Anion and Cation Effects on Anion-Templated Assembly of Tetrahydroxytriptycene

Article abstract of DOI:10.1021/acs.cgd.5b01342

A tetrahydroxytriptycene ligand 1 assembles through O-H···anion hydrogen bonds into a range of different structures. With tetrabutylammonium bromide, 1 forms a stable nanotube structure that is supported by O-H···anion hydrogen bonds, but its space is occupied by the large cation. In an effort to produce the nanotubes with different cations and anions, 1 was crystallized with different salts. The reaction of 1 with tetraethylammonium bromide gives a 2D net structure, while 1 and tetrapropylammonium bromide give a discrete 1:2 complex. Attempting to co-crystallize 1 and tetramethylammonium bromide gave crystals of an oxidized quinone form of the ligand. When 1 was crystallized with tetrabutylammonium terephthalate, two different one-dimensional anion coordination polymers were obtained, depending on the crystallization solvent: acetonitrile gave a zigzag polymer, while methanol gave a linear structure. In both cases, the tetrabutylammonium cations fill the gaps between the 1D polymers, giving a layered 2D morphology. The wide range of architectures prepared from a relatively simple ligand illustrates the potential utility of O-H···anion interactions for constructing solid-state materials.

Full text of DOI:10.1021/acs.cgd.5b01342

Article
pubs.acs.org/crystal
Anion and Cation Effects on Anion-Templated Assembly of
Tetrahydroxytriptycene
Nicholas G. White and Mark J. MacLachlan*
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
S
* Supporting Information
ABSTRACT: A tetrahydroxytriptycene ligand 1 assembles through O−H···
anion hydrogen bonds into a range of different structures. With tetrabuty-
lammonium bromide, 1 forms a stable nanotube structure that is supported by
O−H···anion hydrogen bonds, but its space is occupied by the large cation. In an
effort to produce the nanotubes with different cations and anions, 1 was
crystallized with different salts. The reaction of 1 with tetraethylammonium
bromide gives a 2D net structure, while 1 and tetrapropylammonium bromide
give a discrete 1:2 complex. Attempting to co-crystallize 1 and tetramethylammonium bromide gave crystals of an oxidized
quinone form of the ligand. When 1 was crystallized with tetrabutylammonium terephthalate, two different one-dimensional
anion coordination polymers were obtained, depending on the crystallization solvent: acetonitrile gave a zigzag polymer, while
methanol gave a linear structure. In both cases, the tetrabutylammonium cations fill the gaps between the 1D polymers, giving a
layered 2D morphology. The wide range of architectures prepared from a relatively simple ligand illustrates the potential utility of
O−H···anion interactions for constructing solid-state materials.
structure, as its rigid propeller shape generates large intra-
molecular free volume (IMFV).59,60 This property of triptycene
has been exploited in the pursuit of porous polymers,61−64
coordination polymers,65−68 and porous molecules.69−72 Using
this approach, we recently reported that the triptycene-based
ligand 1 containing four phenolic O−H groups73 assembles
with bromide anions to give hexagonal nanotubes with the
formula [1·(TBA·Br)2]n via O−H···Br− hydrogen bonding
(TBA = tetrabutylammonium cation, Figure 1).74 Using other
INTRODUCTION
■
Research into the supramolecular chemistry of anions1,2 has
tended to focus on their behavior in solution, for example, in
the study of synthetic hosts3−7 and transmembrane transporters
for these species.8−11 Typically these solution-state systems
have used hydrogen bonds to interact with the anion of
interest,12−19 although recently halogen bonding has been
developed as a potent alternative to hydrogen bonding.20−24
O−H hydrogen-bond donors have received little attention,
despite such interactions being important in biological anion
recognition processes.25−27 Nevertheless, key studies by the
groups of Sessler,28 Smith,29 and Gale30 have shown that
aromatic or benzylic alcohols can be effective anion receptors.
Recently Wang, Kass, and co-workers have demonstrated that
flexible aliphatic polyols also exhibit high chloride anion
binding affinities in polar organic solvents.31−35
In contrast to metal cations,36 which have been employed to
prepare a range of complex materials including cages,37,38
interlocked structures,39,40 and framework materials,41,42 the
use of anions to template the formation of self-assembled
supramolecular systems remains underexplored. Pioneering
studies by the groups of Wu43,44 and Kruger and
Gunnlaugsson45 used phosphate or sulfate to form anion-
templated cages. A handful of helicates46−49 and other
polymeric structures50−57 have also been prepared using this
methodologyin all cases, these structures are held together
by N−H···anion hydrogen bonds. Recently, we demonstrated
that O−H···anion hydrogen bonds could be used instead of N−
H hydrogen bonds to assemble supramolecular polymers.58
We were interested in demonstrating the use of O−H···anion
hydrogen bonding to form stable porous materials. We selected
triptycene as a component that would help to create a porous
Figure 1. Assembly of 1 and TBA·Br to give solid-state hexagonal
nanotubes.74
−
−
anions (Cl−, I−, NO3 , or HSO4 ) did not give crystalline
products. The nanotubes could be prepared in bulk, and
remarkably, can withstand vacuum, heat, or water without loss
of the nanotube structure.
In this work, we extend our investigation of these interesting
anion-templated materials by investigating the interaction of 1
with other bromide-containing organic salts. Specifically we
Received: September 16, 2015
Revised: October 5, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
were interested to see if we can retain the nanotube structure,
while reducing the size of the countercation, and in so doing
increase the porosity of the anion-templated assemblies. We
also study the assembly of 1 and the divalent anion,
terephthalate, to form anion-templated polymers.
