A novel 1D → 2D interdigitated framework directed by hydrogen bonds

Article abstract of DOI:10.1016/j.molstruc.2011.01.036

A novel Zn(ΙI) complex, [Zn(L1)(bpe)] (1) (H₂L1 = 5-(benzyloxy) isophthalic acid, bpe = 1,2-bis(4-pyridyl)ethane) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, IR and X-ray powder diffraction (PXRD).

Full text of DOI:10.1016/j.molstruc.2011.01.036

Journal of Molecular Structure 991 (2011) 31–34
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
A novel 1D ? 2D interdigitated framework directed by hydrogen bonds
Jin-Xia Yang a,b, Xin Zhang a,b, Jian-Kai Cheng a, Yuan-Gen Yao a,
⇑
a State Key Laboratory of Structural Chemistry, Fujian Institute of Research On the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s Republic of China
b Graduate School, Chinese Academy of Sciences, Beijing 100039, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel Zn(II) complex, [Zn(L1)(bpe)] (1) (H2L1 = 5-(benzyloxy) isophthalic acid, bpe = 1,2-bis(4-pyri-
dyl)ethane) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction,
IR and X-ray powder diffraction (PXRD). Compoud 1 features a one-dimensional (1D) open-ended tubular
framework. These adjacent tubular frameworks are interdigitated into a two-dimensional (2D) supramo-
lecular framework directed by hydrogen bonds. Moreover, this compound exhibits intense blue photolu-
minescence at room temperature.
Received 13 December 2010
Received in revised form 6 January 2011
Accepted 21 January 2011
Available online 28 January 2011
Keywords:
Ó 2011 Elsevier B.V. All rights reserved.
Zinc(II) compound
Hydrothermal reaction
Tubular framework
Hydrogen bond
Photoluminescence
1. Introduction
tigate its coordination chemistry and construct novel supramolec-
ular structure with promising properties, we exploit H2L1, flexible
In recent years crystal engineering of coordination polymers has
been an active research area due to their fascinating structure and
potential applications as functional solid materials [1–5]. Gener-
ally, covalent interactions for the construction of coordination
polymers are the most effective force. In addition, noncovalent
N-containing ligand (bpe) and Zn(NO3)2Á6H2O as reactants, and
successfully obtained a novel zinc(II) complex, [Zn(L1)(bpe)] (1).
In the structure of 1, it features a 1D open-ended tubular
framework, which is further interdigitated into an interesting 2D
supromolecular framework directed by hydrogen bonds. Moreover,
this compound exhibits intense blue photoluminescence at room
temperature.
interactions (such as hydrogen bonding interactions, p–p stacking
interactions, halogen–halogen interactions and so on) which are
described as ‘supramolecular glues’ are often used as structural-
directing tools in generating many novel supramolecular structure
with promising properties [6–10]. Therefore, versatile functional
organic ligands (such as N- or O-containing ligands) which have
strong coordination ability as well as providing the hydrogen bond
2. Experimental
2.1. Materials and methods
acceptors/donors and p-conjugated systems are often employed in
All chemicals were purchased commercially and used without
further purification except for H2L1. The H2L1 was synthesized
according to the previously reported procedure [14]. X-ray intensi-
ties were collected on Oxford Xcalibur E diffractometer with
construction of novel supramolecular framework [11–13].
5-(Benzyloxy)isophthalic acid (H2L1) (Scheme 1), as a dicarbox-
ylate ligand, has been synthesized before [14,15]. Compared to the
5-hydroxy-isophthalic acid, it not only can provides hydrogen
graphite monochromated Mo K
a radiation (k = 0.71073 Å). Ele-
bond acceptors/donors and
p-conjugated systems, but also can
mental analyses (C, H and N) were performed on an EA1110
CHNS-0 CE Elemental Analyzer. IR spectra (KBr pellet) was re-
corded on a Nicollet Magna 750FT-IR spectrometer. Fluorescence
spectra of the solid samples were performed on an Edinburgh Ana-
lytical instrument FLS920.
exhibits a variety of conformations according to geometric require-
ments of metal ions due to the flexible CH2–O spacer between the
two phenyl rings. More interestingly, the benzyl of the H2L1 ligand
also can act as template in the self-assembly process [16]. To inves-
⇑
Corresponding author. Address: State Key Laboratory of Structural Chemistry,
2.2. Synthesis
Fujian Institute of Research On the Structure of Matter, Chinese Academy of
Sciences, Fuzhou, Fujian 350002, People’s Republic of China. Tel.: +86 591
83711523; fax: +86 591 83714946 (Y.-G. Yao).
A mixture of Zn(NO3)2Á6H2O (0.297 g, 1.0 mmol), H2L1 (0.136 g,
E-mail address: yyg@fjirsm.ac.cn (Y.-G. Yao).
0.5 mmol), bpe (0.092 g, 0.5 mmol), and NaHCO3 (0.084, 1.0 mmol)
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.01.036

