3,7-diazadibenzophosphole oxide: A phosphorus-bridged viologen analogue with significantly lowered reduction threshold

Article abstract of DOI:10.1002/anie.201102453

Phosphorus pulls its weight: Installation of a phosphoryl group as central bridge in the 4,4′-bipyridine scaffold introduces improved reduction responses that become even more pronounced in the corresponding phosphoryl-bridged methylviologen (see picture)

Full text of DOI:10.1002/anie.201102453

Communications
DOI: 10.1002/anie.201102453
Viologen Analogues
3
,7-Diazadibenzophosphole Oxide: A Phosphorus-Bridged Viologen
Analogue with Significantly Lowered Reduction Threshold**
Stefan Durben and Thomas Baumgartner*
[
1]
4
,4’-Bipyridine (1) and its N-alkylated congeners are classic
We now report the synthesis and characterization of a 3,7-
diazadibenzophosphole oxide, which can be considered a
phosphorus-bridged viologen precursor, and its subsequent
organic building blocks that have been utilized in a variety of
electrochemistry, solar-
energy conversion, and as bridging ligands in metallosu-
pramolecular assemblies, or molecular wires. Methylviol-
ogen MV , or paraquat, easily accessible from 4,4’-bipyridine
by methylation (Scheme 1), is frequently used as a photo-
[
1b]
[1c]
fields, such as photochemistry,
[
1d]
2+
conversion into the dimethylated phospha-MV species. Our
[
1e]
study shows that incorporation of the bridging phosphoryl
group dramatically enhances the electron-acceptor features
2
+
2
+
of the scaffold, while maintaining MV -analogue stability
and responses.
To synthesize the title compound using our established
[7]
method towards ring-fused phospholes, 3,3’-dibromo-4,4’-
bipyridine (3) had first to be prepared on a synthetically
useful scale. Despite the fact that compound 3 had been
reported before, the procedure outlined was tedious only
2
+
Scheme 1. Synthesis and reduction of methylviologen (MV ).
[8]
providing 3 in very low yield and analytical amounts. To gain
access to the starting material 3 in synthetically useful
[
9]
amounts, we applied an Ullmann coupling of 3-bromopyr-
idine (2) to afford the target bipyridine in moderate yield
(44%; Scheme 2). Remarkably, the reaction involves only
[
2a]
[2b]
chemical probe,
an electrochemical label,
or a co-
sensitizer in studies concerning the electron-transport pro-
cesses or oxidative damage in DNA.
The high practical value of MV
[
3]
2
+
is based on its
pronounced electron-acceptor character and the change
between intense colors (purple and orange) for the radical
+
cation (MVC ), and the neutral species (MV), respectively,
that make the reduction event(s) easily detectable by optical
[
1a]
spectroscopy or even the naked eye.
In the context of systematic studies on phosphorus-
containing p-conjugated materials for organic electronics,
[
4]
[5]
our group and others could confirm the highly tunable,
favorable electron-acceptor features that are attributable to
the electronic nature of phosphorus. Recently we have
extended our studies toward p-conjugated phospholes with
pyridine units as integral part of the scaffold and were able to
establish the highly functional nature, as well as the pro-
nounced electron-accepting features of these systems, partic-
Scheme 2. Synthesis and reactivity of 3,7-diazadibenzophosphole oxide
4
: a) 1. LDA (À858C, THF), 2. CuCl , 3. air. b) 1. 2 nBuLi (À858C,
2
THF), 2. PhPCl , 3. H O (excess, CHCl ). c) 2 MeOTf, CH Cl , room
2
2
2
3
2
2
temperature.
[6]
ularly for the phosphole oxides.
inexpensive starting materials and was proven to be scalable,
so that bipyridine 3 could be obtained on a gram scale within
two days. Multinuclear NMR spectroscopy, mass spectrome-
try and elemental analysis confirmed the formation of
compound 3. In addition, single-crystals, suitable for X-ray
crystallography were also obtained (see the Supporting
Information).
