Coordination Polymers from Functionalized Bipyrimidine Ligands and Silver(I) Salts

Article abstract of DOI:10.1021/acs.cgd.7b01657

Readily functionalizable bipyrimidine compounds were prepared for the first time, and their coordination chemistry with silver salts was explored. Solution ¹H NMR spectroscopy experiments indicated that the ligands rapidly form complexes with s

Full text of DOI:10.1021/acs.cgd.7b01657

Article
pubs.acs.org/crystal
Cite This: Cryst. Growth Des. XXXX, XXX, XXX−XXX
Coordination Polymers from Functionalized Bipyrimidine Ligands
and Silver(I) Salts
Guillaume Beaulieu-Houle,† Nicholas G. White,†,‡ and Mark J. MacLachlan*,†
†Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
‡Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, Australia
S
* Supporting Information
ABSTRACT: Readily functionalizable bipyrimidine compounds were prepared
for the first time, and their coordination chemistry with silver salts was
explored. Solution 1H NMR spectroscopy experiments indicated that the
ligands rapidly form complexes with silver(I) salts, and coordination at a first
site inhibits coordination of a second cation to the ligand, thus favoring 1:1
complexes in solution. These 1:1 units self-assemble into one-dimensional
chains in the solid state, even in the presence of excess Ag(I). Structurally
diverse coordination polymers exhibiting different coordination numbers and
geometry were characterized by single crystal X-ray crystallography. Our results
demonstrate that a modification to the ligand, distal from the binding site,
affects the coordination chemistry and supramolecular structure of these complexes.
metal ions and a π-conjugated pathway that can mediate
electronic or magnetic interactions between metal centers. One
important difference between these three ligands is that 2,2′-
bipyridine generally only coordinates to a single metal ion,
whereas 4,4′-bipyridine and 2,2′-bipyrimidine can bridge two
metal centers.
A recent important experiment demonstrated that bipyr-
imidine could link Co(II) centers to form a controllable spin
system through switching of coupled spins in a single-molecule
junction. In that work, the bipyrimidine moiety linked two
Co(II) spin centers forming a combined controllable spin
system.24
Despite the attractive properties of 2,2′-bipyrimidine as a
bridging ligand, there are a limited number of reports of
functionalized analogues, except for methylated derivatives.
Therefore, developing a facile route to functionalized 2,2′-
bipyrimidine is attractive for exploring its use in supramolecular
chemistry and may open a path to new families of coordination
polymers with interesting properties.
In this work, we describe the synthesis and characterization
of four new ligands based on 2,2′-bipyrimidine. We
demonstrate that these compounds are effective ligands for
silver(I) cations to produce coordination polymers. The
interesting coordination polymers obtained were studied by
single crystal X-ray diffraction (SCXRD). This new route to
coordination polymers containing bipyrimidine may lead to
diverse new materials with interesting and tunable properties.
INTRODUCTION
■
Bridging ligands have been central to the developments of
inorganic chemistry in the last century and are now at the heart
of supramolecular coordination chemistry.1 For example,
pioneering work by Creutz and Taube on bimetallic
compounds bridged by 1,4-pyrazine ligands demonstrated the
principles of inner sphere electron transfer.2 In addition, 1,4-
benzenedicarboxylate is the key bridging ligand in the
archetypical metal−organic framework, MOF-5.3 Other N-
heterocyclic bridging ligands, such as pyrazolate4 and
imidazole,5−9 have also been employed to create fibers10 and
liquid crystals.11−14 Furthermore, metallosupramolecular struc-
tures, including coordination polymers15−20 and frame-
works,21,22 all use bridging ligands for structural organization.
Conjugated N-containing heterocycles are important bridg-
ing ligands. The coordination chemistry of 2,2′-bipyrimidine
ligands, however, has been understudied and underdeveloped
compared to its more prominent N-heterocyclic analogues,
2,2′-bipyridine and 4,4′-bipyridine (Figure 1).23 Nevertheless,
2,2′-bipyrimidine shares the key features of each of these
ligands: preorganized nitrogen donor atoms that can chelate to
Received: November 28, 2017
Revised: February 14, 2018
Figure 1. Comparison between bipyridine and bipyrimidine ligands.
© XXXX American Chemical Society
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DOI: 10.1021/acs.cgd.7b01657
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RESULTS AND DISCUSSION
■
Synthesis of the Ligands. Our approach to mono-
functionalized 2,2′-bipyrimidine ligands was inspired by a
method described in a patent, where the synthesis of
bipyrimidine ethyl ester 3 was first reported.25 We found,
however, that the one-pot procedure described therein was
unable to yield the desired compound due to an error in the
procedure (the 1,3-dicarbonyl used is not a dialdehyde but an
aldehyde and a methyl ketone, resulting in a methyl substituted
ring). Consequently, it was necessary to independently
establish a synthetic route to compound 3.
Scheme 1 shows our route to monofunctionalized bipyr-
imidine derivatives. Reaction of the amidinium 1 with
Scheme 1. Synthesis of Functionalized 2,2′-Bipyrimidine
Ligands
Figure 2. Downfield region of the 1H NMR spectra of top, L1; middle,
ligand after addition of one equivalent of AgPF6; bottom, ligand after
the addition of four equivalents of AgPF6 (CD3CN, r.t., 400 MHz).
1
exchange. The H NMR spectrum of the solution cooled to
−35 °C also showed only three signals for the aromatic
protons, signifying that even at this low temperature the ligand
and metal are still in fast exchange.
