Heterocyclic quinol-type fluorophores. Part 9: Effect of forming a continuous intermolecular hydrogen bonding chain between fluorophores on the solid-state fluorescence properties

Article abstract of DOI:10.1016/j.tet.2010.08.026

Three heterocyclic quinol-type fluorophores with benzo[c]carbazol-6-one skeleton or benzo[b]naphtho[1,2-d]furan-6-one skeleton, 9-dibutylamino-5- hydroxy-5-phenyl-5,7-dihydro-benzo[c]carbazol-6-one (5a), 7-butyl-9- dibutylamino-5-hydroxy-5-phenyl-5,7-dihydro-benzo[c]carbazol-6-one (5b) and 9-dibutylamino-5-hydroxy-5-phenyl-5H-benzo[b]naphtho[1,2-d]furan-6-one (6c) have been synthesized and their photophysical properties have been investigated in solution and in the solid state. The fluorescence quantum yield (Φ) increases in the order of 5b (0.35)<5a (0.41)< 6c (0.74) in 1,4-dioxane. On the other hand, the Φ value in the solid state increases in the order of 5a<<6C (0.03)<5b (0.07), which are much smaller than those in 1,4-dioxane. To elucidate the effects of molecular and crystal structures on the solid-state fluorescence properties, we have performed the semi-empirical molecular orbital calculations (AM1 and INDO/S) and X-ray crystallographic analysis. It was found that the formation of a continuous intermolecular hydrogen bonding between adjacent fluorophores is observed in the crystal of 5a, which is considered to cause a drastic fluorescence quenching in the solid state.

Full text of DOI:10.1016/j.tet.2010.08.026

Tetrahedron 66 (2010) 7954e7960
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Heterocyclic quinol-type fluorophores. Part 9: Effect of forming a continuous
intermolecular hydrogen bonding chain between fluorophores on the
solid-state fluorescence propertiesq
*
*
Yousuke Ooyama , Saori Nabeshima, Toshiki Mamura, Haruka Egawa Ooyama, Katsuhira Yoshida
Department of Material Science, Faculty of Science, Kochi University, Akebono-cho, Kochi 780-8520, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 July 2010
Received in revised form 7 August 2010
Accepted 10 August 2010
Available online 14 August 2010
Three heterocyclic quinol-type fluorophores with benzo[c]carbazol-6-one skeleton or benzo[b]naphtho
[1,2-d]furan-6-one skeleton, 9-dibutylamino-5-hydroxy-5-phenyl-5,7-dihydro-benzo[c]carbazol-6-one
(5a), 7-butyl-9-dibutylamino-5-hydroxy-5-phenyl-5,7-dihydro-benzo[c]carbazol-6-one (5b) and 9-di-
butylamino-5-hydroxy-5-phenyl-5H-benzo[b]naphtho[1,2-d]furan-6-one (6c) have been synthesized
and their photophysical properties have been investigated in solution and in the solid state. The fluo-
rescence quantum yield (F) increases in the order of 5b (0.35)<5a (0.41)<6c (0.74) in 1,4-dioxane. On the
other hand, the value in the solid state increases in the order of 5a<<6C (0.03)<5b (0.07), which are
F
much smaller than those in 1,4-dioxane. To elucidate the effects of molecular and crystal structures on
the solid-state fluorescence properties, we have performed the semi-empirical molecular orbital calcu-
lations (AM1 and INDO/S) and X-ray crystallographic analysis. It was found that the formation of
a continuous intermolecular hydrogen bonding between adjacent fluorophores is observed in the crystal
of 5a, which is considered to cause a drastic fluorescence quenching in the solid state.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
solid-state emissive fluorophores is to reduce the intermolecular
interactions between fluorophores leading to fluorescence
Solid-state organic fluorescent dyes have received considerable
attention because of not only for fundamental use in the research of
solid-state photochemistry,1 but also for practical use in the organic
light emitting diode (OLED)2 and optical sensor3 fields. Although
there are many dyes exhibiting strong fluorescence in solution, the
number of fluorescent dyes exhibiting intense fluorescence in the
solid state is relatively limited because most organic fluorophores
undergo fluorescence quenching in aggregation state. The solid-
state fluorescence properties are closely associated with the
molecular packing structure, and many researches have been
conducted on the correlation between the solid-state fluorescence
properties and the molecular packing structures on the basis of the
X-ray crystal structures. It has been revealed that strong
quenching in molecular aggregation states. For example, the in-
troduction of bulky substituents to the original fluorophores and
the construction of a non-planar structure with sterical hindered
substituents are known to be very useful methods for solving the
problem of fluorescence quenching by aggregation.5,6 Akkaya et al.