Crystallization of 1 with “Large” Tetraalkylammonium
Salts. Although our primary motivation for this study was to
incorporate smaller cations into the nanotube architectures to
make more porous structures, we also investigated the
crystallization of 1 with larger tetraalkylammonium bromide
salts. However, despite several attempts, we were unable to co-
crystallize 1 with tetrapentylammonium, tetrahexylammonium,
tetraoctylammonium, or hexadecyltrimethylammonium bro-
mide. For each cation, diethyl ether vapor was diffused into a
1:2 stoichiometric mixture of 1 and the salt in three different
solvents (dichloromethane,85 acetone, or acetonitrile), but this
gave only oils, or in the case of hexadecyltrimethylammonium
bromide, crystals of the tetraalkylammonium salt.86
Crystallization of 1 with TPA·Br. Vapor diffusion of diethyl
ether into a 1:2 mixture of 1 and TPA·Br in either
dichloromethane,85 acetone, or acetonitrile gave single crystals.
In all cases, these crystals had very similar unit cells, and a full
data collection was undertaken on the crystals grown from
acetonitrile. The single crystal X-ray diffraction (SCXRD) data
revealed that a discrete 1:2 complex was formed, [1·(TPA·Br)2]
(Figure 2). Repeating the crystallization but using a 1:1 ratio of
1 and TPA·Br gave crystals with the same unit cell as [1·(TPA·
Br)2].
RESULTS AND DISCUSSION
■
Effect of Cations. Background. It is known that in certain
cases, the choice of countercation can greatly affect the apparent
anion association strength measured in solution.75 This is
particularly the case when association constants are measured
in relatively nonpolar solvents such as dichloromethane or
chloroform, as in these solvents tetraalkylammonium anion
salts often remain ion-paired, reducing the amount of anion
available for binding.76 In other cases, the cation may genuinely
affect anion association affinity, for example, by binding to the
receptor and modulating the recognition in some way.75,77
It is well-established that changing the counteranion in a
transition metal-templated system can dramatically influence
the structure formed, and a number of elegant metal-
losupramolecular assemblies have been prepared in this
manner.78−80 In contrast, the effect of countercation on
anion-templated assemblies has received almost no attention.
Maeda and co-workers have elegantly demonstrated that
varying the cation can affect the gross structure and properties
of “charge-by-charge” assemblies consisting of a negatively
charged planar anion·receptor complex and noncoordinating
cations.81,82 In these systems, while the anion···receptor
interactions appear to remain unchanged on varying the
countercation, the interactions between the cation and the
planar anion·receptor complex as well as the ability of the
cations to pack efficiently with the host−guest complex cause
dramatic changes in the mesoscale properties of the system.
Solution Studies. Before studying the effect of cations on the
solid-state anion-templated structures formed from 1, we were
interested to see if changing the countercation had an influence
on the solution binding of bromide anion to 1. The binding of
TEA·Br and TPA·Br to 1 was studied in the polar organic
solvent CD3CN, to allow comparison with previously reported
data for TBA·Br. As shown in Table 1, there is very little
Both O−H groups point toward a single Br− and form short,
linear O−H···Br− hydrogen bonds (∠O−H···Br: 174 and
175°). H···Br− distances are 2.35 and 2.40 Å, which is 77−78%
of the sum of the van der Waals radii (%vdWH,Br).87,88 In the
previously reported nanotube structure,74 the O−H groups
point to the sides facilitating the polymeric structure and are of
comparable length (72−83%vdWH,Br).74
Each bromide anion in [1·(TPA·Br)2] is enclosed in a
“pocket” composed of TPA cations, although no significant
close contacts are observed between the cations and anion
(closest contact, H···Br− = 2.99 Å, 98%vdWH,Br). Several close
contacts are observed between the hydroxyl oxygen atoms of 1
and TPA cation C−H groups (H···Br: 2.59−2.95 Å, 85−96%
vdWH,Br), suggesting the presence of weak hydrogen bonds in
the solid state.
Crystallization of 1 with TEA·Br. Vapor diffusion of diethyl
ether into a 1:2 stoichiometric mixture of 1 and TEA·Br in
acetonitrile, methanol, or a chloroform/acetone/methanol
mixture gave crystals with similar unit cells.89 A full data
collection was undertaken on the crystals grown from
acetonitrile, revealing the formation of a 2D net structure
containing a 2:3 ratio of 1:TEA·Br, i.e., [1·(TEA·Br)1.5]n
(Figure 3). Using 1.5, 2.0, or 2.5 equiv of TEA·Br all gave
crystals with unit cells consistent with that of [1·(TEA·Br)1.5]n.
The asymmetric unit cell contains one molecule of 1, and one
and a half TEA cations and bromide anions. Both TEA cations
exhibit positional disorder, with one disordered over a site of
symmetry. While its identity was apparent, the TEA cation on
the symmetry site could not be sensibly modeled, and so
PLATON-SQUEEZE was used to include this electron density
in the refinement. In order to try and model powder X-ray
diffraction data (PXRD, vide infra), a crude refinement of this
disordered cation was attempted, but this refinement is of low
quality; these refinements are discussed in more detail in the
Supporting Information.
Table 1. Association Constants and Free Energies of Binding
of Tetraalkylammonium Salts to 1
ab
Ka (M−1
,
ac
Ka (M−1
,
b
c
salt
)
)
ΔG (kJ mol−1
)
ΔG (kJ mol−1
)
TEA·Br
TPA·Br
TBA·Br
76(2)
68(1)
85(5)
82(2)
71(1)
92(3)
−10.7
−10.4
−11.0
−10.9
−10.6
−11.2
a
Estimated standard errors of fitting Ka are given in parentheses. These
are the errors in the fitting of the curve and are an approximate
measure of the random error in the data. They do not account for
systematic error (such as inaccuracies in the quantities of reagents
measured out, or the temperature of the NMR spectrometer), and as
b
such the true uncertainty is probably substantially larger. Fit with
c
WinEQNMR program.83 Fit with fittingprogram.84
difference between the association constants recorded for the
three different salts, suggesting little cation−anion pairing in
the competitive solvent used. Notably, binding is modest in all
cases; the highest association constant calculated is 92 M−1,
which implies that only about 14% of the bromide anions in a
1:1 mixture of 1 and TBA·Br would be bound to a receptor at
the concentrations used for the binding studies, 2.0 mM.
