Synthesis, physical properties, and chemistry of donor-acceptor-substituted pentacenes

Article abstract of DOI:10.1139/cjc-2016-0450

Pentacenes bearing electron-donating and (or) -withdrawing groups, namely methoxy-, dialkylamino-, and nitroaryl moieties, are synthesized to afford polarized pentacenes. The optical, electrochemical, and chemical properties of these derivatives are explo

Full text of DOI:10.1139/cjc-2016-0450

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Synthesis, physical properties, and chemistry of donor/acceptor substituted pentacenes
Dan Lehnherr,a Matthias Adam,b Adrian H. Murray,a Robert McDonald,c Frank Hampel,b and
Rik R. Tykwinski*a,b †
a Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
b
Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials
(ICMM), FriedrichꢀAlexanderꢀUniversität, ErlangenꢀNürnberg, Henkestr. 42, 91054 Erlangen,
Germany, Fax: +49ꢀ913ꢀ185ꢀ26865; Tel: +49ꢀ913ꢀ185ꢀ22540,Eꢀmail: rik.tykwinski@fau.de
c
Xꢀray Crystallography Lab, Department of Chemistry, University of Alberta, Edmonton,
Alberta, T6G 2G2, Canada
† Dedicated to Professor Reginald (Reg) Mitchell, with thanks for his support and collegiality
through the years – thanks Reg!
Abstract. Pentacenes bearing electron donating and/or withdrawing groups, namely methoxy,
dialkylaminoꢀ, and nitroaryl moieties, are synthesized to afford polarized pentacenes. The
optical, electrochemical, and chemical properties of these derivatives are explored. The
cycloaddition reaction of selective derivatives with tetracyanoethylene (TCNE) is explored, and
the experimental results are rationalized on the basis calculations using density functional theory
(DFT). Xꢀray crystallographic data provides insight molecular structure and intermolecular
interactions present in the solidꢀstate.
Keywords. pentacene • donorꢀacceptor • acene • polycyclic aromatic hydrocarbon • TCNE
cycloaddition • density functional theory
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Introduction. Structural variation is used to modify HOMO–LUMO energies, band gaps,
solidꢀstate packing, and numerous other structureꢀrelated properties in optoelectronic
chromophores.1,2,3,4 To this end, the stepwise assembly of pentacenes has afforded structures
with unusual and potentially useful structures.5,6,7,8 The functionalization of pentacene is
typically achieved via two general approaches, placement of desired groups at the proꢀcata
positions (particularly the 2,3,9,10ꢀpositions, blue spheres in Figure 1) or at the periꢀ
positions (particularly the 6,13ꢀpositions, red spheres in Figure 1). For example, proꢀcata
functionalization can be achieved with alkoxy, 9 alkyl,10 alkynyl,11 aryl,12 carboxyl,10a–b, 13
silyl,14 halo,15 and cyano16 groups. Functionalization of the 6,13ꢀpositions have been realized
with alkyl,17 silylethynyl,18 aryl,19 arylethynyl,20 thioalkyl,21 cyano,22 trifluoromethyl,23 and
Ptꢀacetylide 24 groups, commonly via a 6,13ꢀpentacenequinone precursor. The fusion of
quinone,25 imide,26 or arene27 moieties to pentacene or the incorporation of heteroatoms into
the chromophore can also be accomplished.28 These various substituents and substitution
patterns can affect a wide range of properties including HOMOꢀLUMO energies, optical
absorption/emission properties, solidꢀstate packing, charge transport characteristics, and
photostability.1,2,19b,29
Figure 1. Summary of common pentacene functionalization patterns: (a) Blue spheres
illustrate the 2,3,9,10ꢀpositions (proꢀcata positions) and (b) red spheres illustrate the 6,13ꢀ
positions (periꢀpositions).
The formation of pentacenes with unsymmetrical 6,13ꢀsubstitution can provide polarized
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30 , 31
pentacenes with weak donor and acceptor substituents (e.g., 1d,e Scheme 1).
Unfortunately, the synthetic protocol used in these cases, nucleophilic addition to pentacene
quinone, does not tolerate strong electronꢀdonating or ꢀwithdrawing groups such as the
aniline and nitrophenyl moieties.30, 32 This problem has now been solved through
derivatization of the protected precursors 2a and 2b via palladium catalyzed Sonogashira
crossꢀcoupling reactions with aryl iodides. It should be emphasized that intermediates 2a,b
and related structures provide powerful building blocks for a wide range of crossꢀ
coupling,7, 33 cycloaddition,34 and coordination35 reactions as recently demonstrated in the
synthesis of oligomeric pentacenes and inorganic complexes with functionalized pentacenes.
Scheme 1. Synthesis of 4a–e and 1a–c (this work) and structures of 1d,e (from ref. 30).
Synthesis of donor/acceptor pentacenes. The reaction of 2a,b7 with iodoaryl derivatives
3a–c afforded 4a–d. Aniline derivative 4a partially decomposed during chromatographic
purification on silica gel, leading to a low isolated yield. Dimethylaniline substituted 4b was
likewise unstable on silica gel, but could be isolated pure and in high yield via
recrystallization (see SI for details). Nitrobenzene derivative 4c was, on the other hand,
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stable to purification via column chromatography. SnIIꢀmediated reductive aromatization of
4a–c provided 1a–c (a shorter reaction time was used for the synthesis of 1c to minimize the
reduction of the nitro group).36
Scheme 2. Synthesis of donorꢀacceptor pentacene 6a and structure of diphenyl derivative 6b (see
SI for the synthesis of 6b).
A pushꢀpull pentacene was then targeted. This began with the conversion of 4d to 4e via
reaction with TBAF at low temperature to avoid products resulting from fluorodenitration
(Scheme 1).37 A Sonogashira reaction of 4e with 3a then installed the dialkylaniline group,
affording 5 (Scheme 2). Compound 5 was also unstable to purification on silica gel. Thus,
after aqueous workup, the crude product was aromatized without prior chromatographic
purification to provide donorꢀacceptor pentacene 6a, which could be isolated pure in 62%
yield via column chromatography and crystallization.
Characterization of donor/acceptor pentacenes. UV–vis spectroscopy in CH2Cl2 reveals
λ
max is moderately influenced by substitution changes in compounds 1a–e and 6a (Figures 2 and
3).38 Parent compound 1e (R = H) has λmax = 652 nm, and this absorption is redꢀshifted via
incorporation of increasingly electron donating groups to 655 nm (1d, R = OMe), 668 nm (1b, R
= NMe2), and 674 nm (1a, R = NnꢀHex2). Appending a nitroaryl group gives λmax = 666 nm for
1c, nearly equal to that of donor substituted 1b. The most strongly polarized pentacene derivative
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6a (density functional calculations predict a dipole moment of 13.7 Debye, see SI for details)
shows the lowest energy λmax at 689 nm, noticeably redꢀshifted versus the parent chromophore
6b20a,39
(λmax 660 nm) as well as derivatives 1a–d. The redꢀshift for 6a is most dramatic in the
solid state (see Figure S5), where the UV–vis spectrum of a thin film shows λmax = 823 nm,
shifted by 134 nm to lower energy than that in solution. Donor/acceptor pentacenes 1a–c and 6a
show no significant emission in CH2Cl2.
Figure 2. UVꢀvis absorption spectra of 1a–e in CH2Cl2; inset expansion of lowꢀenergy region of
UVꢀvis absorption spectra.
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Figure 3. UVꢀvis absorption spectra of 6a,b in CH2Cl2; inset expansion of lowꢀenergy region of
UVꢀvis absorption spectra.
Table 1. Optoelectronic, electrochemical, and thermal properties of pentacenes 1a–e and 6a,b.
*+/
' ꢀ/-*
̿
̿
"
Cmpd
Red
"
Eox1
Eox2
Ered1
Ered2
Ered3
λmax
λmax
/eV e
(CH2Cl2)
/eV d
Shift
/nm c
/V e
/V e
/V e
/V e
/V e
(CH2Cl2)(film)
/nm a
674
668
666
655
652
689
660
/nm b
685
683
718
668
671
823
11
15
52
13
19
134
1.66
1.68
1.72
1.78
1.81
1.49
1.78
1.63
1.66
1.77
1.80
1.83
1.52
0.16 f
0.18 f
0.44
0.35
0.39
0.18
0.33
0.41 f
0.43 f
–1.47
–1.48
–1.33
–1.45
–1.44
–1.34
–1.42
–1.94
–1.93 f
–1.46
–1.92
–1.90
–1.48
1a
1b
1c
1d
1e
6a
–2.09
0.39 f
–2.08 f
g
g
–
–
1.75
–1.84
6b
a
b
c
Lowest energy absorption maximum. Thin film drop cast from CH2Cl2. Redꢀshift for the
d
longest wavelength absorption λmax measured between the solid and solution states. As
determined from UV–vis spectroscopy, see reference 40. Cyclic voltammetry performed in
e
benzene/MeCN (3:1 v/v) with 0.1 M nꢀBu4NPF6 as supporting electrolyte at a scan rate of 150
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mV/s. Potentials are referenced to the ferrocene/ferrocenium (Fc/Fc+) couple used as an internal
standard.41 f Quasiꢀreversible event. g Data not measured.
Cyclic voltammetry (CV) has been used as a complementary method to UV–vis
spectroscopy to examine the electronic make up of donor/acceptor pentacenes (Table 1).41
The presence of the electronꢀdonating aniline groups significantly raises the energy of the
HOMO, as observed by lower oxidation potentials for 1a and 1b (Eox = 0.16 and 0.18 V,
respectively) relative to parent compound 1e (Eox = 0.39 V). Reduction of nitro derivative 1c,
on the other hand, is observed at a lower potential (–1.33 V) than 1e (Ered –1.44 V) and
correlating with a lower LUMO level. For donorꢀacceptor 6a, Eox1 = 0.18 V is nearly
identical to 1a and 1b, while Ered1 = –1.34 V is analogous to that of 1c, showing that the
aniline and nitro groups dictate the initial redox events of 6a.
Figure 4. Solidꢀstate packing of (a) pentacene 1b viewed down the short molecular axis, (b)
pentacene 1b viewed down the long molecular axis, and (c) pentacene 6a viewed down the long
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molecular axis showing three C–H•••
π interactions. Solvent molecules and hydrogen atoms
omitted in (a–b); carbon = gray, nitrogen = purple, oxygen = red, silicon = gold.
Trends for electrochemical HOMO–LUMO gap (
' ꢀ/-* ) are reasonably consistent with
̿
"
that calculated from the UV–vis data (̿
*+/) for 1a–e and 6a,b40 varying only by ±0.05 eV.
"
' ꢀ/-*
Comparing
̿
values, those of 1d–e are the highest 1.80–1.83 eV, while a slightly lower
"
' ꢀ/-*
value
̿
= 1.77 eV is found for nitro derivative 1c. Aniline derivatives 1a,b show a
"
electro
further lowering of Eg
(1.63 eV and 1.66 eV, respectively), and the greatest effect is
*+/
' ꢀ/-*
observed for donorꢀacceptor 6a with
̿
= 1.52 eV (
̿
of 1.49 eV), confirming the ability
"
"
to influence HOMO and LUMO levels through substitution.
Xꢀray crystallographic structures of compound 1b and 6a are shown in Figure 4. The
packing of 1b•0.5CH2Cl2 shows a 1ꢀD slipped ꢀstacking arrangement with about two
π
benzene rings worth of overlap and an interplanar distance between pentacene moieties of
3.40 Å.42 The solidꢀstate packing of 6a features centrosymmetric cofacial dimeric pairs with
interplanar distance between pentacenes of 3.46 Å.42 Although no longꢀrange cofacial
interactions 43 seem to guide the longꢀrange
πꢀ
stacking is present, a number of C–H•••
π
arrangement of 6a. The C–H bonds from the electron deficient nitroaryl moiety point into the
faces of the adjacent electron rich aniline rings, which are likely the cause of the nonꢀplanar
arrangement of the pendent aryl rings with respect to the pentacene framework. Furthermore,
the hexyl chains from the aniline group appear to engage in C–H•••π interactions with the
aromatic core of the pentacene, with distances that range from 2.82 to 3.20 Å (see Figure
S2). The nitroaryl group and the pentacene moiety show a 14.6° dihedral angle, while the
dihedral angle between the aniline and the pentacene moieties is –27.6° (in the opposite
direction).
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Reactions with TCNE. Oligoacenes are known to undergo cycloaddition chemistry with a
variety of cycloaddition partners including molecular oxygen, acetylene derivatives, arynes,
44
fullerenes, as well as dimerization processes via [4+4] and others.
The
cycloaddition/cycloreversion of tetracyanoethylene (TCNE) with electron rich alkynes is a
simple and mild reaction for the formation of optoelectronic materials with interesting
properties.45 With the intent to form pentacene derivatives with an even stronger acceptor group,
the reaction of TCNE with 1b was attempted toward the synthesis of 7b (Scheme 3).46 This
reaction resulted in a mixture of products, from which the isolation of 7b was unsuccessful. The
analogous reaction using 1d, on the other hand, gave the DielsꢀAlder adduct 8d, as confirmed by
Xꢀray crystallography (Figure 5).
Scheme 3. Structure of pentacenes 7b and 7d and the synthesis of adduct 8d.
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Figure 5. ORTEP representation of the Xꢀray crystallographic structure of 8d. Hydrogen atom
not shown, and nonꢀhydrogen atoms are represented by Gaussian ellipsoids at the 50%
probability level.
In order to gain insight into the reactivity of pentacene 1d with TCNE and the origin for the
preferential formation of the [4+2] product 7d over the [2+2]/retro[2+2] product 8d, we
utilized density functional theory (DFT) calculations (see Figure 6, and the Supporting
Information for results related to 1b). To reduce the computational cost, the triisopropylsilyl
group in 1d (and its related structures) was replaced with a trimethylsilyl group (e.g., 1d’).
Using B3LYP/6ꢀ31G(d), DFT calculations47 for both the [4+2] and [2+2] reactivity of 1d’
with TCNE were performed to explore: (a) whether the overall reactions to 7d’ and 8d’ are
exothermic, (b) which reaction pathway leads to the thermodynamically preferred product,
(c) whether there are any intermediates that are exceedingly high in energy to be reasonably
