A mesitylene-bridged bis-benzimidazolyl ligand and six metal coordination compounds

Article abstract of DOI:10.1080/00958972.2016.1219349

The mesitylene-bridged bis-benzimidazolyl ligand 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L) and six metal complexes, [Cu₉L₆(OH)₇Cl₈] (1), [Co₂L₄(NO₃)(H₂O)_2<

Full text of DOI:10.1080/00958972.2016.1219349

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
A mesitylene-bridged bis-benzimidazolyl ligand
and six metal coordination compounds
Qing-Xiang Liu, Yue Ding, Xiao-Qiang Zhao, Zhi-Xiang Zhao, Jie Yu & Jian-Hua
Wang
To cite this article: Qing-Xiang Liu, Yue Ding, Xiao-Qiang Zhao, Zhi-Xiang Zhao, Jie Yu & Jian-
Hua Wang (2016): A mesitylene-bridged bis-benzimidazolyl ligand and six metal coordination
compounds, Journal of Coordination Chemistry, DOI: 10.1080/00958972.2016.1219349
To link to this article: http://dx.doi.org/10.1080/00958972.2016.1219349
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Date: 12 September 2016, At: 18:48

Journal of Coordination Chemistry, 2016
http://dx.doi.org/10.1080/00958972.2016.1219349
A mesitylene-bridged bis-benzimidazolyl ligand and six metal
coordination compounds
Qing-Xiang Liua,b, Yue Dinga,b, Xiao-Qiang Zhaoa,b, Zhi-Xiang Zhaoa,b, Jie Yua,b and
Jian-Hua Wanga,b
aKey laboratory of inorganic-organic hybrid functional materials Chemistry (tianjin normal university), ministry of
education, tianjin, China; btianjin Key laboratory of structure and Performance for functional molecules, College of
Chemistry, tianjin normal university, tianjin, China
ABSTRACT
ARTICLE HISTORY
received 23 January 2016
accepted 15 June 2016
The mesitylene-bridged bis-benzimidazolyl ligand 1,3-bis(benzimidazol-
1′-yl-methyl)mesitylene (L) and six metal complexes, [Cu9L6(OH)7Cl8] (1),
[Co2L4(NO3)(H2O)2](NO3)3 (2), [Zn2L2Cl4] (3), [CdL2(NO3)2]n (4), [MnL(LA)
(CH3OH)]n (5), and [CoLCl2]n (6) (LA = terephthalate), have been prepared
and characterized. Complex 1 is a football-like cluster formed by six Ls,
nine Cu(II) ions, eight chlorides, and seven hydroxides, in which the size
of the football is about 13.9 × 15.4 Å. Complex 2 contains a cage-like ball
formed by four Ls and two Co(II) ions, in which the external and internal
sizes of the ball are about 12.2 × 14.6 Å and 6.5 × 10.7 Å, respectively. In this
complex, one nitrate is fixed in the middle of the cage through two Co–O
bonds. The 24-membered metallomacrocycle of 3 is formed by two Ls and
two Zn(II) ions. In 4, 2-D layers with 48-membered metallomacrocycles are
formed via Ls and Cd(II) ions. In 5, L and terephthalate ions (LA) participate
in coordination with Mn(II) to afford 2-D network layers. The 1-D polymeric
chain of 6 is formed via L and Co(II) chloride moieties. In the crystal packing
of 1–6, 2-D supramolecular layers and 3-D supramolecular frameworks are
formed via intermolecular weak interactions, including hydrogen bonds, π–π
interactions, and C–H⋯π contacts. The conformations of metal complexes
from L are described. Additionally, the fluorescence emission spectra of L
and 1–6 are reported.
KEYWORDS
metal; complex; structure;
bis-benzimidazole
Software of Graphics: Ligand L, H2LA and Schemes 1–3: Chem Draw 8.0
Figures 1–6: Diamand 3.0
Figure 7: Origin 8.0
CONTACT Qing-Xiang liu
hxxylqx@mail.tjnu.edu.cn
supplemental data for this article can be accessed here at http://dx.doi.org/10.1080/00958972.2016.1219349.
© 2016 informa uK limited, trading as taylor & francis Group

2
Q.-X. LIu eT AL.
1. Introduction
Polynuclear metal complexes attract attention due to potential applications in ion-exchange resins [1],
biological probes [2], and host–guest chemistry [3]. These complexes are generally formed by organic
ligands and transition metals via coordination bonds, in which the metal centers are connecting nodes
and the organic ligands are building blocks. Discrete low-dimensional metal complexes can be further
connected into high-dimensional supramolecular architectures via intermolecular weak interactions
(such as hydrogen bonds [4], aromatic π⋯π interactions [5], and C–H⋯π contacts [6]).
In construction of polynuclear metal complexes, the ligands have important influence on the sizes
and shapes of the architectures formed. Bis-benzimidazolyl compounds with different linkers (such
as polyether chains [7] and alkyl chains [8]) are important bidentate ligands, and they can coordinate
with a number of metal ions to form coordination architectures with variable cavities or channels [9].
Additionally, the benzimidazole ring is a structural component of many compounds in living organ-
isms [10]. Therefore, investigating the structure of metal complexes from benzimidazolyl ligands and
metal ions has significance toward knowing the coordinating process in life science. We are interested
in coordination behavior of bis-benzimidazolyl ligands bearing different linkers. Herein, we report the
preparation of 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L), as well as the preparation, structures,
and weak interactions of six of its metal complexes. The conformations of the metal complexes from
L, and the fluorescence emission spectra of L and 1–6 are reported.
N
N
N
N
HOOC
COOH
H2LA
L