As with [1·(TPA·Br)2], the structure of [1·(TEA·Br)1.5]n is
held together by O−H···Br− hydrogen bonds, which in this
structure vary significantly in length (H···Br− = 2.36−2.76 Å,
77−90%vdWH,Br). One end of 1 has both O−H hydrogen
atoms pointing sideways, while at the other end, one O−H
B
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Figure 2. Structure of [1·(TPA·Br)2] determined by SCXRD. Most hydrogen atoms are omitted for clarity.
Figure 3. Structure of [1·(TEA·Br)1.5]n determined by SCXRD. TEA cations and most hydrogen atoms are omitted for clarity.
group points sideways and one forward. While analysis is
complicated due to the disorder of the TEA cations, it does
appear that at least one position of one of the disordered
cations engages in a moderately short C−H···O hydrogen bond
with a phenolic oxygen atom from 1.
Bulk Synthesis of [1·(TEA·Br)1.5]n and [1·(TPA·Br)2]. The
anion-templated structures [1·(TEA·Br)1.5]n and [1·(TPA·
Br)2] could be prepared in bulk by simply dissolving the
appropriate ratio of 1 and tetraalkylammonium salt in CH3CN
and subjecting these solutions to diethyl ether vapor diffusion.
After thorough drying in vacuo, this gave [1·(TEA·Br)1.5]n and
[1·(TPA·Br)2] as large single crystals in 62% and 72% yield,
respectively. The products were characterized by 1H NMR and
IR spectroscopies, as well as elemental, thermogravimetric, and
melting point analysis.
PXRD. PXRD was used to determine whether the structure
Figure 4. Comparison of observed and simulated PXRD traces for [1·
(TEA·Br)1.5]n and [1·(TPA·Br)2].
of the bulk products was consistent with that determined by
SCXRD. Figure 4 shows the recorded traces and the simulated
patterns based on the SCXRD data (see the Supporting
Information for further details).
significant amount of impurity with a different molecular
formula can be excluded on the basis of 1H NMR spectroscopy
and elemental analysis.
In the case of [1·(TPA·Br)2], there is excellent concordance
between the observed PXRD trace and that calculated from the
SCXRD structure. For [1·(TEA·Br)1.5]n, the agreement is not
as good, though the patterns are very similar. We postulate that
the small differences are due to the difficulty of adequately
modeling the two disordered TEA cations. While one cation
could be modeled relatively well, another is disordered over a
special position. It was extremely difficult to model this, and
effectively this species could take any of a number of positions
in this area, which would greatly affect the simulated PXRD
trace. While it is not possible to exclude the existence of a
different crystalline phase, this seems unlikely as by inspection
under a microscope all crystals have the same habit, and several
crystals gave indistinguishable unit cells. The possibility of a
Thermogravimetric Analysis. As shown in Figure 5, both [1·
(TEA·Br)1.5]n and [1·(TPA·Br)2] show high thermal stability,
with thermal decomposition commencing at approximately 240
°C for [1·(TPA·Br)2] and 280 °C for [1·(TEA·Br)1.5]n. The
relatively high stability of these molecules is perhaps surprising
given the weak interactions used to construct them, and
suggests that anion-templated materials may be stable enough
for practical applications.
Crystallization of 1 with TMA·Br. Diethyl ether vapor
diffusion into a 1:2 stoichiometric mixture of 1 and TMA·Br
gave a few dark brown crystals.90 As shown in Figure 6, the
SCXRD structure of this product does not contain any TMA·
C
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
1
yield, and its identity was confirmed by H NMR and IR
spectroscopies. Carefully layering a solution of TBA2·TP in
acetonitrile with an acetonitrile solution of 1 gave single crystals
suitable for SCXRD studies. The complex is a 1D anion
coordination polymer with a zigzag structure that is held
together by O−H···O hydrogen bonds (Figure 7).
Figure 5. Thermogravimetric analyses of [1·(TEA·Br)1.5]n and [1·
(TPA·Br)2] (10 °C/min under N2).
Figure 7. Solid-state structure of zigzag anion coordination polymer
[1·TP·(TBA)2]n as determined by SCXRD: (a) image showing zigzag
polymer composed of 1 and terephthalate anions; (b) image showing
alternating layered structure (most hydrogen atoms and acetonitrile
solvent are omitted for clarity).
Figure 6. Structure of 2 determined by SCXRD. Most hydrogen atoms
are omitted for clarity. Bond lengths are given in Å.
Br, and instead clearly shows that 1 has been partially oxidized
to give 2. In this molecule, one of the catechol rings of 1 has
been oxidized to the quinone form. This is evidenced by short
CO bond lengths [1.220(3) and 1.230(3) Å, compared with
1.366(2) and 1.368(3) Å for the catechol O−H groups] and a
wide range of C−C ring bond lengths due to the presence of
both single and double bonds.
We have previously observed that a hexahydroxytriptycene is
readily oxidized to the bis-catechol quinone form during crystal
growth.74 In that case, the ligand could be deliberately oxidized
by stirring with base in methanol. In the case of 1, we could
achieve partial oxidation by heating 1 to reflux in the presence
of base91 (KOAc), open to the air in methanol. However, even
after extended reaction times, the reaction did not proceed to
completion and a mixture of 1 and 2 was obtained.
Effect of Anions. We were unable to obtain any crystalline
material containing 1 when attempting to co-crystallize 1 with
TBA·Cl, TBA·I, TBA·HSO4, or TBA·NO3 despite using a range
of solvents and crystallization conditions.74 This is in stark
contrast to the nanotubes [1·(TBA·Br)2]n, which crystallize
readily from a wide range of solvents. We have now investigated
the assembly of 1 with terephthalate (TP) anions, to see what
the effect of using a 2− anion would be on the self-assembled
structure. We were unable to investigate the solution binding of
TP, as addition of this anion to 1 caused the O−H resonance to
disappear (no other resonances showed significant movement
upon anion addition).
