Selection for a Single Self-Assembled Macrocycle from a Hybrid Metal-Ligand Hydrogen-Bonded (MLHB) Ligand Subunit

Article abstract of DOI:10.1021/acs.inorgchem.5b00857

To expand the interface between self-assembled metal-ligand and hydrogen-bonded architectures, here we report the preparation, self-assembly, and metal-ligand binding of a pyridyl quinolone ligand (5-PYQ). The 5-PYQ ligand self-associates through quinolon

Full text of DOI:10.1021/acs.inorgchem.5b00857

Article
pubs.acs.org/IC
Selection for a Single Self-Assembled Macrocycle from a Hybrid
Metal−Ligand Hydrogen-Bonded (MLHB) Ligand Subunit
Samantha K. Sommer, Ernst A. Henle, Lev N. Zakharov, and Michael D. Pluth*
Department of Chemistry and Biochemistry, Materials Science Institute, 1253 University of Oregon, Eugene, Oregon 97403, United
States
S
* Supporting Information
ABSTRACT: To expand the interface between self-assembled
metal−ligand and hydrogen-bonded architectures, here we
report the preparation, self-assembly, and metal−ligand
binding of a pyridyl quinolone ligand (5-PYQ). The 5-PYQ
ligand self-associates through quinolone hydrogen bonding,
and it binds to metal centers through the pyridine ligand
component. As a first step toward investigating more-complex
hybrid metal−ligand hydrogen-bonded (MLHB) architectures,
we report investigations of 5-PYQ with mono- and bis-
platinated anthracene precursors. These results demonstrate
that the 5-PYQ ligand maintains hydrogen bonding
interactions while binding to square-planar platinum centers,
but that generation of coordination compounds with closed
topology erodes the hydrogen bonding fidelity to favor ambidentate coordination modes of the 5-PYQ ligand.
assembly strategies for MLHB architectures and access the
diverse landscape and full potential of these hybrid MLHB
systems.
INTRODUCTION
■
Contrasting the established strategies for accessing purely
hydrogen-bonded or metal−ligand-derived supramolecular
architectures, the emerging area of self-assembly utilizing both
hydrogen bonds and metal−ligand interactions in the same
architecture has yet to establish well-defined, rational design
strategies for selecting one discrete structure over other
possible products. For example, a recent report demonstrated
the formation of hybrid metal−ligand hydrogen-bonded
(MLHB) triangles and squares from 2-ureido-4-[1H]-
pyrimidinone and cis-substituted square planar Pd(II) compo-
nents, but selective formation of a single discrete structure in
solution was problematic.1 Similarly, the potential to form
oligomeric or polymeric self-assembled products over their
closed hybrid MLHB counterparts, or the possibility of linkage
isomer formation because of the ability of the hydrogen-bond
acceptors to also act as ligands for metal coordination, also
complicates the self-assembly of metal precursors with ligand
subunits containing both metal-binding and hydrogen-bonding
moieties. For example, the assembly of dinuclear
organoplatinum(II) complexes with nicotinic acid afforded
hybrid cyclic structures in solution; however, hybrid polymeric
corrugated chains were present in the solid state, highlighting
the challenges of engineering architectures with consistent
solution and solid-state structures.2 These, as well as other
challenges including the limited number of fully characterized
systems, constitute major limiting factors in developing rational
design strategies to access closed hybrid MLHB assemblies.1−13
Expansion of well-defined, discrete, characterized structures in
this chemical space is warranted to develop well-defined
Toward the goal of generating discrete MLHB assemblies, we
recently reported the design and preparation of a quinolone-
based phosphine ligand 7-DPQ, which we demonstrated
assembles into a discrete hybrid MLHB structure with closed
topology in the presence of a piano-stool rhodium metal
precursor.13 These results prompted us to explore the limits of
self-assembly with similar quinolone ligands by modulating the
metal-binding component of 7-DPQ from a phosphine to a
pyridine, thus providing access to different metal tectons and
coordination directionality (see Scheme 1). Furthermore, the
pendant pyridyl group should provide access to a diverse library
of architectures, based on previous work with pyridine-
containing ligands for metal−ligand self-assembly, particularly
Scheme 1. Comparison of the Structures of the Hybrid
Subunits 7-DPQ and 5-PYQ
Received: April 15, 2015
© XXXX American Chemical Society
A
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when assembled with square planar platinum metal compo-
nents.14−17 As a first step toward investigating more complex
architectures based on pyridine-containing MLHB ligands, we
report here investigations of 5-PYQ with mono- and bis-
platinated anthracene precursors18−21 to determine whether
hybrid MLHB ligands provide selective access to discrete closed
structures over potential oligomeric or polymeric assembly
motifs. Many different assembly motifs are possible upon
assembly of an ambidentate hybrid subunit, such as 5-PYQ,
with a bidentate metal acceptor. Possible final structures
include hybrid polymers, metal−ligand complexes, symmetrical
and asymmetrical macrocyclic isomers, hybrid closed MLHB
macrocycles, or a mixture of these structures (see Scheme 2).
