Novel 3d-metal complexes with 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole: Synthesis, spectroscopic and structural investigations

Article abstract of DOI:10.1016/j.poly.2010.01.015

A series of new 3d-metal complexes have been prepared by the reaction of M(CH₃COO)₂ (M = Zn(II), Co(II), Ni(II)) and 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole (HL) in a methanol (3) or a methanol/dmf (1, 2) medium. All the complexes have been studied by elemental analyses, electronic and IR spectroscopies. The zinc(II) complex 1 and the ligand HL have been investigated using the method of ¹H NMR-spectroscopy at various temperatures. The disappearance of the signal from one proton of the amino group H(5) in the spectrum of complex 1 confirmed the existence of the ligand in the deprotonated form. According to the data of the ¹H NMR-spectroscopy, the ligand HL is coordinated to zinc(II) through the nitrogen atom of the deprotonated amino group and the nitrogen atom of the benzothiazole substituent. These data are in agreement with X-ray structural studies for the ligand HL and the zinc(II) complex 1.

Full text of DOI:10.1016/j.poly.2010.01.015

Polyhedron 29 (2010) 1363–1369
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Polyhedron
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Novel 3d-metal complexes with 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyr-
role: Synthesis, spectroscopic and structural investigations
a
a
b
Sergiy O. Nikitin a, , Rostyslav D. Lampeka , Yulian M. Volovenko , Gennady V. Palamarchuk ,
*
Oleg V. Shishkin b,c
a Department of Chemistry, Kyiv National Taras Shevchenko University, Volodymyrska Str. 64, Kyiv 01601, Ukraine
b Division of Functional Materials Chemistry, STC, Institute for Single Crystals, National Academy of Sciences of Ukraine, Lenina Ave. 60, Kharkiv 61001, Ukraine
c Department of Inorganic Chemistry, V.M. Karazin Kharkiv National University, Svobody Sq. 4, Kharkiv 61077, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 July 2009
Accepted 4 January 2010
Available online 20 January 2010
A series of new 3d-metal complexes have been prepared by the reaction of M(CH3COO)2 (M = Zn(II),
Co(II), Ni(II)) and 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole (HL) in a methanol (3) or a meth-
anol/dmf (1, 2) medium. All the complexes have been studied by elemental analyses, electronic and
IR spectroscopies. The zinc(II) complex 1 and the ligand HL have been investigated using the method
of 1H NMR-spectroscopy at various temperatures. The disappearance of the signal from one proton of
the amino group H(5) in the spectrum of complex 1 confirmed the existence of the ligand in the depro-
tonated form. According to the data of the 1H NMR-spectroscopy, the ligand HL is coordinated to zinc(II)
through the nitrogen atom of the deprotonated amino group and the nitrogen atom of the benzothiazole
substituent. These data are in agreement with X-ray structural studies for the ligand HL and the zinc(II)
complex 1.
Keywords:
2-Amino-4(5H)-ketopyrrole
3d-metal complexes
Spectroscopic investigation
Crystal structure
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
ketopyrrole, as well as X-ray structural investigations of the afore-
mentioned ligand HL and its zinc(II) complex 1.
Biologically active ligands and their metal ion complexes have
received increasing attention owing to the role which such systems
play in many biological processes. Many organic compounds which
are used in medicine do not have a purely organic mode of action;
some are activated or biotransformed by metal ions. Many drugs
have been known to exhibit increased anticancer activity when
administered as metal complexes [1–4].
In light of the increase in biological activity of chemicals due to
their coordination to metal ions and keeping in mind the high
anticancer activity of 2-amino-4(5H)-ketopyrroles [5], their use
as ligands towards transition metal ions is interesting and promis-
ing. It should be noted that 2-amino-4(5H)-ketopyrroles (as well as
2-amino-4(5H)-ketothiophens) potentially have a wide spectrum
of binding possibilities, but to date examples of coordination com-
pounds with such ligands are scarce [6,7]. So, in order to test and
extend the scope of the coordination abilities of 2-amino-4(5H)-
ketopyrroles, the residue with an additional amino group, 1,2-dia-
mino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole, has been used as a
ligand towards 3d-metal ions. In this paper we describe the syn-
thesis and spectroscopic characterization of new Zn(II), Co(II) and
Ni(II) complexes with 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-
2. Experimental
2.1. Materials and instruments
Elemental analyses were performed by atomic absorption spec-
troscopy (for metals) and with a Perkin–Elmer 2400 CHN Analyzer
(for C, H, N). Infrared spectra were recorded as KBr pellets on a
BX (Perkin–Elmer) spectrometer in the 4000–400 cmꢀ1 region using
conventional techniques. Electronic spectra of the compounds in
dmf solution were recorded on a LOMO MDR-23 spectrophotome-
ter in the 400–800 cmꢀ1 region at room temperature. 1H NMR
spectra in DMSO-d6 solution were recorded on a Varian 400 spec-
trometer (with Me4Si as an internal standard).
