Halogen anion-directed helical host chain and the effect of halogen anions on the inclusion property

Article abstract of DOI:10.1080/10610278.2012.741686

In this paper, a series of halogen anion-directed complexes 0.5[CH ₃OH] · 0.5[H₂O] ? [L1H₂] ²⁺ · 2[Cl^-] (crystal 1), 0.5[H₂O], {[L1H₂]²⁺}_0.5 · [Br^-] (crystal 2), [L2H₂]²⁺ · 2[Br]^- (crystal 3), [L1H₂]²⁺ · 2[] (crystal 4) and 2[L2H ₂]²⁺ · 2[I^-₃] (crystal 5) were synthesised (L1 = diamine N,N,N′,N′-tetrabenzyl-2-butylyne-1,4- diamine, L2 = N,N,N′,N′-tetra-(p-tertbutylbenzyl)-ethyl-enediamine), in which the halogen anions act as templates, via N-H.X (halogen) interactions, generating the helical structures. The choice of anion in this process was shown to be crucial for the successful assembly of the host chains and as well the inclusion property, meanwhile, the conformation of L1 and L2 may also exert an important influence on the formation of helical structures. X-ray structure studies have shown that the ability of the halides to template the formation of the helical host chains follows the order Cl^- > Br^- > I^-.

Full text of DOI:10.1080/10610278.2012.741686

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Supramolecular Chemistry
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Halogen anion-directed helical host chain and the
effect of halogen anions on the inclusion property
Fang Guo a , Hong-cui Yu a , Lei Li a , Fang Xia a , Jian Tong a & Bao-xin Wang a
a College of Chemistry, Liaoning University, Shenyang, 110036, P.R. China
Version of record first published: 19 Nov 2012.
To cite this article: Fang Guo , Hong-cui Yu , Lei Li , Fang Xia , Jian Tong & Bao-xin Wang (2012): Halogen anion-
directed helical host chain and the effect of halogen anions on the inclusion property, Supramolecular Chemistry,
DOI:10.1080/10610278.2012.741686
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Supramolecular Chemistry
iFirst article, 2012, 1–8
Halogen anion-directed helical host chain and the effect of halogen anions
on the inclusion property
Fang Guo*, Hong-cui Yu, Lei Li, Fang Xia, Jian Tong and Bao-xin Wang
College of Chemistry, Liaoning University, Shenyang 110036, P.R. China
(Received 7 July 2012; final version received 16 October 2012)
In this paper, a series of halogen anion-directed complexes 0.5[CH3OH]· 0.5[H2O] , [L1H2]2þ · 2[Cl2] (crystal 1),
}
0.5[H2O], {[L1H2]2þ 0.5 · [Br2] (crystal 2), [L2H2]2þ · 2[Br]2 (crystal 3), [L1H2]2þ · 2[I32] (crystal 4) and 2[L2H2]2þ · 2[I23 ]
(crystal 5) were synthesised (L1 ¼ diamine N,N,N0,N0-tetrabenzyl-2-butylyne-1,4-diamine, L2 ¼ N,N,N0,N0-tetra-( p-
tertbutylbenzyl)-ethyl-enediamine), in which the halogen anions act as templates, via N–H· · ·X (halogen) interactions,
generating the helical structures. The choice of anion in this process was shown to be crucial for the successful assembly of
the host chains and as well the inclusion property, meanwhile, the conformation of L1 and L2 may also exert an important
influence on the formation of helical structures. X-ray structure studies have shown that the ability of the halides to template
the formation of the helical host chains follows the order Cl2 . Br2 . I2.
