Complexation of different metals with a novel N-donor bridging receptor and Hirshfeld surfaces analysis

Article abstract of DOI:10.1016/j.ica.2012.11.010

A novel N-donor bridging receptor R: 4,4′-methanediylbis(2-ethyl-5- methyl-1H-imidazole) has been synthesized from 2-ethyl-4-methyl-1H-imidazole and formaldehyde in the presence of potassium hydroxide. This receptor then formed complexes with different transition metals ([Co(NO₃)₂, CoCl₂, Ni(NO₃)₂ and CuCl₂]) in different solvent systems and obtained five different complexes. Wherein, the complex formation of R with Co(NO₃)₂ resulted in two different structures in methanol and acetonitrile, respectively. A thorough structural investigation of the present receptor and the resulted five complexes show that the NH group of the receptor, the organic anions and solvent molecules play a key role in the construction of the five intriguing architectures. We also prepared molecular Hirshfeld surface and fingerprint plot for R as well as the five complexes, which revealed the influences of different metals to the coordinate behavior of R in terms of intermolecular interactions.

Full text of DOI:10.1016/j.ica.2012.11.010

Inorganica Chimica Acta 397 (2013) 1–9
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Complexation of different metals with a novel N-donor bridging receptor
and Hirshfeld surfaces analysis
⇑
Yang-Hui Luo, Guo-Gan Wu, Shu-Lin Mao, Bai-Wang Sun
College of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, PR China
a r t i c l e i n f o
a b s t r a c t
0
Article history:
Received 29 August 2012
Received in revised form 10 November 2012
Accepted 12 November 2012
Available online 29 November 2012
A novel N-donor bridging receptor R: 4,4 -methanediylbis(2-ethyl-5-methyl-1H-imidazole) has been
synthesized from 2-ethyl-4-methyl-1H-imidazole and formaldehyde in the presence of potassium
hydroxide. This receptor then formed complexes with different transition metals ([Co(NO
Ni(NO and CuCl ]) in different solvent systems and obtained five different complexes. Wherein, the
complex formation of R with Co(NO resulted in two different structures in methanol and acetonitrile,
3 2 2
) , CoCl ,
3
)
2
2
3 2
)
respectively. A thorough structural investigation of the present receptor and the resulted five complexes
show that the NH group of the receptor, the organic anions and solvent molecules play a key role in the
construction of the five intriguing architectures. We also prepared molecular Hirshfeld surface and fin-
gerprint plot for R as well as the five complexes, which revealed the influences of different metals to
the coordinate behavior of R in terms of intermolecular interactions.
Keywords:
N-donor bridging receptor
Complexation
Crystal structure
Hirshfeld surface
Ó 2012 Elsevier B.V. All rights reserved.
1
. Introduction
In recent years, great attentions have been paid to the construc-
that summarises the crystal packing into a single 3D surface, and
the surface can reduced to a 2D fingerprint plot, which summarise
the complex information on intermolecular interactions present in
molecular crystals [15]. The principles of Hirshfeld surface and fin-
gerprint plot are reported in other literature [14].
tion of metal–organic frameworks (MOFs) by using flexible
N-donor bridging receptors, such as 1,2-bis(4-pyridyl)ethane, 1,2-
bis(imidazol-1-ylmethyl)benzene, 2,2 -bis(1H-imidazolyl)ether),
0
In order to further investigate the coordinate behavior of N-do-
nor bridging receptors, we synthesized a novel N-donor bridging
0
4
,4 -bis(1,2,4-triazol-1-ylmethyl)biphenyl, 1,3-bis(1,2,4-triazol-1-
0
yl)-propane, and so on, for their structural/topological diversities
as well as potential application as functional materials [1–7]. These
N-donor bridging receptors are featuring bis-imidazole or bis-tria-
receptor R: 4,4 -methanediylbis(2-ethyl-5-methyl-1H-imidazole)
by using 2-ethyl-4-methyl-1H-imidazole and formaldehyde in
the presence of potassium hydroxide (Scheme 1), and complexated
zole structures which connected by –CH
2
– or –O–CH
2
– spacers. It
3 2 2 3 2 2
this receptor with Co(NO ) , CoCl , Ni(NO ) and CuCl in acetoni-
is these spacers that making these receptors became more confor-
mational changes, allowing the receptors to bend or rotate freely
when interacting with metal centers so as to conform to the coor-
dination geometries of metal ions [8]. Usually, the final crystal
architectures of MOFs are depend on the combination of several
factors such as the nature of organic receptors, the solvent system,
temperature, the coordination geometry of metal ions, organic an-
ions, and so on [9–12].
