Synthesis, structural and optical properties of 1-alkyl-2-(2'-tosylaminophenyl)-5-nitrobenzimidazoles and their zinc(II) complexes

Article abstract of DOI:10.1016/j.molstruc.2015.07.056

A series of novel benzimidazole derivatives 1-alkyl-2-(2'-tosylaminophenyl)-5-nitrobenzimidazoles with common formulas HL (1-3) (R = C₂H₅ (1); R = n-C₃H₇ (2); R = n-C₄H₉(3)) and their monon

Full text of DOI:10.1016/j.molstruc.2015.07.056

Accepted Manuscript
Synthesis, structural and optical properties of 1-alkyl-2-(2’-tosylaminophenyl)-5-
nitrobenzimidazoles and their zinc(II) complexes
Anatolii S. Burlov, Yurii V. Koshchienko, Mikhail A. Kiskin, Stanislav A. Nikolaevskii,
Dmitrii A. Garnovskii, Anatolii S. Lermontov, Nadegda.I. Makarova, Anatolii V.
Metelitsa, Igor L. Eremenko
PII:
S0022-2860(15)30167-8
10.1016/j.molstruc.2015.07.056
MOLSTR 21711
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 11 June 2015
Revised Date: 27 July 2015
Accepted Date: 27 July 2015
Please cite this article as: A.S. Burlov, Y.V. Koshchienko, M.A. Kiskin, S.A. Nikolaevskii, D.A.
Garnovskii, A.S. Lermontov, N.I. Makarova, A.V. Metelitsa, I.L. Eremenko, Synthesis, structural and
optical properties of 1-alkyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazoles and their zinc(II) complexes,
Journal of Molecular Structure (2015), doi: 10.1016/j.molstruc.2015.07.056.
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ACCEPTED MANUSCRIPT
Synthesis, structural and optical properties of 1-alkyl-2-(2’-tosylaminophenyl)-5-
nitrobenzimidazoles and their zinc(II) complexes
a
a
b
b
Anatolii S. Burlov , Yurii V. Koshchienko , Mikhail A. Kiskin , Stanislav A. Nikolaevskii , Dmitrii A.
c,1
b
a
a
Garnovskii , Anatolii S. Lermontov , Nadegda.I. Makarova , Anatolii V. Metelitsa and Igor L.
b
Eremenko
a
Institute of Physical and Organic Chemistry of Southern Federal University, StachkiProsp. 194/2, 344090 Rostov-on-Don,
Russian Federation
b
N.S. Kurnakov Institute of General and Inorganic Chemistry of Russian Academy of Sciences, LeninskyProsp. 31, 119991
Moscow, Russian Federation
b
Southern Scientific Center of Russian Academy of Sciences, Chekhova str. 41, 344006 Rostov-on-Don, Russian Federation
ABSTRACT
A series of novel benzimidazole derivatives 1-alkyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazoles
with common formulae HL (1-3) (R = C H (1); R = n-C H (2); R = n-C H (3)) and their
2
5
3
7
4
9
mononuclear zinc(II) complexes ZnL (4-6) have been synthesized in a molar ratio Zn : HL = 1:2 in
2
methanol solutions. Formulation of 1-6 is based upon satisfactory C, H, N, S elemental analyses, IR
1
13
and H , C NMR spectroscopies, while the structures of 2, 3, 5, 6 were determined by X-ray single-
crystal diffraction. The optical properties of 1-6 were investigated.
Keywords: Benzimidazole, Zinc(II) complexes, N,N-chelating ligands, X-ray crystallography, optical
1
Corresponding author. Tel.: +7 8632434776
E-mail address: garn@ipoc.sfedu.ru (D.A.Garnovskii)
1

ACCEPTED MANUSCRIPT
1
. Introduction
Benzimidazole and its derivatives constitute one of the most intensely studied classes of
heterocycles due to their role in biological processes and their versatile application in both organic and
coordination chemistries [1–3]. Many natural or synthetic compounds comprising benzimidazole
moieties manifest different kinds of bioactivities, e.g. antibacterial [4, 5] or anticancer [6]. The
interaction of metal ions with benzimidazole containing ligands allows to design the new metal-
organic coordination compounds (frameworks) with various structural motifs and physical properties
useful in catalysis, molecular absorption, molecular magnetism, nonlinear optics etc [2, 7–9].
Among the benzimidazole containing coordination compounds lately more attention was given to
the zinc complexes of 2-(2’-hydroxyphenyl)benzimidazoles with N O ligand environment due to their
2
2
photoluminescence (PL) and electroluminescence properties(EL) and the possibility to use above
complexes as emissive and electron-transport layers in the Organic light emitting diodes OLED [10-
1
3], e.g. Zn(BIZ) (BIZ = 1-Phenyl-2-(2’-hydroxyphenyl)benzimidazole) showed pure blue emission
2
with a peak wavelength of around 450 nm and calculated Commission Internationale de l’Éclairage
CIE color coordinates of around (0.17, 0.16) [12]. Besides, the replacement of tosyl amino group in the
ortho-position of benzolic ring by hydroxy group allowed obtaining the zinc complexes with {ZnN4}
coordination core. Based on the 2-(2’-tosylaminophenyl)benzimidazoles derivatives the very efficient
2
+
2+
2+
2+
selective fluorescent metal-ions (Co , Ni , Cu , Zn ) sensors [14-16] were prepared.
Recently we have reported [17] the synthesis of 1-propyl-2-(2’-tosylaminophenyl)-5-
aminobenzimidazole and its structurally characterized binuclear zinc(II) complex as well as their PL
properties. Zinc complex having fluorescence in the solid phase is characterized by a broad band
4
3
00‒600 nm with a maximum at 458 nm. The Stokes shift estimated from the excitation spectrum was
-1
940 cm for the fluorescence of zinc complex.
2