The asymmetric unit cell of [1·TP·(TBA)2]n contains one
TBA cation, half a TP anion, and half a molecule each of 1 and
CH3CN. The two crystallographically independent O−H
groups form convergent hydrogen bonds to one of the
carboxylate oxygen atoms. These hydrogen bonds are very
short, H···O distances are 1.76 and 1.77 Å, 65% and 66%
vdWH,O [O···O distances = 2.611(1) and 2.583(1), ∠O−H···O
= 171 and 161°, respectively]. The other TP carboxylate
oxygen atom is not involved in significant hydrogen bonding.
The TBA cations sit between the 1D anion coordination
polymers, giving an overall 2D layered structure.
Linear Anion Coordination Polymer [1·TP·(TBA)2]n. Vapor
diffusion of diethyl ether into a solution of the bulk product [1·
TP·(TBA)2]n in methanol gave a few colorless crystals (and a
very deep purple-brown solution). SCXRD showed that these
are a linear 1D anion coordination polymer, [1·TP·(TBA)2]n
(Figure 8). The asymmetric unit cell contains half a molecule of
1, half a TP anion, and one TBA cation. A region of ill-defined
diffuse electron density believed to arise from disordered
solvent molecules could not be sensibly refined, and so
PLATON-SQUEEZE was used to include the electron density
in the refinement.
The polymer is held together by short O−H···O hydrogen
bonds between the hydroxyl groups of 1, which both point
inward. The H···O distances are 1.75 and 1.78 Å, which equates
to 64 and 66% vdWH,O, respectively [O···O distances =
2.613(2) and 2.600(2), ∠O−H···O = 170 and 159°,
respectively]. As was observed for the zigzag anion coordina-
tion polymer, the TBA cations sit between the 1D chains,
giving an overall 2D layered structure.
Zigzag Anion Coordination Polymer [1·TP·(TBA)2]n.
Dissolving 1 and TBA2·TP in acetonitrile and leaving the
mixture to stand gave a microcrystalline precipitate, which has
the formula [1·TP·(TBA)2]n. This material was isolated in 58%
D
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
Figure 8. Solid-state structure of linear anion coordination polymer [1·TP·(TBA)2]n as determined by SCXRD: (a) image showing linear polymer
composed of 1 and terephthalate anions; (b) image showing alternating layered structure (most hydrogen atoms omitted for clarity, PLATON-
SQUEEZE has been used).
We were not able to isolate this material in bulk, as a
significant amount of 1 appears to be oxidized when it is
dissolved in methanol. A methanol solution of 1 containing
TBA2·TP rapidly turns purple, and if the bulk product [1·TP·
(TBA)2]n is dissolved in CD3OD or DMSO-d6, new peaks
become visible in the 1H NMR spectrum within a few minutes,
which appear to correspond to the partially oxidized form, 2.
Interestingly, while oxidation begins within minutes, even after
2 weeks in CD3OD, complete conversion of 1 to 2 is not
observed.
hydrogen bonding in our system, metal···ligand coordination in
the case of counteranion templation.)
In the case of the anion coordination polymers prepared
from 1 and (TBA)2·TP, changing solvent caused a significant
change in the architecture of the supramolecular polymer. A
change in the hydrogen-bonding arrangement was also
observed. Notably, in both cases, the hydrogen bonds are short.
Two different effects can be considered when trying to
rationalize the formation of the various different anion-
templated products in this work: either maximizing the various
weak intermolecular forces present, or trying to form a close-
packed product. In the bromide-templated materials, there
appear to be some relatively close contacts between the
alkylammonium cations and 1; however, the disorder present in
the cations of the TEA and TBA-containing structures means
that we cannot draw firm conclusions about the impact of these
short contacts on the nature of the product formed.
DISCUSSION
■
While crystallizing 1 with smaller tetraalkylammonium bromide
salts did not allow us to isolate the desired porous nanotube
architectures, we were able to prepare other robust bulk
materials via anion-templation. Changing from TBA to TPA to
TEA results in nanotube,74 discrete, and net-like architectures,
respectively. It is surprising that varying the tetraalkylammo-
nium cation has such a profound effect on the structure and
hydrogen-bonding arrangement of the anion-templated materi-
als.
The close-packing argument may explain why we were
unable to obtain crystalline material containing alkylammonium
cations larger than TBA. However, the nanotube structure of
[1·(TBA·Br)2]n contains significant void space, yet still forms
reproducibly.
As previously discussed, Maeda and co-workers have
elegantly demonstrated that varying the cation can affect the
gross structure and properties of “charge-by-charge” assem-
blies.81,82 However, in their systems, the structural changes are
thought to arise from packing of the anion and cation rather
than the anion···receptor hydrogen-bonding arrangement. In
contrast, in the complexes containing 1, the coordination
between the host and receptor is disrupted by varying the
cation.
The solution binding data (vide supra) indicate that the
cation has a negligible influence on the solution behavior of
these systems, as would be expected for these “non-
coordinating” cations. However, on crystallization, a dramatic
structure-directing effect is observed.
These systems bear an interesting resemblance to counter-
anion-templated transition metal complexes78−80 as a signifi-
cantly weaker force (interactions between the alkylammonium
cations and 1 in our case, interactions between ligand and
anions in the case of counteranion templation) has a major
influence on product structure. This occurs even in the
presence of a stronger structure-directing synthon (O−H···Br
Taken together, we suggest that a mixture of several factors
determines the architecture of these anion-templated systems.
These factors include satisfying the O−H···anion hydrogen
bonding requirements of the ligand and anion, achieving
reasonably efficient crystal packing (minimizing void space),
and “secondary” hydrogen-bonding interactions between the
alkylammonium cation and the ligand.