PYQ) was synthesized in five steps from commercially available
precursors (Figure 1a). Reaction of ethyl vinyl ether and oxalyl
Scheme 2. Combination of Ambidentate Hybrid MLHB
Ligand Subunit and Bidentate Metal Acceptor Can Lead to a
Large Number of Possible Products, Hybrid Polymers,
Metal−Ligand Complex, Macrocyclic Isomers, Hybrid
a
Closed MLHB Macrocycle, or a Mixture of Products
Figure 1. (a) Synthesis and (b) molecular structure of 5-PYQ.
Thermal ellipsoids in ORTEP diagram are shown at the 50%
probability level.
chloride yields acid chloride 1,22 which is then used in the
acylation of 3-iodoaniline to afford amide 2. Cyclization of 2
with H2SO4, followed by reaction with SOCl2 and purification
by chromatography, yields 5-iodo-2-chloroquinoline (3).
Subsequent protection with NaOMe generates 5-iodo-2-
methyoxyquinoline (4), which was then coupled with 4-
iodopyridine by reaction with n-BuLi, ZnCl2, and Pd(PPh3)2 to
generate methoxy-protected 5. Deprotection with HCl
regenerates the quinolone motif, affording 5-PYQ. Single
crystals of 5-PYQ suitable for X-ray diffraction were grown
from a DMSO solution of 5-PYQ and confirmed its molecular
structure. 5-PYQ self-associates to form a 2-fold-symmetric,
180° hydrogen-bonded dimer, with a N−H···O hydrogen-bond
distance of 2.7784(14) Å (Figure 1b). The N−H hydrogen
atom was located from the residual electron density map and is
consistent with the quinolone tautomeric form observed
previously in similar ligand scaffolds.13
Assembly of 5-PYQ with Half-Clip 6 and Clip 7. To
investigate the preorganization possible in this system, we
deconstructed clip 723 to half-clip 624 to reduce the number of
rotational degrees of freedom, thus simplifying the system to
gain insights into the spectroscopic signals representative of
final assembly formation (Scheme 3). Monoplatinated 6 was
a
Black dashed lines indicate a hydrogen-bond interaction, and solid
black lines indicate a metal−ligand interaction.
Scheme 3. Structure of Half-Clip 6 and Clip 7
Understanding the requirements for selective access to one
product over another is important for understanding the
possible applications of this new class of structures based on
these hybrid MLHB ligand subunits.
RESULTS AND DISCUSSION
Synthesis of the 5-PYQ Hybrid MLHB Ligand. The
pyridine-based MLHB ligand 5-pyridyl-1H-quinolin-2-one (5-
■
B
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treated with 2 equiv of 5-PYQ with excess KPF6 in a CH2Cl2/
H2O mixed solvent system; after stirring for 4 h at room
temperature, the reaction mixture was washed with water and
reduced in volume to afford half-rectangle A (Figure 2a).
The new 31P{1H} NMR resonance for half-rectangle A is
shifted 5.03 ppm upfield, relative to half clip 6, which is again
consistent with pyridyl binding Pt (Figure 2e,f).23
X-ray-quality crystals of half-rectangle A where grown by
layering EtOH onto a CH2Cl2 solution of the assembly, which
unambiguously confirmed the hydrogen-bonded structure of A
(Figure 3). The crystal structure of half-rectangle A shows 5-
Figure 3. Molecular structure of half-rectangle A. Thermal ellipsoids in
ORTEP diagram are shown at the 50% probability level.
