A borromean weave coordination polymer sustained by urea-sulfate hydrogen bonding and its selective anion separation properties

Article abstract of DOI:10.1021/cg901159r

A 3-fold (2D -2D) (6,3) Borromean weave coordination polymer sustained by urea-sulfate hydrogen bonding is formed when N,N′-bis(3-pyridyl)-p- phenylenebisurea (L1) is reacted with ZnSO₄·7H₂O, whereas the corresponding bis-amide deriv

Full text of DOI:10.1021/cg901159r

DOI: 10.1021/cg901159r
A Borromean Weave Coordination Polymer Sustained by Urea-Sulfate
Hydrogen Bonding and Its Selective Anion Separation Properties
2010, Vol. 10
483–487
N. N. Adarsh and Parthasarathi Dastidar*
Department of Organic Chemistry, Indian Association for the Cultivation of Science (IACS),
2A & 2B Raja S C Mullick Road, Jadavpur Kolkata - 700032, West Bengal, India
Received September 22, 2009; Revised Manuscript Received November 20, 2009
ABSTRACT: A 3-fold (2D f 2D) (6,3) Borromean weave coordination polymer sustained by urea-sulfate hydrogen bonding is
formed when N,N0-bis(3-pyridyl)-p-phenylenebisurea (L1) is reacted with ZnSO4 7H2O, whereas the corresponding bis-amide
3
derivative N,N0-bis(3-pyridyl)terephthalamide (L2) gave a coordination polymer displaying a 2D corrugated sheet under the identical
reaction conditions; sulfate anion can be selectively separated from a complex mixture of anions (sulfate, nitrate, perchlorate, and
triflate) by in situ crystallization of these coordination polymers.
Borromean links is a fascinating topology that has inspired
human beings, and many such examples exist in history, arts, and
science.1 In the Borromean topology, three closed circuits are
entangled in such a fashion that all the entangled components can
be separated just by breaking one of the circuits. Nature adopts
interpenetration via topological Hopf links (two closed circuits
interpenetrated just once, i.e. catenation) in order to achieve close
packing to fill the void space in the crystal. The Borromean link is
an alternative method of entanglement without a Hopf link. The
intriguing feature of the interweaving phenomenon of Borro-
mean is that none of the circuits is catenated to another one but
overall they are inseparable (Figure 1).
Figure 1. Borromean entanglement and Hopf link.
Borromean topology has been a synthetic goal of interest in
molecular form inspired by some theoretical studies.2 The first
such molecular Borromean link was achieved by DNA nano-
technology in 1997.3 There have been a handful Borromean
coordination polymers which were not recognized by the original
authors but correctly classified by Carlucci et al. in 2003.4 Since
then Borromean coordination polymer has become a synthetic
goal as it is aesthetically pleasing, intellectually intriguing, synthe-
tically challenging and mechanically strong.5-10 Most of the
reported examples display 2D f 2D Borromean entanglement
involving 3-fold (6,3) honeycomb layers (hcbl). More recently, a
2D f 2D Borromean link involving 3-fold (4,4) sql layers has
been reported.11 However, deliberate construction of Borromean
network is a daunting task.12
to the formation of intriguing coordination polymeric systems for
material applications such as sorption,15 inclusion materials,16
and selective separation of anions.17 We14a,15,18 and others19 have
shown that a urea moiety can interact efficiently with various
oxoanions. In fact, in a communication published in the recent
past,20 we have exploited urea-sulfate hydrogen bonding inter-
actions togeneratea porous self-assemblyof nanorods based ona
simple coordination polymer.
