Synthesis and electronic properties of monodisperse oligophenothiazines

Article abstract of DOI:10.1002/chem.200701341

Starting from N-hexylphenothiazine, a versatile construction kit of brominated and borylated phenothiazines can be easily prepared by a sequence of bromination, bromo-lithium exchange/borylation, and Suzuki coupling. Subsequent Suzuki arylation of the building blocks gives soluble, monodisperse, and structurally well defined oligophenothiazines in good yields. The molecular weights at the peak maximum (M_p), obtained by GPC (gel permeation chromatography), and the actual molecular weights of the oligomer series, obtained by mass spectrometry, show excellent correlation. A QM/MM conformational analysis for the complete series reveals that the obvious butterfly-shaped phenothiazine structure multiplies and significantly reduces the hydrodynamic volume of the oligomers. The electronic properties (absorption and emission spectroscopy and cyclic voltammetry) give reasonable correlations with the chain length. With regard to the emission maxima, the effective conjugation length is already reached with the hexamer. Oligophenothiazines are highly fluorescent, with high fluorescence quantum yields, and are simultaneously highly electroactive, with low oxidation potentials.

Full text of DOI:10.1002/chem.200701341

DOI: 10.1002/chem.200701341
Synthesis and Electronic Properties of Monodisperse Oligophenothiazines
[
a]
Markus Sailer, Adam W. Franz, and Thomas J. J. Müller*
Dedicated to Professor Dr. Herbert Mayr on the occasion of his 60th birthday
Abstract: Starting from N-hexylpheno-
thiazine, a versatile construction kit of
brominated and borylated phenothia-
zines can be easily prepared by a se-
quence of bromination, bromo–lithium
exchange/borylation, and Suzuki cou-
pling. Subsequent Suzuki arylation of
the building blocks gives soluble, mon-
odisperse, and structurally well defined
oligophenothiazines in good yields. The
molecular weights at the peak maxi-
actual molecular weights of the oligo-
mer series, obtained by mass spectrom-
the oligomers. The electronic proper-
ties (absorption and emission spectros-
copy and cyclic voltammetry) give rea-
sonable correlations with the chain
length. With regard to the emission
maxima, the effective conjugation
length is already reached with the
hexamer. Oligophenothiazines are
highly fluorescent, with high fluores-
cence quantum yields, and are simulta-
neously highly electroactive, with low
oxidation potentials.
etry, show excellent correlation.
A
QM/MM conformational analysis for
the complete series reveals that the ob-
vious butterfly-shaped phenothiazine
structure multiplies and significantly
reduces the hydrodynamic volume of
Keywords: C–C coupling · cyclic
voltammetry
·
fluorescence
·
mum (M ), obtained by GPC (gel per-
p
heterocycles · oligomerization
meation chromatography), and the
Introduction
mers. For instance, questions about the effective conjugation
lengths and about reliable electronic structure/property rela-
[9]
In the past decades conjugated polymers have attracted
much scientific and technological research interest, due to
their potential uses as semiconductors and electroactive ma-
tionships can be tackled and answered. Likewise, well de-
fined conjugated oligomers are key elements in molecular
[10]
electronics.
[
1]
terials in diverse applications such as transistors, photovol-
Among numerous p systems suitable for repetitive synthe-
[2]
[3]
[11]
taic devices, nonlinear optical devices, and polymer light-
ses of well defined oligomers, electron-rich entities are of
[4,5]
emitting diodes (PLEDs).
In particular, the search for
peculiar interest due to their ease of oxidation. In particular,
reversibly oxidizable heterocyclic redox systems can be very
promising not only for the design of suitable hole-transport
materials for molecule-based OLED and OFET (organic
field effect transistor) devices but also for switchable molec-
ular wires for future molecular electronics. Most prominent-
[
6,7]
PLEDs fabricated from conjugated polymers
has intensi-
fied tremendously because of their favorable properties for
the design of flat panel displays, such as good processability,
low operating voltages, fast response times, and ease of
color tunability over the full visible range. Still, for a more
profound understanding of structure/property relationships,
shorter, well defined units would be helpful. Therefore,
monodisperse oligomers with extended p-electron delocali-
zation, which are molecularly well defined entities, can be of
fundamental importance for the understanding of the transi-
tion of properties upon going from small molecules to poly-
[12]
[13]
ly, oligothiophenes and oligopyrroles have become well
established in the past. However, polycyclic heterocycles
tend to give more stable radical cations than thiophene or
[
8]
[14]
pyrrole systems upon oxidation. Whereas 3,6-linked and
[15]
2,7-linked di- and tricarbazoles have been synthesized and
studied, the corresponding oligophenothiazines have so far
remained unexplored.
[16]
Phenothiazine derivatives possess low and highly rever-
[16,17]
[
a] Dr. M. Sailer, Dipl.-Chem. A. W. Franz, Prof. Dr. T. J. J. Müller
Institut für Organische Chemie und Makromolekulare Chemie
Heinrich-Heine-Universität Düsseldorf
Universitätsstrasse 1 (26.43.00), 40225 Düsseldorf (Germany)
Fax : (+49)211-81-14324
sible first oxidation potentials
with pronounced propen-
sities to form stable radical cations. As a consequence, the
favorable electronic properties of phenothiazines have led
to applications as electrophore probes in supramolecular as-
[18]
E-mail: ThomasJJ.Mueller@uni-duesseldorf.de
semblies
for PET (photoinduced electron transfer) and
2602
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Chem. Eur. J. 2008, 14, 2602 – 2614

FULL PAPER
sensor studies, and also as electron donor components in
materials science investigations, such as electrically conduct-
synthetic steps (Scheme 1). For the sake of solubility of
higher members of a consanguineous series, n-hexyl groups
were introduced onto the deprotonated phenothiazine nitro-
gen atoms by nucleophilic substitution with 1-bromohexane
to give the N-hexylphenothiazines 1 and 2 in excellent
yields. Upon bromination, 1 was readily converted into the
3,7-dibromo derivative 3, whereas bromophenothiazine 2
was transformed into the boronate 4 by a one-pot sequence
of bromo–lithium exchange, electrophilic trapping with tri-
[19]
[20]
ing charge-transfer composites,
acceptor arrangements.
Therefore, in continuation of our program to synthesize
polymers,
and donor–
[21]
[22]
and study bi- and terphenothiazines with alkynyl, alken-
[
23]
[24]
[25]
yl,
aryl,
and organometallic
bridges and to explore
[
26]
their applications to PET systems, we also became inter-
ested in higher oligomers of phenothiazine as low molecular
weight representatives of polyphenothiazines. Here we
report the synthesis of a homologous series of oligopheno-
thiazines, together with correlation of their actual molecular
weights and gel permeation chromatography, computed
structures, and first electronic properties (cyclic voltamme-
try, absorption and emission spectroscopy).
[24a]
methyl borate, and transesterification with pinacol.
3,7-Dibromo-10-hexyl-10H-phenothiazine (3) is a quite
unique and versatile starting compound that can be trans-
formed by selective monobromine–lithium exchange and
subsequent trapping with an equimolar amount of iodine
[24d]
into the unsymmetrical bromoiodophenothiazine 5,
or by
subsequent transmetalation with copper(i) cyanide and oxi-
dative coupling upon gentle air oxidation at low tempera-
[28]
Results and Discussion
ture to furnish the symmetrical dibrominated diphenothia-
zine 6. Double bromine–lithium exchange on 3, followed by
electrophilic trapping with trimethyl borate and transesteri-
fication with pinacol, gave rise to the formation of the sym-
Synthesis of the oligophenothiazine construction kit: In
recent years we have adapted Suzuki cross-coupling reac-
tions to halogenated and borylated phenothiazines as an ex-
peditious route to phenothiazines with extended p-electron
[24a]
metrical bisboronate 7.
Suzuki coupling of the unsymmetrical bromoiodopheno-
thiazine 5 with boronate 4 gave straightforward access to
the monobrominated diphenothiazine 8, whereas coupling
with the bisboronate 7 furnished the symmetrical bisbromi-
nated terphenothiazine 9 in good yield. Finally, upon subjec-
tion of the bromodiphenothiazine 8 to the sequence of bro-
mine–lithium exchange, electrophilic trapping with trimethyl
borate, and transesterification with pinacol, the diphenothia-
zine boronate 10 can be obtained in decent yield. All com-
pounds have been fully characterized by spectroscopic and
analytical methods. With this expanded set of brominated
and borylated building blocks to hand, the stage for the syn-
thesis of a homologous series of oligophenothiazines had
now been set.
[24]
conjugation. With borylated phenothiazines to hand, the
Suzuki coupling appears to be the arylation method of
choice. Inspired by the synthesis of well defined oligofluor-
[27]
enes we next set out to develop a toolbox of phenothia-
zine derivatives suitable for a selective synthesis of well de-
fined, monodisperse oligophenothiazines.
Starting from 10H-phenothiazine and 3-bromo-10H-phe-
nothiazine, a whole library of brominated and borylated oli-
gophenothiazines can be created in a few straightforward
Abstract in German: Ausgehend von N-Hexylphenothiazin
kann leicht ein vielseitiger Baukasten aus bromierten und
borylierten Phenothiazinen über eine Sequenz aus Bromier-
ung, Bromo–Lithium-Austausch/Borylierung und Suzuki
Kupplung hergestellt werden. Die nachfolgende Suzuki-Ary-
lierung der Bausteine führt in guten Ausbeuten zu lçslichen,
monodispersen und strukturtreuen Oligophenothiazinen. Die
Synthesis of oligophenothiazines: A standard Suzuki proto-
col originally developed for phenothiazine acceptor sys-
[24e]
tems
was successfully adapted for the synthesis of oligo-
phenothiazines ranging from diphenothiazine to heptaphe-
nothiazine (Scheme 2). Treatment of the boronates 4 and 10
with the monobrominated phenothiazine 2 and the dibromi-
nated phenothiazines 3, 6, and 9 in the presence of potassi-
um carbonate in dioxane/water or DME/water, together
with catalytic amounts of palladium(0) tetrakis(triphenyl-
phosphane), for 18 to 48 h gave rise to the selective forma-
tion of the oligophenothiazines 11–16 in good to excellent
yields. The symmetrical molecular structures of the oligo-
phenothiazines are in agreement with the NMR spectro-
Molekulargewichte beim Peakmaximum (M ), die aus GPC
p
(
Gelpermeationschromatographie) erhalten werden und die
tatsächlichen Molekulargewichte der Oligomeren, erhalten
durch Massenspektrometrie, ergeben eine exzellente Korrela-
tion. Die QM/MM-Konformationsanalyse der gesamten Serie
zeigt, das der Effekt der Schmetterlingsstruktur der Pheno-
thiazine sich vervielfältigt und so das hydrodynamische Volu-
men der Oligomere deutlich verkleinert. Die elektronischen
Eigenschaften der Oligomere (Absorptions- und Emissions-
spektroskopie und Cyclovoltammetrie) korrelieren mit der
Kettenlänge. Im Falle der Emissionsmaxima wird die effek-
tive Konjugationslänge bereits mit dem Hexamer erreicht.
Oligophenothiazine fluoreszieren mit hohen Fluoreszenz-
quantenausbeuten und erweisen sich gleichzeitig wegen ihrer
niedrigen Oxidationspotenziale als äußerst elektroaktiv.
1
13
scopic data ( H, C, and DEPT NMR experiments) and
were unambiguously supported by mass spectrometry (FAB,
MALDI-TOF), as well as by IR and UV/Vis spectroscopy
and combustion analyses.
Actual molecular weight and GPC M —conformational
p
analysis: The correlation of the actual molecular weights of
Chem. Eur. J. 2008, 14, 2602 – 2614
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www.chemeurj.org
2603

