Highly stable 3D homochiral coordination polymer with interweaving of double-stranded helices and extended metal-SO4-metal chains

Article abstract of DOI:10.1016/j.inoche.2012.01.021

Solvothermal synthesis of an achiral ligand N,N-bis(3-pyridyl) isophthalamide (bpip) with ZnSO₄ under 120 °C yield a novel compound, [Zn(bpip)SO₄]n, which displays chiral self-assembly into an infinite double-stranded helical coordination polymer consisting of two single-stranded helices with the same P handedness. These chiral infinite double-stranded helical chains are further interwoven by the 1D Zn-SO ₄-Zn chains to form a novel 3D framework structure with a rare 6 ⁵.10 topology. On the basis of the results of TG-DSC analyses, the structure is thermally stable up to ～ 467.4 °C.

Full text of DOI:10.1016/j.inoche.2012.01.021

Inorganic Chemistry Communications 19 (2012) 23–26
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Highly stable 3D homochiral coordination polymer with interweaving of
double-stranded helices and extended metal-SO4-metal chains
Jie Wu a,b, Chao Huang a, Leixia Fu a, Pei Wang a, Chuanjun Song a, Changjian Song a, Haiyu Wang a,
a,b,⁎⁎
Hongwei Hou a, , Junbiao Chang
⁎
a
Department of Chemistry, Zhengzhou University, Zhengzhou 450052, PR China
School of Pharmaceutical Science, Zhengzhou University, Zhengzhou 450052, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Solvothermal synthesis of an achiral ligand N,N-bis(3-pyridyl) isophthalamide (bpip) with ZnSO4 under 120 °C
yield a novel compound, [Zn(bpip)SO4]n, which displays chiral self-assembly into an infinite double-stranded
helical coordination polymer consisting of two single-stranded helices with the same P handedness. These chiral
infinite double-stranded helical chains are further interwoven by the 1D Zn–SO4–Zn chains to form a novel 3D
framework structure with a rare 65.10 topology. On the basis of the results of TG-DSC analyses, the structure is
thermally stable up to ~467.4 °C.
Received 22 September 2011
Accepted 21 January 2012
Available online 31 January 2012
Keywords:
Coordination polymers
Helical structures
Topochemistry
Solvothermal synthesis
Zinc
© 2012 Elsevier B.V. All rights reserved.
Since the discovery of the double-stranded helical structure of
DNA, double-stranded helical structures constructed from metal-
directed self-assembly have received much attention in coordination
chemistry and materials chemistry because of the persistent interests
in numerous enantioselective processes including asymmetric cataly-
sis, chemical sensing, and selective guest inclusion [1–5]. These stud-
ies have usually been focused on the design and synthesis of dimeric
helical assemblies mediated by metal-ligand coordination, in which
the metal ions are helically wrapped by two helical bridging organic
ligands. There are numerous reports on coordination polymers that
exhibit infinite double-helical motifs based on stereoselective synthe-
sis using chiral ligands or by spontaneous resolution upon crystalliza-
tion without any chiral auxiliary [6–12]. Spontaneous resolution is a
more economical and convenient approach, and has received much
more attention, however, which is a relatively rare phenomenon
and less predictable because the conglomeration processes are not
yet fully understood [6,13–16].
hydrogen bonding interactions, which have definite directions that
sometimes can efficiently transfer of stereochemical information be-
tween neighboring homochiral chains, are the driving force in the par-
allel packing to form double-stranded helical structure in the
spontaneous resolution process [6]. Jung et al. also reported a supramo-
lecular framework consisting of two kinds of channels via self assembly
of a 1D double-stranded chain in a prismatic fashion. Weak C–H⋯π in-
teraction may be the driving force in the assembly of the prismatic
channel structure [17]. However, the precise prediction of chiral frame-
work with double-stranded helical structure in the spontaneous resolu-
tion process is still a daunting task because the formation of such a
framework is governed by many factors, and the control of framework
chirality is particularly difficult.
