Tripodal Ru(II) complexes with conjugated and non-conjugated rigid-rod bridges for semiconductor nanoparticles sensitization

Article abstract of DOI:10.1016/j.tet.2004.06.124

Three tripodal Ru(II)-polypyridyl complexes have been synthesized as models to study long-range electron transfer in TiO₂ semiconductor nanoparticles thin films, in particular to study the effect of the conjugation of the bridge containing the

Full text of DOI:10.1016/j.tet.2004.06.124

Tetrahedron 60 (2004) 8497–8508
Tripodal Ru(II) complexes with conjugated and non-conjugated
rigid-rod bridges for semiconductor nanoparticles sensitization
*
Qian Wei and Elena Galoppini
Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ 07102, USA
Received 3 March 2004; revised 5 June 2004; accepted 29 June 2004
Available online 31 July 2004
Abstract—Three tripodal Ru(II)-polypyridyl complexes have been synthesized as models to study long-range electron transfer in TiO2
semiconductor nanoparticles thin films, in particular to study the effect of the conjugation of the bridge containing the Ru complex and for
distance dependence studies. The tripodal sensitizers, which are 1,3,5,7-tetraphenyladamantane derivatives having three COOMe anchoring
˚
groups and one rigid-rod bridge substituted with a Ru(II) complex, are the longest prepared to date (Ru-to-footprint distance w24 A). Two
have a rigid-rod bridge made of two p-ethynylphenylene units (Ph-E)2 capped with a 4-2,20-bipyridyl (bpy) ligand or a 5-1,10-
phenanthrolinyl (phen) ligand for the Ru complex. The third tripod, which contains a bpy ligand for the Ru complex, has one
bicyclo[2.2.2]octylene (Bco) unit in place of a p-phenylene (Ph) unit and is the first example of a tripodal sensitizer with a non-conjugated
bridge.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
phenylene (Ph-E) unit as the bridge carrying Ru-polypyridyl
complexes.2b–d These molecules are rigid and stand
perpendicularly to the surface when all three COOR
anchoring groups are bound. Because of this binding
geometry, the distance of the Ru complex from the
semiconductor is fixed, and tripodal sensitizers are useful
models to study interfacial electron transfer processes.
The photoexcitation of dyes covalently bound to TiO2
nanoparticles thin films is an important step in dye-
sensitized (Gratzel) solar cells and other optoelectronic
¨
systems based on wide band gap semiconductors.1 Poly-
pyridine complexes of Ru(II), the classical photosensitizing
dyes for solar cells, are generally bound to the TiO2
nanoparticles through anchoring groups directly attached on
one or more ligands. Carboxylate (COOR) or phosphonate
(PO(OR)2) groups are frequently used for this purpose
because they form strong bonds with TiO2 surfaces.1a To
bind the sensitizers, we2 and others3,4 have developed rigid
linkers that have the shape of tripods and rigid-rods.5 The
design of linkers of varying complexity for the function-
alization of semiconductor nanoparticle is a recent and
promising development in this field.6
For clarity, in this paper we call bridge (b) the moiety that is
placed between the anchoring groups (A) and the chromo-
phore or sensitizer (S), and tripodal linker the molecule that
contains both the bridge and the anchoring groups, as shown
in Figure 1. Tripodal sensitizer, or tripod, is the tripodal
linker capped with the Ru complex. We reported the study
of tripodal sensitizers based on tetraphenylmethane and
1,3,5,7-tetraphenyladamantane, and having one p-ethynyl-
Figure 1. Schematic representation of the components of a tripodal
sensitizer bound to a TiO2 nanoparticle. These are: the sensitizing
chromophore (S) and the tripodal linker, containing a rigid-rod bridge (b)
and three anchoring groups (A).
Keywords: Titanium dioxide; Sensitization; ruthenium complexes; Tripods.
* Corresponding author. Tel.: C1-973-353-5317; fax: C1-973-353-1264;
e-mail: galoppin@andromeda.rutgers.edu
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.06.124

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Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
The Ru-to-footprint distance (d) in our previous series of
2
tripods was 15–18 A. In this paper we report the synthesis
and characterization of the longest (dZ24 A) tripods
interfacial electron injection. To probe this effect, we have
now prepared 3, which contains a non-conjugated bridge.
˚
˚
prepared to date and the first example of a tripodal sensitizer
with a non-conjugated bridge (1, 2 and 3 in Figure 2). Both 1
and 2 contain a bridge made of two p-ethynylphenylene
units, (Ph-E)2, but differ in the ligands for the Ru complex (a
phen ligand in 1 and a bpy ligand in 2). Tripod 3 is
analogous to the bpy-based 2, but contains a bicyclo[2.2.2]-
octylene unit (Bco) in the bridge in place of a p-phenylene
(Ph) unit.7
Hydrocarbon cage compounds that have been used to
prepare non-conjugated bridges connecting an electron
donor–acceptor12 pair include cubane,13 stellane,14
adamantane,15 [n]staffanes16 and bicyclo[2.2.2]octane.17,18
The use of rigid-rod molecules for this purpose has been
reviewed.19 We selected to incorporate one bicyclo[2.2.2]-
octylene unit in the bridge because it is an excellent
insulator of electronic effects,17c as shown by a comparison
of the LUMO delocalization in the bridges of 2 and 3
(Figure 3).
The study of tripodal Ru-polypyridyl sensitizers bound to
TiO2 thin films has shown that the metal-to-ligand charge
transfer (MLCT) excited state is localized on the bpy ligand
attached to the bridge and that the bridge conjugation can
At the same time, the replacement of a Ph with a Bco does
not significantly change the length of the molecule (Figure 2,
inset). These properties make 3 an ideal model to study the
bridge conjugation effect on the rate of electron injection.
Also, models 1–3 will be useful, together with other tripods,
in distance dependence studies to investigate the mechan-
ism(s) for the electron injection. In this paper we report the
syntheses of 1 and 2 (for which we had reported preliminary
data but not the synthesis) and the new model 3 through two
different routes.
influence the electron injection process.2 This is not
8a–c
surprising, as the influence of (Ph-E)n
groups and other
conjugated substituents8d,9e on the photophysical properties
of Ru-polypyridyl complexes has been demonstrated. We
observed this effect in the interfacial charge injection in 1
and 2 bound to TiO2 thin films (1/TiO2 and 2/TiO2).2a The
electron injection in Ru complexes that are directly bound to
the surface, for instance Ru(dcb)(bpy)22C,7 occurs in t!
80 fs.1a,9 As expected, slower rates were observed in 1/TiO2
and 2/TiO2.2a The kinetics were fit using bi-exponential
decays,1,9,10 with 1 injecting faster than 2. In both cases,
there was a slow (tw3 ps) component ascribed to the long-
range injection, together with a sub-picosecond component
(tw240 fs for 1/TiO2 and w450 fs for 2/TiO2).2a The
ultrafast component was rationalized considering the
extensive p-conjugation of the bridge. The faster injection
exhibited by the phen-based 1/TiO2 with respect to the bpy-
based 2/TiO2 was attributed to the stronger electronic
coupling between the phen ligand and the bridge.2a,11 In
summary, the study of 1 and 2 reinforced the concept that
the conjugated bridge plays an important role in the
2. Synthesis
Scheme 1 shows the two synthetic routes employed. The
key step in both routes, step 1, involves the monosubsti-
tution of a tetrahedral precursor (I) to prepare a derivative
having one group different from the other three. Since this is
a statistical step, it requires a separation. The alkyne of the
tripodal linker (II) is capped with the chromophore in the
last step, so that a variety of tripodal sensitizers (III) can be
prepared from this intermediate.