JOurNAL OF COOrDINATION CHeMISTrY
3
2. Experimental
2.1. General procedures
Commercially available reagents and chemicals were of analytical grade purity and used without puri-
fication. 1,3-bis(bromomethyl)mesitylene and 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene were pre-
pared with analogous methods to the literature [11, 12]. Melting points were determined with a Boetius
Block apparatus. 1H NMr spectra were recorded on a Varian Mercury Vx 400 spectrometer at 400 MHz.
Chemical shifts, δ, were reported in ppm relative to the internal standard TMS for 1H NMr, and J val-
ues were given in Hz. elemental analyses of all compounds were obtained from powder compounds
recrystallized and measured using a Perkin-elmer 2400C elemental Analyzer. The fluorescence spectra
were performed using a Cary eclipse fluorescence spectrophotometer.
2.2. Preparation of 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L)
To a mixture of mesitylene (12.000 g, 99.8 mmol), paraformaldehyde (6.000 g, 199.8 mmol), and glacial
acetic acid (100 mL), hydrogen bromide gas was introduced for 5 h at 50 °C and a massive precipitate
formed. A white powder of 1,3-bis(bromomethyl)mesitylene was obtained after filtration. Yield: 28.496 g
(93%). M.p.: 140–142 °C.
A CH3CN (100 mL) suspension of benzimidazole (1.699 g, 14.4 mmol), KOH (1.467 g, 26.3 mmol), and
tetrabutylammonium bromide (0.211 g, 0.6 mmol) was stirred for 2 h under reflux and then 1,3-bis(bro-
momethyl)mesitylene (2.000 g, 6.5 mmol) was slowly added and stirred continually for 72 h at 80 °C.
A pale yellow powder was obtained after removing the solvent. The powder was dissolved in CH2Cl2
(100 mL) and washed with water (3 × 100 mL), and the organic layer was dried over anhydrous MgSO4.
After removing the CH2Cl2, a white powder of 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L) was
obtained. Yield: 2.215 g (89%). M.p.: 258–260 °C. Anal. Calcd for C25H24N4: C, 79.91; H, 6.35; N, 14.72%.
Found: C, 79.55; H, 6.47; N, 14.89%. 1H NMr (400 MHz, DMSO-d6): δ 2.13 (s, 3H, CH3), 2.30 (s, 6H, CH3), 5.46
(s, 4H, PhCH2), 7.15 (s, 1H, PhH), 7.20–7.23 (q, J = 3.1 Hz, 4H, bimiH), 7.45–7.47 (t, J = 4.4 Hz, 2H, bimiH),
7.65–7.67 (q, J = 3.1 Hz, 2H, bimiH), 7.78 (s, 2H, 2-bimiH) (bimi = benzimidazole).
2.3. Preparation of {[1,3-bis(benzimidazol-1′-yl-methyl)mesitylene]6Cu9(OH)7Cl8} (1)
A DMF (5 mL) solution of 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L) (0.050 g, 0.1 mmol) was added
to a methanol solution (15 mL) of CuCl2·2H2O (0.051 g, 0.3 mmol). The mixture was stirred for 1 h at
40 °C. The filtrate was allowed to evaporate slowly under ambient conditions, and blue single crystals
suitable for X-ray analysis were obtained within two weeks. Yield: 0.034 g (63%). M.p.: 180–182 °C. Anal.
Calcd for C150H151N24Cu9O7Cl8: C, 55.30; H, 4.67; N, 10.31%. Found: C, 55.43; H, 4.65; N, 10.53%.
2.4. Preparation of {[1,3-bis(benzimidazol-1′-yl-methyl)mesitylene]4Co2(NO3)(H2O)2}(NO3)3
(2)
This complex was prepared in a manner analogous to that of 1, only Co(NO3)2·6H2O (0.087 g, 0.3 mmol)
was used instead of CuCl2·2H2O, and red single crystals suitable for X-ray analysis were obtained after
three weeks. Yield: 0.020 g (42%). M.p.: 210–212 °C. Anal. Calcd for C50H50CoN10O7: C, 62.43; H, 5.23; N,
14.56%. Found: C, 62.80; H, 5.45; N, 14.32%.
2.5. Preparation of {[1,3-bis(benzimidazol-1′-yl-methyl)mesitylene]2Zn2Cl4} (3)
This complex was prepared in a manner analogous to that of 1, only ZnCl2 (0.039 g, 0.3 mmol) was
used instead of CuCl2·2H2O, and colorless single crystals suitable for X-ray analysis were obtained after
three weeks. Yield: 0.031 g (60%). M.p.: 280–282 °C. Anal. Calcd for C50H48N8Zn2Cl4: C, 58.10; H, 4.68; N,
10.84%. Found: C, 58.41; H, 4.76; N, 10.64%.

