Self-assembly, structures and properties of three new Ni(II) coordination polymers derived from two different bis-pyridyl-bis-amide ligands and two aromatic polycarboxylates

Article abstract of DOI:10.1007/s12039-016-1213-y

Three new Ni(II) coordination polymers exhibiting different 1D and 2D framework structures have been hydrothermally synthesized: [Ni(L ¹)(1,3-BDC)(H ₂O) ₃] ?H₂O (1), [Ni(L ¹)(1,3,5-HBTC)(H ₂O) ₃] (2), [Ni ₃(L ²)₃(1,3,5-BTC) ₂(H ₂O) ₈] ?12H ₂O (3) [L ¹= N,N ^′-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide, L ²= N,N ^′-bis(3-pyridyl)octandiamide, 1,3-H ₂BDC = 1,3-benzenedicarboxylic acid, 1,3,5-H ₃BTC = 1,3,5-benzenetricarboxylic acid]. X-ray single crystal diffraction analyses revealed that polymer 1 is a 2D interlaced layer based on the 1D [Ni(L ¹)(1,3-BDC)(H ₂O) ₃] meso-helical chains. Polymer 2 is a 1D wave-shaped chain derived from the 1D [Ni(L ¹)] _n chain and monodentate coordinated 1,3,5-HBTC anions. Polymer 3 possesses an interesting 2D layer containing the trinuclear [Ni ₃(1,3,5-BTC) ₂] substructural unit and 1D zigzag [Ni(L ²)] _n chain, representing a 3,4-connected {6 ?8 ²} ₂ {6²?8²?10?12} topology. Finally, the adjacent 1D chains or the 2D layers are connected through hydrogen bonding interactions to construct 3D supramolecular networks. Further, the thermal stability, solid state fluorescent property and photocatalytic activity of 1–3 have been investigated. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s12039-016-1213-y

J. Chem. Sci. Vol. 129, No. 1, January 2017, pp. 9–20. ꢀc Indian Academy of Sciences.
DOI 10.1007/s12039-016-1213-y
REGULAR ARTICLE
Self-assembly, structures and properties of three new Ni(II) coordination
polymers derived from two different bis-pyridyl-bis-amide
ligands and two aromatic polycarboxylates
∗
∗
HONGYAN LIN , JUNJUN SUN, GUOCHENG LIU , XIANG WANG and PANWEN CHEN
Department of Chemistry, Bohai University, Jinzhou 121000, People’s Republic of China
Email: linhongyan_2005@126.com; lgch1004@sina.com
MS received 14 July 2016; revised 24 September 2016; accepted 21 November 2016
Abstract. Three new Ni(II) coordination polymers exhibiting different 1D and 2D framework structures
1
1
have been hydrothermally synthesized: [Ni(L )(1,3-BDC)(H2O)3]·H2O (1), [Ni(L )(1,3,5-HBTC)(H2O)3]
2
1
ꢁ
(
2), [Ni3(L )3(1,3,5-BTC)2(H2O)8]·12H2O (3) [L = N,N -bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide,
2
ꢁ
L = N,N -bis(3-pyridyl)octandiamide, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, 1,3,5-H3BTC = 1,3,5-
benzenetricarboxylic acid]. X-ray single crystal diffraction analyses revealed that polymer 1 is a 2D interlaced
1
layer based on the 1D [Ni(L )(1,3-BDC)(H O) ] meso-helical chains. Polymer 2 is a 1D wave-shaped chain
2
3
1
derived from the 1D [Ni(L )]n chain and monodentate coordinated 1,3,5-HBTC anions. Polymer 3 possesses
an interesting 2D layer containing the trinuclear [Ni3(1,3,5-BTC)2] substructural unit and 1D zigzag [Ni(L )]n
chain, representing a 3,4-connected {6·8 }2 {6 ·8 ·10·12} topology. Finally, the adjacent 1D chains or the 2D
layers are connected through hydrogen bonding interactions to construct 3D supramolecular networks. Further,
the thermal stability, solid state fluorescent property and photocatalytic activity of 1–3 have been investigated.