ACCEPTED MANUSCRIPT
In this work we designed the novel N,N bidentate benzimidazole containing ligands 1-alkyl-2-
(2’-tosylaminophenyl)-5-nitrobenzimidazoles (1-3) by condensation of corresponding 5-nitro-N-alkyl-
o-phenylendiamines and 2-tosylaminobenzaldehyde and their zinc(II) complexes (4-6) in order to
investigate the structural and optical features of these compounds.
2
. Experimental
2
.1.
Materials required and general methods
All starting materials and solvents were of reagent quality and were used as received. 2-alkylamino-5-
nitroanilines and 2-tosylaminobenzaldehyde were prepared according to the published methods [18-
20]. C, H, N, S elemental analyses were carried out on a «Carlo Erba Instruments TCM 480». Melting
points were determined on a Kofler table. The IR spectra of the ligands and complexes were recorded
–1
in the range 400-4000 cm by means of a Varian Excalibur 3100 FT-IR spectrometer in KBr pellets.
1
H NMR spectra were measured on a Varian Unity 300 spectrometer at ambient temperature in
2
13
DMSO-d with the signal of residual H of the solvent as the internal reference. С NMR spectra (62.9
6
MHz) were registered on a Bruker DPX-250 spectrometer at ambient temperature in DMSO-d with
6
the TMS as internal standard.
2
.2.
Ligand synthesis
Ts
HN
H
O N
NH2
N
O N
2
2
Ts
N
+
C O
H
N
R
N R
H
R = C H (1), C H (2), C H (3);
2
5
3
7
4
9
Ts = SO C H CH -p
2
6
4
3
3

ACCEPTED MANUSCRIPT
Scheme 1. Synthesis of the ligands (1-3)
A mixture of copper acetate monohydrate (12 mmol, 2.4 g) in 15 ml of H O, 2-
2
tosylaminobenzaldehyde (6 mmol, 1.65 g) in 6 ml of glacial acetic acid and corresponding 2-
alkylamino-5-nitroaniline (6 mmol) in 15 ml of 50 % of acetic acid was refluxed (Scheme 1). In ca. 1
h reaction mixture was cooled, the precipitate was filtered off, washed with water and dried in air. A
copper salt was suspended in 10 ml of glacial acetic acid and treated with solution of sodium
thiosulfate (12 mmol, 3.0 g) in 5 ml of water. In ca. 30 min the precipitate was collected by filtration,
washed with water and dried in air. The precipitate was dissolved in chloroform and passed through
the layer of Al O . After the evaporation to dryness and crystallization from DMF the precipitates of
2
3
ligands 1-3 were obtained.
-Ethyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazole (1)
Yield: 59 %, M.p. = 202 – 203 °С. Anal. Calc. for C H N O S: C, 60.54; H, 4.62; N, 12.84; S, 7.34.
1
22
20
4
4
-1
Found: C, 60.44; H, 4.70; N, 12.92; S, 7.28 %. IR (KBr, cm ): 3249 s ν(N-H), 1619 m-w, 1598 m-w
1
and 1579 m-w ν(C=N and C=C of benzimidazole ring), 1332 vs ν (SO ), 1164 vs ν (SO ). H NMR
as
2
s
2
spectrum in DMSO-d , δ: 1.23 (t, 3 H, CH -CH , J = 7.2 Hz), 2.27 (s, 3 H, C -CH ), 4.01 (q, 2 H,
6
2
3
Ar
3
CH -CH , J = 7.2 Hz), 7.12 (d, 2 H, C -H, J = 8.1 Hz), 7.35-7.54 (m, 6 H, C -H), 7.90 (d, 1 H, C -H,
2
3
Ar
Ar
Ar
J = 9.0 Hz), 8.24 (dd, 1 H, C -H, J = 8.9, J = 1.3 Hz), 8.61 (d, 1H, C -H, J = 1.5 Hz), 10.09 (s, 1H,
Ar
Ar
1
3
NH). С NMR (62,9 MHz, DMSO-d , TMS): δ 153.83, 143.27, 143.02, 141.47, 139.16, 136.45,
6
1
1
1
36.21, 131.38, 130.64, 129.40, 126.38, 125.32, 123.86, 122.14, 118.12, 115.26, 111.39, 39.86, 20.90,
4.62.
-Propyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazole (2)
Yield: 60 %. M.p. = 185–186 °С. Anal. Calc. for C H N O S: C, 61.32; H, 4.92; N, 12.44; S, 7.11.
2
3
22
4
4
-1
Found: C, 61.23; H, 5.01; N, 12.51; S, 7.24 %. IR (KBr, cm ): 3247 s ν(N-H), 1618 m-w, 1595 m-w
1
and 1577 m-w ν(C=N and C=C of benzimidazole ring), 1334 vs ν (SO ), 1166 vs ν (SO ). H NMR
as
2
s
2
4