4
Q.-X. LIu eT AL.
2.6. Preparation of {[1,3-bis(benzimidazol-1′-yl-methyl)mesitylene]2Cd(NO3)2}n (4)
This complex was prepared in a manner analogous to that of 1, only Cd(NO3)2·4H2O (0.092 g, 0.3 mmol)
was used instead of CuCl2·2H2O, and colorless single crystals suitable for X-ray analysis were obtained
after two weeks. Yield: 0.030 g (62%). M.p.: 262–264 °C. Anal. Calcd for C25H24N5Cd0.5O3: C, 60.21; H, 4.85;
N, 14.04%. Found: C, 60.42; H, 4.72; N, 14.35%.
2.7. Preparation of {[1,3-bis(benzimidazol-1′-yl-methyl)mesitylene](terephthalate)
Mn(CH3OH)}n (5)
A DMF (5 mL) solution of terephthalic acid (H2LA) (0.049 g, 0.3 mmol) was added to a DMF (5 mL)
solution of L (0.050 g, 0.1 mmol). The mixture was stirred for 3 min. Then a methanol solution (15 mL)
of Mn(ClO4)2·6H2O (0.108 g, 0.3 mmol) was added and the pH of the solution was adjusted to 7 with
triethylamine. The mixture was stirred for 2 h at 40 °C. The filtrate was allowed to evaporate slowly under
ambient conditions, and colorless single crystals suitable for X-ray analysis were obtained within two
weeks. Yield: 0.038 g (61%). M.p.: 310–312 °C. Anal. Calcd for C34H32N4MnO5: C, 64.65; H, 5.10; N, 8.87%.
Found: C, 64.89; H, 4.93; N, 8.74%.
2.8. Preparation of {[1,3-bis(benzimidazol-1′-yl-methyl)mesitylene]CoCl2}n (6)
This complex was prepared in a manner analogous to that of 1, only CoCl2·2H2O (0.049 g, 0.3 mmol)
was used instead of CuCl2·2H2O, and blue single crystals suitable for X-ray analysis were obtained after
three weeks. Yield: 0.031 g (62%). M.p.:>320 °C. Anal. Calcd for C50H48N8Co2Cl4: C, 58.83; H, 4.74; N, 8.87%.
Found: C, 58.77; H, 4.94; N, 8.63%.
2.9. X-ray data collection and structure determinations
X-ray single-crystal diffraction data for 1–6 were collected using a Bruker Apex II CCD diffractometer at
296(2) K for 1, 2, and 5 and 173(2) K for 3, 4, and 6 with Mo-Kα radiation (λ = 0.71073 Å) by ω scan mode.
There was no evidence of crystal decay during data collection in all cases. Semiempirical absorption
corrections were applied using SADABS and SAINT was used for integration of the diffraction profiles
[13]. All structures were solved by direct methods using SHeLXS of the SHeLXTL package and refined
with SHeLXL [14] by full-matrix least-squares methods with anisotropic thermal parameters for all
non-hydrogen atoms on F2. Hydrogens bonded to C were placed geometrically and solvent hydrogens
were first located in difference Fourier maps and then fixed in the calculated sites. Further details for
crystallographic data and structural analysis are listed in tables 1 and 2, which were generated using
Crystal-Maker [15]. Bond distances and angles of 1–6 are given in tables 3 and 4.
3. Results and discussion
3.1. Synthesis and characterization of 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L) and
metal complexes 1–6
The 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L) was prepared through reaction of benzimidazole
with 1,3-bis(bromomethyl)mesitylene (scheme 1). L is stable to air and moisture and soluble in CH3OH,
CH3CN, and DMF, but scarcely soluble in water, petroleum ether, and diethyl ether.
[Cu9L6(OH)7Cl8] (1), [Co2L4(NO3)(H2O)2](NO3)2 (2), [Zn2L2Cl4] (3), [CdL2(NO3)2]n (4) and [CoLCl2]n (6)
were prepared via reaction of L with metal salts in DMF/CH3OH (CuCl2·2H2O for 1, Co(NO3)2·6H2O for
2, ZnCl2 for 3, CoCl2·2H2O for 4, and Cd(NO3)2·4H2O for 6). [MnL(LA)(CH3OH)]n (5) was prepared via the
reaction of a mixture of L and terephthalic acid (H2LA) with Mn(ClO4)2·6H2O in the presence of trieth-
ylamine in DMF/CH3OH. Crystals of 1–6 suitable for X-ray diffraction were grown by slow evaporation
at room temperature. Complexes 1-6 are stable to air and moisture, and their structural integrity can

JOurNAL OF COOrDINATION CHeMISTrY
5
Table 1. summary of crystallographic data for 1–3.
1
2·2H2O·CH3OH
3·DMF
Chemical formula
formula weight
Crystal system
C150h151Cl8Cu9n24o7
C50h50Con10o7·2h2o·Ch3oh
C50h48Cl4n8Zn2·dmf
1106.60
triclinic
Pī
3257.40
hexagonal
P63/m
20.8473(9)
20.8473(9)
26.0224(10)
90
90
120
9794.4(9)
2
1.105
1.114
3344
0.19 × 0.18 × 0.17
1.128, 24.590
296.15
48,778
5621
1030.00
monoclinic
P21/n
14.5539(18)
18.471(2)
18.809(2)
90
92.766(2)
90
5050.4(11)
4
space group
a (Å)
b (Å)
c (Å)
10.516(4)
11.786(5)
21.521(9)
82.654(8)
79.702(9)
69.589(7)
2453.4(18)
2
α (°)
β (°)
γ (°)
V (Å3)
Z
D
Calcd (mg m−3)
1.355
0.408
2164
1.498
1.246
1144
abs. coeff. (mm−1)
F(0 0 0)
Crystal size (mm)
0.14 × 0.13 × 0.12
1.546, 25.010
296.15
0.15 × 0.14 × 0.13
0.964, 25.009
173.15
θ
min, θmax (°)
T (K)
no. of data collected
no. of unique data
no. of refined params.
reflns. number gt
R (int)
25,409
8880
693
7205
0.0378
1.049
12,624
8618
648
4510
0.0748
1.011
303
3822
0.0606
1.039
Goodness-of-fit on F2 a
final R indices b [I > 2σ(I)]
R1
0.0752
0.2336
0.0453
0.1231
0.0633
0.1034
wR2
R indices (all data)
R1
wR2
0.0970
0.2493
0.0589
0.1358
0.1591
0.1348
aGof = [Σw(Fo2 − Fc2)2/(n − p)]1/2, where n is the number of reflection and p is the number of parameters refined.
2 2 1/2
bR1 = Σ(||Fo| − |Fc||)/Σ|Fo|; wR2 = [Σ[w(Fo2 − Fc2)2]/Σw(Fo ) ]
.
be retained at room temperature for a considerable length of time. The solubility of these complexes
is poor in most organic solvents; however, they can be dissolved in DMSO.
3.2. Crystal structure of 1–6
The football-like 1 lies about a center of -6 symmetry and is formed by six bis-benzimidazolyl ligands
L, nine Cu(II) ions, eight chlorides, and seven hydroxide ions as shown in figure 1(a), in which the size
of the football is about 13.9 × 15.4 Å. In each ligand, the dihedral angle of two benzimidazole rings is
72.4(5)°, and the dihedral angles between the mesitylene moiety and the two benzimidazole rings are
84.0(9)° and 86.3(1)°. The dihedral angle between two benzimidazole rings connected to the same Cu(II)
is 75.6(1)°. In the football, two adjacent mesitylene rings form the dihedral angle of 58.8(1)°, two interval
mesitylene rings form the dihedral angle of 60.0(8)°, and two opposing mesitylene rings are parallel.
The core of this complex is a bipyramidal cylinder as shown in figure 1(b), in which nine Cu(II) ions are
divided into two groups according to different coordination numbers. Six Cu(II) ions in the first group lie
at both ends of the bipyramidal cylinder, and they are five-coordinate by one chloride, two oxygens, and
two nitrogens from two benzimidazole rings of two Ls to adopt a distorted square pyramidal geometry.
Three Cu(II) ions in the second group lie in the middle of the bipyramidal cylinder, and they are six-co-
ordinate with three oxygens and three chlorides to adopt a slightly distorted octahedral coordination.
Seven oxygens in the bipyramidal cylinder are three-coordinate, and each oxygen is bonded to three
Cu(II) ions to form a O–Cu3 unit. In the central O-Cu3 unit of the bipyramidal cylinder, four atoms are
coplanar. The other six O–Cu3 units have a shallow trigonal pyramidal shape. The eight chlorides in the
bipyramidal cylinder contain three types of coordination models, two chlorides which are placed at

