Ferromagnetic spin alignment in head-to-tail coupled oligo(1,4-phenyleneethynylene)s and oligo(1,4-phenylenevinylene)s bearing pendant p-phenylenediamine radical cations

Article abstract of DOI:10.1021/jo000548o

The intramolecular and long-range ferromagnetic coupling between p-phenylenediamine radical cations in head-to-tail coupled oligo(1,4-phenyleneethynylene)s and oligo(1,4-phenylenvinylene)s between neighbors and next-nearest neighbors is described. UV/vis/near-IR experiments show that the radical cations are localized in the pendant p-phenylenediamine units of the conjugated oligomers. The ESR spectra of these oligo(1,4-phenyleneethynylene) and oligo(1,4-phenylenvinylene) di(radical cation)s are consistent with those of a triplet state. A linear behavior is observed for the doubly integrated ESR intensity of the ΔM(s) = ±1 and ΔM(s) = ±2 signals with the inverse temperature (I ~ 1/T), consistent with Curie's law. This behavior indicates a triplet ground-state diradical with a large triplet-singlet energy gap or possibly a degeneracy of singlet and triplet states.

Full text of DOI:10.1021/jo000548o

5712
J . Org. Chem. 2000, 65, 5712-5719
F er r om a gn etic Sp in Align m en t in Hea d -to-Ta il Cou p led
Oligo(1,4-p h en ylen eeth yn ylen e)s a n d
Oligo(1,4-p h en ylen evin ylen e)s Bea r in g P en d a n t
p-P h en ylen ed ia m in e Ra d ica l Ca tion s
Pauline J . van Meurs and Rene´ A. J . J anssen*
Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology,
P.O. Box 513, 5600 MB Eindhoven, The Netherlands
r.a.j.janssen@tue.nl
Received April 12, 2000
The intramolecular and long-range ferromagnetic coupling between p-phenylenediamine radical
cations in head-to-tail coupled oligo(1,4-phenyleneethynylene)s and oligo(1,4-phenylenvinylene)s
between neighbors and next-nearest neighbors is described. UV/vis/near-IR experiments show that
the radical cations are localized in the pendant p-phenylenediamine units of the conjugated
oligomers. The ESR spectra of these oligo(1,4-phenyleneethynylene) and oligo(1,4-phenylenvinylene)
di(radical cation)s are consistent with those of a triplet state. A linear behavior is observed for the
doubly integrated ESR intensity of the ∆Ms ) (1 and ∆Ms ) (2 signals with the inverse
temperature (I ∼ 1/T), consistent with Curie’s law. This behavior indicates a triplet ground-state
diradical with a large triplet-singlet energy gap or possibly a degeneracy of singlet and triplet
states.
In tr od u ction
p-phenylenediamine units, oxidized to the corresponding
radical cations, allows for an advantageous combination
of generation, stability, and ferromagnetic coupling when
the nitrogen atoms are used to link the radical centers.6
Moreover, the synthesis of arylamines has witnessed a
tremendous progress in recent years using palladium-
catalyzed C-N coupling reactions as developed by Hartwig
et al. and Buchwald et al.9 These improvements have
resulted in the preparation of novel high-spin mol-
ecules.10,11
In the past decade the interest in organic magnetic
materials has increased dramatically.1 Various efforts
have focused on preparing high-spin polyradicals by
creating an alternating sequence of spin-carrying and
ferromagnetic-coupling units in linear, branched, hyper-
branched, and network topologies.1 Considerable progress
in the spin value of these polyradicals can be noted in
recent years. Iwamura et al. have obtained a spin
quantum number of S ) 9 for branched oligocarbenes,2
and more recently Rajca et al. used triarylmethylradicals
in a well-defined dendritic macrocycle and in a π-conju-
gated hydrocarbon network to achieve spin quantum
numbers as high as S ) 10 and S g 40, respectively.3,4
Because of their unusual stability and convenient
generation by one-electron oxidation, arylamine radical
cations have recently been considered in studies on
magnetic organic materials.5-8 Especially the use of
Employing an alternating meta-para topology of oli-
goanilines carrying hydrogen, methyl, or phenyl substit-
uents, we have been able to generate high-spin di-, tri-,
and tetra(radical cations) in linear and branched systems
as model compounds for so-called polaronic ferromag-
nets.6,10 However, in extending these linear and branched
polyarylamines, a problem may arise when incomplete
oxidation of the p-phenylenediamine unit occurs, because
such spin defects are detrimental for achieving a high
spin state, especially when the spin-carrying unit is part
of the main coupling pathway. To overcome this problem
it is possible to use a π-conjugated backbone as a coupling
unit with pendant radical groups.12-14 To ensure ferro-
magnetic coupling between the spin-bearing units of a
pendant polyradical, it is necessary to carefully control
the topology of the substitution pattern along the polymer
* To whom correspondence should be addressed. Phone: +31-40-
247-3597. Fax: +31-40-245-1036.
(1) For a collection of reviews on high-spin organic molecules, see:
Magnetic Properties of Organic Materials; Lathi, P. M., Ed.; Marcel
Dekker: New York, 1999.
(2) Nakamura, N.; Inoue, K.; Iwamura, H. Angew. Chem., Int. Ed.
Engl. 1994, 32, 1884.
(3) Rajca, A.; Wongsriratanakul, J .; Rajca, S.; Cerny, R. Angew.
Chem., Int. Ed. 1998, 37, 1229.
(4) Rajca, A.; Rajca, S.; Wongsriratanakul, J . J . Am. Chem. Soc.
1999, 121, 6308.
(5) Nakamura, Y.; Iwamura, H. Bull. Chem. Soc. J pn. 1993, 66,
3724.
(6) (a) Wienk, M. M.; J anssen, R. A. J . Chem. Commun. 1996, 268.
(b) Wienk, M. M.; J anssen, R. A. J . J . Am. Chem. Soc. 1996, 118, 10625.
(c) Wienk, M. M.; J anssen, R. A. J . J . Am. Chem. Soc. 1997, 119, 4492.
(7) (a) Stickley, K. R.; Selby, T. D.; Blackstock, S. C. J . Org. Chem.
Soc. 1997, 62, 448. (b) Selby, T. D.; Blackstock, S. C. J . Am. Chem.
Soc. 1999, 121, 7152 (c) Selby, T. D., Blackstock, S. C. Org. Lett. 1999,
1, 2053.
(9) For reviews on palladium-catalyzed C-N couplings, see: (a)
Hartwig, J . F. Angew. Chem., Int. Ed. 1998, 37, 2046. (b) Wolfe, J . P.;
Wagaw, S.; Marcoux, J .; Buchwald, S. L. Acc. Chem. Res. 1998, 31,
805. (c) Hartwig, J . F. Acc. Chem. Res. 1998, 31, 852.
