Two Zn coordination polymers with meso-helical chains based on mononuclear or dinuclear cluster units

Article abstract of DOI:10.1016/j.jssc.2016.04.021

Two zinc coordination polymers {[Zn₂(TPPBDA)(oba)₂]·DMF·1.5H₂O}_n (1), {[Zn(TPPBDA)_1/2(tpdc)]·DMF}_n (2) have been synthesized by zinc metal salt, nanosized tetradentate pyridine ligand with flexible or rigid V-shaped carboxylate co-ligands. These complexes were characterized by elemental analyses and X-ray single-crystal diffraction analyses. Compound 1 is a 2-fold interpenetrated 3D framework with [Zn₂(CO₂)₄] clusters. Compound 2 can be defined as a five folded interpenetrating bbf topology with mononuclear Zn²⁺. These mononuclear or dinuclear cluster units are linked by mix-ligands, resulting in various degrees of interpenetration. In addition, the photoluminescent properties for TPPBDA ligand under different state and coordination polymers have been investigated in detail.

Full text of DOI:10.1016/j.jssc.2016.04.021

Journal of Solid State Chemistry 239 (2016) 53–57
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Two Zn coordination polymers with meso-helical chains based on
mononuclear or dinuclear cluster units
a
a
a
a
Ling Qin a,b,c, , Wen-Cheng Qiao , Wei-Juan Zuo , Si-Ying Zeng , Cao Mei ,
n
Chang-Jiang Liu a
a Department of Chemical Engineering and Food Processing, Xuancheng Campus, Hefei University of Technology, Xuancheng 242000, Anhui, PR China
b Jiangsu Engineering Technology Research Center of Environmental Cleaning Materials (CEM), School of Environmental Sciences and Engineering, Nanjing
University of Information Science and Technology, PR China
c State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing National Laboratory of Microstructures, Nanjing
University, Nanjing 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two zinc coordination polymers {[Zn2(TPPBDA)(oba)2] ꢀ DMF ꢀ 1.5H2O}n (1), {[Zn(TPPBDA)1/2(tpdc)] ꢀ
DMF}n (2) have been synthesized by zinc metal salt, nanosized tetradentate pyridine ligand with flexible
or rigid V-shaped carboxylate co-ligands. These complexes were characterized by elemental analyses and
X-ray single-crystal diffraction analyses. Compound 1 is a 2-fold interpenetrated 3D framework with
[Zn2(CO2)4] clusters. Compound 2 can be defined as a five folded interpenetrating bbf topology with
mononuclear Zn2þ. These mononuclear or dinuclear cluster units are linked by mix-ligands, resulting in
various degrees of interpenetration. In addition, the photoluminescent properties for TPPBDA ligand
under different state and coordination polymers have been investigated in detail.
Received 15 March 2016
Received in revised form
13 April 2016
Accepted 14 April 2016
Available online 14 April 2016
Keywords:
Coordination polymer
Meso-helical chains
Interpenetration degree
Mononuclear Or dinuclear cluster units
& 2016 Elsevier Inc. All rights reserved.
1. Introduction
since high surface area and porosity are generally most desired in
porous materials. It is noteworthy that using rod-shaped or other
In the past two decades, the design and synthesis of co-
ordination polymers (CPs) by self-assembly of metal ions as con-
necting nodes and organic ligands as linkers have attracted sci-
entific attention [1–5]. Coordination polymer is an ideal example
of inorganic crystal engineering with various noncovalent inter-
actions to obtain useful function materials with different di-
mensionalities and topologies and provide an important interface
between synthetic and material chemistry. However, predictive
coordination chemistry is still a challenge and deserves our careful
study, because there are many facts that can affect the structure,
such as, the counter anions of metal salts, geometric requirements
of metal atoms, pH, solvent, template and the structure of the
organic ligand [6–11]. As we know, the use of long linkers for the
design of frameworks often affords interpenetrated MOFs with
smaller pores [12–14]. Although interpenetration usually makes
MOFs robust, it negatively reduces the size of open pores. Highly
interpenetrated nets typically have low porosity and surface area,
and high density, negatively affecting the potential applications
secondary building units (SBUs) can reduce the interpenetration,
which provides MOFs with rigid architectures and permanent
porosity [15–17]. Herein we have synthesized two new zinc co-
ordination polymers under solvothermal condition, that is,
{[Zn2(TPPBDA)(oba)2] ꢀ DMF ꢀ 1.5H2O}n (1), {[Zn(TPPBDA)1/2(tpdc)]
ꢀ DMF}n (2) based on Zn (II) cation, nanosized neutral tetradentate
ligand TPPBDA (N,N,N′,N′-tetrakis (4-(4-pyridine)-phenyl) biphe-
nyl-4,4′-diamine) [18–20] and carboxylate co-ligands (H2oba
¼4,4′-oxybis(benzoate) or H2tpdc¼4,4″-dicarboxyl-(1,1′,3′,1″)-ter-
phenyl, DMF
¼
N,N-dimethylformamide). In compounds 1-2,
Zn2þcations act as the mononuclear or dinuclear SBUs, which are
interconnected by TPPBDA and carboxylate co-ligands, resulting in
structural diversity and various degrees of interpenetration.