2.2. Crystal structure determination
Crystallographic data and parameters of data collection, struc-
ture solution and refinement are listed in Table 1. Intensities of
reflections were measured on an automatic Xcalibur-3 diffractom-
eter (graphite monochromated Mo K
a radiation, CCD-detector, x
scanning). All structures were solved by direct methods using the
SHELX97 package [8]. Positions of hydrogen atoms were located
from electron density difference maps and refined isotropically.
* Corresponding author. Tel.: +380 44 239 3392; fax: +380 44 490 7185.
E-mail address: nikchem@ukr.net (S.O. Nikitin).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.01.015

1364
S.O. Nikitin et al. / Polyhedron 29 (2010) 1363–1369
Table 1
0.0075 mol of hydrazine. The reaction mixture was refluxed for
Crystal data and structure refinement for HL and 1.
4 h. Control for the reaction completion was achieved by monitor-
ing of disappearance of the starting chlorobutyronitrile by TLC. The
resulting pale yellow crystals were filtrated, washed with cold eth-
anol and dried in the air. Yield: 0.52 g (85%). M.p. = 237 °C. Anal.
Calc. for C11H10N4OS: C, 53.64; H, 4.09; N, 22.75. Found: C, 53.58;
H, 4.13; N, 22.67%. 1H NMR (200 MHz in DMSO-d6, d, ppm): 7.83
(1H, d, benzothiazole), 7.70 (1H, d, benzothiazole), 7.33 (1H, t, ben-
zothiazole), 7.19 (1H, t, benzothiazole), 8.32 (1H, s, amine), 7.97
(1H, s, amine), 4.88 (2H, s, amine), 3.87 (2H, s, methylene). The
compound is soluble in ethanol, dmf and dmso.
Compound
HL
1
Empirical formula
Molecular weight
Crystal system
Space group
a (Å)
C11H10N4OS
246.29
monoclinic
P21/c
9.54570(10)
11.8099(2)
10.0749(2)
C22H18N8O2S2Zn, C3H7NO, H2O
647.05
triclinic
P1
10.9481(4)
11.3100(3)
12.3978(2)
94.085(2)
108.668(2)
104.372(3)
293
1389.73(7)
2
668
1.546
1.084
60
29 061
7978
0.028
5401
478
0.073
ꢀ
b (Å)
c (Å)
a
(°)
b (°)
(°)
98.762(2)
c
T (K)
293
1122.53(3)
4
V (Å3)
Z
2.3.3. Preparation of [ZnL2]ꢁH2Oꢁdmf (1)
To a solution of Zn(CH3COO)2ꢁ2H2O (0.15 mmol) in 5 mL of
methanol was added 10 mL of a dmf solution of HL (0.3 mmol).
The resulting solution was allowed to stand at room temperature.
Pale yellow crystals of 1 suitable for X-ray crystallography were
formed after 5 days. The crystals were filtered off, washed with
methanol and dried in the air. Yield: 64 mg (77%). Anal. Calc. for
C25H27N9O4S2Zn: C, 46.41; H, 4.21; N, 19.48; Zn, 10.10. Found: C,
F(0 0 0)
512
Dcalc (g/cm3)
1.457
0.276
60
17 137
3153
0.020
2413
194
l(Mo K
a
) (mmꢀ1
)
2hmax (°)
Measured reflections
Independent reflections
Rint
Reflections with F > 4
Number of parameters
r
(F)
46.55; H, 4.15; N, 19.57; Zn, 10.13%. IR (KBr pellet,
m
, cmꢀ1):
1590 (C@O), 1520 (C@N), 3450 and 3330 (N–H). The compound
is soluble in dmso and dmf.
wR2
0.098
0.033
1.07
R1 (F > 4r(F))
0.030
0.91
S
2.3.4. Preparation of [CoL2]ꢁH2O (2)
This complex was obtained in a similar manner to 1, except
with the use of Co(CH3COO)2ꢁ2H2O instead of Zn(CH3COO)2ꢁ2H2O.