(10) Struijk, M. P.; J anssen, R. A. J . Synth. Met. 1999, 103, 2287.
(11) (a) Ito, A.; Taniguchi, A.; Yamabe, T.; Tanaka, K. Org. Lett.
1999, 1, 741. (b) Hauck, S. I.; Lakshmi, K. V.; Hartwig, J . F. Org. Lett.
1999, 1, 2057.
(12) Rajca, A. Chem Rev. 1994, 94, 871.
(13) (a) Lahti, P. M.; Ichimura, A. S. Mol. Cryst. Liq. Cryst. 1989,
176, 125. (b) Lahti, P. M.; Ichimura, A. S. J . Org. Chem. 1991, 56,
3030.
(8) Bushby, R.; McGill, D. R.; Ng, K. M.; Taylor, N. J . Chem. Soc.,
Perkin Trans. 2 1997, 1405.
10.1021/jo000548o CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/09/2000

Ferromagnetic Spin Alignment
J . Org. Chem., Vol. 65, No. 18, 2000 5713
Sch em e 1a
chain in order to guarantee the in-phase periodicity of
spin polarization between adjacent radicals but also
between nonadjacent radicals. The advantage of such
polymers is that they will be less sensitive to spin defects,
because ferromagnetic coupling between next-nearest
neighbors is maintained via the π-conjugated backbone.
Indeed, Nishide et al.14a-c demonstrated that for 1,2- and
1,4-phenylenevinylene-based diradicals there is intra-
chain spin coupling between next-nearest neighbors.
a
Reagents: (a) i: trimethylsilylacetylene, Pd(PPh3)2Cl2, CuI,
Et3N, ii: TBAF, THF; (b) 1,4-diiodobenzene, Pd(PPh3)2Cl2, CuI,
Et3N; (c) 3-bromoiodobenzene, Pd(PPh3)2Cl2, CuI, Et3N; (d) com-
pound 2, Pd(PPh3)2Cl2, CuI, Et3N; (e) Pd2(dba)3, DDPFA, NaOtBu,
N,N’-dimethyl-N-phenyl-1,4-benzenediamine.
Resu lts a n d Discu ssion
Syn th esis of Mod el Com p ou n d s. For the prepara-
tion of 6 and 7 (Scheme 1), 2-bromoiodobenzene was
reacted with trimethylsilylacetylene to give 1-ethynyl-
2-bromobenzene 1 after deprotection. Reaction of 1 with
either 3-bromoiodobenzene or 1,4-diiodobenzene yielded
2,3’-dibromodiphenylacetylene 4 and 2-bromo-4’-iodo-
diphenylacetylene 3, respectively. Compound 3 was then
reacted with 1-ethynyl-3-bromobenzene 2 (synthesized in
the same manner as 1), to yield 3,3’’-dibromodiphenyl-
diacetylene 5. The desired model compounds 6 and 7 were
obtained from 4 and 5 by reaction with N,N’-dimethyl-
N-phenyl-1,4-benzenediamine10 using sodium tert-butox-
ide as a base and tris(dibenzylideneacetone)dipalladium-
(0) (Pd2(dba)3, 1 mol %) and (-)-(R)-N,N’-dimethyl-1-[(S)-
2-(diphenylphosphino)ferrocenyl]ethylamine (DDPFA, 3
mol %) as the catalyst.9 Compounds 6 and 7 were isolated
by column chromatography (SiO2; dichloromethane-hep-
tane, 1:1) in 53% and 65% yields, respectively.
Here we report on the synthesis and characterization
of novel oligo(1,4-phenyleneethynylene)s (62•2+ and 72•2+
)
and oligo(1,4-phenylenevinylene)s (132•2+ and 142•2+) car-
rying pendant p-phenylenediamine radical cations in a
regioregular substitution pattern. The head-to-tail coupled
oligomers 62•2+ and 132•2+ (n ) 0) were designed to
investigate whether ferromagnetic coupling occurs be-
tween neighboring pendant p-phenylenediamine radical
cations attached to p-phenyleneethynylene and p-phe-
nylenevinylene chains, in a topology that favors the in-
phase periodicity of spin polarization at the nitrogen
atoms. The extended oligomers 72•2+ and 142•2+ (n ) 1),
in which the two radical cations are connected by a
π-conjugated chain that incorporates an additional spin-
less monomeric unit, model pendant polyradicals in
which spin-spin interaction can only occur between next-
nearest neighbors We demonstrate using variable tem-
perature ESR that the di(radical cations) of these head-
to-tail coupled conjugated oligomers indeed possess a low-
energy triplet state.
Tetraamines 13 and 14 were synthesized as shown in
Scheme 2. 2-Bromobenzaldehyde was reacted with (3-
bromobenzyl)triphenylphosphonium bromide 8 to give
1-(2-bromophenyl)-2-(3-bromophenyl)ethene 10. (2-Bro-
mobenzyl)triphenylphosphonium bromide 9 was reacted
with terephthaldicarboxaldehyde to give 1-(2-bromophe-
nyl)-2-(4-formylphenyl)ethene 11, which was subse-
quently reacted with (3-bromobenzyl)triphenylphospho-
nium bromide 8 to give dibromide 12. Dibromides 10 and
12 were reacted with N,N’-dimethyl-N-phenyl-1,4-ben-
zenediamine10 using the Pd2(dba)3/DDPFA catalyst sys-
tem as described for 6 and 7, to provide 13 and 14 in
67% and 38% yield, respectively, after isolation by column
chromatography (SiO2; dichloromethane-heptane, 1:1).
R ed ox P r op er t ies. The cyclic voltammograms of
6 and 7 show two chemically reversible oxidation
waves at E0 and E0 (Figure 1a, Table 1). The close
(14) (a) Nishide, H.; Kaneko, T.; Nii, T.; Katoh, K.; Tsuchida, E.;
Yamaguchi, K. J . Am. Chem. Soc. 1995, 117, 548. (b) Nishide, H.;
Kaneko, T.; Nii, T.; Katoh, K.; Tsuchida, E.; Lathi, P. M. J . Am. Chem.
Soc. 1996, 118, 9695. (c) Nishide, H.; Kaneko, T.; Toriu, S.; Kuzamaki,
Y.; Tsuchida, E. Bull. Chem. Soc. J pn. 1996, 69, 499. (d) Nishide, H.;
Miyasaka, M.; Tsuchida, E. Angew. Chem., Int. Ed. 1998, 37, 2400.
(e) Nishide, H.; Maeda, T.; Oyaizu, K.; Tsuchida, E. J . Org. Chem. 1999,
64, 7129. (f) Michinobu, T.; Takahashi, M.; Tsuchida, E.; Nishide, H.