have recently reported solid-state emissive BODIPY dyes with
bulky substituents as spacers; introduction of bulky tert-butyl
substituents on the meso-phenyl groups result in more spaced
packing in the solid-state, leading to highly luminescent powders
and films.7 On the other hand, Tang et al. have discovered a very
interesting solid-state fluorescence system that a series of silole
molecules were found to be non-luminescent in the solution state
but emissive in the aggregated state. They coined the term ‘ag-
gregation-induced emission (AIE)’ for this novel phenomenon and
identified restriction of intramolecular rotation leading to non-ra-
diative decay in the aggregates as a main cause for the AIE effect.8
Thus, in order to control perfectly the solid-state fluorescence
properties of organic fluorophores, it is necessary to obtain further
useful information about the effect of molecular and crystal
structures on the solid-state fluorescence properties.
intermolecular interactions, such as
pep interaction and in-
termolecular hydrogen bonding between neighboring fluorophores
are principal factors of fluorescence quenching in the solid
state.1d,3,4 Consequently, the key point in designing the new strong
q
For part 8 in the series, see Ref. 6e.
In our previous study, we have reported the synthesis of novel
heterocyclic quinols, 5-hydroxy-5-substituent-benzo[b]naphtho
[1,2-d]furan-6-one fluorophores (6aec) with substituents (R¼Me,
* Corresponding authors. Tel.: þ81 88 844 8296; fax: þ81 88 844 8359.; e-mail
addresses: yooyama@hiroshima-u.ac.jp (Y. Ooyama), kyoshida@cc.kochi-u.ac.jp
(K. Yoshida).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.08.026

Y. Ooyama et al. / Tetrahedron 66 (2010) 7954e7960
7955
Bu and Ph) of non-conjugated linkage to the chromophores and
their absorption and fluorescence properties in solution and in the
solid state (Scheme 1).6a Dramatic substituent effects on the solid-
state photophysical properties were observed, which has been
elucidated by means of the X-ray crystallographic analysis. It was
presence of Ni(OCOCH3)2 gave 4-arylated-benzo[c]carbazole-5,6-
dione (1) and 4-aminated-1,2-naphthoquinone (2) in 5% and 35%
yields, respectively. On the other hand, the reaction of sodium 1,2-
naphthoquinone-4-sulfonate with m-butylamino-N,N-dibutylani-
line in DMF in the presence of CuCl2 gave two structural isomers of
4-arylated-N-butylbenzo[c]carbazole-5,6-dione (3) and 4-ami-
nated-benzo[a]carbazole-5,6-dione (4) in 39% and 13% yields, re-
spectively. In both reactions, the formation of a metal chelate
complex between the o-quinone carbonyl groups and the metal ion
probably facilitates the nucleophilic desulpho-amination or the
nucleophilic desulpho-arylation at the 4-position, and the follow-
ing intramolecular cyclization occurs to produce o-quinones with
benzo[a]carbazole or benzo[c]carbazole skeleton, 1, 3, and 4. In-
terestingly, in both reactions, the 4-arylation is in competition with
the 4-amination. The former reaction gives preference to the 4-
amination over the 4-arylation, because the nucleophilicity of
amino group in m-amino-N,N-dibutylaniline is higher than that of
the ortho position of the aniline. Thus, the former reaction afforded
preferentially the 4-aminated-1,2-naphthoquinone (2). On the
other hand, the latter reaction gives preference to the 4-arylation
over the 4-amination, because the sterically hindered N-butyl-
amino group in m-butylamino-N,N-dibutylaniline makes it difficult
for the nucleophilic desulpho-amination. Thus, the latter reaction
afforded preferentially the 4-arylated-N-butylbenzo[c]carbazole-
5,6-dione (3).
confirmed that the formation of intermolecular
pep interactions
between the fluorophores in molecular aggregation states is de-
pendent on the substituents, leading to the differences of the solid-
state fluorescence properties among fluorophores (6aec).
HO
R
HO
Ph
O
O
N
O
R
NBu
NBu
2
2
5a: R = H
5b: R = Bu
6a: R = Me
6b: R = Bu
6c: R = Ph
Scheme 1. Heterocyclic quinol-type fluorophores 5a, 5b, and 6aec.
In this work, to obtain further information about the effect of
molecular and crystal structures in aggregation state on the solid-
statefluorescenceproperties, wehavenewlysynthesizedheterocyclic
quinol-type fluorophores, 9-dibutylamino-5-hydroxy-5-phenyl-5,7-
dihydro-benzo[c]carbazol-6-one (5a) and 7-butyl-9-dibutylamino-
5-hydroxy-5-phenyl-5,7-dihydro-benzo[c]carbazol-6-one (5b)
(Scheme 1), and their photophysical properties along with 6c have
been investigated in solution and in the solid state. Considerable
differences in the photophysical properties among the fluorophores
5a, 5b, and 6c were observed both in solution and in the solid state.
