3160 3280–3150 ␯(NH and NH2) of
hydrazinethiocarbamides
1595
1610
1600
1605
1590
1610
1605
1615
1610
␯(COO−) asymm. of indole-2-carboxylic
acid
1550
1510
1410
1545
1520
1400
1550
1500
1390
1555
1500
1400
1545
1505
1390
1550
1510
1400
1545
1515
1400
1560
1510
1410
1550
1510
1400
␯(C C) of indole and aryl rings
␯(C N) of hydrazinethiocarbamides
␯(COO−) symm. stretching of
indole-2-carboxylic acid
1330
1000
870
770
475
1325
1000
890
765
480
1330
1000
–
770
470
370
1335
995
875
750
490
375
1330
1010
865
770
470
1340
1000
–
765
475
355
1325
1010
890
755
480
1335
1000
885
750
485
1330
1000
–
755
470
350
␯(C S) of hydrazinethiocarbamides
␯(N N) hydrazinethiocarbamides
␯ of rocking mode of coordinated H2O
␯(C S) of hydrazinethiocarbamides
␯(M-N) stretching of indole-NH-M
␯(M-S) stretching of
370
355
360
350
355
hydrazinethiocarbamides – M
␯(M-Cl)
235
212
218
220
230
220
232
235
230

8
I.T. Ahmed / Spectrochimica Acta Part A 65 (2006) 5–10
3370–3330 cm−1. The lowering of these frequencies may be
attributed to theformationof nitrogen–metalbond. Furthermore,
the sharp band appearing in the range of 1410–1390 cm−1 in the
spectra of all synthesized ternary complexes could be attributed
to symm. COO− of indole-2-carboxylic acid. The IR spectra of
4-substituted hydrazinethio-carbamides show strong bands in
the region 3460–3100 cm−1, which may be assigned to NH and
NH2 groups. These bands are shifted towards lower wavenum-
ber in all the complexes (Table 2), suggesting that the NH2 group
is taking part in complex formation [34].
panied by weight loss 22% corresponds to the decomposition
of Ph N C (calcd. 22.39%) takes place within the temperature
range of 300–450 ◦C (step 3). The third weight loss step, which is
maximized at 478 ◦C, is accompanied by 20% weight loss. This
value is very close to that calculated (20.22%) for the expulsion
of aniline (step 4). Finally upon examining the TG curve, one can
observe that we have a plateau above 550 ◦C. This corresponds
to the formation of the metal oxide (CoO) with the deposition
of three moles of carbon giving 24% (calcd. 24.36%).
3.1.2. Electronic spectra
The stretching modes of C S of free substituted
hydrazinethiocarbamides observed at 1360 cm−1 [35] is shifted
to lower frequency at 1340–1325 cm−1 range in the IR spectra of
the complexes, revealing the participation of thione group coor-
dinated with the metal ion. The bands at 1485 cm−1 assigned to
The electronic absorption spectroscopic data of 10−3 mol
dm−3 DMSO solutions of the various prepared ternary
complexes are listed in Table 3. The electronic spectra
of pink or reddish-coloured Co(II) complexes demonstrate
a well-defined absorption band around 512 nm (ε = 23.24–
32.54 cm−1 mol−1 L) (Table 3). It was previously reported
that the electronic spectra of six-coordinated Co(II) complexes
exhibit a broad absorption band near 500 nm (ε = 5–40 cm−1
␯(C N) are shifted to higher wavenumbers (1520–1500 cm−1
)
which is additional evidence for the contribution of the thione
group. The positive shift in the ␯(N N) mode in the spectra
of the complexes, indicates the involvement of only one of the
hydrazine nitrogens [36] in coordination.
mol−1 L), which is assigned to the 4T1g → T1g(p) transition of
4
New bands around 490–470, 375–350 and 235–212 cm−1
seemed to be the spectra of complexes which are assigned
to ␯(M-N) [37], ␯(M-S) [38,39] and ␯(M-Cl) [37,40],
respectively.
an octahedral structure in admixture with spin-forbidden transi-
tion to doublet states [32]. Accordingly, an octahedral structure
could be suggested for these complexes. The spectra of the
Ni(II) complexes showed a main broad absorption band in the
range of 590–610 nm (ε = 8.60–5.30 cm−1 mol−1 L), depend-
ing on the nature of the hydrazinecarbothioamide derivative
ligands. An additional weak absorption band is also observed
around 890 nm (ε = 1.25–1.45 cm−1 mlo−1 L). Six-coordinated
and octahedral Ni(II) complexes exhibit an absorption spec-
trum involving three allowed transitions in the ranges 1428–770,
909–500 and 526–370 nm of comparatively low intensity [32].