T. J. J. Müller et al.
Scheme 1. Synthesis of the oligophenothiazine toolbox: a) KOtBu, 1-bromohexane, THF, 668C, 3 h; b) KOtBu, THF, ꢀ788C, 2 h, 1-bromohexane, room
temperature 12 h; c) HOAc, Br
2
, room temperature, 19 h at room temperature; d) nBuLi, THF, ꢀ788C, 15 min, then: B
A
H
R
U
G
3
, 15 min, then:
pinacol, THF, HOAc, room temperature; e) nBuLi, THF, ꢀ788C, 15 min, then: CuCN, TMEDA, 10 min, air, 1 h; f) 4, K
Pd(PPh ], 18 h, 858C; g) 5, K CO , DME/H O (3:1), 5 mol% [Pd(PPh
pinacol, THF, HOAc, room temperature.
2
CO
3
2
[
A
C
H
T
R
E
U
N
G
3
)
4
2
3
2
A
T
E
G
3
)
4
A
H
R
U
G
3
the homologous series of oligophenothiazines 12–16, as de-
termined by mass spectrometry, with relative molecular
weights was studied by gel permeation chromatography
(Figure 1) than with the polystyrene standard (M=
ꢀ
1
2
0.7218 M +332.41 [gmol ]; r =0.9984). Expectedly, GPC
p
underestimates the molecular weights by 28% (polystyrene
standard) and 10% (poly(p-phenylene) standard). However,
the deviation from poly(p-phenylene) can be attributed to
significant conformational divergence from a rigid rod-like
structure (as assumed from the poly(p-phenylene) data)
with effects on the hydrodynamic volume.
(
GPC) in THF with polystyrene and poly(p-phenylene)
standards (Table 1). The molecular weight at the peak maxi-
mum (M ), obtained by GPC along with M and M , was
p
n
w
used for establishing correlations with the molecular masses.
Linear regression of the actual molecular weights M plotted
[29]
against M of polystyrene and poly(p-phenylene) standards
QM/MM calculations
on the oligomers 11–16 were
p
reveals that GPC traces with the poly(p-phenylene) stan-
therefore carried out by optimization of the truncated 10-
ethyl-10H-phenothiazine at a high level of theory by appli-
ꢀ
1
2
dard (M=0.9001 M +190.54 [gmol ]; r =0.9998) gives a
p
better correlation with the actual molecular weights
cation of the B3LYP/6-31+G(d,p) functional, followed by
A
H
R
U
G
2604
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Chem. Eur. J. 2008, 14, 2602 – 2614

Monodisperse Oligophenothiazines
FULL PAPER
Scheme 2. Synthesis of oligophenothiazines: a) 5 mol% [Pd
A
H
R
U
G
3
)
4
], K
2
CO
3
, 1,4-dioxane/H
2
A
T
E
N
3 4 2 3 2
O 2:1, 908C, 2 d; b) 5 mol% [Pd(PPh ) ], K CO , DME/H O
2
:1, 858C, 18 h.
ꢀ
1
Table 1. GPC data (polystyrene and poly(p-phenylene) as standards—eluent: THF; flow rate: 1.0 mLmin
T=308C) and molecular masses (determined by MALDI-TOF) of N-hexylphenothiazine oligomers.
;
zines to bend and to form sig-
moid and helical conformers. In
ꢀ
1
ꢀ1
Polystyrene standard [gmol
]
Poly(p-phenylene) standard [gmol
]
Molecular
comparison
with
molecule
ꢀ
1
mass [gmol
]
lengths estimated from the in-
tramolecular distances of the
unsubstituted terminal 3- and 7-
positions (Figure 3), in a linear
zigzag arrangement of the phe-
nothiazine cores the butterfly
M
n
M
w
M
p
M
n
M
w
M
p
1
1
1
1
1
2
3
4
5
6
676.6
1038.9
1392.7
1789.8
2261.1
703.3
1065.0
1430.6
1833.1
2390.5
740.8
1086.4
1467.3
1867.2
2296.6
685.3
996.0
1287.0
1602.2
1967.9
705.8
1015.1
1313.7
1631.7
2053.2
740.1
846.3
1127.7
1409.1
1690.6
1972.0
1034.2
1345.0
1660.3
1989.6
[16]
structure
of the phenothia-
zine units causes a pronounced
curvature and leads to consider-
ably reduced molecular dimen-
minimization of the linked and frozen phenothiazine units
with respect to their mutual dihedral torsion by application
of the MM2 force field, giving rise to the lowest-energy con-
formers in the gas phase (Figure 2).
These minimized structures not only explain the GPC re-
sults and the significant deviation from perfect rigid-rod be-
havior as expected for many conjugated oligomers, but also
explain an increasing tendency of higher oligophenothia-
sions (Table 2). Furthermore, an interphenothiazine dihedral
torsion of about 358 suggests that coplanarity and mutual
overlap of the p orbitals in the pristine states of oligo- and
polyphenothiazines should reduce the conjugation pathway
to a few units. Hence, the effective conjugation length
should be reached rather quickly and the most distinctive
electronic effects can be expected in the range of the lower
oligophenothiazines.
Chem. Eur. J. 2008, 14, 2602 – 2614
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2605