PYQ coordinated to the Pt center of half-clip 6 through the
pyridine with a N−Pt length of 2.130(4) Å. The square planar
geometry around the Pt center of half-clip 6 is maintained with
an average N−Pt−P angle of 91.1°. The 5-PYQ ligand
maintains near-linear (173.0(6)°) hydrogen-bonded dimer
character with an N−H···O bond distance of 2.777(6) Å.
Table 1 summarizes bond lengths and angles for bonds of
interest. Table 2 includes the crystallographic data for 5-PYQ
and half-rectangle A. The crystal packing of half-rectangle A
contains π−π interactions (3.756 Å) of the anthracene rings of
half-clip 6 and quinolone ring of 5-PYQ. Interestingly, half-
rectangle A appears to be preorganized in a geometry that
would favor the formation of polymeric structures in the self-
assembly of clip 7 and 5-PYQ.
Having established that the 5-PYQ ligand can bridge two Pt
centers while maintaining the quinolone hydrogen bonding, we
used clip 7 to probe whether the 5-PYQ ligand would yield one
discrete species from a large number of potential self-assembled
products. Such complexes include the coordination polymer
(B), metal−ligand complex (C), macrocycle isomers (D and E)
or hybrid MLHB rectangle (F) (see Scheme 4). Although the
molecular structure of A is preorganized to favor the formation
of a polymeric structure such as B, previous work with 7-DPQ
suggests that closed rectangle F could also be accessible. By
contrast, if ambidentate metal−ligand interactions or inter-
ligand π-stacking interactions are significant, coordination
compounds D and E could also be accessed.
1
Figure 2. (a) Synthesis of half-rectangle A. (b) H NMR spectrum
(500 MHz, CD2Cl2) of half-clip 6. (c) 1H NMR spectrum (500 MHz,
CD2Cl2) of 5-PYQ with α-(red) and β-(blue) pyridyl proton signals
colored for clarity. (d) H NMR spectrum (500 MHz, CD2Cl2) for
half-rectangle A, showing the downfield shift and splitting of the α-
(red) and β-(blue) pyridyl protons upon 5-PYQ binding Pt. (e)
31P{1H} NMR spectrum (202 MHz, CD2Cl2) of half-clip 6. (f)
31P{1H} NMR spectrum (202 MHz, CD2Cl2) of half-rectangle A.
1
Analysis of the 1H NMR spectrum of A suggested formation of
a highly symmetric structure and provided distinct resonances
from the monomeric 5-PYQ and half-clip 6 subunits (Figure
2b−d). Particularly diagnostic were the downfield shifts of the
α- and β-pyridyl proton signals of 5-PYQ due to the loss of
electron density upon platinum coordination. Coordination of
the 5-PYQ ligand to the platinum also results in restricted bond
rotation, generating H′α and Hα′′, as well as H′β and H′β′ signals,
which are also diagnostic of formation of the assembled
structure (see Figure 2c and Figure 2d). Only one N−H
resonance is observed in A, and it is shifted downfield from
unbound 5-PYQ, indicating that a symmetrical 5-PYQ
hydrogen-bonding environment is present in half-rectangle A
(Figure 2c and Figure 2d). The 31P{1H} NMR spectrum of A
also supports the formation of a single, highly symmetric
species, as evidenced by the appearance of a sharp singlet at
11.82 ppm with 195Pt satellites (JP,Pt = 2647.2 Hz) (Figure 2f).