ACCEPTED MANUSCRIPT
spectrum in DMSO-d , δ: 0.70 (t, 3 H, CH CH CH , J = 7.3 Hz), 1.56 (q, 2 H, CH CH CH , J = 7.4
6
2
2
3
2
2
3
Hz), 2.25 (s, 3 H, C -CH ), 3.97 (t, 2 H, CH CH CH , J = 7.5 Hz), 7.17 (d, 2H, C –H, J = 8.1 Hz),
Ar
3
2
2
3
Ar
7
8
1
1
1
.32-7.55 (m, 6 H, C -H), 7.91 (d, 1 H, C -H, J = 9.0 Hz), 8.23 (dd, 1 H, C -H, J = 8.9, J = 2.2 Hz),
Ar Ar Ar
1
3
.59 (d, 1H, C -H, J = 2.2 Hz), 10.07 (s, 1H, NH). С NMR (62,9 MHz, DMSO-d , TMS): δ 154.15,
Ar
6
43.33, 142.95, 141.50, 139.61, 136.68, 136.17, 131.40, 130.96, 129.50, 126.46, 125.13, 123.15,
22.13, 118.07, 115.27, 111.62, 46.22, 22.41, 20.92, 10.92.
-Butyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazole (3)
Yield: 67 %. M.p. = 177–178 °С. Anal. Calc. for C H N O S: C, 62.05; H, 5.21; N, 12.06; S, 6.90.
2
4
24
4
4
-1
Found: C, 62.00; H, 5.29; N, 12.13; S, 7.04 %. IR (KBr, cm ): 3250 s ν(N-H), 1617 m-w, 1594 m-w
1
and 1577 m-w ν(C=N and C=C of benzimidazole ring), 1334 vs ν (SO ), 1165 vs ν (SO ). H NMR
as
2
s
2
spectrum in DMSO-d , δ: 0.81 (t, 3 H, CH CH CH CH , J = 7.3 Hz), 1.20 (q, 2 H, CH CH CH CH , J
6
2
2
2
3
2
2
2
3
=
7.6 Hz), 1.60 (t, 2 H, CH CH CH CH , J = 7.5), 3.99 (t, 2 H, CH CH CH CH , J = 7.7 Hz), 7.09 (d,
2 2 2 3 2 2 2 3
2
H, C –H, J = 8.1 Hz), 7.26 (m, 1Н, C –H),7.43-7.48 (m, 5 H, C -H), 7.76 (d, 1 H, C -H, J = 8.9
Ar Ar Ar Ar
1
3
Hz), 8.21 (dd, 1 H, C -H, J = 9.0, J = 2.1 Hz), 8.59 (s, 1H, C -H), 10.04 (s, 1H, NH). С NMR (62,9
Ar
Ar
6
MHz, DMSO-d , TMS): δ 154.16, 143.32, 142.95, 141.56, 139.55, 136.74, 136.18, 131.42, 131.02,
29.51, 126.47, 125.08, 123.07, 122.07, 118.09, 115.29, 111.57, 44.35, 30.91, 20.93, 19.20, 13.16.
1
2
.3.
Synthesis of complexes
Zn/2
N
Ts
Ts
HN
N
N
O N
O N
2
2
.
+
Zn(CH COO) 2H O
3 2 2
N
R
N
R
R = C H (4), C H (5), C H (6)
2
5
3
7
4
9
Scheme 2. Synthesis of the complexes (4-6)
5