Keywords: anion template; helical structure; halogen anion; host–guest; hydrogen bonding
1. Introduction
our current synthetic strategy is to acquire metal-free
host–guest complexes featuring helical characters. In this
work, we have synthesised a new kind of halogen anion-
directed helical chain, in which the halogen anions act as
templates, via N–H· · ·X (halogen) or C–H· · ·X (halogen)
interactions, generating the helical structures. In our
strategy, the diamine ligands N,N,N0,N0-tetrabenzyl-2-
butylyne-1,4-diamine (L1) and N,N,N0,N0-tetra-( p-tertbu-
tylbenzyl)-ethyl-enediamine (L2) were chosen as the
organic ligand based on the following considerations
(Scheme 1): (i) two N functionality groups are located in
the middle positions, instead of a, v position; (ii) two N
atoms are attached to the substituent benzyl rings, and
spaced by different spacers, such as methylene and 2-
butyne; (iii) two functionality groups are easily double
protonated. Such structure can be motivated by
geometrical requirements for the recognition of halide
anions.
Helical structures, which are ubiquitous in nature and are
the foundation of the genetic code, have received
widespread attention because of their importance in
biological and supramolecular chemistry (1–3). Many
chemists have made great contributions to this field, and
the preparation and characterisation of single, double and
triple helical structures through the self-assembly of
ligands and metal cations have shown significant progress
recently (4–9). The factors affecting the formation of
helices also have attracted particular interest. For example,
molecular shape can determine the helical packing motif
(10). The coordination interactions can effectively
generate helices (11). Hydrogen bonding interaction is
also a versatile and efficient supramolecular synthon in
crystal engineering, even the weak interactions such as
C–H· · ·O, p–p stacking and C–H–p interactions may
produce helical structures (12–20). However, to our best
knowledge, the helical structures constructed via hydrogen
bonding interactions are still rare.
2. Experiment
The use of anion template to direct the formation of
specific molecules and assemblies is an area of
supramolecular chemistry (21). The different anions can
have influence on the self-assembly of the helices (4, 22).
However, the anion-templated formation is particularly
rare in the assembly of metal-free helices (23, 24). Gale
and co-workers (25) have reported the first example of an
anion-templated assembly of a helix formed by two
neutral strands (containing amides as hydrogen bond
donors). Inspired by the aforementioned consideration,
2.1 Materials and instrumentation
All chemicals were obtained from commercial sources and
used without further purifications. IR spectra were
obtained with a PerkinElmer 100 FT-IR spectrometer
(USA) using KBr pellets. NMR spectra were recorded on a
Mercury-Plus 300 spectrometer (VARIAN, 300 MHz,
USA) at 258C with TMS as the internal reference.
Differential scanning calorimetry was performed using a
TA Instrument Q100 differential scanning calorimeter.
*Corresponding author. Email: fguo@lnu.edu.cn
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2012.741686
http://www.tandfonline.com

2
F. Guo et al.
tert-butyl-benezene), 136.783 (benzene ring attached to
CH2), 149.333 (benzene ring attached to tert-butyl).
H2
C
H2
C
N
C
C
N
L1
2.4 Preparation of
0.5[CH3OH]· 0.5[H2O] , [L1H2]21 · 2[Cl]2 (crystal 1)
L1 (0.22 g), 25 ml methanol, 1.5 ml concentrated hydro-
chloric acid and 3 ml water were placed in a 50-ml
Erlenmeyer flask and shaken until the contents were
dissolved. The flask was allowed to stand for over 5 days at
room temperature. Recrystallisation produced white block
crystals, m.p. 219–2248C; IR (KBr), lmax (cm21): 3419 (s,
NþH), 3040 (w, ArH), 2516 (s, NþH), 1498, 1458 (s, Ar),
2915 (s, CH2), 1087 (m, C–O). 1H NMR (DMSO,
300 MHz) d: 3.85 (6H, d, CH2), 4.40 (8H, s, CH2), 7.44–
7.71 (20H, m, ArH), 12.37 (2H, s, NþH).
H2
C
H2
C
N
N
L2
Scheme 1. Structures of L1 and L2.