In this communication, we report the synthesis and single
crystal X-ray structures of two coordination polymers, namely
[{Zn(μ-L1)1.5(SO4)} xH2O]ꢀ (1) and [{Zn(μ-L2)(μ-SO4)} xH2O]ꢀ
3
3
(2) derived from N,N0-bis(3-pyridyl)-p-phenylenebisurea (L1) and
N,N0-bis(3-pyridyl)terephthalamide (L2). The ditopic ligands L1
and L2 equipped with a hydrogen bonding backbone (bis-urea and
bis-amide, respectively) have not been exploited in coordination
polymers.26 Coordination polymer 1 displays a 3-fold (2D f 2D)
Borromean topology involving a (6,3) hcbl network, mainly sus-
tained by interlayer urea-sulfate hydrogen bonding and is capable
of selectively separating an important anion such as sulfate from a
complex mixture of various oxoanions.
The reported Borromean coordination polymeric systems are
known to be sustained by various noncovalent interactions such
as hydrogen bonding,13a halogen bonding,8,13b
π
π stack-
3 3 3
ing,13c and Ag Ag6,13d and Au Au13e interactions in addi-
3 3 3
3 3 3
tion to van der Waals contacts. Examination of the reported
structures involving (6,3) hcbl reveals that highly undulating layer
structures withlarge honeycombcavities, presumablytoensure 3-
fold interpenetration and interlayer nonbonded interactions, are
some of the criterion for Borromean link formation.
Leaf shaped colorless crystals of 126 were readily obtained by
layering an aqueous methanolic solution of ZnSO4 7H2O over a
3
DMF solution of L1 taken in a 1:2 (metal/ligand) molar ratio.
The crystal of 1 belongs to the trigonal R3 space group.27 The
asymmetric unit consists of a Zn(II) metal ion, a sulfate counter-
anion, half of L1, and a water molecule; the metal center, the
sulfate, andthe water molecule werelocatedona 3-foldsymmetry
axis whereas the ligand L1 was located on an inversion center.
The counteranion sulfate was found to display rotational dis-
order around the 3-fold symmetry axis. The metal center Zn(II)
displayed a slightly distorted trigonal bipyramidal geometry
[—N-Zn-N = 119.88(2)ꢁ; —N-Zn-O = 81.7(6)-109.8(4)ꢁ]
wherein the equatorial positions were occupied by the pyridyl N
atoms of L1 and the apical positions were coordinated by the
water moleculeandO atomofthe counteranionsulfate. Extended
We are interested in coordination polymeric compounds de-
rived from noninnocent ligands which are equipped with supra-
molecular functionalities such as hydrogen bonding. The
hydrogen bonding functionalized ligands are capable of interact-
ing with the counteranions, may induce complementary internet-
work interactions, and limit the plausible supramolecular
architecture of the coordination polymers.14 In this context, we
have been exploiting the hydrogen bonding backbone and ligat-
ing topology of the ligands; the specific hydrogen bonding
interactions of the counteranions with the ligand backbone lead
*E-mail: parthod123@rediffmail.com; ocpd@iacs.res.in.
r
2009 American Chemical Society
Published on Web 12/18/2009
pubs.acs.org/crystal

484 Crystal Growth & Design, Vol. 10, No. 2, 2010
Adarsh and Dastidar
Scheme 1. syn-anti-syn and syn-syn-syn Conformations of
L1 and L2
coordination involving the ligand L1 in its syn-anti-syn con-
formation (Scheme 1 and Scheme S1 of the Supporting In-
formation) and the metal center in this fashion resulted in the
formation of large hexagonal rings having a van der Waals inner
˚
diameter of approximately 19.0 A. The vertices of each hexagon
are occupied by Zn(II), and the conformation of each hexagon
resembles that of a chair. Extended coordination of this kind
ultimately resulted in the formation of a highly undulating 2D
honeycomb network involving a (6,3) net. The 2D networks are
further packed along the crystallographic c-axis, displaying a
3-fold interpenetration without Hopf links, resulting in a Borro-
mean entanglement. TOPOS21 analysis suggests that it is a case
of 3-fold (2D f 2D) Borromean entanglement, as depicted in
Figure 2. It is clear from Figure 2 that the green layer is always
above the blue layer, which is in turn always above the red layer,
which is always above the greenlayer. It maybenoted that notwo
layers display catenation (Hopf link) but are involved in 3-fold
interpenetration. Since the network structure does not have any
Hopf link and the entangled 2D layers can be separated just by
breaking one of the layers, this network can be categorized as
Borromean entanglement. The X-ray structure of 1 also reveals
that urea-sulfate hydrogen bonding interactions play a crucial
role in stabilizing such Borromean entanglement; sitting on a
3-fold symmetry, three O atoms of the sulfate counteranion were
available for hydrogen bonding interactions, and as a result, it
indeed formed hydrogen bonding with the three urea moieties
Figure 2. Crystal structure illustration of 1: (a) chair conformation
of the hexagonal ring; (b) highly undulating (6,3) honeycomb layer;
Borromean entanglement (c) in the space filling model and (d) in a
TOPOS schematic representation.