2
2
2
2
Keywords. Metal-organic coordination polymer; crystal structure; bis-pyridyl-bis-amide ligand; fluorescence;
photocatalysis
1
. Introduction
example, Wen et al. have prepared four Cd(II)/Cu(II)
coordination polymers derived from a multidentate tri-
ꢁ
Metal-organic coordination polymers (MOCPs) rep-
resent an interesting new research field and attracted
significant attention in recent years.1 4 Up to now, a
great number of MOCPs possessing diverse structures
azole ligand and two different dicarboxylates [Cd(3,3 -
ꢁ
tmbpt)(1,4-BDC)]·2.5H O, [Cd(3,3 -tmbpt)(1,3-BDC)]·
2
ꢁ
ꢁ
2
1-H O, [Cu(3,3 -tmbpt)(1,3-BDC)]·H O and [Cu(3,3 -
2
2
ꢁ
tmbpt)(1,3-BDC)]·2H O (3,3 -tmbpt = 1-((1H-1,2,4-tria-
2
(such as 1D infinite chains, 2D layers and 3D net-
zol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole, 1,4-H2
works) have been proven to be potential functional
materials for luminescence, catalysis, gas storage and
separation, magnetism, ion exchange and so on.
1
1
,3-BDC = 1,4-benzenedicarboxylic acid, 1,3-H BDC =
2
24
,3-benzenedicarboxylic acid).
5
8
More recently, the bis-pyridyl-bis-amide ligands have
During the process of self-assembly of metal ions
and organic bridging ligands, many influencing fac-
tors may play important roles and even change the
final structures of the aimed MOCPs, such as the
geometric requirement of the metal ions, the geo-
metrical configuration of the organic ligands, the
system pH, the category of solvent and the reaction
been introduced into metal-carboxylate systems and
a number of MOCPs with interesting properties have
been generated, due to their several advantages: (a) As
neutral nitrogen-/oxygen-donor ligands, both the pyri-
dine moieties and the amide groups of these ligands
can coordinate with metal ions; (b) The conformational
changes of these ligands can meet the requirements
of the coordination geometries of metal ions, which
is conducive to construct new complexes more eas-
ily; (c) The amide groups could function not only
as hydrogen bonding acceptors but also as hydrogen
bonding donors, which may generate high-dimensional
supramolecular networks. For example, Chen et al.,
have reported a series of Zn(II)/Cd(II) coordination
polymers derived from the flexible bis-pyridyl-bis-
amide and aromatic polycarboxylates mixed ligands,
9
13
temperature.
So, significant interest has arisen in the
structural tuning of MOCPs by rational design and
selection of organic bridging ligands, usually includ-
14 18
ing O-donor and N-donor ligands.
Wherein, the
mixed-ligand systems consisting of N-donor hete-
rocyclic ligands and O-donor carboxylate ligands
have been widely used to obtain MOCPs.1
9 23
For
∗
For correspondence
9

10
Hongyan Lin et al.
all of them exhibiting fluorescence property.25 28 Our
group has also made some efforts in constructing the
Cu(II)/Co(II)/Cd(II) coordination polymers containing
the flexible/rigid bis-pyridyl-bis-amide ligands and
for polymer 1. Suitable crystals were manually picked,
washed with water and dried in air. Yield: ∼42% (based on
Ni). Anal. Calcd. for C26H32NiN4O10 (619.27): C 50.38, H
5
.21, N 9.04%. Found: C 50.45, H 5.13, N 9.17%. IR (KBr
−1
pellet, cm ): 3460 (s), 3205 (m), 3008 (w), 2365 (w), 2338
(w), 2092 (w), 1689 (s), 1600 (s), 1527 (s), 1481 (s), 1434 (s),
polycarboxylates, and studied their electrochemical,
photocatalytic or fluorescence properties.2
9 32
However,
1
8
381 (s), 1321 (m), 1281 (m), 1201 (w), 1115 (w), 989 (w),
76 (m), 810 (s), 748 (m), 715 (s), 635(w), 556 (m), 523 (w).
the related Ni(II) coordination polymers constructed by
the flexible/rigid bis-pyridyl-bis-amide ligands and aro-
2
9,33
matic polycarboxylates are still limited, up to now.