2.2 Preparation of L1
Dibenzylamine (43 ml) was slowly added into the solution
of 17 g NaHCO3 and 23 ml distilled water. 1,4-Dichloro-2-
butyne of 13 ml (2–3 drops/s) was then continuously
added into the mixture solution. After the reaction was
heated to 958C and stirred for 4 h, the mixture was cooled
to room temperature. The white reaction product
was separated by diethyl ether, and then washed with
distilled water. Recrystallisation using acetone and drying
in vacuo, produced white crystals 27 g, yield 60.8%.
m.p. 109–1128C. IR (KBr), lmax (cm21): 3028 (w, ArH),
1600, 1494, 1452 (s, Ar), 2911 (s, CH2); 1H NMR (CDCl3,
300 MHz) d: 3.36 (4H, s, CH2), 3.78 (8H, s, CH2), 7.26–
7.45 (20H, m, ArH). 13C NMR (CDCl3, 75.45 MHz) d:
41.461 (CH2 attached to alkyne bond), 57.605 (CH2
attached to benzyl group), 79.831 (C;C), 127.091 ( p-C
of monosubstituted benzene), 128.278 (m-C of monosub-
stituted benzene), 128.961 (o-C of monosubstituted
benzene), 138.889 (C of monosubstituted benzene
attached to CH2).
2.5 Preparation of 0.5[H2O] , {[L1H2]21} 0.5[Br]2
(crystal 2)
L1 (0.11 g), 20 mlmethanol, 2.0 ml hydrobromine and
2 ml water were placed in a 50-ml Erlenmeyer flask and
shaken until the contents were dissolved. The flask was
allowed to stand for over 2 days at room temperature.
Recrystallisation produced white transparent crystals,
m.p. 200–2068C; IR (KBr), lmax (cm21): 3441 (s, NþH),
3031 (w, ArH), 2509 (s, NþH), 1496, 1458 (s, Ar), 2911
1
(s, CH2), 1625 (w, H2O). H NMR (DMSO, 300 MHz)
d: 3.94 (4H, s, CH2), 4.45 (8H, s, CH2), 7.47–7.64 (20H,
m, ArH).
2.6 Preparation of 2[H2O] , [L2H2]21 · 2[Br]2
(crystal 3)
L2 (0.15 g), 30 ml methanol, 1.0 ml hydrobromine and
3 ml water were placed in a 50-ml Erlenmeyer flask and
shaken until the contents were dissolved. The flask was
allowed to stand for over 4 days at room temperature,
producing white transparent block crystals. m.p. 216–
2208C; IR (KBr), lmax (cm21): 3632 (w, H2O), 3442 (s,
NþH), 2687, 2512 (s, NþH), 1615, 1516, 1456 (s, Ar),
2.3 Preparation of L2
Ethylene diamine (7 ml) was slowly added into the
solution of 8 g NaOH and 20 ml distilled water. p-
Tertbutyl-benzyl chloride of 40 ml (2–3 drops/s) was then
continuously added into the mixture solution. After the
reaction was heated to 958C and stirred for 3 h, the mixture
was cooled to room temperature. The white reaction
product was separated by chloroform and then washed
with distilled water. Recrystallisation using acetone and
drying in vacuo, produced white crystals 21.6 g, yield
67.1%. m.p. 156–1588C, IR (KBr), lmax (cm21): 3059 (w,
ArH), 1602, 1513, 1462 (s, Ar), 2869 (s, CH2), 2960 (s,
1
2960, 2869 (s, CH3), 2903 (s, CH2); H NMR (CDCl3,
300 MHz) d: 1.25 (36H, s, CH3), 1.70 (5H, s, H2O), 3.82
(4H, s, CH2), 3.97–4.03 (4H, q, CH2), 4.17–4.21 (4H, q,
CH2), 7.41–7.54 (16H, m, ArH).