Yield: 54 mg (65%). Anal. Calc. for C21H20N8O3S2Co: C, 46.56; H,
3.55; N, 19.74; Co, 10.38. Found: C, 46.42; H, 3.64; N, 19.61; Co,
Full-matrix least-squares refinement against F2 was performed for
non-hydrogen atoms within anisotropic approximation.
2.3. Preparations
10.21%. IR (KBr pellet, m
, cmꢀ1): 1580 (C@O), 1525 (C@N), 3315
and 3455 (N–H). The compound is soluble in dmso and dmf.
The ligand HL was prepared in two steps according to Scheme 1,
by reaction of 2-cyanomethyl-1,3-benzothiazole with chloracetyl
chloride, followed by the interaction of the obtained 2-benzothiaz-
olyl-3-keto-4-chlorobutyronitrile with hydrazine.
2.3.5. Preparation of [NiL2] (3)
This complex was obtained in a similar manner to 1, except
with the use of Ni(CH3COO)2ꢁ2H2O instead of Zn(CH3COO)2ꢁ2H2O
in methanol medium. Yield: 49 mg (59%). Anal. Calc. for
C21H20N8O2S2Ni: C, 48.11; H, 3.30; N, 20.40; Ni, 10.69. Found: C,
2.3.1. Preparation of 2-benzothiazolyl-3-keto-4-chlorobutyronitrile
To a solution of 0.01 mol of pyridine and 5 mol of 2-cyanometh-
yl-1,3-benzothiazole in absolute dioxane (20 mL) at 25 °C was
added slowly 0.006 mol of chloracetyl chloride. After refluxing
for 2 h, the dark brown solution was cooled to room temperature,
and 2-benzothiazolyl-3-keto-4-chlorobutyronitrile was precipi-
tated. This precipitate was filtrated, washed with water and cold
ethanol, and then dried in air. Yield: 1.01 g (80%). M.p. = 157 °C.
Anal. Calc. for C11H7ClN2OS: C, 52.70; H, 2.81; N, 11.17. Found: C,
52.61; H, 2.89; N, 11.23%. The compound is soluble in ethanol,
dmf and dmso.
47.94; H, 3.13; N, 19.91; Ni, 10.61%. IR (KBr pellet, m
, cmꢀ1): 1590
(C@O), 1535 (C@N), 3320 and 3450 (N–H). The compound is solu-
ble in dmso and dmf.
3. Results and discussion
3.1. Synthesis and spectroscopic characterization
The reaction between 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-
ketopyrrole (HL) in dmf and the appropriate metal salt
M(CH3COO)2 (M = Zn(II), Co(II) and Ni(II)) in methanol affords the
coordination compounds [ZnL2]ꢁH2Oꢁdmf (1), [CoL2] H2O (2) and
[NiL2] (3). Noticeably, 2-amino-4(5H)-ketopyrroles are structural
analogues of cytosine, which is coordinated by metal ions in depro-
tonated form in the presence of a strong base. In contrast to this, 2-
amino-4(5H)-ketopyrroles are coordinated by metal ions in the
deprotonated form even with the use of metal carboxylates:
2.3.2. Preparation of 1,2-diamino-3-(2-benzothiazolyl)-4(5H)-
ketopyrrole (HL)
About 0.0025 mol of the above 2-benzothiazolyl-3-keto-4-chlo-
robutyronitrile was dissolved in 20 mL of an ethanol solution of
O
S
N
S
N
O
Py
MðCH3COOÞ2 þ 2HL ¼ ½ML2ꢂ þ 2CH3COOH
Cl
+
Cl
CN
Cl
CN
O
The IR-spectrum of the ligand HL in the 3600–3000 cmꢀ1 region
shows stretching vibrations of the amino group
m(N-H) at
O
3350 cmꢀ1 (asymmetrical) and 3245 cmꢀ1 (symmetrical). In con-
S
N
S
trast to HL, the spectra of complexes 1–3 show two sets of bands
Cl
H2N NH2
+
N
due to
m(NH2) and m(NH) vibrations. The broad band around
N
NH2
CN
3460–3445 cmꢀ1 may be attributed to the stretching vibrations
of a non-coordinated NH2 group, while the sharp band appearing
in the range 3330–3310 cmꢀ1 could be assigned to the vibration
H2N
Scheme 1. Synthetic scheme for the ligand HL.

