Protonation and Alkylation Induced Multidentate C-H···Anion Binding to Perrhenate

Article abstract of DOI:10.1021/acs.cgd.5b01524

A family of pyridyl-functionalized arylacetylene C-H hydrogen bonding (HB) receptors were synthesized and binding interactions to perrhenate (ReO₄^-) studied in the solid state. The protonation and alkylation state of the pyridine nit

Full text of DOI:10.1021/acs.cgd.5b01524

Article
pubs.acs.org/crystal
Protonation and Alkylation Induced Multidentate C−H···Anion
Binding to Perrhenate
Asia Marie S. Riel, Daniel A. Decato, and Orion B. Berryman*
Department of Chemistry and Biochemistry, University of Montana, 32 Campus Drive, Missoula, Montana 59812, United States
*
S Supporting Information
ABSTRACT: A family of pyridyl-functionalized arylacetylene C−H hydrogen
bonding (HB) receptors were synthesized and binding interactions to perrhenate
−
(
ReO ) studied in the solid state. The protonation and alkylation state of the
4
pyridine nitrogen dictate the location and denticity of the interactions. X-ray
+
−
structures of neutral 1 and singly charged 2a ·ReO4 reveal the formation of
favorable self-complementary dimers, owing to the presence of nitrogen HB
acceptor sites. Dismissal of these dimers upon elimination of nitrogen HB acceptors
on the receptor result in an array of multidentate C−H HB receptor−guest contacts.
ReO4− resulting in an array of multidentate C−H HB
INTRODUCTION
■
receptor−guest contacts.
The design and application of synthetic receptors for anions
remains a captivating and challenging area of chemistry. A
common motivation driving these efforts is the detection and
RESULTS AND DISCUSSION
■
In supramolecular chemistry the phenyl acetylene group has
been effectively employed to impart direction and rigidity.
remediation of environmentally noxious anions. Pertechnetate
10
−
(
TcO ) is a contemporary example, which has entered the
4
Rotation around the alkyne bonds allow for receptors to be
conformationally flexible and adaptable for guest species to
induce a specific host conformation. A diverse collection of
phenyl acetylene receptors exhibiting induced-fit binding
environment as a product from nuclear processing plants in the
1
99
past few decades. Technetium-99 ( Tc) becomes the mobile
−
TcO4 when oxidized in the environment making it a
particularly dangerous radioactive compound.
include the following: bis(2-anilinoethynyl) sulfonamide
−
Due to the challenges of working with TcO , perrhenate
11
4
receptors,
resorcin[4]arene cavitand-based molecular
−
(
ReO ) is often employed as a manageable surrogate with
12
4
switches, and fluorophoric alkyne-linked bis-urea chemo-
2
comparable structural and electronic characteristics. However,
both anions are elusive targets as a result of low hydration
energies and diffuse charge densities. Efforts to address these
13
sensors. Consequently, aryl C−H protons often frequent the
binding pocket of the host, yet, despite this proximity, their role
in anion binding is rarely discussed.
3
problematic features with noncovalent interactions has included
elegant hydrogen bonding (HB) systems such as aza-thioether
The receptors that we are developing incorporate both
arylacetylene and pyridine functionalities. The pyridine ring is
an appealing and established structural motif for the design of
tunable anion receptors, as the chemistry at the pyridine
4
5
macrocycles, amino-azacryptands, tripodal aminopyridinium-
6
7
based receptors, and lipophilic guanidinium receptors.
14
Additionally, the first solution and solid-state investigations o8f
nitrogen dictates HB functionality; the neutral species can
accept HBs through the nitrogen lone pair. Protonation of the
pyridine ring establishes a strong HB donor while alkylation
silences HB at this site.
bidentate halogen bonding (XB) to ReO4− were reported.