2.7 Preparation of [L1H2]21 · 2[I3]2 (crystal 4)
1
CH3); H NMR (CDCl3 300 MHz) d: 1.30–1.31 (18H, d,
L1 (0.10 g), 25 ml methanol and 0.5 ml hydroiodic acid
were placed in a 50-ml Erlenmeyer flask and shaken until
the contents were dissolved. The flask was allowed to
stand for over 2 days at room temperature, producing red
block crystals, m.p. 190–1968C; IR (KBr), lmax (cm21):
2695, 2600 (s, NþH), 1498, 1454 (s, Ar), 2934 (s, CH2);
CH3), 2.63 (2H, s, CH2), 3.50 (4H, s, CH2), 7.22–7.30
(8H, m, ArH). 13C NMR (CDCl3, 75.45 MHz) d: 31.476
(CH3 of tert-butyl), 34.391 (quaternary carbon attached to
benzene ring), 51.340 (CH2), 58.174 (CH2 of benzyl ring),
124.947 (o-C of tert-butyl-benezene), 128.343 (m-C of

Supramolecular Chemistry
3
1H NMR (DMSO, 300 MHz) d: 3.86 (4H, s, CH2), 4.34
(8H, s, CH2), 7.49–7.53 (20H, m, ArH).
3. Results and discussion
3.1 Structure of crystals 1–5
Crystal structures of 1–3 are halogen anion-directed host–
guest complexes, in which the halogen anions act as
templates, via N–H· · ·X (halogen) or C–H· · ·X (halogen)
interactions, generating the helical host, within which the
guest molecules are included.
2.8 Preparation of 2[L2H2]21 · 2[I3]2 (crystal 5)
L2 (0.10 g), 25 ml methanol and 0.5 ml hydroiodic acid
were placed in a 50-ml Erlenmeyer flask and shaken until
the contents were dissolved. The flask was allowed to
stand for over 2 days at room temperature, producing red
block crystals. m.p. 189–1948C. IR (KBr), lmax (cm21):
3431 (s, NþH), 1613, 1513, 1462 (s, Ar), 2960, 2865
In crystal 1, there are one double-protonated L1, two
chloride anions, half methanol and half water molecule in
one asymmetric unit. The two crystallographically
independent chloride anions Cl1 and Cl2, acting as
templates, bind simultaneously double-protonated L1
through two strong N–H· · ·Cl interactions (N1–
1
(s, CH3), 2903 (s, CH2); H NMR (CDCl3, 300 MHz) d:
1.25 (36H, s, CH3), 3.16 (4H, s, CH2), 3.71 (8H, s, CH2),
5.06 (2H, s, NþH), 7.20–7.22 (8H, d, ArH), 7.38–7.41
(8H, m, ArH).
˚
˚
H1· · ·Cl1: 3.058 A, 170.88; N2–H2· · ·Cl2: 3.088 A,
176.78), forming a double anion-directed unit, as seen in
Figure 1(a). An anion-directed helical chain along c-axis is
formed, involving the above N–H· · ·Cl hydrogen bonds
(Figure 1(b)). However, there are no short contacts
between the helical chains, and the helical chains are
isolated.
2.9 Crystallography
Single-crystal X-ray diffraction measurements of com-
plexes were carried out on a Bruker Smart CCD
diffractometer equipped with a graphite monochromator.
The determination of unit cell parameters and data
collection was performed with MoKa radiation
The guest molecules of methanol and water are filled
between the neighbouring helical chains and stabilised by
the O–H· · ·Cl interactions [water· · ·Cl2: 3.213 A
˚
˚
(l ¼ 0.71073 A). The unit cell parameters were obtained
2
(O1w· · ·Cl1) and methanol· · ·Cl : 3.316 A (O1M· · ·Cl2)]
˚
with least-squares refinements and the structures were
determined using direct methods and refined (based on F 2
using all independent data) by full-matrix least-square
methods (SHELXTL 97) (26). The details of data
collection, data reduction and crystallographic data are
summarised in Table 1. CCDC 889241–889245 contain
the supplementary crystallographic data for this paper.
with the two chloride anions. The guest molecules are
connected with each other through O· · ·O interactions
˚
[2.481 A (O1w· · ·O1M)] between the methanol and the
water, forming a trapezoidal-shaped hydrogen bonded
network, as seen in Figure 1(c). The overall 3D structural
framework is given in Figure 1(d).
