Synthesis and self-assembly of dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium derivates

Article abstract of DOI:10.1016/j.tet.2008.08.063

A novel synthetic method toward nitrogen containing positively charged dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium (DBNT, 1) salts was developed. In this method, the undehydrogenated precursor of DBNT, 14-phenyl-14-dibenzo[a,j]acridinium salt (6), was produced directly from the reaction between 14-phenyl-14-dibenzo[a,j]xanthenylium (2) and amine/aniline in reasonable yield. Various DBNT salts with different alkyl and alkylphenyl chains were synthesized in this two-step method. The self-assembly behavior of two alkylated DBNT salts, 1c and 1f, was studied in this work. Due to the different substituents and counterions, compound 1c formed nanoscale wirelike fibers, and helical aggregates were obtained from 1f, in their methanolic solutions.

Full text of DOI:10.1016/j.tet.2008.08.063

Tetrahedron 64 (2008) 11379–11386
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and self-assembly of dibenzo[jk,mn]naphtho[2,1,8-fgh]
thebenidinium derivates
*
Dongqing Wu, Xinliang Feng, Masayoshi Takase, Monika C. Haberecht, Klaus Mu¨llen
Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 May 2008
Received in revised form 29 July 2008
Accepted 20 August 2008
Available online 27 August 2008
A novel synthetic method toward nitrogen containing positively charged dibenzo[jk,mn]naphtho[2,1,8-
fgh]thebenidinium (DBNT, 1) salts was developed. In this method, the undehydrogenated precursor of
DBNT, 14-phenyl-14-dibenzo[a,j]acridinium salt (6), was produced directly from the reaction between
14-phenyl-14-dibenzo[a,j]xanthenylium (2) and amine/aniline in reasonable yield. Various DBNT salts
with different alkyl and alkylphenyl chains were synthesized in this two-step method. The self-assembly
behavior of two alkylated DBNT salts, 1c and 1f, was studied in this work. Due to the different sub-
stituents and counterions, compound 1c formed nanoscale wirelike fibers, and helical aggregates were
obtained from 1f, in their methanolic solutions.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
DBNT derivatives were composed of hydrophilic aromatic core and
hydrophobic substituents (alkyl/alkylphenyl chains) as amphiphilic
In recent years, polycyclic aromatic hydrocarbons (PAHs) have
attracted great attention from physicists, chemists, and material
scientists due to the excellent electronic and optoelectronic prop-
erties, unique supramolecular behavior, and promising applications
in organic electronics.1–3 The incorporation of neutral nitrogen
atoms into the aromatic framework of PAHs, which can not only
influence their physical and chemical properties but also modify
their supramolecular behavior, is one of the most widely used
methods to obtain novel organic materials based on PAHs.4–11
However, research work on nitrogen containing positively charged
PAHs is still rare, mainly because of the synthetic difficulties.12–14
Dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium (DBNT, 1, Chart 1)
salts are so far the largest nitrogen containing positively charged
PAHs (including 27 conjugated carbon atoms). The reported syn-
thetic route toward the phenyl-substituted derivative, 14-phenyl-
DBNT hexafluorophosphate (1a), required multisteps with a total
yield of less than 5% (Scheme 1).14 Therefore, the development of
a versatile and efficient synthetic strategy toward different DBNT
derivates is urgently required in order to investigate their chemical/
physical properties and potential applications.
aromatic molecules. One-dimensional (1D) nanofibers were
obtained from these molecules simply by drop-casting their
methanolic solutions on silicon wafer, and the morphology of the
nanofibers exhibited obvious dependence on the alkyl chain length
and counterions of DBNTs.
2. Results and discussion
Compound 1a, which is the only DBNT salt reported so far, was
synthesized by A.C. Benniston and his co-workers very recently
(Scheme 1a).14 Adapted from the work previously reported by
W. Dilthey et al.,15,16 their synthetic procedure started with the con-
densation of N-phenyl-2-naphthylamine, benzaldehyde, and 2-
naphthol to produce 7,14-diphenyl-7,14-dihydrodibenzo[a,j]acridine
(4). The oxidation of 4 with MnO2 in the dark resulted in 7,14-
diphenyl-7,14-dihydrodibenzo[a,j]acridin-14-ol (5). Dehydration of 5
by HCl and subsequent ion exchange with potassium hexa-
fluorophosphate (KPF6) gave 7-phenyl-14-phenyl-dibenz[a,j]acridi-
nium hexafluorophosphate (6b). Final irradiation of the solution of 6b
with sunlight resulted in the dehydrogenated product 1a.
This synthetic route was obviously inefficient. First, the oxida-
tion of 5 had to be operated strictly in the dark because any ex-
posure to light caused a drastic decrease in the yield.14 On the other
hand, since the substituted phenyl group on the nitrogen atom of
1a was rigorously defined in the first step, it meant that any attempt
to change the substituted group had to start from different
2-naphthylamines at the beginning, where the synthesis was both
tedious and uneconomical. Accordingly, an alternative synthetic
Herein, we present a novel synthetic pathway to DBNT salts
starting from 14-phenyl-14-dibenzo[a,j]xanthenylium salts (2) as
the key building blocks. In this method, various DBNT derivates
with different alkyl or alkylphenyl substituents on their nitrogen
atoms (the 14-position of DBNT) were synthesized in two steps. The
* Corresponding author. Fax: þ49 6131 379 350.
