A novel coordination polymer containing puckered rhombus grids

Article abstract of DOI:10.1039/b108449f

The polymeric complex [Ni(spcp)₂]_n (spcp^- = 4-sulfanylmethyl-4′-phenylcarboxylate pyridine) with puckered rhombus grids of dimensions 11.72 × 11.09 A was obtained from the reaction of Ni(OAc)₂·4H₂O wi

Full text of DOI:10.1039/b108449f

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A novel coordination polymer containing puckered rhombus grids
Yingjun Zhao, Maochun Hong,* Daofeng Sun and Rong Cao*
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the
Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China
Received 19th September 2001, Accepted 9th January 2002
First published as an Advance Article on the web 25th February 2002
The polymeric complex [Ni(spcp)2]n (spcpϪ = 4-sulfanylmethyl-4Ј-phenylcarboxylate pyridine) with puckered
rhombus grids of dimensions 11.72 × 11.09 Å was obtained from the reaction of Ni(OAc)2ؒ4H2O with Na(spcp) by
solvothermal methods.
Table 1 Crystal data for 1
Introduction
Owing to their fascinating properties and potential applications
in functional materials, the construction of organic–inorganic
open framework complexes with variable cavities or channels
has received considerable interest in the last decade.1,2 It has
been documented that the choice of ligand plays an important
role in the structure of the open framework complexes. For
instance, the bidentate nitrogen containing ligand 4,4Ј-bipyrid-
ine and its analogues have been widely employed and have
resulted in a great number of novel networks;3–6 polycarboxy-
late ligands have led to the formation of moderately robust
(“zeolitic”) frameworks7 and other porous coordination poly-
mers;8 and the use of mixed ligands has also produced many
novel polymeric structures.9–14 Although both length and flexi-
bility of the organic ligand have great influence on the struc-
tural topology, studies on the influence of flexibility attract less
attention. Recently we have begun work on the architectures of
polymeric structures containing flexible ligands and a series
of interesting structures has been obtained.15,16 As part of
our systematic work, in this paper we will report the synthesis
and characterization of a novel long and flexible mono-
anionic ligand with hybrid pyridyl and benzoic carboxylate
moieties, namely 4-sulfanylmethyl-4Ј-phenylcarboxylate pyrid-
ine (spcpϪ), and its nickel polymer [Ni(spcp)2]n (1) which pos-
sesses puckered rhombus grids of dimensions 11.72 × 11.09 Å.
Empirical formula
Formula weight
Space group
a/Å
b/Å
c/Å
α/Њ
β/Њ
C26H20N2NiO4S2
547.27
P1
¯
11.0854(3)
11.1224(3)
11.720(0)
63.373(1)
82.008(1)
80.142(1)
1269.56(5)
2
1.432
293(2)
0.963
6634
γ/Њ
V/Å3
Z
ρcal/g cmϪ3
T /K
µ/mmϪ1
Independent reflections
Observed reflections
R(Fo)
Rw(Fo)
4446
0.0714
0.1831
1.051
S
Largest difference peak, hole/e ÅϪ2
1.075, Ϫ0.489
Preparation of [Ni(spcp)2]n (1)
A mixture of Ni(OAc)2ؒ4H2O (0.249 g, 1 mmol) and Na(spcp)
(0.54 g, 2 mmol) in a metal-to-ligand ratio of 1 : 2 in 20 ml of
CH3OH/H2O (1 : 1) was sealed in a stainless-steel reactor with a
Teflon liner and heated at 90 ЊC for 72 h. A large quantity of
green, sheet-like crystals of 1 were obtained after the solution
was cooled to room temperature (0.41 g, 74%). Elemental
analyses: for C26H20N2NiO4S2, calc: C, 57.06; H, 3.68; N, 5.12.
Found: C, 57.07; H, 3.78; N, 5.08%. IR(KBr, cmϪ1): 1593(vs),
1541(vs), 1421(vs), 1394(vs), 1020(m), 737(s), 642(m), 503(w).