Figure 2. Tripodal sensitizers 1, 2 and 3. The counterion is PFK2 in all cases. Note the phen ligand in 1 and bpy ligand in 2. Tripod 3 contains a Bco unit that
retains the axial symmetry and has the same length as a Ph unit (inset). The distance (d) of the Ru center to the footprint (the plane defined by the three surface-
7
˚
bound oxygen atoms) in 1–3 is 24 A.

Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
8499
monosubstituted 6a or 6b, respectively, in a Sonogashira
cross-coupling reaction (Scheme 2).23,24 Both mono-
deprotected alkynes 5a and 5b were prepared from the
corresponding 1,4-bis(trimethylsilyl)ethynes, using 1 equiv.
of MeLi$LiBr complex as the nucleophile.5b,25 The reaction
was performed at K78 8C for 5a and at rt for 5b. In both
cases the crude material was a 1:1 mixture (GC/MS) of the
monodeprotected compound and the starting material, with
only traces of dialkyne. After this mixture was employed in
the cross-coupling step, the unreacted 1,4-bis(trimethyl-
silyl)ethyne was easily isolated in pure form and used again.
The Sonogashira conditions that we had used previously2d
(Pd(PPh3)2Cl2/CuI/i-Pr2NH) resulted in almost complete
dimerization of 5a or 5b. Dimerization of the alkyne, a
common side reaction in Sonogashira reactions, is not a
problem when the alkyne is added in large excess. In this
case, 5a and 5b are added in equimolar amount to 4, and 5b
is not expendable because it is prepared via a multistep
synthesis.20,21 Our experience with the synthesis of rigid-
rod sensitizers prepared from 5a and methyl 5-bromo-1,3-
benzenedicarboxylate5b indicated that the use of Pd(dba)2/
CuI/PPh3 under argon minimizes the dimerization of 5a. By
employing these conditions we were able to prepare 6a and
6b in 28–36% yields and to inhibit the dimerization
(Table 1, entries 2 and 5).
Figure 3. LUMO of a bpy-E-Bco-E-Ph bridge (top) and of a bpy-E-Ph-E-
Ph bridge (bottom) connected to the adamantane core of the tripod (Spartan
‘02, Wavefunction, Inc.).
In Route A the rigid-rod bridge is introduced via cross-
coupling in step 1 and the three remaining iodine groups are
converted into anchoring groups via metal–halogen
exchange and carboxylation in step 2. This order is reversed
in route B. A potentially useful aspect of this reversal is that
steps 2 and 3 can be combined by performing the cross-
coupling with an ethynyl bridge carrying the chromophore
(Scheme 1, dashed arrow).20 Also, since the tricarboxylation
is performed first, the bridge (with or without the
chromophore) can be attached in a non-statistical cross-
coupling to form II, thereby minimizing the loss of the
valuable rigid-rod bridge. Results obtained with the two
approaches are discussed below.
For the synthesis of 6b, we also used the cross-coupling
procedure reported by Albinsson and coworkers (Table 1,
entry 4),18 but in our case the purification of the product was
not practical. Although 4 and alkyne 5a or 5b were reacted
in equimolar ratio, the step is statistical and di- and tri-
substituted products and unreacted 4 were recovered
together with monosubstituted 6a or 6b. The mono-
substituted products 6a and 6b were both isolated in this
step for characterization purposes. For preparative purposes,
however, it is easier to remove unreacted 4 from the crude
material and use this purified mixture in the following step.
The di- and tri- substituted products are useful inter-
mediates, and we are pursuing their conversion into di- and
tri-chromophoric antennas. Metal–halogen exchange with
t-BuLi followed by quenching with CO2 and acidification
afforded the acids 7a (or 7b), which are insoluble materials.
Treatment with diazomethane and purification of the more
soluble esters by column chromatography (or separation if
the carboxylation is performed on the statistical mixture
Route A (Schemes 2 and 3) follows the same sequence
reported to prepare shorter tripods,2c but the use of longer
bridges required different conditions in the first and last
steps of the synthesis. In general, we observed that cross-
coupling reactions proceeded in lower yields or were more
sluggish as the size of the tripodal linker or of the bridge
increased.
In the first step, 1,3,5,7-tetrakis(4-iodophenyl)-adaman-
tane21 (4) was reacted with 1-ethynyl-4-trimethylsilyl-
ethynyl-benzene (5a)5b or 1-ethynyl-4-trimethyl-
silylethynyl-bicyclo[2.2.2]octane (5b),22 to afford
Scheme 1.

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Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
Scheme 2.
from the first step) afforded tricarboxylic esters 8a or 8b.
The TMS-alkyne was deprotected using n-Bu4NF to form
two different cross-coupling procedures in the last step
(Scheme 3a).
1
alkyne 9a or 9b. The yield from 6a or 6b is 30–45%. H
A Suzuki-type reaction26 was employed to react 9a with
4-bromo-2,20-bipyridine27 or 5-bromo-1,10-phenanthro-
line28 to afford 11 and 10, respectively. This procedure
involves deprotonation of the alkyne, treatment with
B-methoxy-9-BBN and then cross-coupling of the resulting
NMR spectra showed a significant upfield shift of the alkyne
proton in 9b (dH (C^CH)Z2.10 ppm) compared to 9a (dH
(C^CH)Z3.17 ppm) suggesting that the terminal alkyne
on the Bco unit is less acidic. This observation may account
for the significantly lower reactivity of 9b, and the need for

Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
8501
Scheme 3.
ethynylboronate with the aryl halide in the presence of Pd(0)
catalyst. The Sonogashira reaction was avoided, because the
presence of Cu(I) leads to the dimerization of 9a. The non-
conjugated ethyne 9b, however, did not react in Suzuki
conditions. The cross-coupling of 9b required Sonogashira
conditions and the more reactive 4-iodo-2,20-bipyridine29
(Scheme 3b). Tripodal linker 12 could be obtained only in
this way, albeit only in 28% yields and with substantial
dimerization of 9b. Finally, the tripodal Ru(II) complexes 1,
2 and 3 were prepared from the phen- or bpy-substituted
tripodal linkers 10, 11 and 12, respectively.
Given our interest in tripodal sensitizers, we tested a
potentially shorter route in which the anchoring groups are
introduced first (Scheme 1, Route B). Carboxylation of 4
afforded a mixture of mono-, di- and tri-substituted esters.

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Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
Table 1. Reaction conditions for the cross-coupling reaction of 4 with alkyne 5a or 5ba
Entry
Alkyneb
Amine
Et3Nc
Catalysts
Solvent
Product yield (%)
Dimer of 5a or 5b
yield (%)
1
2
3
4
5
5a
5a
5a
5b
5b
Pd(dba)2, PPh3, CuI
Pd(dba)2, PPh3, CuI
Pd(dba)2, PPh3, CuI
Pd(PPh3)4
Benzene/THF
Benzene/THF
Benzene/THF
Piperidined
THF
6a 30
6a 36
6a Traces
6b 23e
6b 28
15
10
34
25
20
i-Pr2NHc
i-Pr2NEtc
Piperidined
i-Pr2NHc
Pd(dba)2, PPh3, CuI
a
All reactions were performed at room temperature.
b
c
d
e
The alkyne was added in 1–1.2 equiv. Any increase leads to more dimer.
The amine was added in 20% excess with respect to 4.
The amine was used as the solvent.
Piperidine was distilled in vacuo from the crude material.
