Structural studies on acetophenone- and benzophenone-derived thiosemicarbazones and their zinc(II) complexes

Article abstract of DOI:10.1016/j.molstruc.2011.11.035

In the present work N(3)-meta-chlorophenyl-(HAc3mCl, 1) and N(3)-meta-fluorphenyl-(HAc3mF, 2) acetophenone thiosemicarbazone, and N(3)-meta-chlorophenyl-(HBz3mCl, 3) and N(3)-meta-fluorphenyl-(HBz3mF, 4) benzophenone thiosemicarbazone were obtained, as we

Full text of DOI:10.1016/j.molstruc.2011.11.035

Journal of Molecular Structure 1008 (2012) 102–107
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structural studies on acetophenone- and benzophenone-derived
thiosemicarbazones and their zinc(II) complexes
Karina S.O. Ferraz a, Nayane F. Silva a, Jeferson G. Da Silva a, Nivaldo L. Speziali b, Isolda C. Mendes c,
Heloisa Beraldo a,
⇑
a Departamento de Química, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
b Departamento de Física, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
c Escola de Belas Artes, Departamento de Artes Plásticas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
In the present work N(3)-meta-chlorophenyl- (HAc3mCl, 1) and N(3)-meta-fluorphenyl- (HAc3mF, 2) ace-
tophenone thiosemicarbazone, and N(3)-meta-chlorophenyl- (HBz3mCl, 3) and N(3)-meta-fluorphenyl-
(HBz3mF, 4) benzophenone thiosemicarbazone were obtained, as well as their zinc(II) complexes
[Zn(Ac3mCl)2] (5), [Zn(Ac3mF)2] (6), [Zn(Bz3mCl)2] (7) and [Zn(Bz3mF)2] (8). Upon re-crystallization in
DMSO:acetone conversion of 8 into [Zn(Bz3mF)2]ꢀ(DMSO) (8a) occurred. The crystal structures of 2, 5
and 8a were determined.
Received 19 September 2011
Received in revised form 21 November 2011
Accepted 21 November 2011
Available online 28 November 2011
Keywords:
Ó 2011 Elsevier B.V. All rights reserved.
Thiosemicarbazones
Zinc(II) complexes
Crystal structures
1. Introduction
thiosemicarbazones. In fact zinc(II) complexes with this class of li-
gands proved to exhibit cytotoxic, antiproliferative [3,8] and anti-
Thiosemicarbazones are an important class of compounds with
innumerous biological applications as antitumor, antiviral and
microbial activities [9], among others.
In the present work N(3)-meta-chlorophenyl acetophenone-
(HAc3mCl) and N(3)-meta-fluorphenyl acetophenone-(HAc3mF)
thiosemicarbazones and N(3)-meta-chlorophenyl benzophenone-
(HBz3mCl) and N(3)-meta-fluorphenyl benzophenone-(HBz3mF)
thiosemicarbazones (see Fig. 1) were obtained as well as their zin-
c(II) complexes. The spectral and structural properties of the stud-
ied compounds were investigated.
antimicrobial agents [1].
a(N)-heterocyclic thiosemicarbazones
were extensively investigated for their antitumor and cytotoxic
activities, which were related to their ability to inhibit ribonucleo-
side diphosphate reductase (RDR), a key enzyme involved in DNA
synthesis [2].
Thiosemicarbazones act as ligands in coordination chemistry in
different ways [3]. They can bind metal ions as bidentate NS- or tri-
dentate NNS-donor ligands forming five-membered chelate rings.
Transition metal complexes of thiosemicarbazones are of consider-
able interest in chemistry because of their bioinorganic relevance
[4,5].
2. Experimental section
2.1. Materials and measurements
Zinc is the second most prominent trace metal in the human
body after iron. Zinc(II) ions are essential for all forms of life. In hu-
mans, they have catalytic and structural functions in an estimated
3000 zinc proteins [6]. Zinc is cytoprotective and suppresses apop-
totic pathways. Zinc plays a role in brain, where it has a specific
function as a neuromodulator in addition to its other typical cellu-
lar functions [7].
Considering the wide pharmacological versatility of thiosemi-
carbazones and the important role of zinc(II) in biological pro-
cesses, it is of interest to prepare new zinc(II) complexes with
Chemicals: acetophenone (Aldrich), benzophenone (Fluka),
hydrazine hydrate (Aldrich), sulfuric acid (Synth), triethylamine
(Merck), zinc(II) chloride (Vetec). Solvents: absolute ethanol
(Synth), methanol (Synth), acetone (Synth), dimethylsulfoxide
(Synth), DMSO-d6 (CIL) and diethylether (Synth).