To determine which of the following structural arrangements
were formed from full-clip 7, we treated a CH2Cl2:H2O
solution of 7 with excess KPF6 and 4 equiv of 5-PYQ (Figure
1
4a). The resultant H NMR spectrum of the crude reaction
mixture showed peaks corresponding to a new compound, but
also free 5-PYQ ligand. Separation of these two species by
1
chromatography yielded a product with a H NMR spectrum
consistent with macrocycle D (Figure 4a). Consistent with the
restricted rotation of a pyridine ligand binding to clip 7, two
1
sets of doublets with downfield shifts were observed in the H
NMR spectrum for the α- and β-pyridyl protons (see Figure 4c
and Figure 4d). Although we would expect a 2:1 pyridyl 5-PYQ
C
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Table 1. Selected Bond Lengths and Angles of Half-Rectangle A
bond pair
bond/interaction length (Å)
bond angle
measurement (deg)
NH(1A)−O(2B)
N(1A)−Pt(1A)
2.777(6)
2.130(4)
NH(1A)−O(2B)
173.0(6)
90.52(12)
91.78(12)
89.51(16)
88.08(16)
8.73
N(1A)−Pt(1A)−P(1A)
N(1A)−Pt(1A)−P(2A)
P(1A)−Pt(1A)−C(1A)
P(2A)−Pt(1A)−C(1A)
plane(quin)−plane(anth)
P(1A)−Pt(1A)
P(2A)−Pt(1A)
π(quin)−π(anth)
2.3041(14)
2.3122(15)
3.756
Table 2. Crystallographic Data for 5-PYQ and Half-
Rectangle A
Scheme 4. Self-Assembly of 5-PYQ with Clip 7 Selects Only
for Macrocycle Isomer D, Rather than Polymer B, Metal-
Ligand Complex C, Macrocyclic Isomer E, or Hybrid MLHB
Rectangle F
5-PYQ
A
formula
C14H10N2O
222.24
C40H48ClF6N2OP3Pt
1010.24
formula weight
temperature (K)
crystal system
space group
a (Å)
100(2)
150(2)
triclinic
monoclinic
P21/n
P1
̅
7.7275(11)
8.7217(12)
8.9532(12)
115.602(4)
74.194(3)
75.677(3)
535.09(13)
2
9.5788(8)
16.5245(13)
25.198(2)
90
b (Å)
c (Å)
a (deg)
b (deg)
92.1140(15)
90
g (deg)
V (Å3)
3985.8(6)
4
Z
r (mm−1
)
1.379
1.684
m (mm−1
)
0.089
3.771
F(000)
232
2016
crystal size (mm3)
limiting indices
0.14 × 0.10 × 0.07
−10 ≤ h ≤ 9
−11 ≤ k ≤ 11
−11 ≤ l ≤ 11
2.49−28.00
99.9
0.13 × 0.12 × 0.11
−11 ≤ h ≤ 11
−19 ≤ k ≤ 19
−29 ≤ l ≤ 29
1.62−25.00
100.0
θ range (deg)
completeness to θ (%)
total reflections
10963
42411
independent reflections
data/restraints/parameters
max, min transmission
R1 (wR2) [I > 2σ(I)]
R1 (wR2)
goodness of fit, GoF (F2)
max, min peaks (e/Å3)
2587
7986
2587/0/2194
0.9938, 0.9876
0.0427 (0.1129)
0.0517 (0.1195)
1.048
7023/0/491
0.680, 0.650
0.0338 (0.0724)
0.0517 (0.0811)
1.016
0.422, −0.249
1.634, −1.037
binding to 7 based on the structure of half-rectangle A,
integrations suggest the presence of a complex with a 1:1 5-
PYQ:7 ratio, indicative of the formation of macrocycle isomers
D or E. The 31P{1H} NMR spectrum of D displayed two sharp
singlets at 8.89 ppm (JP,Pt = 2759.7 Hz) and 6.27 ppm (JP,Pt
=
2725.1 Hz), shifted 4.48 and 7.10 ppm upfield relative to clip 7,
respectively, which is consistent with two different phosphorus
environments as we would expect for macrocycle D or E
(Figure 4d,f). The 31P{1H} NMR alone is not sufficient to
distinguish whether macrocycle D or E is present. However,
isomeric structures D and E can be differentiated by the
solution (Figure 4d). 1H COSY and 1H NOESY NMR
experiments confirmed the 1H NMR proton assignments
1
discussed above. Furthermore, the H NOESY NMR experi-
ments reveal a strong NOE correlation of the 5-PYQ N−H
resonance and one set of PEt3 groups, as well as a NOE signal
of the 5-PYQ−Ha and pyridyl−Hα protons, strongly indicating
that macrocycle D is the complex found in solution (Figure 5).