T. J. J. Müller et al.
fined as the difference between the energies of the absorp-
˜
ꢀ1
tion and emission maximum (Dd=6000–6500 cm ), togeth-
er with moderate to large quantum yields (F =10–77%).
f
These substantial Stokes shifts can be attributed to signifi-
cant geometrical changes occurring upon excitation from a
highly nonplanar ground state to a largely planarized excit-
[30]
ed state. The Stokes shifts decrease with the sizes of the
conjugated systems. Interestingly, for the series of dimer 11
to pentamer 14 the emission maxima correlate well with the
reciprocal chain lengths, and the effective conjugation
length is reached at 482 nm with six phenothiazine cores
and remains constant for the heptamer (Figure 5).
The electrochemical behavior of the oligophenothiazines
is most peculiar and clearly reveals a significant difference
between the lower oligomers 1 and 11–13 and the higher
oligomers 13–16 (Table 3). Interestingly, the first three rep-
resentatives of the homologous series display separated,
well resolved one-electron oxidation events corresponding
to the number of phenothiazine units (Figure 6). As a conse-
quence of intramolecular electronic coupling the first oxida-
tion affects the subsequent electron transfer, and delocaliza-
tion of the generated radical cations is apparently favored.
For tetramer 13 the fourfold separation of the anodic oxida-
tions can only be observed at low concentration. Upon a
dropwise tenfold increase of the concentration not only
does the appearance of the cyclic voltammogram change
from four reversible one-electron oxidations to broad oxida-
tion and reduction waves (Figure 7), but also, in multi-sweep
experiments, adsorption effects of electroactive specimen on
the electrode surface cause a steady growth in the current
intensity that can be attributed to electrocrystallization.
Similar behavior in multisweep experiments is found for
the higher oligomers 13–16, with which adsorption on the
electrode leads to a growth in the peak currents in the oxi-
dative and reductive regions (Figure 8). Hence, two oxida-
tion and two reduction waves can be identified (Table 3),
with the average of lower potentials (oxidation and reduc-
tion wave) seeming to represent the oxidation to the state of
a radical cation. Self-organization of radical cations in con-
densed phase has frequently been observed and can also be
regarded as an important intermolecular interaction for
model studies of a charge-transport phenomenon in posi-
Figure 1. Correlation and linear fit of the molecular mass (determined by
MALDI-TOF) and GPC M (poly(p-phenylene) as a standard) (M=
p
ꢀ
1
2
0
p
.90008 M +190.54245 [gmol ] (r =0.99979)).
Electronic properties: The electronic properties of the ho-
mologous series of oligophenothiazines 1 and 11–16 were in-
vestigated by absorption and emission spectroscopy and by
cyclic voltammetry (Table 3). In CH Cl solution the lon-
2
2
gest-wavelength absorption band—except in the case of 1
lmax,abs =312 nm)—is a distinct shoulder that shifts from
50 nm for the dimer 11 to 374 nm for the heptamer 16. Ac-
cording to TDDFT calculations on phenothiazine oligo-
(
3
[30]
mers
this band represents a HOMO–LUMO transition
with p–p* character. The longest-wavelength bands (in
wavenumbers) of all members of the series correlate reason-
ably well with the reciprocal numbers of phenothiazine units
ꢀ
1
2
(
lmax,abs =6227.6 1/n+25682 [cm ] (r =0.991)), from which
a maximal wavelength for a polymer with infinite chain
ꢀ
1
length of 25682 cm (389 nm) can be estimated. The extinc-
tion of the oligophenothiazines is plotted vs. the number of
phenothiazine units in a log–log plot in Figure 4. The extinc-
tion per phenothiazine unit increases superlinearly with the
length of the conjugated system as a consequence of the in-
crease in the oscillator strength with the length of the conju-
gated system [Eq. (1)]. A linear regression in the log–log
plot gives a slope of 1.46:
[34]
tively doped conducting polymers.
Furthermore, the first reversible oxidation potentials
a
0/+1
e ꢁ n with a ¼ 1:46
ð1Þ
ACHTREUNG
0
/+1
2
where e represents the extinction coefficient of an oligomer
with n phenothiazine units. According to the literature,
power laws with values for a of about 1.16 to 1.3 have been
ACHTREUNG
sorption tendency of the higher oligomers 13–16 at in-
creased concentrations also manifests in a linear correlation
with the reciprocal chain length (E
r =0.9916), but with a steeper slope, indicating that the po-
lymer would stack and be oxidizable at a potential 100 mV
lower than that of the free chain. The ease of oxidation with
increasing chain length concurrently favors self-organization
of the generated radical cations in the sense of stacking,
which, in turn, increases the charge transport through the
layer.
[11b,31,32]
0/+1
described.
Two effects are responsible for this super-
=726.05(1/n)+434.14;
A
H
R
U
G
2
linear increase. The number of phenothiazine units per mol-
ecule expands both the chromophore and the extinction per
unit.
Fluorescence spectroscopy reveals that, with exception of
the monomer 1, in which the fluorescence quantum yield is
below 1%, all members of the series 11–16 fluoresce with
blue to blue–green light and remarkable Stokes shifts, de-
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Chem. Eur. J. 2008, 14, 2602 – 2614

Monodisperse Oligophenothiazines
FULL PAPER
ylation. The molecular weight
at the peak maximum (M ), ob-
p
tained from GPC, and the
actual molecular weights of the
oligomer series, obtained by
mass spectrometry, correlate
very well and give a valuable
estimation for masses of related
higher polymers. The peculiar
deviation from the rigid rod be-
havior of the oligomers with re-
spect to the model and standard
poly(p-phenylene) and estimat-
ed molecular lengths can be in-
terpreted by a QM/MM confor-
mational analysis for the com-
plete series. The obvious inher-
ent butterfly-shaped conforma-
tion of the phenothiazine
structure multiplies and enhan-
ces helical and sigmoid oligo-
mer conformations, concomi-
tantly reducing the hydrody-
namic volume of the oligomers.
The electronic properties were
investigated by absorption and
emission
spectroscopy
and
cyclic voltammetry. Correla-
tions with chain length were
readily established, and for the
emission the effective conjuga-
tion length is already reached
in the hexamer. Moreover, it is
worth mentioning that oligo-
phenothiazines are both highly
fluorescent with high fluores-
cence quantum yields and elec-
troactive with low oxidation po-
tentials. Therefore, their use as
hole transporters and emitters
in molecular electronic devices
seems to be quite advantageous.
Further studies directed to-
wards polyphenothiazines, self-
organization on surfaces and in
porous materials, and tailor-
made oligophenothiazine-based
chromo-, fluoro-, and electro-
phores are currently underway.
Figure 2. Energy-optimized conformers (QM/MM approach with B3LYP/6-31+G(d,p) for the 10-ethyl-10H-
A
H
R
U
G
phenothiazine core and MM2 for minimizing the dihedral torsion) of the oligophenothiazines 11–16.
Experimental Section
Conclusion
General considerations: Reagents, catalysts, and solvents were purchased
In conclusion, we have developed a simple construction kit
approach to soluble, monodisperse, and structurally well de-
fined oligophenothiazines in good yields by use of Suzuki ar-
reagent grade and used without further purification. THF and 1,4-diox-
[
35]
ane were dried and distilled by standard procedures. Column chroma-
1
tography: silica gel 60, mesh 70–230. TLC: silica gel plates. H and
Chem. Eur. J. 2008, 14, 2602 – 2614
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2607