ACCEPTED MANUSCRIPT
A hot solution of zinc acetate dihydrate (0.5 mmol, 110 mg) in 5 ml of methanol was added to a hot
solution containing 1 mmol of corresponding ligand in 50 ml of methanol (Scheme 2). In ca. 2 h. of
refluxing the reaction mixtures were cooled, the precipitates were filtered off and washed many times
with methanol and then crystallized from a methanol - chloroform 1:1.
Bis-[1-ethyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazolato]zinc(II) (4)
Yield: 67 %. M.p. > 250 °С.Anal. Calc. for C H N O S Zn: C, 56.44; H, 4.09; N, 11.97; S, 6.84.
4
4
38
8
8 2
-1
Found: C, 56.39; H, 4.15; N, 12.05; S, 7.01 %. IR (KBr, cm ): 1617 vw, 1597 m-w and 1561 m-w
1
ν(C=N and C=C of benzimidazole ring), 1239 vs ν (SO ), 1144 vs ν (SO ). H NMR spectrum in
as
2
s
2
DMSO-d , δ: 1.31 (t, 3 H, CH CH , J = 6.6 Hz), 2.20 (s, 3 H, C –H), 4.44 (br s, 2 H, CH ), 7.00-7.79
6
2
3
Ar
2
1
3
(
m, 9 H, C -H), 7.94-8.03 (m, 2H, C -H). С NMR (62,9 MHz, DMSO-d , TMS): δ 156.49, 145.17,
Ar Ar 6
1
1
43.06, 141.45, 140.14, 138.09, 137.63, 132.27, 130.76, 129.09, 126.13, 123.39, 121.62, 118.78,
17.05, 112.72, 112.52, 41.92, 20.78, 14.27.
Bis-[1-propyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazolato]zinc(II) (5)
Yield: 64 %. M.p. > 250 °С.Anal. Calc. for C H N O S Zn: C, 57.29; H, 4.39; N, 11.62; S, 6.65.
4
6
42
8
8 2
-1
Found: C, 57.19; H, 4.48; N, 11.73; S, 6.92 %. IR (KBr, cm ): 1617 vw, 1597 m-w and 1566 m-w
1
ν(C=N and C=C of benzimidazole ring), 1236 vs ν (SO ), 1135 vs ν (SO ). H NMR spectrum in
as
2
s
2
DMSO-d , δ: 0.65 (t, 3 H, CH CH CH3, J = 7.3 Hz), 1.59 (q, 2 H, CH CH CH3 J = 7.1 Hz), 2.21 (s, 3
6
2
2
2
2
H, C -H ), 4.49 (br s, 2 H, CH CH CH3), 7.02 (d, 2 H, C -H, J = 7.8 Hz), 7.15 (br s, 2 H, C -H ),
Ar
2
2
Ar
Ar
1
3
7
.47 (d, 3 H, C -H , J = 7.5 Hz), 7.87 (br s, 1 H, C -H ), 8.06 (q, 2 H, C -H, J = 8.2 Hz). С NMR
Ar Ar Ar
(
62,9 MHz, DMSO-d , TMS): δ 157.08, 145.07, 143.08, 141.44, 140.09, 138.36, 137.48, 132.31,
6
131.01, 129.06, 126.20, 122.66, 121.28, 118.81, 116.77, 113.15, 112.77, 48.11, 21.98, 20.77, 10.65.
Bis-[1-butyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazolato]zinc(II) (6)
Yield: 68 %. M.p. > 250 °С.Anal. Calc. for C H N O S Zn: C, 58.09; H, 4.67; N, 11.29; S, 6.23.
4
8
46
8
8 2
-1
Found: C, 58.02; H, 4.72; N, 11.36; S, 6.17 %. IR (KBr, cm ): 1620 vw, 1597 m-w and 1567 m-w
1
ν(C=N and C=C of benzimidazole ring), 1236 vs ν (SO ), 1138 vs ν (SO ). H NMR spectrum in
as
2
s
2
6

ACCEPTED MANUSCRIPT
DMSO-d , δ: 0.66 (t, 3 H, CH CH CH CH3, J = 7.2 Hz), 1.10 (q, 2 H, CH CH CH CH J = 7.1 Hz),
6
2
2
2
2
2
2
3
1
.57 (br s, 2 H, CH CH CH CH3), 2.21 (s, 3 H, C -H ), 4.53 (br s, 2 H, CH CH CH CH3), 7.02 (d, 2
2 2 2 Ar 2 2 2
H, C -H, J = 7.5 Hz), 7.14 (br s, 2 H, C -H ), 7.49 (d, 3 H, C -H), 7.72 (br s, 1 H, C -H ), 8.01-8.03
Ar
Ar
Ar
Ar
1
3
(
m, 2 H, C -H). С NMR (62,9 MHz, DMSO-d , TMS): δ 157.37, 145.50, 143.53, 141.89, 140.52,
Ar 6
1
4
38.69, 137.88, 132.78, 131.44, 129.52, 126.69, 122.96, 121.65, 119.26, 116.99, 113.56, 113.05,
6.51, 30.88, 21.22, 19.41, 13.39.
2
.4.
Crystal structure determination
The X-ray data sets for ligands and complexes 2, 3, 5 and 6 were collected on a Bruker APEX II
diffractometer equipped with a CCD camera and a graphite-monochromated MoK radiation source (λ
α
=
0.71073 Å) [21]. Semiempirical absorption correction for all compounds was applied [22]. The
structures was solved by direct methods and using Fourier techniques and were refined by the full-
2
matrix least squares against F with anisotropic thermal parameters for all non-hydrogen atoms. The
hydrogen atoms of the carbon-containing ligands were positioned geometrically and refined using the
riding model. All calculations were carried out with the use of the SHELX97 program package [23].
Disordered solvent molecules in 6, which could not be localised, were removed by SQUEEZE [24].
The crystallographic parameters and the refinement statistics are given in Table 1.
Table 1
2
.5.
UV-vis spectra
Electronic absorption spectra were recorded on a Varian Cary 100 spectrophotometer. Fluorescence
measurements were performed on a Varian Cary Eclipse spectrofluorimeter. Spectral grade DMSO
from Sigma-Aldrich was used for the preparation of solutions.
7

