Coordination-driven self-assembly of supramolecular cages: Heteroatom-containing and complementary trigonal prisms

Article abstract of DOI:10.1021/ja030209n

The self-assembly of three nanoscopic prisms of approximate size 1 × 4 nm is reported. Tetrahedral carbon, silicon, and phosphorus were used as structure-defining elements in these coordination based cages. A carbon-based assembly completes a pair of nanoscopic complementary 3-D structures. The formation of the structures is supported by multinuclear NMR, ESI FT-ICR mass spectrometry, and elemental analysis data.

Full text of DOI:10.1021/ja030209n

Published on Web 07/18/2003
Coordination-Driven Self-Assembly of Supramolecular Cages:
Heteroatom-Containing and Complementary Trigonal Prisms
Yury K. Kryschenko,† S. Russell Seidel,† David C. Muddiman,‡
Angelito I. Nepomuceno,‡ and Peter J. Stang*,†
Contribution from the Department of Chemistry, UniVersity of Utah, 315 South 1400 East,
Rm. 2020, Salt Lake City, Utah 84112, and W. M. Keck FT-ICR Mass Spectrometry Laboratory
and Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation,
Rochester, Minnesota 55905
Received April 7, 2003; Revised Manuscript Received May 22, 2003; E-mail: stang@chem.utah.edu
Abstract: The self-assembly of three nanoscopic prisms of approximate size 1 × 4 nm is reported.
Tetrahedral carbon, silicon, and phosphorus were used as structure-defining elements in these coordination-
based cages. A carbon-based assembly completes a pair of nanoscopic complementary 3-D structures.
The formation of the structures is supported by multinuclear NMR, ESI FT-ICR mass spectrometry, and
elemental analysis data.
symmetry.30-33 While many of these have a significant potential
Introduction
for host-guest chemistry, the lower-symmetry assemblies
Coordination-driven self-assembly of discrete nanoscopic
structures has become one of the most prevalent areas of modern
supramolecular chemistry.1-12 In the past decade, numerous two-
and three-dimensional assemblies have been reported. The list
of 3-D ensembles synthesized to date includes supramolecular
Platonic13-20 and Archimedean21,22 polyhedra, prisms,23-26
adamantanoids,27-29 as well as many other cages of varying
promise better selectivity toward similarly shaped guest mol-
ecules23,34 and are, therefore, of special interest as synthetic
targets. Using the directional bonding methodology, our group
previously assembled a series of supramolecular prisms of D3h
symmetry.23,24
Heteroatoms are integral to coordination-driven self-assembly,
as many structures include phosphorus-containing ligands or
donor pyridine groups. However, tetrahedral phosphorus and
silicon atoms have never been used as shape-defining elements
in discrete three-dimensional assembly. In fact, all supramo-
lecular cages with tetrahedral angles - for example, double
squares32 or dodecahedra14 - are exclusively carbon-based. With
† University of Utah.
‡ Mayo Clinic and Foundation.
(1) Seidel, S. R.; Stang, P. J. Acc. Chem. Res. 2002, 35, 972-983.
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J. AM. CHEM. SOC. 2003, 125, 9647-9652
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A R T I C L E S
Kryschenko et al.
Scheme 1. Synthesis of Acceptor Tripods 7, 8, and 9
a few exceptions,23,30 only tris(4-pyridyl)methanol and its
derivatives have been employed as rigid tritopic 109.5° tectons.
In addition, discrete 3-D self-assembled structures containing
silicon in any position, to the best of our knowledge, have not
appeared in the literature. It should be noted, however, that
silicon-based building blocks have been utilized in infinite three-
dimensional hydrogen bonded networks.35
The directional bonding approach to self-assembly1,3,5 often
allows for alternative pathways to the same geometry. An
example of such self-assembled structures can be found in the
syntheses of cuboctahedra,22 where a pair of matching cages
was assembled from two complementary sets of angular and
tritopic building units. Similar reasoning has been applied to
other nanoscopic cages, such as truncated tetrahedra.21
Herein, we describe the coordination-driven self-assembly of
new supramolecular prismatic cages. Two of these ensembles
include, respectively, tetrahedral phosphorus and silicon in key
shape-defining locations. For the first time, the precise position-
ing of these heteroatoms has been achieved in discrete supramo-
lecular 3-D assemblies, which may also have implications in
materials science. The structure and composition of the as-
semblies have been characterized by multinuclear NMR and
electrospray ionization Fourier transform ion cyclotron reso-
nance mass spectrometry (ESI-FT-ICR-MS).
