950
S.J. Azhari et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 150 (2015) 949–958
[3], antitumor [4,5], antimalarial [6] and antiviral [7]. In continua-
tion of our earlier work [8–14] and others [15–19] and due to the
importance of these compounds, we extend this work to include
thiosemicarbazide derived from salicylic acid hydrazide. Also,
the ternary metal complexes with 2,20-dipyridyl were synthesized
and characterized. The biological activity of L1 and two metal
complexes were tested against DNA. Moreover, comparative
studies between our previous works of 4-allyl- and
4-phenyl-4-(2-hydroxybenzoyl) thiosemicarbazides [20,21] have
been studied. Finally, we focused our attention to study the role
and behavior of ethyl, phenyl and/or allyl attached in the
4-position of the thiosemicarbazide moiety on the geometry of
complex formation as well as on the reactivity toward DNA.
pH of the solution was raised to 5 in case of Co2+ and Zn2+ com-
plexes using KOH solution. The Cu2+ complex was obtained at
pH = 2 and without raising the pH of the solution. All the binary
and ternary complexes were filtered off, washed several times with
hot EtOH and diethyl ether, respectively. The isolated solid com-
plexes were dried in oven at 120 °C for 1.5 h.
2.5. Genotoxicity activity
The methodology for studding genotoxicity activity was
described earlier [20,21].
3. Computational details
2. Experimental
All computational calculations using DMOL3 program are
reported in our previous work [20,21].
2.1. Instrumentation and materials
4. Results and discussion
All the chemicals were purchased from Aldrich and Fluka and
used without further purification. All the methods and instrumen-
tations are described in earlier works [22,23].
All the isolated metal complexes are colored, insoluble in most
common organic solvents but partially soluble in DMSO and DMF,
except the Zn2+ complexes, which are white in color. The value of
2.2. Synthesis of synthesis of the ligand (L1)
K+m for the ternary Zn2+ complex (5.0
X
ꢃ1 cm2 molꢃ1) at 25 °C
suggests that complex is non-electrolytic in nature. All the metal
complexes have high melting points (>300 °C), except for the Cu2+
(binary) complex, which is 214 °C. Elemental analyses and some
physical properties of the isolated solid complexes are listed in
Table 1.
4-Ethyl-1-(2-hydroxybenzoyl) thiosemicarbazide (L1) was syn-
thesized similar to these described earlier in our previous work
[20,21] but using ethyl isothiocyanate. L1 was checked by its melt-
ing point (217–218 °C) and TLC.
2.3. Syntheses of binary metal complexes
4.1. IR spectra
A solution of L1 (0.0 l mol; 2.5 g) in EtOH was added to the metal
salt solutions (0.01 mol) of CoCl2ꢁ6H2O (2.4 g), CuCl2ꢁ2H2O (1.7 g)
and Zn(Ac)2ꢁ2H2O (2.2 g) in EtOH (50 mL). The reaction mixtures
were refluxed on a hot plate for ꢂ3 h. The pH of the solutions were
found in the range 1–2 for the Cu2+ and Co2+ complexes while at 5
in case of the Zn2+ complex.
The IR bands of 4-ethyl-1-(2-hydroxybenzoyl) thiosemicar-
bazide and its metal complexes are depicted in Table 2. The IR
spectrum of L1 in KBr shows a strong band at 1660 cmꢃ1 assignable
to the
exists in the keto form. On the other hand, three bands are
observed at 3126, 3186 and 3254 cmꢃ1 assigned to the (1NH),
(2NH) and (4NH) vibrations [26], respectively. The three bands
at 3388, 1244 and 700 cmꢃ1 are attributed to
(OH) [25,26] and
m
(C@O) vibration [24,25]. This suggests that L1 is mainly
m
m
m
2.4. Syntheses of ternary metal complexes
m
m
(C@S) [27] vibrations, respectively. Moreover, no bands are
A solution of 2,20-dipyridyl (L2, 0.003 mol; 0.45 g) in EtOH
observed in the 2500–2600 cmꢃ1 region attributed to the SH
group [28] indicating that the free ligand in the solid state is
mainly existed in the thione/keto form (Fig. 1). The previous
postulation is confirmed by molecular modeling of L1 as shown
in (Figs. 1a and 1b).
(25 mL) was added to
a
solution of CoCl2ꢁ6H2O (0.003 mol;
0.72 g), CuCl2ꢁ2H2O (0.003 mol; 0.51 g) and ZnCl2 (0.003 mol;
0.42 g) in EtOH (25 mL). The binary solid complexes derived from
2,20-dipyridyl were filtered off and washed with hot EtOH and
diethyl ether, respectively. The ternary complexes were synthe-
sized by dissolving the isolated solid complexes derived from
2,20-dipyridyl in redistilled water (0.003 mol; 0.8 g) in case of the
Cu2+ complex, (0.002 mol; 0.6 g) for the Co2+ complex and
(0.004 mol; 1.2 g) in case of Zn2+ complex. L1 was dissolved in
absolute EtOH (25 mL) and then added to the above complex solu-
tions. The reaction mixtures were heated on a hot plate for 4 h. The
The IR spectra of metal complexes (binary complexes) show
that L1 acts as a mononegative bidentate in the thiol form in the
case of binary Cu2+ and Co2+ chlorides complexes, while the ligand
acts as a mononegative tetradentate in the enol form in case of the
binary Zn2+ acetate complex.
Firstly, in case of Cu2+ and Co2+ chloride complexes (Figs. 2 and
3), the results show that L1 coordinates to the metal ions through
Table 1
Analytical and some physical data of L1 and its metal complexes.
No.
Compound (empirical formula)
(F.Wt)
Color
M.p. (°C)
% Found (Calcd.)
leff BM
K+m (DMSO)
C
H
M
Cl
1
2
3
4
5
6
7
(L1); C10H13N3O2S
239.3
586.2
535.5
969.0
1022.0
506.5
581.3
White
Brown
Black
White
Olive green
Deep brown
White
217–218
214
50.6 (50 .2)
45.7 (45.1)
45.4 (44.9)
38.1 (37.2)
46.6 (47)
5.3 (5.5)
5.3 (5.2)
4.6 (4.6)
4.4 (4.2)
4.3 (4.9)
4.5 (5)
–
–
–
–
–
–
–
–
–
–
[Cu(L1-H)2]ꢁEtOH
10.6 (10.8)
11.4 (11)
21.1 (20.2)
12.2 (12.4)
11.4 (11.6)
22.4 (22.6)
2.1
3.8
–
1.7
4.2
–
10.8
15.2
–
–
14.5
5.00
[Co(L1-H)2]
>300
>300
>300
>300
>300
[Zn3(L1-H)(LH)(Ac)5]
[Cu2(L2)2(L1-2H)2(H2O)2]ꢁ4H2O
[Co(L2)(L1-2H)]ꢁ3H2O
[Zn2(L2)(OH)(L1-3H)(H2O)]ꢁ1/2EtOH
46.9 (47.4)
42.9 (43.4)
4.2 (4.2)
*(ohmꢃ1 cm2 molꢃ1), L2 = 2,20-dipyridyl.