CONCLUSIONS
■
Several anion-templated structures have been assembled using
O−H···Br− or O−H···terephthalate hydrogen bonds. In the
case of the bromide anion-templated architectures [1·(TEA·
Br)1.5]n and [1·(TPA·Br)2], these materials can be prepared in
bulk in good yields and display high thermal stability. When 1
was crystallized in the presence of TMA·Br in methanol,
crystals of an oxidized form of 1 were obtained. We also
observed partial oxidation of 1 beginning almost immediately
when it was dissolved in CD3OD or DMSO-d6 in the presence
of TBA2·TP. Despite this, single crystals of two different forms
of 1D anion coordination polymers could be obtained by
E
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
using full-matrix least-squares on F2 within the CRYSTALS suite.96
Unless otherwise stated, 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.97 Individual structures are
discussed in more detail in the Supporting Information. Full
crystallographic data in CIF format are provided as Supporting
Information [CCDC Numbers: 1400478−1400480 and 1418005−
1418007].
growing the crystals from two different solvents, and one of
these could be prepared in bulk in good yield.
All of the various anion-templated structures reported in this
paper (discrete complex, 2D net, different 1D anion
coordination polymers) are obtained from a relatively simple
tetrahydroxytriptycene ligand. We suggest that design and
synthesis of more complex ligands will allow the preparation of
practically useful anion-templated materials. Work toward this
goal is underway.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.cgd.5b01342.
EXPERIMENTAL SECTION
■
■
S
General Remarks. Dimethyltetrahydroxytriptycene 1 was pre-
pared as previously described.92 Tetrapentylammonium bromide was
prepared from tetrapentylammonium iodide by washing a CH2Cl2
solution of this compound repeatedly with NH4Br(aq). Tetrabutylam-
monium terephthalate was prepared from terephthalic acid and
tetrabutylammonium hydroxide in methanol/water as previously
described.93 All other reagents were bought from commercial suppliers
and used as received. Details of instrumentation are given in the
Supporting Information.
Details of instrumentation, NMR spectra and photo-
graphs of new compounds, details of SCXRD and PXRD,
and solution anion binding studies (PDF)
Full crystallographic data (CIF)
Synthesis of [1·(TEA·Br)1.5]n. Dimethyltetrahydroxytriptycene 1 (35
mg, 0.10 mmol) and TEA·Br (32 mg, 0.15 mmol) were dissolved in
acetonitrile (5 mL) and subjected to diethyl ether vapor diffusion.
Over 2−4 days, large pale brown crystals developed; these were
isolated by filtration, washed with copious diethyl ether, and
thoroughly dried in vacuo to give [1·(TEA·Br)1.5]n as pale brown
single crystals. Yield: 41 mg (0.062 mmol, 62%).
AUTHOR INFORMATION
Corresponding Author
*E-mail: mmaclach@chem.ubc.ca.
Notes
■
The authors declare no competing financial interest.
1H NMR (CD3CN, 5.0 mM, 300 MHz): 7.25−7.31 (m, 2H), 6.96−
7.02 (m, 2H), 6.85 (s, 4H), 6.72* (br. s, 4H), 3.14 (q, J = 7.3 Hz,
12H), 2.21 (s, 6H), 1.19 (apparent tt, J = 7.3 Hz, 1.8 Hz, 18H) ppm.
*Peak disappears on addition of D2O.
ACKNOWLEDGMENTS
■
The authors thank Dr. Jonathon Chong for preparing
precursors of 1, Anita Lam for collecting PXRD data, and
Debbie Le for assistance with collecting SCXRD data for [1·
(TPA·Br)2]. N.G.W. thanks the Killam Foundation for award of
a Killam Postdoctoral Research Fellowship. We thank NSERC
(Discovery Grant) for funding.
IR: ∼ 3150 cm−1 (broad, O−H stretch). EA: C 61.7, H 7.5, N 3.5%;
calc. for [1·(TEA·Br)1.5], C34H48N1.5O4Br1.5: C 61.7, H 7.3, N 3.2%.
mp 218.5−219.5 °C.
Synthesis of [1·(TPA·Br)2]. Dimethyltetrahydroxytriptycene 1 (35
mg, 0.10 mmol) and TPA·Br (53 mg, 0.20 mmol) were dissolved in
acetonitrile (5 mL) and subjected to diethyl ether vapor diffusion.
Over 2−4 days, large pale brown crystals developed; these were
isolated by filtration, washed with copious diethyl ether, and
thoroughly dried in vacuo to give [1·(TPA·Br)2] as pale brown single
crystals. Yield: 67 mg (0.072 mmol, 72%).
REFERENCES
■
(1) Evans, N. H.; Beer, P. D. Angew. Chem., Int. Ed. 2014, 53, 11716−
11754.
(2) Busschaert, N.; Caltagirone, C.; Van Rossom, W.; Gale, P. A.
Chem. Rev. 2015, 115, 8038−8155.
(3) Custelcean, R. Chem. Soc. Rev. 2014, 43, 1813−1824.
(4) Cai, J.; Sessler, J. L. Chem. Soc. Rev. 2014, 43, 6198−6213.
(5) Gale, P. A.; Caltagirone, C. Chem. Soc. Rev. 2015, 44, 4212−4227.
(6) Elmes, R. B. P.; Jolliffe, K. A. Chem. Commun. 2015, 51, 4951−
4968.
(7) Dutta, R.; Ghosh, P. Chem. Commun. 2015, 51, 9070−9084.
(8) Davis, J. T.; Gale, P. A.; Okunola, O. A.; Prados, P.; Iglesias-
́
Sanchez, J. C.; Torroba, T.; Quesada, R. Nat. Chem. 2009, 1, 138−144.
(9) Busschaert, N.; Gale, P. A. Angew. Chem., Int. Ed. 2013, 52,
1374−1382.
(10) Ko, S.-K.; Kim, S. K.; Share, A.; Lynch, V. M.; Park, J.;
Namkung, W.; van Rossom, W.; Busschaert, N.; Gale, P. A.; Sessler, J.
