Synthesis and optical properties of bifunctional thiophene molecules coordinated to ruthenium

Article abstract of DOI:10.1021/jo070377o

(Chemical Equation Presented) A series of unsymmetrical bi- and tetrathiophenes have been synthesized with bipyridine and phosphonic acid functional groups. To do this, phosphonic esters were bonded to thiophenes and the thiophenes coupled to bipyridine. After synthesis of the thienylbipyridines, bis(bipyridine) ruthenium was coordinated to them through the bipyridines. The thienylbipyridines absorb visible light and fluoresce; however, on attachment to ruthenium, both their fluorescence and that of ruthenium are quenched. An additional effect of coordinating ruthenium to the thiophenes is a new absorption band around 470 nm. Variation in oligothiophene length and bipyridine substitution position allowed comparison of the effect of these variables on electronic properties. The longer oligothiophenes display lower-energy absorptions and emissions than that of the shorter thiophenes. In contrast, the position of the bipyridine attachment does not have a large effect on the absorbance or emission wavelength, or on the fluorescence quantum yield.

Full text of DOI:10.1021/jo070377o

Synthesis and Optical Properties of Bifunctional Thiophene
Molecules Coordinated to Ruthenium
Joseph S. Bair and Roger G. Harrison*
Department of Chemistry and Biochemistry, Brigham Young UniVersity, ProVo, Utah, 84602
roger_harrison@byu.edu
ReceiVed February 23, 2007
A series of unsymmetrical bi- and tetrathiophenes have been synthesized with bipyridine and phosphonic
acid functional groups. To do this, phosphonic esters were bonded to thiophenes and the thiophenes
coupled to bipyridine. After synthesis of the thienylbipyridines, bis(bipyridine) ruthenium was coordinated
to them through the bipyridines. The thienylbipyridines absorb visible light and fluoresce; however, on
attachment to ruthenium, both their fluorescence and that of ruthenium are quenched. An additional
effect of coordinating ruthenium to the thiophenes is a new absorption band around 470 nm. Variation
in oligothiophene length and bipyridine substitution position allowed comparison of the effect of these
variables on electronic properties. The longer oligothiophenes display lower-energy absorptions and
emissions than that of the shorter thiophenes. In contrast, the position of the bipyridine attachment does
not have a large effect on the absorbance or emission wavelength, or on the fluorescence quantum yield.
Introduction
In addition to metal surfaces, oligothiophenes have been
extensively studied in conjunction with one or more optically
interesting groups, such as fullerenes,8-16 porphyrins,9-10 fer-
Oligothiophenes are a promising class of fluorescent mol-
ecules that have potential applications in photovoltaics and
fluorescence sensing.1 They are employed as conducting
molecules because of their favorable optical and electronic
properties and their environmental stability.2,3 Electronic proper-
ties of oligothiophenes are tunable based on the number of
conjugated subunits and types of substituents on the subunits.
Aryl-aryl coupling reactions are used to synthesize oligoth-
iophenes. The thiophenes can be attached to a conducting
surface, which often results in highly ordered self-assembled
monolayer. Recently, they have been attached to gold,4 silicon,5
indium tin oxide (ITO),6 and CdSe nanocrystals.7
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* Author to whom correspondence should be addressed. Fax: 801-422-0153.
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10.1021/jo070377o CCC: $37.00 © 2007 American Chemical Society
Published on Web 08/03/2007
J. Org. Chem. 2007, 72, 6653-6661
6653

Bair and Harrison
SCHEME 1. Synthesis of 5- and 4-Bromobipyridinea
a Reagents: (a) (1) n-BuLi, Bu3SnCl; (2) 2,5-dibromopyridine, Pd(PPh3)4; (b) MMPP; (c) concd H2SO4, concd HNO3; (d) (1) acetyl bromide; (2) PBr3.
rocenes,12 and ligand-coordinated transition metals, especially
ruthenium.17-26 Ruthenium complexes are commonly used as
a source of photoexcited electrons for molecular devices. The
many current applications include organic circuitry in solar
cells,27-29 fluorescent cation sensors,30 and other energy transfer
systems.31-34
We are interested in attaching oligothiophenes to photon-
excitable molecules, such as Ru complexes, and using the
oligothiophenes as conduits for electron transfer. Ideally, we
desire oligothiophenes that have a Ru-binding group on one
end and a surface-binding group on the other end. Although,
Ru-binding groups have been attached to thiophenes and surface-
binding groups have been attached to thiophenes, thiophenes
with both have not been synthesized. Bipyridine (bpy) is known
to complex well with ruthenium, so attachment of bpy to one
end of the oligothiophene is a promising approach for the
ruthenium binding group. The position of that attachment on
bipyridine is important electronically.17,22,33-37 The other func-
tional group on the oligothiophene will be a surface binding
phosphonic acid. We choose phosphonic acid because its oxygen
atoms bind strongly to surface metal cations. Herein we report
the synthesis of the first asymmetric bithiophenes and tetrathio-
phenes that contain bipyridine and phosphonic acid. These
oligothiophenes have bipyridine attached to one end and
phosphonic acid attached to the other end. We also synthesized
the Ru complexes of the thiophenes and report their absorption
and emission properties.
Results and Discussion
The planned procedure to prepare the unsymmetrical thiophenes
involved preparing the di- and tetrathiophenes and then attaching
bipyridine and phosphonic acid groups to them. This procedure
worked for the bithiophenes, but was not effective for the
tetrathiophenes because of the insolubility of tetrathiophene in
common solvents. We planned to use Stille coupling to connect
the thiophenes to bipyridine, requiring synthesis of the bromo-
bipyridines. The synthesis of 5-bromopyridine (1) took one step
and utilized catalytic coupling in a Stille fashion (Scheme 1).38
The synthesis of 4-bromobipyridine (4) required three steps and
several modifications to published procedures (Scheme 1).39-41
To convert bipyridine to bipyridine N-oxide, magnesium
monoperoxyphthalate (MMPP) was used instead of m-chlorop-
eroxybenzoic acid because of its lower toxicity and expense.
The reaction ran efficiently in ethanol and did not require glacial
acetic acid.39 The bipyridine N-oxide was easily separated from
unreacted bipyridine by extraction and flash chromatography.
Next, the bipyridine N-oxide was nitrated by carefully
controlling the temperature (100 °C) and rate of nitric acid
addition. The yield of 4-nitrobipyridine N-oxide (3) was as large
as if fuming sulfuric and nitric acids had been used (50%).40
The slow rate of nitric acid addition and moderate temperature
reduce the amount of dinitrobipyridine N-oxide formation. The
transformation to the 4-bromobipyridine (4) was accomplished
by adding acetyl bromide to replace the nitro group and PBr3
to remove the oxide.41 The 4-bromobipyridine was purified by
extraction with CHCl3 followed by sublimation.