T. J. J. Müller et al.
+
0=þ1
tials were corrected to the internal standard of Fc/Fc in CH
4
2
Cl
2
(E
=
0
[
36]
50 mV).
Fluorescence spectra: Fluorescence measurements (Perkin–Elmer LS-55)
were performed in dry and degassed CH Cl at room temperature. To
2
2
avoid reabsorption and re-emission effects the concentrations were kept
strictly below 1 mm. The solutions were irradiated at approximately 10 nm
less in energy than the longest-wavelength absorption maximum or
shoulder. We estimated the quantum yields of our compounds by com-
parison with the known quantum yields of perylene (F
ethylamino-4-methylchromen-2-one, coumarine 1 (F =0.73).
ing to Eq. (2) the fluorescence emission (I) of standards R and samples S
at five different optical densities OD —that is, concentrations—were de-
termined and corrected for the refractive index (n) of the corresponding
f
=1.00) or 7-di-
[
33]
f
Accord-
Figure 3. Model for measuring molecular lengths.
i
I
i
solutions i. The presented quantum yields (Q) were obtained in each
Table 2. Estimated and computed molecular dimensions according to the
model in Figure 3.
case by averaging of five measurements, yielding a corresponding stan-
[
37]
dard deviation <0.1%.
Oligophenothiazine
Estimated molecular
length [Š]
Computed molecular
length [Š]
2
S
2
R
IS ODR
n
Q
S
¼ Q
R
ð2Þ
11
12
13
14
15
16
17.5
25.7
33.9
42.1
50.3
58.3
17.6
26.3
30.2
33.8
44.5
49.6
IR OD n
S
[38]
1
0-Hexyl-10H-phenothiazine (PT-hex) (1):
In an oven-dried Schlenk
flask (500 mL), 10H-phenothiazine (15.0 g, 75.3 mmol) and potassium
tert-butoxide (9.36 g, 83.4 mmol) were dissolved in dry THF (150 mL).
After the system had been stirred for 1 h, 1-bromohexane (24.8 g,
1
50 mmol) was added by syringe. The color of the reaction mixture
changed from brown to yellow, and
the solution was stirred at 668C for
h. After cooling to room tempera-
2 2
Table 3. UV/Vis, fluorescence, and oxidation potentials of oligophenothiazines (recorded in CH Cl , T=
3
2
98 K; bold values: absorption and emission maxima used for determining the Stokes shift).
ture, the crude product was filtrated
through a short plug of silica gel, and
the solvent was removed under re-
duced pressure. The residual brown oil
was chromatographed on silica gel
(hexane) to give 1 (21.0 g, 98%) as a
light yellow oil. H NMR (300 MHz,
6
[D ]acetone, 300 K): d=7.18 (ddd, J=
8.2, 7.3, 1.6 Hz, 2H), 7.15–7.11 (m,
2H), 7.00 (dd, J=8.2, 0.9 Hz, 2H),
6.92 (dt, J=7.4, 1.2 Hz, 2H), 3.92 (t,
J=6.9 Hz, 2H), 1.82–1.72 (m, 2H),
[
a]
[b]
[e]
1
Compound Absorption
l
max,abs [nm] (e)
D
HOMO–
Emission
Stokes
E
=
2
[mV]
[
d]
LUMO
l
max,em [nm] (F
f
/
shift Dn˜
ꢀ
1
[
eV]
%)
[cm ]
1
258 (30900), 312 (4900)
268 (47800), 282 (40000), 322
3.977
3.545
444 (ꢀ)
9600
6500
728
642, 788
[c]
1
1
2
3
454 (10)
1
(
18600), 350 (14300, sh)
268 (62900, sh), 279 (63500),
24 (26300), 364 (21400, sh)
286 (79700), 326 (33000), 366
sh, 30200)
[c]
1
1
3.409
3.407
471 (15)
6200
6300
606, 727, 861
3
[f]
476 (77)
479 (68)
589, 686, 789, 896
722 (514), 901
(
[
g,h]
(
773)
14
264 (94900), 284 (132300),
22 (57500, sh), 371 (43100,
sh)
3.360
6100
604 (545), 1079
1.49–1.39 (m, 2H), 1.31–1.25 (m, 4H),
[
g,h]
13
3
(828)
0.87–0.82 ppm (m, 3H);
(75 MHz, [D
C NMR
6
]acetone, 300 K): d=
1
1
5
6
282 (155500), 322 (74400),
3.343
3.334
482 (75)
482 (62)
6100
6000
587 (523), 1126
146.4 (Cquat), 128.3 (CH), 128.1 (CH),
125.7 (Cquat), 123.3 (CH), 116.7 (CH),
[
g,h]
3
73 (67600, sh)
284 (217800), 330 (88200, sh),
74 (83000, sh)
(861)
575 (505), 1111
47.8 (CH
27.2 (CH
(CH ); IR (neat): n˜ =3063, 2954, 2927,
2
), 32.2 (CH
2
), 27.6 (CH
2
),
[
g,h]
3
(868)
2
), 23.3 (CH
), 14.3 ppm
2
ꢀ7
3
[
(
[
a] Recorded in CH
=0.73)
2
2
Cl . [b] Recorded in CH
2
Cl
2
at c=10 m with 7-diethylamino-4-methylchromen-2-one
[
33]
ꢀ7
2855, 2580, 1923, 1885, 1770, 1679,
1594, 1571, 1485, 1457, 1443, 1369,
1333, 1285, 1250, 1238, 1195, 1140,
F
f
as a standard. [c] Recorded in CHCl
3
at c=10 m with perylene (F
f
=1.00) as a standard.
ꢀ
1
ꢀ5
d] D n˜ =lmax,absꢀlmax,em [cm ]. [e] Recorded in CH
2
Cl
2
. [f] Recorded at a concentration of 10 m. [g] Single
ꢀ
4
scan, recorded at a concentration of 10 m. [h] Oxidation waves; reduction waves in parentheses. Recorded at
ꢀ1
ꢀ
5
1127, 1105, 1039, 749, 728 cm ; UV/
Vis (CH Cl ): lmax (e)=312 nm (4900),
58 nm (30900 mol dm cm ); EI
MS (70 eV): m/z (%): 284 (21), 283
a concentration of 10 m.
2
2
ꢀ
1
3
ꢀ1
2
1
3
C NMR spectra: CD
The assignments of quaternary C, CH, CH
2
Cl
2
, CDCl
3
, and [D
6
]acetone (locked to Me
, and CH
4
Si).
+
+
+
[
M] (100), 212 [MꢀC
5
H
11
]
(67), 199 (16), 198 [MꢀC
6
H
13
]
(73); ele-
2
3
were made by use
mental analysis calcd (%) for C18
H
21NS (283.4): C 76.27, H 7.47, N 4.94,
of DEPT spectra. Elemental analyses were carried out in the Microana-
lytical Laboratories of the Organisch-Chemisches Institut, Ruprecht-
Karls-Universität, Heidelberg, Germany and in the Microanalytical Lab-
oratories of the Institut für Pharmazeutische Chemie, Heinrich-Heine-
Universität, Düsseldorf, Germany.
S 11.32; found: C 76.03, H 7.45, N 5.01, S 11.19.
[
39]
3
-Bromo-10-hexyl-10H-phenothiazine (2):
In an oven-dried Schlenk
flask (500 mL), potassium tert-butoxide (4.50 g, 40.0 mmol) was suspend-
ed in dry THF (150 mL) and the suspension was cooled to ꢀ788C (ace-
tone/dry ice bath). Then, 3-bromo-10H-phenothiazine (10.0 g,
Electrochemistry: Cyclic voltammetry experiments (EG & G potentio-
3
5.9 mmol) dissolved in dry THF (50 mL) was slowly added dropwise to
static instrumentation) were performed under argon in dry and degassed
the reaction mixture. After the system had been stirred at ꢀ788C for 2 h,
1-bromohexane (6.60 g, 40.0 mmol) was added. The cooling bath was re-
moved and the reaction mixture was stirred for 12 h at room tempera-
ture. The mixture was filtered through a short column of silica gel, and
the solvent was removed under reduced pressure. The residual brown oil
CH
2 2
Cl at room temperature and at scan rates of 100, 250, 500, and
ꢀ1
1
000 mVs . The electrolyte was Bu NPF (0.025m). The working elec-
4 6
trode was a 1 mm platinum disk, the counter electrode was a platinum
wire, and the reference electrode was a Ag/AgCl electrode. The poten-
2608
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 2602 – 2614