Complementing these studies, a XB receptor was recently
−
shown to extract ReO from water in a solvent extraction
4
9
process. In contrast, nontraditional C−H HB receptors are
A series of pyridine-functionalized arylacetylene-based
−
underrepresented with only one investigation of ReO
receptors demonstrate the influence of alkylation and
4
8
−
binding.
protonation when binding to ReO
4
. Receptors capable of
Herein, we report crystal structures for a family of pyridyl−-
functionalized arylacetylene C−H HB receptors where ReO4
binding is dictated by alkylation and protonation of the
receptors in the solid state. The neutral receptor forms self-
complementary dimers whereas elimination of the nitrogen HB
acceptor ensures the receptor binding pocket interacts with
accepting a HB prefer to form self-complementary dimers. As a
−
result ReO4 molecules interact with the backbone of the
Received: October 28, 2015
Revised: December 21, 2015
Published: December 22, 2015
©
2015 American Chemical Society
974
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980

Crystal Growth & Design
Article
receptor. Alkylation or protonation of the pyridine ring disrupts
dimer formation, thus permitting favorable multidentate
interactions between the receptor and ReO4 in the binding
crystallization using tetra-n-butylammonium perrhenate
+
−
(TBA ReO ). This afforded a family of pyridyl-functionalized
4
−
arylacetylene-based receptor molecules, where the electronic
nature of the pyridine ring and C−H HB ability was tuned; all
of the key crystal details and structure parameters are compiled
in Table 1.
Neutral Bis-Ethynyl Benzene Core Crystal Structure 1.
To compare structural characteristics between scaffolds, it was
pocket.
Receptor Synthesis. Three bidentate HB receptor
molecules based on a bis-ethynyl benzene core were prepared
(Scheme 1). The synthesis of pyridyl arylacetylene scaffolds 1
a
Scheme 1. Synthesis of Compounds 1, 2a, 2b, and 2c
crucial to evaluate the packing features of the neutral receptor
−
without ReO . Crystals of the unmodified scaffold (1) were
4
grown by slow evaporation of an MeCN/H O (9:1) solution of
2
1
̅
. Scaffold 1 crystallized in space group PI with two
independent molecules in the asymmetric unit as shown in
Figure 1a.
The crystal structure of 1 reveals that each receptor forms
two unique self-complementary HB dimers (Figure 1b)
between the pyridine nitrogens and the hydrogens that are
ortho to the alkynes on an adjacent pyridine. Receptors from
each dimer reside out-of-plane (blue dimer interplanar distance
of 0.279(9) Å and orange dimer interplanar distance of
0
.968(9) Å) to minimize steric interactions between benzene
and pyridyl hydrogens on independent receptors. As a result
the alkynes distort 4−5° from linearity to accommodate the C−
H···N HB. Interestingly, sheets of dimers are created by
medium strength HBs (C−H···N distances, angles of
a
Step a: 4-Iodopyridine, CuI, Pd(PPh ) Cl , DMF, DIPEA, rt, 24 h,
2%. Step b: Methyl triflate (2 equiv), DCM, rt, 24 h, 98%.
