The structures of three Hg2X4L2 macrocycles {X = Cl, Br and I, and L = 1,2-bis[4-(pyridin-3-yl)phenoxy]-ethane} assembled from ether-bridged dipyridyl ligands

Article abstract of DOI:10.1107/S0108270112019075

The new ether-bridged dipyridyl ligand 1,2-bis-[4-(pyridin-3-yl)phen-oxy] ethane (L) has been used to synthesize three isostructural centrosymmetric binuclear Hg^II macrocycles, namely bis-{-1,2-bis-[4-(pyridin-3-yl) phen-oxy]ethane-² N:N′}-bis-[dichloridomercury(II)], [Hg ₂Cl₄(C₂₄H₂₀N₂O ₂)₂], and the bromido, [Hg2Br4(C₂₄H ₂₀N₂O₂)₂], and iodido, [Hg ₂I₄(C₂₄H₂₀N₂O ₂)₂], analogues. The Hg atoms adopt a highly distorted tetra-hedral coordination environment consisting of two halides and two pyridine N-donor atoms from two bridging ligands. In the solid state, the macrocycles form two-dimensional sheets in the bc plane through noncovalent Hg...X and X...X (X = Cl, Br and I) inter-actions.

Full text of DOI:10.1107/S0108270112019075

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
few reports on flexible ether-bridged dipyridyl ligands. In
order to investigate further the influence of factors such as the
terminal groups of the ligand and the coordinated metal ions
on the topologies and properties of supramolecular
compounds, we studied the design and synthesis of a new,
flexible, ether-bridged dipyridyl ligand, 1,2-bis[4-(pyridin-3-
yl)phenoxy]ethane (L). Three new macrocycles have been
synthesized based on L and the inorganic salts HgX2 (X = Cl,
Br and I), viz. [Hg2Cl4L2], (I), [Hg2Br4L2], (II), and [Hg2I4L2],
(III). The X-ray crystal structures show that the three
ISSN 0108-2701
The structures of three Hg2X4L2
macrocycles {X = Cl, Br and I, and
L = 1,2-bis[4-(pyridin-3-yl)phenoxy]-
ethane} assembled from ether-bridged compounds are isostructural. We report here the inter-
molecular interactions in the lattices of the three com-
pounds.
dipyridyl ligands
Dan Wu, Na Qin, Qi-Kui Liu, Jian-Ping Ma and Yu-Bin
Dong*
College of Chemistry, Chemical Engineering and Materials Science, Shandong
Normal University, Jinan 250014, People’s Republic of China
Correspondence e-mail: yubindong@sdnu.edu.cn
Received 24 February 2012
Accepted 27 April 2012
Online 12 May 2012
The new ether-bridged dipyridyl ligand 1,2-bis[4-(pyridin-3-
yl)phenoxy]ethane (L) has been used to synthesize three
isostructural centrosymmetric binuclear HgII macrocycles,
namely bis{ꢀ-1,2-bis[4-(pyridin-3-yl)phenoxy]ethane-ꢁ2N:N0}-
The three isostructural compounds crystallize in the triclinic
space group P1. The unit cells have been chosen in a similar
fashion in order to facilitate the structural comparison. The
unit cell of (III) became nonstandard (cell setting I, but b > c >
a). As shown in Fig. 1, each compound contains centrosym-
metric macrocycles comprised of two ligands bridging two
HgX2 moieties. The HgII centre lies in a highly distorted
tetrahedral coordination environment defined by two N-atom
donors from two pyridine rings and two coordinated Xꢁ
anions (X = Cl, Br and I). The corresponding metal–ligand
interatomic bond lengths and angles exhibit some differences
in (I), (II) and (III) (Tables 1–3), but are comparable to the
values of reported related HgII complexes (Masciocchi et al.,
2009). The diameters of the cavities in the middle of the
bis[dichloridomercury(II)], [Hg2Cl4(C24H20N2O2)2], and the
bromido, [Hg2Br4(C24H20N2O2)2], and iodido, [Hg2I4(C24H20-
N2O2)2], analogues. The Hg atoms adopt a highly distorted
tetrahedral coordination environment consisting of two
halides and two pyridine N-donor atoms from two bridging
ligands. In the solid state, the macrocycles form two-
dimensional sheets in the bc plane through noncovalent
Hgꢀ ꢀ ꢀX and Xꢀ ꢀ ꢀX (X = Cl, Br and I) interactions.