[
*] Dr. S. Durben, Prof. Dr. T. Baumgartner
Department of Chemistry, University of Calgary
2500 University Drive NW, Calgary, AB T2N 1N4 (Canada)
E-mail: thomas.baumgartner@ucalgary.ca
Homepage: http://www.ucalgary.ca/chem/pages/Baumgartner
[
**] Financial support by NSERC of Canada and the Canada Foundation
for Innovation (CFI) is gratefully acknowledged. We also thank
Alberta Ingenuity, now part of Alberta Innovates—Technology
Futures, for a graduate scholarship (S.D.) and a New Faculty Award
The best results for the synthesis of 4 were obtained by
treatment of 3 with two equivalents nBuLi at À858C in THF
[10]
(
4
(
Scheme 2); diazadibenzophosphole oxide 4 was isolated in
(
T.B.). Thanks to Prof. T. Sutherland for his help with the electro-
chemical studies, as well as Dr. T. Linder and Prof. U. Englert
RWTH Aachen University) for helpful discussions with regard to X-
3
1
9% yield as colorless solid. The P NMR resonance of 4
d P = 33.6 ppm) agrees well with that observed for the 3-
azadibenzophosphole oxide analogue (d P = 34.0 ppm) and
dibenzophosphole oxide (d P = 31.4 ppm).
3
1
(
3
1
[6]
ray crystallography.
3
1
[11a]
Single crystals,
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201102453.
suitable for X-ray crystallography, were obtained from a
7948
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Angew. Chem. Int. Ed. 2011, 50, 7948 –7952

[12]
[6]
concentrated solution of 4 in ethanol upon evaporation.
compared to 3-azadibenzophosphole oxide (DE = 0.29 V),
The structure (Figure 1) exhibits a planar backbone with
small CÀC and CÀN bond-length alternation and shows
essentially equidistant endo- and exocyclic PÀC bond lengths
due to the presence of the second nitrogen within the scaffold
of 4. Since the material revealed reversible one-electron
reduction events, assessed by the separation between anodic
and cathodic peak potentials, its electron-transfer constant
[13]
kET was evaluated. 3,7-Diazadibenzophosphole 4 shows a
À4
À1
lower kET = 2.01 ꢁ 10 cms than those observed in the
[
6]
azadibenzophospholes, probably due to the less polar
backbone structure, resulting in lower mobility in an electric
field. Nevertheless, the obtained kET value indicates suffi-
ciently fast electron-transfer processes that are beneficial for
[14]
an application in electronic devices, well within the range of
previously reported phosphadiazole-oxide, thiadiazole, thia-
diazole-oxide and -dioxide fused phenanthrenes, and pyr-
[15]
enes.
After having established synthetic access to the 3,7-
diazadibenzophosphole oxide 4, its reactivity towards tran-
sition metals was investigated. Due to the analogy of the
backbone of 4 to 4,4’-bipyridine, the synthesis of a supra-
molecular square (see Supporting Information), analogous to
Figure 1. Molecular structure of 4 (left) and packing (right) in the solid
state (thermal ellipsoids set at 50% probability, H atoms are omitted
for clarity). See the Supporting Information for detailed metric
parameters.
[
16]
a compound reported by Fujita and co-workers,
was
that are in good agreement with the reported 1-aza-, and 4-
attempted. However, no reaction was observed upon mixing
[
6]
azadibenzophosphole oxide, as well as dibenzophosphole
of 4 with [Pd(bipy)(NO ) ], and slow heating resulted in
3
2
[
11b]
oxide.
decomposition to unidentified products, as confirmed by
NMR spectroscopy and MALDI-TOF mass spectrometry.
The lack of success can be explained by the electron-
withdrawing effect of the phosphoryl group, making 4 a
The packing in 4 shows a layered motif with two different
face-to-face interactions. The layers with the O-atoms point-
ing toward each other show a strong p-stacking interaction
with a distance of 3.41 ꢀ, whereas the layers with the phenyl
rings pointing toward one another show weaker face-to-face
interactions with a distance of 3.61 ꢀ.