Experimental
Preparation of Na(spcp)
A mixture of the sodium salt of 4-sulfanylpyridine (0.65 g,
5 mmol) and the sodium salt of 4-(bromomethyl)phenyl-
carboxylate (2.15 g, 5 mmol) in CH3OH (40 ml) was heated to
60 ЊC for 12 h with vigorous stirring. After cooling, AgNO3
(5 mmol, 0.85 g) was added to the solution and stirred for half
an hour. The reaction mixture was filtered and the resultant
solution was dried to give an oil-like product, which was
washed three times with H2O (2 ml) and then extracted with
CH3OH (20 ml). Removing the CH3OH under vacuum gave rise
to crude Na(spcp). Pure Na(spcp) was obtained as a white
powder by recrystallization from CH2Cl2/Et2O/hexane (1 : 1 : 1)
(yield 0.68 g, 51%). Elemental analyses: for C13H10NNaO2S,
calc: C, 58.42; H, 3.77; N, 5.24. Found: C, 58.36; H, 3.68; N,
5.18%. NMR (CD3OD, 500 MHz): δ 4.36 (s, 2H, –CH2), 7.31
(d, J = 6.0 Hz, 2H, –C5H4N), 8.27 (d, J = 5.5 Hz, 2H, –C5H4–),
7.44 (d, J = 8.0 Hz, 2H, –C6H4–), 7.90 (d, J = 8.5 Hz, 2H,
–C6H4–). IR(KBr, cmϪ1): 1630(s), 1589(vs), 1545(s), 1385(vs),
1109(m), 1092(m), 1018(m), 798(s), 748(s), 634(m), 536(w),
492(s).
Crystallography
A single crystal of 1 with approximate dimensions 0.24 × 0.20 ×
0.13 mm was used for data collection. The intensity data
were collected on a Siemens Smart CCD diffractometer with
graphite-monochromated Mo-Kα radiation (λ = 0.71073Å) at
room temperature. Empirical absorption corrections were
applied by using the SADABS program for the Siemens area
detector.17 The structure of the complex was solved by direct
methods18 and all calculations were performed by using the
SHELXL-97 program19 on a Legend computer. The structure
was refined by full-matrix least-squares minimizations of Σ(Fo
Ϫ Fc)2 with anisotropic thermal parameters for all atoms except
H. The positions of the H atoms were generated geometrically,
assigned isotropic thermal parameters, and allowed to ride on
their parent carbon atoms before the final cycle of refinement.
Table 1 summarizes the important crystal data and Table 2 gives
the selected bond lengths and angles for the complex.
1354
J. Chem. Soc., Dalton Trans., 2002, 1354–1357
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b108449f

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Table 2 Bond lengths (Å) and angles (Њ) for 1
Ni–N(1)
Ni–O(3B)
Ni–N(2)
2.057(5)
2.057(4)
2.065(5)
Ni–O(1A)
Ni–O(2A)
Ni–O(4B)
2.078(4)
2.170(5)
2.179(5)
N(1)–Ni–O(3B)
N(1)–Ni–N(2)
95.58(19)
98.7(2)
94.0(2)
94.71(19)
165.37(18)
94.66(19)
92.2(2)
107.10(18)
155.2(2)
O(1A)–Ni–O(4B)
O(2A)–Ni–O(4B)
C(9)–S(1)–C(8)
C(29)–S(2)–C(28)
C(5)–C(8)–S(1)
C(13)–C(9)–S(1)
C(10)–C(9)–S(1)
C(25)–C(28)–S(2)
C(30)–C(29)–S(2)
C(33)–C(29)–S(2)
N(2)–Ni–O(4B)
105.98(17)
88.70(18)
104.4(3)
104.2(3)
116.6(5)
125.0(5)
117.0(5)
116.6(5)
117.7(5)
126.3(5)
89.8(2)
O(3B)–Ni–N(2)
N(1)–Ni–O(1A)
O(3B)–Ni–O(1A)
N(2)–Ni–O(1A)
N(1)–Ni–O(2A)
O(3B)–Ni–O(2A)
N(2)–Ni–O(2A)
O(1A)–Ni–O(2A)
N(1)–Ni–O(4B)
O(3B)–Ni–O(4B)
Scheme 1 Top: spcpϪ ligand; bottom: coordination mode of spcpϪ
in 1.