L.; Shin, I. Nat. Chem. 2014, 6, 885−892.
(11) Lisbjerg, M.; Valkenier, H.; Jessen, B. M.; Al-Kerdi, H.; Davis, A.
P.; Pittelkow, M. J. Am. Chem. Soc. 2015, 137, 4948−4951.
(12) Gale, P. A. Chem. Commun. 2008, 4525−4540.
(13) Kubik, S. Chem. Soc. Rev. 2009, 38, 585−605.
(14) Li, A.-F.; Wang, J.-H.; Wang, F.; Jiang, Y.-B. Chem. Soc. Rev.
2010, 39, 3729−3745.
(15) Amendola, V.; Fabbrizzi, L.; Mosca, L. Chem. Soc. Rev. 2010, 39,
3889−3915.
(16) Cai, J.; Sessler, J. L. Chem. Soc. Rev. 2014, 43, 6198−6213.
(17) Ramabhadran, R. O.; Liu, Y.; Hua, Y.; Ciardi, M.; Flood, A. H.;
Raghavachari, K. J. Am. Chem. Soc. 2014, 136, 5078−5089.
(18) Edwards, S. J.; Valkenier, H.; Busschaert, N.; Gale, P. A.; Davis,
A. P. Angew. Chem., Int. Ed. 2015, 54, 4592−4596.
1H NMR (CD3CN, 5.0 mM, 300 MHz): 7.25−7.30 (m, 2H), 6.96−
7.01 (m, 2H), 6.86* (br. s, 8H), 3.01−3.07 (m, 16H), 2.21 (s, 6H),
1.58−1.71 (m, 16H), 0.94 (t, J = 7.3 Hz, 24H) ppm.
*Peak intensity reduces on addition of D2O.
IR: ∼ 3190 cm−1 (broad, O−H stretch). EA: C 62.8, H 8.7, N 3.3%;
calc. for [1·(TPA·Br)2], C46H74N2O4Br2: C 62.9, H 8.5, N 3.2%. mp
180.0−181.0 °C.
Synthesis of [1·TP·(TBA)2]n. A solution of TBA2·TP (26 mg, 0.040
mmol) in CH3CN (2 mL) was added to a solution of 1 in CH3CN (14
mg, 0.040 mmol) in a vial. The solution was stirred briefly, then the
vial was sealed and left to stand overnight giving a sandy-colored
microcrystalline precipitate. This was isolated by filtration, washed
with CH3CN (3 × 1 mL) and CH2Cl2 (3 × 1 mL) and dried in vacuo
to give [1·TP·(TBA)2]. Yield: 23 mg (0.023 mmol, 58%).
1H NMR (CD3OD, 300 MHz): 7.95 (s, 4H), 6.77 (s, 4H), 7.20−
7.26 (m, 2H), 6.92−6.98 (m, 2H), 3.19 (t, J = 8.4 Hz, 16 H), 2.20 (s,
6H), 1.58−1.68 (m, 16H), 1.34−1.46 (m, 16H), 1.01 (J = 7.3 Hz,
24H). IR: ∼ 3000 (broad, obscured, O−H stretch), 1736 (C−O
stretch), 1366 (C−O stretch), 1229 (C−O stretch), 1217 (C−O
stretch). mp. ∼ 230 °C (dec.).
X-ray Crystallography. SCXRD data were collected on a Bruker
APEX DUO diffractometer using graphite monochromated Mo Kα
radiation (λ = 0.71073 Å) or Cu Kα radiation (λ = 1.54178 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
APEX2.94 Structures were solved using SUPERFLIP95 and refined
F
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
(19) Qiao, B.; Sengupta, A.; Liu, Y.; McDonald, K. P.; Pink, M.;
Anderson, J. R.; Raghavachari, K.; Flood, A. H. J. Am. Chem. Soc. 2015,
137, 9746−9757.
(50) Hosseini, M. W.; Ruppert, R.; Schaeffer, P.; De Cian, A.;
Kyritsakas, N.; Fischer, J. J. Chem. Soc., Chem. Commun. 1994, 2135−
2136.
(20) Beale, T. M.; Chudzinski, M. G.; Sarwar, M. G.; Taylor, M. S.
Chem. Soc. Rev. 2013, 42, 1667−1680.
(51) Brooks, S. J.; Gale, P. A.; Light, M. E. CrystEngComm 2005, 7,
586−591.
(21) Sarwar, M. G.; Dragisic,
- Eur. J. 2013, 19, 2050−2058.
(22) Langton, M. J.; Robinson, S. R.; Marques, I.; Fel
D. Nat. Chem. 2014, 6, 1039−1043.
́
B.; Dimitrijevic,
́
E.; Taylor, M. S. Chem.
(52) Chifotides, H.; Schottel, B. L.; Dunbar, K. R. Angew. Chem., Int.
Ed. 2010, 49, 7202−7207.
́
ix, V.; Beer, P.
(53) Wang, T.; Yan, X.-P. Chem. - Eur. J. 2010, 16, 4639−4649.
(54) Zhang, Z.; Kim, D. S.; Lin, C.-Y.; Zhang, H.; Lammer, A. D.;
(23) Robinson, S. R.; Mustoe, C.; White, N. G.; Brown, A.;
Thompson, A. L.; Kennepohl, P.; Beer, P. D. J. Am. Chem. Soc. 2015,
137, 499−507.
(24) Gilday, L. C.; Robinson, S. W.; Barendt, T. A.; Langton, M. J.;
Mullaney, B. R.; Beer, P. D. Chem. Rev. 2015, 115, 7118−7195.
(25) Pflugrath, J. W.; Quiocho, F. A. Nature 1985, 314, 257−260.
(26) Luecke, H.; Quiocho, F. A. Nature 1990, 347, 402−406.
(27) Dutzler, R.; Campbell, E. B.; Cadene, M.; Chait, B. T.;
MacKinnon, R. Nature 2002, 415, 287−294.