Monodisperse Oligophenothiazines
FULL PAPER
saturated aqueous solution of sodium sulfite (70 mL) and diethyl ether
(
100 mL) were added to the mixture and the system was stirred for 2 h.
The organic phase was separated, and the aqueous layer was extracted
several times with diethyl ether. The combined organic layers were dried
with magnesium sulfate, and the solvents were removed under reduced
pressure. The residue was chromatographed on silica gel (isohexane/ace-
tone 10:1) to give 3 (102.6 g, 90%) as a yellow oil, which crystallized
within a week. Compound 3 is sensitive towards light and oxygen, and
1
after exposure the color of 3 turns green. M.p. 588C; H NMR (300 MHz,
CDCl
3
, 300 K): d=7.27–7.21 (m, 4H), 6.68 (d, J=8.1 Hz, 2H), 3.75 (t,
J=7.0 Hz, 2H), 1.41 (m, 2H), 1.75 (m, 2H), 1.31–1.27 (m, 4H), 0.88 ppm
1
3
(
1
(
(
t, J=6.9 Hz, 3H); C NMR (75 MHz, CDCl
30.1 (CH), 129.7 (CH), 126.4 (Cquat), 116.6 (CH), 114.7 (Cquat), 47.6
CH ), 31.3 (CH ), 26.6 (CH ), 26.5 (CH ), 22.5 (CH ), 13.9 (CH ); MS
FAB ): m/z (%): 441 [M] (100), 356 [MꢀC (15).
0-Hexyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-10H-phenothia-
zine (4): Compound 2 (14.4 g, 41.2 mmol) was dissolved in dry THF
230 mL) under argon, and the solution was cooled to ꢀ788C (acetone/
dry ice bath). A solution of n-butyllithium in hexanes (2.5m, 25.0 mL,
1.8 mmol) was then slowly added to the reaction mixture, whereupon its
color turned brown. After the system had been stirred for 15 min at
788C, trimethyl borate (6.9 mL, 61.8 mmol) was added dropwise to the
3
, 300 K): d=144.1 (Cquat),
2
2
2
2
2
3
+
+
+
6
13
H ]
1
Figure 4. Correlation and linear fit of the extinction coefficient (e) and
(
2
phenothiazine units n (log10 e=1.4588 log10 n+3.6486 (r =0.9914)).
6
ꢀ
mixture, and stirring was continued for another 15 min. The solution was
then allowed to warm to room temperature, and stirring was continued
for 1 h. A solution of pinacol (7.41 g, 61.8 mmol; dried over 4 Š mol
sieves) in THF (50 mL) was added dropwise to the reaction mixture, and
the stirring was continued for 2 h. Acetic acid (2.4 mL, 41.2 mmol) was
then added, and the color changed to light orange and the solution
became viscous. After 14 h of stirring, a saturated solution of sodium sul-
fite (100 mL) was added and the mixture was extracted several times
with diethyl ether. The combined organic layers were dried with magnesi-
um sulfate and the solvents were removed under reduced pressure. The
residue was chromatographed on silica gel (isohexane/acetone 10:1) to
1
give 4 (7.71 g, 66%) as a yellow, viscous resin. H NMR (200 MHz,
CDCl
3
, 300 K): d=7.59 (m, 2H), 7.12 (m, 2H), 6.88 (m, 3H), 3.82 (t, J=
7
0
.2 Hz, 2H), 1.79 (m, J=7.1 Hz, 2H), 1.42 (m, 2H), 1.33 (m, 16H),
1
3
.87 ppm (t, J=6.6, 3H); C NMR (75 MHz, CDCl
quat), 144.4 (Cquat), 133.9 (CH), 133.6 (CH), 127.2 (CH), 126.7 (CH),
24.7 (Cquat), 123.8 (Cquat), 122.4 (CH), 115.4 (CH), 114.6 (CH), 83.5
quat), 47.4 (CH ), 31.2 (CH ), 26.6 (CH ), 26.3 (CH ), 24.6 (CH ), 22.3
CH ), 13.8 ppm (CH ); IR (KBr): n˜ =2976, 2956, 2928, 2857, 1600, 1576,
466, 1355, 1264, 1144, 1108, 964, 860, 748, 673 cm ; UV/Vis (CH
3
, 300 K): d=147.5
(
C
Figure 5. Correlation of the emission maxima lmax,em and phenothiazine
1
2
units n for 11–14 (solid line: lmax,em =3876 1/n+20042 (r =0.980); dotted
(
C
2
2
2
2
3
line: effective conjugation length at 482 nm).
(
1
2
3
ꢀ
1
2
Cl
2
ꢀ1
):
ꢀ
1
3
l
max (e)=318 nm (63200), 264 (380600), 244 nm (143200 mol dm cm );
was chromatographed on silica gel (hexane) to give 2 (12.0 g, 92%) as a
+
+
EI MS (70 eV): m/z (%): 409 [M] (100), 324 [MꢀC
tal analysis calcd (%) for C24 S (409.4): C 70.41, H 7.88, N 3.42,
S 7.83; found: C 70.64, H 7.81, N 3.56, S 7.86.
,7’-Dibromo-10,10’-dihexyl-10H,10’H-3,3’-biphenothiazine (6): In an
6 13
H ] (34); elemen-
1
light yellow oil. H NMR (300 MHz, [D
6
]acetone, 300 K): d=7.32 (dd,
H
23BNO
2
J=8.6, 2.3 Hz, 1H), 7.27 (d, J=2.3 Hz, 1H), 7.21 (ddd, J=8.2, 7.3,
1
1
1
.6 Hz, 1H), 7.14 (ddd, J=7.6, 1.6, 0.3 Hz, 1H), 7.03 (dd, J=8.2, 1.1 Hz,
7
H), 6.98–6.93 (m, 2H), 3.92 (t, J=6.9 Hz, 2H), 1.81–1.71 (m, 2H), 1.49–
1
3
oven-dried, three-necked flask (500 mL), 3 (10.0 g, 22.7 mmol) was dis-
solved in dry THF (250 mL) and cooled down to ꢀ788C. A solution of n-
butyllithium in hexanes (2.5m, 9.1 mL, 22.7 mmol) was then added drop-
wise to the reaction mixture over 5 min. The stirring was continued for
.39 (m, 2H), 1.31–1.25 (m, 4H), 0.86–0.82 ppm (m, 3H); C NMR
]acetone, 300 K): d=146.0 (Cquat), 145.8 (Cquat), 131.0 (CH),
30.1 (CH), 128.7 (CH), 128.2 (CH), 127.0 (Cquat), 124.8 (Cquat), 123.7
), 32.2 (CH ), 27.5
); IR (neat): n˜ =3060, 2954,
(
75 MHz, [D
6
1
(
(
2
CH), 118.2 (CH), 117.0 (CH), 114.8 (Cquat), 48.0 (CH
CH ), 27.2 (CH ), 23.3 (CH ), 14.3 ppm (CH
927, 2855, 1588, 1484, 1457, 1392, 1331, 1271, 1250, 806, 748 cm ; UV/
2
2
1
0 min, and copper cyanide (1.01 g, 11.3 mmol) was added in small por-
2
2
2
3
ꢀ1
tions. After the reaction mixture had been kept for another 10 min at low
temperature, TMEDA (10.1 mL, 68.0 mmol) was slowly added dropwise.
The stirring was continued for another 10 min, and synthetic air was
passed through the reaction mixture by syringe for 1 h. The color of the
solution turned from orange to black and the cooling was removed. After
the system had reached room temperature, a diluted aqueous solution of
sodium sulfite was added and the mixture was extracted several times
with diethyl ether. The combined organic layers were dried with magnesi-
um sulfate and the solvents were removed under reduced pressure. The
residue was chromatographed on silica gel (hexane/acetone 20:1) and re-
crystallized from hexane to give 6 (3.41 g, 47%) as yellow crystals. M.p.
ꢀ
1
3
ꢀ1
Vis (CH Cl ): lmax (e)=314 nm (5200), 262 (35100 mol dm cm ); EI
2 2
8
1
+
79
+
MS (70 eV): m/z (%): 363 [ BrꢀM] (100), 361 [ BrꢀM] (85), 292
8
8
1
1
+
+
79
+
[
[
BrꢀMꢀC
BrꢀMꢀC
5
H
H
11
]
]
(56),
290
[ BrꢀMꢀC
5
H
11
]
(49),
278
79
+
6
13
(77), 276 [ BrꢀMꢀC
6
H
13
]
(67), 260 (14), 258 (13),
+
1
97 [MꢀBrꢀC
6
H
13
]
(17), 196 (14); elemental analysis calcd (%) for
18
C H20BrNS (362.3): C 59.67, H 5.56, N 3.87, S 8.85, Br 22.05; found: C
5
9.41, H 5.60, N 3.85, S 9.06, Br 21.87.
3
,7-Dibromo-10-hexyl-10H-phenothiazine (3): In a two-necked flask with
a dropping funnel under a nitrogen atmosphere, compound 1 (73.4 g,
1
2
2
59 mmol) was dissolved in acetic acid (95.0 mL). Bromine (13.3 mL,
59 mmol) was added dropwise to the solution, whereupon it slightly
166–1758C; H NMR (300 MHz, [D ]acetone, 300 K): d=7.41 (dd, J=
6
8.5, 2.2 Hz, 2H), 7.34 (d, J=2.1 Hz, 2H), 7.31 (dd, J=8.4, 2.2 Hz, 2H),
7.26 (d, J=2.2 Hz, 2H), 7.01 (d, J=8.4 Hz, 2H), 6.92 (d, J=8.7 Hz, 2H),
3.89 (t, J=7.0 Hz, 4H), 1.76 (m, 2H), 1.43 (m, 4H), 1.27 (m, 8H),
warmed and its color turned dark red. After the system had been stirred
for 1 h at room temperature, another portion of bromine (13.3 mL,
1
3
2
59 mmol) was added to the reaction mixture and the color turned dark
0.84 ppm (brt, J=7.0 Hz, 6H); C NMR (75 MHz, [D ]acetone, 300 K):
6
green. The solution was stirred for 18 h at room temperature, and then a
d=145.4 (Cquat), 144.7 (Cquat), 135.1 (Cquat), 130.9 (CH), 130.0 (CH), 127.6
Chem. Eur. J. 2008, 14, 2602 – 2614
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2609