Table 1. Crystal data and refinement summary for crystals 1–5.
1
2
3
4
5
Temperature (K)
Crystal system
Space group
Z
294
Monoclinic
P21/c
294
Monoclinic
P2/c
294
Monoclinic
P21/c
113
Triclinic
P-1
113
Monoclinic
C2
4
4
4
2
4
˚
a (A)
8.889(2)
23.792(5)
14.681(3)
90
90.277(4)
90
3104.9(13)
1.214
1208
0.0506
15,938
5472
2905
389
0.0647/0.1689
0.1306/0.2110
1.026
9.0083(16)
11.566(2)
15.164(3)
90
90.265(3)
90
1579.9(5)
1.294
630
0.0452
7766
2789
2088
172
0.0436/0.1274
0.0642/0.1417
1.07
11.2294(15)
12.4585(15)
33.103(4)
90
94.128(2)
90
4619.1(10)
1.212
1784
0.0574
22,935
8142
5443
581
0.0669/0.1442
0.1056/0.1587
1.087
9.4807(19)
9.5065(19)
11.255(2)
104.13(3)
110.58(3)
91.92(3)
913.0(3)
2.197
558
0.0274
5579
3192
2672
181
0.0269/0.0626
0.0330/0.0656
0.984
9.4241(19)
18.800(4)
26.836(5)
90
92.50(3)
90
4750.1(16)
1.436
2056
0.0808
12,736
6857
5792
469
0.0858/0.2191
0.0927/0.2269
1.036
˚
b (A)
˚
c (A)
a ( 8 )
b ( 8 )
g ( 8 )
3
˚
V (A )
Dx (g cm23
F(0 0 0)
Rint
)
No. of total reflns
No. of unique reflns
No. of obsd reflns I . 2s(I)
No. of refined parameters
Rf/wRf
All data Rf/wRf
s

4
F. Guo et al.
Figure 1. Crystal 1: (a) a double anion-directed unit, (b) the formation of anion-directed helical chain along c-axis, (c) the inclusion of
guest molecules and the interactions between the guest and host chains and (d) the overall 3D structural framework.
In the crystal 2, there are half double-protonated L1,
one bromine anion and one water molecule in one
asymmetric unit. The bromine anion, as a template, binds
protonated L2 simultaneously through two strong
˚
N–H· · ·Br interactions (N1–H1· · ·Br2: 3.205 A, 167.28;
˚
N2–H2· · ·Br1: 3.192 A, 164.28), forming a double anion-
˚
directly with L1 molecules through N–H· · ·Br (3.259 A,
directed unit, as seen in Figure 3(a). Such units are further
linked to a helical chain along b-axis, as seen in Figure 3(b).
Interestingly, the helical chains are linked into a 3D
network. The main difference between crystals 3 and 1/2 is
that the template Br anions are located at the outside of the
chains and connect with the neighbouring helical chains via
N–H· · ·Br interactions. The water molecules are filled
inside the channel between the neighbouring helical chains,
171.18), forming a similar anion-directed unit to crystal 1
(Figure 2(a)). A helical chain is also formed, in which the
R24(10) hydrogen bonding arrays are involved to stabilise
the chain, whilst Br1 forms a bifurcated hydrogen bonds
˚
(N1–H1· · ·Br1: 3.259 A, 171.18 and C1–H1B· · ·Br1:
˚
3.849 A, 156.28) (Figure 2(b)). Similar to crystal 1, the
helical chains are also isolated, and no short contacts
between the helical chains are involved. Water molecules
are filled into the helical chains, in which a similar
trapezoidal-shaped hydrogen-bonded network is present,
with the distances of bromine· · ·water and water· · ·water
˚
with O1–H1c· · ·Br1 (3.515 A, 152.48) and O1–H1D· · ·Br2
˚
(3.652 A, 156.18) stabilising the helical chains and the guest
molecules (Figure 3(c)). It is necessary to mention that the
four tert-butyl groups of L2 ligand are greatly disordered,
with the C atom of each methyl refined anisotropically as
two closely situated positions for the sake of overall
convergence with the most reasonable Rf factor. The
occupancies of two sites are refined as 0.230/0.770,
0.818/0.182, 0.606/0.394, 0.647/0.353, for the four tert-
butyl groups, respectively.