Recently, the prediction and computation of molecular crystal
structures through the aspect of intermolecular interactions, for
the purpose of studying the crystal structural features, crystal de-
sign and crystal engineering, also have aroused much attention
trile and methanol at temperature of 25 and 50 °C, respectively, for
the purpose of investigating the influence of such factors as the
solvent system, temperature, the coordination geometry of metal
ions and organic anions on the final crystal architectures of the
resulted MOFs. The structures of the present receptor R and the re-
0
sulted MOFs: (1). {CoNO
H-imidazole) ](NO
)ꢀ2(H
(2-ethyl-5-methyl-1H-imidazole)
nediylbis(2-ethyl-5-methyl-1H-imidazole)
3
[4,4 -methanediylbis(2-ethyl-5-methyl-1
0
2
3
2
O)} (2). {CoNO
](NO
3
[4,4 -methanediylbis
0
2
3
)};(3): {CoCl
2
[4,4 -metha-
0
2
]}; (4): {NiNO
3
[4,4 -
methanediylbis(2-ethyl-5-methyl-1H-imidazole)
2
]
3
(NO )} and
0
(5): {Cu(C
2
O
4
) [4,4 -methanediylbis(2-ethyl-5-methyl-1H-imidaz-
ole) ] (H O)
2
2
3
} are characterized by single-crystal X-ray diffraction,
[
13–15]. The main approach was through Hirshfeld surfaces [16],
infrared spectra (IR) and elemental analyses. The crystallography
dates of complexes (3–5) were reported in our previously work
[16]. In this work, we compared their structures with (1) and (2),
and investigated the influences of different metals to the receptor
in terms of intermolecular interactions by using Hirshfeld surfaces
and fingerprint plots.
which serves as a powerful tool for elucidating molecular crystal
structures [17]. Hirshfeld surfaces is a space partitioning construct
⇑
Corresponding author. Tel./fax: +86 25 52090614.
E-mail address: chmsunbw@seu.edu.cn (B.-W. Sun).
0
020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.11.010

2
Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
Scheme 1. Preparation of receptor R and complexation of it with different metal salts.
400 cm–1, with the samples in the form of potassium bromide pel-
2
. Experimental
lets. Elemental analyses were performed by a Vario-EL III elemen-
tal analyzer for carbon, hydrogen, and nitrogen of these
compounds.
2.1. Materials and methods
All reagents are obtained commercially, and used without fur-
ther purification, 2-ethyl-4-methyl-1H-imidazole (purity P 98%,
CAS number: 931-36-2) was purchased from Alfa Aesar and used
2.3. X-ray crystallographic study
as received, formaldehyde, potassium hydroxide and Co(NO
6H O were purchased from NanJing WanQing Chemical Glassware
Instrument Co. Ltd. and used as received.
3 2-
)
The single-crystal X-ray diffraction data of the receptor (R) and
ꢀ
2
complexes (1) and (2)were collected at 293 K with graphite-mono-
chromated Mo K radiation (k = 0.071073 nm), a Rigaku SCXmini
diffractometer with the -scan technique were used [17]. The lat-
a
x
2
.2. Physical measurements
tice parameters were integrated using vector analysis and refined
from the diffraction matrix, the absorption correction was carried
out by using BRUKER SADABS program with multi-scan method. A sum-
mary of crystallographic data, data collection, and refinement
Infrared spectras (IR) were recorded on a SHIMADZU IR pres-
tige-21 FTIR-8400S spectrometer in the spectral range 4000–
Table 1
Crystal data and structure refinement for R and complexes (1–5).