T. J. J. Müller et al.
ꢀ
5
ꢀ1
Figure 6. Cyclic voltammograms of 1 and 11–13 in CH
2
Cl
2
; T=293 K; c
0
=10 m; electrolyte: 0.05m NBu
4
=þ1
PF
6
(CH
2
Cl
2
); v=100 mVs ; Pt as a working
0
electrode, Ag/AgCl as a reference electrode, and Pt as a counter electrode (determined vs. ferrocene, E0 =+450 mV).
dissolved in a mixture of DME(20 mL) and water (10 mL) and the solu-
tion was degassed with argon for 20 min. After the addition of Pd(PPh
0.17 g, 0.15 mmol) the reaction mixture was stirred for 18 h at 858C.
A
C
H
T
R
E
U
N
G
3 4
)
(
After cooling down to room temperature, the solution was diluted with a
saturated aqueous solution of sodium sulfite and was stirred for 15 min.
The solution was diluted again with water (20 mL) and was extracted sev-
eral times with dichloromethane. The combined organic layers were
dried with magnesium sulfate and the solvents were removed under re-
duced pressure. The residue was chromatographed on silica gel (hexane/
1
acetone 15:1) to give 8 (1.91 g, 80%) as a yellow, glassy resin. H NMR
(
2
300 MHz, [D
H), 7.32–7.26 (m, 2H), 7.22–7.13 (m, 2H), 7.03–6.90 (m, 5H), 3.92 (t,
J=7.0 Hz, 2H), 3.89 (t, J=6.8 Hz, 2H), 1.83–1.71 (m, 4H), 1.45–1.43 (m,
6
]acetone, 300 K): d=7.44–7.39 (m, 2H), 7.35 (d, J=2.2 Hz,
1
3
4
H), 1.29–1.27 (m, 8H), 0.87–0.82 ppm (m, 6H); C NMR (75 MHz,
]acetone, 300 K): d=146.0 (Cquat), 145.4 (Cquat), 145.3 (Cquat), 144.7
quat), 135.3 (Cquat), 134.7 (Cquat), 130.9 (CH), 130.0 (CH), 128.3 (CH),
28.0 (CH), 127.6 (Cquat), 126.3 (CH), 126.1 (CH), 126.0 (Cquat), 125.6
CH), 125.0 (Cquat), 123.2 (CH), 118.0 (CH), 117.0 (CH), 116.7 (CH),
116.6 (CH), 114.7 (Cquat), 47.9 (CH ), 47.8 (CH ), 32.2(CH ), 32.1 (CH ),
27.5 (CH ), 27.4 (CH ), 27.1 (CH ), 27.1 (CH ), 23.2(CH ), 14.2 ppm
CH ); IR (KBr): n˜ =2952, 2925, 2853, 1600, 1575, 1457, 1250 cm ; UV/
Vis (CH
[
D
6
(
1
(
C
Figure 7. Multisweep experiment with tetramer 13 upon dropwise in-
ꢀ
5
ꢀ4
A
H
R
U
G
crease of concentration from 10 to 10 m (CH
lyte: 0.05m NBu PF (CH Cl
4 6 2 2
2
Cl
); v=250 mVs ; Pt as a working electrode,
Ag/AgCl as a reference electrode, and Pt as a counter electrode (deter-
2
; T=293 K; electro-
2
2
2
2
ꢀ
1
A
H
R
U
G
2
2
2
2
2
ꢀ
1
(
3
0
=þ1
Cl
): lmax (e)=362 (11800), 326 (16400), 284 (320000), 268 nm
mined vs. ferrocene, E0 =+450 mV).
2
2
ꢀ
1
3
ꢀ1
+
+
(
44000 mol dm cm ); MS (FAB ): m/z (%): 644 [M] (100), 599
+
+
[
MꢀC
6
H
H
13
]
(40), 474 [Mꢀ2C
6
H
13
]
(35); elemental analysis calcd (%)
(
C
quat), 126.4 (CH), 125.6 (Cquat), 125.3 (CH), 118.0 (CH), 116.8 (CH),
14.8 (Cquat), 48.0 (CH ), 32.1 (CH ), 27.4 (CH ), 27.1 (CH ), 23.3 (CH ),
4.3 ppm (CH ); IR (KBr): n˜ =2954, 2926, 2854, 1600, 1484, 1453, 1416,
393, 1331, 1295, 1267, 1251, 1193, 1145, 1107, 871, 807 cm ; UV/Vis
for C36
39BrN
2
S
2
(643.8): C 67.17, H 6.11, N 4.35, S 9.96, Br 12.41; found:
C 67.13, H 6.20, N 4.35, S 9.89, Br 12.23.
1
1
1
(
(
2
2
2
2
2
7-Bromo-7’-(7-bromo-10-hexyl-10H-phenothiazin-3-yl)-10,10’-dihexyl-
3
ꢀ1
1
0H,10’H-3,3’-biphenothiazine (9): 3-Iodo-7-bromo-10-hexyl-10H-pheno-
[24d]
ꢀ
1
3
ꢀ1
thiazine (5,
3.01 g, 6.2 mmol), 10-hexyl-3,7-bis(4,4,5,5-tetramethyl-
2 2
CH Cl ): lmax (e)=330 (2000), 270 nm (5100 mol dm cm ); MS
[
24a]
+
+
+
1,3,2-dioxaborolan-2-yl)-10H-phenothiazine (7,
Pd(PPh (0.13 g, 0.12 mmol), and potassium carbonate (2.32 g,
6.8 mmol) were dissolved in a degassed mixture of DME(85 mL) and
1.50 g, 2.8 mmol),
FAB ): m/z (%): 722 [M] (100), 638 (18) [MꢀC
6
H13] ; elemental anal-
[
A
H
R
U
G
3 4
) ]
ysis calcd (%) for C36
C 60.79, H 5.04, N 3.94.
-Bromo-10,10’-dihexyl-10H-10’H-[3,3’]biphenothiazine (8): Compound 4
2 2 2
H38Br N S
(722.7): C 59.83, H 5.30, N 3.88; found:
1
water (25 mL). The solution was stirred for 18 h at 958C. After cooling
down to room temperature, the mixture was diluted with water (100 mL)
and extracted with several portions of dichloromethane. The combined
organic layers were dried with magnesium sulfate and the solvents were
7
(
2
[
24d]
1.52 g, 3.71 mmol), 3-iodo-7-bromo-10-hexyl-10H-phenothiazine (5,
.19 g, 4.46 mmol), and potassium carbonate (1.54 g, 11.14 mmol) were
2610
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 2602 – 2614

Monodisperse Oligophenothiazines
FULL PAPER
0
/+1
ꢀ5
Figure 9. Correlation of E
(Nernst behavior for 1, 11–13 at c
0
ꢀ
=10 m;
4
averages of oxidation and reduction waves for 13–16 at c
phenothiazine units n for 11–14 (solid line for 1, 11–13, c
0
=10 m) and
ꢀ
5
0
=10 m:
0
/+1
2
ꢀ4
E
E
=184.06
A
H
R
U
G
0
=10 m:
0
/+1
2
A
H
R
U
G
UV/Vis (CH
2 2
Cl ): lmax (e)=364 nm (25100), 328 (29700), 282 (66200),
+ +
ꢀ1
3
ꢀ1
2
70 (70000 mol dm cm ); MS (FAB ): m/z (%): 1003 [M] (100), 918
+
(
14) [MꢀC
6 54 2 3 3
H13] ; elemental analysis calcd (%) for C H57Br N S
(
1004.1): C 64.60, H 5.72, N 4.18, S 9.58, Br 15.92; found: C 64.67, H
5
.77, N 4.21, S 9.32, Br 15.63.
1
3
0,10’-Dihexyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-10H,10’H-
,3’-biphenothiazine (10): Under argon atmosphere, 8 (2.00 g, 3.11 mmol)
was dissolved in dry THF (50 mL) and the solution was cooled down to
788C (acetone/dry ice bath). A solution of n-butyllithium in hexanes
1.6m, 2.33 mL, 3.73 mmol) was then slowly added dropwise to the reac-
ꢀ
(
tion mixture, whereupon the color turned brown. After the system had
been stirred for 10 min at ꢀ788C, trimethyl borate (0.42 mL, 3.73 mmol)
was added dropwise and the stirring was continued for another 15 min.
The solution was then allowed to come to room temperature and stirring
was continued for 2 h. Pinacol (0.44 g, 3.73 mmol) was added to the reac-
tion mixture and the stirring was continued for 1 h. Acetic acid (0.14 mL,
2
.49 mmol) was then added and the color changed to light orange and
the solution became viscous. After the system had been kept for 12 h at
room temperature, saturated aqueous solution of sodium sulfite
100 mL) was added and the crude product was extracted several times
a
(
with diethyl ether. The combined organic layers were dried with magnesi-
um sulfate and the solvents were removed under reduced pressure. The
residue was chromatographed on silica gel (hexane/acetone 15:1) to give
1
1
0 (1.19 g, 55%) as a light yellow, glassy resin. H NMR (300 MHz,
[
D
6
]acetone, 300 K): d=7.56 (dd, J=8.1, 1.5 Hz, 1H), 7.46 (d, J=1.2 Hz,
1
H), 7.44–7.40 (m, 2H), 7.37–7.32 (m, 2H), 7.22–7.13 (m, 2H), 7.05–7.00
Figure 8. Multisweep experiments with 14 (top, 7 cycles), 15 (center, 10
ꢀ
4
(m, 4H), 6.96–6.91 (m, 1H), 3.96 (t, J=7.4 Hz, 2H), 3.94 (t, J=6.9 Hz,
2H), 1.84–1.75 (m, 4H), 1.48–1.43 (m, 4H), 1.31–1.27 (m, 20H), 0.87–
cycles), and 16 (bottom, 10 cycles) (CH
2 2 0
Cl ; c =10 m; T=293 K; elec-
ꢀ
1
trolyte: 0.05m NBu PF (CH Cl ); v=250 mVs ; Pt as a working elec-
4
6
2
2
1
3
0
.83 ppm (m, 6H); C NMR (75 MHz, [D
(Cquat), 147.0 (Cquat), 146.3 (Cquat), 145.6 (Cquat), 136.3 (Cquat), 136.2 (CH),
35.8 (Cquat), 135.2 (CH), 129.3 (CH), 129.0 (CH), 127.1 (CH), 127.1
CH), 127.0 (Cquat), 126.8 (Cquat), 126.5 (CH), 126.5 (CH), 126.1 (Cquat),
25.1 (Cquat), 124.3 (CH), 118.0 (CH), 117.8, 117.6, 116.9, 48.9 (CH ), 48.9
6
]acetone, 300 K): d=149.6
trode, Ag/AgCl as a reference electrode, and Pt as a counter electrode
0
0
=þ1
(
determined vs. ferrocene, E
=+450 mV).
1
(
1
removed. The residue was chromatographed on silica gel (hexane/ace-
2
1
(CH ), 33.2 (CH ), 33.2 (CH ), 28.6 (CH ), 28.5 (CH ), 28.2 (CH ), 28.1
tone 15:1) to give 9 (1.82 g, 70%) as a yellow, glassy resin. H NMR
2
2
2
2
2
2
(
CH
2
), 26.2 (CH
2
), 24.3 (CH
2
), 15.3 ppm (CH
3
); IR (KBr): n˜ =2955, 2928,
(
(
(
6
300 MHz, [D
6
]acetone, 300 K): d=7.47–7.42 (m, 4H), 7.38 (m, 4H), 7.32
ꢀ
1
2
855, 1604, 1584, 1462, 1354, 1144, 1108, 862, 808, 747, 672 cm ; UV/Vis
dd, J=8.8, 2.6 Hz, 2H), 7.28 (d, J=2.2 Hz, 2H), 7.07–7.03 (m, 4H), 6.95
d, J=8.46 Hz, 2H), 3.99–3.91 (m, 6H), 1.84–1.76 (m, 6H), 1.48–1.43 (m,
(
CH
2
Cl
2
):
l
max
3
(e)=358 nm
(4700),
324
(7800),
+
278
ꢀ
1
ꢀ1
+
1
3
(16900 mol dm cm ); MS (FAB ): m/z (%): 690 [M] (100), 605 (17)
H), 1.31–1.27 (m, 12H), 0.88–0.84 ppm (m, 9H); C NMR (75 MHz,
]acetone, 300 K): d=145.5 (Cquat), 145.0 (Cquat), 144.7 (Cquat), 135.3
quat), 134.8 (Cquat), 130.9 (CH), 130.0 (CH), 127.7 (Cquat), 126.4 (CH),
26.2, 125.6 (CH), 125.6 (CH), 125.1 (Cquat), 118.1 (CH), 117.0 (CH),
16.8, 114.7 (Cquat), 47.9 (CH ), 32.3 (CH ), 32.2 (CH ), 27.5 (CH ), 27.4
), 27.2 (CH ), 27.1 (CH ), 23.3 (CH ), 14.3 (CH ), 14.2 ppm (CH );
IR (KBr): n˜ =2953, 2927, 2854, 1628, 1457, 1416, 1332, 1241, 806 cm
+
+
[
MꢀC
6
H
13] , 520 (8) [Mꢀ2C
6
H13] ; elemental analysis calcd (%) for
[
D
6
42 2 2 2
C H51BN O S (690.8): C 73.02, H 7.44, N 4.06, S 9.28; found: C 72.98, H
(
C
7
.50, N 4.15, S 9.22.
10,10’-Dihexyl-10H,10’H-3,3’-biphenothiazine (PT-hex)
4 (107 mg, 0.26 mmol), [Pd(PPh ] (8 mg, 7 mmol), and K
0.78 mmol) were dissolved in 1,4-dioxane (20 mL) and water (8 mL) in a
1
1
2
2
2
2
2
(11): Compound
CO (103 mg,
(
CH
2
2
2
2
3
3
ꢀ
A
H
R
U
G
3
)
4
2
3
1
;
Chem. Eur. J. 2008, 14, 2602 – 2614
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2611