It has been noted that the employment of rigid and V-shaped exo-
bidentate organic bridges can improve the helicity of the polymeric
chains [15,18]. Recently, some groups including our group have intro-
duced V-shaped symmetrical ligand of N,N-bis(3-pyridyl)isophthala-
mide (bpip) and N,N-bis(pyridine-3-yl)pyridine-3,5-dicarboxamide
to acquire functional MOFs with helical structure [19–21]. Due to
the distortion from the planarity of the two terminal pyridine rings
and the freedom rotation of C–N bond between the amide and pyridyl
moieties, the ligands may be locked in twisting configurations. If
there are two strands with the same chirality and all parallel double
helices are also the same chirality, the double-stranded polymer
would be noncentrosymmetric and chiral even if it contains no chiral
molecular unit in the helices.
Recently, some groups have made great contribution to the advance
and comprehension of the elements that mediate the chirality of
double-stranded helical metal complexes in the spontaneous resolution
process [6,14,17]. In most cases, the metal-directed self-assembly and
the hydrogen-bonding-driven self-assembly are common approaches
to constructing supramolecular duplexes. Bu et al. have reported that
⁎
Corresponding author. Tel.: +86 371 67761744.
⁎⁎ Correspondence to: J. Chang, Department of Chemistry, Zhengzhou University,
Zhengzhou 450052, PR China.
Here, we report fascinating interwoven helices based on a ZnII
complex, namely [Zn(bpip)SO4]n (1), which displays chiral self-
E-mail address: houhongw@zzu.edu.cn (H. Hou).
1387-7003/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2012.01.021

24
J. Wu et al. / Inorganic Chemistry Communications 19 (2012) 23–26
Fig. 1. View of one layer of compound 1. C atoms (dark gray), O atoms (red), S atoms (yellow), Zn atoms (green). All hydrogen atoms are omitted for clarity.
assembly into an infinite double-stranded helical coordination poly-
mer consisting of two single-stranded helices of the same handedness
made from an achiral ligand bpip [22]. These chiral infinite double-
stranded helical chains are further interwoven by the 1D Zn–SO4–Zn
chains to form a 3D architecture. Although some examples of double
stranded helical coordination networks in the spontaneous resolution
process have been reported, the double stranded helical coordination
networks further interwoven with infinite linear M–SO4–M chains
have not been reported until now. Furthermore, the steady state fluo-
rescence spectra and the thermal stability of the complex have been
determined.
A single crystal X-ray diffraction study performed on 1 revealed
that the complex crystallizes in the tetragonal chiral space group
P41212 and contains a fascinating tridimensional polymeric architec-
ture consisting of three interwoven nets [23]. The symmetric unit of
1 consists of one Zn center, two SO42− ions, and two bpip ligands
(Fig. S1). Zn atom adopts a slightly distorted tetrahedral coordination
geometry through bonding to two O atoms (O3 and O5) from SO42−
ions and two N atoms (N1 and N3) from two ligands. The Zn–O
bond lengths (1.936(3)–2.387(2) ) and the Zn–N bond lengths
(2.024(3)–2.038(3) ) are similar to those found in other related
structures [24]. Each SO42− ion acts as a bidentate bridging linker to
connect two Zn centers leading to the formation of a single-
stranded with the O–Zn–O angle is 106.65(11)°.
As seen in Fig. 1, the unit of 1 consists of two bpip ligands with the
dihedral angles being 45.4°, and each ligand exhibits two types of
bridging modes (Mode a and b), which are important for the forma-
tion of the infinite double-helical structure. One kind of ligand
(Mode a) bridges two Zn atoms along the 1D–S–O–Zn–O–S– chain.
The other kind of ligand (Mode b) with two different bridging direc-
tions links two Zn atoms from two adjacent –S –O –Zn –O –S– chains.