(17) Moorlag, C.; Sarkar, B.; Sanrame, C. N.; Bauerie, P.; Kaim, W.;
Wolf, M. O. Inorg. Chem. 2006, 45, 7044-7046.
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Phys. Chem. A. 2003, 107, 3476-3485.
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G.; Bauerle, P.; Goeb, S.; Ziessel, R. Inorg. Chem. 2005, 44, 8033-8043.
(21) Goeb, S.; De Nicola, A.; Ziessel, R.; Sabatini, C.; Barbieri, A.;
Barigelletti, F. Inorg. Chem. 2006, 45, 1173-1183.
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1999, 9, 2123-2131.
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2003, 288-289.
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Bithiophenes. To synthesize the bithiophene that could be
coupled to bipyridine, the tin reagent of bithiophene was
synthesized. After diethyl chlorophosphonate was used to attach
a phosphonic ester group to bithiophene, lithium diisopropyla-
(31) Liu, X.; Liu, J.; Pan, J.; Chen, R.; Na, Y.; Gao, W.; Sun, L.
Tetrahedron 2006, 62, 3674-3680.
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Martenson, J.; Styring, S.; Hammarstrom, L.; Sun, L.; Akermark, B. Inorg.
Chem. 2003, 42, 7502-7511.
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J. Am. Chem. Soc. 1997, 119, 8253-8268.
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Cordeiro, E. S.; de Oliveira, I. M. F.; Carvalho, S.; Paniago, E. B. J. Braz.
Chem. Soc. 1998, 9, 455-460.
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2075-2083.
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Chem. Commun. 2005, 802-804.
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2001, 4, 169-175.
6654 J. Org. Chem., Vol. 72, No. 18, 2007

Bifunctional Thiophene Molecules Coordinated to Ru
SCHEME 2. Synthesis of Bithiophene Compounds 9 and 11a
a Reagents: (a) (1) n-BuLi; (2) (EtO)2P(O)Cl; (b) (1) LDA; (2) Bu3SnCl; (c) 1, Pd(PPh3)4; (d) (1) TMSBr; (2) H2O; (e) 4, Pd(PPh3)4; (f) (1) TMSBr; (2)
H2O.
SCHEME 3. Synthesis of Tetrathienylbipyridine 16a
a Reagents: (a) (1) n-BuLi; (2) Bu3SnCl; (b) 1, Pd(PPh3)4; (c) NBS; (d) 7, Pd(PPh3)4; (e) (1) TMSBr; (2) H2O.
SCHEME 4. Synthesis of Tetrathienylbipyridine 20a
a Reagents: (a) (1) n-BuLi; (2) Bu3SnCl; (b) 4, Pd(PPh3)4; (c) NBS; (d) 7, Pd(PPh3)4; (e) (1) TMSBr; (2) H2O.
mide (LDA) and tributyltin chloride were used to bond
tributyltin to the other side of the bithiophene (Scheme 2).42
This tin compound (7) was used to make both the 4- and
5-bithienybipyridines. The aryl-aryl coupling of 7 to 4- and
5-bromopyridine was catalyzed by palladium. Trimethylsilyl
bromide (TMSBr) was used to promote the hydrolysis of the
esters to acids.7,43 The 4- and 5-bithienylbipyridines (9 and 11)
have phosphonic acid groups and are ready to be coordinated
to ruthenium.
Tetrathiophenes. Addition of bipyridine and phosphonic acid
groups to bithiophene was straightforward, but because
tetrathiophene was much less soluble than bithiophene, a new
synthetic strategy was used to synthesize derivatives of
tetrathiophene. The strategy entailed adding functional groups
to bithiophene and then coupling the bithiophenes. The tribu-
tyltin phosphonic ester bithiophene (7) represents half of the
needed tetrathiophene. It was thus necessary to synthesize the
coupling partners of 7, the thiophenes with bipyridine groups.
Because Stille coupling was the desired path to form the
tetrathienylbipyridine compounds, the tin adduct of bithiophene
was made (Scheme 3). This tributyltin bithiophene (12) was
coupled to 4- and 5-bromobipyridines using a palladium catalyst
and formed the bithienylbipyridines (13 and 17, Schemes 3 and
4).22 These compounds were easily brominated with N-bromo-
succinimide (NBS), after which the tributyltin phosphonic ester
bithiophene (7) was coupled to them, again using a palladium
catalyst. The hydrolysis of the esters to acids was facilitated
with TMSBr. These tetrathienylbipyridine compounds (16 and
20) are less soluble than the bithienylbipyridines, and the
4-thienylbipyridines are somewhat more soluble than the
5-thienylbipyridines.
(42) Edder, C.; Frechet, J. M. J. Org. Lett. 2003, 5, 1879-1882.
(43) McKenna, C. E.; Higa, M. T.; Cheung, N. H.; McKenna, M-C.
Tetrahedron Lett. 1977, 2, 155-158.
J. Org. Chem, Vol. 72, No. 18, 2007 6655

Bair and Harrison
FIGURE 1. Ruthenium-thienylbipyridine complexes.
TABLE 1. Absorption and Emission Properties of Oligothiophenes and Oligothiophene-Ruthenium Complexesa
absorption
emission
em (nm)d
compound
λ
max(nm) (ꢀmax (M-1 cm-1))
λ
φem(%)e
8
237 (12000)
241 (11000)
238 (12000)
250 (18000)
242 (19000)
240 (17000)
261 (10000)
274 (10000)
289 (12000)
286 (16000)
282 (16000)
274 (17000)
365 (43000)
377 (32000)
359 (20000)
363 (28000)
363 (40000)
374 (38000)
422 (38000)
438 (22000)
357 (28000)
362 (24000)
420 (36000)
428 (28000)
397 (41000)
384 (32000)
446 (52000)
437 (49000)
393 (20000)
416, 437
430, 449
408, 420
452
445
454
490, 514
503, 530
430
27
9b
10
19
24
20
26
28
11b
13
13b
15
15b
17
17b
19
19b
21
22
23
24
436
486, 508
497, 523
445
436
486
452
450, 478
600
244 (27000)
245 (34000)
245 (32000)
245 (38000)
254 (8000)
244 (29000)
287 (78000)
288 (75000)
288 (75000)
289 (75000)
462 (18000)
466 (28000)
480 (39000)
478 (46000)
0.23
0.13
0.12
0.17
tetrathiophenec
Ru(bpy)3(PF6)2
287 (95000)
450 (16000)
a Dissolved in acetonitrile unless otherwise noted. Concentrations are 0.01 mM. b Dissolved in DMSO. c Dissolved in THF. d Excitation wavelengths at
350-400 nm. e Excitation wavelength 350 nm.