Separation of this statistical mixture afforded 13, which has
one iodine available for the cross-coupling and three
COOMe anchoring groups, in 15–20% yield from 4
(Scheme 4).
13. The tripodal sensitizer 3 was prepared from 9b using the
same procedures shown in Scheme 2.
In conclusion, Route B yielded 3 in the same overall yield as
Route A (w6% for route A and w6–8% for route B). The
main advantage is that the cross-coupling step proceeds in
higher yields (40%) and without wasting the precious bridge
in a statistical reaction. We are currently improving this
route and the use of a chromophore-substituted alkyne, as
suggested in Scheme 1 (dashed line), is being explored.
Although we could not separate compound 13 from an
impurity, 14, (See Supplementary data),30 this crude
material was used in the cross-coupling step with 5b and
unreacted 14 was separated from the product afterwards.
Monosubstituted 9b was thus obtained in w40% yield from
Scheme 4.

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8503
Table 2. Absorption and fluorescence data for CH3CN solutions of 1–3 and reference complexes
Entry
Sensitizer
labs (nm) (3, MK1 cmK1
)
alF (nm)
t (ms)
fF!10K2
1
2
3
4
5
1
2
3
449 (2.3 !104)
463 (2.8 !104)
456 (1.6 !104)
450
606
638
624
620
626
1.4
2.2
1.6
10
12
14
bRu(bpy)2(phen)2C
bRu(bpy)23C
452
0.8b
a
The solutions were de-oxygenated by freeze-pump-thaw. lexZ450 nm.
From Ref. 2b, in acetonitrile.
b
3. Solution photophysical properties of 1–3
more useful that the method reported before. The bridge
carrying the chromophore is conjugated in phen-based 1 and
bpy-based 2, and carries a bicyclo[2.2.2]octylene unit in
The solution absorption and fluorescence data of tripodal
sensitizers 1–3 are reported in Table 2, together with two
reference complexes. A comparison of the absorption
spectra between the bpy-based tripodal complexes 2 and
3, shown in Figure 4, clearly shows an effect due to
differences in the bridge structure.
2a
bpy-based 3. The photophysical study of 1/TiO2 and
2/TiO22a, and the shorter tripods2b–d had suggested that the
conjugated bridges influence the interfacial kinetic pro-
cesses, and the models described here will allow to fully test
this hypothesis.
The visible absorption spectra of 2 and 3 both displayed the
broad band typical of the MLCT excited state at w450 nm,
while the p/p* ligand-centered band at w350 nm is
present only in the spectrum of the bpy-tripod with the
conjugated bridge (2) (Figure 4). The MLCT band for 2 was
centered at 463 nm and red-shifted with respect to the same
band in the spectrum of the bpy-tripod with the non-
conjugated bridge (3) and of the reference Ru(bpy)3. This
shift was observed in the rt fluorescence spectra (Table 2).
Specifically, the fluorescence spectrum of the bpy-based
tripod with the conjugated bridge 2 was about 14 nm red-
shifted with respect to the spectrum of the corresponding
tripod with the Bco unit in the bridge, 3, and of the reference
Ru(bpy)23C (Table 2, entries 2, 3 and 5).
5. Experimental
5.1. General experimental methods
Instrumentation. H (499.90 MHz) and 13C (124.98 MHz)
NMR spectra were obtained on a Varian INOVA 500
spectrometer and recorded in CDCl3 unless otherwise noted.
The H spectra were referenced to Me4Si, or to residual
1
1
CHCl3 (7.27 ppm) for the compounds containing the TMS
group. The 13C spectra were referenced to the central line of
the solvent. Chemical shifts (d) are given in parts per million
(ppm) and reported to a precision of G0.01 ppm. Proton
coupling constants (J) are given in Hz and reported to a
precision of G0.1 Hz. High-resolution mass spectra (FAB-
MS) and elemental analyses were obtained from commer-
cial facilities. UV–vis absorbance data were collected on a
VARIAN Cary-500 spectrophotometer, and photolumines-
cence (PL) measurements were performed on a VARIAN
Cary-Eclipse Fluorescence Spectrophotometer. Measure-
ments were run in CH3CN in 1 cm quartz cuvettes. The
solvent for the fluorescence spectra was de-oxygenated by
three cycles of freeze-pump-thaw or by bubbling solvent-
saturated nitrogen. The solutions were 0.005 mM (2) and
0.015 mM (3) in acetonitrile for the fluorescence spectra and
0.02 mM (2 and 3) for the absorption spectra. IR spectra
were performed on a Mattson Research Series 1 FT-IR
(KBr).
4. Summary
˚
We have described the synthesis of three long (dZ24 A)
tripodal Ru-polypyridyl sensitizers (1–3) via two synthetic
routes. Although the overall yields from both routes are low,
the compounds are of interest to study the effect of the
bridging unit in electron transfer studies at nanoparticle
interfaces, and the ‘reversal’ route B tested here may prove
Materials and general procedures. All reactions were
performed under nitrogen or argon atmosphere with
glassware oven-dried and then flamed in vacuo unless
otherwise specified. Column chromatography was per-
formed using silica gel (40 mm average particle size). Thin
layer chromatography (TLC) was performed using silica gel
plates with fluorescent indicator and UV light as detection
method. Phosphomolybdic 10% ethanolic solution and heat
or iodine vapors were used as developing agents for
compounds that do not absorb in the UV–vis (for instance
5b). ‘Standard workup’ in the synthetic procedures refers to
the following sequence: (a) the aqueous layer is extracted
with the indicated solvent three times; (b) the organic layers
are collected and dried over Na2SO4 anhyd; (c) the solvent
is evaporated in vacuo on a rotary evaporator. Monoglyme
Figure 4. Absorption spectra of acetonitrile solutions of Ru(bpy)2
(AdTripod-(Ph-E)2-bpy)2C 2 (—) and Ru(bpy)2(AdTripod-Ph-E-Bco-E-
bpy)2C 3 (- - -).

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Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
(1,2-dimethoxyethane) was distilled over sodium/benzo-
phenone ketyl. THF (purchased anhydrous grade) was
distilled over sodium/benzophenone ketyl. Benzene was
distilled over sodium/benzophenone ketyl, CH2Cl2 was
distilled over CaH2, CBr4 was recrystallized from ethanol
and PPh3 from hexane. We observed improved yields when
we used CO2(g) from a lecture bottle rather than generated
from dry ice. Pd(0) catalysts were stored and handled in a
glove box. The following solution reagents were purchased
from Acros or Aldrich and were not titrated prior to use:
t-BuLi (1.5 M solution in pentane), MeLi$LiBr complex
(2.2 M solution in diethyl ether), Lithium bis(trimethyl-
silyl)amide (1.0 M solution in hexane), 9-methoxy-9-
borobicyclo[3.3.3]nonane (B-methoxy-9-BBN, 1.0 M
solution in hexane), n-BuLi (1.6 M solution in hexane). 4-
Bromo-2,200-bipyridine,27 5-bromo-1,10-phenanthroline,28
6b (RfZ0.18). The mixture was separated by column
chromatography (CHCl3/hexane, 1/9) to afford 6b (170 mg,
28%). H NMR dH: 7.68 (d, 6H, JZ8.5 Hz, PhI), 7.33 (s,
1
4H), 7.2 (d, 6H, JZ8.5 Hz, PhI), 2.06 (s, 12H, CH2 (Ad)),
1.83 (d, 12H, JZ7.5 Hz, CH2 (Bco)), 0.13 (s, 9H, SiMe3).