2
+
weak N-donor system not capable of coordination to two Pd
centers. Furthermore, owing to the distortion of the back-
bone, the arrangement of the N donors in 4 is such that the
formation of an ideal square complex is not possible, the
geometry of the product would be a distorted square with
considerable ring strain. Alternatively, the synthesis of a
coordination polymer was attempted by treatment of 4 with
0.9 equivalents of K [PtCl ], affording a poorly soluble, bright
The photophysical features of 4 were investigated by UV/
Vis spectroscopy in dichloromethane (Table 1). The spectrum
(
Supporting Information) shows an absorption profile with a
maximum at l = 276 nm and a molar absorptivity of e276
=
max
À1
À1
1
2
0750 Lmol cm , as well as shoulders at 305 nm and
69 nm; the onset of absorption is found at lonset = 330 nm.
2
4
1
31
orange solid. Despite the fact that H and P NMR spectros-
copy and UV/Vis spectroscopy, as well as MALDI-TOF
spectrometry (see the Supporting Information) suggest the
formation of oligomeric species, the insolubility of the
material precluded a clear assignment of its structure.
However, note in this context that the analogous reaction
using the related monodentate 3-azadibenzophosphole (L) as
ligand cleanly results in the formation of the [Pt(L) Cl ]
The photophysical features are comparable to those observed
[
6]
for the azadibenzophosphole oxides.
2
+
.
Table 1: Photophysical and electrochemical features of 3–5 and MV
À1
À1
Ered[b] [V]
Eox[b] [V]
Compd
lmax[a] [nm]
e [Lmol cm
]
3
4
5
272
276
288
5340
10750
17720
À2.58
0.48, 0.95
0.81
–
2
2
[
6]
À1.85, À2.47
À0.51, À1.00
À1.09, À1.52
complex.
,7-Diazadibenzophosphole oxide 4 was subsequently
3
2
+[17]
MV
–
converted into the methylviologen analogue 5 (Scheme 2).
In stark contrast to the metal complexation, the reaction of 4
proceeded cleanly by addition of two equivalents of methyl
À5
[
a] Dichloromethane, cꢀ10 m. [b] CH CN, NBu PF as supporting
3
4
6
+
electrolyte, vs. Fc/Fc .
2
+
triflate, providing phospha-MV 5 in good yield (79%) as
colorless solid. In addition to multinuclear NMR spectrosco-
py and CHN analysis, the formation of 5 was confirmed by X-
ray crystallography (Figure 2). Single crystals were obtained
from a concentrated solution of 5 in ethanol upon cooling to
The electrochemical characteristics of 4 were probed via
cyclic voltammetry (CV), performed in acetonitrile solution
+
at different scan rates and referenced versus Fc/Fc (Fc = [(h-
[12]
C H ) Fe] see the Supporting Information). The cyclic
08C.
5
5 2
voltammograms show a reversible reduction at Ered1,1/2
=
Note that the triflate anions are disordered over two
positions and only the major component is shown. Due to the
symmetry, both pyridinium rings and triflate anions are
equivalent. The triflate anions are located on top of the
annelated backbone, resulting in a short contact between O12
À1.85 V (E = À2.95 eV). Furthermore, another irrever-
LUMO
sible reduction is observed at E
sible oxidative wave can be found at E
= À2.47 V; an irrever-
red2,1/2
= 0.81 V
ox,peak
(
Table 1). The first reduction occurs at a lower potential
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Communications
À3
À1
À3
À1
kET1 = 1.93 ꢁ 10 cms and kET2 = 1.71 ꢁ 10 cms , respec-
[
14]
tively. Compared to 4, the methylated congener 5 shows
increased electron-transfer rates, probably due to the charges,
resulting in a high mobility in an electric field.
As mentioned above, MV and analogues have been
shown to be useful redox-active photochemical probes to
investigate electron-transfer processes from DNA intercala-
2
+
2
+ [2a,3a]
tors (i.e., ruthenium complexes or ethidium) to MV .
The reduction events on MV result in an increase of the
2
+
absorption in the visible range of the spectrum and are
[
2a]
Figure 2. Molecular structure of 5 (left) and packing (right) in the solid
monitored by UV/Vis spectroscopy.