accessible, and (d) whether the relative energy of key transition state structures can provide
insight into the origin for the experimental preference for the [4+2] over the [2+2] pathway.
The [2+2]/retro[2+2] pathway associated with 1d’ and TCNE leads to two conformational
isomers of product 7d’, namely sꢀtransꢀ7d’ and sꢀcisꢀ7d’, each being exothermic relative to
starting materials 1d’ and TCNE by –32.0 and –31.3 kcal/mol, respectively. The formal
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[2+2]ꢀcycloaddition of TCNE with alkynes is known to proceed via stepwise mechanism48
and our DFT results are consistent with this (Figure 6). Relative to starting materials 1d’ and
TCNE, transition state TS9d is 31.4 kcal/mol higher in energy towards forming the first C–C
bond to reach intermediate 10d (+28.0 kcal/mol) in the stepwise formal [2+2], en route to the
exothermic cyclobutene intermediate 11d (–17.7 kcal/mol) and ultimately to products 7d’ via
a retro[2+2] process. While the formal [2+2]/retro[2+2] pathway leads to the thermodynamic
product, (s-trans-7d’), experimental results afford the [4+2]ꢀproduct 8d, implying a Curtinꢀ
Hammett scenario must be operational. Namely, that rate determining step leading to 7d’
along the [2+2]/retro[2+2] pathway places an energy barrier of higher energy compared to
the transition state leading to the [4+2] adduct (8d’). Indeed the electronic energy barrier for
the TCNEꢀacene [4+2]ꢀcycloaddition (TS12d via 13d) leading to product 8d’ is 17.8
kcal/mol lower in energy compared to the first carbonꢀcarbon bond forming transition state
(TS9d) in the stepwise TCNEꢀalkyne formal [2+2]ꢀcycloaddition. This is the origin of the
experimental preference to form product 8d over 7d. Analogous DFT analysis associated
with dimethylamino substituted pentacene 1b reveals a similar scenario, with preference for
[4+2] over [2+2] reactivity. Although, we were not able to locate the analogous transition
state TS9b, intermediate 10b is significantly higher in energy (+22.3 kcal/mol relative to
starting materials 1b’ and TCNE) than the [4+2] transition state (TS12b, +12.5 kcal/mol),
thus indicating that [2+2] reactivity is also disfavoured in the case of substrate 1b (see
Supporting Information for details).
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Figure 6. DFT calculated energy profile using B3LYP/6ꢀ31G(d) for reaction of TCNE with pentacene 1b illustrating the origin
of the preference for the [4+2] reactivity versus the formal [2+2]/retro[2+2] reactivity.
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Figure 7. DFT calculated energy profile using B3LYP/6ꢀ31G(d) for reaction of TCNE with pentacene 4b’ illustrating the origin
of the preference for the formal [2+2]/retro[2+2] pathway versus the [4+2] pathway.
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The sensitivity of the pentacene core to reactions with TCNE suggested the use of
dehydropentacene precursor 4b in place of pentacene 1b (Scheme 4) towards achieving [2+2]
reactivity with the alkyne instead of [4+2] reactivity with the pentacene to form product 14b’
instead of syn/anti-15, respectively. Examination of this hypothesis with DFT (structures 14–
22, Figure 7) supports the feasibility for TCNE to preferentially react with the alkyne in a
[2+2] manner instead of reacting with the acene in [4+2] fashion by using dehydropentacene
4b instead of pentacene 1b. Comparing the relevant transition states, the energy barrier
associated with the [4+2] pathway (anti-TS17) is 6.5 kcal/mol higher than the highest energy
barrier along the [2+2]/[4+2] pathway (TS20).
Experimentally, dehydropentacene 4b reacts cleanly with TCNE to provide an intensely
red coloured product. While mass spectral analysis was consistent with formation of the
1
expected product 14b, H and 13C NMR spectra of the product clearly shows two nonꢀ
equivalent naphthyl moieties.39 This suggested that either an alternative product had formed,
or that there is restricted or slow rotation on the NMR timescale with regard to the position
of the aniline group relative to the two naphthyl moieties. Indeed, the later premise is
supported by Xꢀray crystallography (Figure 8), which provided unambiguous proof of the
structure of the isolated product and shows the aniline group located above one of the
naphthyl moieties with contacts as short as 3.0–3.4 Å (carbons of aniline ring to plane of
naphthyl ring). Unfortunately, attempted conversion of 14b to 23b under typical
aromatization conditions using SnCl2•2H2O (with and without H2SO4), was not successful
and attempts with forcing conditions (reflux) resulted in decomposition.
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Scheme 4. Attempted synthesis of 23b from compound 14b.
Figure 8. ORTEP representation of the Xꢀray crystallographic structure of 14b. Hydrogen atom
not shown, and nonꢀhydrogen atoms are represented by Gaussian ellipsoids at the 50%
probability level.
In summary, we have developed synthetic methodology that allows for appending strong
electronꢀdonating and ꢀwithdrawing groups on the pentacene framework and extension of
this method to form a “pushꢀpull” pentacene. The presence of a donor and/or acceptor has a
significant effect on the electronic makeꢀup of the acenes demonstrated by UVꢀvis and cyclic
voltammetry analysis. This electronic influence also affects chemical reactivity, as
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demonstrated by reactions of 1d and 4b with TCNE. The origin of the difference in reactivity
towards TCNE with various pentacene derivatives is revealed using DFT calculations and
provides design principles towards controlling [4+2] over [2+2] reactivity. This study
contributes to paving the way to stronger donorꢀacceptor functionalized acenes for organic
electronic applications which may be of use for improved solar cell performance based on
singlet fission processes where charge transfer states are believed to play an important role.49
Experimental section
General experimental methods
Reagents were purchased in reagent grade from commercial suppliers and used without
further purification. Compounds 1d,e,30 2a,b, and 6b20a were synthesized via reported
procedures. THF and benzene were distilled from sodium/benzophenone ketyl. CH2Cl2 and
MeCN were distilled from CaH2. Anhydrous MgSO4 was used as the drying agent after aqueous
workꢀup. Evaporation and concentration in vacuo was done at waterꢀaspirator pressure. All
reactions were performed in standard, dry glassware under an inert atmosphere of nitrogen or
argon. Column chromatography: silica gelꢀ60 (230–400 mesh). Thin Layer Chromatography
(TLC): preꢀcoated plastic sheets covered with 0.20 mm silica gel with fluorescent indicator UV
254 nm; visualization by UV light or KMnO4 stain. Melting points are uncorrected. 1Hꢀ and 13Cꢀ
1
NMR spectra were collected at 27 °C in CDCl3; solvent peaks (7.24 ppm for H and 77.0 ppm
for 13C) as reference. Coupling constants are reported as observed (±0.5 Hz). UVꢀvis absorption
spectra were acquired at rt using a Varian Cary 400 Scan Spectrometer; λmax in nm (ε
in L•mol–
1•cm–1). Emission spectra were recorded using Photon Technology International (PTI) MP1
Fluorescence system. For mass spectral analyses, lowꢀresolution data are provided in cases when
M+ is not the base peak; otherwise, only highꢀresolution data are provided. The samples for ESI
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mass spectrometry were dissolved in ClCH2CH2Cl and made use of a 3:1 MeOH/toluene mixture
as the carrier solvent. MALDI mass spectrometry used the matrix transꢀ2ꢀ[3ꢀ(4ꢀtertꢀ
butylphenyl)ꢀ2ꢀmethylꢀ2ꢀpropenylidene]malononitrile (DCTB).
Differential scanning calorimetry (DSC) measurements were measured on a Perkin Elmer
Pyris 1 DSC instrument. Thermogravometric analyses (TGA) were carried out on a Perkin Elmer
Pyris 1 TGA instrument. All thermal analyses were carried out under a flow of nitrogen with a
heating rate of 10 °C/min. Thermal decomposition temperature as measured by TGA (as sample
weight loss) are reported as Td in which the temperature listed corresponds to the intersection of
the tangent lines of the baseline and the edge of the peak corresponding to the first significant
weight loss, typically >5%. Melting points from DSC analysis are reported as the peak maxima,
except in cases when the sample decomposed, in which case the onset temperature of the
decomposition exothermic peak is reported, as well as the exothermic maxima corresponding to
the decomposition.
Cyclic voltammetry experiments were done using a Bioanalytical Systems, Inc. (BASi)
Epsilon RotatingꢀDisk Electrode (Model RDEꢀ2). Data was analyzed by BASi EpsilonꢀEC Ver.
2.00.71–USB, BASi ComServer Ver. 1.03 on a PC computer. A threeꢀelectrode cell was used,
using a platinum disk working electrode and a platinum wire counter electrode. Silver/silver ion
(Ag in 0.1 M AgNO3, 0.1 M nꢀBu4NPF6 solution in MeCN) was used as a reference electrode.
Ferrocene/ferrocenium (Fc/Fc+) was used as an internal standard. The potential values (E) were
calculated using the following equation (except where otherwise noted): E = (Epc + Epa)/2, where
Epc and Epa correspond to the cathodic and anodic peak potentials, respectively. The potential
values obtained in reference to Ag/Ag+ were converted to potentials vs. ferrocene/ferrocenium
(Fc/Fc+). Solution cyclic voltammetry was performed in ca. 1 mM solution of pentacene
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derivatives in benzene/MeCN (3:1 v/v) containing 0.1 M nꢀBu4NPF6 as supporting electrolyte at
a scan rate of 150 mV•s–1, except where noted otherwise. All solutions were deoxygenated with
N2 before each experiment and a blanket of N2 was used over the solution during the experiment.
The working electrode was polished with 0.05 ꢀm alumina polish prior to each scan. Solutions of
pentacenes 1a–e and 6b were analyzed with a scanning window of 1.0 V to –2.0 V (vs Ag/Ag+),
while pentacene 6a was analyzed with a scanning window of 1.0 V to –2.2 V (vs Ag/Ag+).
Xꢀray data for 1b•0.5CH2Cl2 (CCDC 865682), 6a (CCDC 865683), 8d (CCDC 865684) and
14b (CCDC 865403) have been deposited at the Cambridge Crystallographic Data Centre
(CCDC), 12 Union Road, Cambridge CB21EZ, UK; fax: (+44)122ꢀ333ꢀ6033. These data can be
obtained free of charge from The Cambridge Crystallographic Data Centre via the Internet at
www.ccdc.cam.ac.uk/data_request/cif using the CCDC numbers given above.
X-ray crystallographic data
Data for 1b. Crystals suitable for Xꢀray crystallographic analysis were obtained from a solution
of 1b in CH2Cl2 which had been layered by acetone and allowed to slowly evaporate at 4 °C. Xꢀ
ray data for 1b•0.5CH2Cl2: C43H43ClNSi•0.5CH2Cl2, Mr = 644.34; crystal dimensions (mm) 0.39
× 0.19 × 0.08; monoclinic space group P21/c (No. 14); a = 9.2434(3) Å, b = 26.2155(8) Å, c =
14.8529(5) Å;
= 0.71073 Å; T = –100 °C; 2θmax = 52.82°; total data collected = 28699; R1 = 0.0423 [5794
β ρ
= 91.4551(4)°; V = 3598.0(2) Å3; Z = 4; calcd = 1.189 g cm–3; µ = 0.171 mm–1;
λ
2
2
observed reflections with Fo ≥ 2σ(Fo )]; wR2 = 0.1122 for 426 variables, 0 restraints, and 7395
unique reflections; residual electron density = 0.551 and –0.568 e Å–3. (CCDC 865682).
Data for 6a. Crystals suitable for Xꢀray crystallographic analysis were obtained from a solution
of 6a in CH2Cl2 which had been layered by acetone and allowed to slowly evaporate at 4 °C. Xꢀ
ray data for 6a: C50H46N2O2, Mr = 706.89; crystal dimensions (mm) 0.46 × 0.15 × 0.10; triclinic
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space group Pꢀ1 (No. 2); a = 11.3590(8) Å, b = 12.7835(8) Å, c = 14.8035(10) Å;
α =
74.2113(8)°,
β
= 72.9134(8)°,
γ
= 76.7681(8)°; V = 1951.1(2) Å3; Z = 2; calcd = 1.203 g cm–3; µ
ρ
= 0.073 mm–1;
λ
= 0.71073 Å; T = –100 °C; 2θmax = 51.56°; total data collected = 14731; R1 =
2
2
0.0444 [5021 observed reflections with Fo ≥ 2σ(Fo )]; wR2 = 0.1251 for 487 variables, 0
restraints, and 7477 unique reflections; residual electron density = 0.167 and –0.213 e Å–3.
(CCDC 865683).
Data for 8d. Crystals suitable for Xꢀray crystallographic analysis were obtained from a solution
of 8d in CHCl3 which was allowed to slowly evaporate at 4 °C. Xꢀray data for 8d: C48H40N4OSi,
Mr = 716.93; crystal dimensions (mm) 0.40 × 0.11 × 0.07; monoclinic space group P21/c (No.
14); a = 15.9034(13) Å, b = 12.3331(10) Å, c = 20.8200(18) Å;
β = 103.3580(13)°; V =
3973.1(6) Å3; Z = 4; calcd = 1.199 g cm–3; µ = 0.100 mm–1; λ = 0.71073 Å; T = –100 °C; 2θmax
ρ
=
2
2
51.46°; total data collected = 29103; R1 = 0.0467 [4791 observed reflections with Fo ≥ 2σ(Fo )];
wR2 = 0.1118 for 487 variables, 0 restraints, and 7580 unique reflections; residual electron
density = 0.207 and –0.305 e Å–3. (CCDC 865684).
Data for 14b. Crystals suitable for Xꢀray crystallographic analysis were obtained from a solution
of 14b in hexanes/CH2Cl2 (3:1) which was allowed to slowly evaporate at 4 °C. Xꢀray data for
14b: C51H49N5O2Si, Mr = 792.04; crystal dimensions (mm) 0.42 × 0.222 × 0.11; triclinic space
group Pꢀ1 (No. 2); a = 11.8561(6) Å, b = 15.0323(10) Å, c = 15.1075(10) Å, α = 115.327(7)°, β
= 91.628(5)°, γ = 103.478(5)°, V = 2341.4(3); Z = 2;
ρ
calcd = 1.123 g cm–3; µ = 0.774 mm–1; T =
174(3) K; 2
θmax = 147.08°; total data collected = 16660; R1 = 0.0607 [9138 observed reflections
2
2
with Fo ≥ 2
σ
(Fo )]; wR2 = 0.1873 for 566 variables, 9138 unique reflections, and 11 restraints;
residual electron density = 0.59 and –0.44 e Å–3. (CCDC 865403). Three disordered triisopropyl
19