We then studied Ag(I) complexation in more detail using
1
quantitative H NMR titration experiments. As can be seen in
Figure 3, a sigmoidal binding curve is obtained, suggesting the
dialdehyde 2 results in the formation of the para-substituted
pyrimidine ring 3 in 58% yield. The structure of this compound
was verified by 1H and 13C NMR spectroscopy, mass
spectrometry, and elemental analysis. Alkaline hydrolysis of
ester 3 gave compound 4 with a readily functionalizable
carboxylic acid group at the 5-position in 89% yield.
We found that the amide coupling reagent pair EDCI·HCl
and hydroxybenzotriazole (HOBt) worked well to provide
ligands L1−L4. Conveniently, the pure product precipitated
out of solution as the reaction proceeded or upon the addition
of water, and column chromatography was unnecessary to
purify the products. New compounds L1−L4 were charac-
1
terized by mass spectrometry, H NMR, 13C NMR, and IR
spectroscopy. In addition, compounds L3 and L4 were
characterized by SCXRD. The molecular structures of L1−L4
are shown in Figure S1.
Binding of Metal Salts in Solution. To begin our studies
of the coordination chemistry of L1−L4, we turned to silver(I)
because it has been used extensively with N-containing
heterocycles. Silver(I) has a flexible geometry owing to a d10
electron configuration,26 and coordination polymers of silver
are of interest for antimicrobial agents,27 catalyst precursors,28
and electronic materials. In fact, Ag(I) has been previously
shown to form one-dimensional chains with the parent 2,2′-
bipyrimidine molecule.29,30 The diamagnetism of Ag(I) would
Figure 3. (a) Species present in solution with varying equivalents of
silver cation and (b) titration binding curve of L1 with AgPF6 showing
the shift in signal of the bipyrimidine triplet. Inset shows the sigmoidal
behavior of the signal in the region 0−1 equiv.
1
also facilitate solution studies by H NMR spectroscopy.
The complexation of AgPF6 by L1 was investigated using 1H
NMR spectroscopy. Addition of silver salt to the ligand in
CD3CN causes downfield shifts in the protons of the
bipyrimidine group and the amide hydrogen (Figure 2).
Upon addition of the AgPF6 solution to the free ligand, the
symmetry of the molecule is preserved; even when less than
one equivalent is added, only three aromatic signals are
observed, indicating that free and complexed ligand are in fast
formation of AgL2, AgL, and Ag2L species in solution
depending on the stoichiometry present. Given that saturation
is not reached even after 12 equivaents of silver cation, it
appears that binding of a second silver(I) ion to AgL is very
weak; i.e., even in the presence of excess silver, there is a
minimal amount of Ag2L complex present in solution.
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Synthesis and Structures of the Metal Complexes.
Two different silver salts, silver(I) hexafluorophosphate
(AgPF6) and silver(I) triflate (AgOTf), were used to obtain
solid-state structures of the complexes of ligands L1−L4. In
general, the ligand was dissolved in boiling acetonitrile, and
then a warm solution of the silver salt was added. The resulting
yellow liquid was filtered through glass wool and left standing
for 48−72 h to yield a crystalline precipitate. In the case of L4,
it was found that a mixture of ethanol and acetonitrile was
required to produce crystals of a size suitable for SCXRD.
The solid complexes isolated from L1−L4 and silver(I) salts
are all 1D coordination polymers as shown by SCXRD. In these
complexes, the silver atoms are either all four-coordinate, all
five-coordinate, or alternate between the two coordination
numbers along the chain. Despite this change in coordination
number, the N−Ag−N bond angle of each bipyrimidine is
always in the narrow range of 70 2°. The four-coordinate
silver cations bind to four bipyrimidine nitrogen atoms, while
the five-coordinate ones also add a solvent molecule to their
coordination sphere. Significantly, the amide group never
participates in the coordination to the silver ion. In all cases
presented here, the four-coordinate silver ions are best
described as having a pseudo-tetrahedral geometry. As well,
very little torsion is seen between the two pyrimidine rings, in
contrast to Train’s bipyrimidine-silver chain where a 27°
torsion angle is observed in the presence of a perchlorate
anion.30
In {[Ag(L1)(CH3CN)0.5]PF6}n the amide proton and
carbonyl oxygen participate in interchain hydrogen bonding,
resulting in closely packed wires; only 8.56 Å separate metal
atoms on adjacent chains. The five-coordinate metal nodes
present in the coordination polymer are of particular interest
since they impart chirality to the structure. The space group of
the crystal, P1, indicates the separation of the constituents into
the two enantiomers during crystallization. The resulting
supramolecular structure is thus of a bipyrimidine-silver wire
with decorating chains alternating in two opposite orientations
as seen in Figure 4.
surprise, the weak forces at play favored a different arrangement
of the appended chains.
As shown in Figure 5, the silver ions in this complex are all
chemically equivalent and have a distorted square pyramidal
Figure 5. Solid-state structure of complex {[Ag(L2)CH3CN]OTf}n as
determined by SCXRD. Noncoordinated anions and most hydrogen
atoms are omitted for clarity.
geometry, with the cation resting slightly above the equatorial
plane toward the axial acetonitrile ligand. The main difference
from the previous example is the relative orientation of
neighboring bipyrimidine moieties; rather than straddling the
metal node, the alkyl groups of each chain only project on one
side. It is interesting to note that the intermolecular interactions
resulting from the addition of these 10 carbon atoms are
sufficient to modify the coordination behavior of the distant
bipyrimidine moiety. As well, no hydrogen bonding is observed
between the amides of neighboring bipyrimidine units. Similar
to the previous structure, the presence of five-coordinate silver
ions imparts chirality on the structure; the two enantiomeric
chiral ribbons cocrystallize as a racemate in the space group P1.