3
2
2
2
2
.5055(16) Å, 159.88(11)° and 2.4988(19) Å, 160.22(11)°)
8
that form between two self-complementary dimer systems
(Figure 2a). Parallel sheets of dimers are supported by π−π
interactions that display interplanar distances of 3.116(6) and
3.450(6) Å. The crystal lattice of 1 exhibits herringbone
and 2c have been described previously. Compound 2a was
isolated as a byproduct of the alkylation of neutral scaffold 1
15
−
(Scheme 1, step b). Finally, anion exchange of triflate (OTf )
−
with ReO4 was accomplished through vapor diffusion
Table 1
+
2a ·ReO4−
2b ·2ReO4−·H O
2+
2+
2c ·2ReO4−·2DCM
2+
−
cryst param
1
2c ·2ReO
4
2
CCDC
1433000
C H N
1433002
1433001
1433003
1028025
empirical formula
fw
C H N O Re
21 15
C H N O Re
21 18
C H Cl N O Re
24 22
C H N O Re
22 18 2 8 2
2
0
12
2
2
4
2
9
2
4
2
8
2
280.32
100(2)
0.71073
545.55
814.77
980.63
810.78
T (K)
100(2)
100(2)
100(2)
100(2)
λ (Å)
0.71073
0.71073
0.71073
0.71073
cryst size (mm)
cryst syst
space group
a (Å)
0.25 × 0.2 × 0.05
triclinic
0.35 × 0.05 × 0.02
monoclinic
C2/c
0.35 × 0.15 × 0.05
triclinic
0.3 × 0.3 × 0.04
triclinic
0.2 × 0.1 × 0.01
monoclinic
P1
̅
P1
̅
P1
̅
P2 /n
1
5.8402(5)
11.4802(10)
22.2886(19)
76.511(2)
83.385(3)
89.692(3)
1443.1(2)
4
45.388(4)
5.5199(5)
15.4046(15)
90
7.6357(4)
8.0400(4)
18.3333(9)
82.310(2)
83.902(2)
80.681(2)
1096.54(10)
2
7.6734(6)
10.7002(8)
18.7453(14)
101.0830(19)
91.6380(19)
103.1300(19)
1466.72(19)
2
15.5756(10)
7.6106(5)
19.6042(13)
90
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
95.401(4)
90
100.084(2)
90
3842.3(6)
8
2288.0(3)
4
Z
D (Mg m−3)
1.29
1.886
2.468
2.22
2.354
c
μ (mm−1)
0.077
6.355
11.087
8.659
10.623
1512
F(000)
587
2096
760
924
2
θmax (deg)
54.97
55.236
42312
61.214
55.75
56.56
no. of reflns
48397
70337
38575
40497
no. of indepen reflns
Rint
6623
4459
6731
6987
5583
0.0507
0.092
0.05
0.362
0.0706
0.0286
0.0563
1.000
R1 (I > 2σ(I))
wR2 (I > 2σ(I))
GOF
0.0532
0.0511
0.0948
1.163
0.0289
0.024
0.1261
0.0614
0.0548
1.026
1.162
1.246
max/min residual e density (e Å3)
−
0.37/-0.19
3.0/-3.5
2.88/-2.24
0.94/-0.94
2.88/-1.52
9
75
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980

Crystal Growth & Design
Article
Figure 1. (a) Asymmetric unit of neutral pyridine-functionalized
arylacetylene scaffold 1. (b) Display of two unique self-complementary
dimers of 1 (blue dimer C−H···N distance of 2.5932(19) Å and angle
of 159.12(11)°; orange dimer C−H···N distance of 2.6269(16) Å and
angle of 161.98(12)°).
Figure 2. (a) Self-complementary dimer formed by 1 (red dashed
lines) and dimers forming sheets of dimers through HB (blue dashed
lines). (b) Side view of one dimer highlighting the offset dimerization.
packing (Figure 2c), when viewed along [110], between two
independent receptor units, intersecting at 63.75(6)°.
(c) Herringbone packing displayed when viewed along [110].
The crystal structure of 1 is highlighted by C−H···N HB
dimerization, emphasizing the critical role of the pyridine
nitrogen. Dimerization and lack of charge suggests that this
−
neutral molecule is an inadequate receptor for ReO .
4
Elucidation of the neutral scaffold, however, establishes a
baseline for the investigation of the modified receptors with
−
ReO .
4
+
−
Crystal Structure of 2a ·ReO . Colorless single crystals
4
+
of the monoalkylated pyridyl arylacetelyene complex 2a ·
ReO4 suitable for X-ray diffraction were grown by vapor
−
diffusion of ether into an MeCN solution of ligand 2a and
+
−
+
−
TBA ReO . Complex 2a ·ReO crystallized in space group
4
4
−
C2/c with one singly charged receptor and one ReO4 anion
per asymmetric unit (Figure 3).