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groups were refined with the following occupancies: C4–C5, 30:70; C7–C8, 59:41; C10–C11,
51:49. In addition, a residual electron density pattern indicated a strongly disordered solvent
molecule, likely CH2Cl2. All attempts to model and resolve this solvent molecule and the related
disorder failed. Therefore finally the “solvent mask” option of OLEX2 was used to mask this
region for refinement.50
Compound 1a: To a solution of 4a (0.104 g, 0.129 mmol) in dry THF (10 mL) that had been
deoxygenated by bubbling argon for 5 min was added SnCl2·2H2O (0.101 g, 0.448 mmol). The
solution was stirred at rt for 5 h, poured onto a pad of silica gel, eluted with 1:1 CH2Cl2/hexanes,
and the solvent was removed in vacuo. Column chromatography (silica gel, 3:2 CH2Cl2/hexanes)
afforded 1a (0.080 g, 84%) as a deep blue solid. Rf = 0.67 (3:2 CH2Cl2/hexanes). UVꢀvis
(CH2Cl2) λmax (ε): 274 (sh, 21 300), 315 (181 000), 336 (sh, 21 700), 394 (11 000), 440 (2 660),
495 (3 580), 626 (sh, 12 200), 674 (18 400) nm. No significant emission in CH2Cl2. IR (CDCl3
microscope): 3048 (w), 2955 (s), 2924 (s), 2863 (s), 2169 (s), 2120 (m), 1604 (s), 1526 (s) cm–1.
1H NMR (500 MHz, CDCl3): δ 9.26 (broad s, 4H), 8.08–7.98 (m, 2H), 7.98–7.89 (m, 2H), 7.73
(d, J = 8.7 Hz, 2H), 7.44–7.32 (m, 4H), 6.72 (d, J = 8.8 Hz, 2H), 3.34 (t, J = 7.5 Hz, 4H), 1.70–
13
1.58 (m, 4H), 1.44–1.20 (m, 33H), 0.98–0.89 (m, 6H). C NMR (100 MHz, CDCl3): δ 148.4,
133.2, 132.2, 131.9, 130.8, 129.8, 128.7, 128.6, 126.3, 126.2, 125.8, 125.6, 119.7, 116.5, 111.4,
109.0, 107.2, 106.2, 105.1, 86.4, 51.1, 31.7, 27.3, 26.8, 22.7, 19.0, 14.1, 11.7. ESI HRMS m/z
calcd. for C53H64NSi ([M + H]+) 742.4803, found 742.4787. TGA: Td ≈ 410 °C. DSC:
decomposition, 177 °C (onset), 181 °C (peak).
Compound 1b: To a solution of 4b (0.121 g, 0.182 mmol) in dry THF (10 mL) that had been
deoxygenated by bubbling argon for 5 min was added SnCl2·2H2O (0.204 g, 0.904 mmol). The
solution was stirred at rt for 5 h, poured onto a pad of silica gel, eluted with 2:1 CH2Cl2/hexanes,
20