̅
In the next step of our investigation, a different substituent
was selected to disrupt the interalkyl interactions of the
previous systems. tert-Butylphenyl has a similar length to the
hexyl chain but is more rigid and offers different potential
intermolecular interactions to influence the assembly of the
supramolecular structure.
The complexation of L3 with AgPF6 resulted in the
formation of {[Ag(L3)(H2O)0.5]PF6}n, whose structure is
shown in Figure 6. Rather than the previously observed two
chain positions, the substituents along the coordination
polymer orient themselves in four distinct directions, resulting
in an overall helical arrangement. Two chemically distinct metal
centers, with different coordination numbers, are also present in
this structure. A water molecule occupies the fifth coordination
site of every other silver ion. This helix crystallizes as separate
enantiomers in the chiral space group C2.
By replacing the tert-butyl group at the para position of the
phenylamide with the bulkier trityl group and reacting with
silver triflate, {[Ag(L4)](EtOH)OTf}n was obtained (Figure
7). This time, all of the Ag(I) cations have the same
coordination environment, a four-coordinate metal node with
pseudo-tetrahedral geometry, where adjacent bipyrimidine
planes sit almost at right angles from one another. In contrast
to the previous examples, this supramolecular structure is
achiral. Interestingly again, by increasing the steric demand of
the ligand as was observed when going from hexyl to hexadecyl,
the angle between adjacent bipyrimidines is decreased. Of all
the examples shown here, it is the least sterically demanding
hexyl chains that orient themselves farthest away from each
other.
Figure 4. Solid-state structure of the complex {[Ag(L1)(CH3CN)0.5]-
PF6}n as determined by SCXRD. Noncoordinated anions and most
hydrogen atoms are omitted for clarity.
In an effort to separate the wires from one another in the
solid-state structure, and potentially make them solution-
processable, we elongated the alkyl chain from C6 to C16 and
synthesized L2. We anticipated this would yield an insulated,
soluble bipyrimidine-silver wire after coordination with silver(I)
triflate, where the core structure of the L1 complex would be
retained, but with longer alkyl chains on both sides. To our
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proportions of silver triflate in pure acetonitrile, an interesting
behavior is observed; the precipitated product of L3 with 1
equiv of silver cation is the discrete {[Ag(L3)2]OTf·CH3CN}
complex. When three or more equivalents are used, then the
crystalline polymer {[Ag(L3)CH3CN]OTf}n is obtained. On
the other hand, when L4 is reacted with the same cation in
acetonitrile, the monometallic {[Ag(L4)2CH3CN]OTf·
CH3CN} complex rapidly crystallizes out of solution, even
when 12-fold excess silver is added (Figure 8).
Figure 6. Solid-state structure of the complex {[Ag(L3)(H2O)0.5]-
PF6}n as determined by SCXRD. Top: side-on view of the polymeric
chain. Bottom: end on view showing the four different orientations of
the substituents. Noncoordinated anions and most hydrogen atoms
are omitted for clarity.
Figure 8. Solid-state structure of the complexes (a) {[Ag(L3)2]OTf·
CH3CN}, (b) {[Ag(L4)2CH3CN]OTf·CH3CN}, and (c) {[Ag(L3)-
CH3CN]OTf}n as determined by SCXRD. Noncoordinated anions
and most hydrogen atoms are omitted for clarity.
A larger scale preparation of two of these complexes, the
polymeric material {[Ag(L3)CH3CN]OTf}n and the dimer
{[Ag(L4)2CH3CN]OTf·CH3CN} was carried out and analyzed
by IR and Raman spectroscopy (Figures S17−18), and powder
X-ray diffraction (PXRD) to show the homogeneity of the
material obtained. Figure 9 shows the PXRD traces of the
Figure 7. Solid-state structure of complex {[Ag(L4)](EtOH)OTf}n as
determined by SCXRD. Noncoordinated anions and most hydrogen
atoms are omitted for clarity.
Investigation of the Self-Assembly Process. The fact
that 1:1 Ag(I):ligand coordination polymers are formed even in
the presence of a large excess of silver hints strongly toward a
self-sorting mechanism. Our titration experiment shows that
the complexation of a silver ion in one of the two nitrogen
pockets significantly inhibits the binding of a second ion in the
adjacent pocket; a bipyrimidine ligand cannot easily satisfy two
silver(I) atoms by itself. Thus, even in the presence of excess
silver, the polymerization of the monomer AgL through
preferential self-selection into (AgL)n is favored over the
addition of a “bare silver” to the second binding site, i.e.,
formation of Ag2L. When L3 and L4 are treated with different
Figure 9. (a) PXRD trace of {[Ag(L4)2CH3CN]OTf·CH3CN} and
(b) the simulation from SCXRD. (c) PXRD trace of {[Ag(L3)-
CH3CN]OTf}n and (d) the simulation from SCXRD.