+
−
Figure 3. Asymmetric unit of monoalkylated complex 2a ·ReO .
4
Monoalkylation of the scaffold eliminates the HB accepting
ability of one nitrogen; however, dimerization similar to 1 is
(pyridinium ring rotates 10.1(3)° and neutral pyridine ring
rotates 2.5(3)°) with the center benzene ring to reduce steric
contacts between hydrogens on independent receptors in the
dimer.
conserved. The preservation of the self-complementary dimer
−
results in C−H HB interactions with ReO occurring with the
4
receptor backbone (Figure 4). Examination of the environment
−
+
−
around the anion reveals that one ReO4 accepts nine HBs
A self-complementary dimer is present in 2a ·ReO due to
4
from six different receptor molecules (distances, 2.341(6)−
the availability of a HB accepting lone pair. However, the
second pyridine nitrogen is not available in this capacity; thus,
anion−π interactions contribute to assemble these HB dimers
−
2
.741(5) Å; C−H···O angles, 126.5(5)−168.5(5)°) and one
1
6
anion-π contact. Further investigation reveals a self-
complementary dimer (C−H···N distance of 2.353(7) Å and
angle of 172.0(5)°) similar to 1; each receptor molecule sits
slightly out-of-plane (interplanar distance of 0.60(4) Å).
Additionally, both pyridine rings rotate out of planarity
+
−
in the solid state. Crystal packing of 2a ·ReO displays a
4
herringbone type pattern, similar to 1, when viewed down the
crystallographic c axis, with two independent receptors
intersecting at an angle of 55.7(4)°. Parallel sheets of dimers
9
76
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980

Crystal Growth & Design
Article
Figure 4. Complex 2a ·ReO4− formation of a self-complementary
+
dimer.
are supported by π−π-stacking interactions that display an
Figure 6. Asymmetric unit of monoalkylated/monoprotonated
interplanar distance of 3.18(3) Å. In contrast to 1, the crystal
2+
−
−
complex 2b ·2ReO ·H O displaying a tridentate C−H HB to
4 2
packing is altered due to the presence of ReO in this
−
4
ReO4 in the receptor binding pocket.
+
−
crystalthe lattice of 2a ·ReO is held together by C−H HB,
4
π−π stacking, and anion−π contacts between receptor and
−
ReO (Figure 5).
distance of 2.15(7) Å and angle of 169(7)°), five intermolecular
4
+
−
−
The monoalkylated receptor complex 2a ·ReO highlights
the importance of a pyridinium ring in the crystal lattice.
C−H HB (C−H···O distances, angles of 2.362(4)−2.615(3)
4
Å, 151.7(3)−161.8(3)°) with three other receptor molecules,
and two anion-π contacts. The second ReO4− participates in a
medium strength HB with water (2.08(6) Å, 175(5)°), eight
Alkylation of the pyridine ring encourages C−H HB and
−
electrostatic interactions between the scaffold and ReO .
4
−
However, conservation of one neutral pyridine permits self-
other C−H HB (2.344(3)−2.757(3) Å, C−H···O angles
−
dimerization and prevents ReO4 from binding in the pocket.
121.1(3)−164.7(3)°) with four other receptor molecules and
one anion−π contact.
As a result, this alters the crystal lattice and induces
herringbone type packing held together through C−H HB,
Although protonation and alkylation of the receptor nullified
the HB accepting abilities of the scaffold, the presence of water
molecules presents a new HB acceptor within the crystal lattice.