13C NMR dC: 148.7, 148.2, 137.7, 131.8, 127.4, 124.9,
122.1, 114.1 (C^C), 96.7 (C^C), 91.9 (I-C), 83.9 (C^C),
80.5 (C^C), 46.9 (CH2(Ad)), 39.3 (C(Ad)),
32.0 (CH2(Bco)), 27.1 and 26.9 (C(Bco)), 0.5 (SiMe3). IR
(cmK1): 3032 (nC–H(Ar)), 2942 and 2863 (nC–H(aliph.)),
2155 (nC^C), 1509, 1485, 1454, 1393, 1356, 1247, 1002,
790.
5.2.3. 1,3,5-(4-Carboxyphenyl)-7-[4-(1-trimethylsilyl-
ethynyl-4-ethynyl-phenyl)phenyl]-adamantane (7a). To
a solution of 6a (580 mg, 0.57 mmol) in THF (20 mL)
cooled to K78 8C was added dropwise over 20 min t-BuLi
(5.5 mmol, 4.5 mL of a 1.5 M pentane solution). The
mixture was stirred for an additional 15 min and CO2 was
bubbled into the reaction mixture. An abundant yellow
precipitate formed. The cooling bath was removed, the
mixture was allowed to warm to rt, and water (50 mL) and
hexane (50 mL) were added. The clear aqueous layer was
separated, cooled with a water/ice bath and acidified with
w10% HCl aq. A pale yellow precipitate formed. Standard
workup with CHCl3 afforded 0.42 g of a pale yellow
powder. The crude material was used in the next step.
4-iodo-2,2 -bipyridine,29
1,3,5,7-tetrakis(4-iodo-
phenyl)adamantane 4,21 5a5b and 5b22 were synthesized
following literature procedures. CAUTION. To avoid
explosion, diazomethane was prepared using exclusively
glassware with smooth joints (Aldrich) from Diazald
(Aldrich), MeOH, and KOH aq. following described
procedures.31
5.2. Synthesis of tripodal sensitizers 1–3
5.2.1. 1,3,5-(4-Iodophenyl)-7-[4-(1-trimethylsilylethynyl-
4-ethynyl-phenyl)phenyl]-adamantane (6a). A 1:1 mix-
ture (GC/MS) of 5a5b and 1,4-bis(trimethylsilylethynyl)-
benzene (300 mg of mixture, 0.64 mmol of 5a) was added to
a solution of 421 (515 mg, 0.54 mmol) in i-Pr2NH
(0.12 mL), benzene (25 mL) and THF (25 mL) at rt,
followed by Pd(dba)2 (18 mg, 0.027 mmol), PPh3 (28 mg,
0.108 mmol), and CuI (10 mg, 0.054 mmol). The mixture
was stirred at rt under nitrogen for 24 h and filtered. TLC
(CHCl3/hexane, 10/90) showed 5 spots corresponding to:
1,4-bis(trimethylsilylethynyl)-benzene (RfZ0.95), the
dimer from 5a (RfZ0.6), 4 (RfZ0.4), 6a (RfZ0.26), di-
substituted product (RfZ0.17). The mixture was separated
by column chromatography (CHCl3/hexane, 1/9) to afford
5.2.4. 1,3,5-(4-Carboxyphenyl)-7-[4-(1-trimethylsilyl-
ethynyl-4-ethynyl-[2.2.2]bicyclooctyl)phenyl]-adaman-
tane (7b). This was prepared using the same procedure
using 6b (416 mg, 0.4 mmol) in THF (20 mL), t-BuLi
(3.8 mmol, 2.5 mL of a 1.5 M pentane solution). The pale
yellow precipitate was collected by filtration to afford
260 mg of crude material that was used in the next step.
5.2.5. 1,3,5-(4-Carbomethoxyphenyl)-7-[4-(1-trimethyl-
silylethynyl-4-ethynyl-phenyl)phenyl]-adamantane
(8a). A solution of the mixture of acids (200 mg) in ethyl
ether (10 mL) was treated with CH2N2 (see General). The
solvent was removed in vacuo and the crude material was
purified by column chromatography (AcOEt/hexane, 1/4) to
afford 110 mg of 8a (RfZ0.4) (yield from 6a w45%). Mp
196–198 8C. 1H NMR dH: 8.04 (d, 6H, JZ8.5 Hz,
PhCOOMe), 7.56 (d, 6H, JZ8.5 Hz, PhCOOMe), 7.53 (d,
2H, JZ8.5 Hz), 7.47 (d, 2H, JZ8.5 Hz), 7.45 and 7.44 (two
s, 4H), 3.91 (s, 9H, COOMe), 2.20 (s, 12H, CH2), 0.25 (s,
9H, SiMe3). 13C NMR dC: 166.9 (COOMe), 153.8, 149.0,
131.9, 131.8, 131.4, 129.8, 128.3, 125.1 (two carbons),
123.3, 122.8, 121.1, 104.6 (C^C), 96.3 (C^C), 91.1
(C^C), 89.0 (C^C), 52.1 (COOMe), 46.6 (CH2(Ad)), 39.6
and 39.3 (C(Ad)), K0.1 (SiMe3). IR (cmK1): 3037 (nC–
H(Ar)), 2951 and 2898 (nC–H(aliph.)), 2156 (nC^C),
1931.5, 1724.3 (nCZO), 1608 (nC– C(Ar)), 1512, 1436,
1406, 1358, 1281 (nC–O), 1192, 1110 (nC–O), 1018, 866,
844 (dAr), 762. Anal. calcd for C53H50O6Si: C, 78.49; H,
6.21. Found: C, 78.32, H, 6.11.
1
6a (207 mg, 36%). Mp 194–196 8C. H NMR dH: 7.68 (d,
6H, JZ9.0 Hz, PhI), 7.51 (d, 2H, JZ8.5 Hz), 7.44 (two s,
4H), 7.43 (d, 2H, JZ8.5 Hz), 7.21 (d, 6H, JZ9.0 Hz, PhI),
2.09 and 2.07 (two s, 12H, CH2(Ad)), 0.25 (s, 9H, SiMe3).
13C NMR dC: 149.1, 148.4, 137.5, 131.9, 131.7, 131.3,
127.1, 125.0, 123.3, 122.8, 121.0, 104.6 (C^C), 96.3
(C^C), 91.7 (I-C), 91.1 (–C^C–), 89.0 (–C^C–), 46.7
(CH2(Ad)), 39.2 and 39.0 (C(Ad)), K0.1 (SiMe3). Anal.
calcd for C47H41I3Si: C, 55.64; H, 4.07. Found: C, 55.33; H,
4.29.
5.2.2. 1,3,5-(4-Iodophenyl)-7-[4-(1-trimethylsilylethynyl-
4-ethynyl-[2.2.2]bicyclooctyl)phenyl]-adamantane
(6b). A 1:1 mixture (GC/MS) of 1,4-bis(trimethylsilyl-
ethynyl)-bicyclo[2.2.2]octane and 1-ethynyl-4-trimethyl-
silylethynyl-bicyclo[2.2.2]octane (5b) (342 mg,
w0.58 mmol of 5b) was added to a solution of 4 (535 mg,
0.57 mmol) in i-Pr2NH (0.12 mL) and THF (80 mL) at rt,
followed by Pd(dba)2 (18 mg, 0.028 mmol), PPh3 (28 mg,
0.108 mmol), CuI (10 mg, 0.054 mmol). The mixture was
stirred at rt for 24 h and filtered. GC/MS shows the
formation of dimer from 5b. TLC (CHCl3/hexane, 1/9)
showed three spots: two were assigned to 4 (RfZ0.35) and
5.2.6. 1,3,5-(4-Carbomethoxyphenyl)-7-[4-(1-trimethyl-
silylethynyl-4-ethynyl-[2.2.2]bicyclooctyl)phenyl]-ada-
mantane (8b). A solution of the mixture of acids (0.26 g) in
ethyl ether (10 mL) was treated with CH2N2 (see General).