Chem. Mater. 1999, 111, 1969. (g) Takahashi, M.; Nakazawa, T.;
Tsuchida, E.; Nishide, H. Macromolecules 1999, 32, 6383.
1
2
correspondence of the oxidation potentials of 6 and 7 with

5714 J . Org. Chem., Vol. 65, No. 18, 2000
van Meurs and J anssen
Sch em e 2a
a
Reagents: (a) i: BuLi, ii; I2; (b) BuLi; (c) i: BuLi, compound 8, ii: I2; (d) Pd2(dba)3, DDPFA, NaOtBu, N,N’-dimethyl-N-phenyl-1,4-
benzenediamine.
Ta ble 1. Oxid a tion P oten tia ls of Mod el Com p ou n d s 6, 7,
13, 14, a n d 15a
E0 (V)
E0 (V)
1
2
6
0.42; 0.45
0.42
1.02
1.01
1.07
1.05
1.02
7
13
14
15
0.49
0.44
0.42
Determined in CH2Cl2/Bu4+NPF6 (0.1 mol dm-3) at 295 K,
a
-
scan rate 100 mV s-1, potential vs SCE calibrated using Fc/Fc+.
the oxidation waves shown in Figure 1 corresponds to a
two-electron oxidation process, and oxidation of the
p-phenylenediamine units occurs, rather than of the
conjugated backbone. For 6 the first oxidation wave is
somewhat broader than for 7, and careful inspection
suggests the presence two consecutive one-electron trans-
fers with only slightly different oxidation potentials
(Table 1). The increased distance between the two p-
phenylenediamine units of 7 in comparison with 6
explains the slightly different behavior. The cyclic vol-
tammograms of 13 and 14 show very similar results and
are likewise identified with the generation of pendant
p-phenylenediamine radical cations in the first wave and
the corresponding pendant dications in the second wave.
For 14 there is an additional shoulder in the voltammo-
gram at 0.93 V, which is tentatively ascribed to the
oxidation of the oligo(p-phenylenevinylene) backbone.
UV/vis/n ea r -IR Absor p tion Sp ectr oscop y. Quan-
titative conversion of the tetraamines to the different
oxidation states has been achieved by chemical oxidation
using thianthrenium perchlorate,15 and these reactions
can be monitored with UV/vis/near-IR absorption spec-
troscopy.
F igu r e 1. Cyclic voltammograms of (a) 6 (solid line) and 7
(dashed line) and (b) 13 (solid line) and 14 (dashed line),
determined in CH2Cl2/Bu4+NPF6 (0.1 mol dm-3) at 295 K,
-
scan rate 100 mV s-1, potential vs SCE calibrated using
Fc/Fc+.
those of N,N’-dimethyl-N,N’-diphenyl-1,4-benzenedi-
amine (15) implies that at E0 radical cations of the
1
pendant p-phenylenediamine groups are generated and,
hence, at this potential radical cations and di(radical
cation)s of 6 and 7 are formed. Likewise, E02 is associated
with the formation of the corresponding spinless p-
phenylenediamine dications, and thus the formation of
trications and tetracations of 6 and 7. Therefore each of
(15) Murata, Y.; Shine, H. J . J . Org. Chem. 1969, 34, 3368.

Ferromagnetic Spin Alignment
J . Org. Chem., Vol. 65, No. 18, 2000 5715
F igu r e 2. Normalized absorption spectra of neutral oligomers
6 (solid line), 7 (dashed line), 13 (dotted line), and 14 (dot-
dashed line) recorded in dichloromethane at 295 K.
The electronic absorption spectrum of neutral 6 shows
two bands at 4.12 and 4.32 eV (Figure 2). Stepwise oxi-
dation of 6 with thianthrenium perchlorate in dichlo-
romethane results in the gradual appearance of two new
bands in the spectrum at 2.01 and 3.48 eV, associated
with the formation of pendant p-phenylenediamine radi-
cal cations while the bands at 4.12 and 4.32 eV decrease.
The new absorption bands are associated with both the
radical cations (6•+) and di(radical cation)s (62•2+) of the
parent oligomer (6). After 2 equiv were added, the bands
at 2.01 and 2.38 eV reached the maximum intensity, dem-
onstrating the near quantitative formation of the di-
(radical cation) (62•2+) in which each p-phenylenediamine
unit carries an unpaired electron. Further oxidation by
addition of more than 2 equiv of thianthrenium per-
chlorate results in a new absorption band at 2.71 eV of
doubly oxidized p-phenylenediamine units, i.e. trications
(6•3+) and tetracations (64+), and a simultaneous loss of
the radical cation bands of 62•2+ at 2.01 and 3.48 eV
(Figure 3).
F igu r e 3. (a) UV/vis/near-IR spectra of 6 oxidized stepwise
to 62•2+. The dotted line is the absorption of neutral 6; the
dashed line is of 64+. (b) UV/vis/near-IR spectra of 7 oxidized
stepwise to 72•2+. The dotted line is the absorption of neutral
7; the dashed line is of 74+. The symbols (+•) and (++) indicate
the transitions of the pendant p-phenylenediamine radical
cations and dications, respectively.
As a result of the increased length of the π-conjugated
oligomer, the absorption spectrum of neutral 7 at 3.91
eV has shifted to lower energy in comparison to 6 (Figure
2). Similar to 6, oxidation of 7 results in a loss of the
neutral absorption spectrum and the concomitant in-
crease of two electronic absorptions at 2.00 and 3.50 eV,
associated with radical cations (7•+) and di(radical cat-
ion)s (72•2+). Upon further oxidation these bands decrease
again and are replaced by a new electronic absorption
at 2.76 eV, associated with the formation of trications
(7•3+) and tetracations (74+) (Figure 3).