1
2
.2b Synthesis of [Ni(L )(1,3,5-HBTC)(H2O) ] (2):
3
1
ꢁ
2
Therefore, two bis-pyridyl-bis-amide ligands [L , N,N -
bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide; L ,
N,N -bis(3-pyridyl)octandiamide] have been selected
Polymer 2 was synthesized in the same way as 1, except
that 1,3,5-H3BTC (0.032 g, 0.15 mmol) was used instead of
ꢁ
1,3-H2BDC (0.025 g, 0.15 mmol). Green block-shaped crys-
as the main ligands and combined with two polycar- tals suitable for X-ray single diffraction of 2 were isolated
boxylates [1,3-H BDC, 1,3,5-H BTC (1,3,5-benzene- (yield: 36% based on Ni). Anal. Calcd. for C H N NiO
2
3
27 30
4
11
tricarboxylic acid)] to construct Ni(II) coordination (645.26): C 50.21, H 4.69, N 8.68%. Found: C 50.14, H
−1
polymers, aiming to study their effect on the final 4.75, N 8.56%. IR (KBr pellet, cm ): 3437 (s), 3248 (m),
3
1
1
111 (w), 2361 (w), 1721 (m), 1617 (s), 1565 (s), 1519 (m),
473 (w), 1428 (s), 1388 (m), 1362 (s), 1264 (w), 1219 (m),
153 (s), 1101 (s), 990 (w), 932 (w), 873 (w), 808 (m), 729
architectures and potential properties of target MOCPs.
In this paper, we report three new Ni(II) MOCPs based
on the mixed-ligands of two different bis-pyridyl-bis-
1
2
(s), 690 (w), 664 (m), 612 (m), 592 (w), 540 (w), 508 (w).
amide (L , L ) and two aromatic polycarboxylates
1
(
1,3-H BDC, 1,3,5-H BTC), namely, [Ni(L )(1,3-
2 3
2
2
.2c Synthesis of [Ni3(L )3(1,3,5-BTC)2(H2O)8]·12H2O
1
BDC)(H O) ]·H O (1), [Ni(L )(1,3,5-HBTC)(H O) ]
2
3
2
2
3
(3): The method for polymer 3 was the same as for 2, except
2
(
2) and [Ni (L ) (1,3,5-BTC) (H O) ]·12H O (3).
3
3
2
2
8
2
2
1
that L (0.033 g, 0.10 mmol) was used instead of L (0.033
g, 0.10 mmol). Green crystals of 3, suitable for single X-ray
diffraction were obtained by mechanical separation from the
amorphous solid in 35% yield (based on Ni). Anal. Calcd.
for C72H112Ni3N12O38 (1929.87): C 44.77, H 5.85, N 8.71%.
Polymer 1 represents the first 2D interlaced layer based
1
on the 1D [Ni(L )] meso-helical chains constructed
n
from the bis-pyridyl-bis-amide ligand.
−1
Found: C 44.69, H 5.73, N 8.88%. IR (KBr pellet, cm ):
420 (s), 3126 (m), 2932 (w), 2355 (w), 2079 (w), 1679 (w),
1615 (s), 1533 (s), 1484 (s), 1434 (s), 1378 (s), 1253 (w),
190 (s), 1158 (m), 1108 (m), 933 (m), 807 (m), 764 (m),
2. Experimental
3
2.1 Materials and methods
1
1
2
The main ligands L and L were synthesized by the lit- 701 (s), 645 (w), 613 (w), 526 (w).
34,35
erature method.
,3,5-H3BTC were commercially obtained from Aladdin
Reagent Co. (China) and used without further purification.
The ancillary ligand 1,3-H2BDC and
1
2
.3 X-ray crystallography
All other reagents and solvents for syntheses were pur- X-ray diffraction data for polymers 1–3 were collected on
chased from commercial sources and were used without a Bruker Smart Apex-II CCD area detector and graphite-
further purification. FT-IR spectrum (in KBr pellet) was per- monochromated Mo Kα (λ = 0.71073 Å) by ω and θ
formed on a Varian FT-IR 640 spectrometer. Thermogravi- scan mode. All the structures were solved by direct meth-
2
metric (TG) data of three title polymers were taken on a
Pyris-Diamond thermal analyzer under nitrogen atmosphere.