Figure 1. X-ray structure of a representative Pt halide (4).
Table 1. Tripod Coordination Angles (deg)
tripod:
center:
4
C
6
P
10
Si
Results and Discussion
Synthesis of the Tripod Linkers. Halogenated aromatic
compounds have been used extensively as starting materials in
the preparation of building blocks for self-assembly.22,34,36 The
desired tritopic linkers (7-9) were synthesized by triple
oxidative addition37 of platinum to the corresponding tris(4-
halophenyl) compounds 1-3, followed by the exchange of the
halogen atoms in the resulting metal complexes 4-6 for nitrate
groups by reaction with silver nitrate (Scheme 1). Compound
3 is known,38 and iodides 139 and 2 can be easily obtained in
one or two steps from commercially available materials.
X-ray diffraction studies were performed on intermediate
platinum(II) halides 4 and 6, while silicon-centered tripod 8
required an anion exchange to the corresponding triflate species
10 before crystals of an acceptable quality could be obtained
(10 crystallizes with a molecule of water coordinated to one of
the Pt atoms in place of one of its triflates). Figure 1 shows a
representative ORTEP drawing of a parent compound (4), and
the angles between coordination vectors in these compounds
are listed in Table 1. As is evident from the structural data, the
R
112.4
110.7
107.6
110.2
107.3
107.3
107.3
107.3
107.4
105.8
111.8
108.3
â
γ
ave.
average angle between these vectors in all three cases is close
to tetrahedral (109.5°), even though there is some variation, most
probably due to crystal packing forces. Somewhat unexpectedly,
the phosphorus-centered tripod 6 is the only one that crystallizes
as a C3-symmetrical species.
Synthesis of the Donor “Clip”. Certain self-assembled
structures call for the use of rigid ditopic tectons that have a 0°
(or close) dihedral angle between their coordination vectors.
The sole representative of this interesting class of compounds
to date is the anthracene-based “clip”40 - a platinum-containing
acceptor molecule. Scheme 2 shows the synthesis of a comple-
mentary, pyridine-containing “clip” from 1,8-dichloroanthracene
(11). First, 11 is converted into known 1,8-bis(ethynyl) an-
thracene (12) in two steps.41 Next, compound 12 is coupled with
4-bromopyridine hydrochloride,42 yielding the desired donor
“clip” (13).
(35) Wang, X.; Simard, M.; Wuest, J. D. J. Am. Chem. Soc. 1994, 116, 12119-
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Soc. 2003, 125, 5193-5198.
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9
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Self-Assembly of Supramolecular Cages
A R T I C L E S
Scheme 2. Synthesis of the Donor “Clip” 13
suggests the formation of a discrete, highly symmetric assembly.
The upfield shift of this signal from around 20 ppm for the
starting tripods, along with the change in 1JPPt for the flanking
195Pt satellites (∆J ) -111 Hz), is indicative of coordination
of platinum to pyridine. The 31P NMR spectra of the carbon-
and silicon-centered prisms 14 and 15 are virtually identical,
while the phosphorus-centered prism 16 exhibits a broad singlet
at 24 ppm arising from the two phosphorus atoms at the vertices
of the assembly. The broadening of this signal can be attributed
to the interaction between these two atoms and the phosphorus
atoms of the PEt3 groups in the assembly. As a result of this
same long distance (six bond) coupling, the signal of the
phosphine P atoms displays some degree of splitting into a
doublet. The 1H NMR data for all three prisms also agree with
the notion of closed, symmetrical pyridine-linked structures. In
contrast to certain previously reported assemblies,23,36,40 the
rotation of the pyridine groups in structures 14-16 is not
restrained. An obvious reason for such a difference is that these
pyridine groups are located closer to the center of the new cages.