Comment
Numerous supramolecular compounds designed and con-
structed through crystal engineering have attracted significant
attention because of their fascinating structural topologies
(Chae et al., 2001) and functional applications (Wang et al.,
2011). It is well known that the selection of appropriate
ligands as building blocks is a key point in the design and
synthesis of functional supramolecular compounds. Compared
with rigid ligands, flexible ligands can adopt different confor-
mations under varying conditions resulting in potentially
novel topologies (Chuang et al., 2010). N-Donor ligands, such
as those containing pyridyl groups, are good candidates for the
assembly of versatile structures (Fujita et al., 2007). Recently,
our group has reported several compounds generated from
flexible ether-bridged ligands containing dicyanomethylene
groups (Dong et al., 2007), carboxylic acid groups (Jiang et al.,
2009), terminal indoline-2,3-dione groups (Fang et al., 2011)
and terminal imidazole groups (Yuan et al., 2011). There are
˚
macrocycles are 3.269 (7), 3.811 (7) and 2.770 (6) A for the Cl,
Br and I derivatives, respectively.
The flexible L ligand can adopt different conformations
under different conditions. In a previous study, a flexible ether-
bridged organic ligand with terminal indoline-2,3-dione
groups adopts a trans conformation about its central core in
the free state, but a gauche conformation after coordinating to
the AgI centre (Fang et al., 2011). Here, in (I), the O1—C12—
C13—O2 torsion angle of the central ether group is
ꢁ71.5 (12)ꢂ (Fig. 1a). In (II), the torsion angle has changed to
ꢁ70.1 (9)ꢂ (Fig. 1b), and in (III), the corresponding torsion
angle is 77.9 (7)ꢂ (Fig. 1c). The sign of the torsion angle in (III)
is opposite to that in (I) and (II), indicating a difference of
some 150ꢂ between these torsion angles in the structures, so
the ethylene bridge is oriented quite differently in (III) to the
corresponding bridges in (I) and (II), as can be seen in Fig. 1.
m156 # 2012 International Union of Crystallography
doi:10.1107/S0108270112019075
Acta Cryst. (2012). C68, m156–m160

metal-organic compounds
Figure 1
The molecular structure of (a) (I), (b) (II) and (c) (III), showing the atom-numbering schemes. Displacement ellipsoids are drawn at the 50% probability
level and H atoms have been omitted for clarity. [Symmetry code: (i) ꢁx + 1, ꢁy + 1, ꢁz + 1.]
Additionally, the dihedral angle between the terminal N1-
pyridine plane and the adjacent C6-benzene plane is 24.7 (2)ꢂ
in (I) and 21.2 (2)ꢂ in (II). In contrast, the terminal N2-pyri-
dine plane and the adjacent C17-benzene plane are nearly
coplanar, with a dihedral angle of 9.8 (3)ꢂ in (I) and 6.8 (2)ꢂ in
(II). In (III), the dihedral angles between the planes of the
relative pyridine rings and benzene rings are 15.0 (2) and
18.5 (2)ꢂ.
In the solid state, compounds (I)–(III) have the same
packing motif; Fig. 2 shows the packing feature of compound
(I). Herein, the representative structure of (I) is described in
detail. As shown in Fig. 3, the one-dimensional Hg—Cl chains
are formed along the [021] direction through noncovalent
Hgꢀ ꢀ ꢀCl interactions [Hg1ꢀ ꢀ ꢀCl2ii; symmetry code: (ii) ꢁx + 1,
ꢁy ꢁ 1 ꢁz + 2]. If three different Clꢀ ꢀ ꢀCl interactions
[Cl2ꢀ ꢀ ꢀCl1ii, Cl2ꢀ ꢀ ꢀCl2ii and Cl1ꢀ ꢀ ꢀCl1iii; symmetry code: (iii)
ꢁx + 1, ꢁy, ꢁz + 2] are taken into consideration, a network
parallel to the bc plane is formed. Fig. 4 shows the chains of
Hg—Br moieties in (II) and the chains of Hg—I moieties in
(III), with noncovalent interactions emphasized. The impor-
tant noncovalent interactions in (I)–(III) are compared in
Figure 2
Table 4. These two-dimensional sheets driven by noncovalent
The packing feature of compound (I). H atoms have been omitted for
clarity.
Hgꢀ ꢀ ꢀX and Xꢀ ꢀ ꢀX (X = Cl, Br and I) interactions are stacked
ꢃ
Acta Cryst. (2012). C68, m156–m160
Wu et al.