To investigate the
state (thermal ellipsoids set at 50% probability, H atoms are omitted
for clarity). See the Supporting Information for detailed metric
parameters.
suitability of 5 for studies of this kind, the spectroelectro-
chemical features were examined. As shown in Figure 4,
and N1 (2.86 ꢀ). The bond lengths observed in 5 are in good
agreement with those of 4. In the packing diagram, no face-to-
face interactions are observed due to the position of the
anions, preventing close contacts between the p systems, in
favor of dipolar interactions.
2
+
The photophysical features of the phospha-MV 5 were
investigated via UV/Vis spectroscopy. The absorption profile
is featureless with a maximum at l = 288 nm and a molar
max
À1
À1
absorptivity of e288 = 17720 Lmol cm , comparable to that
of 4 (Table 1). Cyclic voltammetry of 5 revealed two
reversible reductions at Ered1,1/2 = À0.51 V (ELUMO
=
À4.29 eV) and Ered2,1/2 = À1.00 V, respectively (Figure 3).
Figure 4. Spectroelectrochemistry of compound 5 in acetonitrile at
+
E=0.0 V (c), À0.6 V (g, 5 ), and À1.1 V (b, 5 ) vs. Fc/Fc .
red1
red2
Inset: magnification of the visible-light region.
2
+
without applied potential (0.0 V), the phospha-MV 5 shows
no significant absorption in the visible range of the spectrum.
After application of a potential (À0.6 V), resulting in the
reduction of 5 to the corresponding monocation radical 5
,
red1
the absorption in the visible range of the optical spectrum is
significantly increased over a wide spectral window, as
+
expected for the reduced monocation radical. MVC (the
2
+
product for reduction of MV ) also shows a broad absorption
over the whole visible range of the spectrum, due to its
[18]
charge-transfer nature, with a maximum at labs = 605 nm.
The second reduction, resulting in the formation of the
neutral 5red2, leads to a slightly decreased absorptivity
Figure 3. Cyclic voltammograms of 5 in CH CN solution at varying
3
À1
scan rates (10, 20, 50, 100, 200, 500, 1000, 1500, and 2000 mVs
;
(Figure 4).
peak height increases with increasing scan rate). NBu PF as support-
4
6
+
However, even after applying a higher potential (À1.1 V),
ing electrolyte; referenced vs. Fc/Fc .
the absorption remains significantly higher than that of the
dication 5. These results, in combination with its solubility in
2
+
The separate electrochemical events result from sequen-
tial one-electron reduction of the individual pyridinium
moieties. The reduction potentials of 5 are significantly
lower than those of both, the starting material 4 and the
water, show that the phospha-MV 5 is well suited for an
application as redox-active photochemical probe, due to its
significant change in the absorption profile upon reduction.
2
+
Its advantage over parent MV lies in the decreased (i.e., less
negative) reduction potentials (5: E =
red2,1/2
2
+
parent MV (Ered1,1/2 = À1.09 V and E
= À1.52 V, vs. Fc/
= À0.51 V, E
red2,1/2
red1,1/2
+
[17]
2+
Fc ), as a result from the methylation and incorporation of
the phosphole oxide, respectively. Both modifications
decrease the energy of the LUMO-levels, facilitating the
reduction. The electron-transfer rates were determined to be
À1.00 V; MV : E
= À1.09 V, E
= À1.52 V, vs. Fc/
red1,1/2
red2,1/2
+
Fc ), inherently leading to increased sensitivity and wider
scope of useable excited-state electron donors with low-lying
LUMO levels.
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Angew. Chem. Int. Ed. 2011, 50, 7948 –7952

To better understand the electronic and photophysical
characteristics, DFT calculations (B3LYP/6-31G*) have been
performed on the diazadibenzophosphole oxide 4, the
dimethylated congener 5, and the corresponding native
Importantly, the reduction of the system can be achieved at
significantly lower potential (DEred > 0.5 V) than for the
parent viologen system, owing to the planarized geometry,
as well as the electron-withdrawing nature of the phosphoryl
bridge. Our studies suggest considerable practical value of the
new system, for example, in the context of electron-transfer
processes with weaker electron donors. Verifying studies with
corresponding transition-metal complexes and species of
biochemical relevance are currently underway.