Mass-spectrometric studies of the prisms (14-16) were
performed by the ESI-FT-ICR technique, which allowed keeping
the assembly intact during the ionization process while obtaining
the high resolution required for unambiguous determination of
the charge states. It is very challenging to determine accurate
mass for these assemblies due to their large isotopic shift, the
latter defined as the difference between average and monoiso-
topic masses. These complexes have an isotopic shift of >32
amu, due to the presence of six platinum atoms.
Figure 2. Schematic (top) and ORTEP (bottom) representations of the
X-ray structure of 13.
In comparison, a protein of the same nominal molecular
weight has an isotopic shift only on the order of 3 amu. As a
result, the most abundant isotopic mass must be utilized, but
this can only be determined with high confidence to (1 amu
due to the inherent reliance on ion abundance to determine mass;
a 1 amu mass error at a molecular weight of 4500 exceeds 200
ppm.
The new donor building block 13 is the requisite counterpart
for acceptor tripods 7-9 to be used in the self-assembly of
D3h-symmetrical, somewhat distorted trigonal prisms. The X-ray
structure of 13 is shown in Figure 2. The structural feature which
makes this molecule even better suited for the stated purpose
is that the coordination vectors are not perfectly parallel to each
other, as the dihedral angle between the 4-pyridylethynyl groups
is ∼11°. The almost perpendicular mutual arrangement of the
The study of cages 14-16 confirmed in all cases the
formation of assemblies combining two tripods with three
“clips”. Figure 3 shows the mass spectrum of the carbon-
centered assembly (14, 20 mg/mL in 50% aqueous acetone),
with an experimental resolving power of ∼30 000 (full-width
half maximum definition), and the internal mass calibrants.
Prism 14 is denoted as M, while the calibrants are denoted B
for bradykinin and G for glucagon. The inset in Figure 3 displays
an expansion of the [M - 4NO3]4+ peak along with the
“theoretical” isotopic distribution. The 4+ charge state was used
for mass determination, because it was flanked by the internal
standards. The mass measurement accuracy for the most
abundant isotope, after internal calibration (MMAint), was
determined to be -0.13 ppm. Clearly, the experimentally
determined most abundant isotope was correct. The spectra of
heteroatom-centered assemblies 15 and 16 are very similar to
1
pyridine groups suggests unhindered rotation. Indeed, the H
NMR spectrum shows a single set of R and â pyridine protons
for this molecule.
Self-Assembly of Supramolecular Trigonal Prisms. The
formation of trigonal prisms 14-16 from tripods 7-9 and “clip”
13 proceeds in virtually quantitative yield as shown in Scheme
3. The reaction setup is the same for all three assemblies, be-
cause the starting materials are nearly identical. The assembly
of each cage is carried out in 50% aqueous acetone and is com-
plete after the reaction has been stirred for 4 h at room temper-
ature, as is evidenced by the complete dissolution of the starting
materials and the corresponding changes in the NMR spectra.
In the 31P NMR spectrum of cages 14-16, a sharp singlet
from the triethylphosphine ligands at approximately 14 ppm
9
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A R T I C L E S
Kryschenko et al.
Figure 3. ESI-FT-ICR mass spectrum of prism 14.
Scheme 3. Self-Assembly of Supramolecular Prisms 14 (C-centered), 15 (Si-centered), and 16 (P-centered)
Table 2. ESI-FT-ICR MS of 14-16: [M - 4NO3]4+ Peaks
prisms as shown in Scheme 3. While it is possible to isolate
the complexes 14-16 as stable microcrystalline solids, the
ultimate proof of their structure by X-ray diffraction requires
quality single crystals that we are unable to obtain at this time.
most abundant isotopic mass
MMA
(ppm)
int
prism
ionic formulaa
theoreticalb
experimental
14
15
16
C196H258N8O6P12Pt6
C194H258N8O6P12Pt6Si2
C192H252N8O8P14Pt6
4363.4882
4395.4422
4403.3825
4363.4876
4395.4626
4403.3997
-0.13
4.65
3.90
The carbon-based prism (14), along with a previously reported
cage 17,23 constitutes a complementary pair of isomeric
structures (Figure 4). The two cages have the same molecular
formula (C196H258N12O18P12Pt6), share the same geometry, but
have different connectivity. This demonstrates the scope and
versatility of the directional bonding methodology, at the same
time allowing for easier characterization of the new assemblies.