TLC (AcOEt/hexane, 20/80) showed three spots, with 8b

Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
8505
RfZ0.31. The mixture was purified by silica gel column
chromatography (AcOEt/hexane, 1/4) to afford 8b as a
white powder (100 mg, yield from 6bw30%). 1H NMR dH:
8.05 (d, 6H, JZ8.5 Hz, PhCOOMe), 7.56 (d, 6H, JZ
8.5 Hz, PhCOOMe), 7.37 (s, 4H), 3.92 (s, 9H, COOMe),
2.19 (two s, 12H, CH2(Ad)), 1.84 (two s, 12H, CH2(Bco)),
0.14 (s, 9H, SiMe3). 13C NMR dC: 167.0 (COOMe), 154.1,
148.1, 131.8, 130.0, 128.4, 125.3, 124.9, 122.2, 114.0
(C^C), 96.6 (C^C), 83.9 (C^C), 80.4 (C^C), 52.3
(COOMe), 46.9 and 46.8 (CH2(Ad)), 39.8 and 39.3 (C(Ad)),
31.9 (CH2(Bco)), 27.0 and 26.9 (C(Bco)), 0.5 (SiMe3). IR
(cmK1): 2945 and 2864 (nC–H(aliph.)), 2162 (nC^C),
1724 (n CZO), 1932, 1611 (nC–C(Ar)), 1572, 1509, 1436,
1408, 1357, 1282 (nC–O), 1192, 1110 (nC–O), 1017, 961,
847 (dAr). HMRS (FAB) for C55H59O6Si, MHCZ
843.4076.
lithium bis(trimethylsilyl)amide (0.48 mmol, 0.48 mL of a
1 M hexane solution). After 30 min, B-methoxy-9-BBN
(0.48 mmol, 0.48 mL of 1 M hexane) was added. After
stirring 2 h at K78 8C, the solution was transferred via
cannula to a second flask containing Pd(PPh3)4 (36 mg,
0.03 mmol) and 5-bromo-1,10-phenanthroline28 (90 mg,
0.35 mmol) in THF (5 mL). The reaction mixture was
refluxed for 24 h, cooled to rt, and standard workup with
CH2Cl2 afforded a crude material that was purified by
column chromatography with the following sequence of
eluents: (AcOEt/hexane, 1/4), CH2Cl2, (CH2Cl2/MeOH, 95/
5) to afford 10 as a white powder (140 mg, 47%). Mp 187–
1
189 8C. H NMR dH: 9.28 (dd, 1H, JZ3.0, 1.5 Hz, phen),
9.23 (dd, 1H, JZ3.0, 1.5 Hz, phen), 8.86 (dd, 1H, JZ8.5,
1.5 Hz, phen), 8.28 (dd, 1H, JZ7.5, 1.5 Hz, phen), 8.13 (s,
1H, phen), 8.05 (d, 6H, JZ9.0 Hz, PhCOOMe), 7.78 (q, 1H,
JZ4.5 Hz, phen), 7.68 (q, 1H, JZ4.5 Hz, phen), 7.66 (d,
2H, JZ8.5 Hz), 7.56 (m, 10H), 7.50 (d, 2H, JZ8.5 Hz),
3.92 (s, 9H, COOMe), 2.21 (s, 12H, CH2(Ad)). 13C NMR
dC: 166.88 (COOMe), 153.8, 150.9, 150.6, 149.2, 145.7,
145.5, 136.1, 134.9, 131.8, 131.7 (two carbons), 130.8,
129.8, 128.3 (two carbons), 128.1, 125.1 (two carbons),
123.9, 123.6, 123.5, 122.2, 121.0, 119.8, 95.2 (C^C), 91.6
(C^C), 88.9 (C^C), 87.5 (C^C), 52.1 (COOMe), 46.7
(CH2(Ad)), 39.6 and 39.3 (C(Ad)). IR (cmK1): 3035 (nC–
H(Ar)), 2946 and 2899 (nC–H(aliph.)), 2842, 2208
(nC^C), 1930, 1721 (nCZO), 1611 (nC–C(Ar)), 1566,
1511, 1436, 1407, 1282 (nC–O), 1191, 1108 (nC–O), 1019,
835 (dAr), 766. Anal. calcd for C62H48N2O6: C, 81.20; H,
5.28; N, 3.05. Found: C, 80.62, H, 5.14, N, 2.71.
5.2.7. 1,3,5-(4-Carbomethoxyphenyl)-7-[4-(1,4-bis-
(ethynyl)phenyl)phenyl]-adamantane (9a). nBu4NF$
3H2O (540 mg, 1.72 mmol) was added to a solution of
8a (700 mg, 0.86 mmol) in CH3CN (20 mL) and benzene
(20 mL) at rt with stirring. After 1.5 h, water (20 mL) was
added. Standard workup with CH2Cl2 and purification by
column chromatography (AcOEt/hexane, 1/4) afforded 9a
as a white powder (RfZ0.3) (450 mg, Avg. yield for this
step w75%). Mp 214–216 8C. 1H NMR dH: 8.04 (d, 6H, JZ
9.0 Hz, PhCOOMe), 7.56 (d, 6H, JZ9.0 Hz, PhCOOMe),
7.54 (2H, d, JZ8.5 Hz), 7.47 (m, 6H), 3.92 (s, 9H,
COOMe), 3.17 (s, 1H, C^CH), 2.21 and 2.20 (two s,
12H, CH2(Ad)). 13C NMR dC: 166.9 (COOMe), 153.8,
149.1, 132.1, 131.8, 131.4, 129.8, 128.3, 125.1 (two
carbons), 123.7, 121.8, 121.0, 91.2 (C^C), 88.8 (C^C),
83.3 (C^C), 78.9 (C^C), 52.1 (COOMe), 46.6 (CH2(Ad)),
39.6 and 39.3 (C(Ad)). IR (cmK1): 3302 (n ^C–H), 3037
(nC–H(Ar)), 2950 and 2919 (nC–H(aliph.)), 2849, 2565
(nC^C), 2216.4 (nC^C), 1931, 1724 (nCZO), 1611
(nC–C(Ar)), 1514, 1435, 1405, 1282 (nC–O), 1191, 1111
(nC–O), 1018, 837 (dAr), 765.0. Anal. calcd for C50H42O6:
C, 81.28; H, 5.73. Found: C, 80.99, H, 5.57.
