Synthesis and crystal structure of a 3-D netlike supramolecular cobalt picrate complex with 2, 6-bis(benzimidazol-2-yl)pyridine

Article abstract of DOI:10.1080/15533174.2013.771663

A novel complex of cobalt picrate with 2, 6-bis(benzimidazol-2-yl)pyridine (L), has been prepared and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. The complex crystallizes in the monoclinic system, space group c2/c with a = 21.8756(6) A, b = 12.2995(3) A, c = 27.4827(7) A, β = 95.6060(10)°, and Z = 4. The structure was refined to the final R₁ = 0.0708. The complex units are linked by π-π interactions and hydrogen bonds to give infinite two-dimensional (2-D) supramolecular layers, which are further linked by the intermolecular hydrogen bonds to form a three-dimensional (3-D) netlike supramolecule. Copyright Taylor & Francis Group, LLC.

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Synthesis and Crystal Structure of a 3-D Netlike
Supramolecular Cobalt Picrate Complex With 2, 6-
bis(benzimidazol-2-yl)pyridine
Zhen-Zhong Yan a , Na Hou a & Hua-Ding Liang a
a Department of Pharmaceutics and Chemical Engineering , Taizhou University , Linhai , P. R.
China
Accepted author version posted online: 20 Sep 2013.Published online: 06 Nov 2013.
To cite this article: Zhen-Zhong Yan , Na Hou & Hua-Ding Liang (2014) Synthesis and Crystal Structure of a 3-D Netlike
Supramolecular Cobalt Picrate Complex With 2, 6-bis(benzimidazol-2-yl)pyridine, Synthesis and Reactivity in Inorganic, Metal-
Organic, and Nano-Metal Chemistry, 44:3, 344-347, DOI: 10.1080/15533174.2013.771663
To link to this article: http://dx.doi.org/10.1080/15533174.2013.771663
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 44:344–347, 2014
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.771663
Synthesis and Crystal Structure of a 3-D Netlike
Supramolecular Cobalt Picrate Complex With 2,
6-bis(benzimidazol-2-yl)pyridine
Zhen-Zhong Yan, Na Hou, and Hua-Ding Liang
Department of Pharmaceutics and Chemical Engineering, Taizhou University, Linhai, P. R. China
EXPERIMENTAL
A novel complex of cobalt picrate with 2, 6-bis(benzimidazol-2-
Materials and Physical Measurements
yl)pyridine (L), has been prepared and characterized by elemental
All reagents and solvents were purchased commercially
analysis, IR spectroscopy, and single-crystal X-ray diffraction. The
complex crystallizes in the monoclinic system, space group c2/c
with a = 21.8756(6) Å, b = 12.2995(3) Å, c = 27.4827(7) Å, β =
95.6060(10)◦, and Z = 4. The structure was refined to the final R1 =
0.0708. The complex units are linked by π-π interactions and hy-
drogen bonds to give infinite two-dimensional (2-D) supramolecu-
lar layers, which are further linked by the intermolecular hydrogen
bonds to form a three-dimensional (3-D) netlike supramolecule.
and used without further purification unless otherwise noted.
Co(Pic)2 was prepared by the reaction of cobalt carbonate and
picric in the hot water. All reagents used were of analytical grade
and used without further purification.
IR spectra were recorded on a Nicolet 360 FT-IR instru-
ment using KBr discs in the 4000-400 cm–1 region. The crystal
structure was determined by a Bruker APEX CCD area-detector
diffractometer.
Keywords 2, 6-bis(benzimidazol-2-yl)pyridine, crystal structure,
cobalt picrate complex, π-π interactions
Preparation of the Ligand L
The ligand 2,6-bis(benzimidazol-2-yl)pyridine was prepared
by the reaction of pyridine-2,6-dicarboxylic acid and o-
phenylenediamine in syrupy phosphoric acid (40 mL) at ca.
230◦ for 4 h as described previously,[11] yield 55%, m.p. >250◦.
IR (cm–1) in KBr pellet: ν(C = N) 1459s; ν(C = C): 1436s;
ν(C-N):1274s; ν(N-H) 3083m, 3058m, and ν(O-H) 3180 m.
INTRODUCTION
Tripodal ligands have drawn much attention in recent years,
mainly due to their selective coordinating capacity, spheroidal
cavities and hard binding sites, therefore stabilizing their com-
plexes, acquiring novel coordination structure and shielding the
encapsulated ion from interaction with the surroundings.[1–5]
These numerous tripodal ligands have demonstrated their po-
tential use in functional supramolecular chemistry.[6–10] In the
present work, an organic ion picrate was chosen as counter
anion, which possesses relatively weak coordination activity,
the cobalt complex with 2,6-bis(benzimidazol-2-yl)pyridine (L)
(Figure 1) was synthesized. The crystal structure indicates that
the complex molecule [CoL2](Pic)2(DMF) are linked by π-π
interactions and intramolecular to give infinite two-dimensional
(2-D) supramolecular layers, which are further linked by the in-
termolecular hydrogen bonds to form a three-dimensional (3-D)
netlike supramolecule.
Synthesis of the Cobalt Picrate Complex
The cobalt picrate complex was prepared by the reaction
of Co(Pic)2 and L with 1:1 molar ratio in ethanol as yellow
powder. (Found: C: 52.18; H: 2.94; N: 19.78. Anal. Calcd. for
CoL2(Pic)2(DMF): C, 52.62; H, 3.08; N, 19.68%). IR(cm–1,
KBr): ν(C = N): 1614; ν(C = C): 1438; ν(C-N): 1276;
νas(–NO2): 1554; νs(–NO2): 1341.
Crystal Structure Determination
Red crystal suitable for X-ray diffraction was obtained by
slow evaporation of the ethanol solution of the Co complex.
Single-crystal X-ray diffraction study of the title complex was
performed on a Bruker SMART CCD diffractometer equipped
with a graphite crystal monochromator situated in the incident
beam for data collection. Single crystal with dimensions of
0.48 × 0.44 × 0.40 mm3 was chosen for X-ray diffraction
studies. The determination of unit cell parameters and data col-
lections were performed with Mo Ka radiation (λ = 0.71073
Å) at 294(2) K on a Bruker SMART diffractometer. The struc-
ture was solved by direct method using SHELXS program of
Received 1 September 2012; accepted 27 January 2013.
This work was supported by Scientific Research Fund of Zhejiang
Provincial Education Department (Project No. Y201121314).
Address correspondence to Zhen-Zhong Yan, Department of Phar-
maceutics and Chemical Engineering, Taizhou University, Linhai
317000, P. R. China. E-mail: yanzhzh@tzc.edu.cn
344