E-mail address: muellen@mpip-mainz.mpg.de (K. Mu¨llen).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.08.063

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D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
A-
N+
R
A-
A-
N+
R
O+
DBNT 1
2
PQP 3
-
2a, A = BF4
2b, A = Br-.
;
3a R = C6H13, A = Cl;
3b R = C14H29, A = BF4.
1a R = phenyl, A = PF6;
1b R = phenyl, A = BF4;
1c R = C6H13, A = Br;
1d R = C12H25, A = BF4;
1e R = 4-hexylphenyl, A = BF4;
1f R = 4-tetradecylphenyl, A = BF4.
Chart 1. Dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium (DBNT, 1), 14-phenyl-14-dibenzo[a,j]xanthenylium salts (2), and 2-phenyl-benzo[8,9]quinolizino[4,5,6,7-fed]-phenan-
thridinylium (PQP, 3) salts.
(a)
OH
O
H
H
MnO2
Acetic acid
Acetic acid anhydride
20%
Refluxing
20%
N
NH
HO
N
5
4
sun light
98%
HCl
-H2O
45%
KPF6
quantitative
Cl-
N+
N+
N+
-
-
PF6
PF6
6a
1a
6b
(b)
Aniline
EtOH
Refluxing
N+
A-
A-
O+
nearly quantitative yields
7
8
Scheme 1. (a) Benniston’s method to 14-phenyl-dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium hexafluorophosphate (PDBNTPF6, 1a); (b) the synthetic pathway to PQP salts.
method was required to avoid these disadvantages and simplify
the synthetic protocols. In our previous study on the synthesis
of 2-phenyl-benzo[8,9]quinolizino[4,5,6,7-fed]phenanthridinylium
(PQP, 3) salts, various nitrogen containing 1,2,4,6-tetraphenylpyr-
idinium (8), which are the precursors of PQP salts, were obtained in
nearly quantitative yields by the simple reaction between oxygen
containing 2,4,6-triphenylpyrylium (7) and anilines (Scheme
1b).13,17 Therefore, in our opinion, compound 2 could be viewed as
the derivative of 7 with extended aromatic core. The same reaction
between 7 and aniline could be expected for 2 and thus undehy-
drogenated precursors 6 could be produced in a novel approach.
This meant that the synthesis of DBNT salts 1 could be greatly
simplified.
The most important building block in our method, compound 2
was synthesized by following a literature procedure (Scheme 2):
Claisen condensation between 2 equiv of 2-naphthol and 1 equiv of
benzaldehyde with concentrated hydrochloric acid as the catalyst
in glacial acetic acid resulted in 14-phenyl-14H-dibenzo[a,j]xan-
thene (9) in 60% yield.18 Compound 9 was then oxidized to 14-
phenyl-14-hydroxy-dibenzo[a,j]xanthene (10) by PbO2 in acetic
acid at 100 ꢀC (yield 95%). Subsequent treatment of 10 with in-
organic acids (HþAꢁ such as HBF4 and HBr) in acetic acid anhydride
and toluene at 0 ꢀC produced 2 as red powder in nearly quantitative
yields.19
In our work (Scheme 3), the reaction between 2 and aniline/
amine in anhydrous THF under argon atmosphere did give

D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
11381
compound 6 in moderate yields. As far as we know, the similar
conversion of xanthenylium to corresponding acridinium has so far
never been reported. In general, the reactions between xantheny-
lium salts and nucleophilic reagents mainly led to the addition
reactions on their C-9 position (the carbon atom on the para po-
sition of oxygen atom, Scheme 4a).20–22 The experimental results
were consistent with molecular-orbital calculations of xantheny-
lium derivates.23,24 In the case of 2, such addition products of ani-
line in reaction mixture could also be detected by FD MS
spectrometry (not shown). It was believed that the steric hindrance
on the 14-position of 2 reduced the amount of addition products
and enabled us to obtain 6 in reasonable yields.
Another side reaction, the addition between compound 2 and
protic solvents such as water, methanol, and ethanol could also
decrease the yield of 6 (Scheme 4b). Initially, ethanol was selected
as the solvent because it was the most common solvent for the
preparation of pyridinium salts from pyrylium salts.13,17 FD MS and
1H NMR spectra of the resulting reaction mixture (Fig. S1) indicated
that the main reaction was the addition of 2 with ethanol. In this
work, anhydrous tetrahydrofuran (THF) was chosen as the suitable
solvent to avoid this side reaction.
PbO2
AcOH
(b)
AcOH
HCl
(a)
H
O
O
9
OH
HO
Toluene
OH
Ac2O
H+A-
(c)
O+
2
O
10
A-
2a, A = BF4-;
2b, A = Br-.
Scheme 2. Synthetic pathway toward 14-phenyl-14-dibenzo[a,j]xanthenylium salts
(2). (a) Concentrated hydrochloric acid (catalyst), glacial acetic acid, 100 ꢀC, 6 h,
yield¼60%; (b) PbO2, acetic acid, 100 ꢀC, 2 h, yield¼95%; (c) inorganic acids in aqueous
solution, acetic acid anhydride and toluene (1:1), 0 ꢀC, ca. 30 min, quantitative yields.