S.O. Nikitin et al. / Polyhedron 29 (2010) 1363–1369
1365
of the N–H bond of a deprotonated amino group. The presence of
the last band in the spectra of 1–3 could be a result of simulta-
neous deprotonation of the NH2 group of the ligand and its coordi-
nation to the metal ion, which is confirmed by the data of 1H NMR-
spectroscopy and X-ray analysis for 1.
The 1H NMR spectrum of the ligand HL shows four signals from
non-equivalent aromatic protons attributed to the benzothiazole
substituent. The ligand HL contains two different amino groups.
The protons of the first one are observed in the spectrum as a sharp
singlet (two equivalent protons H(6) at d = 4.85 ppm), while the
protons of the second one show up as two separate singlets
(H(5) at d = 7.95 ppm and H(50) at d = 8.33 ppm). The non-equiva-
lence of the protons of the second amino group is caused by the
participation of H(50) in the intramolecular hydrogen bonding with
nitrogen atom of the benzothiazole substituent. A comparison of
the 1H NMR spectra of 1 and HL reveals the shift of the aromatic
ring protons of 1 to the high-field region, with the lowest shift va-
lue for H(4). This fact could be explained by the remoteness of H(4)
from the metal centre (see Scheme 2) in contrast to the other aro-
matic ring protons H(1)–H(3), which are most sensitive to the
coordination by zinc(II). The existence of the ligand in the deproto-
nated form is confirmed by the disappearance of the signal from
one proton of the amino group H(50) in the 1H NMR spectrum of
the complex 1. Additionally, the signal of the proton H(5) (singlet
at d = 6.38 ppm) is shifted to higher field in comparison with the
free ligand, which proves the coordination of the ligand by zinc(II)
ion through the nitrogen atom of the deprotonated amino group
(see Fig. 1). The protons of the CH2 group of pyrrole ring of HL
are equivalent on the NMR-time scale at 20 °C and are observed
at d = 3.87 ppm as a singlet. In contrast to this, the corresponding
peak in complex 1 is shown as an AB quartet at d = 3.95 ppm,
2JH–H = 17 Hz. This splitting of the protons of the CH2 group is
caused by the slower interconversion process for the pyrrole ring
of the complex as compared to the free ligand. On increasing the
The spectrum of HL reveals a very broad and intense band in the
range 1610–1560 cmꢀ1 with several shoulders, assigned to a
superposition of stretching vibrations of C@O, C@N and C@C
bonds. In the spectra of complexes 1–3 the band for the C@O
stretching vibration is observed at 1590–1580 cmꢀ1 and the C@N
stretching vibration at 1535–1520 cmꢀ1. The shift of the
m(C@N)
band to an area of lower frequencies is used as a criterion of ligand
coordination to 3d-metal ions through the nitrogen of the benzo-
thiazole substituent and the deprotonated amino group of pyrrole.
Since all the complexes synthesized and discussed here demon-
strate very similar IR spectra, an assumption about the analogous
coordination modes of 2 and 3 to 1, the structure of which has been
determined by X-ray analysis, has been made.
H4
O
H3
H2
S
CH2
N
N
H/5
NH2
N
H1
H5
Scheme 2. The hydrogen atoms numbering scheme of the ligand HL.
Fig. 1. 1H NMR spectrum of [ZnL2]ꢁdmfꢁH2O (1) in DMSO-d6 solution at 20 °C.

1366
S.O. Nikitin et al. / Polyhedron 29 (2010) 1363–1369
temperature up to 70 °C, the signal from two inequivalent methy-
lene protons broadens and then coalesces. At temperatures higher
than 70 °C, this broadened signal is transformed into a singlet with
a narrow line width, which is the averaged signal from the CH2
groups of the two conformers (see Fig. 2).
The electronic spectra of 2 and 3 were recorded in dmf solution.
The spectrum of 2 shows only one band without any clear splitting
in the visible region. The absorption features are most likely d–d
transitions in origin, typical for Co(II) octahedral species. The band
4
at 20 500 cmꢀ1 could be tentatively attributed to the T1g(F) ?