coming from three different 2D hcbl networks [N O = 2.62-
3 3 3
˚
(7)-2.94(7) A] (Figure 3).
Previously reported Borromean coordination polymers dis-
played mainly metallophilic (argentophilic6,13d or aurophilic13e
)
interactions, which were not possible in the present case. Thus,
the specific hydrogen bonding between urea and sulfate as
discussed above must be one of the most crucial interactions
responsible for the stabilization of such a Borromean entangle-
ment. The other examples wherein the Borromean entangle-
ment is sustained by specific hydrogen bonding involving a
ligand backbone and counteranions are reported by Steed13d
and Vittal.13a
To attain a Borromean entanglement involving a (6,3) hcbl net,
formation of a highly undulating 2D layer is important. From a
ditopic ligand such as L1, such nonplanar 2D layer formation is
dependent on the conformation of the ligand. For example, in the
present case (i.e., coordination polymer 1), the ligand L1 dis-
played a syn-anti-syn conformation, which ultimately led to the
formation of a 2D undulating layer structure via extended
coordination with the metal center. We were curious to see what
happens if we change the hydrogen bonding backbone of L1 from
bis-urea to bis-amide as in L2. Unlike urea-sulfate hydrogen
bonding interactions, which display an eight membered hydrogen
bonded ring structure (Figure 3), amide-sulfate hydrogen bond-
ing interactions lack structural specificity, displaying less direc-
Figure 3. Urea-sulfate hydrogen bonding interactions present
in 1.
and ZnSO4 7H2O under otherwise identical conditions for synthe-
3
sizing coordination polymer 1 and to then characterize it by single
crystal X-ray diffraction. Thus, block shaped crystals of 226 were
readily obtained by reacting L2 and ZnSO4 7H2O under identical
3
conditions as applied in the case of 1. The crystals of 2 belong to the
noncentric monoclinic space group P21.27 A fully occupied Zn(II),
one molecule of L1, one sulfate ion, and one water molecule are
located in the asymmetric unit. The metal center Zn(II) displays a
slightly distorted tetrahedral geometry [—O-Zn-O =112.33(12);
—O-Zn-N = 101.58(14)-117.10(15)ꢁ] of which two of the
tional N-H O interactions. Since ligand L2 can also attain a
3 3 3
similar conformation, such as L1, and, therefore, can induce the
formation of Borromean entanglement, it was considered worth-
while to isolate the reaction product from a reaction between L2

Communication
Crystal Growth & Design, Vol. 10, No. 2, 2010 485
Figure 4. Crystal structure illustration of 2: (a) 2D corrugated
sheet; (b) parallel packing of the 2D sheets.
Figure 5. FT-IR comparison plots of (a) 1 and (b) 2 recorded under
various conditions: noncompetitive condition (red); condition I
(blue); condition II (green).
coordination sites are occupied by the pyridyl N atoms of L2
and the other two sites are occupied by the O atoms of the
sulfate ion and water. Interestingly, the ligand moiety displays
a syn-syn-syn conformation, unlike its bis-urea counterpart
in 1 (Scheme 1 and Scheme S1 of the Supporting Information).