5.2.10. Ad-Tripod-(Ph-E)2-Bpy (11). Tripodal ligand 11
was prepared using the same procedure using 9a (150 mg,
0.20 mmol) in THF (5 mL), lithium bis(trimethylsilyl)-
amide (0.23 mmol, 0.23 mL of a 1 M hexane solution),
B-methoxy-9-BBN (0.23 mmol, 0.23 mL of a 1 M hexane
solution), Pd(PPh3)4 (20 mg, 0.02 mmol), 4-bromo-2,2-
bipyridine27 (89 mg, 0.38 mmol) in THF (5 mL). The
crude material was purified by silica gel column chroma-
tography with the following sequence of eluents: (AcOEt/
hexane, 1/4), CH2Cl2, (CH2Cl2/MeOH 95/5) to afford 11 as
5.2.8. 1,3,5-(4-Carbomethoxyphenyl)-7-[4-(1,4-bis-
(ethynyl)[2.2.2]bicyclooctyl)phenyl]-adamantane
(9b). This was prepared following the same procedure using
8b (81 mg, 0.09 mmol) in CH3CN (10 mL) and nBu4-
NF$3H2O (45 mg, 0.3 mmol). Column chromatography
(AcOEt/hexane, 1/4) afforded 9b as a white powder (RfZ
0.25) (53 mg, Avg. yield for this step w75%). 1H NMR dH:
8.04 (d, 6H, JZ9.0 Hz, PhCOOMe), 7.56 (d, 6H, JZ
9.0 Hz, PhCOOMe), 7.37 (d, 4H, JZ2.5 Hz), 3.92 (s, 9H,
COOMe), 2.19 (two s, 12H, CH2(Ad)), 2.10 (s, 1H,
C^CH), 1.85 (two s, 12H, CH2(Bco)). 13C NMR dC:
167.2 (COOMe), 154.1, 148.2, 131.9, 130.0, 128.5, 125.3,
125.0, 122.2, 96.5 (C^C), 91.4 (C^C), 80.6 (C^C), 68.3
(C^C), 52.3 (COOMe), 46.9 and 46.8 (CH2(Ad)), 39.8 and
39.3 (C(Ad)), 31.9 (CH2(Bco)), 26.9 and 26.3 (C(Bco)). IR
(cmK1): 3302 (n^C–H), 3056 (nC–H(Ar)), 2943 and 2865
(nC–H(aliph.)), 2224 (nC^C), 2107 (nC^C), 1932, 1724
(nCZO), 1610 (nC–C(Ar)), 1571, 1508, 1438, 1406, 1356,
1282 (nC–O), 1193, 1110 (nC–O), 1018, 967, 898, 853 (dAr),
834 (dAr). HMRS (FAB) for C52H51O6, MHCZ771.3690.
1
a white powder (108 mg, 60%). Mp 175–177 8C. H NMR
dH: 8.72 (d, 1H, JZ4.5 Hz, bpy), 8.68 (d, 1H, JZ5.5 Hz,
bpy), 8.55 (s, 1H, bpy), 8.43 (d, 1H, JZ8.0 Hz, bpy), 8.05
(d, 6H, JZ9.0 Hz, PhCOOMe), 7.84 (td, 1H, JZ8.0,
2.0 Hz, bpy), 7.57 (m, 12H), 7.49 (d, 2H, JZ8.5 Hz), 7.41
(d, 1H, JZ5.0 Hz, bpy), 7.35 (t, 1H, JZ5.5 Hz, bpy), 3.92
(9H, s, COOMe), 2.21 (s, 12H, CH2(Ad)). 13C NMR dC:
166.9 (COOMe), 156.1, 155.4, 153.8, 149.2, 149.2, 149.1,
137.1, 132.3, 131.9, 131.6, 129.8, 128.3, 125.2, 125.1,
125.0, 124.2, 124.1, 123.2, 121.9, 121.2, 121.0, 93.6
(C^C), 91.6 (C^C), 88.9 (C^C), 88.8 (C^C),
52.1 (COOMe), 46.7 (CH2(Ad)), 39.6 and 39.3 (C(Ad)).
IR (cmK1): 3058 (nC–H(Ar)), 2948, 2897 and 2843
(nC–H(aliph.)), 2207 (nC^C), 1926, 1722 (nCZO),
1610.0 (nC–C(Ar)), 1582, 1536, 1514, 1459, 1436, 1407,
1282 (nC–O), 1190, 1110 (nC–O), 1018, 836 (dAr), 761.6.
Anal. calcd for C60H48N2O6: C, 80.70; H, 5.42; N, 3.14.
Found: C, 79.98, H, 5.43, N, 2.4.
5.2.11. Ad-Tripod-Ph-E-Bco-E-Bpy (12). Terminal alkyne
9b (260 mg, 0.34 mmol) was added to a solution of 4-iodo-
2,20-bipyridine29 (115 mg, 0.4 mmol) in i-Pr2NH (0.15 mL)
5.2.9. Ad-Tripod-(Ph-E)2-Phen (10). To a solution of 9a
(235 mg, 0.32 mmol) in THF (8 mL) at K78 8C was added

8506
Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
and THF (40 mL) at rt, followed by Pd(dba)2 (15 mg,
0.02 mmol), PPh3 (21 mg, 0.08 mmol), CuI (9.5 mg,
0.04 mmol). The mixture was refluxed for 2 days, then
cooled to rt and filtered. TLC (CHCl3/MeOH, 98/2) showed
three spots: 9b (RfZ0.45), 4-iodo-2,20-bipyridine (RfZ
0.25) and 12 (RfZ0.15). The crude material was separated
by column chromatography with the following sequence of
eluents: (AcOEt/hexane, 1/4), CHCl3, (CHCl3/MeOH 98/2)
(6H, d, JZ8.5 Hz, PhCOOMe), 7.81 (6H, d, JZ8.5 Hz,
PhCOOMe), 7.74 (2H, d, JZ8.5 Hz), 7.65–7.58 (12H, m),
3.87 (9H, s, COOMe), 2.31 and 2.30 (two s, 12H, CH2(Ad)).
13C NMR dC: (CD3COCD3): 167.2 (COOMe), 158.6, 158.1,
158.0, 157.9, 157.7, 155.6, 152.9, 152.8, 152.7, 152.6,
151.6, 139.2, 139.1, 139.0, 133.1, 133.0, 132.7, 132.5,
130.3, 129.7, 129.5, 129.4, 129.1, 129.0, 128.8, 126.9,
126.6, 126.5, 125.9, 125.7, 125.4, 121.8, 121.2, 97.9
(C^C), 93.2 (C^C), 89.1 (C^C), 88.2 (C^C), 52.2
(COOMe), 47.0 and 46.9 (CH2(Ad)) 40.6 and 40.4 (C(Ad)).
IR (cm–1): 3081 (nC–H(Ar)), 2920 and 2849 (nC–H(aliph.)),
2208 (nC^C), 1718 (nCZO), 1610 (nC–C(Ar)), 1570,
1513, 1469, 1439, 1282 (nC–O), 1192, 1113 (nC–O), 841
(dAr), 763. Calcd for C80H64F12N6O6P2Ru: C, 60.19; H,
4.04; N, 5.26. Found: C, 60.13, H, 3.97, N, 5.04. HRMS
(FAB) calcd for C80H64N6O6Ru 1306.3931, found
1306.3910.