On the basis of the results of the semi-empirical molecular orbital
calculations (AM1 and INDO/S) and the X-ray crystal structures, the
relations between the solid-state fluorescence properties and the
molecular and crystal structures are discussed.
As shown in Scheme 3, the heterocyclic quinols 5a and 5b were
obtained in 21% and 12% yields by the reaction of quinones 1 and 3
with phenyllithium (PhLi) at ꢀ108 ꢁC, respectively. It is known that
the addition of organometallic reagents to quinones gives not only
quinols but also hydroquinone as a by-product: both the 1,2-addi-
tion and the reduction of the quinoid skeleton by organometallic
reagents proceed competitively.9 In our case, the corresponding
hydroquinone produced in situ was easily reoxidized by atmo-
spheric oxygen during work-up of the reaction mixture, resulting in
recovery of the starting quinine (40% for 1 and 32% for 3). For the
quinones 1 and 3, PhLi reagent preferentially attack the 5-carbonyl
carbon than the 6-carbonyl in spite of the similar steric reactivity of
the two carbonyls. The conjugated linkage of the dibutylamino
group to the 6-carbonyl group would make the 6-carbonyl carbon
weaker electrophilic than the 5-carbonyl carbon, so that the
counter anions (Phꢀ) preferentially attack the electrophilic 5-car-
bonyl carbon.
2. Result and discussion
2.1. Synthesis
O
OH
Ph
O
O
We first prepared the starting heterocyclic quinones 1 and 3 as
shown in Scheme 2. The reaction of sodium 1,2-naphthoquinone-
4-sulfonate with m-amino-N,N-dibutylaniline in acetic acid in the
PhLi
THF
-108
N
R
N R
C
O
O
O
NH2
NBu
2
NBu
O
O
2
Ni(OCOCH3)2
O
1: R = H
3: R = Bu
5a: R = H
5b: R = Bu
CH3COOH aq.
R.T.
NH
NBu2
HN
SO3Na
Scheme 3. Synthesis of quinols 5a and 5b.
NBu2
NBu2
1
2
2.2. Spectroscopic properties of 5a, 5b, and 6c in solution
O
O
O
O
NHBu
O
N
O
CuCl2
DMF
The visible absorption and fluorescence spectral data of 5a, 5b,
and 6c in solution are summarized in Table 1. The fluorescence
spectra of the three quinols were recorded by excitation at the
wavelengths of the longest absorption maximum. As shown in
Figure 1a, the three quinols exhibit two absorption maxima at
around 340e385 nm and 430e440 nm in 1,4-dioxane, which are
both red-shifted in the order of 6c (340 and 430 nm) <5a (380 and
436 nm)ꢂ5b (385 and 440 nm). On the other hand, the three
Bu
NBu2
80
C
N
SO3Na
Bu
NBu2
NBu2
3
4
Scheme 2. Synthesis of o-quinones 1e4.

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Y. Ooyama et al. / Tetrahedron 66 (2010) 7954e7960
quinols exhibit a single fluorescence maximum at around 340e385
in 1,4-dioxane, which are also red-shifted in the order of 6c
(484 nm)ꢂ5a (488 nm)ꢂ5b (494 nm) as shown in Figure 1b. The
assigned to the transition from the HOMO to the LUMO, where
HOMO were mostly localized on the dibutylaminoindole moiety
for 5a and 5b and the dibutylaminobenzofurano moiety for 6c,
and the LUMO were mostly localized on the naphthoquinol
moiety for the three quinols. The values of the dipole moments in
the ground states are 5.73 D for 5a, 5.62 D for 5b, and 7.33 D for
6c. The differences between the dipole moments (Dm) of the first
excited (HOMO/LUMO) and the ground states are 4.74 D for 5a,
3.69 D for 5b, and 6.53 D for 6c. The changes in the calculated
electron density accompanying the first electron excitation are
shown in Figure 2, which reveal a strong migration of intra-
molecular charge transfer from dibutylaminoindole moiety or the
dibutylaminobenzofurano moiety to the naphthoquinol moiety in
the three quinols. These calculations indicate that the quinols 5a,
5b, and 6c have similarly large dipole moments in their excited
states, which explains well our finding that the three quinols
show a large bathochromic shift of their fluorescence maxima in
polar solvents and that the Stokes shift values for the three
quinols in polar solvents are much larger than those in non-polar
solvents.