2. Experimental section
2.1. Reagents and physical measurements
All chemicals and solvents used in the syntheses were of re-
agent grade and used without further purification. The ligand
H2tpdc was prepared by the literature methods [21]. The ligand
TPPBDA was prepared as follows on the basis of palladium-
n
Corresponding author at: Department of Chemical Engineering and Food Pro-
cessing, Xuancheng Campus, Hefei University of Technology, Xuancheng 242000,
Anhui, PR China
E-mail address: qinling@hfut.edu.cn (L. Qin).
http://dx.doi.org/10.1016/j.jssc.2016.04.021
0022-4596/& 2016 Elsevier Inc. All rights reserved.

54
L. Qin et al. / Journal of Solid State Chemistry 239 (2016) 53–57
catalyzed cross-coupling reaction.
2.3. Single-crystal structure determination
Preparation of N, N, N′, N′-tetrakis(4-bromophenyl)biphenyl-
4,4′-diamine: An oven-dried 500 mL Schlenk flask was charged
with tris(4-bromophenyl)amine (24.1 g, 50 mmol), then ether
(350 mL) and N,N,N′,N′-tetramethylethylenediamine (8.2 mL) were
added through a rubber septum. The reaction mixture was cooled
to ꢁ78 °C. Upon slow addition of a n-BuLi solution (34 mL, 1.6 M in
hexanes, 55 mmol), and the mixture was stirred for 1 h at ꢁ78 °C.
Solid CuCl2 (10.8 g, 80 mmol) was added, and the reaction mixture
was then allowed to slowly warm to room temperature and stirred
for an additional 10 h. The reaction mixture was exposed to air,
stirred for 30 min and concentrated in vacuo. Approximately
chloroform (100 mL) and water (100 mL) were added, and the
layers were separated. The aqueous layer was subsequently wa-
shed with chloroform (50 mL) three times. The organic extracts
were combined, dried with MgSO4, and filtered. The volatile
chloroform was removed under vacuum to leave a green solid.
Purification by column chromatography (petroleum ether) yielded
the pure product as a white solid (10.1 g, 50%). 1HNMR (DMSO-d,
500 MHz, 25 °C): 7.61 (d, 4H), 7.5 (d, 8H), 7.09 (d, 4H), 7.0 (d, 8H).
Preparation of N,N,N′,N′-tetrakis (4-(4-pyridine)-phenyl) bi-
phenyl-4,4′-diamine (TPPBDA): A 500 mL Schlenk flask was evac-
uated and backfilled with nitrogen and charged with N, N, N′, N
′-tetrakis(4-bromophenyl)biphenyl-4,4′-diamine (8 g, 10 mmol),
the pyridine-4-boronic acid (8.41 g, 70 mmol), and K2CO3
(9.66 mg, 70 mmol). The flask was evacuated and backfilled with
nitrogen, then Pd(PPh3)4 (2.2 mg, 0.05 mmol, 5.0 mol%) and 1,4-
dioxane / H2O (V:V¼3:2) were added through a rubber septum.