(28) Miyaji, H.; Sessler, J. L. Angew. Chem., Int. Ed. 2001, 40, 154−
157.
(29) Smith, D. K. Org. Biomol. Chem. 2003, 1, 3874−3877.
Winstanley, K. J.; Sayer, A. M.; Smith, D. K. Org. Biomol. Chem.
2006, 4, 1760−1767.
(30) Busschaert, N.; Jaramillo-Garcia, J.; Light, M. E.; Herniman, J.;
Langley, G. J.; Gale, P. A. RSC Adv. 2014, 4, 5389−5393.
(31) Shokri, A.; Schmidt, J.; Wang, X.-B.; Kass, S. R. J. Am. Chem. Soc.
2012, 134, 2094−2099.
́
Lynch, V. M.; Popov, I.; Miljanic, O. M.; Anslyn, E. V.; Sessler, J. L. J.
Am. Chem. Soc. 2015, 137, 7769−7774.
(55) Gong, H.-Y.; Rambo, B. M.; Karnas, E.; Lynch, V. M.; Sessler, J.
L. Nat. Chem. 2010, 2, 406−409.
(56) Gong, H.-Y.; Rambo, B. M.; Lynch, V. M.; Keller, K. M.; Sessler,
J. L. J. Am. Chem. Soc. 2013, 135, 6330−6337.
(57) Wang, J.; Li, S.; Yang, P.; Huang, X.; Yang, X.-J.; Wu, B.
CrystEngComm 2013, 15, 4540−4548.
(58) White, N. G.; Carta, V.; MacLachlan, M. J. Cryst. Growth Des.
2015, 15, 1540−1545.
(59) Chong, J. H.; MacLachlan, M. J. Chem. Soc. Rev. 2009, 38,
3301−3315.
(60) Ma, Y.-X.; Meng, Z.; Chen, C.-F. Synlett 2014, 26, 6−30.
(61) Yang, J.-S.; Swager, T. M. J. Am. Chem. Soc. 1998, 120, 11864−
11873.
(62) Gulam Rabbani, M.; Reich, T. E.; Kassab, R. M.; Jackson, K. T.;
El-Kaderi, H. M. Chem. Commun. 2012, 48, 1141−1143.
(63) Sekizkardes, A. K.; Islamoglu, T.; Kahveci, Z.; El-Kaderi, H. M. J.
Mater. Chem. A 2014, 2, 12492−12500.
(64) Sekizkardes, A. K.; Altarawneh, S.; Kahveci, Z.; Islamoglu, T.; El-
Kaderi, H. M. Macromolecules 2014, 47, 8328−8334.
(65) Chong, J. H.; MacLachlan, M. J. Inorg. Chem. 2006, 45, 1442−
1444.
(32) Shokri, A.; Schmidt, J.; Wang, X.-B.; Kass, S. R. J. Am. Chem. Soc.
2012, 134, 16944−16947.
(33) Shokri, A.; Wang, X.-B.; Kass, S. R. J. Am. Chem. Soc. 2013, 135,
9525−9530.
(34) Shokri, A.; Kass, S. R. Chem. Commun. 2013, 49, 11674−11676.
(35) The same authors have also recently reported a preorganized
tripodal alcohol-based anion receptor that displays strong anion
recognition through O−H···anion hydrogen bonds: Shokri, A.; Deng,
S. H. M.; Wang, X.-B.; Kass, S. R. Org. Chem. Front. 2014, 1, 54−61.
(36) Cook, T. R.; Zheng, Y.-R.; Stang, P. J. Chem. Rev. 2013, 113,
734−777.
(66) Vagin, S.; Ott, A.; Weiss, H.-C.; Karbach, A.; Volkmer, D.;
Rieger, B. Eur. J. Inorg. Chem. 2008, 2008, 2601−2609.
(67) Vagin, S. I.; Ott, A. K.; Hoffmann, S. D.; Lanzinger, D.; Rieger,
B. Chem. - Eur. J. 2009, 15, 5845−5853.
(68) Crane, A. K.; Patrick, B. O.; MacLachlan, M. J. Dalton Trans.
2013, 42, 8026−8033.
(69) Chong, J. H.; Ardakani, S. J.; Smith, K. J.; MacLachlan, M. J.
Chem. - Eur. J. 2009, 15, 11824−11828.
(37) Yoshizawa, M.; Klosterman, J. K.; Fujita, M. Angew. Chem., Int.
Ed. 2009, 48, 3418−3438.
(70) Mastalerz, M.; Oppel, I. M. Angew. Chem., Int. Ed. 2012, 51,
5252−5255.
(38) Ronson, T. K.; Zarra, S.; Black, S. P.; Nitschke, J. R. Chem.
Commun. 2013, 49, 2476−2490.
(71) Zhang, G.; Mastalerz, M. Chem. Soc. Rev. 2014, 43, 1934−1947
and references therein.
(39) Dietrich-Buchecker, C. O.; Sauvage, J.-P.; Kintzinger, J.-P.
Tetrahedron Lett. 1983, 24, 5095−5098.
(72) Taylor, R. G. D.; Carta, M.; Bezzu, C. G.; Walker, J.; Msayib, K.
J.; Kariuki, B. M.; McKeown, N. B. Org. Lett. 2014, 16, 1848−1851.
(73) Chen and co-workers have reported studies on the solid-state
assembly of hydroxy-substituted triptycenes through intermolecular
hydrogen bonding, and through hydrogen bonding to neutral 4,4′-
bipyridine: Zhang, C.; Chen, C.-F. CrystEngComm 2010, 12, 3255−
3261. Han, Y.; Jiang, Y.; Chen, C.-F. Chin. Chem. Lett. 2013, 24, 475−
478.
(74) White, N. G; MacLachlan, M. J. Chem. Sci. 2015, 6, 6245−6249.
(75) Sessler, J. L.; Gross, D. E.; Cho, W.-S.; Lynch, V. M.;
Schmidtchen, F. P.; Bates, G. W.; Light, M. E.; Gale, P. A. J. Am. Chem.