fluorescence quantum yield (
F
) increases in the order of 5b (0.35)ꢂ
5a (0.41)<6c (0.74) in 1,4-dioxane. The absorption maxima of the
three quinols are nearly independent of solvent polarity, while the
fluorescence maxima show a large red-shift on increasing the sol-
vent polarity from 1,4-dioxane to ethanol. Therefore, the Stokes
shift value in polar solvents becomes larger than that in non-polar
solvents. Moreover, significant dependence of the fluorescence
quantum yield on the solvent polarity was also observed: the
F
values of 5a, 5b, and 6c are reduced to ca. 24% (0.41 in 1,4-dioxane
to 0.10 in ethanol), 6% (0.35 in 1,4-dioxane to 0.02 in ethanol), and
20% (0.74 in 1,4-dioxane to 0.15 in ethanol), respectively, with in-
creasing polarity from 1,4-dioxane to ethanol (Table 1).
Table 1
Absorption and fluorescence spectral data of 5a, 5b, and 6c in solution
Quinol Solvent
Absorptiona
Fluorescenceb, c SSd
lmax/nm (3max/Mꢀ1 cmꢀ1
)
lmax/nm (Ff
)
Dlmax/nm
5a
5b
6c
1,4-Dioxane 436(16,300), 380(13,300) 488 (0.41)
Acetonitrile 444(18,800), 380(13,500) 535 (0.15)
52
91
101
54
88
96
54
95
103
Table 2
Calculated absorption spectra for 5a, 5b, and 6c
Ethanol
442(16,100), 382(13,200) 543 (0.10)
Quinol
m
/Da
Absorption (calcd)
CI componentc
Dm/Dd
1,4-Dioxane 440(30,200), 385(15,600) 494 (0.35)
Acetonitrile 448(28,400), 389(14,800) 536 (0.16)
lmax/nm
fb
Ethanol
1,4-Dioxane 430(21,600), 340(9200)
Acetonitrile 441(22,400), 343(10,000) 536 (0.30)
Ethanol 441(22,800), 344(9500) 544 (0.15)
444(29,400), 388(15,000) 540 (0.02)
5a
5b
6c
5.73
5.62
7.33
379
340
381
344
375
325
0.39
0.17
0.33
0.17
0.43
0.18
HOMO/LUMO (86%)
HOMO-1/LUMO (60%)
HOMO/LUMO (76%)
HOMO-1/LUMO (62%)
HOMO/LUMO (88%)
HOMO-1/LUMO (51%)
4.74
3.16
3.69
3.66
6.53
1.74
484 (0.74)
a
2.5ꢃ10ꢀ5 M.
b
c
2.5ꢃ10ꢀ6 M.
Ff values were determined using 9,10-bisphenylethynylanthracene (Ff¼0.84,
a
The values of the dipole moment in the ground state.
Oscillator strength.
The transition is shown by an arrow from one orbital to another, followed by its
lex¼440 nm) in benzene as a standard.
b
c
d
Stokes shift value.
percentage CI (configuration interaction) component.
d
The values of the difference in the dipole moment between the excited and the
ground states.
Figure 1. (a) Absorption and (b) fluorescence spectra of 5a, 5b, and 6c in 1,4-dioxane.
Figure 2. Calculated electron density changes accompanying the first electronic ex-
citation of 5a, 5b, and 6c. The black and white lobes signify the decrease and increase
in electron density accompanying the electronic transition. Their areas indicate the
magnitude of the electron density change.
2.3. Semi-empirical MO calculations (AM1, INDO/S)
The photophysical spectra of 5a, 5b, and 6c were analyzed by
using semi-empirical molecular orbital (MO) calculations. The
molecular structures were optimized by using MOPAC/AM1
method10, and then the INDO/S method11 using the SCRF Onsager
Model was used for spectroscopic calculations in 1,4-dioxane.