[Hg2Cl4(C24H20N2O2)2], [Hg2Br4(C24H20N2O2)2] and [Hg2I4(C24H20N2O2)2] m157

metal-organic compounds
Figure 3
The two-dimensional sheet parallel to the bc plane of (I) and the stacking of the sheets along a. One-dimensional Hg—Cl chains are formed parallel to
[021] through noncovalent Hgꢀ ꢀ ꢀCl interactions (Hg1ꢀ ꢀ ꢀCl2ii) and three different Clꢀ ꢀ ꢀCl interactions (Cl2ꢀ ꢀ ꢀCl1ii, Cl2ꢀ ꢀ ꢀCl2ii and Cl1ꢀ ꢀ ꢀCl1iii). H atoms
have been omitted for clarity. [Symmetry codes: (ii) ꢁx + 1, ꢁy ꢁ 1, ꢁz + 2; (iii) ꢁx + 1, ꢁy, ꢁz + 2.]
Figure 4
The Hg—X fragments and the chains formed by Hgꢀ ꢀ ꢀX and Xꢀ ꢀ ꢀX interactions in (II) and (III) analogous to those shown in Fig. 3. [Symmetry codes: (ii)
ꢁx + 1, ꢁy ꢁ 1, ꢁz + 2; (iii) ꢁx + 1, ꢁy, ꢁz + 2.]
along a without any offset. The Hgꢀ ꢀ ꢀX distances, in the range
benzene (Sarma & Desiraju, 1986). The Hg—X and the weak
Xꢀ ꢀ ꢀX interactions are important for assisting in the lattice
formation.
In summary, three macrocycles have been synthesized
based on the flexible ether-bridged dipyridyl ligand. We anti-
cipate this approach may be useful in constructing novel
supramolecular compounds with the flexible ether-bridged
dipyridyl ligand.
˚
3.369 (2)–3.9819 (9) A, are shorter than their van der Waals
contact distances. The Xꢀ ꢀ ꢀX (X = Cl, Br and I) distances in
(I), (II) and (III) are a little longer than the sums of the van
˚
der Waals radii (van der Waals radii: Hg = 2.15 A, Cl = 1.80 A,
˚
˚
˚
Br = 1.95 A and I = 2.15 A; Batsanov, 2001). Weak Clꢀ ꢀ ꢀCl
˚
interactions as long as 3.72 A, which is longer than the van der
˚
Waals contact of 3.60 A, have been reported for hexachloro-
ꢃ
m158 Wu et al. [Hg2Cl4(C24H20N2O2)2], [Hg2Br4(C24H20N2O2)2] and [Hg2I4(C24H20N2O2)2]
Acta Cryst. (2012). C68, m156–m160

metal-organic compounds
Table 1
Selected geometric parameters (A, ) for (I).
Experimental
ꢂ
˚
For the preparation of 1,2-bis[4-(pyridin-3-yl)phenoxy]ethane (L),
sodium hydroxide (0.44 g, 11 mmol) was added with stirring to a
solution of 1,2-bis(p-tolylsulfonyl)ethane (1.85 g, 5 mmol) and
4-(pyridin-3-yl)phenol (1.71 g, 10 mmol) in anhydrous N,N-di-
methylformamide (50 ml). The mixture was stirred for 24 h at 358 K
and monitored by thin-layer chromatography (TLC). After removal
of the solvent, the compound was purified by column chromato-
graphy using silica gel and CH2Cl2–MeOH (20:1 v/v) to afford L as a
white crystalline solid (yield 1.54 g, 4.18 mmol, 83.7%). Elemental
analysis calculated for C24H20N2O2: C 78.24, H 5.47, N 7.60%; found:
C 78.17, H 5.38, N 7.73%.
Cl1—Hg1
Cl2—Hg1
Hg1—N1
2.337 (2)
2.338 (2)
2.438 (6)
Hg1—N2i
N2—Hg1i
2.463 (5)
2.463 (5)
Cl1—Hg1—Cl2
Cl1—Hg1—N1
Cl2—Hg1—N1
152.25 (10)
100.05 (16)
103.08 (16)
Cl1—Hg1—N2i
Cl2—Hg1—N2i
N1—Hg1—N2i
98.41 (14)
98.11 (14)
86.50 (19)
Symmetry code: (i) ꢁx þ 1; ꢁy þ 1; ꢁz þ 1.
Compound (II)
For the preparation of (I), a solution of HgCl2 (5.97 mg,
0.022 mmol) in methanol (8 ml) was layered onto a solution of L
(8.10 mg, 0.022 mmol) in CH2Cl2 (8 ml). The system was left for
about one week at room temperature and colourless crystals of (I)
were obtained (yield 11.11 mg, 79%). IR (KBr pellet, cmꢁ1): 3417
(m), 3128 (m), 2925 (w), 2873 (w), 1605 (s), 1580 (w), 1515 (s), 1476
(s), 1452 (m), 1435 (m), 1399 (s), 1315 (w), 1282 (s), 1246 (s), 1200 (w),
1181 (s), 1131 (w), 1072 (m), 1026 (w), 1002 (w), 944 (m), 840 (m), 802
(s), 738 (w), 698 (m), 646 (w), 632 (m), 556 (m), 490 (w).