ACCEPTED MANUSCRIPT
3
. Results and Discussion
3
.1.
Ligand tautomerism
According to the literature data [14, 18] the enamine tautomeric E form of ligand 1-3 is more
stable in the solid state comparing with sulfonimino form I (Scheme 3). This fact was
unambiguosly confirmed by the X-ray diffraction analisis data for the ligands 1 [18], 2 and 3. Thus,
the distribution of double N(3)–C(13), N(2)–C(14) (1.322(3)Å и 1.319(2)Å) and single N(2)–
C(13), N(3)–C(14) (1.380(3)Å и 1.380(2)Å) bonds in 2 and 3 is in a good agreement with earlier
structurally characterized 2-(2’-tosylamino)benzimidazoles (R = Et(1), Ph) that confirms the
realization of enamine tautomeric E form of 2 and 3. Moreover, E form is stabilized by the
intramolecular H-bond between nitrogen atom N(3) of benzimidazole moiety and hydrogen atom
o
of tosylated amino group: N(1)…N(3) 2.804(3), N(3)…H 2.08 Å, N(1)–H–N(3) 139.7(2) for 2,
o
N(1)…N(2) 2.809(2), N(3)…H 2.17 Å, N(1)–H–N(3) 134.0(2) for 3 (Figs. 1 and 2).
Ts
Ts
H
H
N
N
N
N
N
R
N
R
E (enamine form)
I (sulfonimino form)
Scheme 3. Tautomeric forms of HL
3
.2.
Spectroscopic properties
1
6
H NMR spectra (run in DMSO-d ) of ligands 1-3 display the resonance lines in the field
1
0.04–10.07 ppm assigned to the tosylated amino protons, whereas IR spectra of “free” ligands 1-3
8

ACCEPTED MANUSCRIPT
–
1
exhibit the stretching vibration bands in the range 3140–3150 cm attributable to ν(N–H) of
tosylamino group. The IR spectra of the complexes 4-6 in comparison with the IR spectra of
uncoordinated compounds (1-3) do not exhibit the stretching vibration bands in the range 3140–
-1
3
150 cm attributable to ν(N–H) of the tosylated amino group and show a frequency shift (98–30
–
1
1
cm ) of stretching valence bands ν and ν of sulfo group. The H NMR spectra of the Zn(II)
as
s
6
complexes 4-6 in (run in dmso-d ) did not display any resonance assigned to the tosylated amino
proton. Thus, both NMR and IR data favor a {ZnN4} coordination core for the zinc(II) complexes
4
-6 with participation of one deprotonated amide nitrogen atom and the endocyclic nitrogen atom
of benzimidazole ring of each ligand.
3.3 Structural description of 2, 3, 5,and 6
The crystal structures of the ligands 2 and 3 (Figs. 1 and 2) are similar to the earlier described
for 1 [18]. The phenyl rings C(8)–C(12)C(23) (in 2) and C(8)–C(13) (in 3) is not coplanar to
benzimidazole ring and the torsion angles N(3)C(13)C(23)C(8) and N(2)C(14)C(13)C(8) are 39.1
o
and 38.7 for 2 and 3, respectively.
Fig. 1
Fig. 2
The mutual disposition of the benzimidazole and phenyl (C(1)–C(6)) rings within the 3 allowed
assuming the presence of π-π stacking with the centroid distance 3.577 Å and the dihedral angle 7.3°
(Fig. 2). This type of intramolecular interaction was not observed for 2.
X-Ray diffraction analysis revealed that the coordination environment of the central atom in
compounds 5 and 6 is formed by four nitrogen atoms of two monodeprotonated chelating ligands
9