4T1g(P) transition [9]. The spectrum of 3 is typical for a square–pla-
nar nickel(II) complex, and displays an intense absorption at
22 000 cmꢀ1, assigned to a metal-to-ligand charge transfer (MLCT)
band.
°
80 C
°
70 C
3.2. Crystal structures of the ligand HL and complex 1
°
60 C
°
50 C
X-ray structural investigations have been carried out for HL and
1, where compound 1 represents the complex of zinc(II) with the
deprotonated form of the ligand HL. The molecular structures of
HL and 1, together with their labelling schemes, are shown in Figs.
3 and 4, respectively. Selected bond lengths and angles are summa-
rized in Table 2.
°
40 C
°
35 C
°
30 C
In the structure of the free ligand HL, the pyrrole and benzothi-
azole fragments are co-planar (the angle between the planes is
1.5°). Such a conformation of the molecule is stabilized by an intra-
°
20 C
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
4.3 ppm
molecular N(2)–H(2B)ꢁꢁꢁN(1) hydrogen bond (Table 3) and
a
Fig. 2. Fragments of selected 1H NMR spectra of [ZnL2]ꢁdmfꢁH2O (1) in the region of
S(1)ꢁꢁꢁO(1) interaction (the SꢁꢁꢁO distance is 2.998(3) Å, the van
der Waals radii sum is 3.11 Å [10] and the C(1)–S(1)ꢁꢁꢁO(1) angle
the methylene protons at different temperatures. Solution of the complex in DMSO-
d6.
is 164.10(4)°), which can be considered as a
r-hole bonding [11],
i.e. an attractive interaction between the electron deficient sulfur
atom and electron excessive carbonyl oxygen. The geometry at
the N(3) atom of the pyrrole ring is best described as being slightly
pyramidal (the sum of bond angles centred at N(3) atom is 358.2°).
The deviation of the N(3) atom from the mean square plane of
other atoms of the pyrrole ring is 0.064 Å, reflecting a flattened
envelope conformation of the heterocycle. The amino group
N(2)H2 has an almost planar orientation with respect to the pyrrole
ring (the torsion angle H(2A)–N(2)–C(9)–C(8) is 175.36(12)°). The
second amino group, N(4)H2, has an orthogonal orientation relative
to the heterocycle (the torsion angle H(4A)–N(4)–N(3)–C(9) is
110.48(12)°), which is usual for hydrazine fragments.
The molecules of HL in the crystal phase form dimers because of
a stacking interaction of the aromatic fragments of the molecules
(the distance between their mean planes is 3.40 Å) and intermolec-
Fig. 3. Molecular structure of the compound HL with the atom numbering scheme.
Atom displacement ellipsoids are shown at the 50% probability level.
Fig. 4. Molecular structure of the compound [ZnL2]ꢁdmfꢁH2O (1) with the atom numbering scheme. Atom displacement ellipsoids are shown at the 50% probability level.

S.O. Nikitin et al. / Polyhedron 29 (2010) 1363–1369
1367
Table 2
Selected bond distances (Å) and angles (°) for the compounds HL and 1.