6
Q.-X. LIu eT AL.
Table 2. summary of crystallographic data for 4–6.
4·2DMF
5·CH3OH
6·CH3OH
Chemical formula
formula weight
Crystal system
C50h48Cdn10o6·2dmf
1143.59
monoclinic
C2/c
C34h32mnn4o5·Ch3oh
663.62
C50h48Cl4Co2n8·Ch3oh
1052.67
orthorhombic
Pbca
monoclinic
P21/n
13.290(3)
18.050(4)
13.903(3)
90
105.749(18)
90
3209.9(13)
4
space group
a (Å)
b (Å)
c (Å)
21.0093(19)
13.2687(12)
20.1632(19)
90
108.4360(10)
90
5332.3(8)
4
1.424
0.477
2376
0.15 × 0.14 × 0.13
1.84, 25.01
173(2)
18.1766(17)
18.5808(19)
29.801(3)
90
α (°)
β (°)
90
90
γ (°)
V (Å3)
Z
10,064.9(17)
8
D
Calcd (mg m−3)
1.373
0.463
1388
1.389
0.917
4352
abs. coeff. (mm−1)
F(0 0 0)
Crystal size (mm)
0.12 × 0.11 × 0.10
1.880, 28.493
296.15
0.13 × 0.12 × 0.10
1.37, 25.01
173(2)
θ
min, θmax (°)
T (K)
no. of data collected
no. of unique data
no. of refined params.
reflns. number gt
R (int)
13,222
4708
353
4411
0.0231
1.027
20,078
7893
420
4728
0.0249
1.031
49,516
8867
602
5736
0.1137
1.016
Goodness-of-fit on F2 a
final R indicesb [I > 2σ(I)]
R1
0.0229
0.0552
0.0401
0.1143
0.0471
0.0903
wR2
R indices (all data)
R1
wR2
0.0250
0.0563
0.0565
0.1252
0.0931
0.1090
aGof = [Σw(Fo2 − Fc2)2/(n − p)]1/2, where n is the number of reflection and p is the number of parameters refined.
2 2 1/2
bR1 = Σ(||Fo| − |Fc||)/Σ|Fo|; wR2 = [Σ[w(Fo2 − Fc2)2]/Σw(Fo ) ]
.
the ends of the bipyramidal cylinder are coordinated by three Cu(II) ions, three chlorides (Cl(1), Cl(1A)
and Cl(1B)) are coordinated by two Cu(II) ions, and three other chlorides (Cl(2), Cl(2A) and Cl(2B)) are
coordinated by one Cu(II). In the middle of the bipyramidal cylinder, six chlorides and one O–Cu3 unit
are coplanar, and this plane is the symmetric plane of the bipyramidal cylinder and the football. The
values of bond distances and angles in this complex are similar to those of known Cu(II) complexes [16].
Complex 2 contains a cage-like ball formed by four L and two Co(II) ions as shown in figure2(a).
The external and internal sizes of the ball are about 12.2 × 14.6 Å and 6.5 × 10.7 Å, respectively. The
Co⋯Co distance is 6.557(7) Å. In the same ligand, the dihedral angle of two benzimidazole rings
is 87.1(9)°, and the dihedral angles between the mesitylene ring and two benzimidazole rings are
83.2(2)° and 88.9(2)°. Among the four benzimidazole rings connected to each Co(II), the dihedral
angles of two adjacent benzimidazole rings are 54.2(4)–68.5(8)° (table S1), and two opposing ben-
zimidazole rings form dihedral angles of 88.5(6)–87.2(9)°. The opposing mesitylene rings are sym-
metry-related, and the distances between two groups of opposing mesitylene rings are ca. 10.94
and 11.11 Å. One nitrate in 2 is fixed in the cage through two Co–O bonds and is disordered about a
center of symmetry at the center of the cage. each Co(II) is six-coordinate with four nitrogens from
four benzimidazole rings of four Ls, and two oxygens (one from a nitrate and another from a water)
to afford slightly distorted octahedral coordination. An equatorial plane of the octahedron may be
defined by the four nitrogens (N(1), N(4A), N(5) and N(8A)), and the two oxygens (O(1) and O(2)) lie
in the axial positions. The values of bond distances and angles in this complex are similar to those
of known Co(II) complexes [17].
In 3 (figure 3(a)), there are two independent, but essentially identical 24-membered macrocyclic
molecules; π⋯π interactions between mesitylene and benzimidazole rings from both molecules are