Ruthenium Compounds. To make the ruthenium-bound
thienylbipyridine complexes, the thienylbipyridines 9, 11, 16,
and 20 were refluxed with RuCl2(bpy)2 in basic water. Red
unit. This lowest-energy absorption is the most intense and is
the most red-shifted from the bithiophenes to the tetrathiophenes
(58 nm from 8 to 15 and 61 nm from 10 to 19). Three absorption
peaks are observed for similar compounds.24 The 4- and
5-substituted thienylbipyridines have similar absorbance wave-
lengths. This is the case for the bithiophenes (8 and 10) as well
as the tetrathiophenes (15 and 19). The phosphonic ester and
acid groups do not have a major affect on the absorbance peaks
as can be seen by comparing the compounds with phosphonic
groups (8, 9, 10, 11) to those without (13, 17).
44
ruthenium complexes (21, 22, 23, and 24, Figure 1) were
precipitated by acidifying the solution and exchanging the
chlorides for hexafluorophosphates. The tetrathienylbipyridine
ruthenium complexes required much longer reaction times than
the bithienylbipyridines.
Optical Studies. Absorbance and emission measurements
were made to know the relative energies of the orbital levels,
the orbital overlap, and electronic communication between Ru
and oligothiophene and to elucidate the differences between 4-
and 5-substituted bipyridines. Table 1 summarizes UV-visible
absorption and emission data. Acetonitrile was the principle
solvent, but DMSO was also used for enhanced solubility.
DMSO resulted in a small red shift (5 to 8 nm).
The oligothienylbipyridines, whether bithiophenes or tetrathio-
phenes, exhibit similar spectral features. They have a high-
energy absorbance in the region of 240 nm, which is assigned
to thiophene absorption. They also have an absorbance peak
between 275 and 290 nm, which is assigned to bipyridine
absorption. A third peak in the region of 350-430 nm is
assigned to a π-π* transition for the entire thienylbipyridine
Comparing the bithienylbipyridine compounds (13 and 17)
to tetrathiophene shows the π-π* transition in tetrathiophene
red-shifted. Thus, there is better conjugation when only thiophenes
are connected. On the other hand, when tetrathiophene is
compared to tetrathienylbipyridine compounds (15 and 19), its
absorption is blue-shifted. This 30 nm shift can be explained
by the increased conjugation over six aromatic rings compared
to four for tetrathiophene alone.
An interesting observation may be made by comparing the
known compounds 5,5′- and 4,4′-bis(bithienyl)bipyridines 25
and 26 (Figure 2)22 to 5- and 4-tetrathienylbipyridines 15 and
19. Each has a bipyridine and four thiophene rings, but 25 and
26 have bithiophene units on each side of the bipyridine, unlike
15 and 19 which have all of the thiophenes connected to each
other. The absorption bands of 25 (396 nm) and 26 (361 nm)
(44) Sullivan, B. P.; Salmon, D. J.; Meyer, T. J. Inorg. Chem. 1978, 17,
3334-3341.
6656 J. Org. Chem., Vol. 72, No. 18, 2007

Bifunctional Thiophene Molecules Coordinated to Ru
the ruthenium thienylbipyridines are a hundred times weaker
than the unbound thienylbipyridines. The fluorescence quench-
ing indicates that nonradiative excited-state energy decay
pathways become accessible when Ru is bound to the thienyl-
bipyridines. Other ruthenium thiophene complexes also exhibit
fluorescence quenching.20
Electrochemisty. Oxidation and reduction properties of the
compounds were investigated using cyclic voltammetry. The
bithienylbipyridines have two oxidation processes, 13: 1.25 and
1.39 V, 17: 1.36 and 1.49 V. The tetrathienylbipyridines (15
and 19) have at least three oxidation processes, which are
observed at 1.15, 1.48, and 1.62 V (Figure 5). They also exhibit
a reduction process at -1.82 V. The ruthenium-bound thienyl-
bipyridines (21-24) have an oxidation process at around
1.4 V, which is attributed to the Rubpy moiety (Figure 6). Ru-
(bpy)32+ has a reduction process at 1.38 V. Also, the ruthenium-
bound bithienylbipyridines have an oxidation process at 1.7 V
and a reduction process at around -1.4 V. Because of the poor
solubility of the ruthenium-bound tetrathiophenes, weak signals
are observed for their oxidation and reduction processes.
However, besides the oxidation process from the Rubpy group,
they exhibit oxidation processes at 1.1 and 1.5 V. And, 24
exhibits reduction processes at -0.99 and -1.25 V.
FIGURE 2. 5,5′′-Bis(bithienyl)bipyridine (25) and 4,4′-bis(bithienyl)-
bipyridine (26).
are at shorter wavelengths by 30-60 nm relative to 15
(432 nm) and 19 (420 nm). The energy transition is smaller
when thiophenes are directly connected than when they are
bound to bipyridine.
The thienylbipyridines fluoresce at wavelengths 70-80 nm
lower in energy relative to their absorption (Figure 3, Table 1).
As expected, the tetrathiophenes emit at longer wavelengths than
the bithiophenes. Their fluorescence quantum yields are between
19 and 28% when they are excited at 350 nm. The emission of
the 5-substituted bithienylbipyridine (8) is at slightly lower
energy and more efficient than the emission of 4-substituted
bithienylbipyridine (10). The fluorescent lifetimes of the thie-
nylbipyridines are less than 2 ns; other oligothiophenes have
fluorescent lifetimes near 1 ns.45
Conclusion
Ruthenium-Bound Thiophenes. The absorbance spectra of
the four ruthenium-thienylbipyridine complexes (21-24) show
one more peak than the non Ru-coordinated thiophenes
(Figure 4). The new peak is due to the Ru(bpy)3 unit. The two
peaks at around 250 and 290 nm are due to thiophene and
bipyridine, as they were with the metal free thiophenes.
However, the 290 nm peak is much stronger than it was before
Ru was coordinated, because there are now three bipyridines
for each thiophene unit due to the added ancillary bipyridines
on Ru. The next absorbance peaks between 384 and 446 nm,
assigned to π-π* transitions, are red-shifted from where they
were before Ru was coordinated to the thienylbipyridines. The
magnitudes of the shifts for the compounds are: 32 nm (21
from 8), 25 nm (22 from 10), 24 nm (23 from 15), and 17 nm
(24 from 19). This effect is common to Ru complexes of this
type and has been ascribed to the “donor-acceptor” nature of
the system.14 As seen by the magnitudes of the shifts, when
bipyridine is substituted at the 5-position, the red-shift is larger
by 7 nm for both the bithiophene and tetrathiophene. Also, there
is generally an increase in the molar absorptivity of the peaks
after Ru coordination.