As a result of the extended coordination between the ligand L2
and the adjacent metal center, a 1D zigzag coordination
polymeric chain is formed. The 1D chains are further as-
sembled into a 2D corrugated sheet structure by the counter-
anion sulfate, which acts as a bridging ligand. The 2D sheets
are packed on top of each other and are stabilized by hydrogen
bonding interactions involving amide N-H and the O atom
systems can be exploited to recognize and separate important
anions.24,17 Recently, in situ crystallization of coordination poly-
mers has been proposed to be a viable method to separate a
targeted anion from a complex mixture of anions,23 wherein the
organic linker and metal salts having various counteranions are
allowed to crystallize together. Since sulfate isan important anion
to be separated,25 we carried out systematic studies of anion
separation using in situ crystallization of 1 and 2 under compe-
titive conditions as described below.
Sulfate, perchlorate, nitrate, and triflate as Zn(II) salts were
selected for this study. Two different experiments for each
metal-organic system (namely 1 and 2) were adopted. In the
first experiment (condition I), the ligand was reacted with a
mixture of Zn(II) salts having different oxoanions in the molar
ratio of 2:1 (ligand:metal). In the other experiment (condition II),
the reaction was performed using 2:1:2 (ligand:ZnSO4:Zn-other
oxanions). In all the experiments, the experimental conditions
(solvents, temperature, etc.) were kept unchanged, as in the
synthesis of 1 and 2 (for details, see the Supporting Information).
The reaction products obtained in these experiments were char-
acterized by using X-ray powder diffraction (XRPD), FT-IR,
elemental analysis, and energy dispersive X-ray spectrometry
(EDX). It is clear from Figure 5 that the FT-IR spectra recorded
under various conditions are nearly identical. A strong and broad
band at 1116 and 1132 cm-1 in the FT-IR data of 1 and 2,
respectively, indicates the presence of sulfate anion (νasymm S-O)
(Table S1 of the Supporting Information). These results indicate
that the coordination polymers 1 and 2 were crystallized out
exclusively in the presence of other oxoanions. Both elemental
analysis and EDX also support these findings (Table S2 and
Figures S3 and S4 of the Supporting Information). Finally, the
nearly identical XRPD patterns recorded under various condi-
tions as depicted in the Figure 6 strongly support the selective
separation of sulfate as the corresponding coordination polymers
1 and 2 from a complex mixture of oxoanions. It may be noted
here that the reaction of both L1 and L2 with Zn(II) salts (in
separate experiments) having various counteranions such as
nitrate, perchlorate, and triflate resulted in crystallization of
free ligands, which indicated less reactivity of these ligands
toward these metal salts. However, in the presence of a mixture
of Zn(II) salts having various counteranions such as sulfate,
nitrate, perchlorate, and triflate, only 1 and 2 were separated
out as neat crystals, which was advantageous in separating sulfate
from a complex mixture. This could be due to both less reactivity
˚
of the sulfate counteranion [N O = 2.904(4)-2.979(5)A,
3 3 3
—N-H O = 152(1)-157(1)ꢁ] (Figure 4).
3 3 3
During the refinement, significant amounts of smeared elec-
tron densities were located in the difference Fourier map in both
the structures. A SQUEEZE22 calculation indicated the presence
of 623 e/unit cell with a solvent accessible area volume of 2723.5
3
˚
A in 1. Thismaybeattributed to10water molecules inthe crystal
lattice. Thermogravimetric analysis (TG) also supports this find-
ing; a weight loss of 22.0% within the temperature range 19-272
ꢁC may be assigned to 11 water molecules (1 coordinated þ 10
lattice included water molecules; calcd weight loss of 11 water =
22.5%), which is in agreement with the single crystal structure
and SQUEEZE results (Figure S1 of the Supporting In-
formation).