The absorption maximum of neutral 13 at 4.07 eV is
at lower energy than the absorption of neutral 6 (Figure
2). This indicates an enhanced π-conjugation of the
p-phenylenevinylene backbone in comparison with the
p-phenyleneethynylene backbone. In a similar fashion as
for 6 and 7, stepwise oxidation of 13 with thianthrenium
perchlorate results in two new absorption bands in the
spectrum at 2.02 and 3.41 eV, indicative of the formation
F igu r e 4. (a) UV/vis/near-IR spectra of 13 oxidized stepwise
to 132•2+. The dotted line is the absorption of neutral 13; the
dashed line is of 134+. (b) UV/vis/near-IR spectra of 14 oxidized
stepwise to 142•2+. The dotted line is the absorption of neutral
14; the dashed line is of 144+. The symbols (+•) and (++)
indicate the transitions of the pendant p-phenylenediamine
radical cations and dications, respectively.
of the radical cations (13•+) and di(radical cations) (132•2+
)
(Figure 4). These bands reach a maximum intensity after
addition of exactly 2 equiv and then decrease with further
oxidation to make place for a new band at 2.70 eV of
trications (13•3+) and tetracations (134+). Compared to 13,
the absorption bands of neutral 14 at 3.56 and 3.90 eV
are shifted to lower energy because of the increased
π-conjugation (Figure 2). Compared to 6 and 7 there is a
larger shift to lower energy in going from 13 to 14,
indicating a more pronounced increase of conjugation
length with size for the vinylene oligomers. Upon oxida-
tion of 14, two absorption bands appear at 2.02 and 3.51
eV and the neutral bands are decreasing, which can be
ascribed to formation of p-phenylenediamine radical
cations 14•+ and 142•2+ (Figure 4). Addition of more than
2 equiv of thiantrenium perchlorate to 14 gives rise to a
new absorption band at 2.70 eV of 14•3+ and 144+ as in
the case of 13 (Figure 4).

5716 J . Org. Chem., Vol. 65, No. 18, 2000
van Meurs and J anssen
estimates are quite limited in precision due to lack of
experimental resolution. The relatively low D values are
a direct result of the large distance between the radical
centers, and the narrowing of the ESR spectrum for 72•2+
with respect to 62•2+ is consistent with the extension of
the molecule. Within the magnetic dipole-dipole ap-
proximation the distance between the radical centers is
related to the dipolar coupling via D ) 78000 × d-3
.
Using the D-value estimates for 62•2+ and 72•2+ of 70 and
e30 MHz, this suggests d ) ∼10 Å and d g 14 Å,
respectively, as the distances between the radical centers
in the two di(radical cation)s. These distances are con-
sistent with values of ∼12 Å and d g 14 Å between the
centers of the two p-phenylenediamine rings estimated
from molecular modeling assuming an anti orientation.
F igu r e 5. ESR spectra of 62•2+ (solid line) and 72•2+ (dashed
line) recorded in butyronitrile at 4 K. The upper inset
represents the ∆Ms ) (2 spectrum of 62•2+ and the lower inset
the ∆Ms ) (2 spectrum of 72•2+
.
The ESR spectra of 132•2+ and 142•2+ recorded at 4 K
show similar signals in the ∆Ms ) (1 region with a width
of ∼43.5 and ∼19.1 G, respectively. In addition both di-
(radical cation)s show a ∆Ms ) (2 transition at half field,
characteristic of a triplet state (Figure 6). The narrowing
of the signal in 142•2+ in comparison with 132•2+ can be
ascribed, as in the case of 72•2+, to the elongation of the
molecule and the concomitant decrease of the dipolar
spin-spin coupling. In the ESR spectra of 132•2+ and
142•2+ there is, again, no fine structure present in the ∆Ms
) (1 region, but likewise it is possible to estimate the
zero-field parameters D and E by spectral simulation
even though the accuracy will be limited. For 132•2+ it is
found that the spectrum is consistent with D ) 80 ( 5
MHz and E ≈ 0 MHz, while for 142•2+ D e 20 MHz and
E ≈ 0 MHz was found. As in the case of 6 and 7, the low
zero-field splitting can be ascribed to the large distance
between the radical centers. The lower D value for 14
with respect to 13 is consistent with the extension of the
molecule. From the relation D ) 78000 × d-3 it is possible
to estimate the distance between the radical centers. For
132•2+ this yields d ) ∼10 Å and for 142•2+ d g ∼16 Å.
When the pendant radicals are in an anti conformation,
molecular modeling gives ∼12 Å and ∼17 Å, for 13 and
14, respectively, in fair agreement with these experi-
mental estimates. The low-intensity ∆Ms ) (2 signal for
142•2+ is consistent the low D value of this di(radical
cation) since the theoretical ratio of the ∆Ms ) (1 and
(2 transitions is 1:(D/B0)2, or 1:4 × 10-6 under the
present conditions.16
F igu r e 6. ESR spectra of 132•2+ (solid line) and 142•2+ (dashed
line) recorded in butyronitrile at 4 K. The upper inset
represents the ∆Ms ) (2 spectrum of 132•2+ and the lower inset
the ∆Ms ) (2 spectrum of 142•2+
.
These chemical oxidation experiments show that for
all four compounds it is possible to carefully tune the
oxidation level by addition of thiantrenium perchlorate
as the oxidizing agent. In this way it is possible to
selectively achieve a state in which both p-phenylenedi-
amine units of 6, 7, 13, and 14 are oxidized to the cation
radical. The close correspondence between the electronic
spectra of 62•2+, 72•2+, 132•2+, and 142•2+ demonstrates the
localized nature of the radical cation in the p-phenylene-
diamine unit.
ESR Sp ectr oscop y. The ESR spectrum of 62•2+ re-
corded at 4 K shows a broad signal with a width of ∼37.5
G in the ∆Ms ) (1 region and a ∆Ms ) (2 transition at
half field, characteristic of a triplet state (Figure 5). The
ESR spectrum of 72•2+ recorded under similar conditions
is much narrower, with a width of ∼23.5 G, but also
shows a ∆Ms ) (2 transition associated with a triplet
state. Despite the lack of fine structure in the ∆Ms ) (1
region of 62•2+ and 72•2+, it is possible to estimate the zero-
field parameters D and E by spectral simulation. For the
simulation we first measured the ESR spectrum of the
N,N’-dimethyl-N,N’-diphenyl-1,4-benzenediamine radical
cation (15•+) under the same conditions to obtain the
intrinsic line width (∼20 G) of the pendant radicals.
Using this line width it is then possible to simulate the
ESR spectrum of the triplet states of 62•2+ and 72•2+. We
find that the ESR spectrum of 62•2+ is consistent with D
) 70 ( 5 MHz and E ≈ 0 MHz, while for 72•2+ D e 30
MHz and E ≈ 0 MHz. Given that only a single peak is
observed in the ESR spectra, it must be noted that these
Deter m in a tion of th e Gr ou n d Sta tes. Temperature-
dependent ESR experiments show a linear relation for
the doubly integrated ESR intensity (I) of the ∆Ms ) (1
and ∆Ms ) (2 signals of both 62•2+ and 72•2+ as a function
of the reciprocal temperature between 4 and 100 K,
consistent with Curie’s law (I ∼ 1/T) (Figure 7a). Similar
temperature-dependent ESR results were obtained for
132•2+ and 142•2+ (Figure 7b); however, the ∆Ms ) (2
signal of 142•2+ could only be measured between 4 and
60 K. Apparently, no population or depopulation of the
high-spin states occurs in these temperature regions.