The close structural similarity between 14-16 and the previ-
ously published prism 17 allows us to estimate the size of the
new assemblies to be approximately 1 × 4 nm, as the structure
a The ionic formula is generated by subtracting NO3 multiplied by the
charge state from the molecular formula. b The theoretical most abundant
mass was determined by MERCURY.43
the spectrum of 14. Table 2 lists the calculated and experimen-
tally determined peaks for all three cages, with the corresponding
MMAint values.
This ESI-MS information, in combination with the NMR data,
furnishes very strong evidence in favor of the formation of the
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Self-Assembly of Supramolecular Cages
A R T I C L E S
elsewhere46 prior to injection and gated trapping in the cylindrical ICR
cell.47 All mass spectra were single acquisitions acquired with 512 k
points at an ADC rate of 1 MHz. The time-domain was zero-filled
four times and Blackmann-windowed prior to fast-Fourier transform.
The mass spectra were internally mass calibrated using the monoisotopic
mass of singly charged bradykinin and triply charged glucagon. All
mass measurements were determined using the most abundant isotopes
of the 4+ charge state as this charge state was flanked by the internal
mass calibrants. The theoretical most abundant isotopic mass for the
complexes was determined using an FFT algorithm previously re-
ported.43
1,1,1-Tris(4-iodophenyl)ethane (1). 1,1,1-Triphenylethane (1000
mg, 3.87 mmol), iodobenzene diacetate (4120 mg, 12.79 mmol), and
iodine (3048 mg, 12.01 mmol) were dissolved in a mixture of acetic
acid (250 mL) and acetic anhydride (250 mL). Sulfuric acid (3 mL)
was then added, and the reaction mixture was stirred at room
temperature for 12 h, by which time the color of iodine almost entirely
disappeared. The solvent was removed on a rotary evaporator; the
residue was redissolved in chloroform and washed with saturated
aqueous Na2S2O3 and saturated aqueous NaHCO3. Column chroma-
tography (silica gel, hexanes) followed by crystallization from hexanes
provided 1 as colorless crystals. 1H NMR (CDCl3, 300 MHz): δ 7.62
(d, 6H, 3JH3-H2 ) 8.6 Hz, H3), 6.83 (d, 6H, 3JH2-H3 ) 8.6 Hz, H2), 2.07
(s, 3H, CH3). Yield 35.2%.
Figure 4. Complementary pair of isomeric cages 14 and 17.23 Donor tectons
are shown in blue, and acceptor tectons are shown in red.
of the earlier assembly was unambiguously determined by
single-crystal X-ray diffraction.23
Tris(4-iodophenyl)methylsilane (2). 1,4-Diiodobenzene (2000 mg,
6.06 mmol) was dissolved in 60 mL of dry ether and cooled to -90
°C (ether/dry ice bath), and then n-butyllithium (2.43 mL of 2.5 M
solution in hexanes, 6.06 mmol) was added to the reaction by syringe.
The reaction was allowed to warm to 0 °C over 2 h, and then it was
again cooled to -90 °C. Methyltrichlorosilane (0.214 mL, 2.02 mmol)
was added slowly by syringe; the reaction was stirred for 2 h and
allowed to warm to room temperature overnight. A white precipitate
appeared that redissolved when the reaction was washed with aqueous
NaHCO3 and then with saturated aqueous NaCl. The ethereal fractions
were dried by Na2SO4, and the crude product was purified by column
chromatography (silica gel, hexanes). 1H NMR (CDCl3, 300 MHz): δ
7.71 (d, 6H, 3JH3-H2 ) 7.8 Hz, H3), 7.16 (d, 6H, 3JH2-H3 ) 7.8 Hz, H2),
0.77 (s, 3H, CH3). Yield 39.8%.