˚
˚
being 3.365 A (Br1· · ·O1) and 2.934 A (O1· · ·O1),
respectively (Figure 2(c)). The overall 3D structural
framework is given in Figure 2(d).
Similar to crystals 1 and 2, there are one double-
protonated L2, two bromine anions and two water
molecules in one asymmetric unit in crystal 3. The two
crystallographically independent bromine anions Br1 and
Br2, as templates, also bind simultaneously with double-
In contrast to crystals 1–3, an interesting variation
occurs in the crystals 4–5, although the ligands L1 and L2

Supramolecular Chemistry
5
discrete triiodide anion (labeled I1–I2–I3), the I2 units
2
have a distance of 2.884 (1) A (I2–I3), and I with I2 units
˚
˚
has a distance of 2.954 (1) A (I1–I2). The angle of I–I–I is
176.78. The triiodide in this crystal is comparable with
those found in the triiodide anions of [Fe(phen)3](I3)2
(solvent) (27). As the potential energy surfaces of I23 are
flat (28, 29), the anion I23 is positioned on the surfaces of
˚
the molecule of L1 through N1–H1· · ·I1 (3.588 A, 166.18).
The extension of the hydrogen-bonding linkages resulted
in 1D-layered network along (0 1 1), and is then
sandwiched with I23 species, as seen in Figure 4.
In crystal 5, one asymmetric unit comprises two
independently double-protonated L2 and two discrete
triiodide anions. The two crystallographically independent
discrete triiodide anions (labeled I4–I3–I4 and I2–I1–
˚
I2), with I–I distances being 2.820 (1) A (I1–I2) and 2.925
˚
(1) A (I3–I4), and I–I–I angle being 176.18 (I2–I1–I2)
and 176.88 (I4–I3–I4), respectively. One triiodide anion
I23 (I4–I3–I4) is positioned on the surfaces of one
molecule of L2 in the asymmetric unit through van der
Waals force [the nearest distance is C24–H24· · ·I4
2
˚
(4.131 A, 176.58)], whereas the other triiodide anion I3
(I2–I1–I2) sits on the surface of the other crystal-
lographically independent molecule of L2 through van der
Waals force [the nearest distance is C19–H19· · ·I2
˚
(4.201 A, 160.68)]. The two discrete triiodide anions, as
templates, linking the neighbouring L2 molecules along c-
axis into a helical chain through shot contacts between
Figure 2. Crystal 2: (a) a anion-directed unit, (b) the formation
of helical chain, (c) the inclusion of water molecules and the
interactions between the guest and host chains and (d) the overall
3D structural framework.
˚
tert-butyl groups (H11A· · ·H15: 2.8 A, H34B· · ·H45B:
˚
2.1 A), as seen in Figure 5, but no guest molecules are
included.
are reacted with HI in identical experimental conditions.
In crystal 4, there are half double-protonated L1 and one
discrete triiodide anion I23 in one asymmetric unit. In the
Figure 3. Crystal 3: (a) a double anion-directed unit, (b) the formation of a helical chain along b-axis and (c) the inclusion of guest
molecules and the interactions between the guest and host chains.