The NOE of pyridyl−Hα and all 5-PYQ protons resonances
indicate that there is a π-stacking interaction between the two
Pt-bound 5-PYQ ligands (Figure 5c, black circle), which may
contribute to favoring the formation of the macrocycle D
structure instead of the expected hybrid MLHB polymer (B) or
rectangle (F).
1
anthracene H9 and H10 resonances in the H NMR spectrum.
For example, isomer E would generate two sets of H9 and H10
peaks, whereas isomer D would only generate one set of H9 and
H10 peaks, due to the presence of an inversion center at the
1
center of the macrocycle. The H NMR spectrum shows only
one set of very sharp peaks for anthracene H9 and H10 peaks,
indicating macrocycle isomer D is the complex present in
D
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Figure 4. (a) Synthesis of macrocycle D. (b) 1H NMR spectrum (500
MHz, CD2Cl2) of half-clip 6. (c) 1H NMR spectrum (500 MHz,
CD2Cl2) of 5-PYQ with α-(red) and β-(blue) pyridyl proton signals
1
colored for clarity. (d) H NMR spectrum (500 MHz, CD2Cl2) for
macrocycle D, showing the downfield shift and splitting of the α-(red)
and β-(blue) pyridyl protons upon 5-PYQ binding Pt. (e) 31P{1H}
NMR spectrum (202 MHz, CD2Cl2) of clip 7. (f) 31P{1H} NMR
spectrum (202 MHz, CD2Cl2) for macrocycle D.
To further rule out formation of large polymeric structures
like B, or oligomeric aggregates, we performed 1H DOSY NMR
experiments to investigate the diffusion coefficient of the
reaction product and to determine whether multiple species
were present in solution. 1H DOSY NMR experiments
confirmed the presence of one discrete species in solution,
Figure 5. (a) Selected NOE contacts in macrocycle D, color coded to
corresponding circled NOE signal for clarity. (b) H NMR NOESY
spectra (500 MHz, CD2Cl2) of macrocycle D and (c) zoom-in on
aromatic region. The NOE between pyridyl−Hα and all of the 5-PYQ
protons is highlighted in black.
1
with a diffusion coefficient of (4.45
0.05) × 10−10 m2 s−1
correlating to a radius consistent with the presence of the
macrocycle D (see Figure 6). Table 3 compares the radii
calculated from diffusion data with the crystallographic radii of
5-PYQ and half-rectangle A. In both compounds, the solution
and solid-state radii agree well, suggesting that the hydrogen-
bonding remains intact in solution. The calculated radius of
macrocycle D is consistent with the expected size (see Figure
S18 for MMFF optimized structure), due to the more spherical
nature of D by comparison to half-rectangle A.
interactions when complexed with mono-platinated half-clip 6.
Upon treatment with bis-platinated 7, a single discrete
macrocycle is formed over other possible coordinate polymers,
1
oligomers, or MLHB structures as evidenced by H, 31P{1H},
NOESY, and DOSY NMR experiments. Selective macrocycle
formation indicates that further investigation of this system
could lead to potential applications in host−guest chemistry or
catalysis. The selectivity for forming a single coordination
macrocycle suggests that the interligand π-stacking interactions
of 5-PYQ outweigh the self-complementary quinolone hydro-
gen bonding interactions, providing new insights into the
design requirements in self-assembled systems containing both
metal−ligand and hydrogen-bonding interactions. Investigation
CONCLUSION
■
In conclusion, we report the preparation of the pyridyl
quinolone ligand 5-PYQ and demonstrate that this ligand
scaffold maintains self-complementary hydrogen bonding
E
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using the PFG double stimulated echo pulse sequence. High-
resolution mass spectrometry experiments were performed by the
Biomolecular Mass Spectrometry Core of the Environmental Health
Sciences Core Center at Oregon State University. Diffraction data
were collected on a Bruker Smart Apex diffractometer at 150(2) K
using Mo Kα radiation (λ = 0.71073 Å). Data reduction was
performed in SAINT, and absorption corrections were applied using
SADABS. All refinements were performed using the SHELXTL
software package.25−27 All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were treated in calculated positions
except those involved in hydrogen bonds, which were found on the
residual density map and refined with isotropic thermal parameters.