The water molecules aid in directing crystal growth by
accepting a HB from the protonated pyridinium ring and
donating two HBs to two ReO4− molecules. A strong N−H HB−
between a receptor and water molecule is observed (N−H···O
distance of 1.74(7) Å and angle of 177(8)°). With the dimer
absent both pyridine rings remain nearly planar with each
other, rotated by 0.72(17)° out of co-planarity. An off-centered
antiparallel π-stacking dimer is noted (Figure 7). These dimers
π−π stacking, and anion−π contacts between the receptor and
−
ReO . This structure elucidates the competitive and energeti-
4
cally favorable nature of dimer formation despite the presence
of anions.
2
+
−
Crystal Structure of 2b ·2ReO ·H O. Colorless single
4
2
2+
−
crystals of 2b ·2ReO ·H O were grown by diffusing ether
into an MeCN solution of the receptor and TBA ReO .
Complex 2b ·2ReO ·H O crystallized in space group PI
one receptor, two ReO , and one water molecule per
4
2
+
−
4
2+
−
with
4
2
̅
−
4
asymmetric unit.
Protonation of 2a eliminates the HB accepting functionality
of the receptor, which prompts the disruption of previously
are staggered in offset columns which are assisted by C−H and
−
N−H HB interactions with ReO and water molecules (Figure
4
−
observed dimers. This enables multidentate C−H HB to ReO
8).
4
2
+
−
2+
−
in the receptor pocket. Complex 2b ·2ReO ·H O exhibits
The crystal structure of 2b ·2ReO ·H O highlights the
influence of two pyridinium rings on ReO4 binding. Alkylating
4
2
4 2
−
−
tridentate C−H HB between ReO and the phenyl and pyridyl
4
−
hydrogens ortho to the alkynyl group (C−H···O distances,
and protonating both pyridine rings eliminates the HB
angles of 2.480(3) Å, 161.0(3)°; 2.390(4) Å, 138.7(3)°; and
accepting capacity of the receptor, thus inhibiting self-
−
−
2
.609(4) Å, 140.1(3)° (Figure 6). In addition, the same ReO4−
dimerization and enabling tridentate binding to ReO . The
4
participates in a medium strength HB with water (O−H···O
inclusion of water establishes a conventional HB that results in
Figure 5. Complex 2a ·ReO4− receptor interactions with ReO , showing dimer systems together held together and displaying herringbone type
+
−
4
packing, similar to that of 1.
9
77
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980

Crystal Growth & Design
Article
Figure 7. Off-centered antiparallel dimer of receptor−guest complex
2+
−
2
b ·2ReO ·H O (interplanar distance of 3.086(13) Å).
4 2
2
+
−
Figure 9. (a) Asymmetric unit of 2c ·2ReO exhibiting tridentate
4
−
2+
binding to ReO . (b) Asymmetric unit of the solvate complex 2c ·
4
−
2
ReO ·2DCM.
4
Figure 8. Close-in examination of staggered columns of receptors held
−
2+
−
together by interactions with molecules of water and ReO .
Complex 2c ·2ReO ·2DCM displays bidentate HB inter-
4
4
actions with the backbone of the receptor between hydrogen−s
ortho to the alkynes and one ReO4− anion (C−H···O
distances, angles of 2.499(3) Å, 156.2(3)° and 2.581(4) Å,
−
strong interactions with one symmetrically unique ReO ,
4
−
−
which allows binding to the other ReO to occur solely
152.7(2)°). Additionally, the same ReO4 participates in three
4
+
−
−
through aryl C−H HB. Similar to 2a · ReO , the alkylated
intermolecular C−H HB (C−H···O distances, angles of
4
pyridinium ring displays C−H HB and electrostatic anion−π
2.568(4)−2.765(3) Å, 139.8(2)−157.9(2)°) with two other
−
contacts with ReO . Altering the electronic state of the
receptor molecules and one anion−π contact. The second
4
−
−
pyridine rings and eliminating the HB acceptor drastically
influences the receptor interactions with guests, creating a
multidentate binding pocket. 2
ReO forms a monodentate C−H HB (2.513(3) Å, C−H···O
4
angle of 149.9(3)°) and an anion−π contact, as well as eight
additional C−H HBs (2.267(3)−2.637(4) Å, C−H···O angles
−
+
−
Crystal Structure of 2c ·2ReO ·2DCM. Two unique
of 130.0(2)−159.2(3)°) with five other receptors. To
accommodate binding with both ReO4− anions, the pyridinium
rings rotate 2.56(13)° and 8.27(13)° out of co-planarity with
the central benzene ring.