The overall packing displays tiny channels running down
the crystallographic a-axis wherein some disordered electron
densities were located in the refinement cycles of 2. These
electron densities were attributed to disordered water mole-
cules and squeezed out in the final cycles of refinement.
SQUEEZE calculations showed the presence of 13 e/unit cell
3
˚
(with a solvent accessible area volume of 57.3 A ), which
amounts to 6.5 e per asymmetric unit; this may be attributed
to 0.65 water molecule. Since the data were collected at room
temperature, loss of lattice-included solvent such as water in
the present case may take place. TG data further support this
assignment. In TG, a weight loss of 2.6% is observed within
the temperature range 24-185 ꢁC whereas the calculated
weight loss considering 0.65 water molecule in the asymmetric
unit as suggested in the SQUEEZE calculation is 2.4%, which
is in agreement with the experimental results (Figure S2 of the
Supporting Information).
One of the important aspects of metal-organic hybrid com-
pounds such as coordination polymers is the ability to exchange
anions.23 It has already been demonstrated that metal-organic

486 Crystal Growth & Design, Vol. 10, No. 2, 2010
Adarsh and Dastidar
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of these ligands toward these metal salts and weaker hydrogen
bonding interactions with the ligand backbone (urea and amide).
Thus, we have reported one of the rare examples of a Borro-
mean coordination polymer (1) mainly sustained by urea-sulfate
hydrogen bonding interactions. This Borromean entanglement
in 1 is devoid of any metallophilic interactions which are the
main stabilizing factors in the other reported Borromean struc-
tures.5,13d Interestingly, the bis-amide ligand L2 failed to produce
a Borromean topology, which could be due to the syn-syn-syn
conformation of L2 as well as the less directional amide-sulfate
hydrogen bonding interactionscompared tothatof urea-sulfate.
Most interestingly, both the coordination polymers 1 and 2 could
be exploited to separate selectively an important anion sulfate
from a complex mixture of various oxoanions such as sulfate,
nitrate, perchlorate, and triflate via in situ crystallization of the
corresponding coordination polymers.
Acknowledgment. We thank the Department of Science &
Technology (DST), New Delhi, India, for financial support. N.
N.A thanks IACS for research fellowships. Single crystal X-ray
diffraction was performed at the DST-funded National Single
Crystal Diffractometer Facility at the Department of Inorganic
Chemistry, IACS. We are thankful to Prof. Vladislav. A. Blatov,
and Prof. Davide. M. Proserpio for fruitful discussions during the
time of manuscript preparation.
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Supporting Information Available: Hydrogen bonding para-
meters for 1 and 2, Scheme S1, TG (Figures S1 and S2), experi-
mental details for anion separation studies, FT-IR (Table S1),
elemental analysis (Table S2), EDX (Figures S3 and S4), and CIF
data for 1 and 2. This material is available free of charge via the
Internet at http://pubs.acs.org.
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FT-IR (KBr pellet): 3346 (s, amide ν N-H), 3265s, 3047 (m,
aromatic ν C-H), 1679 (s, amide ν CdO), 1652s, 1618 (s, amide
δ N-H), 1562s, 1527s, 1483s, 1415s, 1334s, 1317m, 1284s, 1259w,
1234w, 1190w, 1105w, 1029w, 889w, 865w, 833w, 798w, 702w,
638w, 621w, 540w, 507w cm-1. HRMS calcd for C18H14N4O2 [M þ
H]þ: 319.2; found: 319.4. 1 was synthesized by layering an aqueous
methanolic solution of ZnSO4 7H2O (17 mg, 0.059 mmol) over a
3
DMF solution of L1 (41 mg, 0.118 mmol). After three days, X-ray
quality crystals were obtained by a slow evaporation technique.