The lowest energy absorbance peaks for the compounds,
found from 462 to 480 nm, are assigned to metal-to-ligand
charge-transfer (MLCT) transitions. They are red-shifted from
those of Ru(bpy)32+ by 12-16 nm for the bithiophenes and 28-
30 nm for the tetrathiophenes. No significant difference is
observed between the 4- and 5-bipyridine positions. The red
shift of the MLCT transitions can be explained by the negative
charge being delocalized in a lower energy orbital originating
from both bipyridine and thiophene. There is also observed an
Asymmetric bithiophene and tetrathiophene compounds were
synthesized with bipyridine and phosphonic acid groups. During
the synthesis, tin adducts were used and smaller thiophenes were
coupled to make tetrathiophenes. The thiophenes were attached
to 4- and 5-substituted bipyridines. The bi- and tetrathienylbi-
pyridine compounds were coordinated to Ru, and their optical
spectra were recorded. Absorption spectra indicate that longer
thiophenes have smaller energy gaps between ground and
excited states. Ruthenium coordination to the thiophenes causes
the π-π* and MLCT transitions to be red-shifted. The π-π*
transition is more red-shifted when the bipyridine is substituted
at the 5 position. The free thiophenes fluoresce with quantum
yields from 19-28%, while the Ru-bound thiophenes exhibit
fluorescence quenching. The Ru-bound and unbound thienyl-
bipyridines have oxidation processes in the range 1.1 to 1.7 V.
Experimental Section
Diethyl 5′-(2,2′-Bipyridin-5-yl)-2,2′-bithien-5-ylphosphonate
(8). To 20 mL of dry toluene under N2 were added 7 (0.88 g,
1.5 mmol), 5-Brbpy (0.350 g, 1.49 mmol) and Pd(PPh3)4 (0.089 g,
5.1 mol %). The solution was refluxed for 72 h. Toluene was
evaporated, and the solid was chromatographed on silica with ethyl
acetate as the eluent. The product was recovered and left under
vacuum to remove volatile impurities. It (0.57 g, 1.2 mmol, 81%)
1
was collected as a slightly sticky yellow solid. H NMR (CDCl3,
300 MHz): δ 8.93 (dm, 1H, J ) 3.0 Hz), 8.69 (dm, 1H, J ) 5.0
Hz), 8.44 (d, 1H, J ) 8.5 Hz), 8.42 (d, 1H, J ) 7.0), 7.98 (dd, 1H,
J ) 2.5, 8.5 Hz), 7.82 (ddd, 1H, J ) 2.0, 8.0 Hz), 7.58 (dd, 1H,
J ) 3.5, 8.0 Hz), 7.37 (d, 1H, J ) 3.5 Hz), 7.32 (ddd, 1H, J ) 1.0,
7.5, 5.0), 7.28 (d, 1H, J ) 3.0 Hz), 7.26 (dd, 1H, J ) 3.5, 3.5 Hz),
4.25-4.09 (m, 4H), 1.37 (t, 6H, J ) 7.0 Hz). 13C NMR (CDCl3,
75 MHz): δ 155.6, 155.3, 149.4, 146.1, 145.0 (d, J ) 8.0 Hz),
140.8, 137.7 (d, J ) 11.0 Hz), 137.1, 136.5 (d, J ) 3.0 Hz), 133.6,
129.7, 126.7 (d, J ) 210.0 Hz), 126.4, 125.4, 124.7 (d, J )
17.0 Hz), 124.0, 121.2, 121.2. 31P NMR (CDCl3, 121 MHz): δ
11.56 (s). UV-vis (NCCH3) λ, nm (ꢀ, M-1 cm-1): 237 (12000),
261 (10000), 365 (43000). HRMS (ESI-TOF) m/z calcd for
C22H21N2O3PS2 (M + Na)+ 479.0623; found 479.0623.
increase in the molar absorptivity of these absorbance bands
2+
compared to Ru(bpy)3
.
The emission spectra of the ruthenium thienylbipyridine
complexes show a dramatic quenching of both the thienylbi-
pyridine and Ru-bpy fluorescence. The strongest emissions for
(45) Becker, R. S.; de Melo, J. S.; Macanita, A. L.; Elisei, F. J. Phys.
Chem. 1996, 100, 18683-18695.
J. Org. Chem, Vol. 72, No. 18, 2007 6657

Bair and Harrison
FIGURE 3. Emission spectra of bithienylbipyridines (8, blue; 10, pink) and tetrathienylbipyridines (15, brown; 19, green) excited at 350 nm.
Taken at room temperature.
5.0 Hz), 8.68 (d, 1H, J ) 5.5 Hz), 8.63 (d, 1H, J ) 1.5 Hz), 8.42
(d, 1H, J ) 8.0 Hz), 7.85 (ddd, 1H, J ) 2.0, 8.0, 8.0 Hz), 7.59 (d,
1H, J ) 4.0 Hz), 7.59 (dd, 1H, J ) 3.5, 8.5 Hz), 7.48 (dd, 1H,
J ) 2.0, 5.0 Hz), 7.35 (ddd, 1H, J ) 1.0, 7.5, 5.5), 7.29 (d, 1H, J
) 4.0 Hz), 7.28 (dd, 1H, J ) 3.5, 3.5 Hz), 4.11-4.25 (m, 4H),
1.37 (t, 6H, J ) 7.0 Hz). 13C NMR (CDCl3, 125 MHz): δ 157.1,
155.8, 150.0, 149.3, 137.7 (C-P J ) 11.0 Hz), 137.1, 128.7, 128.6,
127.0 (C-P J ) 209.5), 126.6, 126.3, 125.0 (C-P J ) 16.5 Hz),
124.1, 121.4, 119.6, 117.0, 63.0 (C-P J ) 5.5 Hz), 16.4 (C-P
J ) 6.5 Hz). 31P NMR (CDCl3, 121 MHz); δ (ppm): 11.45 (s).
UV-vis (NCCH3) λ, nm (ꢀ, M-1 cm-1): 241 (11000), 274 (10000),
358 (20000). HRMS (ESI-TOF) m/z calcd for C22H21N2O3PS2 (M
+ Na)+ 479.0623; found: 479.0624.
5′-(2,2′-Bipyridin-4-yl)-2,2′-bithien-5-ylphosphonic Acid (11).