The calculated absorption wavelengths and the transition char-
acter of the first and second absorption bands are collected in
Table 2. The calculated absorption wavelengths and the oscillator
strength values are relatively good compatible with the observed
spectra in 1,4-dioxane, although the calculated absorption spec-
tra are blue shifted. This deviation of the INDO/S calculations,
giving high transition energies compared with the experimental
values, has been generally observed.12 The calculations show that
the longest excitation bands for 5a, 5b, and 6c are mainly
2.4. Spectroscopic properties of 5a, 5b, and 6c in the solid
state
Interesting results have been obtained from the photophysical
properties of 5a, 5b, and 6c in the solid state. Figure 3 shows that
the optical properties of the three quinols are quite different be-
tween the solution and the solid state. The quinols 5a, 5b, and 6c
show yellowish-green in 1,4-dioxane, but orange, yellow, and
yellowish-orange in the crystalline state, respectively. On the other
hand, the three quinols exhibit bluish-green fluorescence emission
in 1,4-dioxane, but the crystals of 5b and 6c exhibit green and
greenish-yellow fluorescence emission, respectively. However, the

Y. Ooyama et al. / Tetrahedron 66 (2010) 7954e7960
7957
ꢀ
fluorescence of 5a was strongly quenched in the solid state. In
order to investigate the difference in the solid-state photophysical
properties among the three quinols, we have measured the fluo-
rescence excitation and emission spectra of the crystals. As shown
in Figure 4, the wavelengths of the excitation and emission max-
ima of 5b (lex¼485 nm, lem¼518 nm) and 6c (lex¼519 nm,
lem¼555 nm) are red-shifted by 45, 24 nm and 89, 71 nm com-
pared with those in 1,4-dioxane, respectively, so that the red-shift
values of 6c from 1,4-dioxane to the solid state are larger than that
contacts of less than 3.6 A between the enantiomers and the
-overlappings were observed between the benzo[b]naphtho
p
[1,2-d]furan planes. The interplanar distances between the benzo
[b]naphtho[1,2-d]furan planes are ca. 3.58 A, which suggests in-
ꢀ
termolecular
fore, it has been concluded that the formation of intermolecular
interactions between the fluorophores is responsible for the
pep interactions between the fluorophores. There-
pep
large red-shift of the absorption and fluorescence maxima and
a decrease in the solid-state fluorescence for 6c from 1,4-dioxane to
the solid state. Unfortunately, we could not obtain sufficient sizes of
single crystals for 5b to carry out the X-ray structural analysis,
however, the relatively strong fluorescence intensity for the crystal
of 5b demonstrated that the N-butylation of carbazole moiety can
of 5b. The
0.03, respectively, which are smaller than those in 1,4-dioxane.
The precise evaluation of the value of 5a was difficult because
F values of 5b and 6c in the solid state are 0.07 and
F
the fluorescence of 5a was strongly quenched in the solid state.
From a comparison of photophysical properties between solution
and the solid states, it was found that the excitation and the
emission maxima of 5a, 5b, and 6c in the crystalline state are large
effectively prevent the intermolecular
pep interactions between
the fluorophores.
red-shifted compared with those in 1,4-dioxane, and the
F values
of the three quinols in the crystalline state are much smaller that
those in 1,4-dioxane.
Figure 3. Fluorescence properties of 5a, 5b, and 6c (a) in 1,4-dioxane and (b) in the
solid state before and after UV irradiation.
Figure 5. Crystal packing of 6c (a) a stereoview of the molecular packing structure and
(b) a top view of the pairs of fluorophores.
To elucidate the effects of the molecular packing structure on
drastic solid-state fluorescence quenching for the crystals of 5a, the
X-ray crystal structure of 5a has been determined. In the crystal of
ꢀ
5a, there are no short
pe
p
contacts of less than 3.60 A between the
Figure 4. (a) Solid-state excitation and (b) emission spectra of the crystals of 5b
neighboring fluorophores, which indicates the absence of the pep
(
lex¼485 nm, lem¼518 nm, V¼0.07) and 6c (lex¼519 nm, lem¼555 nm, V¼0.03).
interactions between the fluorophores (Fig. 6a). More interestingly,
an one-dimensional chain is formed through three-type in-
termolecular hydrogen bonding between the equal enantiomers
(Figs. 6b and c); the proton on carbazole nitrogen atom in the en-
antiomer is directing toward the carbonyl oxygen and the hydroxyl
oxygen of another enantiomer to form the bifurcated in-
2.5. Relation between the solid-state fluorescence properties
and X-ray crystal structures
In the previous paper, we have performed X-ray crystallographic
analysis of 6c.6a As shown in Figure 5a, the crystal of 6c is built up
by a centrosymmetric dimer unit, which is composed of a pair of
quinol enantiomers: neighboring enantiomers are connected by
two intermolecular hydrogen bonds between the hydroxyl and
termolecular hydrogen bonding (N(1)H(2)/O(2)
*
angle¼155(3)ꢁ,
*
ꢀ
N(1)/O(2)
N(1)/O(1)
*
distance¼2.897(4) A; N(1)H(2)/O(1)
angle¼126(1)ꢁ,
ꢀ
ꢀ
*
distance¼3.064(4) A distance¼2.800(4) A), and the
hydroxyl proton of the enantiomer is directing toward the carbonyl
carbonyl oxygens through the hydroxyl proton (O(1)/O(2)
*
dis-
oxygen of another enantiomer (O(1)H(1)/O(2)** angle¼145(4)ꢁ, O
ꢀ
ꢀ
tance is 2.812 (4) A). The intramolecular hydrogen bonding for-
mation was also observed between the hydroxyl proton and the
carbonyl oxygen in each quinol molecule (O(1)/O(2) distance is
(1)/O(2)** distance¼2.804(3) A). Above results strongly reveal
that the formation of a continuous intermolecular hydrogen
bonding between the fluorophores is a principal factor of the
drastic solid-state fluorescence quenching for the crystal of 5a.