Powder X-ray diffraction (PXRD) investigation was recorded
on a Bruker AXS D8-Advanced diffractometer. The fluores-
cence spectra were carried out using a HITACHI F–4500
Fluorescence Spectrophotometer. UV-Vis absorption spectra
were taken on a SP-1900 spectrophotometer.
ods and refined on F by full-matrix least-squares methods
using the SHELXS program of the SHELXTL package. For
polymers 1–3, the crystal parameters, data collection, and
refinement results are summarized in Table 1. Selected bond
distances and bond angles are listed in Table S1–S3 (Sup-
plementary Information). Hydrogen bonding geometries of
polymers 1–3 are summarized in Table S4 (Supplementary
Information).
2.2 Preparation of the polymers
1
2
.2a Synthesis of [Ni(L )(1,3-BDC)(H2O)3]·H2O (1):
A
3. Results and Discussion
mixture of Ni(NO3)2·6H2O (0.058 g, 0.2 mmol), 1,3-H2BDC
1
3
.1 Description of crystal structure
(
0.025 g, 0.15 mmol), L (0.033 g, 0.10 mmol), H2O (12 mL)
1
and NaOH (0.018 g, 0.45 mmol) was stirred for 30 min, then of [Ni(L )(1.3-BDC)(H
transferred and sealed in a 25 mL Teflon reactor, which was
heated at 120 C and kept for 4 days; then cooled to room Single-crystal X-ray diffraction analysis reveals that
O)
]·H
O (1)
2
3
2
◦
temperature leading to the formation of green block crystals polymer 1 is monoclinic crystal system with C 2/c

Three new nickel(II) coordination polymers
11
Table 1. Crystal data and structure refinement for polymers 1–3.
Formula
C26H32NiN4O10
C27H30N4NiO11
C72H112Ni3N12O38
Formula wt.
Cryst. size, mm3
Crystal system
Space group
T , k
619.27
645.26
1929.87
0.23 × 0.21 × 0.16
Monoclinic
C 2/c
0.22 × 0.18 × 0.14
Monoclinic
P 21/c
0.23 × 0.21 × 0.20
Triclinic
P -1
293(2)
296(2)
296(2)
a, Å
b, Å
c, Å
α, deg
β, deg
γ , deg
V , Å3
25.893(5)
16.974(5)
13.924(5)
90
110.486(5)
90
5733(3)
8
1.430
14.700(3)
12.017(2)
16.197(3)
90
99.359(4)
90
2822.9(9)
4
1.518
9.2271(5)
11.7044(7)
22.0100(14)
83.4150(10)
83.3690(10)
70.9440(10)
2224.2(2)
1
Z
3
Dcalc, g/cm
μ, mm
1.441
0.723
−1
0.738
0.756
2576
1344
1016
F(000)
1.430
1.518
1.441
hkl range
−32 ≤ h ≤ +21
−18 ≤ h ≤ +19
−15 ≤ k ≤ +15
−15 ≤ l ≤ +21
27.95
−9 ≤ h ≤ +11
−13 ≤ k ≤ +15
−28 ≤ l ≤ +24
27.47
−
19 ≤ k ≤ +21
12 ≤ l ≤ +17
−
θmax, deg
26.19
Rint
0.0265
0.0398
0.1056
1.033
0.679
−0.243
0.0528
0.0943
0.2987
1.058
2.005
−0.859
0.0194
0.0511
0.1475
1.019
0.769
−0.643
a
R
1
b
2
wR (all data)
GOF
−
3
ꢀρmax, e Å
−3
ꢀρmin, e Å
a
b
2
o
2 2
c
2 2 1/2
o
R1 = ꢁ||Fo| − | Fc||ꢁ| Fo|; wR2 = ꢁ[w(F –F ) ]/ꢁ[w(F ) ]
.