The reaction mixture was heated to 95 °C with stirring until the
starting N, N, N′, N′-tetrakis(4-bromophenyl) biphenyl-4,4′-dia-
mine had been completely consumed as judged by TLC. The re-
action mixture was then cooled to room temperature and the 1,4-
dioxane was removed under vacuum. The aqueous mixture was
extracted with chloroform (50 mL). The combined organic layers
were dried over anhydrous MgSO4, filtered, and concentrated in
vacuo. The crude material was purified by chromatography on si-
lica gel (ethyl acetate / methanol ¼10:1) yielded the pure product
as a yellow solid (4.2 g, 53%). 1HNMR (DMSO-d, 500 MHz, 25 °C):
8.60 (s, 8H), 7.80 (d, 8H), 7.68 (s, 12H), 7.19 (d, 12H). 13CNMR
The measurements were made on a Bruker Apex Smart CCD
diffractometer with graphite-monochromated Mo-Ka radiation
(λ¼0.71073 Å). The structure was solved by direct methods, and
the non-hydrogen atoms were located from the trial structure and
then refined anisotropically with SHELXTL using full-matrix least-
squares procedures based on F2 values [22]. The distributions of
peaks in the channels of 1 and TPPBDA were chemically feature-
less to refine using conventional discrete-atom models. To resolve
these issues, the contribution of the electron density by the re-
maining water molecule was removed by the SQUEEZE routine in
PLATON [23]. Hydrogen atoms positions were fixed geometrically
at calculated distances and allowed to ride on the parent atoms. A
semiempirical absorption correction was applied using SADABS
[24]. The topological analysis and some diagrams were produced
using the TOPOS 4.0 program [25]. Crystallographic data and
structural refinements for the TPPBDA ligand and two compounds
were summarized in Table 1 and important bond distances are
listed in Table S1. The CCDC reference numbers are 1410720 and
1444480 for 1 and 2. The data can be obtained free of charge via
ohttp://www.ccdc.cam.ac.uk/conts/retrieving.html4, or from
the Cambridge Crystallographic Data Center, 12 Union Road,
Cambridge CB2 1EZ, UK; fax:(þ44) 1223–336–033; or e-mail:
deposit@ccdc.cam.ac.uk.
3. Results and discussion
3.1. Structure of {[Zn2(TPPBDA)(oba)2] ꢀ DMF ꢀ 1.5H2O}n (1)
Compound 1 crystallizes in the monoclinic crystal system C2/c
space group with two Zn cations, one TPPBDA, two oba2-and
squeezed solvent in the asymmetric unit (Fig. 1a). The solvent of
compound 1, that is one DMF and one and half of lattice water
molecules in per asymmetric unit, has been determined by ele-
mental analysis and thermogravimetric analysis. Each Zn(II) unit
Table 1
(DMSO-d): , [ppm]: 119.42, 120.41, 121.04, 124.33, 125.63, 128.15,
δ
Crystal data and structure refinements parameters of TPPBDA, complexes 1–2.
128.53, 131.85, 135.50, 145.91, 146.65, 148.12, 150.67. MS (ESI-Tof):
Calcd for C56H40N6, 796; found, 797.
Complex
1a
2
TPPBDAa
Formula
Mr
Cryst syst
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C84H56N6O10Zn2 C51H39N4O5Zn C56H40N6
2.2. Syntheses of compounds 1–2
1440.09
Monoclinic
C2/c
853.23
Monoclinic
P21/c
796.94
Monoclinic
P21/c
General procedure for the preparation of {[Zn2(TPPBDA)(oba)2]ꢀ
DMF ꢀ 1.5H2O}n (1): A mixture of H2O/DMF/CH3CN containing the
TPPBDA (79.6 mg, 0.1 mmol), 4,4′-H2oba (25.8 mg, 0.1 mmol) and
Zn(NO3)2 ꢀ 6H2O (29.7 mg, 0.1 mmol) was mixed in a Teflon vessel
within the autoclave. The vessel was heated at 85 °C for 72 h and
then cooled to room temperature. Transparent pale yellow block
crystals were collected (yield based on TPPBDA ligand: ꢂ20% for 1).
Elemental analysis calcd. for C84H56N6O10Zn2(C3H7NOH3O1.5)(1): C,
67.84; H, 4.32; N, 6.37, Found: C, 67.80; H, 4.29; N, 6.35. The IR
spectra of the corresponding complex was shown in the Supporting
Information (Fig. S1).
21.2969(18)
37.398(3)
28.267(2)
90.00
8.9575(8)
19.6850(18)
25.063(2)
90.00
16.293(2)
16.709(2)
17.586(2)
90.00
109.7320(10)
90.00
96.015(2)
90.00
92.956(2)
90.00
γ (°)
V (Å3)
Z
21192(3)
8
4395.0(7)
4
4781.2(10)
4
ρcaled (g cmꢁ3
)
0.903
0.611
1.107
μ (mmꢁ1
)
0.497
0.498
0.066
rflns collected
Uniq. rflns
64171
31908
35187
11061
5316
4182
Synthesis of {[Zn(TPPBDA)1/2(tpdc)] ꢀ DMF}n (2): Compound 2
was synthesized by dissolving 0.05 mmol of TPPBDA and 0.1 mmol
of H2tpdc in DMF (3 mL) in a 10 mL glass vial. A solution of 2 mL
0.1 mmol aqueous Zn(NO3)2 solution was then added and the so-
lution heated at 85 °C for 3 days. Transparent pale yellow pris-
matic crystals were formed. Yield of the reaction was ca. 40% based
on TPPBDA ligand. Elemental analysis calcd. for C51H39N4O5Zn (1):
C, 71.79; H, 4.61; N, 6.57, Found: C, 71.80; H, 4.68; N, 6.55. The IR
spectra of the corresponding complex was shown in the Sup-
porting Information (Fig. S2).