32
J.-X. Yang et al. / Journal of Molecular Structure 991 (2011) 31–34
Table 2
Selected bond lengths (Å) and angles (°) of compound 1.
Zn(1)–O(1)
1.953(4)
Zn(1)–O(4)a
1.985(3)
Zn(1)–N(2)
2.033(4)
Zn(1)–N(1)
2.075(5)
O(1)–Zn(1)–O(4)a
O(4)a–Zn(1)–N(2)
O(1)–Zn(1)–N(1)
100.26(16)
113.97(16)
107.15(17)
O(1)–Zn(1)–N(2)
O(1)–Zn(1)–N(1)
O(4)a–Zn(1)–N(1)
111.67(16)
107.15(17)
108.57(16)
a
Symmetry codes: x À 1, y, z.
structure determination are presented in Table 1. Selected bond
lengths and angles are listed in Table 2.
3. Results and discussion
Scheme 1. The structure of the H2L1 ligand.
3.1. Description of the structure
Single-crystal X-ray structural analysis reveals that Compound
1 exhibits a 1D open-ended tubular architecture. There are one
crystallographically independent Zn(II) ion, one L1 ligand and
one bpe ligand in the asymmetric unit. As shown in Fig. 1, each
Zn(II) ion is in a tetrahedral {ZnO2N2} coordination environment,
surrounded by two N atoms from two different bpe ligands and
two O atoms from two different L1 ligands. The Zn–O distance is
1.982(3) Å and the Zn–N distance is in the range of 2.032(4)–
2.077(4) Å. These Zn–O/N distances are in the normal range of
those observed in other Zn(II)-complexes [19]. Interestingly, rare
gauche conformation of the bpe ligand, which may be benefit to
construct open-ended tubular architecture, is observed in com-
pound 1. The two pyridyl rings from the same bpe unit twist by
53.154(1)° from each other. Such gauche conformational bpe li-
gands bridge two different Zn(II) ions forming a cyclic closed struc-
ture with S2-symmetry (Fig. 2a). Then, adjacent closed structures
are bridged by the L1 ligands forming an open-ended tubular archi-
tecture propagating along crystallographical a axis (Fig. 2b). The
dimension of the nanotube is approximately 8.1232(8) Â
10.8137(6) Å. Obviously, each L1 ligand in 1 acts as a bidentate li-
gand with its two carboxylate groups both in monodentate mode.
The phenyls of the anionic, aromatic L1 ligands in the 5-sites pro-
ject out and arrange on both sides of the tube (Fig. 2b). The twist
angle of L1 between the two phenyl rings is 79.355(2)°. To the best
of our knowledge, such metal–organic coordination polymers con-
taining gauche conformational bpe ligands remain rarely be
reported.
in molar ratio 2:1:1:2 and 15 ml H2O was placed in a Parr Teflon-
lined stainless steel vessel (25 cm3), then the vessel was sealed and
heated to 160 °C. The temperature was hold for 60 h, then the ves-
sel was cooled to room temperature over 60 h to lead to the forma-
tion of colorless crystals of 1 (yield: 65% based on Zn). Anal. Calc.
for 1, C27H22N2O5Zn: C, 62.32; H, 4.23; N, 5. 39%. Found: C,
62.38; H, 4.18, N, 5.38%. IR (solid KBr pellet, v/cmÀ1) for compound
1: 3127(m), 2891(m), 1642(s), 1612(s), 1561(s), 1448(s), 1367(m),
1258(m), 1131(m), 1062(w); 852(vw), 775(w), 711(vw), 612(w),
554(m), 429(vw).
2.3. X-ray crystallography
The X-ray single-crystal structure analysis of 1 was performed
on
a Oxford Xcalibur E diffractometer (Mo Ka radiation,
k = 0.71073 Å, graphite monochromator) at 293(2) K. Empirical
absorption corrections were applied to the data using the SADABS
program [17]. The structure was solved by the direct method and
refined by the full-matrix least-squares on F2 using the SHELXL-
97 program [18]. All of the non-hydrogen atoms were refined
anisotropically, and the hydrogen atoms attached to carbon were
located at their ideal positions. Experimental details for the
Table 1
Crystallographic data for compound 1.
It is noteworthy that the distance between the adjacent rings of
the tube is 10.1698(8) Å, indicating that large space exists between
the adjacent rings. CH/n hydrogen bonding is an interesting inter-
action and has been proved to act as a structural-directing tool
Empirical formula
Temperature (K)
Crystal color
Crystal size
Formula weight
Crystal system
Space group
a (Å)
C27H22N2O5Zn
293(2)
Colorless
0.20 Â 0.15 Â 0.10 mm3
519.86
Monoclinic
P21/c
10.1698(3)
b (Å)
11.9741(5)
c (Å)
b
Volume (Å3)
20.9721(10)
109.483(4)
2407.63(17)
o
Z
4
Density (calculated)
1.434
1.063
1058
Abs. coeff. (mmÀ1
F(000)
)
Refinement method
Reflections collections
Independent reflections
h range for data collection
h, k, l range
Full-matrix least-squares on F2
8146
4208 [(R(int) = 0.0306)]
2.65–24.99
À12 6 h 6 10, À14 6 k 6 13, À24 6 l 6 21
Goodness-of-fit on F2
Final R indices [I 2 sigma(I2)]
R (all data)
0.974
R = 0.0569, wR = 0.1615
R = 0.0911, wR = 0.1706
Fig. 1. ORTEP drawing of compound 1 (30% thermal ellipsoids). Hydrogen atoms
associated with C atoms have been omitted for clarity. Symmetry codes: (A) À1 + x,
y, z; (B) 1 À x, Ày, Àz.
Largest difference peak and hole 1.206 and À0.567 e/Å3