62.08(17)
156.96(19)
62.30(17)
the coordination sphere of the metal ion owing to the chelating
function of carboxylate. Thus spcpϪ was reacted with Ni(OAc)2ؒ
4H2O in a metal to ligand ratio of 1 : 2 under solvothermal
conditions. As expected, complex 1 containing puckered rhom-
bus grids was obtained in high yield.
Symmetry transformations used to generate equivalent atoms. A: x, y,
z ϩ 1. B: x Ϫ 1, y, z.
Crystal structure
CCDC reference number 165608.
See http://www.rsc.org/suppdata/dt/b1/b108449f/ for crystal-
lographic data in CIF or other electronic format.
The crystallographic analysis reveals that complex 1 is a two-
dimensional grid-like polymer. As shown in Fig. 1, each nickel
Physical measurements
The infrared spectra were taken on a Magna 750 FTIR spectro-
photometer as KBr pellets in the 4000–400 cmϪ1 region. The
NMR spectrum was recorded on a Varian Inova-500 spectro-
photometer at room temperature and the chemical shifts
were quoted in δ (ppm) relative to the deuterated solvent used.
The elementary analyses were performed on an Elementar
Vario ELIII elemental analyzer. Variable-temperature magnetic
susceptibility data for a polycrystalline sample of complex 1
were obtained in an external field of 10.0 kG on a Quantum
Design PPMS Model 6000 magnetometer from 300 to 4 K.
Results and discussion
Syntheses
Recently, we have developed a convenient method for the syn-
theses of flexible organic ligands containing sulfur and nitrogen
donor atoms, such as 2,4,6-tris[(4-pyridyl)methylsulfanyl]-
1,3,5-triazine (tpst) and 1,2-bis[(2-pyrimidinyl)sulfanymethyl]-
benzene (bpsb). By introducing these ligands during the
preparation of metal complexes, we have isolated a series of
novel transition metal complexes with nanometer-sized
metallosupramolecular cubes, nanometer-sized tubes, single-
stranded helical chains, or two-dimensional lamellar network
structures.15,16 The success prompted us to extend our work to
flexible ligands containing sulfur, nitrogen and oxygen donor
atoms. Thus the sodium salt of 4-(bromomethyl)phenylcarb-
oxylate was selected as a starting material to react with the
sodium salt of 4-sulfanylpyridine and Na(spcp) was obtained
as a white powder in satisfactory yield.
Fig. 1 The coordination environment of Ni() in 1.
ion is coordinated by two nitrogen atoms from two ligands and
four oxygen atoms of the carboxylate groups from two other
ligands in a highly distorted octahedral coordination geometry.
One nitrogen atom [N(1)] and three oxygen atoms [O(1A),
O(3B) and O(4B)] form the equatorial plane with the deviation
of Ni from the mean plane of [N(1)O(1A)O(3B)O(4B)] being
0.16 Å, while the axial positions are filled by one nitrogen atom
[N(2)] and one oxygen atom [O(2A)] with the N(2)–Ni–O(2A)
angle being 155.2(2)Њ. The Ni–N and Ni–O distances range
from 2.057(5) to 2.065(5) Å and 2.057(4) to 2.179(5) Å (see
Table 2), respectively, similar to those in other related grid-like
nickel complexes.1,20
Each ligand acts as a single bridge linking two nickel ions
through its nitrogen atom and carboxylate group (Scheme 1),
and each nickel ion connects four ligands to form an infinite
two-dimensional structure. The grid-like Ni4(spcp)4 species can
be viewed as the basic building block of the structure, in which
the apices are occupied by nickel ions and the sides are formed
by spcpϪ ligands. Each four Ni4(spcp)4 grids are joined together
through sharing the nickel apices to give the final two-
dimensional layer structure consisting of puckered rhombus
grids with dimensions of 11.72 × 11.09 Å based on the metal–
metal distances (Fig. 2). The most intriguing feature of the
structure is that the basic grid is puckered, different from
previously reported grid-like structures in which the basic grids
are usually coplanar or quasi-coplanar.1,20 The puckered shape
The intriguing features of spcpϪ arise not only from its flexi-
bility but also from the presence of hybrid pyridyl and benzoic
carboxylate moieties that are connected by a –CH2S– spacer.