Page 21 of 35
and the solvent was removed in vacuo. Column chromatography (silica gel, 2:1 CH2Cl2/hexanes)
afforded 1b (0.097 g, 89%) as a deep blue solid. Rf = 0.80 (2:1 CH2Cl2/hexanes). UVꢀvis
(CH2Cl2) λmax (ε): 275 (sh, 30 900), 314 (272 000), 389 (16 200), 440 (4 640), 481 (4 550), 619
(16 100), 668 (25 200) nm. No significant emission in CH2Cl2. IR (CH2Cl2 cast film): 3046 (w),
2941 (m), 2890 (w), 2863 (m), 2170 (m), 2120 (w), 1606 (s), 1525 (m), 1362 (m) cm–1. 1H NMR
(500 MHz, CDCl3): δ 9.25 (s, 2H), 9.24 (s, 2H), 8.04–7.98 (m, 4H), 7.74 (d, J = 8.6 Hz, 2H),
13
7.42–7.35 (m, 4H), 6.76 (d, J = 8.7 Hz, 2H), 3.03 (s, 6H), 1.45–1.34 (m, 21H). C NMR (125
MHz, CDCl3): δ 150.4, 133.0, 132.2, 131.9, 130.8, 129.8, 128.7, 128.6, 126.3, 126.2, 125.8,
125.6, 119.5, 116.7, 111.9, 110.3, 106.8, 106.2, 105.1, 86.6, 40.2, 19.0, 11.7. 13C NMR (APT,
125 MHz, CDCl3): δ 150.4 (C), 133.0 (CH), 132.2 (C), 131.9 (C), 130.8 (C), 129.8 (C), 128.7
(CH), 128.6 (CH), 126.3 (CH), 126.2 (CH), 125.8 (CH), 125.6 (CH), 119.5 (C), 116.7 (C), 111.9
(CH), 110.3 (C), 106.8 (C), 106.2 (C), 105.1 (C), 86.6 (C), 40.2 (CH3), 19.0 (CH3), 11.7 (CH).
ESI HRMS m/z calcd. for C43H44NSi ([M + H]+) 602.3238, found 602.3221. TGA: Td ≈ 430 °C.
DSC: decomposition, 162 °C (onset), 164 °C (peak).
Compound 1c: To a solution of 4c (0.105 g, 0.157 mmol) in dry THF (7 mL) that had been
deoxygenated by bubbling N2 for 5 min was added a solution of SnCl2·2H2O (0.082 g, 0.36
mmol) in THF (7 mL). The solution was stirred at rt for 3 h, poured onto a pad of silica gel,
eluted with 1:1 hexanes/CH2Cl2, and the solvent was removed in vacuo. Column
chromatography (silica gel, 1:1 hexanes/CH2Cl2) afforded 1c (0.053 g, 56%) as a green solid. Rf
= 0.50 (1:1 hexanes/CH2Cl2). UVꢀvis (CH2Cl2) λmax (ε): 274 (29 700), 313 (255 000), 347 (14
600), 395 (14 600), 441 (7 090), 616 (14 400), 666 (22 900) nm. No significant emission in
CH2Cl2. IR (CHCl3, cast) 3048 (w), 2942 (m), 2890 (w), 2864 (m), 2185 (w), 2124 (w), 1589
21