This behavior is consistent with a triplet ground-state
diradical with a large triplet-singlet energy gap but also
with a degeneracy of singlet and triplet states for 62•2+
2•2+, 132•2+ and 142•2+. In either case, however, the triplet
state corresponds to a low-energy state.
,
7
(16) Weismann, S. I.; Kothe, G. J . Am. Chem. Soc. 1975, 97, 2538.

Ferromagnetic Spin Alignment
J . Org. Chem., Vol. 65, No. 18, 2000 5717
tions were carried out with a spin Hamiltonian incorporating
the electron Zeeman term and the dipolar spin-spin coupling.
The g value was assumed to be isotropic.
Ma ter ia ls. Commercial grade reagents were used without
further purification. Solvents were purified, dried, and de-
gassed following standard procedures. Thianthrenium per-
chlorate was prepared according to literature.15 Ca u tion :
Thianthrenium perchlorate is a shock-sensitive explosive solid
that should be handled on small scale only. N,N’-Dimethyl-
N-phenyl-1,4-benzenediamine,10 (3-bromobenzyl)triphenylphos-
phonium bromide (8),17 (2-bromobenzyl)triphenylphosphonium
bromide (9),17 and N,N’-dimethyl-N-phenyl-1,4-benzenedi-
amine (15)10 were prepared as described in the literature.
1-Eth yn yl-2-br om oben zen e (1). 2-Bromoiodobenzene (10
mmol, 2.83 g) was dissolved in 20 mL of triethylamine. Argon
was lead through the reaction mixture for 30 min. Trimeth-
ylsilylacetylene (12 mmol, 1.2 g), bis(triphenylphospine)-
palladium(II) chloride (10 mol %, 200 mg), and copper(I) iodide
(10 mol %, 100 mg) were added, and the reaction mixture was
stirred for 3 h at room temperature. Then the reaction mixture
was poured into water and extracted with dichloromethane
(3×). The organic layers were washed with brine and dried
over MgSO4. The organic layer was evaporated in vacuo. The
crude product was purified by column chromatography (SiO2;
heptane) yielding a colorless liquid (1.91 g, 75%). The liquid
was dissolved in 20 mL of THF, and subsequently an equimo-
lar amount of tetrabutylammonium fluoride (TBAF) was
added. The reaction mixture was stirred for 1 h at room
temperature after which it was poured into a saturated NH4-
Cl solution and extracted with dichloromethane (3×). The
organic layers were washed with brine and dried over MgSO4.
The solvent was removed in vacuo. The crude product was
purified by column chromatography (SiO2; heptane) yielding
a yellow liquid (0.84 g, 62%): 1H NMR (CDCl3) δ 7.59 (dd, J
) 8.1, 0.7 Hz, 1H) 7.53 (dd, J ) 7.7, 1.8 Hz, 1H) 7.27 (dt, J )
8.1, 1.5 Hz, 1H) 7.20 (dt, J ) 7.7, 1.8 Hz) 3.38 (s, 1H); 13C
NMR (CDCl3) δ 134.06, 132.42, 129.96, 126.97, 125.53, 124.24,
81.87, 81.79.
F igu r e 7. Temperature dependence of the ESR signal inten-
sity of the di(radical cation)s: (a) 62•2+ (0: ∆Ms ) ,(1; O: ∆Ms
) (2) and 72•2+ (9: ∆Ms ) (1; b: ∆Ms ) (2); (b) 132•2+ (0:
∆Ms ) (1; O: ∆Ms ) (2) and 142•2+ (9: ∆Ms ) (1; b: ∆Ms
) (2). Solid lines are least-squares fits to Curie’s law.
Con clu sion s
We have prepared triplet state di(radical cation)s of
novel head-to-tail coupled oligo(1,4-phenyleneethynylene)s
and oligo(1,4-phenylenevinylene)s carrying N,N’-dim-
ethyl-N’-phenyl-1,4-benzenediamine pendant groups. The
zero-field splitting in these pendant di(radical cation)s
is reduced compared to di(radical cation)s coupled via a
1,3-phenylene unit6 as a result of the increased separa-
tion between the radical centers. Although the magnitude
of the exchange interaction could not be determined from
the ESR experiments, the presence of ∆Ms ) (2 ESR
signals and their increasing intensity at lower temper-
ature suggest that ferromagnetic coupling occurs between
p-phenylenediamine radical cations in regioregular sub-
stituted π-conjugated chains between neighbors and
possibly also between next-nearest neighbors. These
results give support to view that pendant p-phenylene-
diamine radical cations, regioregularly substituted on a
conjugated polymer chain, constitute a promising ap-
proach toward future stable high-spin polymers. Work
is in progress for the synthesis of such appealing systems.
1-Eth yn yl-3-br om oben zen e (2) was prepared as described
for 1-ethynyl-2-bromobenzene 1 but 3-bromoiodobenzene was
used instead affording the title compound as a light yellow
liquid (74%): 1H NMR (CDCl3) δ 7.64 (t, J ) 1.5 Hz, 1H) 7.48
(dt, J ) 8.1, 1.1 Hz, 1H) 7.42 (dt, J ) 7.7, 1.5 Hz, 1H) 7.19 (t,
J ) 8.1 Hz, 1H) 3.12 (s, 1H); 13C NMR (CDCl3) δ 134.86,
132.00, 130.68, 129.74, 124.09, 122.09, 82.02, 78.52.
2-Br om o,4’-iod od ip h en yla cetylen e (3). 1-Ethynyl-2-bro-
mobenzene 1 (3 mmol, 0.55 g) and 1,4-diiodobenzene (6 mmol,
1.98 g) were dissolved in triethylamine (10 mL). Argon was
bubbled through the reaction mixture for 30 min. Then bis-
(triphenylphosphine)palladium(II) chloride (10 mol %, 60 mg)
and copper(I) iodide (10 mol %, 30 mg) were added to the
reaction mixture. The reaction mixture was stirred for 3 h at
room temperature after which it was poured into water and
extracted with dichloromethane (3×). The combined organic
layers were washed with brine and dried over MgSO4. The
solvent was removed in vacuo, affording the crude product
which was purified by column chromatography (SiO2; heptane)
affording a white solid (0.56 g, 49%) mp: 70.7-73.2 °C. 1H
NMR (CDCl3) δ 7.70 (dt, J ) 8.4, 1.8 Hz, 2H) 7.61 (dd, J )
8.1, 1.1 Hz, 1H) 7.54 (dd, J ) 7.6, 1.8 Hz, 1H) 7.30 (m, 3H)
7.19 (dt, J ) 7.5, 1.8 Hz, 1H); 13C NMR (CDCl3) δ 137.54,
133.19, 133.11, 132.48, 129.63, 127.86, 125.60, 125.01, 122.36,
94.65, 92.63, 89.34. Anal. Calcd for C14H8BrI: C, 43.90; H, 2.10.