2
+ [19,20]
species 1 and MV .
The geometries were fully optimized
and the orbital energies determined (Table 2).
Table 2: Frontier orbital energies [eV] and (character) for 1, 4, 5, and
2
+ [19]
MV
.
[
a]
2+[a]
Orbital
1
4
5
MV
Received: April 8, 2011
Revised: May 19, 2011
Published online: July 5, 2011
LUMO
HOMO
À2.02 (p*)
À2.60 (p*)
À7.37 (p)
À4.18 (p*)
À3.77 (p*)
À8.96 (p)
À8.97 (p)
À8.99 (p)
À7.40 (n )
À7.45 (p )
N
Ph
HOMOÀ1
À7.45 (n )
À7.39 (n )
À7.61 (p )
N
N
Ph
HOMOÀ2
À7.57 (p)
À7.50 (n )
À8.58 (s )
Keywords: 4,4’-bipyridine · nitrogen heterocycles ·
N
P
.
[20]
phosphorus heterocycles · redox chemistry · viologen
[a] Only the cationic portion was calculated using PCM solvation.
The LUMO energy of 4 is significantly stabilized in
[1] a) P. M. S. Monk, The Viologens: Physicochemical Properties,
Synthesis and Applications of the Salts of 4,4’-Bipyridine, Wiley,
Chichester, 1998; b) F. Ito, T. Nagamura, J. Photochem. Photo-
biol. C 2007, 8, 174; c) B. Han, Z. Li, C. Li, I. Pobelov, G. Su, R.
Aguilar-Sanchez, T. Wandlowski, Top. Curr. Chem. 2009, 287,
comparison with 4,4’-bipyridine 1 (DE ꢀ 0.6 eV), while the
HOMO energy level essentially remains the same, despite a
switch in character from nN to p. The energy differences
between HOMO, HOMOÀ1, and HOMOÀ2, representing
either the nitrogen lone pairs or the p system (see Supporting
Information), are minor in both compounds, which supports
the fact that the general reactivity of 4 toward methylation is
not compromised; the phosphoryl bridge largely introduces
increased electron-acceptor features to the system. While the
correlation between computational results for 4 with the
181; d) S. Fukuzumi, Eur. J. Inorg. Chem. 2008, 1351; e) W. Sliwa,
B. Bachowska, T. Girek, Curr. Org. Chem. 2007, 11, 497.
[2] a) P. Fromherz, B. Rieger, J. Am. Chem. Soc. 1986, 108, 5361;
b) S. Takenaka, T. Ihara, M. Takagi, J. Chem. Soc. Chem.
Commun. 1990, 1485.
[
3] a) P. K. Bhattacharya, J. K. Barton, J. Am. Chem. Soc. 2001, 123,
8649; b) M. Hariharan, J. Joseph, D. Ramaiah, J. Phys. Chem. B
2006, 110, 24678; c) Y. Li, U. H. Yildiz, K. Mꢂllen, F. Grçhn,
experimental electrochemical data is fair (from CV: ELUMO
=
Biomacromolecules 2009, 10, 530; d) R. E. Holmlin, P. J. Dand-
liker, J. K. Barton, Angew. Chem. 1997, 109, 2830; Angew. Chem.
Int. Ed. Engl. 1997, 36, 2714.
À2.95 eV; calculated: E = À2.60 eV), the calculated
LUMO
LUMO level of dication 5 (E
= À4.18 eV) agrees very
[20]
LUMO
well with that determined by CV (ELUMO = À4.29 eV); as
[4] a) Y. Dienes, M. Eggenstein, T. Kꢃrpꢃti, T. C. Sutherland, L.
Nyulꢃszi, T. Baumgartner, Chem. Eur. J. 2008, 14, 9878; b) Y.
Ren, Y. Dienes, S. Hettel, M. Parvez, B. Hoge, T. Baumgartner,
Organometallics 2009, 28, 734; c) Y. Ren, T. Baumgartner,
Chem. Asian J. 2010, 5, 1918; d) Y. Ren, T. Baumgartner, J. Am.