R(int)
0.0193
1.002
0.0500
0.1329
ꢁ0.376, 0.406
0.0722
1.066
0.0741
0.2112
0.0731
1.030
0.0669
0.1603
GOF(F2)
R1[I42s(I)]b
wR2[I42s(I)]c
Min. and max resd dens
ꢁ0.740, 0.826 ꢁ0.286, 0.269
(e Åꢁ3
)
a
The residual electron densities were flattened by using the SQUEEZE option of
PLATON.
b
c
R1¼Σ||Fo|-|Fc||/|Σ|Fo|.
wR2¼{Σ[w(Fo2-Fc2)2]/Σ[w(Fo2)2]}1/2; where w¼1/[s2(Fo2)þ(aP)2þbP], P¼(Fo
2
þ2Fc2)/3.

L. Qin et al. / Journal of Solid State Chemistry 239 (2016) 53–57
55
Fig. 1. (a) Coordination environments of complex 1 (30% ellipsoid probability). Most hydrogen atoms and solvent molecules are omitted for clarity. Symmetry codes for 1:
#1¼ ꢁ0.5þx, 0.5ꢁy, 0.5þz; #2¼1.5-x, ꢁ0.5þy, 0.5ꢁz. (b) View of 3D structure with meso-helical chains (marked by L and R) in net 1. (c) Schematic view of two
interpenetrating framework. (d) Schematic view of the topology of structure 1 (oba2ꢁ ligands were simplified into linkers).
has a seven coordination geometry. The carboxylate groups of
oba2ꢁ ligand takes bidentate-chelating and chelating-bridging
tridentate coordination modes, respectively. Two Zn(II) ions are
bridged by carboxylate oxygen atoms to form a four-membered
[Zn2(CO2)4] ring. The oba2ꢁ anions and TPPBDA ligands connect to
the [Zn2(CO2)4] units to generate a 3D net.
The three-dimensional net 1 consisted of meso-helical chains
(right handed helixes and left handed helixes), which are labeled as
R and L chains with an approximate dimension of 9.30 Å ꢃ 16.87 Å
(Fig. 1b). The oba2ꢁ and TPPBDA bridge [Zn2(CO2)4] units into a 21
helix with a helical pitch of 21.30 Å. However, left-handed and
right-handed helical chains coexist in the crystal structure, the
whole crystal is racemic and exhibit no chirality.
The overall structure is that two equivalent nets adopt 2-fold
interpenetration to minimize the large voids in the single net to
form a doubly interpenetrated framework (Fig. 1c). To better un-
derstand the structure, topological approach can be taken. In this
structure, TPPBDA ligands linking four [Zn2(CO2)4] clusters can act
as 4-connected nodes; [Zn2(CO2)4] clusters can be seen as 6-con-
nected nodes. On the basis of the simplification principle, the fi-
four oxygen atoms belonging to two oba ligands and two nitrogen
atoms from TPPBDA ligands with the Zn-O distances ranging from
2.062(7) Å to 2.359(8) Å and the Zn-N distances ranging from
2.067(3) Å and 2.108(4) Å. The tetradentate TPPBDA ligands and
tpdc2ꢁ anions bridge the Zn (II) ions into a 3D network containing
1D meso-helical chains with a helical pitch of 19.69 Å along the b-
axis, which are presented by L and R with an approximate di-
mension of 12.75 Å ꢃ 16.09 Å (Fig. 2b). The whole crystal is also
racemic and does not exhibit chirality. Considering the Zn(II) ca-
tions and the TPPBDA ligands as 4-c nodes, 2 can be defined as a
4-connected net with bbf topology as shown in Fig. 2c. In order to
minimize the presence of large cavities and to stabilize the fra-
mework during the assembly process, other four identical net-
works are filled in the cavities giving a 5-fold interpenetrating 3D
architecture (class Ia) (Fig. 2d).