Compound
R
1
2
3
4
5
Formula
C
12
H
20
N
4
C
28
H
47CoN10
O
7
C
26
H
40CoN10
O
6
C
26
H
44Cl
4
Co
N
2 8
O
2
C
15H2
6
CuN
4
O
7
26 6
C H40NiN10O
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
232.33
monoclinic
Cc
15.1991(14)
10.2064(11)
8.8579(9)
90
96.8420(10)
90
662.69
monoclinic
P21/c
9.6160(10)
9.6141(11)
18.5089(18)
90
92.7990(10)
90
1709.1(3)
2
647.61
monoclinic
C2/c
37.310(3)
9.3410(10)
19.17010(18)
90
104.6090(10)
90
6465.1(9)
8
760.35
monoclinic
P2(1)/m
437.94
monoclinic
P2(1)/c
647.39
monoclinic
C2/c
37.163(3)
9.4190(10)
19.0191(18)
90
104.4700(10)
90
8.4012(7)
12.1711(13)
23.167(2)
7.4400(8)
90
107.3040(10)
90
2002.9(4)
4
1.452
12.1591(11)
8.5944(8)
90
98.88(3)
90
829.4(3)
4
1.558
a
(°)
b (°)
(°)
c
3
V (Å )
1364.3(2)
4
1.131
6446.3(11)
8
1.334
Z
D
calc (Mgm 3
ꢁ
)
1.288
1.331
T (K)
l
293(2)
0.07
293(2)
0.552
293(2)
0.585
293(2)
0.419
293(2)
1.133
293(2)
0.656
(mm 1
ꢁ
)
Crystal dimensions
0.2 ꢂ 0.12 ꢂ 0.10
0.36 ꢂ 0.30 ꢂ 0.27
0.35 ꢂ 0.30 ꢂ 0.28
0.25 ꢂ 0.20 ꢂ 0.20
0.35 ꢂ 0.18 ꢂ 0.12
0.40 ꢂ 0.31 ꢂ 0.30
Goodness-of-fit (GOF) on F2
1.032
1.046
0.9
1.187
1.056
1.079
R
R
1
, wR
, wR
2
[(I > 2
(all data)
r
(I)]
0.0731, 0.1506
0.1231, 0.1727
0.0675, 0.1987
0.0938, 0.2140
0.0682, 0.1423
0.1847, 0.1878
0.2107, 0.4867
0.2227, 0.4921
0.0471, 0.0647
0.0929, 0.0699
0.0526, 0.0905
0.1318, 0.1018
1
2

Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
3
parameters for (R), (1) and (2) as well as complexes (3–5) were
aqueous solution, then formaldehyde (37% in H
2
O) was added
summarized in Table 1. The structures of them were solved by
full-matrix least-squares methods on all F data, and used the SHEL-
XS-97 and SHELXL-97 programs [18] for structure solution and struc-
ture refinement respectively. Reliability factors were defined as
dropwising. The resulting turbid mixture was later made alkaline
with a concentrated potassium hydroxide solution until a pH of
13 was reached. Then the reaction mixture was stirred for 5 days
at room temperature in a closed vessel and resulted in a white so-
lid of R. The white solid was collected by filtration, washed with
acetonitrile and diethyl ether, and air-dry at room temperature.
Yield 86%, based on 2-ethyl-5-methylimidazole. Mp 134 °C. Ele-
mental analysis for R, Anal. Calc.: C, 67.207; N, 24.11; H, 8.67.
2
R
1
=
R
R
(|F
w(F
o
| ꢁ |F
c
|)/
R
|F
o
|
and the function minimized was
2
2 2
4 ½
Rw = [
o
ꢁ F
c o
) /w(F ) ] , where in the least-squares calcula-
tion the unit weight was used. All non-hydrogen atoms were re-
fined anisotropically, and hydrogen atoms were inserted at their
calculated positions and fixed at their positions [19] The molecular
graphics were prepared by using the DIAMOND program [20] and
mercury [21].
ꢁ
1
Found: C, 67.21; N, 24.11; H, 8.66%. IR (KBr pellet, cm ): 3404,
3087, 2971, 2917, 1610, 1530, 1460, 1430, 1328, 1072, 1043, 970.
0
Synthesis of complex (1) {CoNO
-methyl-1H-imidazole) ] (NO ) (H
Co(NO
ꢀ6H
3
[4,4 -methanediylbis(2-ethyl-
O)}: It was obtained by adding
5
2
3
2
3
)
2
2
O and the receptor R at stoichiometric ratio of 1:2 to
2.4. Hirshfeld surfaces calculations
a certain amount of acetonitrile at temperature of 25 °C under con-
tinuous stirring. After stirring for 30 min, the solution which re-
sults from the mixture was filtered off and allowed to evaporate
at room temperature. Single crystals of (1) were grown from the
solution by slow evaporation at room temperature within 5 days.
Yield 75%, based on Co. Elemental analysis for (1), Anal. Calc.: C,
Molecular Hirshfeld surfaces calculations were performed by
using the CRYSTALEXPLORER [22] program. When the cif files of the
six compounds are read into the CRYSTALEXPLORER program for analy-
sis, all bond lengths to hydrogen were automatically modified to
0
0
typical standard neutron values (C–H = 1.083 ÅA and N–H = 1.009 ÅA ).
The molecular Hirshfeld surfaces of 2-ethyl-5-methyl-1H-
imidazole were generated using a standard (high) surface resolu-
5
0.75; N, 21.14; H, 7.15. Found: C, 50.748; N, 21.142; H, 7.16%. IR
ꢁ1
(
KBr pellet, cm ): 3310, 3120, 2860, 2731, 1600, 1520, 1450,
1
420, 1320, 1078, 1023, 960, 820.