T. J. J. Müller et al.
flask (50 mL). The solution was degassed with nitrogen for 10 min, and 2
95 mg, 0.26 mmol) was added. The solution was stirred at 908C for 2 d.
After cooling down to room temperature the reaction mixture was dilut-
ed with diethyl ether and water. The organic layer was dried with magne-
sium sulfate and the solvents were removed under reduced pressure. The
residue was chromatographed on silica gel (pentane/diethyl ether 4:1) to
A
T
E
U
G
7
(16): This compound was produced by GP1 from 10 and 9, and
(
after chromatography on silica gel (hexane/acetone 10:1 to dichlorome-
thane), 16 (160 mg, 81%) was isolated as a yellow, glassy resin. H NMR
(300 MHz, CD
6.91–6.86 (m, 16H), 3.86–3.80 (m, 14H), 1.84–1.73 (m, 14H), 1.50–1.38
(m, 14H), 1.33–1.27 (m, 28H), 0.89–0.83 ppm (m, 21H); C NMR
(75 MHz, CD Cl , 300 K): d=145.3 (Cquat), 144.4 (Cquat), 144.1 (Cquat),
134.2 (Cquat), 127.4 (CH), 125.3 (CH), 125.2 (CH), 125.0 (CH), 124.7
(Cquat), 124.4 (Cquat), 122.4 (CH), 115.7 (CH), 115.6 (CH), 115.5 (CH),
1
2 2
Cl , 300 K): d=7.33–7.28 (m, 24H), 7.18–7.09 (m, 4H),
1
3
give 11 (137 mg, 93%) as a light yellow oil, which slowly crystallized.
2
2
1
M.p. 117–1198C; H NMR (300 MHz, [D
6
]acetone, 300 K): d=7.44 (dd,
J=8.5, 2.2 Hz, 2H), 7.38 (d, J=1.8 Hz, 2H), 7.04 (m, 4H), 7.29–7.14 (m,
4
1
3
H), 6.94 (m, 2H), 3.96 (t, J=7.0 Hz, 4H), 1.81 (m, 4H), 1.45 (m, 4H),
47.7 (CH
22.7 (CH
2
), 47.6 (CH
), 14.0 ppm (CH
2
), 31.6 (CH
2 2 2 2
), 27.0 (CH ), 26.9 (CH ), 26.7 (CH ),
1
3
.30 (m, 8H), 0.86 ppm (m, 6H); C NMR (75 MHz, [D
6
]acetone,
2
3
); IR (KBr): n˜ =2953, 2926, 2868, 2854, 1605,
ꢀ1
00 K): d=146.1 (Cquat), 145.2 (Cquat), 134.9 (Cquat), 128.3 (CH), 128.0
1458, 1415, 1379, 1333, 1294, 1274, 1252, 1240, 1192, 873, 806, 746 cm
UV/Vis (CH Cl ): lmax (e)=374 nm (83000, sh), 330 (88200), 284 nm
;
(
CH), 126.1 (CH), 126.0 (Cquat), 125.5 (CH), 125.2 (Cquat), 123.3 (CH),
16.8 (CH), 116.6 (CH), 47.8 (CH ), 32.2 (CH ), 27.6 (CH ), 27.2 (CH ),
3.3 (CH ), 14.2 ppm (CH ); IR (KBr): n˜ =2954, 2927, 2853, 1600, 1575,
487, 1458, 1414, 1376, 1332, 1252, 1194, 1121, 1040, 887, 874, 808,
48 cm ; UV/Vis (CH
82 (40000), 268 (47800 mol dm cm ); EI MS (70 eV): m/z (%): 566
2
2
ꢀ
1
3
ꢀ1
+
(
217800 mol dm cm ); MS (MALDI): m/z (%): 1971 [M] (100),
1
2
1
7
2
2
2
2
2
+
+
1
605.0 (87) [MꢀC
6
H
13] , 1519.8 (29) [Mꢀ2C
6
H
13] , 1434.7 (12)
2
3
+
[
Mꢀ3C
6
H
13] ; elemental analysis calcd (%) for C126
H
135
N
7
S
7
(1972.0): C
ꢀ
1
76.75, H 6.90, N 4.97, S 11.38; found: C 76.67, H 6.88, N 4.89, S 11.20.
2 2
Cl ): lmax (e)=350 nm (14300, sh), 322 (18600),
ꢀ
1
3
ꢀ1
General procedure for the syntheses of even-numbered oligophenothia-
zines (PT-hex)2n
+
(
17), 565 (42), 564 [M] (100), 480 (10), 479 (23), 395 (13), 394 (35); ele-
ACHTREUNG
mental analysis calcd (%) for C36 (564.8): C 76.55, H 7.14, N 4.96,
H
40
N
2
S
2
ic acid ester 4 or 10 (2.2 equiv), [Pd
A
H
R
U
3 4
)
S 11.35; found: C 76.68, H 7.34, N 4.67, S 11.45.
carbonate (5.0 equiv) in a degassed DME/water (2:1) mixture was stirred
for 18 h at 858C. After the system had cooled to room temperature, a di-
luted sodium sulfite solution and water were added. The mixture was ex-
tracted with several portions of dichloromethane. The combined organic
layers were dried with magnesium sulfate and the solvents were removed.
The residue was chromatographed on silica gel to give the pure even-
numbered oligophenothiazines 13 or 15.
General procedure for the syntheses of odd-numbered oligophenothia-
zines (PT-hex)2n+1
pound 3 or 9 (1.0 equiv), phenothiazine boronic acid ester 4 or 10
2.2 equiv), [Pd(PPh ] (0.05 equiv), and potassium carbonate (5.0 equiv)
A
C
H
T
R
E
U
N
G
(GP1): A mixture of dibromo phenothiazine com-
(
A
C
H
T
R
E
U
N
G
3 4
)
in a degassed DME/water (2:1) mixture was stirred for 18 h at 858C.
After cooling down to room temperature, the mixture was diluted with a
diluted sodium sulfite solution and water. The mixture was extracted
with several portions of dichloromethane. The combined organic layers
were dried with magnesium sulfate and the solvents were removed. The
residue was chromatographed on silica gel to give the pure odd-num-
bered oligophenothiazines 12, 14, or 16.
A
H
R
U
G
4
(13): This compound was produced by GP2 from 4, and after
1
was isolated as a yellow, glassy resin. H NMR (300 MHz, CD
2
Cl
00 K): d=7.37–7.30 (m, 12H), 7.19–7.11 (m, 4H), 6.93–6.87 (m, 10H),
.85 (t, J=7.33 Hz, 8H), 1.87–1.75 (m, 8H), 1.50–1.39 (m, 8H), 1.35–1.28
2
,
3
3
1
3
(
2 2
m, 16H), 0.90–0.85 ppm (m, 12H); C NMR (75 MHz, CD Cl , 300 K):
A
C
H
T
R
E
U
N
G
(PT-hex)
3
(12): This compound was produced by GP1 from 3 and 4, and
d=145.5 (Cquat), 144.7 (Cquat), 134.4 (Cquat), 127.6 (CH), 125.5 (CH), 125.2
(CH), 125.0 (Cquat), 124.7 (Cquat), 122.7 (CH), 116.0 (CH), 115.9 (CH),
after chromatography on silica gel (hexane/acetone 20:1), 12 (354 mg,
1
8
4%) was isolated as a yellow resin. H NMR (CD