J.-X. Yang et al. / Journal of Molecular Structure 991 (2011) 31–34
33
Fig. 2. (a) Cyclic closed structure. (b) 1D open-ended tubular framework propagating along crystallographical a axis (the rod represents the tube). (c) Hydrogen interactions
of the framework view along a axis. (d) 2D interdigitated framework directed by hydrogen bonds (dashed lines represent hydrogen bonds).
[20]. Therefore, through the direction of the hydrogen bonds be-
tween the carboxylate O and C atoms (C25ÁÁÁO4b and C14aÁÁÁO2)
(Fig. 2c), the large space are effectively occupied by the phenyls
of the L1 ligands from adjacent tubular architecture, leading to
the final 2D interdigitated framework (Fig. 2d). The detailed hydro-
gen bond parameters are list in Table 3. Therefore, hydrogen bonds
play an important direction role in the final 2D interdigitated
framework. Although supramolecular frameworks constructed by
hydrogen bonds have been widely investigated [21–23], such un-
ique 1D ? 2D interdigitated framework directed by hydrogen
bonds has not been reported before.
3.2. PXRD patterns and photoluminescent properties
As shown in Fig. 3, the experimental PXRD pattern of 1 is in
good agreement with the simulated one except for the relative
intensities variations because of the preferred orientation of the
Fig. 3. Experimental and simulated XRD patterns for compound 1.
crystals, indicating that compound 1 is in a pure phase.
Considering the excellent photoluminescent properties of d10
complexes, the solide-state luminescence of compound 1 was
investigated at room temperature. As shown in Fig. 4, compound
1 exhibits intense blue emission band at 460 nm when excited at
359 nm. To understand the nature of the emission band, the lumi-
nescent properties of the ligand H2L1 and bpe were also investi-
gated at room temperature. However, no obvious emission bands
were observed in the range of 400–600 nm. Therefore, the emis-
sion band of the title compound may be attributed to the ligand-
to-metal-charge-transfer (LMCT). These observations indicates
that metal centers may play an important affection on the photo-
luminescent properties of the coordination polymers, and com-
pound 1 may be an excellent candidate for potential photoactive
materials.
Table 3
Hydrogen-bonding geometrical parameters (Å, °) of compound 1.
DÀHÁÁÁA
DÀH
0.93
0.93
HÁÁÁA
2.64
2.53
DÁÁÁA
3.3976(8)
3.4063(3)
\ DÀHÁÁÁA
139.582(5)
158.743(5)
C14aÀH14AÁÁÁO2
C25ÀH25AÁÁÁO4b
a
Symmetry codes:3 À x, 0.5 + y, 0.5 À z.
Symmetry codes:2 À x, 0.5 + y, 0.5 À z.
Fig. 4. Emission spectrum and excitation spectrum (inset) of 1 in the solid-state at
room temperature.
b

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J.-X. Yang et al. / Journal of Molecular Structure 991 (2011) 31–34
4. Conclusions
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into a unique 2D supramolecular framework.
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Appendix A. Supplementary material
CCDC No. 804453 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/data_request/cif, by emailing data_request@
ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic
Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK. Fax:C44
1223336033. Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.molstruc.
2011.01.036.
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