Synthesis of complex (2) {CoNO [4,4 -methanediylbis(2-ethyl-
3
tion with the 3D dnorm surfaces are mapped over a fixed colour
0
0
scale of ꢁ0.42 (red) to 1.6 ÅA (blue), the Shape index mapped in
5
2 3
-methyl-1H-imidazole) ] (NO )}: It was obtained by adding
the colour range of 0.7–2.5 and Curvedness in the range of 0.72–
Co(NO
3
)
2
ꢀ6H O and the receptor R at stoichiometric ratio of 1:2
2
2
0
.4. The 2D fingerprint plots displayed by using the standard
0
.6–2.6 ÅA view with the d and d distance scales displayed on
e i
to a certain amount of methanol at temperature of 50 °C under
continuous stirring. After refluxed for about 30 min, the solution
which results from the mixture was filtered off and allowed to
evaporate at room temperature. Single crystals of (2) were grown
from the solution by slow evaporation at room temperature within
the graph axes.
2.5. Synthesis and characterization
5
days. Yield 70%, based on Co. Elemental analysis for (2), Anal.
The synthesis procedure of the receptor was shown in Scheme 1:
-ethyl-5-methylimidazole was added to a vigorously stirred
Calc.: C, 48.22; N, 21.63; H, 6.22. Found: C, 48.23; N, 21.61; H,
2
Fig. 1. (a) Molecular structure and numbering scheme of receptor R; (b) N–Hꢀ ꢀ ꢀN hydrogen bonds motifs of receptor R (H atoms are omitted for clarity); (c) pack diagram
viewed along b-axis.

4
Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
6
1
.20%. IR (KBr pellet, cmꢁ1): 3315, 3122, 2872, 2733, 1630, 1550,
460, 1415, 1300, 1084, 1025, 953, 820, 710.
3.2. Crystal structure of complex (1)
The synthesis procedures of complex (3–5) are reported in our
The complex (1) crystallizes as blue block crystals in the mono-
clinic Pc space group with Z = 2, the asymmetric unit (ASU) consist-
ing of a polycation which composed by a Co ion, a nitrate anion
previously work [16].
. Results and discussion
II
and two receptor R, a dissociative nitrate anion and two solvent
3
II
water molecules (Fig. 2a). For the polycation, the Co ion shows a
distorted octahedral geometry formed by four N atoms from two
3.1. Crystal structure of receptor R
0
4
,4 -methanediylbis(2-ethyl-5-methyl-1H-imidazole)
2
receptors
and two O atoms from the chelating nitrate anion. The dihedral an-
gles between two imidazole planes of the receptors in complex (1)
The receptor R crystallizes as colourless prism crystals in the
monocilinc Cc space group with Z = 4, the molecular structure of
R was shown in Fig. 1a, it is composed of two 2-ethyl-5-methyl-
H-imidazole which connected by a –CH – group, and the two 2-
2
ethyl-5-methyl-1H-imidazole molecules are almost perpendicular
with each other with the dihedral angle found to be 89.48°, and
were changed to 50.41° and 51.49°, which due to the coordination
II
capacity of the Co ion. But the angles which containing –CH
2
–
1
group are found to be 113.15° and 113.53°, which shown no
changes when compared with R. The angles between the coordi-
II
nated N group and Co ion are found to be N2–Co1–N7 = 88.82°,
2
the angle which containing –CH – group is 113.72°. Every mole-
and N3–Co1–N5 = 89.89°, while the angle between the chelating
cule in the crystal connected with four molecules through centro-
0
II
nitrate anion and Co ion is O2–Co1–O3 = 57.04°.
symmetric N–Hꢀ ꢀ ꢀN (distance of 2.895 ÅA ) and Nꢀ ꢀ ꢀH–N (distance of
0
In the crystal structure, the two solvent water molecules con-
nect the polycations into an infinite 1D chain structure along the
2
.843 ÅA ) hydrogen bonds interactions (Fig. 1b), and the molecules
are packed by ꢀ ꢀ ꢀABABꢀ ꢀ ꢀ fashion along the b-axis (Fig. 1c).
Fig. 2. (a) Molecular structure and numbering scheme of complex (1); (b) 1D chain diagram of (1) (H atoms and hydrogen bonds are omitted for clarity); (c) 1D chain diagram
of (1) with hydrogen bonds; (d) Connecting motif of different 1D chains (H atoms and hydrogen bonds are omitted for clarity); (e) Pack diagram of complex (1) viewed along
c-axis.

Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
5
0
a-axis, through N–Hꢀ ꢀ ꢀO (distance of 2.921 ÅA ) and Oꢀ ꢀ ꢀH–O (dis-
hydrogen bonds interactions along the b-axis (Fig. 3d). The crystal
structure of complex (2) is almost identical with (5).