4
−
dialkylated receptor and ReO complexes were crystallized7.
4
2
+
−
Complex 2c ·2ReO (Figure 9a) was previously reported.
4
2
+
−
2+
−
Similar to 2b ·2ReO ·H O, 2c ·2ReO exhibits tridentate
4
2
4
−
binding to ReO4 in the binding pocket (2.714(3) Å,
Crystal packing displays staggered columns of offset
antiparallel π-stacking dimers (interplanar distance of
3.174(9) Å). Columns of dimers are held together by HB
interactions to ReO4− while DCM solvate molecules occupy
the space in the binding pocket (Figure 10). Comparison of
1
1
8
8
60.3(3)°; 2.308(4) Å, 162.3(3)°; and 2.639(4) Å,
56.0(3)°). As a result, the pyridinium rings adjust
.7341(5)° from co-planarity and one alkynyl spacer deviates
.7211(7)° from linearity. In addition, an off-centered
−
2+
−
2+
−
antiparallel dimer is noted.
C−H···O distances between 2c ·2ReO and 2c ·2ReO ·
4
4
For this study a solvate of the charged dialkylated pyridyl
2DCM reveals stronger C−H···anion interactions when
tridentate binding occurs.
Similar to 2b ·2ReO ·H O, the two pyridinium rings do
not contain HB acceptors. Introducing a second alkyl group on
−
2+
−
arylacetylene receptor and ReO4 complex (2c ·2ReO ·
4
2+
−
2
DCM) was isolated from vapor diffusion of DCM into an
4 2
+
−
2+
−
MeCN solution of 2c and TBA ReO . Complex 2c ·2ReO ·
4
4
2
DCM crystallized in space group PI
̅
with one receptor, two
the receptor removed the HB abilities of the nitrogen, resulting
−
−
ReO4 anions, and two DCM molecules per asymmetric unit
in C−H HB interactions with ReO . Inclusion of a DCM
4
(Figure 9b).
solvate molecule in the crystal lattice, eliminates the tridentate
−
A DCM molecule is observed occupying the binding pocket,
interactions with ReO that were displayed in the crystals of
4
−
−
2+
−
2+
−
inhibiting tridentate C−H HB to ReO . One ReO molecule
2b ·2ReO ·H O and 2c ·2ReO . All three pyridyl arylace-
4 2 4
2+ 2+
4
4
−
−
participates in a weak C−H HB with a DCM molecule. Due to
tylene dimer complexes, 2b ·2ReO ·H O, 2c ·2ReO , and
4
2
4
2+
−
the inclusion of solvent molecules, receptor contacts with
2c ·2ReO ·2DCM, are held together through aryl C−H HB,
4
−
−
ReO4 were limited to mono- and bidentate interactions, unlike
π−π-stacking, and electrostatic interactions with ReO .
4
2
+
−
2+
−
1
the crystal structures of 2b ·2ReO ·H O and 2c ·2ReO .
Solution Studies. Previously, H NMR titration studies
4
2
4
These results suggest that judicious choice of solvent will be
important when designing these receptors to target ReO4− in
solution.
were completed to quantify the C−H HB interactions of an
2+
−
octylated derivative of 2c ·2ReO in a CDCl /(CD ) CO
4
3
3 2
(3:2 (v/v)) mixed solvent system, resulting in a stability
9
78
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980

Crystal Growth & Design
Article
Through simple alkylation and protonation, the noncovalent
interactions of the presented receptor system with ReO4− were
directly affected. To prevent competitive self-dimerization and
−
enhance electrostatic interactions with ReO , it is essential that
4
the pyridine nitrogens be protonated or alkylated. This also
facilitates multidentate binding from each arm of the receptor
with ReO4− anions. We report evidence that underrepresented
aryl C−H HB is a viable tool in the design of chelators for
−
ReO . Optimization of the bis-ethynyl binding pocket is
4
−
currently underway to increase selectivity for ReO .