ꢀ
2.740(2) A). As shown in Figure 5b, there are five short interatomic

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Y. Ooyama et al. / Tetrahedron 66 (2010) 7954e7960
3. Conclusion
To obtain variable information about the effect of molecular and
crystal structures on the solid-state fluorescence properties, the
three heterocyclic quinol-type fluorophores with benzo[c]carbazol-
6-one skeleton or benzo[b]naphtho[1,2-d]furan-6-one skeleton
have been derived from the corresponding o-quinones and their
photophysical properties have been investigated in solution and in
the solid state. The three quinols exhibit a moderate fluorescence
intensity in 1,4-dioxane. However, the fluorescence of 5a with
benzo[c]carbazol-6-one skeleton was strongly quenched in the
solid state. The X-ray crystal structure of 5a demonstrated that the
formation of a continuous intermolecular hydrogen bonding be-
tween the fluorophores is a principal factor of a drastic solid-state
fluorescence quenching for the crystal of 5a. Thus, new valuable
information concerning the effect of molecular and crystal struc-
tures on the solid-state fluorescence of organic fluorescent dyes has
been obtained.
4. Experimental
4.1. General
Elemental analyses were measured with a PerkineElmer 2400 II
CHN analyzer. IR spectra were recorded on a JASCO FT/IR-5300
spectrophotometer for samples in KBr pellet form. Single-crystal
X-ray diffraction was performed on Rigaku AFC7S diffractometer.
Absorption spectra were observed with a JASCO U-best30 spec-
trophotometer and fluorescence spectra were measured with
a JASCO FP-777 spectrophotometer. The fluorescence quantum
yields (
nylanthracene (
F) in benzene were determined using 9,10-bisphenylethy-
F
¼0.84, lex¼440 nm)13 in benzene as the standard.
For the measurement of the solid-state fluorescence excitation and
emission spectra of the crystals, Jasco FP-1060 attachment was
used. The solid-state fluorescence quantum yields (F) were de-
termined by a Hamamatsu C9920-01 equipped with CCD by using
a calibrated integrating sphere system (lex¼485 nm for 5b and
lex¼519 nm for 6c). 1H NMR spectra were recorded on a JNM-LA-
400 (400 MHz) FT NMR spectrometer with tetramethylsilane (TMS)
as an internal standard.
4.2. Synthesis
4.2.1. 9-Dibutylamino-7H-benzo[c]carbazole-5,6-dione
(1)
and
4-(3-dibutylamino-phenylamino)-[1,2]naphthoquinone (2). To a so-
lution of sodium 1,2-naphthoquinone-4-sulfonate (10.38 g,
40 mmol) and Ni(OCOCH3)2$4H2O (9.93 g, 40 mmol) in acetic acid
aqueous solution (80%, 250 ml) was add m-amino-N,N-dibutyla-
niline (8.8 g, 40 mmol) with stirring at room temperature. After
further stirring for 12 h, the reaction mixture was poured into
water. The resulting precipitate was filtered, washed with water
and dried. The residue was chromatographed on silica gel (n-hex-
ane/ethyl acetate¼2:1 as eluent) to give 1 (0.8 g, yield 5%) as
a purple powder and 2 (5.3 g, yield 35%) as a red powder.
Compound 1: mp 221e222 ꢁC; 1H NMR (400 MHz, DMSO-d6,
TMS)
d
¼0.93 (t, J¼7.3 Hz, 6H), 1.32e1.37 (m, 4H), 1.52e1.57 (m, 4H),
3.22e3.51 (m, 4H) (overlapping peak of dissolved water in DMSO-
d6), 6.39 (s, 1H), 6.82 (d, J¼9.5 Hz, 1H), 7.30 (t, J¼7.6 Hz, 1H), 7.62
(t, J¼7.8 Hz, 1H), 7.81 (d, J¼9.5 Hz, 1H), 8.00e8.04 (m, 2H), 11.7 (s,
1H, eNH); IR (KBr):
[MþH]þ
n
¼3312, 1685, 1636 cmꢀ1; MS (ESI, m/z) 375
Compound 2: mp 204e205 ꢁC; 1H NMR (400 MHz, DMSO-d6,
Figure 6. Crystal packing and hydrogen bonding pattern of 5a (a) a stereoview of the
molecular packing structure, (b) intermolecular hydrogen bonding between fluo-
rophores and (c) a schematic structure.