1
to afford 12 (170 mg, 28%). H NMR dH: 8.69 (d, 1H, JZ
4.5 Hz, bpy), 8.58 (d, 1H, JZ5.0 Hz, bpy), 8.39 and 8.37 (s,
2H, bpy), 8.04 (d, 6H, JZ9.0 Hz, PhCOOMe), 7.82 (td, 1H,
JZ8.0, 2.0 Hz, bpy), 7.56 (d, 6H, JZ8.5 Hz, PhCOOMe),
7.38 (s, 4H), 7.32 (t, 1H, JZ5.5 Hz, bpy), 7.25 (dd, 1H, JZ
5.0, 1.5 Hz, bpy), 3.92 (s, 9H, COOMe), 2.19 (two s, 12H,
CH2(Ad)), 1.91 (s, 12H, CH2). 13C NMR dC: 167.1
(COOMe), 156.2, 155.9, 154.1, 149.4, 149.2, 148.2, 137.2,
133.3, 131.9, 130.0, 128.5, 125.7, 125.3, 125.0, 124.1,
123.6, 122.2, 121.3, 101.8 (C^C), 96.4 (C^C), 80.6
(C^C), 79.1 (C^C), 52.3 (COOMe), 46.9 and 46.8
(CH2(Ad)), 39.8 and 39.3 (C(Ad)), 31.9 and 31.8
(CH2(Bco)), 27.2 and 27.0 (C (Bco)). IR (cmK1): 3060
(nC–H(Ar)), 2946 and 2866 (nC–H(aliph.)), 2226 (nC^C),
1931, 1724 (nCZO), 1611 (nC–C(Ar)), 1586, 1534, 1509,
1458, 1435, 1409, 1280 (nC–O), 1191, 1112 (nC–O), 1015,
841 (dAr).
5.2.14. Ru(bpy)2(Ad-Tripod-Ph-E-Bco-E-Bpy)2C 2PF6K
(3). Complex 3 was prepared using the same procedure, but
under argon, from 12 (44 mg, 0.047 mmol) in THF
(w1 mL), ethanol/water (10 mL), Ru(bpy)2Cl2$2H2O
(25 mg, 0.048 mmol) and NaPF6 to afford 53 mg of 3
(70% yield). The precipitate was very fine and tended to
form a suspension. 1H NMR dH: (CD3COCD3): 8.90 (d, 1H,
JZ8.5 Hz, bpy), 8.83 (m, 4H, bpy), 8.74 (d, 1H, JZ1.0 Hz,
bpy), 8.24 (m, 5H, bpy), 8.17 (d, 1H, JZ5.5 Hz, bpy), 8.07
(m, 10H), 7.79 (d, 6H, JZ8.5 Hz, PhCOOMe), 7.61 (m,
7H), 7.44 (dd, 1H, JZ6.0, 1.5 Hz, bpy), 7.36 (d, 2H, JZ
8.5 Hz), 3.87 (s, 9H, COOMe), 2.30 (two s, 12H, CH2(Ad)),
1.93 (s, 12H, CH2(Bco)). 13C NMR (CD3COCD3) dC: 184.3,
167.2 (COOMe), 158.4, 158.2, 158.1, 158.0, 157.8, 155.8,
152.9, 153.0, 152.8, 152.7, 139.1, 139.0, 134.2, 132.3,
130.4, 130.1, 129.1, 129.0, 128.8, 127.1, 126.5, 126.3,
125.7, 125.4, 122.5, 107.1 (C^C), 96.4 (C^C), 81.6
(C^C), 78.7 (C^C), 52.3 (COOMe), 47.2 and 47.0
(CH2(Ad)), 40.7 and 40.3 (C(Ad)), 32.3 and 32.1
(CH2(Bco)), 28.2 and 27.6 (C(Bco)). IR (cmK1): 3083
(nC–H(Ar)), 2926, 2852 (nC–H(aliph.)), 2225 (nC^C),
1924, 1718 (nCZO), 1610 (nC–C(Ar)), 1568, 1508, 1464,
1442, 1410, 1362, 1281 (nC–O), 1194, 1112 (nC–O), 1017,
842 (dAr). HRMS (FAB) calcd for C82H72O6N6F6PRu
1483.4199, found 1483.4216.
5.2.12. Ru(bpy)2(Ad-Tripod-(Ph-E)2-Phen)2C 2PF6K
(1). A solution of 10 (97 mg, 0.105 mmol) in THF (2 mL)
was added to a 1:1 mixture of ethanol/water (10 mL). To the
solution, de-oxygenated by bubbling N2 for w30 min, was
added Ru(bpy)2Cl2$2H2O (54 mg, 0.105 mmol). The mix-
ture was refluxed for 6 h under nitrogen, cooled to rt and
filtered. Addition of NaPF6 to the filtrate formed a red
precipitate, which was collected and washed with water
several times to afford 1 (130 mg, 80%). 1H NMR dH:
(CD3COCD3): 9.19 (d, 1H, JZ8.5 Hz, phen), 8.88 (d, 2H,
JZ5.0 Hz), 8.84 (t, 3H, JZ6.0 Hz), 8.70 (s, 1H, phen), 8.53
(d, 1H, JZ4.5 Hz), 8.49 (d, 1H, JZ4.5 Hz), 8.27 (m, 2H),
8.18 (m, 4H), 8.03 (d, 6H, JZ8.5 Hz, PhCOOMe), 7.96 (m,
4H), 7.80 (m, 8H), 7.76 (d, 2H, JZ8.5 Hz), 7.66 (m, 4H),
7.61 (d, 2H, JZ8.5 Hz), 7.40 (m, 2H), 3.88 (9H, s,
COOMe), 2.33 and 2.32 (12H, two s, CH2(Ad)). 13C
NMR dC: (CD3COCD3): 167.2 (COOMe), 158.4, 158.2,
155.8, 154.2, 153.1, 151.6, 148.8, 148.5, 139.1, 139.0,
137.8, 136.4, 133.1, 132.7, 132.6, 131.6, 130.3, 129.0,
128.8, 128.7, 127.9, 127.8, 126.7, 126.6 (two carbons),
125.4, 125.3, 122.5, 121.3, 98.00 (C^C), 93.0 (C^C), 89.2
(C^C), 86.8 (C^C), 52.3 (COOMe), 47.0 (CH2(Ad)), 40.7
and 40.4 (C(Ad)). IR (cmK1): 3083 (nC–H(Ar)), 2951 and
2918 (nC–H(aliph.)), 2208 (nC^C), 1930, 1719 (nCZO),
1609 (nC–C(Ar)), 1515, 1466, 1446, 1434, 1282 (nC–O),
1195, 1111 (nC–O), 1018, 842 (d(Ar)), 765. Anal. calcd for
C82H64F12N6O6P2Ru: C, 60.78; H, 3.98; N, 5.19. Found: C,
60.50, H, 3.97, N, 5.03. HRMS (FAB) calcd for
C82H64N6O6Ru 1330.3931, found 1330.3940.