Partial elemental analyses were performed on a Perkin Elmer CHN
2400 analyzer. Infrared spectra were recorded on a Perkin–Elmer FT-IR
Spectrum GX spectrometer using CsI pellets; an YSI model 31 conduc-
tivity bridge was employed for molar conductivity measurements.
NMR spectra were obtained at room temperature with a Brucker
DRX-200 Avance (200 MHz) spectrometer using deuterated dimethyl
sulfoxide (DMSO-d6) as the solvent and tetramethylsilane (TMS) as
internal reference.
⇑
Corresponding author. Tel.: +55 31 34095740; fax: +55 31 34095700.
E-mail address: hberaldo@ufmg.br (H. Beraldo).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.11.035

K.S.O. Ferraz et al. / Journal of Molecular Structure 1008 (2012) 102–107
103
2.2.1.2.
HAc3mF (2). White solid. Yield: 99%. IR (KBr, cmꢁ1):
3299 s, (N2AH) 3264 s, (C@N) 1520 s, (C@S) 787 w. UV–Vis
N(3)-meta-fluorphenyl-acetophenone-thiosemicarbazone,
m
(N3AH)
m
m
m
(DMF, cmꢁ1): 32,573. The main signals in 1H NMR (DMSO-d6): d
(ppm) = 8.03–7.98 (1H, d, H(2), H(6)); 7.44–7.33 (1H, t, H(3), H(5)
and H(4)); 7.67–7.61 (1H, s, H(10)); 7.04 (1H, d, H(12); 7.44–7.33
(1H, t, H(13)); 7.48–7.33 (1H, d, H(14)); 2.39 (3H, s, H(15)); 10.50
(1H, s, N(2)H); 9.01 (1H, s, N(3)H). 13C NMR (DMSO-d6): d
(ppm) = 176.71, C8@S; 137.31, C7@N; 149.49, C1; 126.83, (C2,
C6); 128.19, (C3, C5); 129.32, C4; 140.90–140.68, C9; 112.35–
111.86, C10; 111.86–111.46, C12; 14.48, C15. nJ(1H): 6.17, 1J(H2,
H3); 2.73, 2J(H2, H4); 11.15, 1J(H12, H13); 2.23 2J(H12, H14).
2.2.1.3. N(3)-meta-chlorophenyl-benzophenone-thiosemicarbazone,
HBz3mCl (3). White solid. Yield: 70%. IR (KBr, cmꢁ1):
m
(N3AH)
3342 s,
m(N2AH) 3292 s, m(C@N) 1588 s, m(C@S) 804 w. UV–Vis
(DMF, cmꢁ1): 31,348. The main signals in 1H NMR (DMSO-d6): d
(ppm) = 7.74–7.65 (1H, d, H(2), H(6)); 7.45–7.37 (1H, t, H(3), H(5)
and H(4)); 7.74–7.65 (1H, s, H(10)); 7.31–7.27 (1H, d, H(12);
7.45–7.37 (1H, t, H(13)); 7.60–7.56 (1H, d, H(14)); 10.50 (1H, s,
Fig. 1. General structure of N(3)-phenyl-acethophenone- and benzophenone-
derived thiosemicarbazones.
N(2)H); 9.01 (1H, s, N(3)H). 13C NMR (DMSO-d6):
d
(ppm) = 176.01, C8@S; 136.14, C7@N; 150.39, C1; 128.37, (C2,
C6); 129.73, (C3, C5); 129.99, C4; 140.31, C9; 127.89, C10;
125.34, C12. nJ(1H): 7.29, 1J(H12, H13); 7.92, 1J(H13, H14).
The X-ray diffraction measurements were carried out on a GEM-
INI-Ultra diffractometer. The data collection, cell refinement re-
sults, and data reduction were performed using the CRYSALISPRO
software [10]. Semi-empirical from equivalents absorption correc-
tion method was applied [10]. The structures were solved by direct
methods using SHELXS-97 [11]. Full-matrix least-squares refine-
ment procedure on F2 with anisotropic thermal parameters was
carried on using SHELXL-97 [11]. Positional and anisotropic atomic
displacement parameters were refined for all non-hydrogen atoms.
Hydrogen atoms were placed geometrically and the positional
parameters were refined using a riding model.