Chem. Soc. 2011, 133, 1328.
expected, it is significantly stabilized compared to that of 4
2
+
(
DE ꢀ 1.6 eV), but also that of MV (DE ꢀ 0.4 eV). The
character of the LUMO in 5 is very similar to that for 4 and
2
+
MV , representing a quinoidal p* system. It is interesting to
note, however, that the HOMO level of 5 shows no
contribution from the main p system, only the p system of
the exocyclic phenyl ring is represented; the same is true for
[
5] a) A. Fukazawa, M. Hara, T. Son, E.-C. Okamoto, C. Xu, K.
Tamao, S. Yamaguchi, Org. Lett. 2008, 10, 913; b) A. Fukazawa,
Y. Ichihashi, Y. Kosaka, S. Yamaguchi, Chem. Asian J. 2009, 4,
1729; c) A. Saito, T. Miyajima, M. Nakashima, T. Fukushima, H.
Kaji, Y. Matano, H. Imahori, Chem. Eur. J. 2009, 15, 10000; d) T.
Miyajima, Y. Matano, H. Imahori, Eur. J. Org. Chem. 2008, 255;
e) Y. Matano, T. Miyajima, T. Fukushima, H. Kaji, Y. Kimura, H.
Imahori, Chem. Eur. J. 2008, 14, 8102.
2+
the HOMOÀ1. Since MV does not have this structural
feature, the essentially degenerate HOMO, HOMOÀ1, and
HOMOÀ2 involve the p system, however at lower energy
than the corresponding orbitals for 5 (DE ꢀ 0.4–1.5 eV).
In conclusion, we have successfully synthesized 3,3’-
dibromo-4,4’-bipyridine in reasonable quantities for the first
time, which has allowed us to access a novel phosphorus-
bridged viologen analogue. Owing to the pronounced elec-
tron-acceptor character of the phosphoryl bridge, the com-
pound shows reversible reduction features, but only a limited
capacity to act as a rigid bidentate ligand for transition-metal
species through the nitrogen centers. However, methylation
of the nitrogen centers is clearly possible, providing the water-
[6] S. Durben, T. Baumgartner, Inorg. Chem. 2011, 50, DOI:
10.1021/ic200951x.
[
7] a) T. Baumgartner, T. Neumann, B. Wirges, Angew. Chem. 2004,
16, 6323; Angew. Chem. Int. Ed. 2004, 43, 6197; b) T.
1
Baumgartner, W. Bergmans, T. Kꢃrpꢃti, T. Neumann, M.
Nieger, L. Nyulꢃszi, Chem. Eur. J. 2005, 11, 4687; c) C.
Romero-Nieto, S. Merino, J. Rodrꢄguez-Lꢅpez, T. Baumgartner,
Chem. Eur. J. 2009, 15, 4135; d) Y. Dienes, U. Englert, T.
Baumgartner, Z. Anorg. Allg. Chem. 2009, 635, 238.
[8] a) S. Kanoktanaporn, J. A. H. MacBride, J. Chem. Soc. Perkin
Trans. 1 1978, 1126; b) M. Abboud, V. Mamane, E. Aubert, C.
Lecomte, Y. Fort, J. Org. Chem. 2010, 75, 3224.
2
+
soluble phospha-MV 5 with a further lowering of the
reduction potentials. This species can be reversibly reduced in
two steps and the reduction can be monitored by optical
spectroscopy, as the reduction events correlate well with the
formation of strongly absorbing charge-transfer species,
[
9] M. B. Smith, J. March, Marchꢀs Advanced Organic Chemistry:
Reactions, Mechanisms, and Structure, 5th ed., Wiley, New York,
2001.
[
10] a) P. N. W. Baxter, Chem. Eur. J. 2003, 9, 2531; b) F. Trꢆcourt, M.
Mallet, O. Mongin, G. Quꢆguiner, J. Org. Chem. 1994, 59, 6173.
2
+
similar to those observed for the parent MV system.