1
space group, which shows a 2D interlaced layer derived adjacent Ni(II) ions to construct a 1D [Ni(L )] meso-
1
from a 1D polymeric chain [Ni(L )(1,3-BDC)(H O) ] . helical chain with alternate iteration of left-handed and
2
3 n
The asymmetric unit of 1 contains one Ni(II) ion, right-handed half turns (Figure 1b, 1c and Figure S1a in
1
an L ligand, one 1,3-BDC anion, three coordinated Supplementary Information), in which only one car-
water molecules and one lattice water molecule. Each boxyl group of the 1,3-BDC anion adopts a monoden-
Ni(II) ion is six-coordinated by two pyridyl nitro- tate coordination mode hanging on the side of the
gen atoms [Ni(1)–N(1) = 2.133(2) Å, Ni(1)–N(3)#1 1D chain. In the 1D chain, the different non-bonding
1
1a
1b
=
2.145(2) Å] from two separate L ligands, one car- Ni· · · Ni distances are 18.23 Å (L ) and 18.16 Å (L ).
boxyl oxygen atom O(6) of a 1,3-BDC anion with
distance of 2.0430(18) Å, and three oxygen atoms are in mutually staggered arrangement to form the
O(1W), O(2W) and O(3W)] belonging to three coor- interlaced layer (Figure 1d, 1e and Figure S1b in
dinated water molecules [Ni(1)–O distances: 2.042(2)– Supplementary Information). Further, there exist
Interestingly, the adjacent 1D meso-helical chains
[
2
.085(2) Å] to complete a distorted octahedral geom- strong O–H· · · O hydrogen bonding interactions
1
etry (Figure 1a). In complex 1, the L ligands adopt [O(1W)–H(1WA)· · · O(1)
=
2.764(3) Å O(2W)–
only one μ -bridging coordination mode (via ligation H(2WA)· · · O(2) = 2.689(4) Å, Table S4 in Supple-
2
of pyridyl nitrogen atoms), but they exhibit two kinds mentary Information] among the adjacent chains in
1a
1b
of conformations (L and L , Table 2) due to the flex- the interlaced layer to consolidate the 2D framework
ibility of the cyclohexyl group. For each kind of the L
1
(Figure S1c in Supplementary Information). To the best
ligands, their two pyridine rings are parallel. The of our knowledge, the polymer 1 represents the first 2D
1a
1b
1
ligands L and L alternately are connected to the interlaced layer based on the 1D [Ni(L )] meso-helical
n

12
Hongyan Lin et al.
3
D supramolecular network by the O–H· · · O hydro-
gen bonding interactions [O(1W)–H(1WA)· · · O(4) =
2
.694(3) Å, O(2W)–H(2WA)· · · O(3) = 2.676(3) Å], as
shown in Figure 1f.
3
.2 Description of crystal structure
1
of [Ni(L )(1,3,5-HBTC)(H O) ] (2)
2
3
Similar to polymer 1, using 1,3,5-H BTC in the reac-
3
tion, polymer 2 was successfully prepared. It crystal-
lizes in monoclinic crystal system with P21/c space
group. The asymmetric unit of 2 consists of one Ni(II)
1
ion, one L molecule, one 1,3,5-HBTC anion and three
coordinated water molecules. As shown in Figure 2a,
Ni(II) ion displays a six-coordinated distorted octa-
hedral geometry, coordinated by one carboxyl oxy-
gen atom from 1,3,5-HBTC anion with Ni(1)–O(1)
distance of 2.039(5) Å, two pyridyl nitrogen atoms
1
from two L ligands [Ni(1)–N(1) = 2.119(6) Å, Ni(1)–
N(2)#1 = 2.148(6) Å], and three oxygen atoms of
three coordinated water molecules [Ni(1)–O(1W) =
2
.062(5) Å, Ni(1)–O(2W) = 2.076(5) Å, Ni(1)–O(3W)
=
2.033(5) Å]. In polymer 2, the adjacent Ni(II) ions
1
are linked by L ligands with a μ -bridging mode to
2
1
form a 1D [Ni(L )] wave-like chain (Figure 2b), in
which the 1,3,5-HBTC anions only adopt a monoden-
tate mode and hang on both sides of the 1D chain.