3.3. The comparison of the configuration for TPPBDA ligand in dif-
ferent compounds
The distortion of TPPBDA can be assessed by comparing the
dihedral angles defined by the central benzene groups (A and B)
and the torsion angle of Npyridyl-Ncore-Npyridyl (1 and 2). In
TPPBDA, central benzene groups are almost in parallel. The angles
of 1 and 2 are 120.564(42)° and 116.686(60)° (Fig. 3). In compound
1, the ligand TPPBDA adopts a distorted conformation, and the
dihedral angle between A and B is 15.262(99)°. The angles of 1 and
2 are 118.532(34)° and 124.605(34)°. In compound 2, the dihedral
angle between A and B is almost zero. The angles of 1 and 2 are
both 114.978(52)°.
nally structure is
a (4,6)-connected net with point symbol
{46}{420.680.85} (Fig. 1(d)).
3.2. Structure of {[Zn(TPPBDA)1/2(tpdc)] ꢀ DMF}n (2)
X-ray crystallography reveal the asymmetric unit of 2 contains
one Zn(II) cation, half a TPPBDA ligand, one tpdc2ꢁ anion, and one
lattice DMF molecule (Fig. 2a). The Zn center is six coordinated by

56
L. Qin et al. / Journal of Solid State Chemistry 239 (2016) 53–57
Fig. 2. (a) Coordination environments of complex 2 (30% ellipsoid probability). Most hydrogen atoms and solvent molecules are omitted for clarity. Symmetry codes for 2:
#1¼1ꢁx, 0.5þy, 1.5-z; #2¼ ꢁx, 0.5þy, 2.5ꢁz. (b) View of 3D structure with meso-helical chains (marked by L and R) in net 2. (c) Schematic view of bbf topology of
structure 2 (tpdc2-ligands were simplified into linkers). (d) Schematic view of five interpenetrating bbf framework.
3.4. Optical properties
The photoluminescent properties of d10 metal coordination
compounds have been attracting more interest for their potential
applications as fluorescence-emitting materials. Therefore, in this
work, the solid-state emission spectra for complexes 1 and 2 were
studied in the solid state at room temperature (Fig. 4 and S3). The
emission spectra have peaks for 1 and 2 with maxima at 541 nm,
575 nm, respectively. In order to understand the nature of above
emission bands, the luminescence property of the TPPBDA ligand in
the solid state has also been measured (λem¼555 nm). Compared to
these emission peaks of TPPBDA ligand, the emissions of 1 and 2
may be attributed to intraligand transition. The differences in the
band positions of these two coordination polymers might be related
to the differences in the coordination environments or the degree of
interpenetration in these structures [26]. In addition, the emission
spectra of TPPBDA in crystalline state and in organic solvent are
Fig. 3. The structure of TPPBDA ligand (the solvent molecules are squeezed).
investigated (Figs. 5 and S4,S5). The results show that the emission

L. Qin et al. / Journal of Solid State Chemistry 239 (2016) 53–57
57
polymers 1–2 were almost consistent with their simulated spectra
(Figs. S7,S8).
4. Conclusions
We have synthesized two new zinc coordination polymers
{[Zn2(TPPBDA)(oba)2] ꢀ DMF ꢀ 1.5H2O}n (1), {[Zn(TPPBDA)1/2(tpdc)]
ꢀ DMF}n (2) based on a nanosized neutral ligand and two carbox-
ylate co-ligands. They are three-dimensional nets consisted of
meso-helical chains, that is, right handed helixes and left handed
helixes. Compound 1 is a 2-fold interpenetrated 3D framework
with dinuclear clusters. Compound 2 can be defined as a five fold-
interpenetrating bbf topology with mononuclear cation. These
mononuclear or dinuclear cluster units are interconnected by
TPPBDA and carboxylate co-ligands, resulting in interesting
structural diversity and various degrees of interpenetration.
Fig. 4. Solid-state photoluminescent spectra of compounds 1, 2 and TPPBDA ligand
at room temperature.
Acknowledgements
This work was supported by grants from Startup Foundation of
Hefei University of Technology (JZ2014HGBZ0358, XC2015JZBZ04)
and Open fund by Jiangsu Engineering Technology Research Cen-
ter of Environmental Cleaning Materials (KFK1505), A Project
Funded by the Priority Academic Program Development of Jiangsu
Higher Education Institutions (PAPD).
Appendix A. Supporting information
Supplementary data associated with this article can be found in
the online version at http://dx.doi.org/10.1016/j.jssc.2016.04.021.
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