5-Iodo-2-chloroquinoline (3). Solid 2 (5.76 g, 21.3 mmol) was
added to concentrated H2SO4 (97%, 10 mL) and stirred at room
temperature for 6 h. The resultant reaction mixture was poured into
ice water (100 mL). The resultant precipitate was filtered, washed with
Et2O (25 mL), and dried to give a beige solid. The crude product (500
mg, 1.38 mmol) was dissolved in CH2Cl2 (30 mL) and SOCl2 (130
μL, 214 μmol) and DMF (118 μL, 1.51 mmol) were added. The
reaction mixture was refluxed for 3 h, cooled to room temperature, and
poured into water (50 mL). After extraction with EtOAc (3 × 50 mL),
the combined organic fractions were dried over MgSO4, evaporated,
and the residue was purified by flash chromatography (hexanes/EtOAc
1
9:1) to afford 3 (0.152 g, 28%) as white solid. H NMR (500 MHz,
CD2Cl2) δ: 8.40 (d, 1H, 8.8 Hz), 8.18 (d, 1H, 8.3 Hz), 8.03 (d, 1H, 8.3
Hz), 7.50 (m, 2H). 13C{1H} NMR (125 MHz, CD2Cl2) δ: 151.6,
148.0, 143.2, 138.2, 131.4, 129.5, 129.1, 123.9, 97.6. HRMS (m/z): [M
+H]+ calcd for C9H6NClI 289.9230, found 289.9092.
5-Iodo-2-methyoxyquinoline (4). A solution of 3 (0.651 g, 2.25
mmol) and NaOMe (10.1 mmol, prepared from 231.7 mg of Na in 10
mL of MeOH) was heated at 65 °C for 2 h. The reaction mixture was
poured into a saturated aqueous NH4Cl solution (10 mL) at 0 °C.
After extraction with CH2Cl2, the combined organic layers were dried
over MgSO4 and evaporated to afford 4 (0.620 g, 97%) as a white
solid. 1H NMR (500 MHz, CD2Cl2) δ: 8.25 (d, 1H, 9.0 Hz), 7.98 (d,
1H, 7.6 Hz), 7.85 (d, 1H, 7.6 Hz), 7.35 (t, 1H, 7.6 Hz), 6.98 (d, 1H,
9.0 Hz), 4.10 (s, 3H). 13C{1H} NMR (125 MHz, CD2Cl2) δ: 163.6,
147.6, 143.3, 135.7, 131.0, 128.7, 127.6, 115.2, 98.4, 54.2. HRMS (m/
z): [M+H]+ calcd for C10H9NOI 285.9729, found 285.9731.
1
Figure 6. H NMR DOSY spectra (500 MHz, CD2Cl2) of (a) half-
rectangle A and (b) macrocycle D.
Table 3. Diffusion Data for 5-PYQ, Half-Rectangle A, and
Macrocycle D, Including the Calculated Radii and Radii
from the Determined Molecular Structures
5-Pyridyl-2-methylquinoline (5). In a glovebox, a solution of 4
(0.988 g, 3.46 mmol) in THF (30 mL) was cooled in a cold well
cooled with liquid N2, n-BuLi (2.73 mL of a 2.5 M solution in pentane,
6.93 mmol) was added slowly with stirring. The solution was allowed
to sit in a cold well for 15 min, after which it was treated with a
solution of ZnCl2 (0.708 g, 5.19 mmol) in THF (10 mL). After an
additional 15 min, a solution containing Pd(PPh3)4 (80 mg, 69 μmol)
and 4-iodopyridine (1.42 g, 6.93 mmol) in THF (10 mL) was added
to the reaction. The reaction mixture was then removed from
glovebox, held on ice for 5 min, and then was heated to reflux under
N2 overnight. The solution was allowed to cool to room temperature
and then cooled on an ice bath while H2O (20 mL) was added. After
extraction with CH2Cl2 (3 × 75 mL), the combined organic fractions
were dried over MgSO4, evaporated, and the residue was purified by
flash chromatography (hexanes/EtOAc 3:2) to afford 6 (0.199 g, 24%)
as white solid. 1H NMR (500 MHz, CD2Cl2) δ: 8.75 (d, 2H, 5.4 Hz),
8.06 (d, 1H, 9.3 Hz), 7.94 (d, 1H, 8.8 Hz), 7.73 (t, 1H, 7.3 Hz), 7.44
(d, 2H, 5.9 Hz), 7.39 (d, 1H, 7.3 Hz), 6.93 (d, 1H, 9.3 Hz), 4.11 (s,
3H). 13C{1H} NMR (125 MHz, CD2Cl2) δ: 163.0, 150.4, 148.2, 147.6,
138.1, 136.6, 129.6, 128.4, 125.4, 125.3, 123.1, 113.9. HRMS (m/z):
calcd for C15H13N2O 237.1028, found 237.1035.