1
In 2, the L exhibits only one coordination confor-
mation, which bridges two Ni(II) ions with the non-
bonding Ni· · · Ni distance as 18.08 Å, and the dihe-
◦
dral angle between its two pyridine rings is 7.39
(
Table 2). Furthermore, the 1D chains are connected by
the O–H· · · O hydrogen bonding interactions between
the coordinated water molecules and the carbonyl group
1
of L ligands [O(1W)–H(1WA)· · · O(7), 3.008(10) Å;
O(2W)–H(2WB)· · · O(8), 2.757(8) Å] to give a 2D
supramolecular structure, as shown in Figure S2a
(
Supplementary Information). The π-π stacking in-
1
teractions between the pyridyl rings among the L
ligands consolidate the 2D supramolecular architec-
ture of 2 [the shortest centroid–centroid distance is
3
.678(5) Å]. Finally, the other O–H· · · O hydrogen
Figure 1. (a) The coordination environment of Ni(II) ion in
polymer 1. (b) The 1D [Ni(L )(BDC)(H2O)3] meso-helical
1
bonding interactions [O(1W)–H(1WA)· · · O(5) = 3.228
chain. (c) The simplified representation of 1D chain of 1. (d) (9) Å, O(3W)–H(3WA)· · · O(2) = 2.755(8) Å, O(1W)
The simplified representation of the interlaced arrangement –H(1WB)· · · O(4) = 2.718(8) Å, O(3W)–H(3WB)· · ·
of the adjacent 1D chains along the b-axis in 1. (e) View of
O(3) = 2.641(8) Å] between the coordinated water
the interlaced 2D framework of 1. (f) The 3D supramolecular
molecules and the carboxyl oxygen of 1,3,5-HBTC
network of 1 formed by hydrogen bonding interactions along
anions link the neighboring 2D layers to form a 3D su-
the c-axis.
pramolecular network (Figure 2c). The hydrogen bond-
chains derived from the bis-pyridyl-bis-amide ligand. ing data are summarized in Table S4 (Supplementary
Finally, the 2D interlaced layers are extended into a Information).

Three new nickel(II) coordination polymers
13
1
2
Table 2. Coordination modes of Ni(II) ions, the bis-pyridyl-bis-amide ligands (L , L ) and polycarboxylates (1,3-BDC,
1,3,5-HBTC, 1,3,5-BTC) in polymers 1–3.
Ni(II)
ion(s)
Dihedral angle of
pyridyl rings
Polymers
Polycarboxylates
Bis-pyridyl-bis-amide ligands
◦
1
0
◦
0
◦
2
7.39
◦
35.60
3
◦
0
2
3
.3 Description of crystal structure of [Ni (L )
independent Ni(II) ions in 3. The Ni1 ion is six-
coordinated by two carboxyl oxygen atoms from two
different 1,3,5-BTC anions [Ni(1)–O(1), Ni(1)–O(1)#1,
3
3
(1,3,5-BTC) (H O) ]·12H O (3)
2
2
8
2
2
.0392(18) Å], two pyridyl nitrogen atoms from two
Polymer 3 was obtained by a similar procedure as that
of 2, except that L was used instead of L . X-ray
diffraction analysis displays that polymer 3 pos-
2
2
1
L molecules [Ni(1)–N(1), Ni(1)–N(1)#1, 2.140(2) Å]
and two coordinated water molecules [Ni(1)–O(1W),
sesses a 2D coordination framework in triclinic crys- Ni(1)–O(1W)#1, 1.979(2) Å], showing a distorted
tal system with P-1 space group. The asymmetric octahedral geometry. The Ni2 ion is also in six-
unit of 3 contains three Ni(II) ions, two 1,3,5-BTC coordinated distorted octahedral geometry, surrounded
2
anions, three L molecules, eight coordinated water by one carboxyl oxygen atom of a 1,3,5-BTC anion
molecules and twelve lattice water molecules. As [Ni(2)–O(3) = 2.0630(19) Å], two pyridyl nitrogen
2
shown in Figure 3a, there are two crystallographically atoms of two L molecules [Ni(2)–N(2) = 2.112(2) Å,

14
Hongyan Lin et al.
Figure 2. (a) The coordination environment of Ni(II) ion in polymer 2. (b)
The 1D polymeric chain of 2. (c) The 3D supramolecular structure of 2 formed
by hydrogen bonding interactions.