6
F. Guo et al.
However, due to the relatively larger anion radius of I32
than Br2 and Cl2, no guest molecules were included
inside the host formed by I23 . Therefore, the size of the
anion may exert an important influence on the inclusion
property.
In addition, in the case of I23 as templates, although the
ligands L1 and L2 are reacted with HI in identical
experimental conditions, the ligand L2 is more favourable
to the formation of helical structures than the ligand L1.
There are two main differences between two ligands: (1)
the two methylene groups as spacers between N atoms in
L2 are more flexible than the 2-butyne groups in L1, thus
facilitating conformational change to produce the helices
instead of the rigid linear arrangement. (2) The substituent
tert-butyl groups, which have short contacts between the
neighbouring L2 ligands, are key to the formation of
helices. Therefore, the choice of ligands, with different
conformation and substituent groups, may also exert an
important influence on the generation of helical structures.
The thermogravimetric analysis (TGA) was carried out
on crystals 1–4 (see Figure 6). The crystal specimens
having a nominal mass between 15 and 20 mg were placed
in ceramic sample pans. Samples were equilibrated at
258C for 5 min, and then ramped to 8008C at 108C/min. In
crystal 1, the decomposition could mainly proceed in three
stages. The first two stages in the range from 30 to 2008C
probably corresponds to the elimination of HCl gas (which
was speculated from the previous studies of solid-state
interconversions of coordination networks and hydrogen-
bonded salts (30)) and the weight loss of included water
and methanol (18.5% obsd; 18.1% calcd). The subsequent
weight loss was considered to be a result of the further
decomposing of the ligand. In crystal 2, 3.2% weight loss
beginning from 30 to 908C corresponds to the loss of the
included water (calcd 2.9%). The subsequent weight loss
above 908C was considered to be a result of the further
Figure 4. Crystal 4: the 1D layered network along (0 1 1) and I32
species as sandwich between the layers.
3.2 The effect of halogen anions on the inclusion
property and thermal analysis
From the X-ray structural analysis, we found that the
choice of halogen anions may have effect on the inclusion
property. The inclusion property follows the order Cl2
. Br2 . I2. In the case of Br2 as templateds, the helical
host can accommodate the guest molecules of water,
whereas in the case of Cl2 anions as templates, the host
can include both methanol and water guest molecules.
Figure 5. Crystal 5: helical structural packing along c-axis.
Figure 6. TGA of crystals 1–4.

Supramolecular Chemistry
7
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decomposing of the ligand and HBr. In crystal 3, one stage
in the range from 30 to 2208C, corresponding to the weight
loss of included water (4.0% obsd; 4.2% calcd). The
subsequent weight loss above 2208C was the further
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the range from room temperature to 1808C could
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4. Conclusion
Herein, we have synthesised a series of halogen anion-
directed host–guest complexes, in which the halogen
anions act as templates, via N–H· · ·X (halogen) or C–
H· · ·X (halogen) interactions, generating the helical host,
within which the guest molecules are included. The choice
of anion in this process was shown to be crucial for the
successful assembly of the host chains and as well the
inclusion property, meanwhile, the conformation of L1
and L2 may also exert an important influence on the
formation of helical structures. X-ray structure studies
have shown that the ability of the halides to template the
formation of the helical host chains follow the order Cl2
. Br2 . I2.
Acknowledgements
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This work was supported by the National Science Foundation of
China (no. 20903052), SRF for ROCS, SEM, the Programme for
Liaoning Excellent Talents in University (no. LJQ2011003) and
Foundation of 211 Project for Innovative Talents Training,
Liaoning University.
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8
F. Guo et al.
A new kind of halogen anion-directed helical chain
has been synthesised, in which the halogen
anions act as templates, via N–H· · ·X (halogen)
interactions, generating the helical structures.
Fang Guo, Hong-cui Yu, Lei Li,
Fang Xia, Jian Tong and
Bao-xin Wang
Halogen anion-directed helical
host chain and the effect of
halogen anions
on the inclusion property
1–8