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(m), 1513 (m), 1337 (s) cm–1. 1H NMR (500 MHz, CDCl3): δ 8.94 (s, 2H), 8.54 (s, 2H), 8.09 (d,
J = 8.4 Hz, 2H), 7.75 (d, J = 8.5 Hz, 2H), 7.62 (d, J = 8.5 Hz, 2H), 7.46 (d, J = 8.3 Hz, 2H), 7.32
(t, J = 7.2 Hz, 2H), 7.26 (t, J = 7.2 Hz, 2H), 1.46–1.36 (m, 21H). gCOSY NMR (500 MHz,
CDCl3): δ 8.94 ↔ 7.75; 8.54 ↔ 7.62; 8.09 ↔ 7.46; 7.75 ↔ 8.94, 7.32; 7.62 ↔ 8.54, 7.26; 7.46
↔ 8.09; 7.32 ↔ 7.75; 7.26 ↔ 7.62. 13C NMR (125 MHz, CDCl3): δ 146.6, 132.1, 131.9, 131.7,
130.1, 130.0, 129.8, 128.5, 128.3, 126.4, 126.1, 125.9, 125.0, 123.5, 119.6, 115.9, 107.8, 104.6,
13
101.9, 92.9, 19.0, 11.7. C NMR (APT, 125 MHz, CDCl3): δ 146.6 (C), 132.1 (C), 131.9 (C),
131.7 (CH), 130.1 (C), 130.0 (C), 129.8 (C), 128.5 (CH), 128.3 (CH), 126.4 (CH), 126.1 (CH),
125.9 (CH), 125.0 (CH), 123.5 (CH), 119.6 (C), 115.9 (C), 107.8 (C), 104.6 (C), 101.9 (C), 92.9
(C), 19.0 (CH3), 11.7 (CH). MALDI HRMS m/z calcd. for C41H37NO2Si (M+) 603.2588, found
603.2590. TGA: Td ≈ 330 °C. DSC: decomposition, 197 °C (onset), 225 °C (peak).
Compound 3a: To a solution of BnEt3NICl251 (2.81 g, 7.203 mmol) in CHCl3 (30 mL) and
MeOH (15 mL) was added N,Nꢀdihexylaniline (2.00 g, 7.65 mmol) and CaCO3 (2.41 g, 24.1
mmol). The flask was wrapped in aluminum foil to protect from light and the reaction mixture
was stirred for 48 h at rt. The solution was filtered through a pad of Celite® with CH2Cl2 and the
solvent was removed in vacuo. Column chromatography (silica gel, 10:1 hexanes/CH2Cl2)
afforded 3a (2.51 g, 90%) as a clear yellow liquid. Rf = 0.43 (10:1 CH2Cl2/hexanes). IR (CH2Cl2
cast film): 3086 (w), 2955 (s), 2928 (s), 2857 (m), 1589 (s), 1499 (s) cm–1. 1H NMR (400 MHz,
CDCl3): δ 7.44 (d, J = 8.6 Hz, 2H), 6.44 (d, J = 8.9 Hz, 2H), 3.24 (t, J = 7.7 Hz, 4H), 1.58
(quintet, J = 6.7 Hz, 4H), 1.42–1.28 (m, 12H), 0.99–0.89 (m, 6H). 13C NMR (100 MHz, CDCl3):
δ 147.5, 137.5, 113.9, 75.3, 50.9, 31.7, 27.0, 26.7, 22.6, 14.0. 13C NMR (APT, 100 MHz,
CDCl3): δ 147.5 (C), 137.5 (CH), 113.9 (CH), 75.3 (C), 50.9 (CH2), 31.7 (CH2), 27.0 (CH2), 26.7
22