The most fascinating topological feature in 1 is the ligands bridge
the Zn atoms to form a chiral infinite double-helical chain with the
P (right-hand) configuration (Fig. 2a). Each chain is rotated by 90°
along the c axis on passing to each successive layer, in a 41 helical dis-
position, thus resulting in a chiral network. The helical pitch, given by
the distance between equivalent atoms generated by one full rotation
of the 41 screw axis, is 19.86 Å.
In general, the most important feature of the helix is its chirality.
Right-handed (P) and left-handed (M) helices are nonidentical mirror
images. The two single-stranded infinite helices in 1 are of the same P
handedness and are intertwined to form a chiral infinite double-
Fig. 2. (a) View of the double-stranded helices showing the same chirality for the two chains of each double-stranded helix; (b) View of the double-stranded helical chains inter-
woven with the 1D S–O–Zn–O–S chains; (c) 3D framework of 1 showing its chiral layers and interwoven structure. All hydrogen atoms are omitted for clarity.

J. Wu et al. / Inorganic Chemistry Communications 19 (2012) 23–26
25
helical structure. The aromatic rings in the ligand at each side of the
helix are arranged in a parallel fashion with an inner-ring distance
of 9.47 Å; adjacent chiral helices are packed in a zipperlike, off-set
fashion into 2D layers parallel to the bc plane (Fig. 2b). These chiral
infinite double-stranded helical chains are further linked by the 1D
S–O–Zn–O–S chains to form a 3D architecture (Fig. 2c). It is worth
noting that all helicals are of the same chirality and are packed in a
parallel manner, leading to a noncentrosymmetric and chiral solid.
In such a case, this coordination polymer 1 is noncentrosymmetric
and chiral even if it contains no chiral molecular unit. Though numer-
ous infinite double helices have been structurally characterized to
date, chiral 3D double helices of the same handedness based on achi-
ral ligands are quite rare.
The driving force for the formation of the double helical arrange-
ment is likely the definite directions of the ligand. The bpip group is
a rigid and angular diptopic ligand which has two “arms” with 120°
angle to act as an ideal half-cycle, and at the end of each “arm”
there is a pyridyl donor group which is convenient for bridging
metal centers to form an integrated macrocycle. Besides, the distor-
tion from the planarity of the two terminal pyridine rings and the
freedom rotation of the amido-N to 3-pyridyl-C bond could make
the ligands may be locked in twisting configurations. In addition,
the 1D S–O–Zn–O–S chains interwoven with the double-stranded he-
lical chains further stabilize the double helical arrangement.
as diamond (66), NbO (6482), PtS, CdSO4 (658), dense (759), etc.
[25–28].
To conform whether the crystal structure is truly representative of
the bulk materials, the XRD powder patterns for compound 1 has
been collected on
a PANalytical X'prtPro diffractometer using
graphite-monochromated Cu-Kα radiation in the angular range
2θ=5–50°. The XRD of powder pattern was fully coincident with
the compound 1 that calculated from its sing crystal structure data,
so it exists as a single phase (Fig. S2).
The solid-state photo luminescent behaviors of the free ligand
bpip and complex 1 have been investigated at room temperature.
As shown in Fig. S3, excitation at 328 nm leads to broad fluorescence
signals with the emission maxima at approximately 440 nm for the
⁎
free ligand bpip, which is probably attributable to the π →n or
⁎
π →π transitions. In comparison, complex 1 displays an emission
band centered at about 390 nm when excited at 325 nm. Such fluo-
rescence behaviors suggest the emissions of 1 are neither metal-to-
ligand charge transfer (MLCT) nor ligand-to-metal charge transfer
(LMCT), but they may be assigned to intraligand transition because
Zn(II) is difficult to oxidize or reduce due to its d10 configuration.
The partial quenching of fluorescence emission in 1 may be due to
the fact that the introduction of the metal ions and sulfate anions reduce
the rigidity of the polymer which causes a decrease in the conjugate de-
gree of whole molecules. In addition, the weak interactions, especially
the strong hydrogen-bonding interactions, also play an important role
in weakening the fluorescence intensity of the supermolecules [29].