ACCEPTED MANUSCRIPT
(Figs. 3 and 4). In the crystal of 5 the molecule of complex stands in the local position, while in 6 on
the C axis. In both complexes the zinc atom is arrounded by four nitrogen atoms in distorted
2
tetrahedral environment: (Zn(1)–N(2) 1.965(2), Zn(1)–N(5) 1.970(2), Zn(1)–N(1) 2.022(2), Zn(1)–
N(6) 2.036(2) Å for 5 and Zn(1)–N(1) 2.0060(16), Zn(1)–N(2) 2.0459(15) Å for 6. Both deprotonated
ligands form the non-planar six-membered metallocycles where С(8), С(13) and С(14) atoms deviate
from the average Zn(1)N(1)N(2) plane by 0.57, 0.59 and 0.06 Å, whilst С(31), С(36) and С(37) atoms
deviate by 0.89, 0.98 and 0.17 Å for 5. In the 6 structure the same features were observed, i.e. the C(8),
C(13) and C(14) atoms deviate from the plane Zn(1)N(1)N(2) by 0.65, 0.75 and 0.11 Å. The mutual
disposition of benzimidazole and phenyl rings (C(8)–C(13) and C(31)–C(36) in 5, C(8)–C(13) and
o
C(31)–C(36) in 6 ) as well as in ligands are not coplanar (the dihedral angles are equal 43.4 and 43.6
o
for 5 and 37.5 for 6). Selected bond lenghts and bond angles are summerised in Table 2.
Fig. 3
Fig. 4
Table 2
In the crystal structure of 6, molecular packing is stabilized by weak π-π stacking
intramolecular interactions: distances between centers of symmentrical C(15)–C(20) benzene rings
(symmentry code: – x, 1 – y, – z)) is 3.967 Å (Fig. 5).
Fig. 5
3.4 UV-vis and luminescent spectra
1
0

ACCEPTED MANUSCRIPT
Spectral absorption and PL properties of the ligands 1-3 with different alkyl substituents (R =
Et, Pr, Bu) at N -atom of benzimidazole moiety as well as their zinc(II) complexes 4-6 were studied at
1
ambient temperature in DMSO solutions. These results are presented in the table 3. UV-vis absorption
spectra of 1-6 are depicted on the Fig. 6.
Table 3
Fig. 6
The UV-vis absorption spectra of 1-alkyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazoles 1-3
(table 3, Fig. 6) in DMSO exhibit almost similar long-wave absorption bands with maxima at 326 nm
-1
-1
for 1, 2 and 327 nm for 3 and molar extinction coefficients 13850, 14480 и 13450 M ·cm ,
respectively. In comparison with ligands 1-3 the complexes 4-6 demonstrate practically identical
optical properties. In the UV-vis spectra of complexes 4-6 the low hypsochromic shift (2-3 nm) with
the maxima of long wave absorption bands till λmax = 324 nm (4-6) and simultaneous increasing of
-1
-1
their intensities were observed (ε = 27600 – 28500 M ·cm ) (table 3, fig. 6). Double increasing of
intensity of absorption for 4-6 comparing with 1-3 confirms the ZnL composition for complexes 4-6.
2
Regardless the variation of alkyl substituents the solutions of 1-6 in DMSO did not show any
fluorescence in contrast with previously published data [17] on the PL properties of 1-propyl-2-(2’-
tosylaminophenyl)-5-aminobenzimidazole and its zinc(II) complex characterized with high value of
quantum yield of fluorescence.
Conclusion
Herein we have reported three novel complexes with {ZnN4} coordination core based on 1-
alkyl-2-(2’-tosylaminophenyl)-5-nitrobenzimidazoles. From single X-ray analysis it has been
established that complexes 4, 5 are mononuclear species whereas molecules of 6 are bound in
1
1

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supramolecular chains in crystal due to weak π-π stacking interactions between benzimidazole rings.
The introduction of withdrawing nitro group in the fifth position of benzimidazole moiety of ligands 1-
3
causes the absence of fluorescence in the Zn(II) complexes 4-6 in contrast with the structural
analogous Zn(II) compounds comprising donor amino group [17].
Acknowledgements
This research was supported by The Ministry of education and science of Russian Federation in the
framework of the State Assignment for Research, project № 1895.
X-ray diffraction studies were performed at the Centre of Shared Equipment of IGIC RAS.
IR, NMR and UV-vis spectra were obtained using facilities of the “Molecular Spectroscopy” Multi-
Center of the Southern Federal University.
1
3
NMR spectra were recorded on a Bruker DPX-250 (62.9 MHz for C) spectrometer at the Scientific
and Educational Laboratory of Resonance Spectroscopy, Department of Natural and High Molecular
Compounds Chemistry of Southern Federal University.
References
1
2
. J.B. Wright, Chem. Rev. 48 (1951) 397.
. M. Haga, In Comprehensive Coordination Chemistry II, (Eds. J.A. McCleverty, T.J. Meyer),
Elsevier, Amsterdam 1 (2004) 125.
3
4
5
. N.Xi.Q. Huang, L. Liu, in Comprehensive Heterocyclic Chemistry III, (Eds. A.R. Katritzky,
C.A. Ramsden, E.F.V. Scriven, R.J.K. Taylor), Elsevier, Amsterdam, 4 (2008) 143.
. A. Khalafi-Nezhad, M.N. Soltani Rad, H. Mohabatkar, Z. Asrari, B. Hemmateenejad, Bioorg.
Med. Chem. 13 (2005) 1931.
. R.V. Shingalapur, K.M. Hosamani, R.S. Keri, Eur. J. Med. Chem. 44 (2009) 4244.
1
2