0
tance of 2.901 ÅA ) hydrogen bonds interactions with NH groups
and chelating nitrate anions, respectively (Fig. 2b and c). The disso-
ciative nitrate anion, which distributed along the two sides of the
We further discussed here the additional structural analysis of
previously reported complexes (3) and (4). The molecular struc-
tures of them were shown in Fig. 4, and they all have only one
coordinated R for the metal ions duo to the strong coordination
ability of chloridion and oxalate, respectively. Complex (3) form
grand shape layer structure by N–Hꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀCl hydrogen
bonds interactions (Fig. 4a), and the dihedral angle between the
two imidazole planes is 173.8°, which is much larger than the cor-
responding angles in R, (1), (2) and (5) and is attribute to the steric
hindrance of chloridion. Thus we get to the conclusion that the or-
ganic anions do much influence not only to the final crystal archi-
tectures of the resulted MOFs, but also the coordinate receptors in
the corresponding MOFs. In complex (4), we use oxalate as co-
1
D chain evenly, connected the different 1D chains into 2D struc-
0
tures through N–Hꢀ ꢀ ꢀO (distance of 2.954 ÅA ) and Oꢀ ꢀ ꢀH–O (distance
0
of 3.029 ÅA ) hydrogen bonds interactions with NH groups and sol-
vent water molecules, respectively (Fig. 2d).
When viewed from the c-axis (Fig. 2e), the polycation packed in
the ‘‘head to head’’ and ‘‘end to end’’ fashion: the chelating nitrate
anions heads are overlap and the receptor ends form round struc-
tures, the dissociative nitrate anions then inset at the ‘‘head’’
position.
3.3. Crystal structure of complex (2)
II
receptor to coordinate with Cu ion. The dihedral angle between
the two imidazole planes was found to be 47.75°, which is almost
identical with corresponding angles in R, (1), (2) and (5). In the
crystal structure, every two molecules mate together into a unit
through N–Hꢀ ꢀ ꢀO hydrogen bonds interactions, the unit then con-
nected by a part of solvent water molecules into 1D chain structure
The complex (2) crystallizes as blue prism crystals in the mono-
clinic C/2c space group with Z = 8, the ASU consisting of a polyca-
tion and a dissociative nitrate anion (Fig. 3a). The polycation
shows the similar geometry with complex (1): the angles which
2
containing –CH – group are found to be 113.15° and 113.53°; the
(Fig. 4b and c). The different 1D chain structures then further con-
imidazole planes of the receptors show dihedral angles of 54.40°
II
nected by the other solvent water molecules into intricate crystal
structure (Fig. 4d).
and 50.23°; the angles between the coordinated N group and Co
ion are found to be N1–Co1–N3 = 90.16°, and N5–Co1–
N7 = 88.78°, and the angle between the chelating nitrate anion
II
and Co ion is O2–Co1–O3 = 56.23°.
3.4. Molecular Hirshfeld surfaces
But the crystal structure of (2) is significant different from (1).
The polycations in (2) formed 1D double-chain structure through
Hirshfeld surface is a useful tool for describing the surface char-
0
N–Hꢀ ꢀ ꢀO (distance of 3.053 ÅA ) hydrogen bonds interactions be-
tween the receptors and the chelating nitrate anion (Fig. 3b and
c), the double-chain units then packed paralleled with each other
and stabilized by the dissociative nitrate anion through N–Hꢀ ꢀ ꢀO
acteristics of the molecules. The molecular Hirshfeld surface (dnorm
Shape index and Curvedness) of 4,4 -methanediylbis(2-ethyl-5-
methyl-1H-imidazole) in the present six compounds were shown
2
in Fig. 5.
,
0
Fig. 3. (a) Molecular structure and numbering scheme of complex (2); (b) 1D chain diagram of (1) (H atoms and hydrogen bonds are omitted for clarity); (c) 1D chain diagram
of (2) with hydrogen bonds; (d) Connecting motifs of different 1D chains.

6
Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
d
norm surface is used for the identification of very close intermo-
tions to the total Hirshfeld surfaces, except complex (3) (as been
shown in Table 2).