2 2
Cl , 300 MHz, 300 K):
1
1
1
15.8 (CH), 47.8 (CH
4.1 ppm (CH ); IR (KBr): n˜ =2953, 2926, 2868, 2854, 1604, 1457, 1415,
378, 1333, 1295, 1275, 1251, 1240, 1193, 873, 807, 747 cm ; UV/Vis
2 2 2 2 2
), 31.7 (CH ), 27.2 (CH ), 27.0 (CH ), 23.0 (CH ),
d=7.34–7.31 (m, 8H), 7.19–7.12 (m, 4H), 6.94–6.88 (m, 8H), 3.86 (m,
3
6
H), 1.80 (m, 6H), 1.45 (m, 6H), 1.32 (m, 12H), 0.89 ppm (m, 9H);
ꢀ
1
1
3
C NMR (CD
quat), 134.2 (Cquat), 134.1 (Cquat), 127.3 (CH), 125.2 (CH), 125.2 (CH),
24.9 (CH), 124.9 (CH), 124.7 (Cquat), 124.4 (Cquat), 122.4 (CH), 115.6
CH), 115.6 (CH), 115.5 (CH), 47.6 (CH ), 47.5 (CH ), 31.6 (CH ), 26.9
CH ), 26.7 (CH ), 22.7 (CH ), 13.8 ppm (CH ); IR (KBr): n˜ =2953, 2927,
854, 1602, 1576, 1458, 1415, 1378, 1332, 1240, 1193, 1138, 1106, 874, 808,
47 cm ; UV/Vis (CH Cl ): lmax (e)=364 nm (21400, sh), 324 (26300),
2 2
79 (63500), 268 (62900 mol dm cm , sh); EI-MS (70 eV): m/z (%):
48 (11), 847 (30), 846 (61), 845 [M] (100), 761 (11), 760 (15), 590 (16),
2 2
Cl , 75 MHz, 300 K): d=145.2 (Cquat), 144.3 (Cquat), 144.1
(
(
(
CH
2
Cl
2
):
l
max
3
(e)=366 nm
(30200, sh),
326
(33000),
286
(
1
(
(
2
7
2
8
4
7
C
ꢀ
1
ꢀ1
+
+
79700 mol dm cm ); MS (FAB ): m/z (%): 1126 [M] (100), 1042
48) [MꢀC
+
+
6
H13] , 787.0 (43) [Mꢀ4C
6
H13] ; elemental analysis calcd (%)
2
2
2
for C72
78 4 4
H N S (1127.7): C 76.69, H 6.97, N 4.97, S 11.37; found: C 76.39,
2
2
2
3
H 6.91, N 4.87, S 11.38.
(PT-hex) (15): This compound was produced by GP2 from 10, and after
chromatography on silica gel (hexane/acetone 15:1), 15 (229 mg, 80%)
ꢀ
1
A
H
R
U
G
6
ꢀ
1
3
ꢀ1
1
+
was isolated as a yellow, glassy resin. H NMR (300 MHz, CD
2
Cl
00 K): d=7.36–7.30 (m, 18H), 7.19–7.11 (m, 6H), 6.93–6.87 (m, 12H),
.89–3.82 (m, 12H), 1.86–1.77 (m, 12H), 1.50–1.40 (m, 12H), 1.36–1.29
2
,
3
3
(
22 (10); elemental analysis calcd (%) for C54
.03, N 4.96, S 11.36; found: C 76.55, H 7.33, N 4.79, S 10.78.
(14): This compound was produced by GP1 from 4 and 9, and
after chromatography on silica gel (hexane/acetone 15:1), 14 (400 mg,
59 3 3
H N S (846.3): C 76.64, H
1
3
m, 24H), 0.91–0.88 ppm (m, 18H); C NMR (75 MHz, CD
d=145.5 (Cquat), 144.7 (Cquat), 144.4 (Cquat), 134.5 (Cquat), 127.7 (CH),
25.6 (CH), 125.2 (CH), 125.0 (Cquat), 124.7 (Cquat), 122.7 (CH), 115.9
CH), 115.8 (CH), 47.9 (CH ), 31.9 (CH ), 27.2 (CH ), 27.0 (CH ), 23.0
); IR (KBr): n˜ =2954, 2925, 2868, 2854, 1604, 1457,
415, 1379, 1333, 1294, 1252, 1240, 1193, 873, 806, 746 cm ; UV/Vis
2 2
Cl , 300 K):
A
C
H
T
R
E
U
N
G
(PT-hex)
5
1
1
5
3
6
1
2 2
1%) was isolated as a yellow, glassy resin. H NMR (300 MHz, CD Cl ,
(
(
1
2
2
2
2
00 K): d=7.32–7.29 (m, 14H), 7.26–7.09 (m, 6H), 6.91–6.86 (m, 10H),
.71–6.68 (m, 2H), 3.85–3.75 (m, 10H), 1.86–1.73 (m, 20H), 1.53–1.41 (m,
CH
2
), 14.2 ppm (CH
3
ꢀ1
1
3
0H), 1.27 (m, 20H), 0.90–0.85 ppm (m, 15H, CH
Cl , 300 K): d=145.2 (Cquat), 144.5 (Cquat), 144.4 (Cquat), 144.2 (Cquat),
44.1 (Cquat), 143.9 (Cquat), 134.5 (Cquat), 134.2 (Cquat), 134.1 (Cquat), 134.0
3
); C NMR (75 MHz,
(
(
(
CH
2
Cl
2
):
l
max
ꢀ1
(e)=373 nm (67600, sh), 322 (74400), 282 nm
CD
1
2
2
3
ꢀ1
+
155500 mol dm cm ); MS (MALDI): m/z (%): 1689 [M] (100), 1605
90) [MꢀC
+
+
+
6
H
13] , 1520 (41) [Mꢀ2C
6
H
13] , 1435 (17) [Mꢀ3C
6
H
13] ; ele-
(
C
quat), 130.0 (CH), 129.5 (CH), 127.4 (CH), 125.4 (CH), 125.2 (CH),
mental analysis calcd (%) for C108
116 6 6
H N S (1690.6): C 76.73, H 6.92, N
1
24.9 (CH), 124.7 (Cquat), 124.5 (Cquat), 124.4 (Cquat), 122.4 (CH), 116.7
4
.97, S 11.38; found: C: 76.47, H 7.65, N 4.60, S 10.38.
(
(
(
1
1
3
CH), 115.8 (CH), 115.7 (CH), 115.6 (CH), 115.5 (CH), 114.3 (Cquat), 47.6
CH
CH
2
), 47.6 (CH
), 26.7 (CH
); IR (KBr): n˜ =2955, 2926, 2870, 2854, 1627, 1603, 1458,
2
), 31.6 (CH
2
), 31.5 (CH
2
), 29.2 (CH
2
), 26.9 (CH
2
), 26.8
2
2
), 26.6 (CH
2
), 22.7 (CH
2
), 22.7 (CH
2
), 13.9 (CH
3
),
3.9 ppm (CH
415, 1379, 1333, 1241, 873, 806, 746 cm ; UV/Vis (CH
71 nm (43100, sh), 322 (57500), 284 (132300),
3
Acknowledgements
ꢀ
1
2
Cl
2
): lmax (e)=
264
The support of this work by the Deutsche Forschungsgemeinschaft
(SFB 486, support for M.S.; Graduate College 850, stipend for A.W.F.)
and by the Fonds der Chemischen Industrie is gratefully acknowledged.
The authors also cordially thank Radu-Adrian Gropeanu, M.Sc., for ex-
perimental assistance, Dr. A. C. Grimsdale and Professor K. Müllen for
ꢀ
1
3
ꢀ1
+
+
(
(
94900 mol dm cm ); MS (FAB ): m/z (%): 1408 [M] (100), 1323.7
47) [MꢀC
+
+
6
H
13] , 983.3 (12) [Mꢀ2C
6
H13] ; elemental analysis calcd (%)
for C72
78 4 4
H N S (1409.1): C 76.71, H 6.94, N 4.97, S 11.38; found: C 76.61,
H 7.04, N 4.95, S 11.55.
2612
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 2602 – 2614

Monodisperse Oligophenothiazines
FULL PAPER
generous support with GPC analytics, helpful interpretation, and valuable
discussions, and BASF AG for the generous donation of chemicals.
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