ACCEPTED MANUSCRIPT
6
7
. A.W. White, N.J. Curtin, B.W. Eastman, B.T. Golding, Z. Hostomsky, S. Kyle, J. Li, K.A.
Maegley, D.J. Skalitzky, S.E. Webber, X.-H. Yu, R.J. Griffin, Bioorg. Med. Chem. Lett. 14
(2004) 2433.
. A.D. Garnovskii, A.P. Sadimenko, I.S. Vasilchenko, D.A. Garnovskii, E.V. Sennikova, V.I.
Minkin, Adv. Heterocycl. Chem. 97 (2009) 291.
8. H. Wu, T. Sun, K. Li, Y. Xu, R. Yun, Q. Sun, Z. Anorg. Allg. Chem. 635 (2009) 146.
9. A.D. Garnovskii, A.P. Sadimenko, Adv. Heterocycl. Chem. 72 (1998) 1.
10. Y.P. Tong, S.L. Zheng, X.M. Chen, Eur. J. Inorg. Chem. (2005) 3734.
11. H. Xu, Z.F. Xu, Yu. Z. Yue, P.F. Yan, B. Wang, L.W. Jia, G.M. Li, W.B. Sun, J.W. Zhang A,
J. Phys. Chem. C. 112 (2008) 15517.
1
1
1
1
1
1
2. S.Tokito, K. Noda, H. Tanaka, Y. Taga, T. Tsutsui // Synth. Met. 111-112 (2000) 393.
3. Y.P. Tong, S.L. Zheng, X.M., X.-M. Chen, J. Mol Struct. 826 (2007) 104.
4. C.J. Fahrni, M.M. Henary, D.J. Van Derveer, J. Phys. Chem. A. 2002 (106) 7655.
5. D. Martin, M. Rouffet, S.M. Cohen, Inorg. Chem. 2010 (49) 10226.
6. M.M. Henary, Y. Wu, C.J. Fahrni, Chem. Eur. J. 2004 (10) 3015.
7. S.A. Nikolaevskii, Yu.V. Koshchienko, A.V. Chernyshev, A.S. Burlov, A.S. Cheprasov, G.G.
Aleksandrov, M.A. Kiskin, A.V. Metelitsa, Russian J. Coord. Chem. 2014 (40) 468.
8. K.A. Lyssenko, A.O. Borissova, A.S. Burlov, I.S. Vasilchenko, A.D. Garnovskii,V.I. Minkin,
M.Yu. Antipin, Mendeleev Commun. 17 (2007) 164.
1
1
9. A.S. Burlov, V.N. Ikorskii, S.A. Nikolaevskii, Yu.V. Koshchienko, V.G. Vlasenko, Ya.V.
Zubavichus, A.I. Uraev, I.S. Vasilchenko, D.A. Garnovskii, G.S. Borodkin, A.D. Garnovskii,
Rus. J. Inorg. Chem. 53 (2008) 1566.
2
2
0. N.I. Chernova, Yu.S. Ryabokobylko, V.G. Brudz’, B.M. Bolotin, Zh. Org. Khim. 7 (1971)
1
687.
1. Bruker APEX2 Software Package, Bruker AXS, Madison, 2005.
1
3

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2
2. G.M. Sheldrick, SADABS, Program for Scanning and Correction of Area Detector Data,
University of Götinngen, Götinngen, Germany, 2004.
3. G.M. Sheldrick, ActaCryst. A. 64 (2008) 112.
2
2
4. A. L. Spek, PLATON, A Multipurpose Crystallographic Tool, Utrecht University, Utrecht,
Netherlands, 2005.
1
4

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Table 1
Experimental data for crystallographic analysis of 2, 3, 5 and 6
Complex /
2
3
5
6
Parameter
formula
C H N O S C H N O S C H42.5C N O S Zn C H N O S Zn
23
22
4
4
24 24
464.53
173(2)
4
4
46.5
l1.5
8
8
2
48 46
992.42
173(2)
8
8 2
–
1
fw (g·mol )
T (K)
450.51
150(2)
0.71073
1024.05
173(2)
Wavelength
0.71073
0.71073
0.71073
(
Å)
crystal system Monoclinic
Triclinic
P-1
Monoclinic
Monoclinic
C2/c
28.514(4)
11.7046(18)
20.003(3)
90
123.380(2)
90
5574.6(15)
4
space group
a (Å)
C2/c
P2 /n
1
25.555(10)
10.423(4)
18.234(8)
90
9.740(3)
9.5399(14)
26.241(4)
19.084(3)
90
93.737(2)
90
4767.3(12)
4
b (Å)
10.225(3)
11.321(3)
95.981(4)
100.051(4)
94.667(4)
1098.5(5)
2
c (Å)
α
β
(deg)
(deg)
118.692(7)
90
4260(3)
8
γ (deg)
3
V (Å )
Z
-
3
1
.405
1.404
0.188
1.427
1.182
Dcalc (g·cm )
-
1
ꢀ
(mm )
0.191
0.748
36315/10140
0.568
20370/5727
total no. of
16910 / 4652 9027 / 4461
reflns/unique
R
min/max
0.0624
0.9943
0
27.00
1.013
0.0497
0.0239
/ 0.7464
0.6358
26.50
0.0531
/ 0.9635 / 0.7539
0.0460
0.8480 / 0.7840
int
T
.9774
θ
(deg)
26.79
1.041
0.0432
0.1075
0.0670
0.1240
26.46
0.931
0.0340
0.0831
0.0452
0.0858
max
GOF
1.058
R (I >2
σ
(I))
0.0406
0.1053
0.0504
0.1110
1
wR (I >2σ(I)) 0.1087
2
R (all data)
0.0879
0.1214
1
wR (all data)
2