NH2
R
Waterfree THF
Refluxing
N+
A-
R
O+
A-
Ar
2
6c R = phenyl, A = BF4, 35%;
6d R = C6H13, A = Br, 24%;
6e R = C12H25, A = BF4, 19%;
6f R = 4-hexylphenyl, A = BF4, 22%;
6g R = 4-tetradecylphenyl, A = BF4, 17%.
hv
300 nm
N+
R
1b-f
A-
Scheme 3. Novel synthetic pathway toward DBNT salt 1. (a) Aniline/amine (1 equiv), anhydrous THF, argon bubbling, refluxing, ca. 6 h; (b) ethanol, rt, h
69% (1c), 48% (1d), 67% (1e), and 43% (1f).
n, ca. 24 h, yield¼80% (1b),
Nu
(a)
Nu
C+
O+
A-
A-
O
O
(b)
NH
C
H2N
O
C+
O
Et
O
A-
H
A-
O+
2
OEt
C
O
Scheme 4. (a) The literature reported reaction between xanthenylium derivates and nucleophilic reagents; (b) the side reaction of 2 and aniline and ethanol.

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D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
A mechanism for the formation of dibenzo[a,j]acridinium 6 from
(Fig. 1a) was dominated by a strong band located at 305 nm
(log
¼4.88) followed by two weak absorption bands at longer
wavelength region (348 nm, log ¼4.00).
¼4.43 and 430 nm, log
Compared with 3b, compound 1f showed similar absorption bands
in which the first main band was at 328 nm (log
¼4.79), and the
other two low energy bands were located at 416 (log
¼4.34), and
507 nm (log
cules exhibited structureless emission peaks in their fluorescence
spectra. Remarkably, the emission maximum at 535 nm for 1f was
red-shifted by 69 nm compared with 3b (466 nm). The obvious
dibenzo[a,j]xanthenylium 2 is proposed herein. As shown in
Scheme 5, the reaction might experience a nucleophilic C-2 open-
ing/recyclization.25 During that process, the first C-2 addition be-
tween 2 and aniline led to the ring-opening product 12. Subsequent
intramolecular aldol condensation of 12 produced intermediate 13,
and the further dehydration reaction of the latter compound
resulted in the recyclized product 6.
3
3
3
3
3
3
¼4.63), respectively. On the other hand, both mole-
As shown in Scheme 3, the final photocyclization of precursors 6
in ethanol under 300 nm UV light and further recrystallization of
+
-
H
O+
-
BF4
O
O
HN
NH
H
H
NH
11
12
-H2O
N+
-
N+
BF4
HO
H
6c
13
Scheme 5. One possible synthetic mechanism of dibenzo[a,j]acridinium 6c.
the precipitates produced the corresponding DBNT salts 1 with
difference of the absorbance and fluorescence spectra indicated
a strong influence of the extension of the size of aromatic core on
their photophysical properties, which was similar to other ex-
tended PAHs.26,27
various alkyl and alkylphenyl chains. All molecules were charac-
terized by 1H and 13C NMR spectroscopies, MALDI-TOF mass
spectrometry as well as elemental analysis (Section 4).
2.1. UV–vis absorption and fluorescence spectra of DBNT salts
2.2. Self-assembly of DBNT salts
In the interest of understanding the effect of shape and size of
the aromatic core on the physical properties of nitrogen containing
positively charged PAHs, the UV–vis absorption and fluorescence
spectra of PQP 3b and DBNT 1f in methanol were recorded and
compared in Figure 1. The absorption spectrum of compound 3b
Recently, we investigated the self-assembly behavior of alky-
lated PQP derivates in solution and obtained nanoscale aggregates
with different morphologies such as fibers and tubes by using PQP
salts with different alkyl chains and counterions.17 In order to
obtain a better understanding of the relationship between the
(a)
(b)
1f
1f
12000
3b
466
3b
535
305
10000
8000
6000
4000
2000
0
328
50000
507
348
416
430
0
300
350
400
Wave length (nm)
450
500
550
600
400
600
Wave length (nm)
Figure 1. The UV–vis absorption (a) and fluorescence (b) spectra of the different nitrogen containing positively charged PAHs: 3b (red) and 1f (blue).

D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
11383
aggregation of nitrogen containing positively charged PAHs and the
1c
1f
001
size of their aromatic cores, the self-assembly behavior of DBNT
salts 1c and 1f in solution was studied in a similar manner.
The morphology of the aggregates from these two DBNT salts
was first investigated by scanning electron microscopy (SEM) after
drop-casting their methanolic solutions on silicon wafers. As
shown in Figure 2a and b, compound 1c formed fibrous aggregates
and the diameters of these wirelike fibers ranged from 150 to
200 nm, which was similar to the aggregates of PQP salt with hexyl
chain and chloride as anion (compound 3a). In the case of com-
pound 1f with longer alkyl chain and larger anion, aggregates with
fibrous structures were also obtained. It was interesting to note that
their diameters were about 50 nm and they contained helical
structures (Fig. 2c and d). Such helical structures were also ob-
served for PQP salt with tetradecyl chain and tetrafluoroborate as
anion (compound 3b).17
The different morphology of aggregates from the two com-
pounds implied that DBNT salts with different alkyl/alkylphenyl
chains might adopt different packing models, which was similar to
previous descriptions for PQP salts with different alkyl chains.