The thermal properties of the complex 1 were investigated. As
shown in Fig. 4, TG curve of complex 1 exhibits that it is stable up
to 467.4 °C. The surprising thermal stability of 1 is mainly due to the
interwoven structure of double-stranded helices and extended
metal-SO4-metal chains. From 467.4 °C to 552.2 °C, it keeps losing
weight because the structure collapsed resulting from the removing
organic ligand. The curve observed from 552.2 °C to 676.9 °C is caused
by the decomposition of SO42− ions. Finally a white residue of ZnO
(observed 18.26%, calculated 16.97%) remained.
When the tetrahedral coordinated Zn(II) centers are regarded as
nodes, and the organic ligands and SO42− ions are regarded as connec-
tors, the network of the complicated structure can be described topo-
logically in
a straight-forward way with node-and-connector
approach. As shown in Fig. 3, the 1D S–O–Zn–O–S chains on the op-
posing ends of any given bpip ligands are disposed leading to the
3D framework structure which has a 65.10 topology. The 65.10 topol-
ogy in 1 is a rare tetrahedrally four-connected net, related but differ-
ent from the other nets for a 3D network of four-connected nets, such
We attempted to measure the CD spectrum of the sample to un-
derstand the P and M percentage distribution of the chiral crystals,
which apparently needs further study.
In conclusion, the compound 1 reported here is an interesting ex-
ample of a homochiral 3D chiral coordination polymer consisting of
two single-stranded helices with the same handedness based on an
achiral ligand bpip. The adjacent chiral double helices are of the
same P handedness and are packed in a parallel fashion. These chiral
infinite double-stranded helical chains are further interwoven with
Fig. 3. An unusual (65, 10) net of compound 1 viewed along different directions (top)
and a convenient view of the essential circuits of the vertex (bottom).
Fig. 4. Thermogravimetric curve (TG and DSC) of compound 1.

26
J. Wu et al. / Inorganic Chemistry Communications 19 (2012) 23–26
[14] T. Ezuhara, K. Endo, Y. Aoyama, Helical coordination polymers from achiral com-
ponents in crystals. Homochiral crystallization, homochiral helix winding in the
solid state, and chirality control by seeding, J. Am. Chem. Soc. 121 (1999)
3279–3283.
[15] L. Han, M.C. Hong, Recent advances in the design and construction of helical coor-
dination polymers, Inorg. Chem. Commun. 8 (2005) 406–419.
the 1D S–O–Zn–O–S chains to form a 3D framework structure which
has a rare 65.10 topology. On the basis of the results of TG/DSC ana-
lyses, the structure is thermally stable up to ~467.4 °C.
Acknowledgments
[16] O.R. Evans, W.B. Lin, Crystal engineering of NLO materials based on metal-organic
coordination networks, Acc. Chem. Res. 35 (2002) 511–522.
[17] B. Park II, I.S. Chun, Y. Lee, K. Park, O. Jung, Supramolecular framework with two
different kinds of channels via self-assembly of 1D coordination polymers in a
prismatic manner, Inorg. Chem. 45 (2006) 4310–4312.
[18] X.M. Chen, G.F. Liu, Double-stranded helices and molecular zippers assembled
from single-stranded coordination polymers directed by supramolecular interac-
tions, Chem. Eur. J. 8 (2002) 4811–4817.
[19] Z.Q. Qin, M.C. Jennings, R.J. Puddephatt, Alternating right- and left-handed helical
loops in a self-assembled polymer: direct observation of ring-opening polymeri-
zation of a macrocyclic gold complex, Chem. Eur. J. 8 (2002) 735–738.
[20] N.N. Adarsh, D.K. Kumar, P. Dastidar, Metalla-macro-tricyclic cryptands: anion
encapsulation and selective separation of sulfatevia in situ crystallization, Crys-
tEngComm 11 (2009) 796–802.
[21] L.H. Huang, J. Wu, F.F. Pan, Catena-Poly[[[diiodidomercury(II)]-μ -N, N'-di-3-pyr-
idylpyridine-2,6-dicarboxamide] dimethylformamide solvate], Acta Crystallogr.