Conclusion
The formation of the supramolecular prisms (14-16) has once
again proven the versatility and modularity of the directional
bonding approach to self-assembly. For the first time, tetrahedral
silicon and phosphorus were used as precisely positioned
structure-defining elements in supramolecular cages, which may
make them of relevance to materials science. Moreover, several
heretofore-unknown molecular building blocks - three acceptor
tripods and a donor “clip” - have been utilized in assembling
these prisms. Altogether, a number of diverse three-dimensional
structures that maintain common geometric features were
produced, allowing a unique opportunity to study the structure-
property relationships in self-assembled cages.
General Procedure for the Preparation of Compounds 4-6. A
50-mL Schlenk flask was charged under nitrogen with the appropriate
aromatic halide (1-3) and 4 equiv of Pt(PEt3)4. Freshly distilled toluene
(45 mL) was added to the flask under nitrogen by syringe, and the
resulting bright red solution was stirred for 24 h at 45 °C (60 h at 60
°C in the case of 6) as the color of the reaction mixture was turning
yellow. The solvent was then removed in vacuo. The white micro-
crystalline residue was washed with cold methanol (4 and 5) or cold
pentane (6) (3 × 50 mL) and dried in vacuo overnight.
Experimental Section
General Methods. Tris(4-bromo)triphenylphosphine oxide (3),38
1,1,1-triphenylethane,44 and Pt(PEt3)4 were prepared according to
45
known procedures. n-Butyllithium (2.5 M solution in hexanes), iodine,
and silver nitrate were purchased from Fisher; the deuterated solvents
were purchased from CIL; other reagents were purchased from Aldrich
and used without purification unless specified otherwise. All NMR
spectra were recorded on Varian Unity 300 or Varian XL-300
spectrometers. The 1H chemical shifts are reported relative to the
residual protons of deuterated dichloromethane (δ 5.32 ppm) or, when
CD2Cl2 was not used, relative to the residual protons of deuterated
acetone (δ 2.05 ppm). The 31P chemical shifts are reported relative to
an external, unlocked sample of H3PO4 (δ 0.0 ppm). Elemental analyses
were performed by Atlantic Microlab, Norcross, GA.
1,1,1-Tris[4-(trans-Pt(PEt3)2I)phenyl]ethane (4). 1H NMR (CDCl3,
3
3
300 MHz): δ 7.11 (d, 6H, JH3-H2 ) 8.0 Hz, JH3-Pt ) 67 Hz, H3),
3
6.66 (d, 6H, JH2-H3 ) 8.0 Hz, H2), 2.06 (s, 3H, C-CH3), 1.81 (m,
36H, CH2CH3), 1.04 (m, 54H, CH2CH3). 31P{1H} NMR (CD2Cl2, 121.4
1
MHz): δ 11.7 (s, JPPt ) 2749 Hz). Yield 72.1%.
Tris[4-(trans-Pt(PEt3)2I)phenyl]methylsilane (5). 1H NMR
(CD2Cl2, 300 MHz): δ 7.28 (d, 6H, JH3-H2 ) 8.0 Hz, JH3-Pt ) 67
3
3
3
Hz, H3), 6.98 (d, 6H, JH2-H3 ) 8.0 Hz, H2), 1.8 (m, 36H, CH2CH3),
ESI Mass Spectrometry. Mass spectra of cages 14-16 were
acquired in the positive-ion mode using a modified ESI-FT-ICR mass
spectrometer (IonSpec Inc., Irvine, CA) with a 7 T superconducting
magnet (Cryomagnetics, Oak Ridge, TN). ESI infusion was performed
using a Harvard syringe pump, model PHD 2000, at a flow rate of 3.3
nL/s through a 20 µL gastight Hamilton syringe held at a potential of
∼+2 keV. Analyte ions and internal mass calibrant were accumulated
externally in a rf-only hexapole using a novel dual ESI source detailed
1.05 (m, 54H, CH2CH3), 0.74 (s, 3H, Si-CH3). 31P{1H} NMR
1
(CD2Cl2, 121.4 MHz): δ 9.25 (s, JPPt ) 2741 Hz). Yield 56.3%.