Subsequent wide angle X-ray scattering (WAXS) measurements of
the dry powder of 1c and 1f from their methanolic solution con-
firmed this hypothesis. As shown in Figure 3, the characteristic
reflections of lamellar stacking (d spacings¼40.1, 19.6, and 13.2 Å)
appeared in the WAXS patterns of compound 1f, whereas such
diffraction peaks could not be observed in the patterns of 1c.
1000
002
003
0.34 nm
0.34 nm
100
5
10
15
(degree)
20
25
30
2
Figure 3. WAXS patterns of the dried powder of 1c and 1f obtained from their
methanolic solutions.
Therefore, the morphology change of the aggregates formed by 1c
and 1f could be explained by the packing parameter theory brought
forward by Israelachivili.28–32 This theory proposed that the mor-
phology formed by an amphiphilic molecule was dependent upon
its packing parameter, P¼v/(a0lc), where v was the volume of the
Figure 2. (a) and (b) SEM image of the aggregates formed by 1c; and (c) and (d) SEM image of the aggregates formed by 1f (1ꢂ10ꢁ3 mol/L in methanol, drop-cast on a silicon wafer).

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D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
Figure 4. The schematic representation of the self-assembly of 1c and 1f.
hydrophobic chain, a0 was the surface area of the hydrophobic core
of the aggregate expressed per molecule in the aggregate (hereafter
referred to as the area per molecule), and lc was the chain length. If
P<1/3, spherical and ellipsoidal aggregates were favored mor-
phologies; if 1/3<P<1/2, the amphiphile tended to form cylindrical
rods; if 1/2<Pꢃ1, bilayer structures such as vesicles, tubes and
lamellae were preferred. In the case of these two DBNT salts, the
wirelike fibers of 1c indicated that the packing parameter P of 1c
was between 1/3 and 1/2. With the increase of alkyl chain length,
the change of intramolecular interactions such as solvophobic ef-
fects caused lower interaction free energies and a smaller optimal
surface area per molecule a0. As a result, the packing parameter P of
1f increased with respect to 1c and the lamellar aggregates formed
accordingly (Fig. 4).17,33
4. Experiment part
4.1. General information
All starting materials were obtained from commercial suppliers
such as Aldrich, Acros, and Fluka and used as received unless oth-
erwise specified. Irradiations with an external UV source were per-
formed with a Rayonet reactor (RPR-200) with 3000 Å lamps in
quartz flasks. 1H and 13C NMR spectra were recorded on Bruker DPX
250 spectrometer with use of the solvent proton or carbon signal as
an internal standard. FD mass spectra were obtained on a VG In-
struments ZAB 2-SE-FPD spectrometer. MALDI-TOF mass spectra
were measured using a Bruker Reflex II-TOF spectrometer using
a 337 nm nitrogen laser and 7,7,8,8-tetracyanoquinodimethane
On the other hand, the helically coiled shapes of the fibers from
1f might be caused by the tetrafluoroborate anion as PQP salt 3b.
Such a large anion might disrupt the face-to-face alignment of
adjacent molecules, causing them to adopt a slipped orientation.
Consequently, neighboring pairs of 1f were rotated with respect to
one another along the axis of the aggregate and a helical aggregate
resulted (Fig. 4).17,34
Obviously, the similarity in the morphology of aggregates from
PQP and DBNT salts indicated that both kinds of nitrogen con-
taining positively charged PAHs had similar self-assembly behavior
despite the different size of their aromatic cores. Combining this
with the self-assembly behavior of PQP, it was assumed that the
governing effects on the morphology of the aggregates from the
nitrogen containing positively charged PAHs were the length of
their alkyl chains and the size of their counterions.17,33–35
(TCNQ) as matrix. A double graphite monochromator for the Cu K
a
radiation (
l¼0.154 nm) was used for the WAXS experiments. SEM
measurements were performed on a LEO 1530 field emission scan-
ning electron microscope. The elemental analysis was measured in
Institut fu¨r Organische Chemie der Johannes Gutenberg-Universita¨t
Mainz for: C, N, H: Foss Heraeus vario EL. UV–vis spectra were
recorded at room temperature on a Perkin–Elmer Lambda 9 spec-
trophotometer. Fluorescence spectra were recorded on a SPEX-Flu-
orolog II (212) spectrometer.
4.2. Synthesis
4.2.1. 14-Phenyl-14H-dibenzo[a,j]xanthene (9)
To a solution of benzaldehyde (50 mmol) and 2-naphthol
(100 mmol) in glacial acetic acid (40 mL), concentrated HCl (1 mL)
was added dropwise. The solution was heated with oil bath to
100 ꢀC and kept at this temperature until crystallization took place.
When the solution was cooled to room temperature, the pre-
cipitated product was filtered with suction and recrystallized from
glacial acetic acid to give the target compound 9.