2.2.1.4.
HBz3mF (4). White solid. Yield: 88%. IR (KBr, cmꢁ1):
3302 s, (N2AH) 3198 s, (C@N) 1546 s, (C@S) 780 w. UV–Vis
N(3)-meta-fluorphenyl-benzophenone-thiosemicarbazone,
m
(N3AH)
m
m
m
(DMF, cmꢁ1): 31,446. The main signals in 1H NMR (DMSO-d6): d
(ppm) = 7.75–7.71 (1H, d, H(2), H(6)); 7.43–7.39 (1H, t, H(3), H(5)
and H(4)); 7.58 (1H, s, H(10)); 7.07 (1H, d, H(12); 7.68–7.65 (1H,
t, H(13)); 7.68–7.65 (1H, d, H(14)); 10.52 (1H, s, N(2)H); 9.03
(1H, s, N(3)H). 13C NMR (DMSO-d6): d (ppm) = 175.93, C8@S;
150.32, C7@N;, C1; 127.62, (C2, C6); 128.37, (C3, C5); 129.97, C4;
140.65–140.43, C9; 112.69–112.34, C10; 112.20–111.93, C12.
nJ(1H): 6.08, 1J(H12, H13); 2.53, 1J(H13, H14).
2.2. Syntheses
2.2.1. Synthesis of N(3)-meta-chlorophenyl- (HAc3mCl, 1) and N(3)-
meta-fluorphenyl- (HAc3mF, 2) acetophenone thiosemicarbazone, and
N(3)-meta-chlorophenyl- (HBz3mCl, 3) and N(3)-meta-fluorphenyl-
(HBz3mF, 4) benzophenone thiosemicarbazone
2.2.2. Synthesis of the zinc(II) complexes with N(3)-meta-chlorophenyl
and N(3)-meta-fluorphenyl acetophenone- and benzophenone-thiose
micarbazones
The thiosemicarbazones were prepared by a method described
in the literature [12]. A solution of hydrazine hydrate (10 mmol)
in methanol (10 mL) was added to a solution of the desired isothi-
ocianate (10 mmol in 10 mL of methanol). The reaction mixture
was kept under stirring in an ice bath for 15 min. Thereafter, the
reaction was stirred for 24 h at room temperature. The obtained
thiosemicarbazide was filtered and washed with diethyl ether.
The thiosemicarbazide (5 mmol) was then dissolved in methanol
(10 mL) and mixed to a solution of acetophenone or benzophenone
(5 mmol) in methanol (10 mL) with addition of two drops of con-
centrated sulfuric acid. The reaction mixture was kept under stir-
ring for 24 h at room temperature. The resulting solids were
filtered off, washed with methanol and ether and dried in vacuum.
The zinc(II) complexes were obtained by refluxing an ethanol
solution of the desired thiosemicarbazone with zinc(II) chloride
and triethylamine in 1:1:1 ligand-to-metal-to-triethylamine molar
ratio. The obtained solids were washed with ethanol and diethyl
ether and then dried under vacuum.
2.2.2.1. Bis[(N(3)-meta-chlorophenylacetophenone-thiosemicarbazo-
nato)zinc(II)], [Zn(Ac3mCl)2] (5). Yellow solid. Yield: 74%. Anal. Calc.
(MW 671.0) C, 53.70%; H, 3.91%; N, 12.52%. Found: C, 53.87%; H,
3.80%; N, 12.72.57%. Molar conductivity (1 ꢂ 10ꢁ3 mol Lꢁ1 DMF):
0.44
X
-1 cm2 molꢁ1. IR (KBr, cmꢁ1):
m(N3AH) 3414 m,
m(C@N)
1490 s,
m
(C@S) 762 w,
m
(ZnAN) 423 m, (ZnAS) 367 m. UV–Vis
m
(DMF, cmꢁ1): 33,783, 30,769. The main signals in 1H NMR
(DMSO-d6): d (ppm) = 7.57–7.53 (1H, d, H(2), H(6)); 7.34–7.14
(1H, t, H(3), H(5) and H(4)); 7.87 (1H, s, H(10)); 6.99–6.95 (1H, d,
H(12); 7.34–7.14 (1H, t, H(13)); 7.53–7.44 (1H, d, H(14)); 9.42
(1H, s, N(3)H). 13C NMR (DMSO-d6): d (ppm) = 167.05, C8@S;
132.61, C7@N; 137.30, C1; 127.34, (C2, C6); 128.16, (C3, C5);
142.33, C9; 120.81, C10; 119.36, C12; 21.18, C15. nJ(1H): 7.25,
1J(H2, H3); 7.57, 1J(H12, H13); 8.31, 1J(H13, H14).