JOurNAL OF COOrDINATION CHeMISTrY
7
Table 3. selected bond lengths (Å) and angles (°) for 1–3.
Complex 1
Cu(1)–Cl(3)
Cu(1)–o(2)
2.7835(18)
1.986(3)
Cu(1)–o(2B)
Cu(1)–n(1)
2.009(3)
2.031(4)
Cu(1)–n(3)
Cu(2)–Cl(2)
Cu(2)–o(2)
1.974(4)
2.196(3)
2.033(4)
Cu(2)–Cl(1)
Cu(2)–o(1)
Cu(2)–o(2d)
2.721(2)
1.8347(12)
2.033(4)
o(2)–Cu(1)–o(2B)
o(2)–Cu(1)–Cl(3)
n(3)–Cu(1)–Cl(3)
o(2)–Cu(1)–n(1)
Cl(2)–Cu(2)–Cl(1)
o(1)–Cu(2)–Cl(2)
o(2)–Cu(2)–Cl(2)
o(2)–Cu(2)–o(2d)
Cu(1)–o(2)–Cu(1a)
Cu(1a)–o(2)–Cu(2)
90.24(18)
81.52(10)
105.70(14)
88.40(16)
94.17(9)
179.53(10)
95.70(9)
167.54(19)
119.63(18)
117.19(15)
n(3)–Cu(1)–n(1)
o(2B)–Cu(1)–Cl(3)
n(1)–Cu(1)–Cl(3)
o(2)–Cu(1)–n(3)
o(1)–Cu(2)–Cl(1)
o(2)–Cu(2)–Cl(1)
o(1)–Cu(2)–o(2)
Cu(2)–o(1)–Cu(2a)
Cu(1)–o(2)–Cu(2)
90.92(19)
81.13(10)
107.25(14)
172.60(18)
86.30(6)
92.08(9)
84.28(9)
120.0
112.18(15)
Complex 2
Co(1)–n(1)
Co(1)–n(5)
Co(1)–o(1)
2.125(2)
2.121(2)
2.1081(19)
92.00(8)
89.42(8)
89.81(8)
87.44(8)
88.20(8)
91.52(8)
93.30(8)
170.30(13)
Co(1)–n(4a)
Co(1)–n(8a)
Co(1)–o(2)
n(4a)–Co(1)–n(8a)
n(1)–Co(1)–n(4a)
n(5)–Co(1)–n(8a)
n(1)–Co(1)–o(2)
n(4a)–Co(1)–o(2)
n(5)–Co(1)–o(2)
n(8a)–Co(1)–o(2)
2.124(2)
2.129(2)
2.223(5)
89.13(9)
175.55(9)
175.03(8)
83.17(14)
101.15(14)
86.00(16)
89.45(16)
n(1)–Co(1)–n(8a)
n(1)–Co(1)–n(5)
n(5)–Co(1)–n(4a)
n(1)–Co(1)–o(1)
n(4a)–Co(1)–o(1)
n(5)–Co(1)–o(1)
n(8a)–Co(1)–o(1)
o(1)–Co(1)–o(2)
Complex 3
Zn(1)–Cl(1)
Zn(1)–n(1)
2.192(2)
2.017(5)
Zn(1)–Cl(2)
Zn(1)–n(4a)
2.2382(19)
2.034(5)
Zn(2)–Cl(3)
Zn(2)–n(5)
2.2164(18)
2.017(5)
Zn(2)–Cl(4)
Zn(2)–n(8a)
2.2056(19)
1.998(6)
Cl(1)–Zn(1)–Cl(2)
n(1)–Zn(1)–Cl(2)
Cl(3)–Zn(2)–Cl(4)
n(5)–Zn(2)–Cl(4)
118.75(8)
108.68(14)
119.28(8)
106.05(16)
n(1)–Zn(1)–Cl(1)
n(1)–Zn(1)–n(4a)
n(5)–Zn(2)–Cl(3)
n(8a)–Zn(2)–Cl(3)
110.34(16)
99.2(2)
108.05(14)
107.95(17)
observed (table S2) [5]. each molecule is formed by two L and two Zn(II) ions, with each Zn(II) surrounded
by two chlorides and two nitrogens from two benzimidazole rings of two L in a tetrahedral coordination.
In each molecule, an inversion center is observed. The Zn(1)⋯Zn(1A) and Zn(2)⋯Zn(2A) distances are
10.964(4) and 10.609(4) Å. Two pairs of opposing benzimidazole rings in each molecule are parallel to
each other, and the face-to-face distances between them are 4.965(1) and 9.705(2) Å (or 4.962(3) and
9.735(7) Å). One pair of opposing mesitylene rings in each molecule is also parallel with face-to-face
distance of 7.504(9) Å (or 8.501(8) Å). In the same ligand of each molecule, the dihedral angle between
two benzimidazole rings is 68.4(1)° (or 77.8(8)°), and the dihedral angles between the mesitylene and
two benzimidazole rings are 83.0(4) and 84.6(9)° (or 87.6(9) and 89.6(7)°). The values of bond distances
and angles in this complex are consistent with those from published Zn(II) complexes [18].
Complex 4 is a 2-D network layer containing 48-membered metallomacrocyclic rings (figure 4(a)).
each metallomacrocycle is constructed from four L and four Cd(II) ions (figure 4(b)), in which two pairs
of opposing mesitylene rings are parallel to each other, the distance between two adjacent Cd(II) ions is
12.424(3) Å, and the distances between two pairs of opposing Cd(II) ions are 13.268(1) and 21.009(1) Å.
In the same ligand, the dihedral angle between two benzimidazole rings is 77.5(1)°, and the dihedral
angles between the mesitylene and two benzimidazole rings are 87.6(4) and 87.8(1)°. Among the four
benzimidazole rings connected to the same Cd(II), the dihedral angles between two benzimidazole
rings range from 58.7(5) to 79.1(1)°. each Cd(II) is surrounded by four nitrogens from four benzimidazole