Found: C, 43.90; H, 2.24.
Exp er im en ta l Section
Gen er a l Meth od s. NMR chemical shifts are relative to
TMS. Matrix-assisted laser-desorption ionization/time-of-flight
(MALDI/TOF) mass spectra were recorded using R-cyano-4-
hydroxycinnamic acid as a matrix. Cyclic voltammograms were
recorded with 0.1 M tetrabutylammonium hexafluorophos-
phate as supporting electrolyte. The working electrode was a
platinum disk (0.2 cm2), the counter electrode was a platinum
plate (0.5 cm2), and a saturated calomel electrode was used
as reference electrode, calibrated against a Fc/Fc+ couple. ESR
spectra were recorded at X-band. An NMR gauss meter and
frequency counter were used for field-frequency callibration.
Temperature was controlled in a continuous helium flow
cryostat. Saturation of the ESR signal during variable tem-
perature experiments was avoided by using low microwave
powers in a range such that signal intensity is proportional
to square root of the microwave power at 4 K. For double
integration spectra were baseline corrected. Powder simula-
2,3’-Dib r om od ip h en yla cet ylen e (4). 1-Ethynyl-2-bro-
mobenzene 2 (5 mmol, 0.92 g) and 3-bromoiodobenzene (6
mmol, 1.7 g) were dissolved in triethylamine (15 mL). Argon
was bubbled through the reaction mixture for 30 min. Then
bis(triphenylphosphine)palladium(II) chloride (10 mol %, 100
mg) and copper(I) iodide (10 mol %, 50 mg) were added to the
reaction mixture. The reaction mixture was stirred for 2 h at
(17) Wallace, T. W.; Wardell, I.; Li, K.; Leeming, P.; Redhouse, A.
D.; Challand, S. R. J . Chem. Soc., Perkin Trans. 1 1995, 18, 2293.

5718 J . Org. Chem., Vol. 65, No. 18, 2000
van Meurs and J anssen
room temperature after which it was poured into water and
extracted with dichloromethane (3×). The combined organic
layers were washed with brine and dried over MgSO4. The
solvent was removed in vacuo affording the crude product
which was purified by column chromatography (10% CH2Cl2
in n-heptane) affording a white solid (1,34 g, 80%) mp: 57.0-
58.4 °C: 1H NMR (CDCl3) δ 7.73 (t, J ) 2.2 Hz, 1H) 7.63 (dd,
J ) 8.1, 1.1 Hz, 1H) 7.55 (dd, J ) 7.7, 1.5 Hz, 1H) 7.49 (m,
2H) 7.30 (dt, J ) 7.3, 1.1 Hz, 1H) 7.23 (t, J ) 8.1 Hz, 1H) 7.20
(dt, J ) 7.7, 1.1 Hz, 1H); 13C NMR (CDCl3) δ 134.31, 133.28,
132.49, 131.75, 130.22, 129.61, 129.73, 127.08, 125.70, 124.68,
122.18, 92.17, 89.18. Anal. Calcd for C14H8Br2: C, 50.04; H,
2.40. Found: C, 50.35; H, 2.52.
2-Br om o,3’’-d ib r om ot r ip h en ylen ed ia cet ylen e (5). 2-
Bromo,4’-iododiphenylacetylene 4 (1.0 mmol, 0.38 g) and
1-ethynyl-3-bromobenzene 2 (1.0 mmol, 0.18 g) were dissolved
in triethylamine (5 mL). Argon was lead through the reaction
mixture for 30 min. Then bis(triphenylphosphine)palladium-
(II) chloride (10 mol %, 20 mg) and copper(I) iodide (10 mol %,
10 mg) were added, and the reaction mixture was stirred
overnight at room temperature. The reaction mixture was then
poured into water and extracted with dichloromethane (3×).
The combined organic layers were washed with brine and dried
over MgSO4. The solvent was then removed in vacuo, and the
crude product was purified by column chromatography (10%
CH2Cl2 in n-heptane) affording a pale yellow solid (0.25 g, 57%)
mp: 94.9-96.7 °C. 1H NMR (CDCl3) δ 7.70 (t, J ) 1.8 Hz, 1H)
7.63 (dd, J ) 8.0, 1.1 Hz, 1H) 7.56 (m, 3H) 7.49 (m, 4H) 7.31
(dt, J ) 7.5, 1.1 Hz, 1H) 7.23 (t, J ) 7.9 Hz, 1H) 7.20 (dt, J )
7.9, 1.7 Hz, 1H); 13C NMR (CDCl3) δ 134.31, 133.25, 132.49,
131.60, 130.14, 129.63, 127.08, 125.09, 124.97, 123.07, 122.69,
122.20, 90.28, 89.72. Anal. Calcd for C22H12Br2: C, 60.58; H,
2.77. Found: C, 60.29; H, 2.85.
) 7.4, 1.0 Hz, 1H) 6.88 (dd, J ) 8.2, 2.3 Hz, 1H) 6.82 (d, J )
8.5 Hz, 1H) 6.74 (m, 2H) 3.43 (s, 3H) 3.35 (s, 3H) 3.32 (s, 3H)
3.25 (s, 3H); 13C NMR (CDCl3) δ 151.25, 150.73, 150.28, 147.07,
145.87, 143.63, 141.34, 134.91, 132.39, 132.32, 130.91, 130.20,
130.04, 129.88, 127.50, 127.06, 125.89, 125.65, 124.52, 124.11,
124.04, 123.42,121.66, 121.62, 120.39, 120.37, 118.86, 118.40,
117.75, 116.27, 95.87, 92.93, 90.47, 89.62, 41.66, 41.55. Anal.
Calcd for C50H42N4: C, 85.9; H, 6.1; N, 8.0. Found: C, 86.1; H,
5.65; N, 7.97. Mass calcd: 698.34. Found: 698.27.