Compound 10 (0.502 g, 1.1 mmol) was added to a Schlenk flask
and thoroughly degassed with N2. Trimethylsilyl bromide (TMSBr)
(1.0 mL, 7.6 mmol) was added through a septum. The resultant
slurry was stirred overnight under N2. The reaction was quenched
with water and stirred vigorously. The solid was filtered out and
washed with acetone. Product (0.394 g, 0.97 mmol, 90%) was
collected as an orange powder (mp 232-237 °C). 1H NMR (DMSO,
500 MHz): δ 8.80 (d, 1H, J ) 4.5 Hz), 8.75 (d, 1H, J ) 5.0 Hz),
8.70 (d, 1H, J ) 0.5 Hz), 8.57 (d, 1H, J ) 8.0 Hz), 8.14 (ddd, 1H,
J ) 1.0, 8.0, 8.0 Hz), 8.06 (d, 1H, J ) 4.0 Hz), 7.91 (dd, 1H, J )
1.5, 5.0 Hz), 7.64 (ddd, 1H, J ) 1.0, 6.0, 6.0 Hz), 7.61 (d, 1H,
J ) 4.0 Hz), 7.52 (dd, 1H, J ) 3.5, 3.5 Hz), 7.42 (dd, 1H, J ) 3.5,
8.5 Hz). 31P NMR (DMSO, 121 MHz): δ 5.20 (s). UV-vis (H2O/
OH-) λ, nm (ꢀ, M-1 cm-1): 238 (13000), 278 (13000), 363 (31000).
HRMS (ESI-TOF) m/z calcd for C18H13N2O3PS2 (M + H)+
401.0178; found 401.0176.
5-(2,2′-Bipyridin-5-yl)-2,2′-bithiophene (13). Bithiophene (5)
(2.00 g, 12.0 mmol) was dissolved in 50 mL of dry THF under N2,
and the solution was cooled to -78 °C. n-BuLi (7.5 mL, 12 mmol)
was added dropwise, and the solution was stirred for 1 h at
-78 °C. Tributyltin chloride (3.9 mL, 14 mmol) was added in one
aliquot, and the mixture was left to stir and warm to room
temperature overnight. The solvent was evaporated, and 50 mL of
dry toluene was added. The precipitate was removed by vacuum
filtration under air. The solution was returned to a Schlenk flask
and purged with N2. Compound 1 (2.76 g, 11.7 mmol) and Pd-
(PPh3)4 (0.41 g, 2.9 mol %) were added, and the solution was heated
to reflux for 72 h. The solvent was evaporated, and the solid was
taken up in 200 mL of CH2Cl2 and 50 mL of 2 M NaOH. The
layers were separated, and solid impurities in the organic layer were
removed by filtration through celite. The solid was washed with
CH2Cl2 until the filtrate ran pale, and then the solid was discarded.
FIGURE 4. Absorbance spectra of the four Ru-oligothiophenes (21,
brown; 22, green; 23, red; 24, blue). Concentrations were 0.01 mM in
acetonitrile.
5′-(2,2′-Bipyridin-5-yl)-2,2′-bithien-5-ylphosphonic Acid (9).
To 8 (0.479 g, 1.05 mmol) under N2 was added TMSBr (1.0 mL,
7.6 mmol). The slurry was stirred for 2.5 h before being quenched
with water. Excess water was removed under vacuum. Acetone was
added, and the slurry was stirred vigorously and then filtered. The
solid was washed with acetone and methanol until the filtrate ran
colorless. The bright orange solid (mp 218-221 °C) was dried and
collected (0.335 g, 0.77 mmol, 73%). 1H NMR (CDCl3,
500 MHz): δ 9.07 (d, 1H, J ) 2.5 Hz), 8.74 (d, 1H, J ) 4.5 Hz),
8.47 (d, 1H, J ) 2.5, Hz), 8.46 (d, 1H, J ) 2.5 Hz), 8.27 (dd, 1H,
J ) 2.5 Hz, 8.5 Hz), 8.07 (ddd, 1H, J ) 8.0, 8.0, 0.5 Hz), 7.78 (d,
1H, J ) 4.0 Hz), 7.55 (t, 1H, 6.0 Hz), 7.52 (d, 1H, J ) 4.0 Hz),
7.43-7.39 (m, 2H). 31P NMR (DMSO, 121 MHz): δ 5.36 (s). UV-
vis (DMSO), λ, nm (ꢀ, M-1 cm-1): 377 (ꢀ ) 32000). HRMS (ESI-
TOF) m/z calcd for C18H13N2O3PS2 (M + H)+ 401.0178; found:
401.0177.
Diethyl 5′-(2,2′-Bipyridin-4-yl)-2,2′-bithien-5-ylphosphonate
(10). Compound 7 (1.7 g, 2.9 mmol) was dissolved in 30 mL of
dry toluene under N2. Compound 4 (0.89 g, 4.0 mmol) and Pd-
(PPh3)4 (0.173 g, 5 mol %) were added, and the solution was heated
to reflux for 48 h. After cooling, the solution was extracted with
20 mL of water and then 20 mL of saturated NH4Cl. The combined
aqueous fractions were extracted with toluene (2 × 20 mL). The
combined organic extracts were dried over MgSO4, filtered, and
evaporated. The resulting crude orange oil was chromatographed
on silica with hexanes:ethyl acetate (1:1) followed by ethyl acetate.
The product (0.55 g, 1.2 mmol, 42%) was collected as an orange
1
viscous oil. H NMR (CDCl3, 500 MHz): δ 8.73 (dm, 1H, J )
6658 J. Org. Chem., Vol. 72, No. 18, 2007

Bifunctional Thiophene Molecules Coordinated to Ru
FIGURE 6. Cyclic voltammograms of Ru-thienylbipyridines 21-24
in acetonitrile. Compound concentrations were 0.5 mM or less and NBt4-
PF6 was 0.1 M.
FIGURE 5. Cyclic voltammograms of bithienylbipyridines 13 and 17
in acetonitrile and tetrathienylbipyridines 15 and 19 in dichloromethane.
Compound concentrations were 0.5 mM and NBt4PF6 was 0.1 M.
4.0 Hz), 8.43 (m, 2H), 7.99 (dd, 1H, J ) 2.5, 8.5 Hz), 7.83 (ddd,
1H, J ) 1.5, 7.5, 7.5 Hz), 7.36 (d, 1H, J ) 4.0 Hz), 7.32 (ddd, 1H,
J ) 1.0 Hz, 6.5, 5.0 Hz), 7.25 (dd, 1H, J ) 1.0, 5.0 Hz), 7.24 (dd,
1H, J ) 1.0, 3.5 Hz), 7.20 (d, 1H, J ) 3.5 Hz), 7.05 (dd, 1H, J )
5.0, 3.5 Hz). 13C NMR (CDCl3, 125 MHz): δ 155.8, 155.0, 149.4,
146.1, 139.1, 138.3, 137.1, 133.4, 130.2, 128.2, 125.2, 125.1, 125.0,
124.3, 123.9, 121.2, 121.2. UV-vis (NCCH3) λ, nm (ꢀ, M-1 cm-1):
The solvent was evaporated and the residual solid was chromato-
graphed with silica and 0.5% methanol in ethyl acetate increasing
to 2% methanol. Product (1.47 g, 4.6 mmol, 39%) was collected
as a brown solid (mp 145-148 °C). Sublimation yields a pure
yellow solid, but some material is lost to decomposition. 1H NMR
(CDCl3, 500 MHz): δ 8.94 (d, 1H, J ) 2.0 Hz), 8.69 (d, 1H, J )
J. Org. Chem, Vol. 72, No. 18, 2007 6659

Bair and Harrison
238 (12000), 289 (12000), 363 (40000). HRMS (ESI-TOF) m/z
calcd for C18H12N2S2 (M + H)+ 321.0515; found 321.0513.