HL
S(1)–C(1)
S(1)–C(7)
O(1)–C(11)
N(1)–C(7)
N(1)–C(6)
N(2)–C(9)
N(3)–C(9)
N(3)–N(4)
N(3)–C(10)
C(7)–C(8)
C(8)–C(11)
C(8)–C(9)
C(10)–C(11)
1.736(1)
1.756(1)
1.236(2)
1.315(1)
1.384(2)
1.321(2)
1.334(1)
1.396(1)
1.452(2)
1.422(2)
1.413(2)
1.420(1)
1.524(2)
C(1)–S(1)–C(7)
C(7)–N(1)–C(6)
C(9)–N(3)–N(4)
C(9)–N(3)–C(10)
N(4)–N(3)–C(10)
C(2)–C(1)–S(1)
C(6)–C(1)–S(1)
N(1)–C(6)–C(5)
N(1)–C(6)–C(1)
N(1)–C(7)–C(8)
N(1)–C(7)–S(1)
88.94(5)
110.48(9)
120.9(1)
111.3(1)
126.0(1)
128.9(1)
109.7(1)
124.9(1)
115.5(1)
124.1(1)
115.4(1)
C(11)–C(8)–C(7)
C(9)–C(8)–C(7)
N(2)–C(9)–N(3)
N(2)–C(9)–C(8)
N(3)–C(9)–C(8)
N(3)–C(10)–C(11)
O(1)–C(11)–C(8)
O(1)–C(11)–C(10)
C(8)–C(11)–C(10)
C(8)–C(7)–S(1)
C(11)–C(8)–C(9)
127.4(1)
124.7(1)
123.0(1)
126.4(1)
110.6(1)
102.8(1)
129.1(1)
123.7(1)
107.2(1)
120.5(1)
107.9(1)
1
Zn(1)–N(2)
Zn(1)–N(5)
Zn(1)–N(3)
Zn(1)–N(6)
O(1)–C(3)
O(2)–C(15)
N(1)–N(7)
N(2)–C(5)
N(3)–C(6)
N(3)–C(12)
N(4)–C(14)
N(5)–C(17)
N(6)–C(18)
N(6)–C(24)
C(2)–C(3)
C(3)–C(4)
C(4)–C(6)
C(4)–C(5)
C(14)–C(15)
C(15)–C(16)
C(16)–C(18)
C(16)–C(17)
1.9442(16)
1.9458(13)
2.0393(12)
2.0425(11)
1.234(2)
1.2391(18)
1.402(2)
1.303(2)
1.3264(19)
1.390(2)
1.443(2)
1.3013(19)
1.3253(18)
1.3927(17)
1.512(3)
1.415(2)
1.400(2)
1.443(2)
1.519(2)
1.412(2)
1.4113(19)
1.437(2)
N(2)–Zn(1)–N(5)
N(2)–Zn(1)–N(3)
N(5)–Zn(1)–N(3)
N(2)–Zn(1)–N(6)
N(5)–Zn(1)–N(6)
N(3)–Zn(1)–N(6)
C(6)–N(3)–C(12)
C(6)–N(3)–Zn(1)
C(12)–N(3)–Zn(1)
C(17)–N(5)–Zn(1)
C(18)–N(6)–C(24)
C(18)–N(6)–Zn(1)
C(24)–N(6)–Zn(1)
N(1)–C(2)–C(3)
O(1)–C(3)–C(4)
O(1)–C(3)–C(2)
C(4)–C(3)–C(2)
125.0(1)
96.3(1)
116.9(1)
117.1(1)
96.0(1)
105.2(1)
112.2(1)
120.7(1)
126.4(1)
123.6(1)
112.0(1)
121.5(1)
126.3(1)
103.0(2)
129(2)
N(1)–C(5)–C(4)
N(3)–C(6)–C(4)
108.2(1)
125.8(1)
129.0(1)
123.8(1)
107.2(1)
125.3(1)
125.8(1)
108.9(1)
125.1(1)
126.9(1)
107.9(1)
125.9(1)
114.1(1)
120.0(1)
126.3(1)
108.5(2)
125.3(2)
126.5(2)
O(2)–C(15)–C(16)
O(2)–C(15)–C(14)
C(16)–C(15)–C(14)
C(18)–C(16)–C(15)
C(18)–C(16)–C(17)
C(15)–C(16)–C(17)
N(5)–C(17)–N(4)
N(5)–C(17)–C(16)
N(4)–C(17)–C(16)
N(6)–C(18)–C(16)
N(6)–C(18)–S(2)
C(16)–C(18)–S(2)
C(6)–C(4)–C(5)
123.6(2)
107.4(2)
125.2(2)
C(3)–C(4)–C(5)
N(2)–C(5)–N(1)
N(2)–C(5)–C(4)
C(6)–C(4)–C(3)
Table 3
Hydrogen bonding distances (Å) and angles (°) for the compounds HL and 1.
the deprotonated amino groups (N(2) and N(5) in 1 corresponding
to N(2) in HL) and two nitrogen atoms of the benzothiazole
fragment (N(3) and N(6) in 1 corresponding to N(1) in HL)
of two deprotonated residues of 1,2-diamino-3-(2-benzothiazol-
yl)-4(5H)-ketopyrrole. The dihedral angle between the N(2)–
Zn(1)–N(3) and N(5)–Zn(1)–N(6) planes is 86.8°. The angles around
the central atom are distorted from an ideal tetrahedral configura-
tion (Table 2). The deprotonation of the ligand and its coordination
to Zn(II) leads to some changes in the geometrical parameters of Lꢀ
as compared to structure of HL. This includes an increase of the dis-
tance between the N(1) and N(2) atoms (2.866(3) Å in HL and
2.963(4), 2.968(3) Å in 1) and a strengthening of the SꢁꢁꢁO intramo-
lecular attractive interaction (the distances are 2.891(3) and
2.896(3) Å in 1 and 2.998(3) Å in HL). There is also a shortening
of the C(4)–C(6), C(16)–C(18), N(2)–C(5) and N(5)–C(17) bonds
and elongation of the N(3)–C(6), N(6)–C(18), C(4)–C(5) and
C(16)–C(17) bonds in the ligand of compound 1 as compared to HL.