1-(2-Br om op h en yl)-2-(3-br om op h en yl)eth en e (10). To
a suspension of (3-bromobenzyl)triphenylphosphonium bro-
mide 8 (4 mmol, 2.1 g) in dry THF (30 mL) was added n-BuLi
(4.2 mmol) at -30 °C. The reaction mixture was stirred for 5
min at -20 °C and then cooled to -30 °C. At this temperature
2-bromobenzaldehyde (4 mmol, 0.74 g) in dry THF (8 mL) was
added at such a rate that the temperature did not rise above
-20 °C. The reaction mixture was slowly warmed to room
temperature and stirred overnight at this temperature. Then
the reaction mixture was poured into water and extracted with
diethyl ether (3×). The combined organic layers were washed
with brine and dried over MgSO4. The solvent was removed
in vacuo. Addition of n-hexane to the resulting yellow oil gave
a white precipitate, which was removed by filtration. The
filtrate was concentrated in vacuo. After column chromatog-
raphy with n-hexane a colorless oil (1.12 g, 83%) was obtained
which was a mixture of cis- and trans-dibromide. The oil was
refluxed in toluene in the presence of a catalytic amount of
iodine overnight. The solvent was removed in vacuo, and the
brown oil was chromatographed on silica with n-hexane
affording a white solid (0.9 g, 67%) which was the trans-
dibromide according to NMR, mp: 41.2-43.0 °C. 1H NMR
(CDCl3) δ 7.69 (t, J ) 1.8 Hz, 1H) 7.65 (dd, J ) 5.1, 1.8 Hz,
1H) 7.59 (dd, J ) 8.1, 1.5 Hz) 7.50-7.28 (m, 3H) 7.24 (t, J )
7.7 Hz, 1H) 7.14 (dt, J ) 7.7, 1.5 Hz, 1H) 7.05 (d, J ) 16.1 Hz,
1H) 6.95 (d, J ) 16.1 Hz, 1H); 13C NMR (CDCl3) δ 139.13,
136.61, 133.12, 130.84, 130.19, 129.83, 129.59, 129.17, 128.85,
OP E2-tetr a a m in e (6). An oven-dried Schlenk flask was
charged with 2,3’-dibromodiphenylacetylene 4 (1 mmol, 0.34
g), N,N’-dimethyl-N-phenyl-1,4-benzenediamine (2 mmol, 0.43
g), sodium tert-butoxide (2.4 mmol, 0.23 g), tris(dibenzylide-
neacetone)dipalladium(0) (1 mol %, 9.2 mg), and (-)-(R)-N,N’-
dimethyl-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethylamine (3
mol %, 18.8 mg). After purging with argon, dry toluene (2 mL)
was added, and the reaction mixture was heated at 80 °C
overnight. The reaction mixture was poured into water and
extracted with dichloromethane (3×). The combined organic
layers were washed with water and dried over MgSO4. The
solvent was removed in vacuo affording a brown thick oil which
was purified by column chromatography (50% CH2Cl2 in
n-heptane) affording a pale yellow solid (0.32 g, 53%) mp:
127.58, 126.76, 125.41, 124.26, 122.91. Anal. Calcd for C14H10
Br2: C, 49.74; H, 2.98. Found: C, 50.28; H, 2.91.
-
1-(2-Br om op h en yl)-2-(4-for m ylp h en yl)eth en e (11). To
a suspension of (2-bromobenzyl)triphenylphosphonium bro-
mide 9 (4 mmol, 2.1 g) in dry THF (30 mL) was added n-BuLi
(4.2 mmol) at -30 °C. The reaction mixture was stirred for 5
min at -20 °C and then cooled to -30 °C. At this temperature
terephthaldicarboxaldehyde (8 mmol, 1.1 g) in dry THF (8 mL)
was added rapidly. The reaction mixture was slowly warmed
to room temperature and stirred overnight at this temperature.
Then the reaction mixture was poured into water and ex-
tracted with diethyl ether (3×). The combined organic layers
were washed with brine and dried over MgSO4. The solvent
was removed in vacuo. Addition of n-hexane to the resulting
yellow oil gave a white precipitate, which was removed by
filtration. The filtrate was concentrated in vacuo. After column
chromatography with 20% ethyl acetate in n-hexane a light
yellow oil (0.92 g, 80%) was obtained which was a cis/ trans
mixture of the title compound. 1H NMR (CDCl3) δ 10.01 + 9.93
(s, 1H) 7.89 (dd, J ) 6.2, 1.5 Hz, 1H) 7.70-7.60 (m, 3H) 7.40-
7.26 (m, 2H) 7.19-7.09 (m, 2H) 6.79 (d, J ) 12.1 Hz, 1H) 6.72
(d, J ) 12.1 Hz, 1H); 13C NMR (CDCl3) δ 191.64, 191.55,
142.98, 142.73, 137.25, 136.39, 135.64, 135.05, 133.23,132.88,
132.38, 130.82, 130.69, 130.23, 130.21, 130.03, 129.61, 129.56,
129.51, 129.21, 127.66, 127.24, 127.18, 126.89, 124.50, 123.76.
OP V3-d ibr om id e (12). To a suspension of (3-bromobenzyl)-
triphenylphosphonium bromide 8 (3 mmol, 1.53 g) in dry THF
(25 mL) was added n-BuLi (3.2 mmol) at -30 °C. The reaction
mixture was stirred for 5 min at -20 °C and then cooled to
-30 °C. At this temperature aldehyde 11 (3 mmol, 0.9 g) in
dry THF (6 mL) was added at such a rate that the temperature
did not rise above -20 °C. The reaction mixture was slowly
warmed to room temperature and stirred overnight at this
temperature. Then the reaction mixture was poured into water
and extracted with diethyl ether (3×). The combined organic
layers were washed with brine and dried over MgSO4. The
solvent was removed in vacuo. Addition of n-hexane to the
resulting yellow oil gave a white precipitate, which was
removed by filtration. The filtrate was concentrated in vacuo.
1
110.5-113.6 °C. H NMR (CDCl3) δ 7.58 (dd, J ) 7.7, 1.5 Hz,
1H) 7.37 (dt, J ) 7.7, 1.8 Hz, 1H) 7.28 (m, 7H) 7.16 (m, 5H)
7.02-6.97 (m, 4H) 6.93 (t, J ) 1.1 Hz, 1H) 6.88 (t, J ) 1.5 Hz,
1H) 6.83 (dd, J ) 8.4, 1.1 Hz, 1H) 6.74 (m, 5H) 3.41 (s, 3H)