Accordingly, an octahedral structure is suggested for the Ni(II)
complexes, where the observed band in the range 590–610 nm
3.1.4. 1H-NMR spectrum of [Co(A)(L1)Cl(H2O)]H2O
The 1H-NMR spectrum of [Co(A)(L1)Cl(H2O)]H2O ternary
complex in DMSO-d6 in addition to aromatic and indole-
CH protons shows four broad signals at 6.40, 8.82, 9.42
and 9.87 ppm in 2:1:1:1 ratio, which are down field from TMS
and disappear upon adding D2O. These signals are attributed to
the protons of hydrazinethiocarbamide-NH2, hydrazine-
thiocarbamide-2NH, indole-NH and hydrazinethiocarbamide-
1NH, respectively. The presence of the previous signals in the
1H-NMR spectrum of [Co(A)(L1)Cl(H2O)]H2O ternary com-
plex indicates that substituted hydrazinecarbothioamides act as
a bidentate ligands via a contribution of NH2 as well as C S
groups in coordination. On the other hand, the disappearance
of carboxylic proton in indole ring indicates the involvement of
carboxylic group in complex formation.
3
3
3
is assigned to the T1g(F) ← A2g(F) → T1g(F) transitions. The
weak absorption around 890 nm is attributed to the 3A2g → Eg
2
transition [19].
The spectra of the Cu(II) complexes showed a broad band
with λmax at 700–630 nm followed by a broad band into the
near infrared region. It was reported previously that the major-
ity of six-coordinate Cu(II)-complexes have a tetragonal dis-
torted structure giving rise to an absorption band near 630 nm.
Therefore a tetragonal distorted structure is suggested for these
complexes. Accordingly, the observed band is assigned to a
3.1.5. Mass spectrum of [Co(A)(L1)Cl(H2O)]H2O
For the complex [Co (A) (L1) Cl (H2O)]H2O the gross for-
mulaC16H19 CoClN4SO2, wasconfirmedbythemassspectrom-
etry. Besides the molecular ion at m/z = 458/460, the characteris-
tic fragment ion pattern of monohalo compounds was observed
[41].
The mass spectrum shows fragments at 361 (8), 268 (17),
150 (11), 117 (100), 103 (21) and 93 (46). The fragments at m/z
135 (representing Ph N C S residue), 117 (representing indole
residue), 103 (representing Ph N C residue) and 93 (represent-
ing aniline residue) resulting from the cleavage of Co N and
Co S bonds.
2
2
2
2
2
2
combination of B1g → A1g, B1g → B2g and B1g → E1g
transitions.
3.1.3. Infrared spectra
Relevant IR bands which provide conclusive structural evi-
dence for the structure of the ternary complexes prepared are
listed in Table 2.
Generally, the IR spectra of ligands were compared with
the spectra of the metal complexes. The IR spectra of the
ternary complexes display the broad bands in the range of 3525–
3495 cm−1 which could be attributed to the OH-stretching
vibration of hydrated and coordinated water. The stretching-
NH vibration is observed at 3395 cm−1 in indole-2-carboxylic
acid [33] shifts to the lower frequencies in the region
The mass spectral fragmentation of the ternary metal com-
plex [Co(A)(L1)Cl(H2O)]H2O, however, is in agreement with
structure in Fig. 3.

I.T. Ahmed / Spectrochimica Acta Part A 65 (2006) 5–10
9
References
[1] A.D. Burrows, M.D. Coleman, M.F. Mahon, Polyhedron 18 (1999)
2665.