2.2.1.1. N(3)-meta-chlorophenyl-acetophenone-thiosemicarbazone,
HAc3mCl (1). White solid. Yield: 68%. IR (KBr, cmꢁ1):
m(N3AH)
3295 s, m(N2AH) 3239 m, m(C@N) 1520 s, m(C@S) 793 w. UV–Vis
(DMF, cmꢁ1): 32362. The main signals in 1H NMR (DMSO-d6): d
(ppm) = 8.04–7.99 (1H, d, H(2), H(6)); 7.44–7.39 (1H, t, H(3),
H(4), H(5)); 7.79 (1H, s, H(10)); 7.28–7.24 (1H, d, H(12); 7.43–
7.39 (1H, t, H(13)); 7.61–7.57 (1H, d, H(14)); 10.77 (1H, s,
N(2)H); 10.12 (1H, s, N(3)H). 13C NMR (DMSO-d6):
d
2.2.2.2. bis[(N(3)-meta-fluorphenylacetophenone-thiosemicarbazona-
to)zinc(II)], [Zn(Ac3mF)2] (6). Yellow solid. Yield: 73%. Anal. Calc.
(MW 638.09) C, 56.47%; H, 4.11%; N, 13.17%. Found: C, 56.44%;
H, 4.00%; N, 13.27%. Molar conductivity (1 ꢂ 10ꢁ3 mol Lꢁ1 DMF):
(ppm) = 176.83, C8@S; 132.08, C7@N; 149.51, C1; 126.85, (C2,
C6); 128.19, (C3, C5 and C4); 140.58, C9; 125.11, C10; 124.92,
C12; 14.49, C15. nJ(1H): 6.01, 1J(H2, H3); 3.26, 1J(H6, H5); 3.26,
2J(H2, H4); 8.07, 1J(H12, H13); 8.07, 1J(H13, H14).
0.18
X m(N3AH) 3330 m, m(C@N)
ꢁ1 cm2 molꢁ1. IR (KBr, cmꢁ1):

104
K.S.O. Ferraz et al. / Journal of Molecular Structure 1008 (2012) 102–107
1500 s,
m
(C@S) 756 w,
m
(ZnAN) 418 m,
m
(ZnAS) 349 m. UV–Vis
107.77–107.34, C12. nJ(1H): 6.69, 1J(H2, H3); 7.96, 1J(H12, H13);
12.49, 1J(H13, H14).
(DMF, cmꢁ1): 31,152, 29,940. The main signals in 1H NMR
(DMSO-d6): d (ppm) = 7.65–7.53 (1H, d, H(2), H(6)); 7.33–7.19
(1H, t, H(3), H(5) and H(4)); 7.65 (1H, s, H(10)); 6.74 (1H, d,
H(12); 7.33–7.19 (1H, t, H(13)); 7.33–7.19 (1H, d, H(14)); 9.43
(1H, s, N(3)H). 13C NMR (DMSO-d6): d (ppm) = 167.11, C8@S;
137.30, C7@N; 159.64, C1; 127.34, (C2, C6); 128.19, (C3, C5);
142.82–142.59, C9; 106.75–106.22, C10; 107.85–107.76, C12.
nJ(1H): 8.04, 1J(H12, H13).
2.3. X-ray crystallography
Upon slow evaporation of 2, 5 and 8 in 9:1 acetone/DMSO crys-
tals of HAc3mF (2), [Zn(Ac3mCl)2] (5), and [Zn(Bz3mF)2]ꢀDMSO
(8a) were formed and their crystal structures were determined
using single-crystal X-ray diffractometry.
A summary of the crystals data, data collection details and
refinement results are listed in Table 1. Molecular graphics and
packing figures were prepared using ORTEP [13] and PLATON
[14], respectively.
2.2.2.3. Bis[(N(3)-meta-chlorophenylbenzophenone-thiosemicarbazo-
nato)zinc(II)], [Zn(Bz3mCl)2] (7). Yellow solid. Yield: 70%. Anal. Calc.