The Shape index is the most sensitive to very subtle changes in
surface shape, the red triangles on them (above the plane of the
molecule) represent by concave regions indicating atoms of the
lecular interactions. The value of dnorm is negative or positive when
intermolecular contacts are shorter or longer than r
Waals (vdW) radii), respectively. The dnorm values are mapped onto
the Hirshfeld surface by using a red–blue–white colour scheme:
where red regions correspond to closer contacts and negative dnorm
value; the blue regions correspond to longer contacts and positive
vdW
(van der
p
ꢀ ꢀ ꢀstacked molecule above them, and the blue triangles represent
by convex regions indicating the ring atoms of these molecule in-
dnorm value; and the white regions correspond to the distance of
side these surfaces. In the case of the present six compounds, the
contacts is exactly the vdW separation and with a dnorm value of
zero. The larger red regions on dnorm surface of R correspond to
strong N–Hꢀ ꢀ ꢀN hydrogen bonds interactions, and these interac-
tions comprise 17.7% to the total Hirshfeld surfaces (shown in
Fig. S1 and summarised in Table 2). While for the other five com-
plexes, the most closet interactions refer to the Metal–N interac-
tions, as they are indicated by the deep red regions on dnorm
surface, near the metal atoms. The small red regions on the dnorm
red triangles are referring to the C–Hꢀ ꢀ ꢀ
p interaction, and the infor-
mation convey by Shape index are consisted with the 2D fingerprint
plots (Table 2).
The Curvedness is the measurement of ‘‘how much shape’’, the
flat areas of the surface are correspond to low values of curvedness,
while sharp curvature areas are correspond to high values of curv-
edness and usually tend to divide the surface into patches, which
indicating interactions between neighboring molecules. The large
surfaces are corresponding to the significant C–Hꢀ ꢀ ꢀ
and they are clear shown that complexation of receptor R with me-
tal ions lead to the increasing of the percentage of C–Hꢀ ꢀ ꢀ interac-
p
interactions,
flat region which delineated by a blue outline refer to the
stacking interactions. The Curvedness of the present six compounds
indicate no stacking interactions observed.
ꢀ ꢀ ꢀ
p
ꢀ ꢀ ꢀ
p
p
p p
Fig. 4. (a) Connecting diagram of complex (3) (H atoms are omitted for clarity); (b) 1D chain motif of complex (4) (H atoms and hydrogen bonds are omitted for clarity); (c)
D chain diagram of (4) with hydrogen bonds; (d) Connecting motif of different 1D chains in (4).
1

Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
7
0
Fig. 5. Molecular Hirshfeld dnorm surfaces, Shape index and Cvrvedness of 4,4 -methanediylbis(2-ethyl-5-methyl-1H-imidazole)
2
in R and complexes (1–5).
The 2-D fingerprint plots complement the Hirshfeld surfaces,
they are quantitatively summarizing the nature and type of inter-
molecular contacts experienced by the molecules in the crystal.
They are colored with a range from blue (relatively few points)

8
Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
Table 2
in the 2-D fingerprint plots, as well as Fig. S1), but the complexa-
tion with metal ions leads to reduction of the H–H percentage to
the total Hirsheld surfaces. For compounds R - (5), the percentage
of H–H contacts is 74.3%, 57.7% (56.6%), 57.1% (57.9%), 64.5%,
58.4%, and 56.8% (58.9%), respectively.
N–H interaction (Fig. S2) is one of the most significant contacts
for these compounds. For receptor R, N–H interaction is indicated
by two large spikes (Fig. 6), they are also characteristic of symmet-
rical N–Hꢀ ꢀ ꢀN hydrogen bond interaction. For the other five com-
plexes, the percentage of N–H interactions decreased dramaticlly,
from 17.7% in R to 10.3% (10%), 10.5% (9.6%), 6.8%, 8.3% and
0
Summary of the various contact contributions to the 4,4 -methanediylbis(2-ethyl-5-
methyl-1H-imidazole) Hirshfeld surface area in receptor R and complexes (1–5).
2
H–H N–H C–H O–H H–M N–N N–C N–O C–C H–Cl
R
74.3
57.7
56.6
57.1
57.9
64.5
58.4
56.8
58.9
17.7
10.3
10
8.1
0
0
0
0
0
0
0
0
0
0
0
0
0
1.2
1
0
0
0
0
0
0
0
10.2
0
0
1
1
2
2
3
4
5
5
a
9.9 17.9 0.3
10.7 18.3 0.2
0.3
0.3
0.2
0.2
0.5
0.5
0.3
0.3
0.7
0.8
0.7
0.7
0
0.5
0.8
0.7
b
a
b
10.5 11.2 17.3 0.3
9.6
6.8
8.3
9.4 19.4 0.3
6.4 1.1
9.2 17.6 0.4
0
3
1.9
0.9
0
a
b
10.3 10.8 18.2 0.3
9.5 9.1 18.8 0.2
0.1
0
1
0.3% (9.5%) in complexes (1–5), respectively. This phenomenon
may attribute to the existence of O–H interactions (Fig. S3). For
complexes (1), (2), (4) and (5), the percentage of O–H interactions
are all larger than N–H interactions, while for complex (3), the low
percentage of O–H and N–H contacts attribute to the existence
high percentage of H–Cl contacts (10.2%).
through green (moderate points) to red (many points). Shown in
0
Fig.