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(CH2), 22.6 (CH2), 14.0 (CH3). EI MS m/z 387.1 (M+, 56), 316.1 ([M – C5H11]+, 100). EI HRMS
m/z calcd. for C18H30IN (M+) 387.1423, found 387.1422.
Compound 3b.52 4ꢀIodoꢀN,Nꢀdimethylaniline was synthesized analogously to 3a (vide supra).
Spectroscopic data of 3b was in agreement with that reported.52b,d
Compound 4a: To a solution of 2a (0.288 g, 0.527 mmol) and 3a (0.331 g, 0.855 mmol) in THF
(7 mL) and diisopropylamine (5.0 mL, 3.6 g, 35 mmol) which had been deoxygenated with
argon for 10 min was added Pd(PPh3)4 (0.030 g, 0.026 mmol) and CuCl (0.005 g, 0.05 mmol)
and the solution was further deoxygenated for 5 min. The solution was stirred for 20 h at 45–55
°C before being poured into satd. aq. NH4Cl (200 mL). H2O (100 mL) was added and the
mixture was extracted with CH2Cl2 (80 mL, 50 mL). The organic phase was washed with 5% aq.
NH4Cl (200 mL), dried (MgSO4), filtered, and the solvent removed in vacuo. Column
chromatography (silica gel, 5:4 CH2Cl2/hexanes, column wrapped in aluminum foil to exclude
light) afforded 4a (0.119 g, 28%) as a brown oil. Rf = 0.38 (5:4 CH2Cl2/hexanes). IR (CH2Cl2
cast film): 3054 (w), 2931 (s), 2220 (m), 2169 (vw), 1607 (s), 1519 (s) 1081 (m), 1062 (m) cm–1.
1H NMR (500 MHz, CDCl3): δ 8.71 (s, 2H), 8.54 (s, 2H), 8.02–7.97 (m, 2H), 7.97–7.92 (m, 2H),
7.59–7.51 (m, 4H), 7.23 (d, J = 9.0 Hz, 2H), 6.46 (d, J = 9.1 Hz, 2H), 3.21 (t, J = 7.7 Hz, 4H),
3.11 (s, 3H), 3.07 (s, 3H), 1.57–1.47 (m, 4H), 1.34–1.25 (m, 12H), 1.25–1.19 (m, 21H), 0.91–
13
0.86 (m, 6H). C NMR (125 MHz, CDCl3): δ 147.8, 134.8, 133.5, 133.4, 132.9, 132.8, 128.2,
128.0, 126.9, 126.6, 126.4, 110.9, 108.3, 106.3, 90.8, 88.6, 88.1, 75.7, 74.1, 52.1, 51.9, 50.9,
13
31.6, 27.1, 26.7, 22.6, 18.7, 14.0, 11.4 (one signal coincident or not observed). C NMR (APT,
125 MHz, CDCl3): δ 147.8 (C), 134.8 (C), 133.5 (C), 133.4 (CH), 132.9 (C), 132.8 (CH), 128.2
(CH), 128.0 (CH), 126.9 (CH), 126.6 (CH), 126.4 (CH), 110.9 (CH), 108.3 (C), 106.3 (C), 90.8
(C), 88.6 (C), 88.1 (C), 75.7 (C), 74.1 (C), 52.1 (CH3), 51.9 (CH3), 50.9 (CH2), 31.6 (CH2), 27.1
23

Page 24 of 35
(CH2), 26.7 (CH2), 22.6 (CH2), 18.7 (CH3), 14.0 (CH3), 11.4 (CH) (one signal coincident or not
observed). ESI MS m/z 804.5 ([M + H]+, 100), 772.5 ([M – OMe]+, 66). ESI HRMS m/z calcd.
for C55H70NO2Si ([M + H]+) 804.5170, found 804.5155.
Compound 4b: To a solution of 2a (0.285 g, 0.524 mmol) and 3b (0.152 g, 0.614 mmol) in THF
(5 mL) and diisopropylamine (3 mL, 2 g, 0.2 mmol) which had been deoxygenated with argon
for 10 min was added Pd(PPh3)4 (0.030 g, 0.026 mmol) and CuCl (0.005 g, 0.05 mmol) and the
solution was further deoxygenated for 5 min. The solution was stirred for 20 h at rt before being
poured into satd. aq. NH4Cl (150 mL). H2O (50 mL) was added and the mixture was extracted
with CH2Cl2 (80 mL, 50 mL). The organic phase was washed with 5% aq. NH4Cl (150 mL),
satd. aq. NaCl (150 mL), dried (MgSO4), filtered, and the solvent removed in vacuo. The residue
was dissolved in a small amount of EtOAc (ca. 1 mL) to which MeOH (ca. 30 mL) was added.
The solution was cooled to –78 °C, filtered, and the solid was washed with MeOH (3 × 5 mL) to
afford 4b (0.254 g, 73%) as a white solid that is unstable to silica gel. IR (microscope): 3052 (w),
2942 (s), 2891 (m), 2864 (s), 2829 (w), 2816 (w), 2223 (m), 2164 (vw), 1609 (s) cm–1. 1H NMR
(500 MHz, CDCl3): δ 8.70 (s, 2H), 8.50 (s, 2H), 8.00–7.95 (m, 2H), 7.94–7.88 (m, 2H), 7.56–
7.49 (m, 4H), 7.22 (d, J = 9.1 Hz, 2H), 6.50 (d, J = 9.1 Hz, 2H), 3.09 (s, 3H), 3.04 (s, 3H), 2.89
13
(s, 6H), 1.27–1.17 (m, 21H). C NMR (125 MHz, CDCl3): δ 150.9, 134.7, 133.5, 133.3, 132.8,
128.21, 128.16, 128.1, 126.9, 126.7, 126.5, 111.5, 109.8, 106.0, 91.3, 89.1, 87.6, 75.9, 73.9, 52.1,
51.9, 40.1, 18.8, 11.4 (one signal coincident or not observed). ESI MS m/z 686.3 ([M + Na]+, 3),
664.4 ([M + H]+, 2), 632.3 ([M – OMe]+, 100). ESI HRMS m/z calcd. for C45H49NO2SiNa ([M +
Na]+) 686.3425, found 686.3416.
Compound 4c: To a solution of 2a (0.410 g, 0.753 mmol) and 3c (0.171 g, 0.687 mmol) in THF
(6 mL) and diisopropylamine (3 mL, 2 g, 0.2 mmol) which had been degassed for 10 min with
24

Page 25 of 35
argon was added Pd(PPh3)4 (0.039 g, 0.34 mmol) and CuCl (0.011 g, 0.11 mmol). The reaction
mixture was further deoxygenated with argon for an additional 2 min. The solution was stirred
for 20 h at rt before being poured into satd. aq. NH4Cl (150 mL). H2O (50 mL) was added and
the mixture was extracted with CH2Cl2 (80 mL, 50 mL). The organic phase was washed with 5%
aq. NH4Cl (150 mL), satd. aq. NaCl (150 mL), dried (MgSO4), filtered, and the solvent removed
in vacuo. Column chromatography (silica gel, CH2Cl2) afforded 4c (0.412 g, 90%) as an off
white foamy solid. Rf = 0.73 (CH2Cl2), 0.67 (2:1 hexanes/EtOAc), 0.24 (9:1 hexanes/EtOAc). IR
(CH2Cl2 cast film): 3056 (w), 2943 (m), 2892 (w), 2865 (m), 2230 (vw), 2170 (vw), 1594 (m),
1
1520 (s), 1344 (s) cm–1. H NMR (500 MHz, CDCl3): δ 8.78 (s, 2H), 8.45 (s, 2H), 8.04 (d, J =
8.2 Hz, 2H), 8.02–7.97 (m, 2H), 7.97–7.91 (m, 2H), 7.61–7.54 (m, 4H), 7.43 (d, J = 8.2 Hz, 2H),
3.13 (s, 3H), 3.11 (s, 3H), 1.35–1.24 (m, 21H). 13C NMR (125 MHz, CDCl3): δ 147.0, 133.6,
133.4, 133.0, 132.8, 132.3, 129.8, 128.5, 128.3, 128.1, 127.1, 126.92, 126.85, 123.2, 104.3, 97.2,
93.0, 83.5, 76.5, 73.3, 52.2, 51.9, 18.8, 11.4. 13C NMR (APT, 125 MHz, CDCl3): δ 147.0 (C),
133.6 (C), 133.4 (C), 132.9 (C), 132.8 (C), 132.3 (CH), 129.8 (C), 128.5 (CH), 128.3 (CH),
128.1 (CH), 127.1 (CH), 126.92 (CH), 126.86 (CH), 123.2 (CH), 104.3 (C), 97.2 (C), 93.0 (C),
83.5 (C), 76.5 (C), 73.3 (C), 52.2 (CH3), 52.0 (CH3), 18.8 (CH3), 11.4 (CH). MALDI HRMS m/z
calcd. for C43H43NO4Si (M+) 665.2956, found 665.2958. Anal. calcd. for C43H43NO4Si: C, 77.56;
H, 6.51; N, 2.10. Found: C, 77.34; H, 6.35; N, 2.21.
Compound 4d: To a solution of 2b (0.585 g, 0.993 mmol) and 3c (0.344 g, 1.38 mmol) in THF
(7 mL) and diisopropylamine (5.0 mL, 3.6 g, 35 mmol) which had been deoxygenated for 10 min
with argon was added Pd(PPh3)4 (0.030 g, 0.026 mmol) and CuCl (0.005 g, 0.05 mmol). The
reaction mixture was further deoxygenated for an additional 2 min. The solution was stirred for
12 h at 40 °C before being poured into satd. aq. NH4Cl (150 mL). H2O (100 mL) was added and
25