(MW 795.13) C, 60.42%; H, 3.81%; N, 10.54%. Found: C, 60.14%; H,
3.80%; N, 10.57%. Molar conductivity (1 ꢂ 10ꢁ3 mol Lꢁ1 DMF):
0.09
X
ꢁ1 cm2 molꢁ1. IR (KBr, cmꢁ1):
m
(N3AH) 3320 m,
m(C@N)
3. Results and discussion
1481 s,
m
(C@S) 777 w,
m
(ZnAN) 420 m, (ZnAS) 349 m. UV–Vis
m
(DMF, cmꢁ1): 31,250, 27,778. The main signals in 1H NMR
(DMSO-d6): d (ppm) = 6.81 (1H, d, H(2), H(6)); 6.99–6.92 (1H, t,
H(3), H(5)); 6.82 (1H, d, H(12); 7.50–7.45 (1H, t, H(13)); 7.24
(1H, d, H(14)); 9.42 (1H, s, N(3)H). 13C NMR (DMSO-d6): d
(ppm) = 168.06, C8@S; 132.63, C7@N; 136.67, C1; 129.27, (C2,
C6); 129.49 (C3, C5); 141.94, C9; 120.94, C10; 117.64, C12.
nJ(1H): 8.03, 1J(H12, H13); 8.42, 1J(H13, H14).
3.1. Formation of the thiosemicarbazones and zinc(II) complexes
Formation of the thiosemicarbazones was confirmed by their IR,
electronic and NMR spectra. Microanalyses and molar conductivity
data indicated the formation of [Zn(Ac3mCl)2] (5), [Zn(Ac3mF)2]
(6), [Zn(Bz3mCl)2] (7), and [Zn(Bz3mF)2] (8) in which two anionic
thiosemicarbazones are attached to the zinc(II) center.
2.2.2.4. Bis[(N(3)-meta-fluorphenylbenzophenone-thiosemicarbazo-
nato)zinc(II)], [Zn(Bz3mF)2] (8). Yellow solid. Yield: 74%. Anal. Calc.
(MW 762.23) C, 63.03%; H, 3.97%; N, 11.03%. Found: C, 62.83%; H,
3.76%; N, 11.28%. Molar conductivity (1 ꢂ 10ꢁ3 mol Lꢁ1 DMF):
3.2. Characterization
3.2.1. IR spectra
In the infrared spectra of the thiosemicarbazones absorptions
0.35
X
ꢁ1 cm2 molꢁ1. IR (KBr, cmꢁ1):
m(N3AH) 3318 m,
m
(C@N)
at 3342–3295 cmꢁ1 were assigned to the
m
(NAH) stretching vibra-
tions [15]. The absence of the absorption attributed to (N2AH) in
the spectra of the complexes is according to coordination of an
1481 s,
m(C@S) 755 w,
m
(ZnAN) 419 m, (ZnAS) 349 m. UV–Vis
m
m
(DMF, cmꢁ1): 29,851, 27,322. The main signals in 1H NMR
(DMSO-d6): d (ppm) = 7.50–7.47 (1H, d, H(2), H(6)); 7.40–7.36
(1H, t, H(3), H(5)); 6.58 (1H, d, H(12); 7.07 (1H, t, H(13)); 6.99–
6.96 (1H, d, H(14)); 9.44 (1H, s, N(3)H). 13C NMR (DMSO-d6): d
(ppm) = 167.90, C8@S; 136.90, C7@N; 159.50, C1; 128.31, (C2,
C6); 129.45 (C3, C5); 142.36–142.13, C9; 105.94–105.91, C10;
anionic thiosemicarbazone [16,4].The band assigned to
m(C@N)
at 1588–1520 cmꢁ1 in the spectra of the thiosemicarbazones
shifts to 1500–1481 cmꢁ1 in the spectra of complexes (5–8) sug-
gesting coordination of the imine nitrogen [17]. The absorption
attributed to
m
(C@S) at 804–780 cmꢁ1 in the spectra of the free
Table 1
Crystal data and refinement results for HAc3mF (2), [Zn(Ac3mCl)2] (5) and [Zn(Bz3mF)2]ꢀDMSO (8a).