Tris[4-(trans-Pt(PEt3)2Br)phenyl]phosphine Oxide (6). 1H NMR
3
4
(CD2Cl2, 300 MHz): δ 7.43 (dd, 6H, JH3-H2 ) 8.1 Hz, JH3-Pcentral
)
2.8 Hz, 3JH3-Pt ) 66 Hz, H3), 7.02 (dd, 6H, 3JH2-H3 ) 8.1 Hz, 3JH2-Pcentral
) 11.8 Hz, H2), 1.7 (m, 36H, CH2CH3), 1.05 (m, 54H, CH2CH3).
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(43) Rockwood, A. L.; Vanorden, S. L. Anal. Chem. 1996, 68, 2027-2030.
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J. AM. CHEM. SOC. VOL. 125, NO. 32, 2003 9651

A R T I C L E S
Kryschenko et al.
31P{1H} NMR (CD2Cl2, 121.4 MHz): δ 30.9 (broad s, Pcentral), 13.2
(d, JPP ) 1.6 Hz, JPPt ) 2968 Hz, PEt3). Yield 66.4%.
General Procedure for the Preparation of Compounds 14-16.
A solution of the appropriate platinum(II) nitrate (7-9) in 1 mL of
acetone-d6 was added to a 1.5-dram vial containing a weighted sample
of 13 (1.5 equiv) and a stirring bar, and then 1 mL of D2O was added
to the reaction vial. The reaction was stirred for 4 h, upon which 13
was completely dissolved and the reaction mixture attained a yellow
color.
6
1
General Procedure for the Preparation of Compounds 7-10. The
appropriate platinum(II) halide 4-6 and a large excess (10-20 equiv)
of AgNO3 (AgOSO2CF3 in the case of 10) were placed in a 2-dram (8
g) vial followed by 3 mL of dichloromethane. The reaction was stirred
in the dark at room temperature for 24 h. A clear solution with a heavy
creamy precipitate resulted; the vial was centrifuged, and the leftover
precipitate was filtered off; after that, the solvent was removed under
a flow of nitrogen. The residue was redissolved in a minimal amount
of dichloromethane, and then n-pentane was carefully added to
precipitate the residual silver salts, but not the product. The cloudy
solution that resulted was filtered through a glass fiber filter, and the
product was then precipitated by the addition of more n-pentane. The
supernatant was decanted, and the product was dried in vacuo overnight.
1,1,1-Tris[4-(trans-Pt(PEt3)2(NO3))phenyl]ethane (7). 1H NMR
(CDCl3, 300 MHz): δ 7.13 (d, 6H, 3JH3-H2 ) 8.2 Hz, 3JH3-Pt ) 64 Hz,
Bicyclo[tris[1,8-bis(4-pyridylethynyl)anthracene]bis[1,1,1-tris[4-
(trans-Pt(PEt3)2(NO3))phenyl]ethane]] (14). 1H NMR (50% D2O/
acetone-d6, 300 MHz): δ 9.27 (s, 3H, H9), 8.81 (d, 12H, 3JHRHâ ) 6.6
3
Hz, HR), 8.80 (s, 3H, H10), 8.31 (d, 6H, JHH ) 8.9 Hz, H4 and
3
3
H5), 8.11 (d, 6H, JHH ) 7.0 Hz, H2 and H7), 8.00 (d, 12H, JHâHR
)
3
3
6.6 Hz, Hâ), 7.66 (dd, 6H, JHH ) 8.9 Hz, JHH ) 7.0 Hz, H3 and
H6), 7.22 (d, 12H, 3JH3H2 ) 8.3 Hz, H3tripod), 6.75 (d, 12H, 3JH2H3 ) 8.3
Hz, H2tripod), 2.12 (s, 6H, C-CH3), 1.41 (m, 72H, CH2CH3), 1.09 (m,
108H, CH2CH3). 31P{1H} NMR (50% D2O/acetone-d6, 121.4
1
MHz): δ 13.7 (s, JPPt ) 2682 Hz). Yield 96%. Anal. Calcd for
3
H3), 6.59 (d, 6H, JH2-H3 ) 8.2 Hz, H2), 2.04 (s, 3H, C-CH3), 1.54
C196H258N12O18P12Pt6: C, 51.04; H, 5.64; N, 3.64. Found: C, 50.75;
H, 5.64; N, 3.55.