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Table 2
Selected bond lengths (Å) and angles (deg.) for 2, 3, 5, and 6
2
S(1)–
1
.639(2)
.427(3)
O(1)–S(1)–O(2) 1.222(2)
N(1)–S(1)–C(1) 119.87(10)
N(1)
N(1)–
C(8)
1
S(1)–
O(1)
S(1)–
O(2)
N(2)–
C(17)
N(3)–
C(13)
N(3)–
C(22)
O(3)–
N(4)
1
1
1
1
1
1
.4279(17) C(8)–N(1)–S(1) 106.19(10)
C(17)–N(2)–
.4314(16)
.376(3)
.322(3)
.396(3)
.222(2)
119.19(15)
106.37(17)
C(13)
C(22)–N(3)–
C(13)
O(3)–N(4)–O(4) 105.35(18)
3
S(1)– 1.6409(15) O(1)S(1)O(2)
N(1)
120.74(10)
106.10(7)
119.58(12)
N(1)– 1.427(2)
C(8)
C(1)S(1)N(1)
S(1)– 1.4237(15) S(1)N(1)C(8)
O(1)
S(1)– 1.4303(16) C(14)N(2)C(15) 105.19(13)
O(2)
N(2)– 1.3828(19) C(14)N(3)C(20) 106.17(12)
C(15)
N(3)– 1.380(2)
O(3)N(4)O(4)
123.18(15)
C(14)
N(3)– 1.373(2)
C(20)
O(3)– 1.2272(19)
N(4)
5
Zn(1)– 2.022(2)
N(1)
Zn(1)– 1.965(2)
N(2)
Zn(1)– 1.970(2)
N(5)
Zn(1)– 2.036(2)
N(6)
N(2)Zn(1)N(1)
N(2)Zn(1)N(5)
N(2)Zn(1)N(6)
N(5)Zn(1)N(6)
94.31(9)
125.49(9)
119.71(9)
92.44(9)
N(5)Zn(1) N(1) 122.19(9)
N(1)Zn(1)N(6) 102.43(8)
6
Zn(1)– 2.0060(15) N(1)Zn(1)N(1A) 142.55(9)
N(1)

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Zn(1)– 2.0459(15) N(1)Zn(1)N(2)
91.35(6)
N(2)
Zn(1)– 2.0060(16) N(2)Zn(1)N(2A) 123.59(9)
N(1A)
Zn(1)– 2.0460(15) N(1)Zn(1)N(2A) 106.25(6)
N(2A)

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Table 3.
Absorption spectral data for compounds 1-6 in DMSO at 293 K
Ligands
Complexes ZnL2
Compound R Absorption
Compound Absorption
3
-1
-1
3
-1
-1
λmax (нм)/ ε (10 M ·cm )
λmax (нм)/ε (10 M ·cm )
1
2
3
Et 326 (13.85)
4
5
6
324 (27.60)
Pr 326 (14.48)
Bu 327 (13.45)
324 (28.50)
324 (27.98)

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Fig. 1. Molecular structure of 2 (the hydrogen atoms are not shown; thermal ellipsoids are drawn
at the 30% probability level).
Fig. 2. Molecular structure of 3 (the hydrogen atoms are not shown; thermal ellipsoids are drawn
at the 30% probability level).

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Fig. 3. Molecular structure of 5 (the hydrogen atoms are not shown; thermal ellipsoids are drawn
at the 30% probability level).
Fig. 4. Molecular structure of 6 (the hydrogen atoms are not shown; thermal ellipsoids are drawn
at the 30% probability level).

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Fig. 5. Packing fragment for compound 6 (the hydrogen atoms are not shown).
-5
-
Fig. 6. UV-vis absorption spectra (1-6) of compounds 1-6 in DMSO solutions (С = 4·10 mol L
1
,
l = 1 cm, T = 293 K).

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HIGHLIGHTS
•
•
•
N, N bidentate Benzimidazole containing ligands and their Zn(II) complexes.
X-ray crystallographic analysis of ligands and Zn(II) complexes.
Optical behavior of mononuclear Zn(II) compounds.