[2] X. Shen, X.F. Shi, B.S. Kang, Y. Liu, Y.X. Tong, H.L. Jiang, K.X. Chen,
Polyhedron 17 (1998) 4049.
[3] M.J.M. Cambell, Coord. Chem. Rev. 5 (1975) 279.
[4] B.C. Benns, B.A. Gingras, C.H. Bayley, Appl. Microbiol. 2 (1961)
353.
[5] D. Chattopadhyay, S.K. Majumdor, P. Lowe, C.H. Schwalbe, J. Chem.
Soc. Dalton Trans. (1991) I2121.
[6] M.B. Cingi, F. Bigoli, M. Lanfranchi, M.A. Pellinghelli, A. Vera, E.
Buluggiu, J. Chem. Soc. Dalton Trans. (1992) 3145.
[7] C.Y. Duan, Z.H. Liu, X.Z. You, F. Xue, T.C.W. Mak, J. Chem. Soc.
Chem. Commun. (1997) 381.
Fig. 3. Representative examples of the structures for the synthesized ternary
metal complexes (R = phenyl, benzyl and allyl).
[8] F. Nicolo, H. ElGhaziri, G. Chapuis, Acta Crystallogr. C 44 (1988)
975.
[9] O.P. Mel’nyk, Ya. E. Filinchuk, D. Schollmeyer, M.G. Mys’kiv, Z.
Anorg. Allg. Chem. 627 (2001) 287.
In conclusion, the following remarks may be of some
interest:
[10] A.D. Burrows, C.W. Chan, M.M. Chowdhry, J.E. McGrad, D.M.P. Min-
gos, Chem. Soc. Rev. 24 (1995) 329.
[11] M.T. Allen, A.D. Burrows, M.F. Mahon, J. Chem. Soc. Dalton Trans.
(1999) 215.
[12] A.D. Burrows, S. Menzer, D.M.P. Mingos, A.J.P. White, D.J. Williams,
J. Chem. Soc. Dalton Trans. (1997) 4237.
(i) All complexes are stable on heating up to 200 ◦C, the
first decomposition step for Co(II) and Ni(II)-ternary com-
plexes may be attributed to the removal of two water
molecules.
[13] K.A. Hanshalter, J. Lau, J.D. Roberts, J. Am. Chem. Soc. 118 (1996)
8891.
[14] A.K. Singh, D. Prakash, J. Inorg. Nucl. Chem. 40 (1978) 579.
[15] A.K. Singh, D. Parkash, S.K. Srivastava, J. Indian Chem. Soc. LV (1978)
861.
[16] M.M.A. Hamed, M.B. Saleh, I.T. Ahmed, M.R. Mahmoud, J. Chem.
Eng. Data 39 (1994) 565.
[17] M.R. Mahmoud, M.M.A. Hamed, S.A. Ibrahim, I.T. Ahmed, Synth.
React. Inorg. Metal Org. Chem. 24 (1994) 1661.
[18] S.A. Ibrahim, M.R. Mahmoud, M.B. Saleh, I.T. Ahmed, Transit. Metal
Chem. 19 (1994) 494.
[19] M.R. Mahmoud, S.A. Ibrahim, A.M.A. Hassan, I.T. Ahmed, Transit.
Metal Chem. 21 (1996) 1.
[20] M.R. Mahmoud, M.I. Abdel-Hamid, N.M. Ismail, I.T. Ahmed, Polish.
J. Chem. 70 (1996) 544.
[21] I.T. Ahmed, Synth. React. Inorg. Metal Org. Chem. 26 (1996)
1455.
[22] I.T. Ahmed, A.A.A. Boraei, S.A. Ibrahim, Synth. React. Inorg. Metal
Org. Chem. 27 (1997) 169.
(ii) The second to fourth steps attributed to removal of indole
and the residue of hydrazinethiocarbamide.
(iii) The hydrazinethiocarbamide derivatives act as a neutral
bidentate ligand, coordinating via NH2 and the (C S)
groups as shown in Fig. 3 This mode of complexation
1
can be suggested on the basis of IR and H-NMR which
shows broad signals due to the protons of hydrazinethiocar-
bamide – NH2, 2NH and 4NH. The IR spectra of the ternary
complexes revealing the participation of thione group coor-
dinated with the metal ions.