Identification code
(2)
(5)
(8a)
Empirical formula
Formula weight (g molꢁ1
Crystal system
Space group
Temperature (K)
Radiation, k (Å)
C
16H16FN3S
C30H26Cl2N6S2Zn
670.96
Monoclinic
C 2/c
C42H36F2N6OS3Zn
840.32
)
301.38
Triclinic
P ꢁ 1
293(2)
Triclinic
P ꢁ 1
293(2)
250(2)
Mo K
a, 0.71073
Cu K
a, 1.54184
Mo Ka, 0.71073
h Range for data collection
3.00–26.37
4.71–58.93
4.08–26.37
Limiting indices
ꢁ6 6 h 6 7, ꢁ10 6 k 6 13,
ꢁ14 6 l 6 13
5.8624(2)
10.5083(4)
12.0065(4)
74.714(3)
86.591(3)
89.559(3)
712.19(4)
316
2/1.405
0.235
5414
ꢁ21 6 h 6 21, ꢁ9 6 k 6 10,
ꢁ19 6 l 6 14
19.3896(16)
9.0743(5)
17.4434(14)
90
104.534
90
2970.9(4)
1376
ꢁ13 6 h 6 13, ꢁ14 6 k 6 14,
ꢁ22 6 l 6 22
10.4751(2)
11.4047(2)
18.3352(4)
79.654(2)
75.821(2)
71.934(2)
2006.19(7)
868
2/1.391
0.819
32790
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
Volume (Å3)
F(000)
Z/D calc. (mg mꢁ3
)
4/1.500
4.371
9168
Absorption coefficient
Reflections collected
l
(mmꢁ1
)
Reflections unique/R(int)
Completeness to h
Data/restraints/parameters
2901/0.0218
99.9% (h = 26.37)
2901/0/181
R1 = 0.0430, wR2 = 0.1071
R1 = 0.0694, wR2 = 0.1147
0.953
2132/0.0467
100.0% (h = 58.93)
2132/0/187
R1 = 0.0416, wR2 = 0.1024
R1 = 0.0646, wR2 = 0.1180
1.051
8170/0.0305
99.6% (h = 26.37)
8170/168/588
R1 = 0.0324, wR2 = 0.0839
R1 = 0.0458, wR2 = 0.0871
1.039
Final R indices [I > 2
R indices (all data)
r(I)]
Goodness-of-fit on F2
Largest difference in peak and hole
0.368 and ꢁ0.263
0.252 and ꢁ0.273
0.733 and ꢁ0.433
(e Å3)

K.S.O. Ferraz et al. / Journal of Molecular Structure 1008 (2012) 102–107
105
thiosemicarbazones shifts to 777–755 cmꢁ1 in the spectra of the
complexes, indicating coordination through thiolate sulfur
[9,18,19]. New absorptions at 423–418 cmꢁ1 and 367–349 cmꢁ1
in the spectra of the complexes were assigned to (ZnAN) and
(ZnAS), respectively [4,20,21]. Hence the infrared spectra indi-
3.2.4. X-ray crystallography
a
In the structure of HAc3mF (2) the thiosemicarbazone backbone is al-
most planar with a mean plane deviation of 0.0293 Å. The compound
adopts the EE conformation in relation to the C7@N1 and C8AN2 bonds
[25] (see Fig. 2). In the molecular packing dimmers are generated by pairs
of NAHꢀꢀꢀS hydrogen bonds (d(DꢀꢀꢀA) = 3.8135 (16) Å; \(DHA) = 175.7°)
related to each other by an inversion center [26] (Fig. 2).
m
m
cate coordination through the NAS chelating system.
3.2.2. Electronic spectra
Fig. 3 shows the molecular structures of [Zn(Ac3mCl)2] (5) and
[Zn(Bz3mF)2]ꢀDMSO (8a). The asymmetric unit of 5 contains half
of a [Zn(Ac3mCl)2] molecule. In [Zn(Bz3mF)2]ꢀDMSO (8a) the
meta-fluorphenyl ring and the DMSO solvent molecules have
shown to be twofold disordered; the refined occupancies con-
verged to 72:28 and 54:46, respectively. We may suspect that
the structure of 8a would present higher symmetry in the absence
of DMSO and of the disorder in the meta-fluorphenyl ring. In fact
the distances and angles in the two ligands of complex (8a) are
not significantly different (see Table 2).
The electronic spectra of the acetophenone-derived thiosemi-
carbazones show an absorption at ca. 32,600–32,300 cmꢁ1 while
those of the benzophenone-derived thiosemicarbazones exhibit a
band at ca. 31,450–31,350 cmꢁ1. This absorption is attributed to
the
p ?
pꢃ transition of the benzene ring and the n ? pꢃ transi-
tions of the azomethine and thioamide functions overlapped in
the same envelope [22,23]. In the spectra of the zinc(II) complexes
two absorptions were observed at ca. 33,780–31,150 cmꢁ1 and ca.