8
Q.-X. LIu eT AL.
Table 4. selected bond lengths (Å) and angles (°) for 4–6.
Complex 4
Cd(1)–n(1)
Cd(1)–o(1)
n(1)–Cd(1)–n(1a)
n(1)–Cd(1)–n(4a)
n(1)–Cd(1)–o(1a)
n(4B)–Cd(1)–o(1a)
2.3051(14)
2.4087(12)
104.65(7)
166.60(5)
84.88(5)
Cd(1)–n(4a)
2.3228(14)
81.04(7)
87.50(5)
86.36(5)
90.38(5)
n(4a)–Cd(1)–n(4B)
n(1)–Cd(1)–n(4B)
n(1)–Cd(1)–o(1)
n(4a)–Cd(1)–o(1a)
o(1)–Cd(1)–o(1a)
100.55(5)
165.66(7)
Complex 5
mn(1)–o(4a)
mn(1)–o(1)
mn(1)–n(1)
2.0939(13)
2.2242(14)
2.2678(17)
57.79(5)
146.99(6)
176.70(6)
93.86(6)
92.35(5)
91.60(6)
86.50(6)
92.00(6)
mn(1)–o(5)
mn(1)–n(4a)
mn(1)–o(2)
2.1742(16)
2.2454(17)
2.3244(15)
89.27(6)
119.11(6)
119.11(6
174.00(6)
93.27(6)
o(1)–mn(1)–o(2)
o(2)–mn(1)–o(5)
o(4a)–mn(1)–o(1)
o(4a)–mn(1)–o(5)
o(1)–mn(1)–n(1)
o(2)–mn(1)–n(1)
o(4a)–mn(1)–n(1)
o(5)–mn(1)–n(1)
o(1)–mn(1)–o(5)
o(2)–mn(1)–o(4a)
o(4a)–mn(1)–o(2)
n(1)–mn(1)–n(4a)
o(1)–mn(1)–n(4a)
o(2)–mn(1)–n(4a)
o(4a)–mn(1)–n(4a)
o(5)–mn(1)–n(4a)
89.61(6)
87.78(6)
90.18(7)
Complex 6
Co(1)–n(1)
Co(1)–Cl(1)
Co(2)–n(4)
2.009(3)
2.2776(11)
2.029(3)
Co(1)–n(8a)
Co(1)–Cl(2)
Co(2)–n(5)
2.009(3)
2.2357(11)
2.017(3)
Co(2)–Cl(3)
2.2612(11)
109.61(13)
104.57(9)
100.09(10)
102.39(13)
113.20(10)
107.25(9)
Co(2)–Cl(4)
2.2295(11)
111.29(4)
112.39(9)
117.50(10)
116.52(4)
102.91(10)
113.74(9)
n(1)–Co(1)–n(8a)
Cl(1)–Co(1)–Cl(8a)
n(1)–Co(1)–Cl(1)
n(4)–Co(2)–n(5)
n(4)–Co(2)–Cl(3)
n(5)–Co(2)–Cl(3)
Cl(1)–Co(1)–Cl(2)
Cl(2)–Co(1)–Cl(8a)
n(1)–Co(1)–Cl(2)
Cl(3)–Co(2)–Cl(4)
n(4)–Co(2)–Cl(4)
n(5)–Co(2)–Cl(4)
HBr
Br
(HCHO)n
N
N
N
N
N
N
N
NH
Br
KOH
cis
N
N
trans
Scheme 1. Preparation of ligand L.
rings of four L and two oxygens from two nitrates in an octahedral coordination. The equatorial plane
of the octahedron is occupied by four nitrogens (N(1), N(1A), N(4) and N(4A)), and two oxygens (O(1)
and O(1A)) are axial. The values of bond distances and angles in this complex compare favorably with
analogous ones from known Cd(II) complexes [19].
In 5, L and LA (terephthalate) participate in coordination with the Mn(II) to afford 2-D network layers
with 42-membered metallomacrocyclic rings (figure 5(a)). each metallomacrocycle is constructed by
two L, two LA, and four Mn(II) ions around a center of symmetry at the center of the ring (figure 5(b)).
In each metallomacrocycle, two pairs of opposing benzimidazole rings and two pairs of opposing
benzene rings are parallel to each other, and π–π interactions [5] between two benzimidazole rings

JOurNAL OF COOrDINATION CHeMISTrY
9
Figure 1. (a) Perspective view of 1. (b) the coordination environment of Cu(ii). symmetry code: a = 1 − x + y, 1 − x, z, B = 1 − y, x − y,
z, C = 1 − y, x − y, 0.5 − z, d = x, y, 0.5 − z, e = 1 − x + y, 1 − x, 0.5 − z. (c) 2-d layer of 1 via π–π interactions.
are observed (table S2). The Mn⋯Mn distance between the two ends of a terephthalate is 10.855(3) Å
and between the ends of L is 12.336(3) Å. In each L, the dihedral angle between two benzimidazole
rings is 31.9(7)°, and the dihedral angles between the mesitylene and two benzimidazole rings are
74.2(2) and 85.3(3)°. The dihedral angle between two benzimidazole rings connected to the same

10
Q.-X. LIu eT AL.
Figure 2. (a) Perspective view of 2. all hydrogens were omitted for clarity, and the alternative site of the disordered nitrate has
been omitted; symmetry code: a = 1 − x, 2 − y, 2 − z. (b) 2-d supramolecular layer of 2 formed via C–h⋯o hydrogen bonds. (c) 3-d
supramolecular architecture of 2 formed via o–h⋯o hydrogen bonds. in (b) and (c), all hydrogens except those participating in
the C–h⋯o and o–h⋯o hydrogen bonds were omitted for clarity.
Mn(II) is 31.9(7)°. In the two carboxyl groups of each terephthalate, one is mono-coordinated and
the other is di-coordinated. each Mn(II) is six-coordinate with two nitrogens from two benzimidazole
rings of two L and four oxygen donors (two from one chelating carboxyl group, the third oxygen from
another carboxyl group, and the fourth from a methanol) in octahedral coordination. The equatorial
plane of the octahedron is occupied by four oxygens (O(1), O(2), O(4A) and O(5)), with N(1) and N(4A)
axial. The values of bond distances and angles in this complex are similar to those from reported
Mn(II) complexes [20].
The 1-D zigzag polymeric chains of 6 are formed via Ls and Co(II) ions (figure 6(a)). In the polymer
chain, both ligands connected to the same Co(II) are very similar, but independent, and the dihedral
angle between the two mesitylene rings from both ligands is 88.2(7)°. The dihedral angle between
two benzimidazole rings connected to the same Co(II) is 89.2(7)°. In each ligand, the dihedral angle
between two benzimidazole rings is 26.4(4)° (or 46.0(5)°), and the dihedral angles between the mesi-
tylene and two benzimidazole rings are 79.2(8) and 82.3(2)° (or 79.8(6) and 83.4(0)°). The Co⋯Co sepa-
rations between the two ends of L are 11.947(5) and 12.132(5) Å, and the angles between neighboring