3. Conclusion
In summary, we have developed a novel synthetic approach
toward nitrogen containing DBNT salts. In this method, the unde-
hydrogenated precursors, dibenzo[a,j]acridinium salts 6, were
produced directly from the reaction between dibenzo[a,j]xanthe-
nylium derivates 2 and amine/aniline in reasonable yields. There-
fore, various DBNT salts with different substituents were
successfully synthesized in this two-step method. By drop-casting
their methanolic solutions on silicon wafers, two DBNT salts, 1c and
1f, with different alkyl and alkylphenyl chains formed one-di-
mension nanoscaled fibers with relatively different morphologies.
The former compound with a hexyl chain aggregated into wirelike
fibers, whereas the self-assembly of the latter with a tetradecyl-
phenyl chain produced helical aggregates. The difference in their
morphology is due to their different hydrophobic substituents and
counterions. These ordered aggregates are expected to be useful as
ionic conducting materials36,37 and the study of their electronic
properties is underway in our lab now.
White needles (yield¼60%), 1H NMR (250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼8.33–8.29 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 7.77–7.71 (t,
4H, 3J(H,H)¼7.5 Hz, aromatic), 7.53–7.30 (m, 8H, aromatic), 7.10–7.04
(t, 2H, 3J(H,H)¼7.5 Hz, aromatic), 6.95–6.89 (t, 1H, 3J(H,H)¼7.5 Hz,
13
aromatic), 6.42 (s, 1H, CH); C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼148.40, 145.04, 131.10, 130.89, 128.73, 128.62, 128.28,
128.03, 126.63, 126.28, 124.14, 122.43, 117.77, 116.96, 37.83.
FD MS (MW¼358.44): m/z: 358.67.
Elemental analysis: calcd C 90.47%, H 5.06%, O 4.66%; found: C
90.35%, H 5.12%.
4.2.2. 14-Phenyl-14H-dibenzo[a,j]xanthen-14-ol (10)
Compound 9 (5.6 mmol) and lead dioxide (PbO2, 2 g; 8.4 mmol)
in glacial acetic acid (50 mL) were stirred while heating on an oil
bath at 120 ꢀC for 3 h. The cooled mixture was poured onto crushed

D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
11385
13
ice and the solid residue was recrystallized from aqueous acetone
CH2), 0.81–0.77 (m, 3H, CH3); C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
to give 10.
d
(ppm)¼143.45, 141.20, 140.71, 139.10, 133.06, 132.37, 132.02,
1
White powder (yield¼95%), H NMR (250 MHz, CD2Cl2, 25 ꢀC):
132.98, 131.25, 130.50, 129.71, 129.60, 127.93, 31.52, 29.54, 27.34,
22.77, 14.11.
d
(ppm)¼8.95–8.91 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 7.76–7.72 (d,
2H, 3J(H,H)¼10.0 Hz, aromatic), 7.69–7.62 (m, 4H, aromatic), 7.35–7.31
(d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 7.29–7.22 (m, 4H, aromatic), 7.11–
7.05(t, 2H, 3J(H,H)¼7.5 Hz, aromatic), 6.93–6.87(t,1H, 3J(H,H)¼7.5 Hz,
MALDI-TOF-MS (MW¼440.24 without anion): m/z: 440.30.
4.2.4.3. 7-Dodecyl-14-phenyldibenzo[a,j]acridinium tetrafluoroborate
13
aromatic), 3.12 (s, 1H, OH); C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
(6e). Golden yellow powder (yield¼19%), 1H NMR (250 MHz,
d
(ppm)¼132.57, 131.80, 131.70, 129.89, 129.49, 128.17, 127.94, 127.73,
CD2Cl2, 25 ꢀC):
d
(ppm)¼8.45–8.41 (d, 2H, 3J(H,H)¼10.0 Hz, aro-
127.53, 127.41, 126.94, 126.86, 125.93, 124.89, 124.81, 118.31.
matic), 8.15–8.11 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.07–8.00 (m,
3H, aromatic), 7.94–7.76 (m, 7H, aromatic), 7.62–7.41 (m, 3H, aro-
matic), 5.09–5.05 (t, 2H, 3J(H,H)¼5.0 Hz, CH2), 3.12–3.08 (m, 2H,
CH2), 1.50–1.11 (m, 18H, CH2), 0.82–0.78 (m, 3H, CH3); 13C NMR
MALDI-TOF-MS (MW¼374.13): m/z: 374.21.
4.2.3. Dehydration of xanthene-ol (synthesis of 2a and 2b)
Compound 10 (5 mmol) in acetic anhydride (15 mL) and toluene
(5 mL) were cooled and treated with inorganic acid (ca. 25 mmol)
until no further precipitation occurred. The cooled solution was
filtered and washed with anhydrous ether to yield 2 as product.
(62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼143.25, 141.00, 140.53, 138.97,
132.96, 132.27, 131.89, 132.78, 131.07, 130.32, 129.55, 129.45, 127.73,
32.82, 31.75, 31.23, 30.34, 29.54, 27.34, 25.08, 22.77, 14.11.
MALDI-TOF-MS (MW¼524.33 without anion): m/z: 524.45.