Bicyclo[tris[1,8-bis(4-pyridylethynyl)anthracene]bis[tris[4-(trans-
Pt(PEt3)2(NO3))phenyl]methylsilane]] (15). 1H NMR (50% D2O/
(m, 36H, CH2CH3), 1.12 (m, 54H, CH2CH3). 31P{1H} NMR (CD2Cl2,
1
121.4 MHz): δ 19.6 (s, JPPt ) 2902 Hz). Yield 92.5%.
Tris[4-(trans-Pt(PEt3)2(NO3))phenyl]methylsilane (8). H NMR
1
(CDCl3, 300 MHz): δ 7.27 (d, 6H, 3JH3-H2 ) 7.9 Hz, 3JH3-Pt ) 64 Hz,
H3), 6.92 (d, 6H, 3JH2-H3 ) 7.9 Hz, H2), 1.52 (m, 36H, CH2CH3), 1.11
(m, 54H, CH2CH3), 0.69 (s, 3H, Si-CH3). 31P{1H} NMR (CD2Cl2,
acetone-d6, 300 MHz): δ 9.23 (s, 3H, H9), 8.84 (d, 12H, JHRHâ
)
3
3
6.6 Hz, HR), 8.79 (s, 3H, H10), 8.31 (d, 6H, JHH ) 8.7 Hz, H4 and
3
3
H5), 8.11 (d, 6H, JHH ) 6.8 Hz, H2 and H7), 8.00 (d, 12H, JHâHR
)
1
3
3
121.4 MHz): δ 19.8 (s, JPPt ) 2895 Hz). Yield 90.9%.
6.6 Hz, Hâ), 7.66 (dd, 6H, JHH ) 8.7 Hz, JHH ) 6.8 Hz, H3 and
Tris[4-(trans-Pt(PEt3)2(NO3))phenyl]phosphine Oxide (9). 1H
NMR (CD2Cl2, 300 MHz): δ 7.44 (dd, 6H, 3JH3-H2 ) 8.2 Hz, 4JH3-Pcentral
H6), 7.39 (d, 12H, JH3H2 ) 7.8 Hz, H3tripod), 7.15 (d, 12H, JH2H3 )
3
3
7.8 Hz, H2tripod), 1.39 (m, 72H, CH2CH3), 1.08 (m, 108H, CH2CH3),
3
3
) 2.8 Hz, JH3-Pt ) 66 Hz, H3), 7.03 (dd, 6H, JH2-H3 ) 8.2 Hz,
3JH2-Pcentral ) 11.8 Hz, H2), 1.54 (m, 36H, CH2CH3), 1.12 (m, 54H,
CH2CH3). 31P{1H} NMR (CD2Cl2, 121.4 MHz): δ 30.7 (broad s, Pcentral),
0.80 (s, 6H, Si-CH3). 31P{1H} NMR (50% D2O/acetone-d6, 121.4
1
MHz): δ 14.0 (s, JPPt ) 2676 Hz). Yield 98%. Anal. Calcd for
C194H258N12O18P12Pt6Si2: C, 50.17; H, 5.60; N, 3.62. Found: C, 49.80;
6
1
19.2 (d, JPP ) 1.4 Hz, JPPt ) 2852 Hz, PEt3). Yield 89.6%.
Tris[4-(trans-Pt(PEt3)2(OSO2CF3))phenyl]methylsilane (10). 1H
NMR (acetone-d6, 300 MHz): δ 7.43 (d, 6H, 3JH3H2 ) 7.1 Hz, 3JH3-Pt
H, 5.63; N, 3.56.