JOurNAL OF COOrDINATION CHeMISTrY
11
Figure 3. (a) Perspective view of 3. all hydrogens were omitted for clarity. symmetry code: a = −x, 2 − y, −z. (b) 2-d supramolecular
layer of 3 formed via C–h⋯Cl hydrogen bond interactions. (c) 3-d supramolecular architecture of 3 formed via new C–h⋯Cl hydrogen
bond interactions. in (b) and (c), all hydrogens except those participating in the C–h⋯Cl hydrogen bonds were omitted for clarity.
Co⋯Co⋯Co are 59.8(3) and 108.0(1)°. each Co(II) has two nitrogens from two benzimidazole rings of
two L and two chlorides in tetrahedral coordination. The values of bond distances and angles in this
complex are similar to those of 2 and reported Co(II) complexes [17].

12
Q.-X. LIu eT AL.
Figure 4. (a) Perspective view of 4. all hydrogens were omitted for clarity. symmetry code: a = -0.5 + x, 0.5 + y, z, B = 1.5 − x, 0.5 + y,
1.5 − z. (b)the 48-membered metallomacrocycle in 4. (c) 3-d supramolecular architecture of 4 formed via C–h⋯o hydrogen bonds.
all hydrogens except those participating in the C–h⋯o hydrogen bonds were omitted for clarity.
3.3. The crystal packing of 1–6
As shown in figure 1(c), the 2-D supramolecular layer of 1 is formed via π⋯π interactions [5] from
benzimidazole rings (table S2).

JOurNAL OF COOrDINATION CHeMISTrY
13
Figure 5. (a) Perspective view of 5. (b) the 42-membered metallomacrocycle in 5. (c) 3-d supramolecular frameworks of 5 formed
via π–π interactions. in (a)–(c), all hydrogens were omitted for clarity.
The 2-D supramolecular layer of 2 (figure 2(b)) is formed via C–H⋯O hydrogen bonds [4(c)] (table
S3). In the hydrogen bonds, the hydrogens are from methyl groups of mesitylene rings and the oxygens
are from nitrate. The 2-D layers are further extended into 3-D supramolecular frameworks via similar
C–H⋯O hydrogen bonds (figure 2(c)).

14
Q.-X. LIu eT AL.
Figure 6. (a) Perspective view of 6. all hydrogens were omitted for clarity. symmetry code: a = −x, −0.5 + y, 0.5 − z. (b) 2-d
supramolecular layer of 6 formed via C–h⋯π contacts. (c) 3-d supramolecular architecture of 6 formed via new C–h⋯π contacts.
in (b) and (c), all hydrogens except those participating in the C–h⋯π contacts were omitted for clarity.
The 2-D supramolecular layer of 3 is formed via C–H⋯Cl hydrogen bonds [4(a)] (figure 3(b)). In
the hydrogen bonds, the hydrogens are from benzimidazole rings and methylene groups. The 2-D
supramolecular layers are further extended into a 3-D architecture via additional C–H⋯Cl hydrogen

JOurNAL OF COOrDINATION CHeMISTrY
15
bonds (figure 3(c)). In these hydrogen bonds, aromatic hydrogens from the mesitylene rings are
involved.
The 3-D supramolecular frameworks of 4 are formed via C–H⋯O hydrogen bonds (figure4(b))
between the benzimidazole rings and nitrates. The 3-D supramolecular frameworks of 5 (figure 5(c))
are formed via π⋯π interactions between benzene rings of the mesitylene units.
The 2-D supramolecular layer of 6 (figure 6(b)) is formed via C–H⋯π contacts [6] (table S2) between
hydrogens from methyl groups and π systems from benzimidazole rings. In addition, the 2-D supramo-
lecular layers are further extended into 3-D supramolecular networks via additional C-H⋯π contacts
(figure 6(c)) between benzimidazole rings.
3.4. The conformations of 1,3-bis(benzimidazol-1′-yl-methyl)mesitylene (L) and its metal
complexes
According to literature reports and our results reported here, the mesitylene-bridged bis-ben-
zimidazolyl ligand L can form two different conformations when coordinating to metal ions, a
cis-conformation (two benzimidazole rings lying on the same flank of the mesitylene plane) and a
trans-conformation (two benzimidazole rings lying on the opposing flanks of the mesitylene plane)
as shown in scheme 1.
When L adopts the cis-conformation, the metal complexes contain mainly five types of conforma-
tions (scheme 2): (1) the metallomacrocycle (I) formed by one ligand L, two metal ions and two halide
N
N
N
N
cis
M salts
N
N
N
N
N
N
N
N
N
N N
N N
X
X
N
M
M
M
X
M
N
N
N
N
M
M
N N
X
I
III
X = Br or I
II
N
N
O
N
N
N
N
N
N
N
N
N
Cu
N
M
Cu
O
N
N
N
Cu
Cu
O
N
N
N
N
N
N
Cu
N
Cu
N
N
O
N
N
N
N
O
O
N
Cu
N
M
N
N
N
N
N
Cu
N
Cu
N
O
N
N
N
IV
V
Scheme 2. the conformations of complexes formed by cis-ligand L and metal salts.