5-Bromo-5′-(2,2′-bipyridin-5-yl)-2,2′-bithiophene (14). To
200 mL of 1:1 CHCl3:acetic acid was added 13 (1.00 g, 3.12 mmol)
and N-bromosuccinimide (NBS) (0.56 g, 3.14 mmol). The reaction
was heated to 60 °C and was maintained at that temperature for
15 min before cooling. The mixture was poured into 50 mL of
water, and the layers were separated. The aqueous layer was
extracted with CHCl3 (2 × 50 mL), and the combined organic
extracts were washed with K2CO3(aq) until neutral. The organic
layer was then dried over MgSO4, filtered, and evaporated. Product
(1.21 g, 3.00 mmol, 96%) was collected as an orange solid (mp
175-179 °C, with partial decomposition). 1H NMR (CDCl3,
300 MHz): δ 8.92 (dm, 1H, J ) 2.5 Hz), 8.69 (dm, 1H, J ) 3.5
Hz), 8.43 (dd, 1H, J ) 0.5 Hz, 8.5 Hz), 8.42 (ddd, 1H, J ) 1.0 Hz,
1.0 Hz, 8.5 Hz), 7.97 (dd, 1H, J ) 2.5 Hz, 8.5 Hz), 7.83 (ddd, 1H,
J ) 2.0 Hz, 8.0 Hz, 8.0 Hz), 7.34 (d, 1H, J ) 4.0 Hz), 7.32 (ddd,
1H, J ) 1.5, 7.5, 5.5 Hz), 7.13 (d, 1H, J ) 4.0 Hz), 7.02 (d, 1H,
J ) 4.0 Hz), 6.97 (d, 1H, J ) 4.0 Hz). 13C NMR (CDCl3,
125 MHz): δ 155.8, 155.3, 149.5, 146.2, 139.7, 138.7, 137.2, 137.2,
133.6, 131.0, 130.0, 125.3, 124.4, 124.0, 121.3, 121.3, 111.8. HRMS
(ESI-TOF) m/z calcd for C18H11N2S2Br (M- H)+ 398.9620; found
398.9619.
117.0, 112.1. HRMS (ESI-TOF) m/z calcd for C18H13N2S2Br
(M + H)+ 398.9620; found 398.9621.
Diethyl 5′′′-(2,2′-bipyridin-4-yl)-2,2′-5′,2′′-5′′,2′′′-tetrathien-5-
ylphosphonate (19). To 25 mL of dry toluene under N2 in a Schlenk
flask were added 7 (1.02 g, 1.72 mmol), 18 (0.715 g, 1.79 mmol),
and Pd(PPh3)4 (0.101 g, 5.1 mol %). The solution was heated to
reflux and stirred for 72 h. After cooling, the mixture was poured
into 100 mL of hexane, which precipitated a red/orange solid (mp/
dec ∼150 °C). Product (0.877 g, 1.41 mmol, 82%) was collected
by filtration and washed with hexanes. 1H NMR (CDCl3,
500 MHz): δ 8.72 (dm, 1H, J ) 5.0 Hz), 8.66 (d, 1H, J ) 5 Hz),
8.63 (d, 1H, J ) 2.0 Hz), 8.44 (d, 1H, J ) 8.0 Hz), 7.83 (ddd, 1H,
J ) 2.0, 7.5, 7.5 Hz), 7.57 (d, 1H, J ) 4.0 Hz), 7.55 (dd, 1H, J )
8.5, 3.5 Hz), 7.47 (dd, 1H, J ) 2.0, 5.5 Hz), 7.34 (ddd, 1H, J )
1.0, 8.0, 5.0 Hz), 7.22 (d, 1H, J ) 4.0 Hz), 7.20 (dd, 1H, J ) 3.0,
3.0 Hz), 7.18 (d, 2H, J ) 4.0 Hz), 7.14 (d, 1H, J ) 7.0 Hz), 7.13
(d, 1H, J ) 6.5 Hz), 4.22-4.12 (m, 4H), 1.37 (t, 6H, J ) 7.0 Hz).
13C NMR (CDCl3, 125 MHz): δ 157.1, 156.0, 150.0, 149.4, 142.1,
140.4, 138.8, 137.6, 137.2, 136.4, 136.4, 126.7, 126.2, 125.1, 124.9,
124.2, 121.5, 119.6, 117.0. 31P NMR (CDCl3, 121 MHz): δ 11.63
(s). UV-vis (NCCH3) λ, nm (ꢀ, M-1 cm-1): 240 (17000), 274
(17000), 420 (36000). HRMS (ESI-TOF) m/z calcd for C30H25N2O3-
PS4 (M + 2H)2+ 311.0316; found 311.0316. Anal. Calcd for
C30H25N2O3PS4: C, 58.04; H, 4.06; N, 4.51. Found C, 58.19; H,
4.10; N, 4.44.