5-Pyridyl-1H-quinolin-2-one (5-PYQ). Solid 6 (0.177 g, 0.749
mmol) was dissolved in concentrated HCl (5 mL) and refluxed for 6
h, after which the pH of the reaction mixture was adjusted to pH 7
with 6 M NaOH. The reaction mixture was extracted with a CH2Cl2/
MeOH solution (3 × 20 mL), the organic fractions were combined
and dried over MgSO4, and the solvent was removed under reduced
pressure to afford 5-PYQ as white solid (0.106 g, 64%). 1H NMR (500
MHz, CD2Cl2/MeOD) δ: 8.68 (d, 2H, 5.4 Hz), 7.84 (d, 1H, 9.7 Hz),
7.631 (t, 1H, 7.33 Hz), 7.25 (m, 3H), 7.22 (d, 1H, 7.3 Hz), 6.63 (d,
1H, 9.7 Hz). 13C{1H} (125 MHz, CD2Cl2/MeOD) δ: 163.9, 149.8,
5-PYQ
half-rectangle A macrocycle D
diffusion coefficient
9.07 0.56
4.98 0.31
4.45 0.23
(× 10−10 m2 s−1
)
radius (Å)
Stokes−Einstein
5.87 0.36
5.98
10.69 0.35
10.12
11.04 0.60
a
crystal structure
a
Average of x, y, z radii.
of the quinolone interligand π-stacking interactions will be the
focus of future studies and will be reported in forthcoming
publications.
EXPERIMENTAL SECTION
■
Materials and Methods. All air- and moisture-sensitive reactions
were performed under a nitrogen atmosphere using standard Schlenk
and glovebox techniques. All chemicals were used as purchased unless
noted otherwise. 3-Ethoxyprop-2-enoyl chloride (1),22 3-Ethoxy-N-(3-
iodophenyl)acrylamide (2),13 [1-trans-Pt(PEt3)2NO3]-8-chloroanthra-
cene (6),24 and 1,8-bis(trans-Pt(PEt3)2NO3)anthracene (7)23 were
prepared as previously described. Anhydrous and air-free solvents were
obtained from a solvent purification system (Pure Process
Technologies). Deuterated solvents were dried and deoxygenated by
distillation over the appropriate drying agent followed by three freeze−
pump−thaw cycles. NMR spectra were acquired on a Varian INOVA
500 MHz spectrometer at 25 °C and are referenced internally to
residual protic solvent resonances. Data for 1H, 31P{1H}, and 13C{1H}
NMR spectra are reported as follows: chemical shift (δ, ppm),
multiplicity: (s) singlet, (d) doublet, (t) triplet, (m) multiplet,
1
integration, coupling constant (Hz). H DOSY spectra were recorded
F
DOI: 10.1021/acs.inorgchem.5b00857
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
148.2, 139.6, 138.7, 138.4, 131.1, 125.6, 124.2, 122.2, 117.8, 116.9.
HRMS (m/z): calcd for dimer C28H21N4O2 445.1665, found
445.1685.