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Preparation of Bipyrimidine Ethyl Ester (3). Compound 1 (4.7 g,
26 mmol) and pyridine (50 mL) were added to crude ethyl 2,2-
diformylacetate (4.8 g, 33 mmol). The mixture was warmed to 70 °C
under a nitrogen atmosphere and stirred overnight. Pyridine was then
evaporated under reduced pressure to give a dark brown sticky solid.
The solid was washed multiple times with cold acetone to obtain
bipyrimidine ethylester as a beige powder in 58% yield (4.3 g, 19
mmol).
ground material and models obtained from the SCXRD
structure (after correction to account for the difference in
temperature between the two experimental techniques). Efforts
to scale up the other complexation reactions did not yield
sufficient material for PXRD or showed a mixture of phases.
CONCLUSIONS
■
1H NMR (300 MHz, CDCl3) δ = 9.52 (s, 2 H), 9.07 (d, J = 4.8 Hz,
2 H), 7.49 (t, J = 4.8 Hz, 1 H), 4.50 (q, J = 7.1 Hz, 2 H), 1.47 (t, J =
7.1 Hz, 3 H) ppm; 13C NMR (75 MHz, CD3CN) δ = 166.2, 164.7,
163.3, 159.5, 158.9, 125.1, 122.9, 62.9, 14.5; HRMS (ESI TOF) m/z
[M + H]+ Calcd for C11H11N4O2: 231.0882. Found: 231.0878; Anal.
Calcd for C11H10N4O2: C, 57.39; H, 4.38; N, 24.34. Found: C, 57.11;
H, 4.37; N, 23.96; melting point range: 146−149 °C.
Preparation of Bipyrimidine Carboxylic Acid (4). To a flask
containing 3 (4.3 g, 19 mmol) was added sodium hydroxide (5.0 g,
125 mmol) and water (50 mL). The mixture was stirred at room
temperature for 3 h and acidified with conc. HCl until a white
precipitate formed. The solid was filtered off and washed with cold
water to give bipyrimidine carboxylic acid 4 as a white powder in 89%
yield (3.5 g, 17 mmol).
In summary, we have developed the synthesis of 5-substituted
bipyrimidines. To demonstrate the utility of these function-
alized compounds, four new derivatives were synthesized and
used as ligands. When combined with silver(I) salts, these
bipyrimidine ligands rapidly bind to the metal ion and
crystallize into coordination polymers with diverse 1-D chain
structures. This new family of bridging ligands is promising for
the development of coordination polymers. We are now
investigating the coordination chemistry of related ligands to
form complex metallosupramolecular assemblies.
EXPERIMENTAL SECTION
■
1H NMR (400 MHz, DMSO-d6) δ = 9.39 (s, 2 H), 9.05 (d, J = 4.8
Hz, 2 H), 7.70 (t, J = 4.8 Hz, 1 H) ppm; 13C NMR (101 MHz,
DMSO-d6) δ = 164.8, 164.6, 162.0, 158.6, 158.0, 124.3, 122.2 ppm;
HRMS (TOF ES-, m/z) Calcd for C9H5N4O2 [M − H]−: 201.0413.
Found: 201.0415; Anal. Calcd for C9H7N4O2.5 (M+0.5H2O): C,
51.19; H, 3.34; N, 26.53. Found: C, 51.17; H, 3.36; N, 26.24; melting
point > 260 °C.
General Remarks. All reagents were purchased from Sigma-
Aldrich or AK Scientific and used without further purification. 4-
Tritylaniline was synthesized according to a literature procedure.31 1H
and 13C NMR spectra were recorded on a Bruker AV-300 or AV-400
spectrometer and referenced to residual solvent signals. 13C NMR
spectra were recorded using a proton decoupled pulse sequence.
Electrospray ionization mass spectra (ESI-MS) were obtained on a
Waters/Micromass LCT-TOF instrument. Melting points were
recorded on a Stanford Research Systems Digimelt. Elemental analyses
were performed at the UBC Microanalytical Services Laboratory.
PXRD patterns were collected on a Bruker D8 Discover diffractometer
at room temperature. Single-crystal X-ray data were collected on a
Bruker APEX DUO diffractometer using graphite monochromated Mo
Kα radiation (λ = 0.71073 Å). All data were collected at 90 K to a
resolution of 0.77 Å. Raw frame data (including data reduction,
interframe scaling, unit cell refinement, and absorption corrections) for
all structures were processed using APEX2.32 Structures were solved
using SUPERFLIP33 and refined using full-matrix least-squares on F2
within the CRYSTALS suite.34 All non-hydrogen atoms were refined
with anisotropic displacement parameters. Hydrogen atoms were
generally visible in the Fourier difference map and were initially refined
with restraints on bond lengths and angles, after which the positions
were used as the basis for a riding model.35 The structure of
{[Ag(L3)(H2O)0.5]PF6}n is of relatively low quality and so is provided
as an indication of structural connectivity only; in this structure it was
not possible to resolve an area of diffuse electron density (believed to
arise from disordered solvent molecules), and so PLATON-SQUEEZE
was used to account for this electron density in the model.36 Individual
structures are shown in more detail in the CIFs, which have been
deposited with the CCDC (CCDC numbers: 1586467−1586475).