Indole-2-carboxylic acid behave as a mononegative
bidentate ligand via indole-NH and COOH groups (in
1
accordance with the results of H-NMR and IR spectra)
with the displacement of hydrogen atom from the lat-
ter group, forming two five membered rings as shown in
Fig. 3.
[23] I.T. Ahmed, A.A.A. Boraei, O.M. El-Roudi, J. Chem. Eng. Data 43
(1998) 459.
[24] A.A.A. Boraei, I.T. Ahmed, Synth. React. Inorg. Metal Org. Chem. 32
(2002) 981.
(iv) The analytical data of the ternary complexes under inves-
tigation would also match for other alternative structures
and could be ruled out on the basis of the above thermal
and spectroscopic data.
[25] I.T. Ahmed, Synth. React. Inorg. Metal Org. Chem. 34 (2004) 523.
[26] I.T. Ahmed, Synth. React. Inorg. Metal Org. Chem. 33 (2003) 547.
[27] B. Stanovnik, M. Tisler, J. Org. Chem. 25 (1960) 2236.
[28] U. Eberhardt, J. Rabe, I. Anger, J. Schmidt, H. Grunet, East German
Patent 83 (1971) 559, Appl. WPC o7c/149 (1970) 657, Chem. Abstr.
87 (1973) 996674g.
[29] M.G. Paranje, P.H. Deshpande, Indian J. Chem. 7 (1969) 186.
[30] I.V. Nikolaeva, A.A. Tsurkan, I.B. Levshin, K.A. Vyunov, A.I. Ginak,
Zh. Prakt. Khim. (Leningrad) 58 (1985) 1189, Chem. Abstr. 103 (1985)
177952h.
[31] K. Burger, Coordination Chemistry, Experimental Methods, CRC Press,
Cleveland, 1973, pp. 219–226.
[32] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam,
1968.
[33] A.K. Singh, D. Prakash, J. Inorg. Chem. 40 (1978) 579.
[34] D.R. Williams, Chem. Rev. 72 (1972) 203.
[35] R. Smicius, V. Jakubkiene, M.M. Burbuliene, A. Mikalaingte, P.
Vainilavicies, J. Chem. Res. S (2002) 170.
[36] A. Braibanti, F. Dallvalle, M.A. Pellinghell, E. Laporati, Inorg. Chem.
7 (1968) 1430.
(v) Further, the molecular mechanics PM3 program [42]
for the structure of H[Cu(A)(L1)Cl2] complex (Fig. 3),
as examples suggests that the coordination by both the
thiocarbonyl and the NH2 groups towards Cu metal is
more stable (steric energy = 125 kcal/mole) with respect
to the other structure which involved coordination by the
R NH and NH2 groups (steric energy = 248 kcal/mole)
towards the same metal. Moreover, the coordination via
the C S group is more favorable compared with the
RNH-group.
(vi) The metal complexes insoluble in ethanol, methanol, ace-
tonitrile and various solvents, but soluble in DMSO. All
attempts to prepare single crystals of the compounds failed.
Thus, no definite structure can be described, but the analyt-
ical and spectroscopic data enable us to predict the possible
structures as shown in Fig. 3.

10
I.T. Ahmed / Spectrochimica Acta Part A 65 (2006) 5–10
[37] J. Ehuheey, Inorganic Chemistry, Principles of Structure and Reactivity,
1st Edn, Harper International, 1983.
[38] W. Brzyska, Z. Rzacznska, A. Kula, Monatsh. Chem. 120 (1989)
211.
[39] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordina-
tion Chemistry, Wiley, New York, 1978.
[41] R.M. Silverstein, Spectroscopic Identification of Organic Compounds,
John Wiley and Sons Inc., New York, London, Sydney, 1974.
[42] N.L. Allinger, MM2 (91) force field program, obtained from Quan-
tumChemistry Program, Indiana University; Molecular Mechanics PM3
program (ACD/3D), Advanced Chemical Development Inc., Toronto,
Canada (1988).
[40] M. Gabryszewski, Spectrosc. Lett. 34 (2001) 57.