Diethyl 5′′′-(2,2′-Bipyridin-5-yl)-2,2′-5′,2′′-5′′,2′′′-tetrathien-
5-ylphosphonate (15). Compounds 7 (2.63 g, 4.4 mmol) and 14
(1.15 g, 2.9 mmol) were dissolved in 90 mL of dry toluene under
N2. Pd(PPh3)4 (0.17 g, 5 mol %) was added, and the mixture was
heated to reflux for 16 h. The reaction mixture was poured into
200 mL of hexanes, and a precipitate was allowed to form for
several minutes. The solid was collected by filtration, and the filtrate
was discarded. The solid was then dissolved in THF, and the
residual solid was removed by filtering through celite and was
discarded. The THF solution was evaporated to an orange/brown
sticky solid which was stirred vigorously in ∼100 mL of ether for
0.5 h. The dry solid (0.770 g, 1.2 mmol, 41%) was collected by
filtration (dec ∼200 °C). 1H NMR (CDCl3, 500 MHz): δ 8.93 (d,
1H, J ) 2.5 Hz), 8.69 (dm, 1H, J ) 2.5), 8.43 (dd, 2H, J ) 8.5,
8.5 Hz), 7.98 (dd, 1H, J ) 8.5, 2.5 Hz), 7.83 (ddd, 1H, J ) 7.75,
7.75, 2.0 Hz), 7.56 (dd, 1H, J ) 8.5, 4.0 Hz), 7.36 (d, 1H, 3.5 Hz),
7.31 (ddd, 1H, J ) 1.0, 7.0, 5.0 Hz), 7.21 (d, 1H, J ) 3.5 Hz),
7.20 (dd, 1H, J ) 3.0, 3.0 Hz), 7.18 (d, 1H, J ) 3.5 Hz), 7.16 (d,
1H, J ) 3.5 Hz), 7.13 (d, 1H, J ) 4.0 Hz), 7.12 (H11-14, d, 1H,
J ) 3.0 Hz). 13C NMR (CDCl3, 125 MHz): δ 155.9, 155.2, 149.5,
146.2, 139.6, 137.8, 137.7, 137.2, 136.6, 136.1, 135.0, 133.5, 130.1,
126.2, 125.7, 125.4, 125.2, 125.1, 125.0, 124.8, 124.6, 124.4, 124.0,
[5′-(2,2′-Bipyridin-5-yl)-2,2′-bithien-5-ylphosphonic acid]bis-
(bipyridyl)ruthenium(II) Hexafluorophosphate (21). To 25 mL
of H2O were added 9 (0.204 g, 0.510 mmol), RuCl2(bpy)2
(0.249 g, 0.514 mmol), and NaOH (21.3 mg, 0.533 mmol). The
mixture was refluxed for 3 h. After cooling, the mixture was
acidified with 1 M HCl and filtered to remove unreacted starting
material. KPF6 (0.427 g, 2.32 mmol) in 10 mL of water was added
which precipitated a red solid. The solid was collected by
centrifugation. It was then dissolved in acetone, transferred to a
round-bottom flask, and evaporated to dryness. The product
(0.490 g, 0.444 mmol, 87%) was collected as a red/brown solid
1
(dec >180 °C). H NMR (DMSO, 500 MHz): δ 8.91-8.84 (m,
6H), 8.46 (d, 1H, J ) 8.0 Hz), 8.28 (dd, 1H, J ) 8.0, 8.0 Hz),
8.21-8.16 (m, 4H), 7.94 (d, 1H, J ) 5.0 Hz), 7.85 (d, 1H, J )
5.0 Hz), 7.77-7.74 (m, 3H), 7.66-7.61 (m, 2H), 7.56-7.52 (m,
5H), 7.46 (d, 1H, J ) 4.0 Hz), 7.38 (dd, 1H, J ) 3.5, 7.5 Hz), 7.35
(d, 1H, J ) 3.0 Hz). 31P NMR (DMSO, 121 MHz): δ 4.83 (s).
UV-vis (NCCH3) λ, nm (ꢀ, M-1 cm-1): 244 (27000), 287 (78000),
397 (41000), 462 (18000). HRMS (ESI-TOF) m/z calcd for
C38H29N6O3PS2Ru (M)+2 407.0256; found 407.0264. Anal. Calcd
for C38H29N6O3F12P3S2Ru: C, 41.35; H, 2.65; N, 7.61. Found C,
41.49; H, 2.80; N, 7.62.
121.3, 121.3, 63.0 (C-P J ) 5.5 Hz), 16.5 (C-P J ) 6.0 Hz). 31
P
NMR (CDCl3, 121 MHz): δ 11.44 (s). UV-vis (NCCH3) λ, nm
(ꢀ, M-1 cm-1): 250 (18000), 286 (16000), 422 (38000). HRMS
(ESI-TOF) m/z calcd for C30H25N2O3PS4 (M + H)+ 621.0558; found
621.0559. Anal. Calcd for C30H25N2O3PS4: C, 58.04; H, 4.06; N,
4.51. Found C, 57.71; H, 4.02; N, 4.29.
[5′-(2,2′-Bipyridin-4-yl)-2,2′-bithien-5-ylphosphonic acid]bis-
(bipyridyl)ruthenium(II) Hexafluorophosphate (22). To 25 mL
of H2O were added 11 (0.199 g, 0.499 mmol), RuCl2(bpy)2
(0.264 g, 0.545 mmol), and NaOH (24.4 mg, 0.61 mmol). The
mixture was refluxed for 2.5 h. After cooling, the mixture was
acidified with about 1.0 mL of 1 M HCl and filtered to remove
unreacted starting material. KPF6 in 10 mL of H2O (0.49 g,
2.7 mmol) was added, which precipitated a red solid. The mixture
was filtered through a medium fritted filter. Product (0.410 g, 0.371
mmol, 74%) was washed with ether and dried (mp 232-237 °C).
1H NMR (DMSO, 500 MHz): δ 9.14 (d, 1H, J ) 8.5 Hz), 9.08 (d,
1H, J ) 2.0 Hz), 8.88-8.85 (m, 4H), 8.24-8.16 (m, 6H), 7.90 (d,
1H, J ) 2.5 Hz), 7.77-7.74 (m, 4H), 7.71 (dd, 1H, J ) 2.0,
6.0 Hz), 7.66 (d, 1H, J ) 3.5 Hz), 7.62 (d, 1H, J ) 6.5 Hz), 7.57-
7.53 (m, 5H), 7.49 (dd, 1H, J ) 3.0, 3.0 Hz), 7.42 (dd, 1H, J )
3.5, 8.0 Hz). 31P NMR (DMSO, 121 MHz): δ 5.12 (s). UV-vis
(NCCH3) λ, nm (ꢀ, M-1 cm-1): 245 (34000), 288 (75000), 384
(32000), 466 (28000). HRMS (ESI-TOF) m/z calcd for C38H29N6O3-
PS2Ru (M)2+ 407.0256; found 407.0256. Anal. Calcd for C38H29N6O3-
F12P3S2Ru: C, 41.35; H, 2.65; N, 7.61. Found C, 41.06; H, 2.73;
N, 7.85.
5-Bromo-5′-(2,2′-bipyridin-4-yl)-2,2′-bithiophene (18). To
200 mL of 1:1 CHCl3:acetic acid were added 17 (1.00 g, 3.12 mmol)
and NBS (0.56 g, 3.14 mmol). The reaction was heated to 60 °C
and was maintained at that temperature for 15 min before cooling.