3.33 (s, 3H) 3.27 (s, 3H) 3.23 (s, 3H); 13C NMR (CDCl3) δ
151.16, 150.79, 150.05, 147.26, 145.59, 143.90,141.07, 134.89,
130.56, 130.16, 129.84, 127.69, 127.20, 125.73, 125.49, 124.83,
123.71, 123.52, 122.13, 121.41, 120.60, 119.98, 118.62, 118.51,
117.50, 116.09, 96.60, 87.92, 41.64, 41.55. Anal. Calcd for
C
42H38N4: C, 84.2; H, 6.4; N, 9.4. Found; C, 83.89; H, 6.56; N,
9.19. MS calcd for C42H38N4: 598.31. Found: 598.19.
OP E3-tetr a a m in e (7). An oven-dried Schlenk flask was
charged with 2,3’’-dibromodiphenyldiacetylene 6 (0.9 mmol,
0.39 g), N,N’-dimethyl-N-phenyl-1,4-benzenediamine (2 mmol,
0.43 g), sodium tert-butoxide (2.4 mmol, 0.23 g), tris(diben-
zylideneacetone)dipalladium(0) (1 mol %, 9.2 mg), and (-)-
(R)-N,N’-dimethyl-1-[(S)-2-(diphenylphosphino)ferrocenyl]-
ethylamine (3 mol %, 18.8 mg). After purging with argon, dry
toluene (2 mL) was added, and the reaction mixture was
heated at 80 °C for 2.5 days. The reaction mixture was poured
into water and extracted with dichloromethane (3×). The
combined organic layers were washed with water and dried
over MgSO4. The solvent was removed in vacuo affording a
brown thick oil which was purified by column chromatography
(50% CH2Cl2 in n-heptane) affording a yellow solid (0.41 g,
65%) mp: 126.7-130.1 °C. 1H NMR (CDCl3) δ 7.58 (d, J ) 7.7
Hz, 1H) 7.43 (d, J ) 8.0 Hz, 1H) 7.39 (t, J ) 6.7 Hz, 1H) 7.32-
7.24 (m, 2H) 7.24-7.14 (m, 5H) 7.09-7.00 (m, 6H) 6.94 (td, J

Ferromagnetic Spin Alignment
J . Org. Chem., Vol. 65, No. 18, 2000 5719
After column chromatography with n-hexane, a colorless oil
(1.06 g, 80%) was obtained which was a mixture of cis/ trans
isomers. The product was refluxed in toluene in the presence
of a catalytic amount of iodine overnight. The solvent was
removed in vacuo affording a brownish solid which was the
trans-isomer according to NMR, which was used without
OP V3-tetr a a m in e (14). An oven-dried Schlenk flask was
charged with 12 (1.5 mmol, 0.66 g), N,N’-dimethyl-N-phenyl-
1,4-benzenediamine (3 mmol, 0.64 g), sodium tert-butoxide (3.6
mmol, 0.35 g), tris(dibenzylideneacetone)dipalladium(0) (1 mol
%, 13.8 mg), and (-)-(R)-N,N’-dimethyl-1-[(S)-2-(diphenylphos-
phino)ferrocenyl]ethylamine (3 mol %, 19.9 mg). After purging
with argon, dry toluene (3 mL) was added, and the reaction
mixture was heated at 80 °C for 5 days. The reaction mixture
was poured into water and extracted with dichloromethane
(3×). The combined organic layers were washed with water
and dried over MgSO4. The solvent was removed in vacuo
affording a brown thick oil which was purified by column
chromatography (50% CH2Cl2 in n-heptane) affording a yellow
1
further purification, mp: 125.4-128.5 °C. H NMR (CDCl3) δ
7.68 (m, 1H) 7.60-7.51 (m, 5H) 7.47-7.21 (m, 6H) 7.14-7.10
(m, 2H) 7.04 (d, J ) 16.5 Hz, 1H); 13C NMR (CDCl3) δ 139.47,
137.15, 137.02, 136.55, 136.35, 133.11, 130.99, 130.85, 130.44,
130.17, 129.65, 129.24, 128.85, 128.77, 128.70, 128.18, 127.71,
127.55, 127.23, 127.18, 127.03, 126.87, 126.65, 126.54, 125.20,
124.19, 122.92.
OP V2-tetr a a m in e (13). An oven-dried Schlenk flask was
charged with 1-(2-bromophenyl)-2-(3-bromophenyl)ethene 10
(2 mmol, 0.68 g), N,N’-dimethyl-N-phenyl-1,4-benzenediamine
(4 mmol, 0.85 g), sodium tert-butoxide (4.8 mmol, 0.46 g), tris-
(dibenzylideneacetone)dipalladium(0) (1 mol %, 18.3 mg), and
(-)-(R)-N,N’-dimethyl-1-[(S)-2-(diphenylphosphino)ferrocenyl]-
ethylamine (3 mol %, 26.5 mg). After purging with argon, dry
toluene (4 mL) was added, and the reaction mixture was
heated at 80 °C for 5 days. The reaction mixture was poured
into water and extracted with dichloromethane (3×). The
combined organic layers were washed with water and dried
over MgSO4. The solvent was removed in vacuo affording a
brown thick oil which was purified by column chromatography
(50% CH2Cl2 in n-heptane) affording a yellow wax (0.8 g,
67%): 1H NMR (CDCl3) δ 7.30-7.13 (m, 10H) 7.05-6.81 (m,
13H) 6.75-6.65 (m, 5H) 3.31 (s, 3H) 3.30 (s, 3H) 3.24 (s, 3H)
3.22 (s, 3H); 13C NMR (CDCl3) δ 149.60, 149.27, 146.95, 144.01,
143.54, 139.52, 139.51, 135.39, 130.12, 129.24, 129.09, 128.87,
128.80, 127.97, 126.46, 126.39, 126.14, 124.92, 123.51, 123.06,
120.05, 118.50, 117.87, 117.62, 117.54, 116.48, 115.24, 114.90,
40.35. Anal. Calcd for C42H40N4: C, 83.96; H, 6.71; N, 9.32.
Found: C, 83.85; H, 7.09; N, 8.94. Mass calcd: 600.81.
Found: 600.72.
1
solid (0.4 g, 38%) mp ) 171.7-173.8 °C; H NMR (CDCl3) δ
7.47 (q, J ) 12.8 Hz, 3H) 7.31-7.20 (m, 16H) 7.16-7.10 (m,
2H) 7.07-6.96 (m, 9H) 6.91-6.83 (m, 1H) 6.75-6.68 (m, 4H)
3.34 (s, 3H) 3.32 (s, 3H) 3.25 (s, 3H) 3.23 (s, 3H); 13C NMR
(CDCl3) δ 150.16, 149.94, 147.31, 147.08, 144.28, 143.84,
139.84, 138.46, 137.13, 137.07, 135.57, 129.57, 129.34, 129.22,
129.05, 128.35, 128.24, 127.15, 127.00, 126.66, 126.43, 125.09,
123.76, 123.32, 120.30, 118.78, 118.27, 117.95, 117.83, 116.54,
115.53, 115.16, 40.70, 40.61. Anal. Calcd for C50H46N4: C,
85.43; H, 6.60; N, 7.79. Found: C, 84.84; H, 6.99; N, 7.48. Mass
calcd: 702.94. Found: 702.73.
Ack n ow led gm en t. These investigations were sup-
ported by the Council for Chemical Sciences (CW) with
financial aid from The Netherlands Organization for
Scientific Research (NWO) together with the Technische
Universiteit Eindhoven in the PIONIER program.
J O000548O