Soc. 2006, 128, 12281−12288.
(76) Alunni, S.; Pero, A.; Reichenbach, G. J. Chem. Soc., Perkin Trans.
2 1998, 1747−1750.
(40) Beves, J. E.; Blight, B. A.; Campbell, C. J.; Leigh, D. A.;
McBurney, R. T. Angew. Chem., Int. Ed. 2011, 50, 9260−9327.
(41) Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1989, 111, 5962−
5964.
(42) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M.
Science 2013, 341, 974−987.
(43) Wu, B.; Cui, F.; Lei, Y.; Li, S.; de Sousa Amadeu, N.; Janiak, C.;
Lin, Y.-J.; Weng, L.-H; Wang, Y.-Y.; Yang, X.-J. Angew. Chem., Int. Ed.
2013, 52, 5096−5100.
(44) Yang, D.; Zhao, J.; Zhao, Y.; Lei, Y.; Cao, L.; Yang, X.-J.; Davi,
M.; de Sousa Amadeu, N.; Janiak, C.; Zhang, Z.; Wang, Y.-Y.; Wu, B.
Angew. Chem., Int. Ed. 2015, 54, 8658−8661.
(45) Pandurangan, K.; Kitchen, J. A.; Blasco, S.; Boyle, E. M.;
Fitzpatrick, B.; Feeney, M.; Kruger, P. E.; Gunnlaugsson, T. Angew.
Chem., Int. Ed. 2015, 54, 4566−4570.
́
(46) Sanchez-Quesada, J.; Seel, C.; Prados, P.; de Mendoza, J. J. Am.
Chem. Soc. 1996, 118, 277−278.
(47) Haketa, Y.; Maeda, H. Chem. - Eur. J. 2011, 17, 1485−1492.
(48) Li, S.; Jia, C.; Wu, B.; Luo, Q.; Huang, X.; Yang, Z.; Li, Q.-S.;
Yang, X.-J. Angew. Chem., Int. Ed. 2011, 50, 5721−5724.
(49) Schneebeli, S. T.; Frasconi, M.; Liu, Z.; Wu, Y.; Gardner, D. M.;
Strutt, N. L.; Cheng, C.; Carmieli, R.; Wasielewski, M. R.; Stoddart, J.
F. Angew. Chem., Int. Ed. 2013, 52, 13100−13104.
(77) Hua, Y.; Ramabhadran, R. O.; Karty, J. A.; Raghavachari, K.;
Flood, A. H. Chem. Commun. 2011, 47, 5979−5981.
(78) Hasenknopf, B.; Lehn, J.-M.; Kneisel, B. O.; Baum, G.; Fenske,
D. Angew. Chem., Int. Ed. Engl. 1996, 35, 1838−1840.
(79) Hasenknopf, B.; Lehn, J.-M.; Boumediene, N.; Dupont-Gervais,
A.; Van Dorsselaer, A.; Kneisel, B.; Fenske, D. J. Am. Chem. Soc. 1997,
119, 10956−10962.
(80) Chifotides, H. T.; Dunbar, K. R. Acc. Chem. Res. 2013, 46, 894−
906.
G
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design
Article
(81) Haketa, Y.; Sasaki, S.; Ohta, N.; Masunaga, H.; Ogawa, H.;
Mizuno, N.; Araoka, F.; Takezoe, H.; Maeda, H. Angew. Chem., Int. Ed.
2010, 49, 10079−10083.
(82) Dong, B.; Terashima, Y.; Haketa, Y.; Maeda, H. Chem. - Eur. J.
2012, 18, 3460−3463.
(83) Hynes, M. J. J. Chem. Soc., Dalton Trans. 1993, 311−312.
(84) Thordarson, P. Chem. Soc. Rev. 2011, 40, 1305−1323.
(85) 1 is not soluble in dichloromethane, so 1 and tetraalkylammo-
nium bromide salts were combined in acetone, evaporated to dryness
under reduced pressure, and the resulting oil dissolved in dichloro-
methane.
(86) Crystals gave a unit cell that matched a previously-determined
structure of trimethylhexadecylammonium bromide: Prukala, W.;
Marciniec, B.; Kubicki, M. Acta Crystallogr., Sect. E: Struct. Rep. Online
2007, E63, o1464−o1466.
(87) Alvarez, S. Dalton Trans. 2013, 42, 8617−8636.
(88) For a more detailed explanation of the advantages and
disadvantages of using %vdWH,X to describe hydrogen bonding
parameters, see: White, N. G.; Serpell, C. J.; Beer, P. D. Cryst. Growth
Des. 2014, 14, 3472−3479.
(89) TEA·Br is not soluble in chlorinated solvents or acetone, so we
could not use these solvents (as we had for TPA·Br or TBA·Br).
(90) TMA·Br is not sufficiently soluble in chlorinated solvents,
acetone or acetonitrile to allow their use.
(91) Deprotonation of catechol is known to increase its tendency to
oxidize: Dei, A.; Sorace, L. Dalton Trans. 2003, 3382−3386.
(92) Zong, Q.-S.; Chen, C.-F. Org. Lett. 2006, 8, 211−214.
(93) Campanelli, A. R.; Scaramuzza, L. Acta Crystallogr., Sect. C: Cryst.
Struct. Commun. 1986, C42, 1380−1383.
(94) APEX2, 2007; Bruker AXS Inc., Madison, Wisconsin, USA.
(95) Palatinus, L.; Chapuis, G. J. Appl. Crystallogr. 2007, 40, 786−
790.
(96) Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.;
Watkin, D. J. J. Appl. Crystallogr. 2003, 36, 1487.
(97) Cooper, R. I.; Thompson, A. L.; Watkin, D. J. J. Appl. Crystallogr.
2010, 43, 1100−1107.
H
DOI: 10.1021/acs.cgd.5b01342
Cryst. Growth Des. XXXX, XXX, XXX−XXX