The mixture was poured into 50 mL of water, and the layers were
separated. The aqueous layer was extracted with CHCl3 (2 ×
50 mL), and the combined organic extracts were washed with K2-
CO3(aq) until neutral. The organic layer was then dried over MgSO4,
filtered, and evaporated. Product (1.20 g, 3.00 mmol, 96%) was
collected as an orange solid (mp 137-141 °C, with partial
1
decomposition). H NMR (CDCl3, 300 MHz): δ 8.72 (dm, 1H,
J ) 4.0 Hz), 8.64 (dd, 1H, J ) 5.0, 1.0 Hz), 8.60 (dm, 1H, J )
2.0 Hz), 8.42 (ddd, 1H, J ) 8.0, 1.0, 1.0 Hz), 7.83 (ddd, 1H, J )
2.0, 8.0, 8.0 Hz), 7.53 (d, 1H, J ) 4.0 Hz), 7.44 (dd, 1H, J ) 3.0,
5.0 Hz), 7.33 (dd, 1H, J ) 1.0, 8.0, 5.0), 7.12 (d, 1H, J ) 4.0 Hz),
7.00 (d, 1H, J ) 4.0 Hz), 6.97 (d, 1H, J ) 4.0 Hz). 13C NMR
(CDCl3, 125 MHz): δ 157.1, 156.0, 150.0, 149.3, 142.0, 140.5,
138.5, 138.2, 137.2, 131.0, 126.6, 125.1, 124.6, 124.2, 121.4, 119.6,
6660 J. Org. Chem., Vol. 72, No. 18, 2007

Bifunctional Thiophene Molecules Coordinated to Ru
[5′′′-(2,2′-Bipyridin-5-yl)-2,2′-5′,2′′-5′′,2′′′-tetrathien-5-ylphos-
phonic acid]bis(bipyridyl)ruthenium(II) Hexafluorophosphate
(23). Compound 15 (0.213 g, 0.343 mmol) was placed in a Schlenk
flask under N2. TMSBr (1.0 mL, 7.6 mmol) was added by syringe.
The slurry was stirred for 16 h. Some of the TMSBr evaporated,
leaving a thick slurry. Three milliliters of CHCl3 was added, and it
was quenched with water. The slurry was filtered with difficulty,
washed with acetonitrile, and dried to form 16, a dark red solid
(0.155 g, 0.27 mmol, 80%, dec 250 °C).
0.123 g, 89%, dec 245 °C) was washed extensively with acetonitrile
and then dried. NMR and MS spectra were not recorded because
of the insolubility of the product.
To 30 mL of H2O in a round-bottom flask were added 20
(76.2 mg, 0.135 mmol), RuCl2(bpy)2 (66.0 mg, 0.136 mmol), and
NaOH (5 mg, 0.1 mmol). The mixture was heated to reflux for
16 h. After cooling, the mixture was filtered through celite to
remove unreacted starting material. The solid was washed with basic
water until the filtrate ran pale. KPF6 (0.20 g, 1.1 mmol) in 5 mL
of H2O was added to the filtrate with no result. A 10 mL amount
of 1 M HCl was added, which caused a red/orange solid to
precipitate. The solid was collected by centrifugation and washed
once with water. The solid was then suspended in acetonitrile and
transferred to a round-bottom flask. The solvent was evaporated,
leaving 24 as a red solid (0.109 g, 0.086 mmol, 64%, dec
>190 °C). 1H NMR (DMSO, 500 MHz): δ 9.17 (d, 1H, J ) 8.0),
9.09 (s, 1H), 8.86 (m, 4H), 8.24-8.15 (m, 6H), 7.90 (d, 1H, J )
5.5 Hz), 7.76-7.73 (m, 4H), 7.68 (d, 1H, J ) 6.5 Hz), 7.61 (d,
2H, J ) 5.0 Hz), 7.56-7.53 (m, 5H), 7.48 (d, 1H, J ) 4.0 Hz),
7.42-7.37 (m, 5H). 31P NMR (DMSO, 121 MHz): δ 5.32 (s). UV-
vis (NCCH3) λ, nm (ꢀ, M-1 cm-1): 245 (38000), 289 (75000), 437
(49000), 478 (46000). HRMS (ESI-TOF) m/z calcd for C46H33N6O3-
PS4Ru (M)+2 489.0134; found 489.0135. Anal. Calcd for C46H33N6O3-
F12P3S4Ru: C, 43.57; H, 2.62; N, 6.63. Found C, 43.76; H, 2.64;
N, 6.54.
To 25 mL of water in a round-bottom flask were added 16
(0.147 g, 0.26 mmol), RuCl2(bpy)2 (0.130 g, 0.27 mmol), and NaOH
(17 mg, 0.425 mmol). The mixture was refluxed for 4 h. After
cooling, a solution of KPF6 (0.29 g, 1.6 mmol) in 10 mL of 0.3 M
HCl was added and a red precipitate formed. The solid was collected
by centrifugation, and the mother liquor was decanted. The solid
was dissolved in DMF and collected in a round-bottom flask, and
the DMF was evaporated. Product, 0.252 g (0.20 mmol, 76%), was
1
collected as a dark red solid (dec ∼210 °C). H NMR (DMSO,
500 MHz): δ 8.93 (d, 1H, J ) 8.5 Hz), 8.90-8.85 (m, 5H), 8.47
(d, 1H, J ) 8.5 Hz), 8.32 (t, 1H, J ) 8.0 Hz), 8.22-8.16 (m, 4H),
7.97 (m, 1H), 7.88 (d, 1H, J ) 5.5 Hz), 7.78 (m, 2H), 7.75 (d, 1H,
J ) 5.5 Hz), 7.66 (t, 1H, J ) 6.5 Hz), 7.61 (s, 1H), 7.56 (m, 5H),
7.46 (d, 1H, J ) 3.5 Hz), 7.42 (d, 1H, J ) 3.5 Hz), 7.40-7.38 (m,
4H), 7.36 (d, 1H, J ) 3.5 Hz). 31P NMR (DMSO, 121 MHz): δ
4.83 (s). UV-vis (NCCH3) λ, nm (ꢀ, M-1 cm-1): 245 (32000),
288 (75000), 446 (52000), 480 (39000). HRMS (ESI-TOF) m/z
calcd for C46H33N6O3PS4Ru (M)+2 489.0134; found 489.0136. Anal.
Calcd for C46H33N6O3F12P3S4Ru: C, 43.57; H, 2.62; N, 6.63. Found
C, 43.27; H, 2.87; N, 6.44.
Acknowledgment. We thank Brigham Young University for
financial support and for a graduate student fellowship for J.S.B.
We are grateful to Dr. Matthew Asplund for assistance measur-
ing fluorescent lifetimes.
[5′′′-(2,2′-Bipyridin-4-yl)-2,2′-5′,2′′-5′′,2′′′-tetrathien-5-ylphos-
phonic acid]bis(bipyridyl)ruthenium(II) Hexafluorophosphate
(24). Compound 19 (0.152 g, 0.245 mmol) was placed in a Schlenk
flask under N2, and TMSBr (1.0 mL, 7.6 mmol) was added by
syringe. The slurry was left to stir overnight. Some TMSBr had
evaporated, leaving a thick slurry. One milliliter of CHCl3 was
added, followed by 1 mL of acetonitrile. The reaction was then
quenched with water, and a precipitate formed. The product (20,
Supporting Information Available: General procedures, syn-
thetic procedures for 2, 3, and 6, and 1H NMR spectra of selected
compounds. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO070377O
J. Org. Chem, Vol. 72, No. 18, 2007 6661