4
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.cgd.5b01524.
■
*
S
Experimental procedures for and copies of H, 13C, and
1
19
F NMR spectra of 2a (PDF)
Accession Codes
CCDC 1028025 and 1433000−1433003 contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/
cif, or by emailing data_request@ccdc.cam.ac.uk, or by
contacting The Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Figure 10. (a) View of crystal packing down crystallographic a axis for
2+
−
2
c ·2ReO ·2DCM and (b) view of crystal packing down crystallo-
4
graphic b axis.
AUTHOR INFORMATION
Corresponding Author
E-mail: orion.berryman@umontana.edu.
■
−
1
constant (K ) with a K of 7390 and K of 145 M . In contrast,
a
1
2
+
2+
the binding of the octylated derivatives of 2a and 2b to
*
−
ReO4 in solution has not been quantified. Due to the large
electrostatic component of the interaction, it is likely that the
doubly charged systems 2b and 2c will exhibit stronger
binding than the singly charged 2a . The solid-state studies
presented herein and the previous solution studies have
inspired future experiments that will be used to evaluate the
impact of protonation/alkylation on solution phase anion
binding within this system.
Notes
2
+
2+
The authors declare no competing financial interest.
+
ACKNOWLEDGMENTS
■
This work was funded by the Center for Biomolecular Structure
and Dynamics CoBRE (National Institutes of Health (NIH),
Grant NIGMS P 20GM103546), National Science Foundation
(
NSF)-MRI (Grant CHE-1337908), Montana University
CONCLUSION
In summary, a family of pyridyl-functionalized arylacetylene C−
H HB receptors was prepared exhibiting various alkylation and
System (MREDI, Grant 51030-MUSRI2015-02) and the
University of Montana (UM).
■
−
REFERENCES
protonation states. All ReO4 crystals were grown in
■
competitive crystallization environments where C−H HB−
with this charge diffuse anion was preferred over the OTf
counteranion.
(1) Wildung, R.; McFadden, K.; Garland, T. J. Environ. Qual. 1979, 8,
156−161.
(2) Clark, J. F.; Clark, D. L.; Whitener, G. D.; Schroeder, N. C.;
Strauss, S. H. Environ. Sci. Technol. 1996, 30, 3124−3127.
(3) Katayev, E. A.; Boev, N. V.; Khrustalev, V. N.; Ustynyuk, Y. A.;
Tananaev, I. G.; Sessler, J. L. J. Org. Chem. 2007, 72, 2886.
4) Glenny, M. W.; Lacombe, M.; Love, J. B.; Blake, A. J.; Lindoy, L.
F.; Luckay, R. C.; Gloe, K.; Antonioli, B.; Wilson, C.; Schroder, M.
New J. Chem. 2006, 30, 1755−1767.
(5) Farrell, D.; Gloe, K.; Gloe, K.; Goretzki, G.; McKee, V.; Nelson,
J.; Nieuwenhuyzen, M.; Pal, I.; Stephan, H.; Town, R. M.; Wichmann,
The receptors display unique solid-state interactions with
−
ReO4 through modification of the pyridine ring. Comparably,
self-complementary dimers of neutral scaffold 1 and mono-
(
+
−
alkylated complex 2a ·ReO were observed as a result of the
4
̈
HB accepting abilities of the pyridine nitrogen lone pair.
+
−
−
Complex 2a ·ReO exhibited bidentate binding to ReO4 with
4
hydrogens ortho to the alkyne on the backbone of the receptor.