The lengths of the Zn–N(amino) and Zn–N(benzothiazole) bonds are
1.944(2), 1.946(1) and 2.039(1), 2.043(1) Å, respectively. It should
be noted that the lengths of the Zn–N(amino) bonds correspond to
the formation of partly covalent bonds. Both six-membered metal-
locycles, Zn(1)–N(2)–C(5)–C(4)–C(6)–N(3) and Zn(1)–N(6)–C(18)–
C(16)–C(17)–N(5), adopt a twist-boat conformation (puckering
H-bond (number)
Symmetry
Hꢁ ꢁ ꢁA
D–Hꢁ ꢁ ꢁA
HL
N(2)–H(2B)ꢁꢁꢁN(1)
N(2)–H(2A)ꢁꢁꢁO(1)
N(4)–H(4A)ꢁꢁꢁO(1)
x, y, z
2.13(2)
2.15(2)
2.20(2)
2.86(2)
2.81(2)
2.74(2)
135.1(13)
166.8(14)
155.1(16)
127(1)
147(1)
174(1)
ꢀx + 1, y + 1/2, ꢀz + 1/2
x, ꢀy + 1/2, z ꢀ 1/2
1 ꢀ x, 1 ꢀ y, 1 ꢀ z
1 ꢀ x, 1 ꢀ y, 1 ꢀ z
x, 1/2 ꢀ y, 1/2 ꢀ z
N(4)–H(4B)ꢁꢁꢁC(1)
p
C(10)–H(10B)ꢁꢁꢁC(5)
p
C(2)–H(2C)ꢁꢁꢁN(1)
p
1
O(1 W)–H(102)ꢁꢁꢁO(1)
O(1 W)–H(106)ꢁꢁꢁO(2)
N(8)–H(8A)ꢁꢁꢁO(1 W)
N(8)–H(8B)ꢁꢁꢁO(1S)
N(7)–H(7A)ꢁꢁꢁN(8)
ꢀx, ꢀy + 1, ꢀz
ꢀx + 1, ꢀy + 2, ꢀz + 1
x, y, z
2.07(3)
2.08(4)
2.13(2)
2.13(2)
2.52(3)
2.32(2)
165(3)
177(4)
166(2)
152(2)
170(2)
145(2)
x, y, z
ꢀx + 1, ꢀy + 1, ꢀz
N(7)–H(7B)ꢁꢁꢁO(1 W)
x, y, z ꢀ 1
ular N–Hꢁꢁꢁ
p
and C–Hꢁꢁꢁ
p hydrogen bonds (Table 3). Neighboring
dimers of compound HL interact with each other by intermolecular
N–H???O, C–Hꢁꢁꢁ
p
hydrogen bonds and Sꢁꢁꢁ
p interactions. In the
last case, the distance between the S(1) and C(90) atoms
(3.424(2) Å) is considerably shorter than the van der Waals radii
sum (3.55 Å), and the value of the C(7)–S(1)ꢁꢁꢁC(90) angle
(154.59(4)°) meets the requirements for
r
-hole bonding. These
parameters [12] are S = 0.16, h = 59.3,
h = 89.3, = 25.9, respectively).
w = 19.9 and S = 0.09,
interactions finally form a two-dimensional supramolecular net-
work of HL parallel to the (1 0 1) crystallographic plane (Fig. 5).
The asymmetric part of the unit cell of the crystal structure of 1
contains one molecule of complex formed by zinc(II) and two an-
ionic ligands Lꢀ, one molecule of dmf and one molecule of water.