6
are the total fingerprint plots of 4,4 -methanediylbis
(
2
2-ethyl-5-methyl-1H-imidazole) in the present six crystals,
wherein, crystal (1), (2) and (5) contain two molecules of 4,
Apart from those above, the presence of H–M, N–O, C–C and N–
N contacts are observed, and they are all summarized in Table 2.
The most closet contacts for receptor R in complexes (1–5) (N–M
contacts) cannot be included in Table 2 due to the fact that Hirsh-
feld analysis is only concerned with intramolecular interactions
and intermolecular interactions should not be considered. The
0
4
2
-methanediylbis(2-ethyl-5-methyl-1H-imidazole) and they are
identified as a and b. Fig. 6 clearly shown the difference of intermo-
0
lecular contacts experienced by the 4,4 -methanediylbis(2-ethyl-5-
2
methyl-1H-imidazole) molecules. The main intermolecular con-
tact is H–H contact (shown in the middle of the scattered point
0
Fig. 6. 2-D fingerprint plots of 4,4 -methanediylbis(2-ethyl-5-methyl-1H-imidazole)
2
in R and complexes (1–5), the two coordinate receptors in one complex are
distinguished as ‘‘a’’ and ‘‘b’’.

Y.-H. Luo et al. / Inorganica Chimica Acta 397 (2013) 1–9
9
bond length of N–M contacts for complexes (1–5) are found to be
References
2
2
.091 (2.085), 2.081 (2.083, 2.087, 2.107), 2.017, 1.975 (1.997), and
.056 (2.055, 2.047, 2.071) ÅA , respectively. It is interesting that for
0
[
1] D.N. Dybtsev, H. Chun, S.H. Yoon, J. Am. Chem. Soc. 126 (2004) 32;
b) B. Kesanli, Y. Cui, M.R. Smith, E.W. Bittner, B.C. Bockrath, W.B. Lin, Angew.
(
the two coordinate N atoms of one receptor, only (3) shows the
identical bond length between Co ion and the two coordinate N
atoms of R. For the three complexes with two coordinate receptors,
only complex (1) shows identical two kinds of bond length be-
tween Co ion and the two coordinate receptors (the two N–M bond
length for one receptor are different), which may attribute to the
existence of water molecules.
Chem., Int. Ed. 44 (2005) 72;
(c) S.R. Batten, R. Robson, Angew. Chem., Int. Ed. 37 (1998) 1460;
(
(
d) Y.Y. Liu, J.F. Ma, J. Yang, Z.M. Su, Inorg. Chem. 46 (2007) 3027;
e) J.-R. Li, R.J. Kuppler, H.-C. Zhou, Chem. Soc. Rev. 38 (2009) 1477.
[
[
2] (a) B. Oelkers, A. Venker, J. Sundermeyer, Inorg. Chem. 51 (2012) 4636;
(b) J.D. Lin, J.W. Cheng, S.W. Du, Cryst. Growth Des. 8 (2008) 3345;
(c) J.J. Perry, G.J. McManus, M.J. Zaworotko, Chem. Commun. (2004) 2534;
(
(
d) C. Janiak, Dalton Trans. (2003) 2781;
e) J.P. Zhang, X.M. Chen, Chem. Commun. (2006) 1689.
3] (a) N.L. Rosi, J. Kim, M. Eddaoudi, B.L. Chen, M. O’Keeffe, O.M. Yaghi, J. Am.
Chem. Soc. 127 (2005) 1504;
(
b) R. Matsuda, R. Kitaura, S. Kitagawa, Y. Kubota, R.V. Belosludov, T.C.
4
. Conclusion
Kobayashi, H. Sakamoto, T. Chiba, M. Takata, Y. Kawazoe, Y. Mita, Nature 436
(
(
2005) 238;
c) L. Pan, D.H. Olson, L.R. Ciemnolonski, R. Heddy, J. Li, Angew. Chem., Int. Ed.
5 (2006) 616.
In conclusion, the crystal structure of a new N-donor bridge
4
0
receptor R: 4,4 -methanediylbis(2-ethyl-5-methyl-1H-imidazole)
2
[4] S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem., Int. Ed. 43 (2004) 2334.
[5] L. Pan, M.B. Sander, X.Y. Huang, J. Li, M. Smith, E. Bittner, B. Bockrath, J.K.
Johnson, J. Am. Chem. Soc. 126 (2004) 1308.
6] D.J. Tranchemontagne, J.L. Mendoza-Cortes, M. O’Keeffe, O.M. Yaghi, Chem.