́
2+
−
2+
−
Complexes 2b ·2ReO ·H O and 2c ·2ReO ·2DCM high-
K. Dalton Trans. 2003, 1961−1968.
4
2
4
light the influence of two pyridinium rings on C−H HB to
(6) (a) Kang, S. O.; Llinares, J. M.; Day, V. W.; Bowman-James, K.
Chem. Soc. Rev. 2010, 39, 3980−4003. (b) Ghosh, S.; Roehm, B.;
Begum, R. A.; Kut, J.; Hossain, M. A.; Day, V. W.; Bowman-James, K.
Inorg. Chem. 2007, 46, 9519−9521. (c) Amendola, V.; Bonizzoni, M.;
−
ReO . Both structures contained solvent molecules in the
4
2+
lattice, which aided crystal growth. The water molecule in 2b ·
−
2
ReO ·H O displayed strong N−H HB with the protonated
4
2
−
Esteban-Go
Taglietti, A. Coord. Chem. Rev. 2006, 250, 1451−1470.
7) Stephan, H.; Berger, R.; Spies, H.; Johannsen, B.; Schmidtchen, F.
J. Radioanal. Nucl. Chem. 1999, 242, 399−403.
8) Massena, C. J.; Riel, A. M. S.; Neuhaus, G. F.; Decato, D. A.;
́ ́
mez, D.; Fabbrizzi, L.; Licchelli, M.; Sancenon, F.;
nitrogen, allowing for tridentate C−H HB to ReO in the
4
2
+
−
binding pocket. The DCM in 2c ·2ReO ·2DCM nullified C−
4
(
−
H HB to ReO inside the binding pocket, which was
4
previously observed. C−H HB interactions between receptor
(
and ReO4− in complex 2c ·2ReO ·2DCM were only
2+
−
4
Berryman, O. B. Chem. Commun. 2015, 51, 1417−1420.
observed with the receptor backbone.
(9) Lim, J. Y.; Beer, P. D. Chem. Commun. 2015, 51, 3686−3688.
9
79
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980

Crystal Growth & Design
Article
(
10) (a) Carroll, C. N.; Naleway, J. J.; Haley, M. M.; Johnson, D. W.
Chem. Soc. Rev. 2010, 39, 3875−3888. (b) Vonnegut, C. L.; Tresca, B.
W.; Johnson, D. W.; Haley, M. M. Chem. - Asian J. 2015, 10, 522−535.
(
c) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. Rev. 2000, 100, 853−
9
08.
11) Berryman, O. B.; Johnson, C. A.; Vonnegut, C. L.; Fajardo, K.
A.; Zakharov, L. N.; Johnson, D. W.; Haley, M. M. Cryst. Growth Des.
015, 15, 1502−1511.
12) Azov, V. A.; Schlegel, A.; Diederich, F. Angew. Chem., Int. Ed.
(
2
(
2
(
005, 44, 4635−4638.
13) Swinburne, A. N.; Paterson, M. J.; Beeby, A.; Steed, J. W. Chem.
-
Eur. J. 2010, 16, 2714−2718.
(
14) Kilah, N.; Beer, P. In Anion Recognition in Supramolecular
Chemistry; Gale, P. A., Dehaen, W., Eds.; Springer: Berlin, Heidelberg,
010; Vol. 24, pp 301−340, DOI: 10.1007/7081_2010_33.
15) Compound 2b was not isolated. During the alkylation reaction,
2
(
methyl triflate had unknown trace amounts of triflic acid present which
afforded 2b.
(
16) Berryman, O. B.; Bryantsev, V. S.; Stay, D. P.; Johnson, D. W.;
Hay, B. P. J. Am. Chem. Soc. 2007, 129, 48−58.
9
80
DOI: 10.1021/acs.cgd.5b01524
Cryst. Growth Des. 2016, 16, 974−980