Crystal data
[Hg2Br4(C24H20N2O2)2]
Mr = 1457.66
Triclinic, P1
ꢄ = 81.635 (5)ꢂ
V = 1149.1 (8) A
Z = 1
Mo Kꢂ radiation
ꢀ = 10.20 mmꢁ1
T = 298 K
0.15 ꢄ 0.14 ꢄ 0.13 mm
3
˚
˚
a = 9.021 (4) A
˚
b = 11.096 (4) A
˚
c = 11.914 (5) A
ꢂ = 81.812 (5)ꢂ
ꢃ = 78.764 (5)ꢂ
For the preparation of (II), a solution of HgBr2 (7.93 mg,
0.022 mmol) in methanol (8 ml) was layered onto a solution of L
(8.10 mg, 0.022 mmol) in CH2Cl2 (8 ml). The system was left for
about one week at room temperature and colourless crystals of (II)
were obtained (yield 10.10 mg, 63%). IR (KBr pellet, cmꢁ1): 3415
(m), 3128 (m), 2925 (w), 2873 (w), 1605 (s), 1516 (s), 1476 (s), 1452
(m), 1436 (m), 1400 (s), 1282 (s), 1246 (s), 1181 (s), 1130 (w), 1072
(m), 1026 (w), 1001 (w), 944 (m), 837 (m), 802 (s), 738 (w), 698 (m),
646 (w), 632 (m), 555 (m).
Data collection
Bruker SMART CCD area-detector
diffractometer
Absorption correction: multi-scan
(SADABS; Bruker, 2003)
Tmin = 0.310, Tmax = 0.351
6112 measured reflections
4234 independent reflections
3491 reflections with I > 2ꢅ(I)
Rint = 0.025
Refinement
R[F2 > 2ꢅ(F2)] = 0.040
wR(F2) = 0.100
S = 1.08
280 parameters
H-atom parameteꢁrs3 constrained
For the preparation of (III), a solution of HgI2 (10.00 mg,
0.022 mmol) in methanol (7 ml) was layered onto a solution of L
(8.10 mg, 0.022 mmol) in CH2Cl2 (7 ml). The system was left for
about one week at room temperature and colourless crystals of (III)
were obtained (yield 10.67 mg, 59%). IR (KBr pellet, cmꢁ1): 3417
(m), 3128 (m), 2919 (w), 1605 (s), 1517 (s), 1475 (s), 1450 (m), 1436
(m), 1399 (s), 1313 (w), 1280 (s), 1246 (s), 1180 (s), 1130 (w), 1073 (m),
1024 (w), 1001 (w), 950 (s), 836 (s), 801 (s), 738 (w), 700 (m), 646 (w),
630 (m), 553 (m).
˚
Áꢆmax = 1.19 e A
Áꢆmin = ꢁ1.04 e A
ꢁ3
˚
4234 reflections
Compound (III)
Crystal data
[Hg2I4(C24H20N2O2)2]
Mr = 1645.62
Triclinic, P1
ꢄ = 77.620 (2)ꢂ
V = 1213.3 (4) A
Z = 1
3
˚
˚
a = 8.9444 (16) A
˚
Mo Kꢂ radiation
ꢀ = 8.91 mmꢁ1
T = 298 K
0.20 ꢄ 0.15 ꢄ 0.15 mm
Compound (I)
b = 12.352 (2) A
˚
c = 12.052 (2) A
Crystal data
ꢂ = 72.641 (2)ꢂ
ꢃ = 74.882 (2)ꢂ
[Hg2Cl4(C24H20N2O2)2]
Mr = 1279.82
Triclinic, P1
ꢄ = 84.014 (2)ꢂ
3
˚
V = 1102.8 (3) A
Z = 1
Data collection
˚
a = 8.7822 (15) A
b = 10.6904 (18) A
Mo Kꢂ radiation
ꢀ = 7.25 mmꢁ1
T = 298 K
0.20 ꢄ 0.15 ꢄ 0.15 mm
Bruker SMART CCD area-detector
diffractometer
Absorption correction: multi-scan
(SADABS; Bruker, 2003)
Tmin = 0.269, Tmax = 0.348
6387 measured reflections
4426 independent reflections
3740 reflections with I > 2ꢅ(I)
Rint = 0.023
˚
˚
c = 12.044 (2) A
ꢂ = 86.662 (2)ꢂ
ꢃ = 78.930 (2)ꢂ
Data collection
Bruker SMART CCD area-detector
diffractometer
Absorption correction: multi-scan
(SADABS; Bruker, 2003)
Tmin = 0.325, Tmax = 0.410
5867 measured reflections
4066 independent reflections
3708 reflections with I > 2ꢅ(I)
Rint = 0.021
Table 2
Selected geometric parameters (A, ) for (II).