5.2.15. Synthesis of 8b via Route B (Scheme 4). To a
solution of 421 (470 mg, 0.5 mmol) in THF (20 mL) cooled
to K78 8C, n-BuLi (2 mmol, 1.3 mL of a 1.5 M pentane
solution) was added dropwise over 20 min with stirring. The
mixture was stirred for additional 20 min and CO2 was
bubbled into the reaction mixture from a flask containing
solid CO2. An abundant yellow precipitate formed. The
cooling bath was removed, the mixture was allowed to
warm to rt, and water (50 mL) and hexane (50 mL) were
added. The aqueous layer was separated, cooled with water/
ice bath and acidified by addition of diluted HCl. A pale
yellow precipitate formed. This was collected by filtration to
afford 360 mg of crude material. This was dissolved in ethyl
ether (10 mL), treated with CH2N2 (see General) and stirred
for 2 h. TLC (AcOEt/hexane, 1/4) showed four spots: RfZ
0.77, 0.63, 0.47 and 0.32 corresponding to mono-, di-, tri-
and tetra-ester, respectively. The mixture of methyl esters
was purified by column chromatography (AcOEt/hexane,
1/4) to afford 70 mg of 13 and 14 in ratio 1.5:1 (1H NMR)
5.2.13. Ru(bpy)2(Ad-Tripod-(Ph-E)2-Bpy)2C 2PF6K
(2). Complex 2 was prepared using the same procedure
from 11 (70 mg, 0.075 mmol) in THF (2 mL), ethanol/water
(10 mL), Ru(bpy)2Cl2$2H2O (40 mg, 0.075 mmol), NaPF6
to afford 67 mg of 2 (56% yield). 1H NMR dH: (CD3-
COCD3): 8.95 (d, 2H, JZ9.0 Hz, bpy), 8.84 (d, 4H, JZ
8.0 Hz, bpy), 8.25–8.18 (m, 6H), 8.12–8.06 (m, 5H), 8.02

Q. Wei, E. Galoppini / Tetrahedron 60 (2004) 8497–8508
8507
3. (a) Loewe, R. S.; Ambroise, A.; Muthukumaran, K.; Padmaja,
K.; Lysenko, A. B.; Mathur, G.; Li, Q.; Bocian, D. F.; Misra,
V.; Lindsey, J. S. J. Org. Chem. 2004, 69, 1453. (b) Wei, L.;
Padmaja, K.; Youngblood, W. J.; Lysenko, A. B.; Lindsey,
J. S.; Bocian, D. F. J. Org. Chem. 2004, 69, 1461. (c) Long, B.;
Nikitin, K.; Fitzmaurice, D. J. Am. Chem. Soc. 2003, 125,
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(yield of 13 w15–20%). The mixture could not be separated
by column chromatography or other methods, because both
compounds had an identical Rf factor in a variety of eluents,
and have identical solubility properties in a variety of
1
solvents. H NMR of 13 and 14 dH: (CDCl3): 8.04 (d, 6H,
JZ9.0 Hz, PhCOOMe), 7.70 (d, JZ9.0 Hz, PhI), 7.57 (s),
7.56 (d, 6H, JZ9.0 Hz, PhCOOMe), 7.51 (d, JZ7.0 Hz),
7.41 (t, JZ7.5 Hz), 7.25 (d, JZ8.0 Hz, PhI), 3.92 (s, 9H,
COOMe), 2.19 (two s, 12H, CH2(Ad)). 13C NMR dC:
(CDCl3): 167.1 (COOMe), 154.2, 153.9, 148.8, 148.5,
137.8, 130.0, 128.8, 128.5, 128.4, 127.4, 125.3, 125.1, 92.0,
52.3 (COOMe), 47.0; 46.9; 46.8 and 46.7 (CH2(Ad)), 39.8;
39.7 and 39.3 (C(Ad)).
4. For examples of tripodal thiols that bind to gold see
(a) Whitesell, J. K.; Chang, H. K. Science 1993, 261, 73.
(b) Hirayama, D.; Takimiya, K.; Aso, Y.; Otsubo, T.; Hasobe,
T.; Yamada, H.; Imahori, H.; Fukuzumi, S.; Sakata, Y. J. Am.
Chem. Soc. 2002, 124, 532. (c) Yao, Y. X.; Tour, J. M. J. Org.
Chem. 1999, 64, 1968. (d) Mattern, D. L.; Hu, J. H. J. Org.
Chem. 2000, 65, 2277.
A 1:1 mixture (GC/MS) of 5b (295 mg, w0.56 mmol of 5b)
was added to a solution of mixture 13 and 14 (410 mg,
w0.56 mmol of 13) in i-Pr2NH (0.15 mL) and THF (30 mL)
at rt, followed by Pd(dba)2 (18.5 mg, 0.028 mmol), PPh3
(29 mg, 0.11 mmol), and CuI (10 mg, 0.054 mmol). The
mixture was stirred at rt for 24 h and filtered. GC/MS of the
filtrate shows the formation of dimer from 5b. TLC (CHCl3/
hexane, 1/9) showed two spots: 8b, RfZ0.48 and 14, RfZ
0.45. The mixture was separated by column chromato-
graphy (CHCl3/hexane, 1/9) to afford 8b (110 mg, 40%).
The spectral data were identical to those obtained for 8b
prepared though route A.
5. For rigid-rods linkers see (a) Hoertz, P. G.; Carlisle, R.; Meyer,
G. J.; Wang, D.; Piotrowiak, P.; Galoppini, E. Nano Lett. 2003,
3, 325. (b) Wang, D.; Schlegel, J. M.; Galoppini, E.
˚
Tetrahedron 2002, 58, 6027. (c) Kilsa, K.; Mayo, E. I.;
Kuciauskas, D.; Villahermosa, R.; Lewis, N. S.; Winkler,
J. R.; Gray, H. B. J. Phys. Chem. A 2003, 3379.
6. Galoppini, E. Coord. Chem. Rev. 2004 in press. doi
10.1016/j.ccr.2004.03.016.
7. Abbreviations used in this paper: BcoZ1,4-bicyclo[2.2.2]-
octyl; bpyZ4-(2,20-bipyridyl); phenZ5-(1,10-phenanthro-
linyl); dcbZ4,40-(COOH)2K2,2-bipyridine; Ad-TripodZ
1,3,5-tris(p-carboxyphenyl)-7-adamantyl. The Ad-tripod
notation is different from that used in our previous publi-
cations. In this paper the phenyl group in position 7 is
considered part of the bridge.
Acknowledgements
E.G. is grateful to the Division of Chemical Sciences, Office
of Basic Energy Sciences, Office of Energy Research, US
Department of Energy (DE-FG02-01ER15256) for grant
support. Q.W. thanks Mr Dong Wang for help in the
synthesis of 5b.
8. (a) Wang, Y.; Liu, S.; Pinto, M. R.; Dattelbaum, D.;
Schoonover, J.; Schanze, K. J. Phys. Chem. B 2001, 105,
1118. (b) Walters, K. A.; Dattelbaum, D.; Ley, K. D.;
Schoonover, J.; Meyer, T. J.; Schanze, K. Chem. Com-
mun.2001, 1834. (c) Li, Y.; Whittle, E.; Walters, K. A.; Ley,
K. D.; Schanze, K.; MRS Symposium Series 2002, Vol. 665 p 61.
For an example with p-phenylenes see: (d) De Cola, L.; Welter,
S.; Brunner, K.; Hofstraat, J. W. Nature 2003, 421, 54.
9. (a) Zimmermann, C.; Willig, F.; Ramakrishna, S.; Burfeindt,
B.; Pettinger, B.; Eichberger, R.; Stork, W. J. Phys. Chem. B
Supplementary data
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.tet.2004.06.124
¨
2001, 105, 9245. (b) Benko, G.; Kallioinen, J.; Korppi-
¨
Tommola, J. E. I.; Yartsev, A.; Sundstrom, V. J. Am. Chem.
Soc. 2002, 124, 489. (c) Asbury, J. B.; Hao, E.; Wang, Y.;
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(e) Kasciauskas, D.; Monat, J. E.; Villahermosa, R.; Gray,
H. B.; Lewis, N. S.; McCusker, J. K. J. Phys. Chem. B. 2002,
106, 9347.
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30. We have tentatively assigned the structure of 14 as 1-phenyl-
3,5,7-tris(4-carbomethoxyphenyl)adamantane. This assign-
ment is based on (i) the 1H NMR of the mixture (see
Supplementary data), (ii) the observation that 14 does not react
in the cross coupling step, (iii) the observation that the polarity
on silica is identical to that of 13, similar to what we have
experienced when a H is replaced by a I group in
tetraphenylmethane derivatives. Unreacted 14 was separated
from the product after the cross-coupling, but could never be
isolated in pure form
22. 1-Bis(ethynyl)-bicyclo[2.2.2]octane, with or without tri-
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