64 (2008) 1533.
This project is supported by China Postdoctoral Science Foundation
(20090450095 and 201003401) and the Student Innovative Funded
Projects of Zhengzhou University (2010cxsy095).
Appendix A. Supplementary material
Crystallographic data for structural analysis have been deposited
with the Cambridge Crystallographic Data Center, CCDC reference num-
ber 640706 for complex 1. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ, UK;
fax: (+44) 1223 336 033; or deposit@ccdc.cam.ac.uk). Details on the
view of the building unit of structure 1, powder X-ray diffractograms
for 1, solid-state emission spectra of bpip and 1, selected bond lengths
and bond angles are listed in the supplementary content.
[22] Synthesis of 1:
A mixture of ligand bpip (38.1 mg, 0.1 mmol), ZnSO4·7H2O
(28.7 mg, 0.1 mmol), and H2O/CH3OH (v/v 1:5, 10 mL) was sealed in a Parr
Teflon-lined stainless steel vessel and heated to 120 °C for 3 days and cooled to
room temperature in 12 h. Block crystals were isolated by filtration and washed
with distilled water and dried in air to give the product. Yield: 75% based on
ZnSO4·7H2O. Anal. Calcd: C36H28N8O12S2Zn2: C, 45.06; H, 2.94; O, 20.01; N,
11.68. Found: C, 45.12; H, 2.89; O, 19.98; N, 11.73. IR (KBr)/cm-1: 3302 (m),
3177(w), 3062 (w), 1677 (s), 1589(s), 1436 (s), 1300 (s), 1116 (m), 821 (s),
719 (s), 698 (s), 607 (m), 421 (m).
Supplementary data to this article can be found online at doi:10.
1016/j.inoche.2012.01.021.
References
[23] Single crystals of 1 were selected for indexing and intensity data collection on a
Rigaku Saturn 724 CCD diffractometer with graphite monochromatic Mo-Ka radi-
ation (λ=0.71073 Å). The data were collected at a temperature of 293(2)K and
corrected for Lorentz-polarization effects. A correction for secondary extinction
was applied. The structures were solved by direct methods and expanded using
Fourier techniques. The non-hydrogen atoms were refined anisotropically. Hy-
drogen atoms were included but not refined. The final cycle of full-matrix least-
squares refinement was based on observed reflections and variable parameters.
All calculations were performed using the SHELX 97 Crystallographic software
package. Crystal data for 1: Mr=959.52, tetragonal, space group P4(1)2(1)2,
a=13.4378(19) Å, b=13.4378(19)Å, c=19.864(4)Å, α=β=γ=90°,
[1] M. Albrecht, “Let's Twist Again”—double-stranded, triple-stranded, and circular
helicates, Chem. Rev. 101 (2001) 3457–3497.
[2] M. Albrecht, Artificial molecular double-stranded helices, Angew. Chem. Int. Ed.
44 (2005) 6448–6451.
[3] H.B. Qiu, Y. Inoue, S.N. Che, Supramolecular chiral transcription and recognition
by mesoporous silica prepared by chiral imprinting of a helical micelle, Angew.
Chem. Int. Ed. 48 (2009) 3069–3072.
[4] C. Pigue, G. Bernardinelli, G. Hopfgartner, Helicates as versatile supramolecular
complexes, Chem. Rev. 97 (1997) 2005–2062.
[5] T. Maeda, Y. Furusho, S. Sakurai, J. Kumaki, K. Okoshi, E. Yashima, Double-strand-
ed helical polymers consisting of complementary homopolymers, J. Am. Chem.
Soc. 130 (2008) 7938–7945.
[6] L. Han, H. Valle, X.H. Bu, Homochiral coordination polymer with infinite double-
stranded helices, Inorg. Chem. 46 (2007) 1511–1513.