Synthesis of Ligands. Compound 2 was synthesized using a
reported procedure and used without further purification.37 1 had been
reported previously, but we developed a new synthesis that does not
involve the use of ammonia.38
Preparation of Bipyrimidine-amide-C6 (L1). Compound 4 (202
mg, 1.0 mmol), HOBt (203 mg, 1.5 mmol), EDCI·HCl (287 mg, 1.5
mmol), dimethylacetamide (6 mL), and hexylamine (140 μL, 1.0
mmol) were combined in a round-bottomed flask. The mixture was
sonicated until all reagents had dissolved and the solution turned
yellow. The reaction was stirred at 65 °C under a nitrogen atmosphere
for 16 h. The reaction mixture was then poured into basic water (1 g of
NaHCO3, 100 mL) and extracted three times with DCM (300 mL
total). The combined organic phase was washed with water (2 × 150
mL) and dried under reduced pressure. To the yellow oil obtained, 50
mL of water was added and left in the freezer until a white precipitate
formed. The white powder was isolated using a glass frit and washed
with water (2 × 10 mL) before being dried under reduced pressure to
obtain a white precipitate, L1 (135 mg, 0.47 mmol, 47% yield).
1H NMR (300 MHz, CDCl3) δ = 9.34 (s, 2 H), 9.06 (d, J = 4.8 Hz,
2 H), 7.49 (t, J = 4.8 Hz, 1 H), 6.27 (br. s., 1 H), 3.53 (dd, J = 6.4, 13.6
Hz, 2 H), 1.77−1.63 (m, 2 H), 1.50−1.23 (m, 6 H), 0.91 (t, J = 6.9
Hz, 3 H) ppm; 13C NMR (75 MHz, CDCl3) δ = 163.3, 163.0, 161.5,
158.1, 156.8, 127.9, 121.9, 40.4, 31.3, 29.4, 26.6, 22.4, 13.9 ppm;
HRMS (TOF ES+, m/z) Calcd for C15H19N5ONa [M + Na]+
308.1487. Found 308.1483; melting point: 130−134 °C.
Preparation of Bipyrimidine-amide-C16 (L2). To compound 4
(202 mg, 1.0 mmol), HOBt (203 mg, 1.5 mmol), and EDCI·HCl (287
mg, 1.5 mmol) in dimethylacetamide (6 mL) was added hexadecyl-
amine (241 mg, 1.0 mmol). The mixture was sonicated until all
reagents had dissolved and the solution turned a faint yellow. The
reaction was stirred at 65 °C under nitrogen for 16 h then triturated in
100 mL of basic water (1 g NaHCO3), and the white precipitate was
filtered and washed with cold water. L2 was isolated as a white powder
(345 mg, 0.82 mmol, 82% yield).
Preparation of 2-Amidinopyrimidine Acetate (1). 2-Cyanopyr-
imidine (5.0 g, 48 mmol) and ammonium acetate (7.0 g, 91 mmol)
were mixed in 50 mL of methanol and heated to 80 °C for 16 h. After
being cooled down to room temperature, the yellow solution
containing a pale precipitate was taken to dryness under reduced
pressure. The solid was washed with a small amount of cold methanol
to give pure 2-amidinopyrimidine acetate as a white solid (3.5 g, 19
mmol, 40% yield).
1H NMR (300 MHz, CDCl3) δ = 9.34 (s, 2 H), 9.06 (d, J = 4.9 Hz,
2 H), 7.49 (t, J = 4.9 Hz, 1 H), 6.26 (t, J = 4.9 Hz, 1 H), 3.53 (dd, J =
7.2, 13.1 Hz, 2 H), 1.73−1.66 (m, 2 H), 1.38 (br. s., 2 H), 1.26 (br. m.,
24 H), 0.89 (t, J = 6.9 Hz, 3 H) ppm; 13C NMR (75 MHz, CD3OH) δ
= 163.2, 162.8, 160.0, 159.4, 132.4, 123.7, 40.9, 33.2, 30.94, 30.91,
30.8, 30.64, 30.62, 30.4, 28.8, 27.6, 23.9, 14.6 ppm; HRMS (TOF ES+,
m/z) Calcd for C25H39N5ONa [M + Na]+ 448.3052, found 448.3058;
melting point: dec 197 °C.
1H NMR (400 MHz, D2O) δ = 8.95 (d, J = 5.0 Hz, 2 H), 7.72 (t, J
= 5.0 Hz, 1 H), 1.84 (s, 3 H) ppm; 13C NMR (101 MHz, D2O) δ =
181.4, 159.8, 158.3, 152.3, 124.8, 23.4 ppm; HRMS (ESI TOF) m/z
[M − CH3COO]+ Calcd for C5H7N4 123.0671. Found 123.0673;
Anal. calcd for C7H10N4O2: C, 46.15; H, 5.53; N, 30.75. Found: C,
46.48; H, 5.54; N, 30.71; melting point: dec > 205 °C.
Preparation of Bipyrimidine-amide-t-butylphenyl (L3). 4-tert-
Butylaniline (160 μL, 1.0 mmol) was added to a suspension of 4
(202 mg, 1.0 mmol), HOBt (203 mg, 1.5 mmol) and EDCI·HCl (287
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mg, 1.5 mmol) in dimethylacetamide (6 mL). The reaction was stirred
at 65 °C under nitrogen for 16 h, then triturated in 100 mL basic water
(1 g NaHCO3), the white precipitate was filtered and washed with
cold water. L3 was isolated as a white powder (280 mg, 0.84 mmol,
84% yield).