30,770–29,940 cmꢁ1 for the acetophenone-derived thiosemicarba-
zones and at ca. 31,250–29,850 cmꢁ1 and 27,800–27,300 cmꢁ1 for
the benzophenone-derived thiosemicarbazones. The first is attrib-
Selected intra-molecular bond distances and angles in the struc-
tures of HAc3mF (2), [Zn(Ac3mCl)2] (5) and [Zn(Bz3mF)2]ꢀDMSO
(8a) are given in Table 2.
uted to the
p ?
pꢃ transition of the benzene ring and the second to
the n ? pꢃ transitions of C@N and C@S [16]. The two separate
absorptions observed in the spectra of the complexes are due to
the formation of a highly delocalized system upon deprotonation
at N2AH, involving the benzene ring and the thiosemicarbazone
chain. Hence the n ? pꢃ transitions appear at lower energies in
the complexes.
In complexes (5) and (8a) two anionic thiosemicarbazones are
attached to the zinc(II) center through the NAS chelating system.
The geometry around the metal is highly distorted tetrahedral.
The small N1AZn1AS1 (5) and N1AZn1AS11, N11AZn1AS101
(8a) angles (86.5–87.5°) are very different from the expected angle
of 109° for a perfect tetrahedron, probably due to the rigidity of the
thiosemicarbazone’s NAS chelating system [27]. As a consequence
the N1AZn1AS10- (5) and N1AZn1AS101, N11AZn1AS1 (8a) an-
gles are 137.45(9)° in 5 and 129.02(4)°, 128.81(4)° in 8a. The
sum of the N1AZn1AS1, N1AZn1AS10, N10AZn1AS0, N10AZn1AS1
angles is 442.7° for complex (5) and the sum of the equivalent an-
gles in complex (8a) are 446.16° and 445.38°, while the sum of the
four angles of a perfect tetrahedron is 437.88°. Hence, as already
mentioned, the geometries of 5 and 8a are highly distorted
tetrahedral.
In complexes (5) and (8a) the coordinated thiosemicarbazone
adopts the EZ conformation in relation to the C7AN1 and N2AC8
bonds.
Comparison between complexes (5) and (8a) reveals that the two
compounds present comparable bond distances. In general the bond
angles of the thiosemicarbazone chain in the two complexes are also
not significantly different. However, the angles comprising the me-
tal are not similar.
3.2.3. NMR spectra
The NMR spectra of the thiosemicarbazones and their zinc(II)
complexes were recorded in DMSO-d6. The 1H resonances were as-
signed on the basis of chemical shifts and multiplicities. The carbon
type (C, CH) was determined by using distortion less enhancement
by polarization transfer (DEPT135) experiments.
In the 1H and 13C NMR spectra of HAc3mF (2) and HBz3mF (4)
and their zinc(II) complexes (6 and 8) the fluor nucleus couples
with neighbor hydrogen and carbon nuclei resulting in splitting
of the hydrogen and carbon signals. In the 1H NMR spectra of all
complexes the signal of N2AH is absent due to deprotonation
and formation of an anionic ligand. The signals of N3AH undergo
significant shifts in relation to their position in the free thiosemi-
carbazones, indicating coordination through the sulfur. The signals
of CH3 from the acetophenone group shift significantly upon com-
plexation suggesting coordination through the imine nitrogen [22].
Upon coordination significant shifts were observed in the 13C NMR
signals especially for C2, C@N, C@S and C9, which also confirms
coordination of the thiosemicarbazone through the imine nitrogen
and the sulfur in the thiolate form [9,24].
Considering that the bond distances do not significantly vary in
complexes (5) and (8a) in spite of the fact that 5 contains a chloro
substituent while 8a contains a fluor substituent at the N(3)-phenyl
group, comparisons of bond distances could in principle be made
Fig. 2. Molecular structure of HAc3mF (2) showing the labelling scheme of the non-H atoms and their displacement ellipsoids at the 50% probability level (left) together with
the NAHꢀ ꢀ ꢀS hydrogen bonds indicated by dashed lines (right).

106
K.S.O. Ferraz et al. / Journal of Molecular Structure 1008 (2012) 102–107
Fig. 3. Molecular structures of [Zn(Ac3mCl)2] (5) and [Zn(Bz3mF)2]ꢀDMSO (8a) showing the labelling scheme of the non-H atoms and their displacement ellipsoids at the 50%
probability level. In 5, the ‘‘prime’’ atoms were generated by [ꢁx, y, ꢁz + 1/2].