The zinc(II) is tetrahedrally coordinated by two nitrogen atoms of
w
The N(1) and N(4) atoms of the pyrrole ring have a pyramidal
configuration (the sum of the bond angles centred at the N(1)
and N(4) atoms are 355.6° and 358.4°, respectively). Deviations
of the N(1) and N(4) atoms from the mean plane of the remaining
atoms of the pyrrole rings are 0.14 and 0.08 Å, respectively, reflect-

1368
S.O. Nikitin et al. / Polyhedron 29 (2010) 1363–1369
Fig. 5. Two-dimensional supramolecular network of the compound HL along the (1 0 1) crystallographic direction.
Fig. 6. Fragment of the infinite chain of the compound [ZnL2]ꢁdmfꢁH2O (1).
ing a flattened envelope conformation of the heterocycles. The
amino groups N(7)H2 and N(8)H2 have an orthogonal orientation
relative to the heterocycles (the H(7A)–N(7)–N(1)–C(5) and
H(8A)–N(8)–N(4)–C(17) torsion angles are 137.71(2)° and
ꢀ122.11(1)°, respectively), which is usual for hydrazine fragments
and is similar to the conformation of HL.
C(18)–S(2)ꢁꢁꢁC(90) angle is 144.10(1)°). These interactions result in
the formation of a three-dimensional supramolecular network in
the crystal structure of complex 1.
4. Conclusions
In the crystals of compound 1, solvate dmf molecules are H-
bonded to N(8)H2 groups of neighboring ligands of 1. The role of
the solvate water molecules in the crystal architecture of 1 is more
significant. The latter are joined by O–HꢁꢁꢁO hydrogen bonds with
the oxygen atoms of carbonyl groups of two neighboring com-
plexes units. These interactions connect [ZnL2] complexes together
into infinite chains (Fig. 6). Neighboring chains are linked together
into a 2d sheet through hydrogen bonds between the oxygen
atoms of water molecules and the hydrogen atoms of N(8)H2
groups (Fig. 7). An additional attraction between the neighboring
sheets is provided by stacking of aromatic fragments of the ligands
The presented work describes the first example of the usage of
1,2-diamino-3-(2-benzothiazolyl)-4(5H)-ketopyrrole as a ligand
towards 3d-metal ions. To explore the coordination abilities of
HL, we have used acetate salts of 3d-metals, yielding three novel
mononuclear coordination compounds of zinc(II), cobalt(II) and
nickel(II). The coordination of HL by the metal ion in the deproto-
nated form is proposed, based on spectroscopic investigations,
mainly the 1H NMR spectrum of the zinc(II) complex 1. Analogous
IR spectra of the other obtained complexes (2 and 3) to 1, charac-
terized by 1H NMR-spectroscopy and X-ray analysis, suggests the
coordination of HL in the deprotonated form in the same mode
in these compounds.
(the distance between parallel fragments is 3.40 Å) and Sꢁꢁꢁ
p r-
hole interactions (the S(2)ꢁꢁꢁC(90) distance is 3.45(1) Å and the

S.O. Nikitin et al. / Polyhedron 29 (2010) 1363–1369
1369
Fig. 7. Fragment of the supramolecular sheet of the compound [ZnL2]ꢁdmfꢁH2O (1).
[2] J. Schubert, Sci. Am. 214 (1966) 40.
[3] B. Rosenberg, L. van Camp, Nature 222 (1969) 385.
Supplementary data
[4] B. Rosenberg, L. van Camp, Cancer Res. 30 (1970) 1799.
[5] H.H. Dubinina, Yu.M. Volovenko, Ukrainian Patent 22204, 2007.
[6] S.O. Nikitin, R.D. Lampeka, Yu.M. Volovenko, T.A. Volovnenko, V.V.
Dyakonenko, S.V. Shishkina, O.V. Shishkin, Polyhedron 27 (2008) 1161.
[7] S.O. Nikitin, R.D. Lampeka, S.V. Shishkina, O.V. Shishkin, Yu.M. Volovenko, T.A.
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[8] G.M. Sheldrick, Acta Crystallogr. A 64 (2008) 112.
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CCDC 736005 and 736004 contain the supplementary crystallo-
graphic data for HL and 1, respectively. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;
or e-mail: deposit@ccdc.cam.ac.uk.
[10] Yu.V. Zefirov, Crystallogr. Rep. 42 (1997) 865.
[11] P. Politzer, J.S. Murray, M.C. Concha, J. Mol. Model. 14 (2008) 659.
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