Yield: 77% (40 mg, 0.046 mmol). Anal. Calcd for
C27H26N9O8SZn 8H2O (%): C, 38.33; H, 5.00; N, 14.90. Found:
3
(26) Syntheses of L1 and L2: The syntheses of L1 and L2 were reported
in the context of organic crystal engineering. Byrne, P.; Turner,
D. R.; Lloyd, G. O.; Clarke, N.; Steed, J. W. Cryst. Growth Des.
2008, 8, 3335 for L1. Rajput, L.; Singh, S.; Biradha, K. Cryst.
Growth Des. 2007, 7, 2788 for L2. However, we have followed
different methods to synthesize both the ligands, which are as
follows.L1: To a stirring solution of 3-aminopyridine (686 mg, 7.29
mmol) and triethylamine (3 mL) in 100 mL of anhydrous dichlor-
omethane (DCM) at ice cold temperature under an inert atmo-
sphere was added triphosgene (900 mg, 3.030 mmol), and the
solution was kept stirring for 20 min. p-Phenylene diamine (394
mg, 3.65 mmol) in 50 mL of dry DCM was then added dropwise.
The pale yellow colored solution became a thick brown precipitate,
which was further stirred at room temperature for 24 h. After
filtration, the precipitate was washed with DCM, air dried, and
treated with a 5% NaHCO3 solution. The resultant solid was
filtered, washed with distilled water, and dried. The crude product
thus obtained was then dissolved in DMSO, and further addition of
distilled water gave L1 as a gelly precipitate, which was then
filtered, washed with excess water, and air dried (700 mg, 55%
yield). mp 280-282 ꢁC. Anal. Calcd for C18H16N6O2 (%): C, 62.06;
C, 38.72; H, 4.76; N, 15.33. FT-IR (KBr pellet): 3286 (s, amide ν N-
H), 3085 (m, aromatic ν C-H), 1728 (s, urea ν CdO), 1691(s, urea δ
N-H), 1649s, 1595s, 1562s, 1515m, 1483s, 1423s, 1292s, 1228s,
1213s, 1118 (s, SO42- νasymm S-O), 1060m, 906w, 810m, 698s, 651s,
524m cm-1. 2 was synthesized by layering an aqueous methanolic
solution of ZnSO4 7H2O (18 mg, 0.063 mmol) over a DMF
3
solution of L2 (40 mg, 0.126 mmol). After one week, X-ray quality
crystals were obtained by a slow evaporation technique. Yield:
66% (20 mg, 0.041). Anal. Calcd for C18H14N4O6SZn (%):
C, 45.06; H, 2.94; N, 11.68. Found: C, 44.88; H, 2.76; N, 12.20.
FT-IR (KBr pellet): 3267 (m, amide ν N-H), 3076 (m, aromatic
ν C-H), 1677 (s, amide ν CdO), 1614 (s, amide δ N-H), 1585s,
1554s, 1508s, 1483s, 1425s, 1332s, 1290s, 1253w, 1203s, 1132 (sb,
SO42- νasymm S-O), 1060m, 1018s, 904w, 817m, 719m, 698m, 657m,
626m cm-1
.
(27) X-ray crystallography: X-ray single crystal data were collected
˚
using Mo KR (λ = 0.7107 A) radiation on a BRUKER APEX II
diffractometer equipped with a CCD area detector. Data collec-
tion, data reduction, and structure solution/refinement were car-
ried out using the software package of SMART APEX. All
structures were solved by direct methods and refined in a routine
manner. In most of the cases, non-hydrogen atoms were treated
anisotropically. Whenever possible, the hydrogen atoms were
located on a difference Fourier map and refined. In other cases,
the hydrogen atoms were geometrically fixed. CCDC (CCDC No:
748201 and 748202) contains the supplementary crystallographic
data for this paper. 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, U.K. Fax: (þ44) 1223-336-033. E-mail: deposit@ccdc.