16
Q.-X. LIu eT AL.
N
N
N
N
trans
M salts
N
N
N
N
N M
N
M
N
N N
N
N
N
N
N
n
VI
N
N
n
VII
N
N
N
N
N
N
N
N
N
N
N
N
N
O
O
O
O M
M
C
C
N
C
C
O
O
N
N
O
O
N
N
N
N
N
N
N
N
n
n
IX
VIII
N
N
M
N N
M
N
N
N
N
N
N
N
N
M
N
N
N
N
M
X
Scheme 3. the conformations of complexes formed by trans-ligand L and metal salts.
ions (such as [Hg2LI2]I2 [21]); (2) the dimer with two metallomacrocycles (II) (such as [Cd2L2Br2]Br2 [22]),
in which each metallomacrocycle is similar to that of I; (3) the metallomacrocycle (III), formed by two L
and two metal ions; this type of complex contains an inversion center (such as 3, [Hg2L2]I4 [21], [Ag2L2]
(CF3SO3)2 [12] and [Ag2L2](ClO4)2 [23]); (4) the cage-like ball (IV) formed by four L and two metal ions
(such as 2 and [Cu2L4](ClO4)4 [12, 24]), in which an approximate symmetry plane is observed; (5) the
football-like cluster (V) formed by six L, nine Cu(II) ions and seven hydroxide ions (such as 1); this type
of complex contains many symmetry planes.
When L is in the trans-conformation, the metal complexes also contain five types of confor-
mations (scheme 3): (6) a 1-D zig-zag polymeric chain (VI) formed by L and metal ions (such as 6

JOurNAL OF COOrDINATION CHeMISTrY
17
and [HgLI2] [21]); (7) an (M3L2)n type of 2-D network layer (VII) formed by L and metal ions (such
as {[Ag3L2](ClO4)3}n [23]); (8) an (ML2)n type of 2-D network layer (VIII) formed by L and metal ions
(such as 4); (9) the (MLLA)n type of 2-D network layer (IX) formed by ligands and metal ions (such
as 5); (10) the M4L4 type of the metallomacrocycle (X) formed by four L and four metal ions (such
as [Hg4L4]Cl8 [25]).
The conformations of metal complexes based on bis-benzimidazolyl bidentate ligands with flexi-
ble linkers (such as alkanyl, oligoether and 1,2-bis(2′-ethoxy)phenyl) [7, 8, 17(f)] or semi-rigid linkers
(such as –CH2–benzene–CH2–, –CH2–trimethylbenzene–CH2– and –CH2–tetramethylbenzene–CH2–)
[16(a), 17(e)] have some differences. Their similar points are that these complexes contain some similar
conformations, such as the metallomacrocycle, 1-D polymeric chain, and 2-D layer. Their main differ-
ences are that complexes from the bis-benzimidazolyl ligands with semi-rigid linkers can form cage-like
conformations [2b, 12, 23, 24], and this may originate from the large steric hindrance of linkers and
semi-rigidity of ligands. By contrast, metal complexes from ligands bearing flexible linkers do not easily
form this type of complex.
On the whole, conformations of metal complexes based on bis-benzimidazolyl bidentate ligands
are related mainly to steric hindrance and sizes of linkers, the conformation of L, and metal ions. The
counter ions and the reaction conditions (such as the ratio of ligands with metal salts and solvents)
also have influence on the conformations of complexes.
3.5. Fluorescence emission spectra of 1,3-bis(benzimidazol-1’-yl-methyl)mesitylene (L) and
1–6
As indicated in figure 7, the fluorescence emission spectra of L and 1–6 in acetonitrile at room
temperature are obtained upon excitation at 245 nm (the fluorescence emission spectrum of 3 is
similar to that of 1, and the fluorescence emission spectrum of 5 is similar to that of 4). L shows
three weak emission bands from 280 to 320 nm, corresponding to intraligand transitions [26].
Complexes 1–6 exhibit analogous emission bands in same region, but they are stronger than that
of L, which should originate from the metal perturbed intraligand processes. In 4 and 6, a peak
near 285 nm disappears and it may be ascribed to the incorporation of metal-ligand coordination
interactions.
Figure 7. emission spectra of L, 1, 2, 4 and 6 at room temperature in Ch3Cn (5.0 × 10−6 mol l−1) solution.

18
Q.-X. LIu eT AL.
4. Conclusion
Six new copper(II), cobalt(II), zinc(II), cadmium(II), and manganese(II) complexes have been prepared and
characterized. Complex 1 is a football-like cluster formed by six L, nine copper(II) ions, eight chlorides,
and seven hydroxides. Complex 2 is a cage-like ball, in which one nitrate is in the middle of the cage
through two Co-O bonds. Complex 3 is a 24-membered metallomacrocycle formed by two L and two
Zn(II) ions. The 2-D layer with a 48-membered metallomacrocycle of 4 is formed via L and Cd(II) ions.
In 5, L and a terephthalate ion participate in coordination with Mn(II) ions to afford 2-D network layers.
The 1-D polymeric chain of 6 is formed via L and Co(II). In the crystal packing of 1–6, 2-D supramolecular
layers or 3-D supramolecular frameworks are formed via intermolecular weak interactions, including
hydrogen bonds, π–π interactions and C–H⋯π contacts. The mesitylene-bridged bis-benzimidazolyl
ligand L exhibits two different conformations (cis- and trans-) upon coordinating to metal ions. The metal
complexes based on cis- or trans- L each contain five types of conformations. The resultant structures
of these complexes provide valuable experimental data for crystal engineering and supramolecular
chemistry. Additionally, these cage-like or metallomacrocycle complexes suggest that they may have
potential applications in host–guest chemistry. Further studies on new metal-organic compounds from
these precursors and analogous ligands are underway.
Supplementary material
Tables of selected dihedral angles, π–π interactions, C–H⋯π contacts, and H-bonding geometry for 1–6. CCDC 1407640-
1407645 for 1–6 contain the supplementary crystallographic data for this article. These data can be obtained free of charge
from the Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by the National Natural Science Foundation of China [grant numbers 21172172 and
21572159]; Tianjin Natural Science Foundation [grant number 11JCZDJC22000]; and the Program for Innovative research
Team in university of Tianjin [grant number TD12-5038].
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