Angew. Chem. Int. Ed. 2011, 50, 7948 –7952
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
7951

Communications
[
11] a) S. Affandi, J. H. Nelson, N. W. Allcock, O. W. Howard, E. C.
model. CCDC 820571, 820572-820573 contain the supplemen-
tary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[13] R. S. Nicholson, Anal. Chem. 1965, 37, 1351.
Alyea, G. M. Sheldrick, Organometallics 1988, 7, 1724; b) A.
Decken, personal communication, 2004, see CCDC 254271.
12] Crystal data for 4: (C H N OP): M = 278.24, T= 173(2) K,
[
1
6
11
2
r
ꢀ
triclinic, space group P1, a = 7.6072(4), b = 9.5827(3), c =
1
6
0
0.0206(5) ꢀ, a = 87.971(3), b = 72.078(2), g = 67.961(2)8, V=
[14] See, for example: a) S. Gꢂnes, H. Neugebauer, N. S. Sariciftci,
Chem. Rev. 2007, 107, 1324; b) J. Peet, J. Y. Kim, N. E. Coates,
W. L. Ma, D. Moses, A. J. Heeger, G. C. Bazan, Nat. Mater. 2007,
6, 497; c) S. H. Park, A. Poy, S. Beauprꢆ, S. Cho, N. Coates, J. S.
Moon, D. Moses, M. Leclerc, K. Lee, A. J. Heeger, Nat.
Photonics 2009, 3, 297.
[15] a) T. Linder, T. C. Sutherland, T. Baumgartner, Chem. Eur. J.
2010, 16, 7101; b) T. Linder, E. Badiola, T. Baumgartner, T. C.
Sutherland, Org. Lett. 2010, 12, 4520.
[16] a) M. Fujita, J. Yazaki, K. Ogura, J. Am. Chem. Soc. 1990, 112,
5645; b) C. Janiak, Dalton Trans. 2003, 2781.
[17] C. L. Bird, A. T. Kuhn, Chem. Soc. Rev. 1981, 10, 49.
[18] M. Ito, T. Kuwana, J. Electroanal. Chem. 1971, 32, 415.
[19] Gaussian 03, Revision E.01, M. J. Frisch, et al. Gaussian Inc.,
Wallingford, CT, 2007; see Supporting Information.
3
À3
À1
41.59(5) ꢀ , Z = 2, 1
= 1.440 Mgm , m = 0.210 mm , l =
calcd
.71070 ꢀ, qmax = 27.568, 9205 measured reflections, 2867 [R-
2
(
int) = 0.0921] independent reflections, GOF on F = 1.158, R =
1
0.0552, wR = 0.1473 (I > 2s(I)), R = 0.0661, wR = 0.1660 (for
2
1
2
all data), largest difference peak and hole 0.351 and
À3
À0.409 eꢀ ; Crystal data for 5: (C H F N O PS ): M =
2
0
17
6
2
7
2
r
6
1
2
06.45, T= 173(2) K, orthorhombic, space group Pnma, a =
3.0018(4),
b = 16.7820(6),
526.01(15) ꢀ , Z = 4, 1calcd = 1.595 Mgm
c = 11.5768(4) ꢀ,
V=
3
À3
À1
,
m = 0.363 mm
,
l = 0.71070 ꢀ, qmax = 27.488, 14507 measured reflections, 2985
2
[
R(int) = 0.0681] independent reflections, GOF on F = 1.153,
R = 0.0644, wR = 0.1776 (I > 2s(I)), R = 0.0833, wR = 0.2064
1
2
1
2
(
for all data), largest difference peak and hole 0.536 and
À3
À0.437 eꢀ . The intensity data were collected on a Nonius
KappaCCD diffractometer with graphite monochromated Mo
[20] Only the cationic portion was calculated for the methylated
Ka
2+
radiation. The structure was solved by direct methods
species 5 and MV . To account for this truncation, a PCM
2
(
SHELXTL) and refined on F by full-matrix least-squares
solvation model (acetonitrile) was employed.
techniques. Hydrogen atoms were included by using a riding
7952
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ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2011, 50, 7948 –7952