2a
2b
Ni(2)–N(5) = 2.111(2) Å] and three oxygen atoms two different coordination conformations (L and L ,
2a
2b
belonging to three coordinated water molecules [Ni(2)– Table 2). The ligands L and L alternately link the
2
O(2W) = 2.0552(19) Å, Ni(2)–O(3W) = 2.091(2) Å, adjacent Ni(II) ions to construct a 1D [Ni(L )] chain
Ni(2)–O(4W) = 2.052(2) Å]. Each 1,3,5-BTC anion (Figure S3b in Supplementary Information). Ni1 and
2a
adopts a monodentate-monodentate bridging mode Ni2 ions are bridged by the L ligand with the non-
(
Table 2) to connect with two Ni(II) ions with the non- bonding distance of 17.56 Å, while two Ni2 ions are
2b
bonding Ni1· · · Ni2 distance of 7.91 Å. Two Ni2 and linked through the L ligand [Ni2··Ni2 = 18.72 Å]. In
2
one Ni1 ions are bridged by two 1,3,5-BTC anions to the 2D of 3, each Ni1 is surrounded by two L ligands
build a trinuclear [Ni (1,3,5-BTC) ] substructural unit, and two 1,3,5-BTC anions, which can be regarded as a
3
2
as shown in Figure S3a (Supplementary Information). four-connected node; while Ni2 is linked by one 1,3,5-
2
Then, the trinuclear structural units are further con- BTC anion and two L ligands, which can be considered
2
nected by μ -bridging L ligands to generate a 2D as a three-connected node. The 1,3,5-BTC anion acts
2
polymeric layer (Figure 3b). Wherein, the ligands show as a two-connector to link two Ni(II) ions, then the L2

Three new nickel(II) coordination polymers
15
through the hydrogen bonding interactions between the
coordinated water molecules and the carboxyl oxygen
atoms of 1,3,5-BTC anions [O(2W)–H(2WB)· · · O(6)
=
2.711(3) Å, O(4W)–H(4WB)· · · O(5) = 2.746(3) Å],
giving a 3D supramolecular network (Figure 3d and
Figure S3d in Supplementary Information).
3.4 Powder X-ray diffraction of polymers 1–3
The powder X-ray diffraction (PXRD) patterns of the
as-synthesized crystal materials were almost identical
to that calculated from the single-crystal structures, as
shown in Figure S7–S9 (Supplementary Information).
The diffraction peaks of the simulated and experimen-
tal patterns match well in key positions, indicating the
phase purities of the as-synthesized polymers 1–3.
3.5 Thermal stability analyses of polymers 1–3
The thermogravimetric (TG) curves of polymers 1–3
were determined in the temperature range of 20–
◦
◦
−1
7
00 C with a heating rate of 10 C·min , as shown in
Figures S10–S12 (Supplementary Information). The TG
curve of polymer 1 displays two obvious weight loss
steps. The first weight loss step in the region of 155–
◦
2
55 C should be ascribed to the loss of lattice water and
coordinated water molecules (11.63%, calcd. 11.43%).
The second weight loss step in the range of 370–
◦
5
10 C is equivalent to the decomposition of organic
1
ligands (1,3-BDC and L ). The final remaining weight
12.36%) is close to 12.23% by assuming NiO phases
(
as the final residue (calcd 12.06%), indicating this is
the final product. For the TG curve of polymer 2, the
◦
first weight loss occurs about 160 C, which can be
assigned to the loss of coordinated water molecules
(8.86%, calcd. 8.37%). Then the framework of 2 began
to decompose with a continuous weight loss up to
◦
5
50 C, and the remaining weight 11.76% is in agree-
ment with the percentage of Ni and O components
calcd. 11.58%). For 3, its TG curve shows three weight
(
loss steps, the first step should be attributed to the loss
of lattice water molecules (10.56%, calcd. 11.19%), the
second step could be attributed to the loss of coordi-
nated water molecules (7.27%, calcd. 7.46%), and the
third step might be ascribed to the loss of organic lig-
Figure 3. (a) The coordination environment of Ni(II) ions
in polymer 3. (b) The 2D polymeric layer of 3. (c) The
schematic representation of the 2D layer in 3. (d) The 3D ands. And the remaining weight 12.20% is in consistent
supramolecular structure for 3 formed by hydrogen bonding with the Ni and O components in NiO (calcd. 11.61%),
interactions.
indicating that the final product is NiO.
ligand serves as a linker, thus the resulting 2D layer of 3
3
.6 Fluorescent property of polymers 1–3
is an interesting 2,3,4-connected framework with point
2
2
2
symbol of {6.8 } {6 .8 .10.12}{6} (Figure 3c). In addi- The fluorescent property of polymers 1–3, the free lig-
2
2
1
2
tion, such 2D polymeric layers are further connected ands L and L were studied at room temperature in the

16
Hongyan Lin et al.