4.2.3.1. 14-Phenyl-14-dibenzo[a,j]xanthenylium
tetrafluoroborate
4.2.4.4. 14-Phenyl-7-(4-hexylphenyl)dibenzo[a,j]acridinium
tetra-
(2a). Dark red crystals with a golden glimmer (yield¼92%), 1H NMR
fluoroborate (6f). Golden yellow powder (yield¼22%), 1H NMR
(250 MHz, CD2Cl2,25 ꢀC):
d
(ppm)¼8.78–8.74 (d, 2H, "pre">3J(H,H)¼10.0 Hz,
(250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼8.44–8.40 (d, 2H,
aromatic), 8.25–8.21 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.16–8.12 (d, 2H,
3J(H,H)¼10.0 Hz, aromatic), 7.91–7.81 (m, 3H, aromatic), 7.75–7.69 (t,
2H 3J(H,H)¼7.5 Hz, aromatic), 7.48–7.36 (m, 4H, aromatic), 7.17–7.14 (d, 2H,
3J(H,H)¼7.5 Hz, aromatic); 13C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
3J(H,H)¼10.0 Hz, aromatic), 8.13–8.09 (d, 2H, 3J(H,H)¼10.0 Hz, ar-
omatic), 7.94–7.92 (m, 3H, aromatic), 7.90–7.62 (m, 7H, aromatic),
7.55–7.30 (m, 7H, aromatic), 2.97–2.91 (t, 2H, CH2), 1.91–1.78 (m,
2H, CH2), 1.46–1.31 (m, 6H, CH2), 0.95–0.98 (m, 3H, CH3); 13C NMR
d
(ppm)¼167.30, 159.95, 147.70, 138.67, 133.20, 132.73, 132.40, 132.10,
(62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼143.05, 140.87, 140.35, 138.80,
130.90, 130.08, 129.43, 128.60, 126.73, 122.56, 117.72.
132.68, 131.99, 131.68, 131.70, 131.01, 130.10, 129.38, 129.70, 129.12,
128.97, 128.35, 127.97, 125.15, 35.44, 31.87, 31.08, 28.52, 22.94, 14.19.
MALDI-TOF-MS (MW¼516.27 without anion): m/z: 516.35.
MALDI-TOF-MS (MW¼357.13 without anion): m/z: 357.20.
4.2.3.2. 14-Phenyl-14-dibenzo[a,j]xanthenylium bromide (2b). Dark
red crystals with a golden glimmer (yield¼95%), 1H NMR (250 MHz,
4.2.4.5. 14-Phenyl-7-(4-tetradecylphenyl)dibenzo[a,j]acridinium tetra-
CD2Cl2, 25 ꢀC):
d
(ppm)¼8.75–8.71 (d, 2H, 3J(H,H)¼10.0 Hz, aro-
fluoroborate (6g). Golden yellow powder (yield¼17%), 1H NMR
matic), 8.21–8.17 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.13–8.10 (d,
2H, 3J(H,H)¼7.5 Hz, aromatic), 7.90–7.82 (m, 3H, aromatic), 7.74–
7.68 (t, 2H, 3J(H,H)¼7.5 Hz, aromatic), 7.46–7.35 (m, 4H, aromatic),
7.16–7.12 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic); 13C NMR (62.5 MHz,
(250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼8.43–8.39 (d, 2H,
3J(H,H)¼10.0 Hz, aromatic), 8.12–8.08 (d, 2H, 3J(H,H)¼10.0 Hz, ar-
omatic), 7.93–7.91 (m, 3H, aromatic), 7.89–7.61 (m, 7H, aromatic),
7.54–7.29 (m, 7H, aromatic), 2.96–2.91 (t, 2H, CH2), 1.91–1.78 (m,
2H, CH2), 1.46–1.16 (m, 22H, CH2), 0.88–0.85 (m, 3H, CH3); 13C
CD2Cl2, 25 ꢀC):
d
(ppm)¼167.51,159.90,147.64,138.61,133.15,132.73,
132.40, 132.06, 130.91, 130.08, 129.41, 128.59, 126.67, 122.55, 117.60.
NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
138.81, 132.66, 131.97, 131.66, 131.68, 130.92, 130.05, 129.32,
129.68, 129.10, 128.95, 128.33, 127.92, 125.10, 36.05, 33.11, 32.11,
30.85, 30.56, 29.62, 23.79, 14.49.
d
(ppm)¼143.06, 140.85, 140.37,
MALDI-TOF-MS (MW¼357.13 without anion): m/z: 357.18.
4.2.4. 7,14-Diphenyldibenzo[a,j]acridinium derivates
All the aniline/amine were dried according to handbook pro-
cedure before use. Compound 2 (2 mmol) and appropriate aniline/
amine (2.2 mmol) were added to 15 mL anhydrous THF. The mix-
ture was refluxed for 5 h till the solution turned transparent. After
cooling the solution to room temperature, it was concentrated in
vacuo to ca. 3 mL. Then the concentrated solution was poured into
400 mL hexane. After filtration, the solid was recrystallized from
20 mL hexane to give the target compound 6.
MALDI-TOF-MS (MW¼628.39 without anion): m/z: 628.51.