TMS)
d
¼0.90 (t, J¼7.3 Hz, 6H), 1.25e1.35 (m, 4H), 1.46e1.54 (m, 4H),
3.20e3.50 (m, 4H) (overlapping peak of dissolved water in DMSO-
d6), 5.78 (s, 1H), 6.52e6.57 (m, 3H), 7.22 (t, J¼7.8 Hz, 1H), 7.72 (t,
J¼7.6 Hz, 1H), 7.85 (t, J¼7.8 Hz, 1H), 8.03 (d, J¼8.0 Hz, 1H), 8.31

Y. Ooyama et al. / Tetrahedron 66 (2010) 7954e7960
7959
(d, J¼8.0 Hz, 1H), 9.76 (br, 1H, eNH); IR (KBr):
MS (ESI, m/z) 377 [MþH]þ
n
¼3315, 1584 cmꢀ1
;
empirical method INDO/S (intermediate neglect of differential
overlap/spectroscopic)11 using the SCRF Onsager Model. All INDO/S
calculations were performed using single excitation full SCF/CI
(self-consistent field/configuration interaction), which includes the
configuration with one electron excited from any occupied orbital
to any unoccupied orbital, 225 configurations were considered for
the configuration interaction [keyword CI (15 15)].
4.2.2. 7-Butyl-9-dibutylamino-7H-benzo[c]carbazole-5,6-dione (3)
and 11-butyl-9-dibutylamino-11H-benzo[a]carbazole-5,6-dione (4).
To a solution of sodium 1,2-naphthoquinone-4-sulfonate (0.5 g,
1.92 mmol) and CuCl2 (0.26 g, 1.92 mmol) in DMF (10 ml) was add
m-butylamino-N,N-dibutylaniline (0.53 g, 1.92 mmol) with stirring
at 80 ꢁC. After further stirring for 2 h, the reaction mixture was
poured into water. The resulting precipitate was filtered, washed
with water, and dried. The residue was chromatographed on silica
gel (CH2Cl2 as eluent) to give 3 (0.32 g, yield 39%) as a black powder
and 4 (0.11 g, yield 13%) as a brown powder.
4.4. X-ray crystallographic studies
The data sets were collected at 23ꢄ1 ꢁC on a Rigaku AFC7S four-
circle diffractometer by 2
q u scan technique, and using graphite-
ꢀ
ꢀ
monochromated Mo K
a
(l¼0.71069 A) radiation at 50 kV and
Compound 3: mp 169e170 ꢁC; 1H NMR (400 MHz, CDCl3, TMS)
30 mA. In all case, the data were corrected for Lorentz and polari-
zation effects. A correction for secondary extinction was supplied.
The reflection intensities were monitored by three standard re-
flections for every 150 reflections. An empirical absorption cor-
rection based on azimuthal scans of several reflections was applied.
All calculations were performed using the teXsan14 crystallographic
software package of Molecular Structure Corporation.
d
¼0.94e1.02 (m, 9H), 1.36e1.46 (m, 6H), 1.62e1.70 (m, 4H),
1.71e1.81 (m, 2H), 3.40 (t, J¼8.3 Hz, 4H), 4.47 (t, J¼9.6 Hz, 2H), 6.20
(d, J¼2.0 Hz, 1H), 6.78 (dd, J¼2.0 and 9.3 Hz, 1H), 7.23 (t, J¼7.9 Hz,
1H), 7.52 (t, J¼7.7 Hz, 1H), 7.88e7.93 (m, 2H), 7.99 (dd, J¼1.5 and
7.6 Hz, 1H); IR (KBr):
n
¼1690, 1637 cmꢀ1; MS (ESI, m/z) 431 [MþH]þ
Compound 4: mp 87e89 ꢁC; 1H NMR (400 MHz, CDCl3, TMS)
¼0.91e1.00 (m, 9H), 1.25e1.44 (m, 6H), 1.59e1.67 (m, 4H),
d
1.78e1.87 (m, 2H), 3.35 (t, J¼7.6 Hz, 4H), 4.15 (t, J¼7.1 Hz, 2H), 6.21
(d, J¼2.0 Hz, 1H), 6.68 (dd, J¼2.0 and 9.0 Hz, 1H), 6.92 (t, J¼7.3 Hz,
1H), 6.99 (d, J¼7.1 Hz, 1H), 7.13 (t, J¼6.8 Hz, 1H), 7.20 (d, J¼7.1 Hz,
4.4.1. Crystal structure determination of compound 5a. Crystal of 5a
was recrystallized from dichloromethane/n-hexane as orange
prism, air stable. The one selected had approximate dimensions
0.25ꢃ0.25ꢃ0.35 mm. The transmission factors ranged from 0.98 to
1.00. The crystal structure was solved by direct methods using SIR
92.15 The structures were expanded using Fourier techniques.16 The
non-hydrogen atoms were refined anisotropically. Some hydrogen
atoms were refined isotropically, the rest were fixed geometrically
1H), 7.44 (d, J¼9.0 Hz, 1H); IR (KBr):
n
¼1681 cmꢀ1
.