Bicyclo[tris[1,8-bis(4-pyridylethynyl)anthracene]bis[tris[4-(trans-
Pt(PEt3)2(NO3))phenyl]phosphine oxide]] (16). 1H NMR (50% D2O/
acetone-d6, 300 MHz): δ 9.22 (s, 3H, H9), 8.87 (d, 12H, 3JHRHâ ) 6.6
3
) 67 Hz, H3), 7.09 (d, 6H, JH2H3 ) 7.1 Hz, H2), 1.6 (m, 36H,
CH2CH3), 1.18 (m, 54H, CH2CH3), 0.76 (s, 3H, Si-CH3). 31P{1H}
Hz, HR), 8.80 (s, 3H, H10), 8.31 (d, 6H, JHH ) 8.7 Hz, H4 and H5),
3
1
3
3
NMR (acetone-d6, 121.4 MHz): δ 20.8 (broad s, JPPt ) 2832 Hz),
19.6 (s, JPPt ) 2793 Hz). Yield 87.0%.
8.12 (d, 6H, JHH ) 6.8 Hz, H2 and H7), 8.01 (d, 12H, JHâHR ) 6.6
1
3
Hz, Hâ), 7.63 (m, 18H, H3, H6, and H3tripod), 7.30 (dd, 12H, JH2H3 )
4
1,8-Bis(4-pyridylethynyl)anthracene (13). 1,8-Diethynylanthracene
12 (1800 mg, 7.95 mmol) was placed in a 100-mL Schlenk flask along
with 4-bromopyridine hydrochloride (3246 mg, 16.7 mmol), (Ph3P)2-
PdCl2 (10 mg), and CuI (20 mg). Diethylamine (80 mL) was distilled
under nitrogen directly into the reaction flask, and the reaction was
stirred in the dark at room temperature for 2 days. The solvent was
then removed in vacuo; the residue was redissolved in dichloromethane,
washed with water, and then washed with saturated aqueous NaCl. The
organic fraction was dried with Na2SO4, filtered through a silica gel
plug, and then the solvent was removed on a rotary evaporator to
produce 13 as a dark yellow microcrystalline solid. XRD quality single
crystals were grown by slow vapor diffusion of hexanes into a
8.2 Hz, JH-Pcentral ) 11.8 Hz, H2tripod), 1.39 (m, 72H, CH2CH3), 1.09
(m, 108H, CH2CH3). 31P{1H} NMR (50% D2O/acetone-d6, 121.4
6
1
MHz): δ 31.2 (broad s, Pcentral), 13.5 (d, JPP ) 1.1 Hz, JPPt ) 2630
Hz, PEt3). Yield 98%. Anal. Calcd for C192H252N12O20P14Pt66‚
6H2O: C, 48.44; H, 5.59; N, 3.53. Found: C, 48.43; H, 5.63; N, 3.44.
Acknowledgment. Financial support from the National Sci-
ence Foundation (CHE-9818472) and the National Institutes of
Health (5R01GM57052) is gratefully acknowledged.
Supporting Information Available: Crystallographic data for
4, 6, 10, and 13 (CIF), NMR spectra (1H and 31P) for 14, 15,
and 16, and ESI-FT-ICR mass spectra for 15 and 16 with
1
expansion displaying isotope distributions of [M - 4NO3]4+
-
chloroform solution of 13. H NMR (CDCl3, 300 MHz): δ 9.47 (s,
1H, H9), 8.53 (s, 1H, H10), 8.52 (d, 4H, 3JHRHâ ) 4.5 Hz, HR-Py), 8.09
(d, 2H, 3JHH ) 8.3 Hz, H4 and H5), 7.86 (d, 2H, 3JHH ) 6.7 Hz, H2 and
H7), 7.52 (dd, 2H, 3JHH ) 6.7 Hz, 3JHH ) 8.3 Hz, H3 and H6), 7.40 (d,
peaks (PDF). This material is available free of charge via the
Internet at http://pubs.acs.org.
3
4H, JHRHâ ) 4.5 Hz, Hâ-Py). Yield 82.0%.
JA030209N
9
9652 J. AM. CHEM. SOC. VOL. 125, NO. 32, 2003