[7] S.Q. Zang, Y. Su, Y.Z. Li, Z.P. Ni, H.Z. Zhu, Q.J. Meng, Interweaving of triple-helical
and extended metal-o-metal single-helical chains with the same helix axis in a
3D metal-organic framework, Inorg. Chem. 45 (2006) 3855–3857.
[8] M. Ikeda, Y. Tanaka, T. Hasegawa, Y. Furusho, E. Yashima, Construction of double-
stranded metallosupramolecular polymers with a controlled helicity by combina-
tion of salt bridges and metal coordination, J. Am. Chem. Soc. 128 (2006)
6806–6807.
V=3587.0(10)Å3, Z=4,
ρ , F(000)=1952, GOF=1.162,
calcd. =1.777 gcm−3
R1 =0.0422, wR2=0.0902 [I>2σ(I)].
[24] L.F. Ma, C.P. Li, L.Y. Wang, M. Du, Zn(II) and Cd(II) Coordination polymers assem-
bled from a versatile tecton 5-Nitro-1,2,3-benzenetricarboxylic acid and N,N'-
Donor ancillary coligands, Cryst. Growth Des. 10 (2010) 2641–2649.
[25] B. Chen, F.R. Fronczek, A.W. Maverick, Solvent-dependent 44 square grid and
64.82 NbO frameworks formed by Cu(Pyac)2 (bis[3-(4-pyridyl)pentane-2,4-dio-
nato]copper(II)), Chem. Commun. (2003) 2166–2167.
[26] B. Chen, M. Eddaoudi, T.M. Reineke, J.W. Kampf, M. O'Keeffe, O.M. Yaghi,
Cu2(ATC)·6H2O: design of open metal sites in porous metal-organic crystals
(ATC: 1,3,5,7-Adamantane Tetracarboxylate), J. Am. Chem. Soc. 122 (2000)
11559–11560.
[9] A. Jouaiti, M.W. Hosseini, N. Kyritsakas, Molecular tectonics: infinite cationic dou-
ble stranded helical coordination networks, Chem. Commun. (2003) 472–473.
[10] L. Carlucci, G. Ciani, D.W. Gudenberg, D.M. Proserpio, Self-assembly of infinite
double helical and tubular coordination polymers from Ag(CF3SO3) and 1,3-
Bis(4-pyridyl)propane, Inorg. Chem. 36 (1997) 3812–3813.
[11] R.H. Wang, L.J. Xu, X.S. Li, Y.M. Li, Q. Shi, Z.Y. Zhou, M.C. Hong, A.S.C. Chan, New
types of homochiral helical coordination polymers constructed by exo-
bidentate binaphthol derivatives, Eur. J. Inorg. Chem. (2004) 1595–1599.
[12] B. Schmaltz, A. Jouaiti, M.W. Hosseini, A.D. Cian, Double stranded interwound in-
finite linear silver coordination network, Chem. Commun. (2001) 1242–1243.
[13] P.A. Maggard, C.L. Stern, K.R. Poeppelmeier, Understanding the role of helical
chains in the formation of noncentrosymmetric solids, J. Am. Chem. Soc. 123
(2001) 7742–7743.
[27] B. Moulton, H. Abourahma, M.W. Bradner, J. Lu, G.J. McManus, M.J. Zaworotko, A
new 65.8 topology and a distorted 65.8 CdSO4 topology: two new supramolecular
isomers of [M2(bdc)2(L)2]n coordination polymers, Chem. Commun. (2003)
1342–1343.
[28] H. Chun, D. Kim, D.N. Dybtsev, K. Kim, An unprecedented twofold interpenetrating
(3,4)-connected 3-D metal–organic framework, Angew. Chem. Int. Ed. 43 (2004)
971.
[29] S.L. Zheng, M. Gembicky, M. Messerschmidt, P.M. Dominiak, P. Coppens, Effect of
the environment on molecular properties: synthesis, structure, and photolumi-
nescence of Cu(I) bis(2,9-dimethyl-1,10-phenanthroline) nanoclusters in eight
different supramolecular frameworks, Inorg. Chem. 45 (2006) 9281–9289.