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
1H NMR (400 MHz,CDCl3) δ = 9.49 (s, 2 H), 9.04 (d, J = 5.1 Hz,
2 H), 8.29 (br. s., 1 H), 7.59 (d, J = 7.6 Hz, 2 H), 7.48 (t, J = 4.8 Hz, 1
H), 7.41 (d, J = 8.9 Hz, 2 H), 1.33 (s, 9 H) ppm; 13C NMR (75 MHz,
CDCl3) δ = 163.5, 161.4, 161.2, 158.1, 157.0, 148.6, 134.4, 128.4,
126.0, 122.0, 120.4, 34.5, 31.3 ppm; HRMS (TOF ES+, m/z) Calcd
for C19H20N5O [M + H]+ 334.1670, found 334.1668; anal. calcd for
C19H19N5O: C, 68.45; H, 5.74; N, 21.01. Found: C, 68.19; H, 5.76; N,
20.74; melting point > 260 °C.
*Dr. Mark MacLachlan, Department of Chemistry, University
of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1,
Canada. E-mail: mmaclach@chem.ubc.ca.
ORCID
Nicholas G. White: 0000-0003-2975-0887
Mark J. MacLachlan: 0000-0002-3546-7132
Preparation of Bipyrimidine-amide-tritylphenyl (L4). Compound
4 (202 mg, 1.0 mmol), HOBt (203 mg, 1.5 mmol), EDCI·HCl (287
mg, 1.5 mmol), 6 mL of dimethylacetamide, and 4-trityl aniline (335
mg, 1.0 mmol) were combined in a round-bottomed flask. The
mixture was sonicated until all reagents had dissolved and the solution
turned gray. The reaction was stirred at 65 °C under a nitrogen
atmosphere for 16 h. The product was triturated with 100 mL of basic
water (1 g NaHCO3), the off-gray precipitate was filtered and washed
with cold water. L4 was isolated as a powder (317 mg, 0.61 mmol,
61% yield).
Funding
Natural Sciences and Engineering Research Council (NSERC)
of Canada; Killam Trust.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank NSERC for funding (Discovery Grant, Scholarship to
G.B.H.) and the Killam Trust for a Postdoctoral Fellowship for
NGW. G.B.H. would like to thank Veronica Carta for her help
with SCXRD data acquisition of one structure.
1H NMR (400 MHz, CD3CN) δ = 9.37 (s, 2 H), 9.02 (s, 1 H), 8.99
(d, J = 5.1 Hz, 2 H), 7.66 (d, J = 8.9 Hz, 2 H), 7.55 (t, J = 5.1 Hz, 1
H), 7.33−7.18 (m, 17 H) ppm; HRMS (TOF ES+, m/z) Calcd for
C34H25N5ONa [M + Na]+ 542.1957. Found 542.1949; melting point >
260 °C.
REFERENCES
■
Preparation of Single Crystals of Silver Coordination Polymers.
Typically, 5 mg of ligand and at least 3 equiv of silver triflate or
hexafluorophosphate were dissolved in 5 mL of warm acetonitrile. The
solution was filtered through glass wool and left to stand until yellow
needles of a suitable size could be observed. In the case of L4, it was
found that 5 mL of 50/50 v/v ethanol/acetonitrile mixture was
required to produce crystals of size suitable for SCXRD.
(1) Steel, P. J. Aromatic Nitrogen Heterocycles as Bridging Ligands; a
Survey. Coord. Chem. Rev. 1990, 106, 227−265.
(2) Creutz, C.; Taube, H. Direct Approach to Measuring the Franck-
Condon Barrier to Electron Transfer between Metal Ions. J. Am. Chem.
Soc. 1969, 91, 3988−3989.
(3) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe,
M.; Yaghi, O. M. Systematic Design of Pore Size and Functionality in
Isoreticular MOFs and Their Application in Methane Storage. Science
2002, 295, 469−472.
(4) Klingele, J.; Dechert, S.; Meyer, F. Polynuclear Transition Metal
Complexes of Metal···metal-Bridging Compartmental Pyrazolate
Ligands. Coord. Chem. Rev. 2009, 253, 2698−2741.
(5) Liu, Y. Y.; Ma, J. F.; Yang, J.; Su, Z. M. Syntheses and
Characterization of Six Coordination Polymers of Zinc(II) and
Cobalt(II) with 1,3,5-Benzenetricarboxylate Anion and Bis(imidazole)
Ligands. Inorg. Chem. 2007, 46, 3027−3037.
Preparation of {[Ag(L3)CH3CN]OTf}n. Silver triflate (150 mg, 0.60
mmol), and ligand L3 (66 mg, 0.20 mmol), were dissolved in 25 mL of
boiling acetonitrile. The solution was filtered through glass wool. The
solution was let to stand for 1 week at room temperature as a yellow
sparkly precipitate formed. The crystalline precipitate was filtered and
dried to obtain the coordination polymer (72 mg, 0.11 mmol, 55%
yield). Anal. calcd for C22H22N6O4 AgSF3: C, 41.85; H, 3.51; N, 13.31;
S, 5.04. Found: C, 41.60; H, 3.49; N, 13.01; S, 4.84. FT-IR 1678 s
(amide CO), 1238 vs, 1156 s, 1026 vs cm−1.