4.2.3. General synthetic procedure for the quinols 5a or 5b by the
reaction of quinones 1 or 3 with phenyllithium reagent. To a THF
solution of quinone 1 (or 3) under an argon atmosphere was added
ethereal solution of phenyllithium at ꢀ108 ꢁC over 15 min. During
the course of addition, the red solution turned to a reddish brown
solution. After stirring for 15 min at room temperature, the reaction
was quenched with saturated NH4Cl solution. The solvent was
evaporated and the residue was extracted with CH2Cl2. The organic
extract was washed with water. The CH2Cl2 extract was evaporated
and the residue was chromatographed on silica gel (CH2Cl2/ethyl
acetate¼10:1 as eluent) to give 5a or 5b.
and not refined. Crystal data for 5a: C30H32N2O2, M¼452.59,
ꢀ
monoclinic, a¼22.388(3), b¼7.749(1), c¼14.871(2) A,
b¼106.501
(8) , U¼2473.8(5) A , rcalcd¼1.215 gcmꢀ3, T¼297 K, space group
3
ꢀ
ꢁ
P21/n (no.14), Z¼4,
m(Mo K
a
)¼0.76 cmꢀ1, 6248 reflections mea-
sured, 5815 unique (Rint¼0.016), which were used in all calcula-
tions. The final
R
indices [I>2
s
(I)], R1¼0.063, wR(F2)¼0.174.
Crystallographic data (excluding structure factors) has been de-
posited with Cambridge Crystallographic Data Centre as supple-
mentary publication number CCDC 783289. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.au.uk/data_request/cif.
4.2.3.1. 9-Dibutylamino-5-hydroxy-5-phenyl-5,7-dihydro-benzo
[c]carbazol-6-one (5a). Yield 21%, an orange powder; mp
209e215 ꢁC; 1H NMR (400 MHz, CDCl3, TMS)
d
¼0.98 (t, J¼7.4 Hz,
6H), 1.35e1.45 (m, 4H), 1.60e1.67 (m, 4H), 3.37 (t, J¼7.8 Hz, 4H),
4.45 (s, 1H, eOH), 6.43 (d, J¼2.2 Hz, 1H), 6.82 (dd, J¼2.2 and
9.2 Hz, 1H), 7.13e7.43 (m, 7H), 7.56 (dd, J¼1.2 and 7.8 Hz, 1H),
Acknowledgements
This work was supported in part by a Grant-in-Aid for Scientific
Research (C) (21550181) from the Japan Society for the Promotion
of Science.
8.06e8.14 (m, 2H), 8.64 (br, 1H, eNH); IR (KBr):
n
¼3418, 3258,
1633 cmꢀ1. Anal. Calcd (%) for C30H32N2O2: C 79.61, H 7.13, N 6.19;
found: C 79.96, H 7.18, N 6.20.
Supplementary data
4.2.3.2. 7-Butyl-9-dibutylamino-5-hydroxy-5-phenyl-5,7-dihy-
dro-benzo[c]carbazol-6-one (5b). Yield 12%, a yellow powder; mp
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.tet.2010.08.026.
118e120 ꢁC; 1H NMR (400 MHz, CDCl3, TMS)
d
¼0.73 (t, J¼7.3 Hz,
3H), 0.97e1.10 (m, 8H), 1.36e1.45 (m, 4H), 1.56e1.69 (m, 6H), 3.39
(t, J¼7.8 Hz, 4H), 4.42e4.29 (m, 1H), 4.44e4.51 (m, 1H), 4.82 (s, 1H,
eOH), 6.30 (d, J¼2.2 Hz, 1H), 6.82 (dd, J¼2.2 and 9.3 Hz, 1H),
7.12e7.41 (m, 7H), 7.58 (dd, J¼1.5 and 7.8 Hz, 1H), 8.09e8.15
References and notes
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