ꢂ
˚
Br1—Hg1
Br2—Hg1
Hg1—N1
2.4644 (10)
2.4512 (12)
2.443 (6)
Hg1—N2i
N2—Hg1i
2.449 (5)
2.449 (5)
Refinement
Br1—Hg1—Br2
Br1—Hg1—N1
Br2—Hg1—N1
150.17 (4)
100.18 (15)
104.22 (15)
N2i—Hg1—Br1
N2i—Hg1—Br2
N1—Hg1—N2i
97.82 (14)
100.51 (14)
86.53 (19)
R[F2 > 2ꢅ(F2)] = 0.042
wR(F2) = 0.116
S = 1.08
280 parameters
H-atom parameteꢁrs3 constrained
˚
Áꢆmax = 1.99 e A
ꢁ3
˚
4066 reflections
Áꢆmin = ꢁ1.68 e A
Symmetry code: (i) ꢁx þ 1; ꢁy þ 1; ꢁz þ 1.
ꢃ
Acta Cryst. (2012). C68, m156–m160
Wu et al.
[Hg2Cl4(C24H20N2O2)2], [Hg2Br4(C24H20N2O2)2] and [Hg2I4(C24H20N2O2)2] m159

metal-organic compounds
Table 3
Selected geometric parameters (A, ) for (III).
bond to keep the rationality of the ring. As a result, the C6—C11
˚
bond length is 1.388 (6) A.
ꢂ
˚
For all compounds, data collection: SMART (Bruker, 2003); cell
refinement: SMART; data reduction: SAINT (Bruker, 2003);
program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);
program(s) used to refine structure: SHELXL97 (Sheldrick, 2008);
molecular graphics: SHELXTL (Sheldrick, 2008); software used to
prepare material for publication: SHELXTL.
I1—Hg1
I2—Hg1
Hg1—N1
2.6365 (6)
2.6272 (6)
2.482 (5)
Hg1—N2i
N2—Hg1i
2.471 (5)
2.471 (5)
I1—Hg1—I2
I1—Hg1—N1
I2—Hg1—N1
149.69 (2)
98.91 (12)
103.46 (12)
N2i—Hg1—I1
N2i—Hg1—I2
N2i—Hg1—N1
100.74 (11)
100.93 (11)
86.14 (16)
Symmetry code: (i) ꢁx þ 1; ꢁy þ 1; ꢁz þ 1.
We are grateful for financial support from the NSFC (grant
Nos. 91027003 and 21072118), 973 Program (grant No.
2012CB821705), PCSIRT, Shangdong Natural Science Foun-
dation (grant No. JQ200803) and Taishan scholars’ construc-
tion project special fund.
Table 4
Comparative geometric parameters (A) for the important noncovalent
interactions in (I), (II) and (III).
˚
(I) (X = Cl)
(II) (X = Br)
(III) (X = I)
Hg1—X2ii
X2—X2ii
X2—X1ii
X1—X1iii
3.369 (2)
3.935 (3)
3.985 (3)
3.661 (3)
3.6254 (19)
4.077 (2)
4.405 (2)
3.914 (2)
3.9819 (9)
4.4521 (11)
4.7066 (11)
4.5354 (12)
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GZ3208). Services for accessing these data are
described at the back of the journal.
Symmetry codes: (ii) ꢁx ꢁ 1, ꢁy ꢁ 1, ꢁz + 2; (iii) ꢁx + 1, ꢁy, ꢁz + 2.
References
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R[F2 > 2ꢅ(F2)] = 0.034
wR(F2) = 0.086
S = 1.02
4426 reflections
280 parameters
1 restraint
H-atom parameteꢁrs3 constrained
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Áꢆmax = 1.11 e A
ꢁ3
˚
Áꢆmin = ꢁ1.10 e A
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˚
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˚
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˚
1.378 A; a restraint of 1.37 (1) A was applied to the longer C6—C11
˚
ꢃ
m160 Wu et al. [Hg2Cl4(C24H20N2O2)2], [Hg2Br4(C24H20N2O2)2] and [Hg2I4(C24H20N2O2)2]
Acta Cryst. (2012). C68, m156–m160