As shown in Scheme 1, the ligand possesses four possible
bonding sites, i.e, the nitrogen atom, the sulfur atom, and the
two oxygen atoms of the carboxylate group. Because the carb-
oxylate group can adopt monodentate, chelating-bidentate,
bridging-bidentate and bridging-multidentate modes,14 rich
coordination modes of spcpϪ may be expected. If spcpϪ
coordinates to metal ions through its carboxylate group and
pyridyl nitrogen and the carboxylate group adopts a chelating-
bidentate mode, it may be used as a mono-anionic singly bridg-
ing ligand. Accordingly, a grid-like structure may be expected
by introducing metal ions favoring a hexa-coordination mode,
with the advantage that no co-ligand is needed for saturating
J. Chem. Soc., Dalton Trans., 2002, 1354–1357
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Fig. 4 Temperature-dependent magnetic susceptibility of 1: (᭺ ) χM,
(∆) µeff, (—) the best fit obtained.
(1)
Fig. 2 The two-dimensional layer structure of 1.
The best fit (assuming ZJ = 0) of the experimental data to
eqn. (1) yielded J = Ϫ0.10 cmϪ1, g = 2.13, with an agreement
of the basic grid in 1 is understandable, because the sp3
configurations of C and S of the –CH2S– spacer force the spcpϪ
ligand to be non-linear, generating the non-linear grid sides and
thereby the puckered grids. Actually, the C–C–S and C–S–C
angles of spcpϪ in 1 range from 116.6(5) to 126.3(5) and
104.2(3) to 104.4(3)Њ, respectively; the phenyl and pyridyl rings
in each ligand are almost perpendicular to each other with an
average dihedral angle of 87.7(6)Њ. These structural data clearly
depict the non-linear configuration of spcpϪ in 1. It should be
noted that the actual structure of the two-dimensional layer is
wave-like, the convex surface of one layer is immersed into the
concave surface of an adjacent layer to get a tightly packed
structure without any guest molecules (Fig. 3).
2
factor R = Σ(χobsd Ϫ χcacld)2/Σχobsd = 2.8 × 10Ϫ4. The J value is so
small that one cannot attribute it unambiguously to an intra-
molecular interaction. We may conclude that the interaction
via the spcpϪ bridge is very weak, suggesting that there is no
efficient orbital pathway for super-exchange between Ni()
ions through the spcpϪ bridge, because the sp3 configurations of
C and S of the –CH2S– spacer in spcpϪ make the long and
flexible ligand unconjugated and unfavorable for electronic
interactions.
Conclusion
In summary, a novel long and flexible mono-anionic ligand
(spcpϪ) comprising hybrid pyridyl and benzoic carboxylate
moieties linked by a –CH2S– spacer was synthesized. The
polymeric complex [Ni(spcp)2]n (1) consisting of puckered
rhombus grids with dimensions of 11.72 × 11.09 Å was
obtained in the reaction of Ni(OAc)2ؒ4H2O with Na(spcp)
under solvothermal conditions. The non-linear configuration
of spcpϪ induces the puckered basic grid and the wave-like
two-dimensional structure of 1.
Magnetic properties
Variable-temperature magnetic susceptibilities in the range of
4–300 K are shown in Fig. 4. The experimental µeff value per
Ni() ion at room temperature is ca. 3.02 µB, within the range
expected for a high-spin Ni() ion. Upon cooling, the magnetic
moment decreases slightly to a value of 2.87 µB at 5.93 K. This
Ϫ1
indicates that the interaction is very weak. The χM versus T
plot is essentially linear, and least-squares fitting of the data to
the Curie–Weiss law gave C = 1.13 cm3 molϪ1 K and θ = Ϫ0.47
K. This Curie–Weiss behavior may arise from antiferro-
magnetic interactions between Ni() ions. Assuming an iso-
tropic exchange between Ni() ions, the magnetic susceptibility
per Ni() ion can be expressed as
Acknowledgements
We are grateful to the NNSF of China for financial support and
the Key Project from CAS.
Fig. 3 The tightly packed structure of 1, only two layers are shown for clarity.
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