cam.ac.uk). Crystal data for 1: C27H26N9O8SZn, FM = 702.00,
1
H, 4.63; N, 24.12. Found: C, 62.42; H, 4.42; N, 24.14. H NMR
(300 MHz, DMSO-d6): δ = 8.79 (2H, s, N-H), 8.69 (2H, s, N-H),
8.60 (2H, s, Py-H), 8.19-8.17 (2H, d, J = 4.1 Hz, Py-H), 7.95-7.93
(2H, d, J = 7.0 Hz, Py-H), 7.39 (4H, s, Ar-H), 7.33-7.28 (2H, dd,
J = 4.68, 8.22 Hz, Py-H) ppm. FT-IR (KBr pellet): 3286 (s, urea
ν N-H), 3178w, 3126 (m, aromatic ν C-H), 3080w, 3041m, 3024m,
2926w, 1894w, 1693m, 1647 (s, urea ν CdO), 1597 (s, urea δ N-H),
1566s, 1514s, 1479s, 1419s, 1404s, 1327m, 1305s, 1284s, 1247m,
1228s, 1188s, 1120w, 1103w, 1024w, 935w, 898w, 848m, 812m,
765w, 746w, 702s, 669w, 624w, 613w, 588w, 526m cm-1. HRMS
calcd for C18H16N6O2 [M þ H]þ: 349.1368; found: 349.2404. L2:
To a solution of 3-aminopyridine (1.069 g, 11.38 mmol) and
triethylamine (8 mL) in 80 mL of dry THF under ice cold condi-
tions under a nitrogen atmosphere, terephthaloyl chloride (1.1 g,
5.42 mmol) in dry THF (20 mL) was added dropwise. The thick
white colored precipitate thus formed was kept stirring with reflux
for 8 h. After filtration, the precipitate was washed with THF, air
dried, and treated with 5% NaHCO3 solution. It was then washed
in distilled water, dried, and recrystallized from DMSO (yield: 1.2
g, 70%) Anal. Calcd for C18H14N4O2 (%): C, 67.91; H, 4.43; N,
17.60. Found: C, 67.47; H, 4.40; N, 17.86. 1H NMR (200 MHz,
DMSO-d6): δ = 10.64 (2H, s, N-H), 8.98 (2H, s, Py-H), 8.37-8.34
(2H, d, J = 9 Hz, Py-H), 8.25-8.22 (2H, d, J = 9 Hz, Py-H), 8.15
(4H, s, Ar-H), 7.47-7.40 (2H, dd, J = 4.6, 8.2 Hz, Py-H) ppm.
trigonal space group R3 (No. 148), a = 15.0798(19), b =
3
15.0798(19), c = 35.075(9) A. V = 6907(2) A , T = 100 K, Z =
˚
˚
6. Dc = 1.013 g cm-3. F(000) = 2166, λ(Mo KR) = 0.71073 A, μ =
˚
0.622 mm-1, 2θmax = 41.46ꢁ, 7580 collected reflections measured,
1588 observed (I > 2σ(I)) 163 parameters; Rint = 0.0367, R1
=
0.0866; wR2 = 0.2358 (I > 2σ(I)), R1 = 0.0970; wR2 = 0.2462
(all data) with GOF = 1.087. Crystal data for 2: C18H14N4O6SZn,
FM = 479.76, monoclinic, space group P21 (no. 4), a =
˚
4.9904(17), b = 19.473(7), c = 9.891(3)A. β = 93.762(5)ꢁ. V =
959.1(6) A , T = 298 K, Z = 2. Dc = 1.661 g cm-3. F(000) = 488,
3
˚
λ(Mo KR) = 0.71073 A, μ = 1.435 mm-1, 2θmax = 47.98ꢁ, 8312
˚
reflections measured, 3000 observed (I > 2σ(I)), 271 parameters;
Rint = 0.0415, R1 = 0.0318; wR2 = 0.0628 (I > 2σ(I)), R1
0.0367; wR2 = 0.0646 (all data) with GOF = 1.006.
=