1
Figure 4. (a) The emission spectra of polymers 1 and 2 and the free ligand L (λex = 280 nm). (b) The
2
emission spectrum of polymer 3 and the free ligand L (λex = 280 nm).
Figure 5. (a–c) Absorption spectra of the MB solution (10.0 mg·L 1) during the decomposition reac-
tion under UV irradiation in the presence of polymers 1–3. (d) Photocatalytic decomposition rates of MB
solution under UV irradiation with the use of polymer catalysts 1–3 and without catalyst under the same
conditions.
−

Three new nickel(II) coordination polymers
17
solid state (Figure 4). The solid-state 1,3-H BDC and be the potential candidates for photoactive materials
2
1
,3,5-H BTC ligands can exhibit fluorescence at room due to their high thermal stability and insolubility in
3
temperature, but its fluorescent emission resulting from common organic solvents.
the π*→n transition is very weak compared to that of
1
2
the π*→ π transition of the N-donor ligands L and L ;
3.7 Photocatalytic property of polymers 1–3
so, 1,3-H BDC and 1,3,5-H BTC ligands almost have
2
3
no contribution to the fluorescent emission of the title Recently, some metal-organic coordination polymers
3
6,37
polymers.
As shown in Figure 4a, the free ligand have been used as one kind of photocatalysts for decom-
1
40,41
L displays the emission peak at 348 nm for the excita- posing organic pollutants under UV irradiation.
tion at 280 nm. The polymers 1–2 and L ligands have Herein, we studied the photocatalytic activities of poly-
1
similar emission spectra, and their emission bands are mers 1–3 for the photodegradation of organic dye
observed at 363 nm for 1 and 360 nm for 2 (λex
80 nm). The red shift of 15 nm for 1 and 12 nm for 2 (RhB) under UV irradiation to evaluate the photocat-
were seen, which may be ascribed to metal-to-ligand or alytic effectiveness in the purification of waste water.
=
contaminants methylene blue (MB) and rhodamine B
2
38,39
ligand-to-metal charge-transfer transitions.
The free The photocatalytic performance of polymers 1–3 for
ligand L has the emission peak at 390 nm for the exci- the degradation of MB and RhB was studied by a typi-
2
tation at 280 nm, and polymer 3 exhibits the emission cal process: 90 mg of the title polymers as powder was
−1
band at 395 nm (Figure 4b). Three title polymers may dispersed in the MB or RhB solution (10.0 mg·L ),
Figure 6. (a–c) Absorption spectra of the RhB solution (10.0 mg·L 1) during the decomposition reaction
under UV irradiation with the presence of polymers 1–3. (d) Photocatalytic decomposition rates of RhB
solution under UV irradiation with the use of polymer catalysts 1–3 and without catalyst under the same
conditions.
−

18
Hongyan Lin et al.
and then magnetically stirred in the dark for 30 min spectra, PXRD and TG curves, Figures S1–S12) are available
to ensure equilibrium of the working solution. The dye in Supplementary Information; see, www.ias.ac.in/chemsci.
solution was then exposed to UV irradiation from a
1
3
25 W Hg lamp and kept continuously stirred. Every
0 min interval, 3.0 mL of MB or RhB solution sam-
Acknowledgements
ple was taken out for analysis. As shown in Figure 5, in
the presence of title polymers, the absorption peaks of
MB decreased with time under UV irradiation. In addi-
tion, the concentration of MB and RhB (C) versus reac-
tion time (t) are plotted in Figure 5d. It can be seen that
the photocatalytic activity increased from 14% (with-
out any catalyst) to 28% for 1, 47% for 2 and 62% for
This work was supported by the National Natural Science
Foundation of China (No. 21471021, 21501013, 21401010),
New Century Excellent Talents in University (NCET-09-
0853) and Program of Innovative Research Team in Univer-
sity of Liaoning Province (LT2012020).
3
after 180 min of UV irradiation. Similar experiments
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