4.2.5. Photocyclization
1 mmol 6 was dissolved in 200 mL absolute ethanol. The etha-
nolic solution was irradiated with 300 nm UV lamp. After 72 h, the
solid product was filtered off. The resulted solid was recrystallized
in ethanol to give the DBNT salts 1.
4.2.5.1. 14-Phenyl-dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium
4.2.4.1. 7,14-Diphenyldibenzo[a,j]acridinium tetrafluoroborate (6c).
Golden yellow needles (yield¼35%), 1H NMR (250 MHz, CD2Cl2,
tetrafluoroborate (1b). Golden red needles (yield¼85%), 1H NMR
(250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼9.35–9.32 (d, 2H,
25 ꢀC):
d
(ppm)¼8.50–8.46 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic),
3J(H,H)¼7.5 Hz, aromatic), 9.18–9.15 (d, 2H, 3J(H,H)¼7.5 Hz, aro-
matic), 8.82–8.78 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.68–8.65 (d,
2H, 3J(H,H)¼7.5 Hz, aromatic), 8.40–8.34 (t, 3H, 3J(H,H)¼7.5 Hz,
aromatic), 8.08–8.06 (t, 3H, 3J(H,H)¼2.5 Hz, aromatic), 7.88–7.84
(m, 4H, aromatic); 13C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
8.20–8.16 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.05–8.03 (m, 3H,
aromatic), 8.00–7.76 (m, 7H, aromatic), 7.67–7.40 (m, 8H, aro-
13
matic); C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼143.00,
140.81, 140.29, 138.72, 132.61, 131.93, 131.62, 131.58, 130.95, 130.04,
129.30, 129.23, 129.02, 128.91, 128.25, 127.93, 125.10.
d
(ppm)¼148.50, 140.49, 139.55, 133.92, 133.41, 132.13, 131.65,
MALDI-TOF-MS (MW¼432.17 without anion): m/z: 432.26.
130.19, 130.15, 129.89, 128.14, 127.09, 124.18, 122.59, 118.66, 117.17.
MALDI-TOF-MS (MW¼428.14 without anion): m/z: 428.21.
Elemental analysis: calcd C 76.92%, H 3.52%, B 2.10%, F 14.25%, N
2.72%; found: C 76.95%, H 3.72%, N 2.61%.
4.2.4.2. 7-Hexyl-14-phenyldibenzo[a,j]acridinium bromide (6d).
Golden yellow powder (yield¼24%), 1H NMR (250 MHz, CD2Cl2,
25 ꢀC):
d
(ppm)¼8.41–8.37 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.11–
8.07 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.00–7.95 (m, 3H, aromatic),
7.89–7.66 (m, 7H, aromatic), 7.58–7.36 (m, 3H, aromatic), 5.07–5.03
(t, 2H, 3J(H,H)¼5.0 Hz, CH2), 3.11–3.07 (m, 2H, CH2),1.47–1.12 (m, 6H,
4.2.5.2. 14-Hexyl-dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium
bromide (1c). Golden red powder (yield¼69%), 1H NMR (250 MHz,
CD2Cl2, 25 ꢀC):
d
(ppm)¼8.49–8.46 (d, 2H, 3J(H,H)¼7.5 Hz,

11386
D. Wu et al. / Tetrahedron 64 (2008) 11379–11386
aromatic), 8.27–8.24 (d, 2H, 3J(H,H)¼7.5 Hz, aromatic), 8.16–8.09
(m, 4H, aromatic), 7.79–7.73 (m, 6H, aromatic), 7.36–7.32 (m, 1H,
3J(H,H)¼5.0 Hz, aromatic), 5.16–5.12 (t, 2H, 3J(H,H)¼5.0 Hz, CH2),
3.15–3.10 (m, 2H, CH2), 1.50–1.18 (m, 6H, CH2), 0.83–0.80 (m, 3H,
Elemental analysis: calcd C 79.32%, H 6.51%, B 1.52%, F 10.68%, N
1.97%; found: C 79.72%, H 6.22%, N 1.95%.
Acknowledgements
CH3); 13C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼142.60, 139.89,
138.15, 137.31, 133.78, 131.11, 129.56, 128.55, 126.13, 122.88, 120.99,
116.59,113.44,110.75,104.62, 32.31, 30.03, 29.97, 29.74, 23.07,14.26.
MALDI-TOF-MS (MW¼428.14 without anion): m/z: 428.21.
Elemental analysis: calcd C 76.74%, H 5.07%, Br 15.47%, N 2.71%;
found: C 77.24%, H 4.53%, N 2.49%.
This work was financially supported by the Max Planck Society
through the program ENERCHEM, the German Science Foundation
(Korean-German IRTG), and DFG Priority Program SPP 1355.