Preparation of {[Ag(L4)2CH3CN]OTf·CH3CN}. Silver triflate (150
mg, 0.60 mmol), and ligand L4 (52 mg, 0.20 mmol), were dissolved in
25 mL of boiling acetonitrile. The solution was filtered through glass
wool. The solution was let to stand for 1 week at room temperature as
a yellow sparkly precipitate formed. The crystalline precipitate was
filtered and dried to obtain the discrete complex (38 mg, 0.028 mmol,
28% yield). Anal. Calcd for C73H56N12O5 AgSF3: C, 63.62; H, 4.10; N,
12.20; S, 2.33. Found: C, 61.89; H, 3.81; N, 10.41; S, 2.69. FT-IR 1663
s (amide CO), 1282 s, 1223 s, 1023 s, cm−1.
(6) Sun, Y.-G.; Li, J.; You, J.; Guo, Y.; Xiong, G.; Ren, B.-Y.; You, L.-
X.; Ding, F.; Wang, S.-J.; Verpoort, F.; Dragutan, I.; Dragutan, V.
Bis(imidazole) Coordination Polymers Controlled by Oxalate as an
Auxiliary Ligand. J. Coord. Chem. 2015, 68, 1199−1212.
(7) Arıcı, M.; Yesi̧ lel, O. Z.; Tas,̧ M. Coordination Polymers
Assembled From 3,3′,5,5′-Azobenzenetetracarboxylic Acid and Differ-
ent Bis(imidazole) Ligands with Varying Flexibility. Cryst. Growth Des.
2015, 15, 3024−3031.
(8) Masciocchi, N.; Ardizzoia, G. A.; LaMonica, G.; Maspero, A.;
Galli, S.; Sironi, A. Metal Imidazolato Complexes: Synthesis,
Characterization, and X-Ray Powder Diffraction Studies of Group 10
Coordination Polymers. Inorg. Chem. 2001, 40, 6983−6989.
(9) Chen, M.; Bai, Z.-S.; Liu, Q.; Okamura, T.; Lu, Y.; Sun, W.-Y.
Coordination Polymers with Mixed 4,4′-Bipyridine-2,2′,6, 6′-Tetra-
carboxylate and Imidazole-Containing Ligands: Synthesis, Structure
and Properties. CrystEngComm 2012, 14, 8642.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.cgd.7b01657.
Crystal data and structure refinement as well as
structures of the ligands, their IR and NMR spectra,
and Raman and IR spectra of selected complexes (PDF)
(10) Hui, J. K. H.; MacLachlan, M. J. Metal-Containing Nanofibers
via Coordination Chemistry. Coord. Chem. Rev. 2010, 254, 2363−
2390.
(11) Grondin, P.; Siretanu, D.; Roubeau, O.; Achard, M. F.; Clerac,
R. Liquid-Crystalline zinc(II) and iron(II) Alkyltriazoles One-Dimen-
sional Coordination Polymers. Inorg. Chem. 2012, 51, 5417−5426.
(12) Chisholm, M. H. One-Dimensional Polymers and Mesogens
Incorporating Multiple Bonds between Metal Atoms. Acc. Chem. Res.
2000, 33, 53−61.
Accession Codes
CCDC 1586467−1586475 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
F
DOI: 10.1021/acs.cgd.7b01657
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
(13) Rusjan, M.; Donnio, B.; Guillon, D.; Cukiernik, F. D. Liquid-
Crystalline Materials Based on Rhodium Carboxylate Coordination
Polymers: Synthesis, Characterization and Mesomorphic Properties of
Tetra(alkoxybenzoato)dirhodium(II) Complexes and Their Pyrazine
Adducts. Chem. Mater. 2002, 14, 1564−1575.
(14) Su, P. Y. S.; Hsu, S. J.; Tseng, J. C. W.; Hsu, H. F.; Wang, W. J.;
Lin, I. J. B. Polynuclear Silver(I) Triazole Complexes: Ion Conduction
and Nanowire Formation in the Mesophase. Chem. - Eur. J. 2016, 22,
323−330.
(15) Wang, C. C.; Kuo, C. T.; Chou, P. T.; Lee, G. H. Rhodizonate
Metal Complexes with a 2D Chairlike M6 Metal-Organic Framework.
Angew. Chem., Int. Ed. 2004, 43, 4507−4510.
(31) Witten, B.; Reid, E. E. P-Aminotetraphenylmethane. Org. Synth.
1950, 30, 5.
(32) Apex2; Bruker AXS Inc: Madison, Wisconsin, USA, 2007.
(33) Palatinus, L.; Chapuis, G. SUPERFLIP − a Computer Program
for the Solution of Crystal Structures by Charge Flipping in Arbitrary
Dimensions. J. Appl. Crystallogr. 2007, 40, 786−790.
(34) Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.;
Watkin, D. J. CRYSTALS Version 12: Software for Guided Crystal
Structure Analysis. J. Appl. Crystallogr. 2003, 36, 1487−1487.
(35) Cooper, R. I.; Thompson, A. L.; Watkin, D. J. CRYSTALS
Enhancements: Dealing with Hydrogen Atoms in Refinement. J. Appl.
Crystallogr. 2010, 43, 1100−1107.
(36) Spek, A. L. PLATON SQUEEZE: A Tool for the Calculation of
the Disordered Solvent Contribution to the Calculated Structure
Factors. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 9−18.
(37) Allin, S. M.; Barton, W. R. S.; Bowman, W. R.; Bridge, E.;
Elsegood, M. R. J.; McInally, T.; McKee, V. Bu3SnH-Mediated Radical
Cyclisation onto Azoles. Tetrahedron 2008, 64, 7745−7758.