Soc. Rev. 38 (2009) 1257.
and five complexes (1–5) of it have been synthesized and charac-
terized successfully. The molecules in R are packed by ꢀ ꢀ ꢀABABꢀ ꢀ ꢀ
fashion, and every two molecules of R coordinated to one metal
ion duo to the present of nitrate ion, while chloride ion and the
existence of co-liangd result in single coordination of receptor.
The water molecules not only play a key role to the final crystal
architectures of the resulted MOFs but also affect the metal–recep-
tor bond length.
The molecular Hirshfeld surface and fingerprint plots of R and
complexes (1–5) revealed that the complexation with transition
metal ions results in the reduction of H–H and N–H contacts in
receptor, and leads to strengthening of C–H and O–H contacts.
[
[7] (a) J. Yang, B. Li, J.-F. Ma, Y.-Y. Liu, J.-P. Zhang, Chem. Commun. 46 (2010) 8383;
b) H. Wu, J. Yang, Z.-M. Su, S.R. Batten, J.-F. Ma, J. Am. Chem. Soc. 133 (2011)
1406.
(
1
[
8] (a) X.J. Li, X.-Y. Wang, S. Gao, R. Cao, Inorg. Chem. 45 (2006) 1508;
(b) X.Y. Lan, S.L. Li, Y.M. Fu, Y.H. Xu, L. Li, Z.M. Su, Q. Fu, Dalton Trans. (2008)
6
796;
c) D. Niu, J. Yang, J. Guo, W.Q. Kan, S.Y. Song, P. Du, J.F. Ma, Cryst. Growth Des.
2 (2012) 2397.
[9] (a) K.A. Hirsch, S.R. Wilson, J.S. Moore, Inorg. Chem. 36 (1997) 2960;
b) Z. Ma, B. Moulton, J. Chem. Crystallogr. 39 (2009) 913.
10] L. Carlucci, G. Ciani, P. Macchi, D.M. Proserpio, A. Sironi, Chem. Commun.
1997) 631.
(
1
(
[
(
[
[
11] J. Yang, J.F. Ma, Y.Y. Liu, J.C. Ma, S.R. Batten, Cryst. Growth Des. 8 (2008) 4383.
12] (a) C.-P. Li, M. Du, Chem. Commun. (2011) 5958;
M. Chen, S.-S. Chen, Cryst. Growth Des. 11 (2011) 1901.
[13] J.J. McKinnon, D. Jayatilaka, M.A. Spackman, Chem. Commun. (2007) 3814.
Acknowledgements
[
14] A.L. Rohl, M. Moret, W. Kaminsky, K. Claborn, J.J. McKinnon, B. Kahr, Cryst.
Growth Des. 8 (2008) 12.
15] Y.H. Luo, C.G. Zhang, B. Xu, B.W. Sun, CrystEngComm 14 (2012) 6860.
16] (a) Y.H. Luo, X.M. Qian, G. Gao, J.F. Li, S.L. Mao, Acta Crystallogr., Sect. E 67
(2011) m172;
This work has been supported by the prospective joint research
project of Jiangsu Province (SBY201220255) and the National
Science Foundation For Young Scholars of China (31100055).
[
[
(
(
(
(
b) X.M. Qian, Y.H. Luo, J.F. Li, S.L. Mao, G. Gao, Acta Crystallogr., Sect. E 67
2011) m575;
c) G. Gao, S.L. Mao, X.M. Qian, Y.H. Luo, J.F. Li, Acta Crystallogr., Sect. E 67
2011) m212.
Appendix A. Supplementary material
[
[
17] Rigaku, CRYSTALCLEAR, Version 14.0. Rigaku Corporation, Tokyo, Japan, 2005.
18] M. Sheldrick, SHELXS97: Programs for Crystal Structure Analysis, University of
Göttingen, Germany, 1997.
CCDC 888758, 892183 and 888760 contain the supplementary
crystallographic data for receptor R and complexes (1) and (2),
respectively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at http://dx.doi.org/10.1016/
j.ica.2012.11.010.
[
[
19] Y.H. Luo, Q. Zhou, B.W. Sun, J. Chem. Res. (2012) 505.
20] K. Brandenburg, DIAMOND
: Crystal and Molecular Structure Visualization,
Version 3.1b. Crystal Impact GbR, Bonn, Germany, 2006.
[21] MERCURY 2.3 Supplied with Cambridge Structural Database, CCDC: Cambridge,
UK, 2003–2004.
22] S.K. Wolff, D.J. Grimwood, J.J. McKinnon, D. Jayatilaka, M.A. Spackman,
CrystalExplorer 2.0., University of Western Australia, Perth, Australia, 2007.
[