Supplementary data
4.2.5.3. 14-Dodecyl-dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2008.08.063.
tetrafluoroborate (1d). Golden red powder (yield¼48%), 1H NMR
(250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼8.46–8.43 (d, 2H,
3J(H,H)¼7.5 Hz, aromatic), 8.24–8.21 (d, 2H, 3J(H,H)¼7.5 Hz, aro-
matic), 8.13–8.04 (m, 4H, aromatic), 7.79–7.73 (m, 6H, aromatic),
7.33–7.29 (m, 1H, 3J(H,H)¼5.0 Hz, aromatic), 5.14–5.10 (t, 2H,
3J(H,H)¼5.0 Hz, CH2), 2.04–2.02 (m, 2H, CH2), 1.76–1.71 (m, 2H,
CH2), 1.48–1.32 (m, 18H, CH2), 0.81–0.79 (m, 3H, CH3); 13C NMR
References and notes
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(62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼142.51, 139.80, 138.06, 137.22,
133.70, 131.03, 129.48, 128.45, 126.04, 122.79, 120.91, 116.50, 113.35,
110.66, 104.53, 32.28, 31.36, 30.23, 29.85, 29.64, 29.29, 22.62, 14.31.
MALDI-TOF-MS (MW¼520.30 without anion): m/z: 520.11.
Elemental analysis: calcd C 77.10%, H 6.30%, B 1.78%, F 12.51%, N
2.31%; found: C 77.29%, H 6.11%, N 2.53%.
4.2.5.4. 14-(4-Hexylphenyl)-dibenzo[jk,mn]naphtho[2,1,8-fgh]thebe-
nidinium tetrafluoroborate (1e). Golden red powder (yield¼67%),
1H NMR (250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼9.41–9.38 (d, 2H,
3J(H,H)¼7.5 Hz, aromatic), 9.29–9.26 (d, 2H, 3J(H,H)¼7.5 Hz, aro-
matic), 8.74–8.70 (d, 2H, 3J(H,H)¼10.0 Hz, aromatic), 8.61–8.59 (d,
2H, 3J(H,H)¼7.5 Hz, aromatic), 8.53–8.47 (t, 1H, 3J(H,H)¼7.5 Hz, aro-
matic), 8.42–8.36 (t, 2H, 3J(H,H)¼7.5 Hz, aromatic), 7.85–7.74 (m,
4H, aromatic), 7.55–7.52 (d, 2H, 3J(H,H)¼7.5 Hz, aromatic); 2.94–
2.88 (t, 2H, 3J(H,H)¼7.5 Hz, CH2), 1.84–1.76 (m, 2H, CH2), 1.46–1.35
(m, 6H, CH2), 0.94–0.89 (m, 3H, CH3); 13C NMR (62.5 MHz, CD2Cl2,
25 ꢀC):
d
(ppm)¼148.41, 140.40, 139.51, 133.89, 133.36, 132.09,
131.61, 130.15, 130.11, 129.86, 128.09, 127.07, 124.10, 122.53, 118.59,
117.11, 36.27, 32.13, 31.74, 29.48, 23.05, 14.29.
18. Claisen, L. Ber. Dtsch. Chem. Ges. 1887, 20, 665.
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25. Gilchrist, T. L. Heterocyclic Chemistry, 3rd ed.; Prentice Hall: New Jersey, NJ, 1997.
26. Kastler, M.; Schmidt, J.; Pisula, W.; Sebastiani, D.; Mu¨ llen, K. J. Am. Chem. Soc.
2006, 128, 9526.
27. Yang, X. Y.; Dou, X.; Rouhanipour, A.; Zhi, L. J.; Rader, H. J.; Mu¨llen, K. J. Am.
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MALDI-TOF-MS (MW¼512.24 without anion): m/z: 512.22.
Elemental analysis: calcd C 78.14%, H 5.04%, B 1.80%, F 12.68%, N
2.34%; found: C 77.94%, H 4.83%, N 2.25%.
4.2.5.5. 14-(4-Tetradecylphenyl)-dibenzo[jk,mn]naphtho[2,1,8-fgh]-
thebenidinium tetrafluoroborate (1f). Golden
red
powder
1
(yield¼43%), H NMR (250 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼9.05–
9.01 (d, 2H, 3J(H,H)¼7.5 Hz, aromatic), 8.84–8.81 (d, 2H,
3J(H,H)¼7.5 Hz, aromatic), 8.69–8.65 (d, 2H, 3J(H,H)¼10.0 Hz, ar-
omatic), 8.52–8.49 (d, 2H, 3J(H,H)¼7.5 Hz, aromatic), 8.26–8.20
(t, 1H, 3J(H,H)¼7.5 Hz, aromatic), 8.17–8.11 (t, 2H, 3J(H,H)¼7.5 Hz,
aromatic), 7.84–7.78 (m, 4H, aromatic), 7.59–7.55 (d, 2H,
3J(H,H)¼10.0 Hz, aromatic), 2.99–2.93 (t, 2H, 3J(H,H)¼7.5 Hz,
CH2), 1.91–1.85 (m, 2H, CH2), 1.54–1.21 (m, 22H, CH2), 0.85–0.83
(m, 3H, CH3); 13C NMR (62.5 MHz, CD2Cl2, 25 ꢀC):
d
(ppm)¼148.70, 140.69, 139.78, 134.18, 133.55, 132.33, 131.81,
130.40, 130.60, 130.08, 128.33, 127.38, 124.39, 122.81, 118.92,
117.41, 37.11, 33.15, 32.73, 30.92, 30.70, 30.65, 29.88, 22.98, 14.55.
MALDI-TOF-MS (MW¼624.36 without anion): m/z: 624.42.