Table 2
Selected bonds distances (Å), and angles (°) for HAc3mF (2), [Zn(Ac3mCl)2] (5) and [Zn(Bz3mF)2]ꢀDMSO (8a). Standard deviation in parenthesis.
Atoms
(2)
Atoms
(5)
Atoms
(8a)
Distance (Å)
–
–
S1AC8
N1AC7
N1AN2
N2AC8
N3AC8
–
–
Zn1AN1
Zn1AS1
S1AC8
N1AC7
N1AN2
N2AC8
N3AC8
2.075(3)
2.2884(11)
1.738(4)
1.309(5)
1.387(4)
1.283(5)
1.379(5)
Zn1AN1/Zn1AN11
Zn1AS101/Zn1AS11
S11AC8/S101AC108
N1AC7/N11AC107
N1AN2/N11AN12
N2AC8/N12AC108
N3AC8/N13AC108
2.0537(14)/2.0566(14)
2.2849(5)/2.2726(5)
1.7513(18)/1.7470(17)
1.304(2)/1.302(2)
1.391(2)/1.3885(19)
1.298(2)/1.302(2)
1.670(2)
1.281(2)
1.374(2)
1.354(2)
1.341(3)
1.369(2)/1.365(2)
Angles (°)
–
–
–
–
–
–
–
–
N1’AZn1AN1
S1’AZn1AS1
N1AZn1AS1
N1AZn1AS10
C8AS1AZn1
C7AN1AN2
N1AN2AC8
N2AC8AS1
N3AC8AS1
N3AC8AN2
107.80(16)
111.82(6)
85.63(8)
137.45(9)
93.21(14)
113.9(3)
115.2(3)
129.0(3)
113.1(3)
117.9(4)
N1AZn1AN11
S101AZn1AS11
115.01(6)
114.561(19)
N1AZn1AS11/N11AZn1AS101
N1AZn1AS101/N11AZn1AS1
C8AS11AZn1/C108AS101AZn1
C7AN1AN2/C107AN11AN12
N1AN2AC8/N11AN12AC108
N2AC8AS11/N12AC108AS101
N3AC8AS11/N13AC108AS101
N2AC8AN3/N12AC108AN13
87.57(4)/87.00(4)
129.02(4)/128.81(4)
92.30(6)/92.47(6)
115.28(14)/114.87(14)
115.90(14)/116.00(14)
128.44(13)/128.17(13)
113.64(13)/113.97(13)
117.91(16)/117.86(15)
–
–
C7AN1AN2
N1AN2AC8
N2AC8AS1
S1AC8AN3
N3AC8AN2
118.94(17)
119.17(16)
119.81(15)
125.62(15)
114.52(17)
a
0
Symmetry operation: = ꢁx, y, ꢁz + 1/2.
between HAc3mF (2) and the acetophenone thiosemicarbazone
complex (5). C8AS1, which is a predominantly double bond, varies
from 1.670(2) Å in 2 to 1.738(4) Å in 5 as a consequence of deproto-
nation with formation of a new predominantly single bond [28]. The
N2AC8 bond goes from 1.354(2) Å in 2 to 1.283 (5) Å in 5 due to this
same effect. Significant modifications were observed as well in the
bond angles involving the sulfur atom in 2 and 5.
We were not able to grow crystals of complexes (6) and (7) but
considering that both 5 and 8a are highly distorted tetrahedral we
may assume that 6 and 7 probably present the same geometry.
4. Conclusions
N(3)-meta-chlorophenyl- and N(3)-meta-fluorphenyl thiosemi-
carbazones derived from acetophenone and benzophenone coordi-
nate to zinc(II) forming [Zn(L2)] (L = anionic thiosemicarbazone)
complexes, in which the bidentate thiosemicarbazone ligands
adopt the EZ conformation in relation to the C7AN1 and N2AC8
bonds.
The presence of triethylamine in the reaction mixture induced
deprotonation at N(2)AH and the excess of zinc(II) probably

K.S.O. Ferraz et al. / Journal of Molecular Structure 1008 (2012) 102–107
107
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the d10 configuration of zinc(II) affords no crystal field stabilization,
the presence of rather bulky thiosemicarbazone ligands also prob-
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responsible for the highly distorted tetrahedral geometry of the
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CCDC 844586, 844587 and 844588 contain the supplementary
crystallographic data for thiosemicarbazone (2) and complexes
(5) and (8a). These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223 336033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be found, in
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