Page 26 of 35
the mixture was extracted with CH2Cl2 (80 mL, 50 mL). The organic phase was washed with 5%
aq. NH4Cl (150 mL), dried (MgSO4), filtered, and the solvent removed in vacuo. Column
chromatography (silica gel, 2:1 CH2Cl2/hexanes) afforded 4d (0.578 g, 82%) as an off white
foamy solid. Rf = 0.65 (2:1 CH2Cl2/hexanes). IR (microscope): 3056 (w), 2952 (s), 2928 (m),
2896 (m), 2867 (m), 2230 (w), 2169 (w), 1595 (s), 1520 (s) cm–1. 1H NMR (500 MHz, CDCl3): δ
8.70 (s, 2H), 8.44 (s, 2H), 8.03 (d, J = 9.0 Hz, 2H), 8.01–7.96 (m, 2H), 7.96–7.90 (m, 2H), 7.59–
7.54 (m, 4H), 7.42 (d, J = 9.1 Hz, 2H), 3.10 (s, 3H), 3.06 (s, 3H), 2.08 (nonet, J = 6.7 Hz, 3H),
1.11 (d, J = 6.6 Hz, 18H), 0.86 (d, J = 7.0 Hz, 6H). 13C NMR (125 MHz, CDCl3): δ 147.0, 133.6,
133.4, 133.0, 132.8, 132.3, 129.8, 128.5, 128.2, 128.1, 127.1, 127.0, 123.3, 104.4, 97.2, 95.5,
83.5, 76.3, 73.3, 52.2, 52.0, 26.5, 25.3, 25.2, (one signal coincident or not observed). ESI MS m/z
730.3 ([M + Na]+, 48), 676.3 ([M – OMe]+, 100). ESI HRMS m/z calcd. for C46H49NO4SiNa([M
+ Na]+) 730.3323, found 730.3311.
Compound 4e: To a solution of 4d (0.566 g, 0.799 mmol) in THF (80 mL) at –78 °C was added
TBAF (1.0 M in THF, 0.82 mL, 0.82 mmol). The solution was stirred for 1 h at –78 °C before
warming the solution to –15 °C and stirring for an additional 30 min. The reaction mixture was
then poured into satd. aq. NH4Cl (150 mL). H2O (100 mL) was added and the mixture was
extracted with CH2Cl2 (150 mL, 100 mL). The organic phase was washed with 5% aq. NH4Cl
(150 mL), dried (MgSO4), filtered, and the solvent removed in vacuo. Column chromatography
(silica gel, 4:1 hexanes/EtOAc) afforded 4e (0.354 g, 87%) as an off white foamy solid. Rf = 0.31
(4:1 hexanes/EtOAc), 0.50 (CH2Cl2). IR (CH2Cl2 cast film): 3290 (m), 2056 (w), 2936 (w), 2230
1
(vw), 2117 (vw), 1594 (s), 1519 (s) cm–1. H NMR (500 MHz, CDCl3): δ 8.64 (s, 2H), 8.50 (s,
2H), 8.09 (d, J = 9.0 Hz, 2H), 8.03–7.96 (m, 4H), 7.60–7.54 (m, 4H), 7.51 (d, J = 9.0 Hz, 2H),
3.12 (s, 1H), 3.11 (s, 3H), 3.08 (s, 3H). 13C NMR (125 MHz, CDCl3): δ 147.1, 133.4, 133.1,
26

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133.0, 132.7, 132.4, 129.5, 128.3, 128.1, 128.0, 127.3, 127.1, 127.0, 123.4, 96.2, 84.6, 82.4, 78.0,
75.1, 73.9, 52.1, 52.0. ESI MS m/z 532.2 ([M + Na]+, 100). HRMS ESI m/z calcd. for
C34H23NO4Na ([M + Na]+) 532.1519, found 532.1510.
Compound 5: To a solution of 4e (0.307 g, 0.602 mmol) and 3a (0.352 g, 0.909 mmol) in THF
(7 mL) and diisopropylamine (5.0 mL, 3.6 g, 36 mmol) which had been deoxygenated for 10 min
with argon was added Pd(PPh3)4 (0.030 g, 0.026 mmol) and CuCl (0.005 g, 0.05 mmol) followed
by additional deoxygenation with argon for 5 min. The solution was stirred for 14 h at rt before
being poured into satd. aq. NH4Cl (150 mL). H2O (100 mL) was added and the mixture was
extracted with CH2Cl2 (80 mL, 50 mL). The organic phase was washed with 5% aq. NH4Cl (150
mL), dried (MgSO4), filtered, and the solvent removed in vacuo. The crude yellow oil containing
5 was used for the synthesis of 6a without further purification. HRMS ESI m/z calcd. for
C52H54N2O4Si ([M + H]+) 769.4000, found 769.3984.
Compound 6a: To a solution of crude 5 (0.602 mmol, based on 4e) in dry THF (20 mL) that had
been deoxygenated by bubbling through N2 for 5 min was added SnCl2·2H2O (0.271 g, 1.20
mmol). The solution was stirred at rt for 3 h, poured onto a pad of silica gel, eluted with CH2Cl2,
and the solvent was removed in vacuo. Column chromatography (silica gel, CH2Cl2) afforded a
blueꢀgreen solid. The solid was dissolved in minimum CH2Cl2 (ca. 6 mL) after which was added
hexanes (ca. 50 mL). The suspension was cooled to –78 °C and filtered. The solid was washed
with hexanes (5 × 5 mL) to afford 6a (0.263 g, 62%) as a blue solid. Rf = 0.99 (CH2Cl2). UVꢀvis
(CH2Cl2) λmax (ε): 274 (sh, 38 000), 317 (21 6000), 343 (sh, 30 500), 391 (14 300), 440 (7 600),
497 (8 400), 589 (sh, 9 560), 689 (28 400) nm. No significant emission in CH2Cl2. IR (CHCl3,
1
cast) 3045 (w), 2954 (m), 2928 (m), 2857 (w), 2169 (s), 1604 (s), 1590 (s) cm–1. H NMR (500
MHz, CDCl3): δ 8.89 (s, 2H), 8.60 (s, 2H), 8.20 (d, J = 8.5 Hz, 2H), 7.79–7.71 (br s, 4H), 7.70–
27