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[1-(trans-Pt(PEt3)2(5-PYQ))-8-chloroanthracene]2(PF6)2 (A). KPF6
(57.4 mg, 0.311 mmol) in water (1.5 mL) was added to a solution of
anthPtCl (36.9 mg, 5.24 μmol) in CH2Cl2 (1.5 mL) and stirred
vigorously for 20 min, after which a solution of 5-PYQ (23.3 mg, 105
mmol) in CH2Cl2 (1.5 mL) and MeOH (0.5 mL) was added. The
reaction mixture was then stirred vigorously for 4 h at room
temperature. The organic layer was removed, washed with water (5
mL), and reduced to 1 mL under flow of N2 and then layered with
EtOH. Diffusion of EtOH into the saturated solution of CH2Cl2
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1
afforded A as orange crystals (116 mg, 47%). H NMR (500 MHz,
CD2Cl2) δ: 10.89 (s, 1H), 9.73 (s, 1H), 9.07 (d, 1H, 5.8 Hz), 8.95 (d,
1H, 5.6 Hz), 8.52 (s, 1H), 8.04 (d, 1H, 8.5 Hz), 7.93 (d, 1H, 5.6 Hz),
7.89 (d, 1H, 5.6 Hz), 7.84 (m, 2H), 7.75 (t, 1H, 7.5 Hz), 7.68 (m,
2H), 7.53 (d, 1H, 7.8 Hz), 7.49 (t, 1H, 7.8 Hz), 7.40 (d, 1H, 7.3 Hz),
7.34 (t, 1H, 7.3 Hz), 6.82 (d, 1H, 10.0 Hz), 1.57−1.23 (m, 12 H), 1.14
(m, 18 H). 31P{1H} NMR (202 MHz, CD2Cl2) δ: 11.82 ppm (JP,Pt
=
2647.1 Hz).
[1,8-bis(trans-Pt(PEt3)2(5-PYQ))anthracene]2(PF6)4 (D). KPF6
(30.4 mg, 165 μmol) in water (1.5 mL) was added to a solution of
anthPt2 (32.0 mg, 27.6 μmol) in CH2Cl2 (1.5 mL) and stirred
vigorously for 20 min, after which a solution of 5-PYQ (24.5 mg, 110
μmol) in CH2Cl2 (1.5 mL) and MeOH (0.5 mL) was added. The
reaction mixture was stirred vigorously for 4 h at room temperature.
The organic layer was removed, washed with water (5 mL), and
evaporated to afford an orange-red solid that was purified by
preparatory chromatography (5% MeOH:CH2Cl2) to afford D (42.2
1
mg, 49%) as a red-orange solid. H NMR (500 MHz, CD2Cl2) δ:
12.05 (s, 1H), 10.03 (s, 1H), 9.56 (d, 1H, 5.3 Hz), 8.79 (d, 1H, 5.8
Hz), 8.29 (s, 1H), 7.99 (d, 1H, 4.6 Hz), 7.85 (d, 1H, 5.3 Hz), 7.76 (d,
1H, 9.7 Hz), 7.72−7.64 (m, 3H), 7.59 (d, 1H, 6.3 Hz), 7.49 (d, 1H,
8.3 Hz), 7.43 (d, 1H, 6.3 Hz), 7.34 (d, 1H, 7.3 Hz), 7.15−7.07 (m,
2H), 6.74 (d, 1H, 9.7 Hz), 1.83 (m, 12 H), 1.62 (m, 12 H), 1.46 (m,
12 H), 1.26 (m, 12 H), 1.04−0.84 (m, 72 H). 31P{1H} NMR (202
MHz, CD2Cl2) δ: 8.89 ppm (JP,Pt = 2759.79 Hz), 6.27 ppm (JP,Pt
=
2725.1 Hz).
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental details, NMR spectra, including DOSY, COSY,
and NOESY experiments, MMFF optimized structure of D,
and X-ray crystallographic data. The Supporting Information is
available free of charge on the ACS Publications website at
DOI: 10.1021/acs.inorgchem.5b00857.
(25) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found Crystallogr.
2008, 64, 112.
(26) Sheldrick, G. M. SHELXTL; University of Gottingen:
̈
Gottingen, Germany, 2008.
̈
(27) Sheldrick, G. M. SHELXTL; University of Gottingen:
̈
AUTHOR INFORMATION
Corresponding Author
*E-mail: pluth@uoregon.edu.
Gottingen, Germany, 2000.
̈
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by funding from the University of
Oregon (UO). The NMR facilities at the UO are supported by
the NSF/ARRA (Grant No. CHE-0923589). The Biomolecular
Mass Spectrometry Core of the Environmental Health Sciences
Core Center at Oregon State University is also acknowledged.
Oregon State University is supported, in part, by the NIEHS
(Grant P30ES000210) and the NIH.
REFERENCES
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DOI: 10.1021/acs.inorgchem.5b00857
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