(38) Padalkar, V. S.; Patil, V. S.; Sekar, N. Synthesis and
Characterization of Novel 2, 2’-Bipyrimidine Fluorescent Derivative
for Protein Binding. Chem. Cent. J. 2011, 5, 72−79.
(16) Beauchamp, D. A.; Loeb, S. J. Coordination Polymers with 4,4’-
Bipyrimidine. Using a Combination of Endo- and Exodentate Donors
to Build a One-Dimensional Ag(I) Ladder and a Heterometallic
Co(II)Ag(I)2 Network. Dalton Trans. 2007, 42, 4760−4762.
́ ́
(17) Fabelo, O.; Pasan, J.; Lloret, F.; Julve, M.; Ruiz-Perez, C. 1,2,4,5-
Benzenetetracarboxylate- and 2,2′-Bipyrimidine-Containing Cobalt(II)
Coordination Polymers: Preparation, Crystal Structure, and Magnetic
Properties. Inorg. Chem. 2008, 47, 3568−3576.
́ ̀
(18) Zucchi, G.; Thuery, P.; Riviere, E.; Ephritikhine, M. Europium-
(II) Compounds: Simple Synthesis of a Molecular Complex in Water
and Coordination Polymers with 2,2′-Bipyrimidine-Mediated Ferro-
magnetic Interactions. Chem. Commun. 2010, 46, 9143.
(19) Maekawa, M.; Tominaga, T.; Sugimoto, K.; Okubo, T.; Kuroda-
Sowa, T.; Munakata, M.; Kitagawa, S. Framework Dimensionality of
Copper(I) Coordination Polymers of 4,4′-Bipyrimidine Controlled by
Anions and Solvents. CrystEngComm 2012, 14, 1345−1353.
(20) Pointillart, F.; Boubekeur, K.; Herson, P.; Train, C. Barium
One-Dimensional Coordination Polymers from Barium β-Diketonates
and 2,2′-Bipyrimidine Derivatives. CrystEngComm 2010, 12, 3430.
(21) Wei, K. J.; Ni, J.; Gao, J.; Liu, Y.; Liu, Q. L. Self-Assembly of
−
silver(I) Coordination Polymers from AgX (X = BF4 −, ClO4
,
−
CF3COO−, and SO3CF3 ) and a Rigid Bent 3,6-Dicyano-9-Phenyl-
carbazole Ligand: The Templating Effect of Anions. Eur. J. Inorg.
Chem. 2007, 2007, 3868−3880.
(22) He, X.; Lu, C. Z.; Wu, C. De; Chen, L. J. A Series of One- to
Three-Dimensional Copper Coordination Polymers Based on N-
Heterocyclic Ligands. Eur. J. Inorg. Chem. 2006, 2006, 2491−2503.
(23) Kaes, C.; Katz, A.; Hosseini, M. W. Bipyridine: The Most
Widely Used Ligand. A Review of Molecules Comprising at Least Two
2,2′-Bipyridine Units. Chem. Rev. 2000, 100, 3553−3590.
(24) Wagner, S.; Kisslinger, F.; Ballmann, S.; Schramm, F.;
Chandrasekar, R.; Bodenstein, T.; Fuhr, O.; Secker, D.; Fink, K.;
Ruben, M.; Weber, H. B. Switching of a Coupled Spin Pair in a Single-
Molecule Junction. Nat. Nanotechnol. 2013, 8, 575−579.
(25) Aldous, S. C.; Fennie, M. W.; Jiang, J. Z.; John, S.; Mu, L.;
Pedgrift, B.; Pribish, J. R.; Rauckman, B.; Sabol, J. S.; Stoklosa, G. T.;
Thurairatnam, S.; Vandeusen, C. L. Pyrimidine Hydrazide Compounds
as PGDS Inhibitors and Their Preparation, Pharmaceutical Compo-
sitions and Use in the Treatment of Diseases. WO 2008121670, 2008.
(26) Chen, C. L.; Kang, B. S.; Su, C. Y. Recent Advances in
Supramolecular Design and Assembly of Silver(I) Coordination
Polymers. Aust. J. Chem. 2006, 59, 3−18.
(27) Fromm, K. M. Silver Coordination Compounds with
Antimicrobial Properties. Appl. Organomet. Chem. 2013, 27, 683−687.
(28) Paul, M.; Sarkar, K.; Dastidar, P. Metallogels Derived from Silver
Coordination Polymers of C3-Symmetric Tris(pyridylamide) Tripodal
Ligands: Synthesis of Ag Nanoparticles and Catalysis. Chem. - Eur. J.
2015, 21, 255−268.
(29) Massoud, A. A.; Langer, V.; Gohar, Y. M.; Abu-Youssef, M. A.
M.; Janis, J.; Ohrstrom, L. 2D Bipyrimidine Silver(I) Nitrate:
Synthesis, X-Ray Structure, Solution Chemistry and Anti-Microbial
Activity. Inorg. Chem. Commun. 2011, 14, 550−553.
(30) Pointillart, F.; Herson, P.; Boubekeur, K.; Train, C. Square-
Planar and Trigonal Prismatic silver(I) in Bipyrimidine and Oxalate
Bridged Tetranuclear Complexes and One-Dimensional Compounds:
Synthesis and Crystal Structures. Inorg. Chim. Acta 2008, 361, 373−
379.
G
DOI: 10.1021/acs.cgd.7b01657
Cryst. Growth Des. XXXX, XXX, XXX−XXX