A CRYSTAL STRUCTURE OF A COBALT PICRATE COMPLEX
345
TABLE 1
Crystal and experimental data
Empirical formula
Formula weight
C56H44N18O24Co
1412.02
Temperature
294(2)
Wavelength
0.71073 Å
Crystal system, space group
Unit cell dimensions
Monoclinic, c2/c
a = 21.8756(6) Å
b = 12.2995(3) Å β =
95.6060◦(10)
c = 27.4827(7) Å
7359.1(3) Å3
4
FIG. 1. The chemical structure of the ligand L.
Volume
Z
Dx
the SHELXL-97 package and refined with SHELXL.[12] Cobalt
centers were located from the E-map and other non-hydrogen
atoms were located in successive difference Fourier syntheses.
The final refinement was performed by full matrix least-squares
method with anisotropic thermal parameters for non-hydrogen
atoms on F2. The hydrogen atoms were added geometrically
and not refined. The final R = 0.0708 and wR = 0.1831 (w =
1.274 Mg·m–3
Absorption coefficient
0.316 mm–1
F(000)
2900
Crystal size
Theta range for data
collection
0.48 × 0.44 × 0.40 mm
1.87–25.60◦
1/[σ2(Fo ) + (0.1131P)2+3.1714P], where P = (Fo + 2Fc )/3), Limiting indices
–26 ≤ h ≤ 15, –14 ≤ k ≤ 14,
–33 ≤ l ≤ 33
2
2
2
S = 1.053, (ꢀρ)max = 0.601, (ꢀρ)min = –0.253 e/Å3, and
Reflections collected/unique
19606/6897
(ꢀ/σ)max = 0.000.
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices
[I>2sigma(I)]
Largest diff. peak and hole
Refinement method
6897/0/450
1.053
R1 = 0.0708, wR2 = 0.1831
RESULTS AND DISCIUSSION
A summary of crystallographic data and details of the struc-
ture refinements are listed in Table 1. The selected bond lengths
and bond angles are given in Table 2.
0.601 and –0.253 e·Å–3
Full-matrix least-squares on F2
Measurement: Bruker SMART CCD; Programs system: SHEL-
XTL-97; Structure determination: SHELXS-97.
As shown in Figure 2, in the complex [CoL2](Pic)2(DMF),
Co(II) atom is coordinated with six nitrogen atoms from two
tridentates ligand L to form a distorted octahedron (Figure 3).
Two picrate groups act as the counter anions, and one DMF
molecule locates at the outer coordination sphere. All atoms
of the same ligand L are almost in a plane, and the dihe-
dral angle between two planes formed by the two ligands is
85.64◦.
A 3D netlike supramolecule was further formed through the
hydrogen bonds and π-π interactions. The π-π interactions
between the picrate group and one benzene ring of the benz-
imidazole rings [the centroid (C1, C2, C3, C4, C5, and C6) to
the centroid (C19, C20, C21, C22, C23, and C24) distances are
3.732 Å (symmetry code: –1/2 + x, 1/2 + y, z)] form a one-
dimensional (1-D) supramolecule chains.[13,14] The chains are
linked by hydrogen bonds [C(10–H(10)···O, C(14)–H(14)···O,
N(7)–H(7)···O], thus generating a two-dimensional (2-D)
supramolecular layer as shown in Figure 4.[15] The layers are
linked by intermolecular hydrogen bond C(9) H(9)···O(5) to
form a three-dimensional (3-D) netlike supermolecule as shown
in Figure 5. In addition, there is an intermolecular hydrogen
bond N(8) H(8A)···O(8) between the tridentates ligand L and
the DMF molecular in the complex. Hydrogen bonding param-
eters of the complex are given in Table 3.
TABLE 2
Selected bond distances (Å) and angles (◦)
Co(1)-N(1)
Co(1)-N(1–2)
2.074 (3)
2.074 (3)
Co(1)-N(2)
Co(1)-N(2–2)
2.128 (3)
2.128 (3)
Co(1)-N(3)
Co(1)-N(3–2)
2.151 (3)
2.151 (3)
N(1)-Co(1)-N(1–2)
N(1)-Co(1)-N(2)
N(1)-Co(1)-N(2–2)
N(1)-Co(1)-N(3)
N(1)-Co(1)-N(3–2)
175.66 (17)
76.22 (12)
106.85 (12)
76.39 (12)
100.44 (12)
N(2)-Co(1)-N(2–2)
N(2)-Co(1)-N(1–2)
N(2)-Co(1)-N(3)
N(2)-Co(1)-N(3–2)
N(3)-Co(1)-N(3–2)
94.07 (17)
106.85 (12)
152.58 (12)
94.9 4(12)
88.81 (18)
N(1–2)-Co(1)-N(3)
N(2–2)-Co(1)-N(3)
N(1–2)-Co(1)-N(2–2)
N(1–2)-Co(1)-N(3–2)
N(2–2)-Co(1)-N(3–2)
100.44 (12)
94.94 (12)
76.22 (12)
76.39 (12)
152.58 (12)