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7.62 (m, 4H), 7.33–7.26 (m, 4H), 6.73 (d, J = 8.7 Hz, 2H), 3.39 (t, J = 7.7 Hz, 4H), 1.69 (quintet,
13
J = 7.2 Hz, 4H), 1.46–1.34 (m, 12H), 0.95 (t, J = 6.9 Hz, 6H). C NMR (125 MHz, CDCl3): δ
148.5, 146.6, 133.3, 132.1, 131.8, 131.6, 130.7, 130.1, 129.2, 128.6, 128.4, 126.5, 125.9, 125.5,
125.1, 123.7, 121.3, 113.9, 111.4, 108.9, 108.3, 101.8, 94.0, 86.8, 51.1, 31.8, 27.3, 26.9, 22.7,
14.1. ESI HRMS m/z calcd. for C50H46N2O2 (M+) 706.3554, found 706.3542. TGA: Td ≈ 285 °C.
DSC: decomposition, 152 °C (onset), 177 °C (peak).
Compound 8d: To a solution of 1d (0.076 g, 0.13 mmol) in CH2Cl2 (5 mL) was added
tetracyanoethylene (0.012 g, 0.094 mmol). The reaction flask was stirred at rt for 24 h. The
solvent was removed in vacuo and the residue was purified by column chromatography (silica
gel, CH2Cl2) to afford 8d (0.050 g, 74%) as a yellow solid. Rf = 0.70 (CH2Cl2). IR (CHCl3 cast
film): 3049 (w), 2941 (s), 2892 (m), 2864 (s), 2250 (vw), 2199 (m), 2149 (w), 1604 (s) cm–1. 1H
NMR (500 MHz, CDCl3): δ 8.993 (s, 1H), 8.987 (s, 1H), 8.12–8.07 (m, 1H), 8.06–8.00 (m, 1H),
7.77–7.72 (m, 2H), 7.72–7.66 (m, 1H), 7.62–7.54 (m, 3H), 7.54–7.48 (m, 2H), 7.06–7.01 (m,
2H), 5.84 (s, 1H), 5.80 (s, 1H), 3.91 (s, 3H), 1.42–1.24 (m, 21H). 13C NMR (125 MHz, CDCl3):
δ 160.8, 133.8, 133.70, 133.67, 132.9, 132.9, 131.9, 130.5, 130.4, 130.3, 129.6, 129.5, 128.5,
127.19, 127.16, 127.14, 127.03, 126.99, 120.9, 119.9, 114.5, 114.1, 110.9, 110.8, 110.4, 110.2,
106.0, 102.9, 100.5, 82.1, 55.5, 51.9, 51.7, 45.8, 45.7, 18.9, 11.4 (two signals coincident or not
observed). MALDI MS m/z 716.3 (M+, 5), 588.2 ([M – (NC)2C=C(CN)2]+, 100). MALDI HRMS
m/z calcd. for C48H40N4OSi (M+) 716.2966, found 716.2969.
Compound 14b: To a solution of 4b (0.125 g, 0.188 mmol) in CH2Cl2 (9 mL) was added
tetracyanoethylene (0.025 g, 0.20 mmol). The reaction flask was stirred at rt for 15 h, poured
onto a pad of silica gel, eluted with 3:1 hexanes/EtOAc to collect the red band, and the solvent
was removed in vacuo. Column chromatography (silica gel, 4:1 hexanes/EtOAc) afforded 14b
28

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1
1
(0.104 g, 70%) as a red solid. H NMR (500 MHz, CDCl3): δ H NMR (500 MHz, CDCl3): δ
8.64 (s, 1H), 8.61 (s, 1H), 8.23 (br s, 1H), 7.98 (br s, 1H), 7.86 (d, J = 8.1 Hz, 1H), 7.81 (d, J =
8.1 Hz, 2H), 7.71 (br s, 1H), 7.58–7.40 (m, 4H), 7.04 (br s, 2H), 5.95 (d, J = 9.0 Hz, 2H), 3.52 (s,
3H), 3.00 (s, 3H), 2.67 (s, 6H), 1.26–1.19 (m, 21H). 13C NMR (125 MHz, CDCl3): δ 173.8,
162.4, 152.2, 133.8, 133.5, 133.1, 132.9, 132.6, 132.0, 130.6, 130.4, 130.3, 130.0, 128.5, 128.2,
128.1, 128.0, 127.8, 127.7, 127.2, 127.1, 126.8, 118.6, 113.9, 113.0, 112.3, 110.5, 104.6, 93.4,
82.4, 75.4, 52.3, 51.5, 39.5, 18.7, 11.4 (five signals coincident or not observed). ESI MS m/z
814.4 ([M + Na]+, 100), 760.3 ([M – OMe]+, 40). ESI HRMS m/z calcd. for C51H51N5O2SiNa
([M + Na]+) 814.3548, found 814.3537.
Supplementary data
Supplementary data are available with the article through the journal Web site at
http://nrcresearchpress.com/doi/suppl/xxxxx.
Acknowledgements. This work has been generously supported by “Solar Technologies go
Hybrid” – an initiative of the Bavarian State Ministry for Science, Research and Art, the DFG
“Excellence Initiative” supporting the Cluster of Excellence “Engineering of Advanced
Materials” (www.eam.uniꢀerlangen.de), and the Natural Sciences and Engineering Research
Council of Canada (NSERC). D.L. thanks NSERC (PGSꢀD), the Alberta Ingenuity Fund, the
University of Alberta, Alberta Heritage, and the Killam Trusts for scholarship support.
References
1
2
3
Anthony, J. E. Chem. Rev. 2006, 106, 5028–5048.
Anthony, J. E. Angew. Chem. Int. Ed. 2008, 47, 452–483.
Anthony, J. E.; Facchetti, A.; Heeney, M.; Marder, S. R.; Zhan, X. Adv. Mater. 2010 22,
3876–3892.
29

Page 30 of 35
4
5
Bendikov, M.; Wudl, F.; Perepichka, D. F. Chem. Rev. 2004, 104, 4891–4946.
Lehnherr, D.; Murray, A. H.; McDonald, R.; Ferguson, M. J.; Tykwinski, R. R. Chem. Eur.
J. 2009, 15, 12580–12584.
6
7
Vets, N.; Smet, M.; Dehaen, W. Synlett 2005, 217–222.
(a) Lehnherr, D.; Murray, A. H.; McDonald, R.; Tykwinski, R. R. Angew. Chem. Int. Ed.
2010, 49, 6190–6194. (b) Lukman, S.; Musser, A. J.; Chen, K.; Athanasopoulos, S.; Yong,
C. K.; Zeng, Z.; Ye, Q.; Chi, C.; Hodgkiss, J. M.; Wu, J.; Friend, R. H.; Greenham, N. C.
Adv. Funct. Mater. 2015, 25, 5452–5461.
8
9
Lehnherr, D.; Tykwinski, R. R. Aust. J. Chem. 2011, 64, 919–929.
(a) Payne, M. A.; Delcamp, J. H.; Parkin, S. R.; Anthony, J. E. Org. Lett. 2004, 6, 1609–1612. (b)
Anthony, J. E.; Gierschner, J.; Landis, C. A.; Parkin, S. R.; Sherman, J. B.; Bakus II, R. C. Chem.
Commun. 2007, 4746–4748. (c) Reichwagen, J.; Hopf, H.; Desvergne, J.ꢀP.; Guerzo, A. D.;
BouasꢀLaurent, H. Synthesis 2005, 3505–3507. (d) Kitamura, C.; Naito, T.; Yoneda, A.;
Kobayashi, T.; Naito, H.; Komatsu, T. Chem. Lett. 2009, 38, 600–601.
10 (a) Takahashi, T.; Kitamura, M.; Shen, B.; Nakajima, K. J. Am. Chem. Soc. 2000, 122,
12876–12877. (b) Takahashi, T.; Li, S.; Huang, W.; Kong, F.; Nakajima, K.; Shen, B.;
Ohe, T.; Kanno, K.ꢀi. J. Org. Chem. 2006, 71, 7967–7977.
11 (a) Jiang, J.; Kaafarani, B. R.; Neckers, D. C. J. Org. Chem. 2006, 71, 2155–2158. (b)
Bénard, C. P.; Geng, Z.; Heuft, M. A.; VanCrey, K.; Fallis, A. G. J. Org. Chem. 2007, 72,
7229–7236.
12
13
Zhao, Y.; Mondal, R.; Neckers, D. C. J. Org. Chem. 2008, 73, 5506–5513.
(a) Stone, M. T.; Anderson, H. L. J. Org. Chem. 2007, 72, 9776–9778. (b) Lin, C.ꢀH.; Lin,
K.ꢀH.; Pal, B.; Tsou, L.ꢀD. Chem. Commun. 2009, 803–805.
14
(a) Chan, S. H.; Lee, H. K.; Wang, Y. M.; Fu, N. Y.; Chen, X. M. Cai; Z. W.; Wong, H.
N. C. Chem. Commun. 2005, 66–68. (b) Wang, Y.ꢀM.; Fu, N.ꢀY.; Chan, S.ꢀH.; Lee, H.ꢀK.;
Wong, H. N. C. Tetrahedron 2007, 63, 8586–8597.
15 Swartz, C. R.; Parkin, S. R.; Bullock, J. E.; Anthony, J. E.; Mayer, A. C.; Malliaras, G. G.
Org. Lett. 2005, 7, 3163–3166. (b) Tang, M. L.; Oh, J. H.; Reichardt, A. D.; Bao, Z. J. Am.
Chem. Soc. 2009, 131, 3733–3740. (c) Tang, M. L.; Reichardt, A. D.; Wei, P.; Bao, Z. J.
Am. Chem. Soc. 2009, 131, 5264–5273.
30