346
Z.-Z. YAN ET AL.
FIG. 2. ORTEP diagram (30% probability ellipsoids) showing the molecular
structure of the Co complex (Color figure available online).
FIG. 4. 2-D supramolecular layers generated by hydrogen bonds and π-π
interactions in the title complex (Color figure available online).
FIG. 5. 3-D supramolecular network generated by intermolecular hydrogen
bonds (hydrogen bonds are indicated by the yellow dashed lines) (Color figure
available online).
FIG. 3. Coordination polyhedron of Co ion (Color figure available online).
TABLE 3
Hydrogen-bonds in crystal packing (Å, ◦)
D—H···A
d(D—H)/nm
d(H. . .A)/nm
d(D. . .A)/nm
∠DHA/(◦)
Symmetry
N(8) H(8A)···O(8)
C(9) H(9)···O(5)
N(7) H(7)···O(1)
N(7) H(7)···O(2)
C(10) H(10)···O(2)
C(10) H(10)···O(3)
C(14) H(14)···O(1)
0.86
0.93
0.86
0.86
0.93
0.93
0.93
1.84
2.56
2.60
1.97
2.26
2.55
2.48
2.6984
3.3041
3.1547
2.7929
3.1161
3.1761
3.1278
174
138
123
161
153
125
127
–x, 2 – y, –z
1/2 – x, 3/2 – y, –z

A CRYSTAL STRUCTURE OF A COBALT PICRATE COMPLEX
347
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