Heterocyclic quinol-type fluorophores. Synthesis of novel imidazoanthraquinol derivatives and their photophysical properties in benzene and in the crystalline state

Article abstract of DOI:10.1039/b410311d

An isomeric pair of novel imidazoanthraquinol fluorophores 2 and 3 exhibiting two tautomeric forms (A and B) that are possible for the imidazole ring have been developed. In order to control the tautomeric form to improve the fluorescence properties, the

Full text of DOI:10.1039/b410311d

View Article Online / Journal Homepage / Table of Contents for this issue
P A P E R
Heterocyclic quinol-type fluorophores.w Synthesis of novel
imidazoanthraquinol derivatives and their photophysical
properties in benzene and in the crystalline statez
Yousuke Ooyama, Takato Nakamura and Katsuhira Yoshida*
Department of Material Science, Faculty of Science, Kochi University, Akebono-cho,
Kochi 780-8520 Japan. E-mail: kyoshida@cc.kochi-u.ac.jp; Fax: þ81 88-844-8359
Received (in Durham, UK) 6th July 2004, Accepted 10th November 2004
First published as an Advance Article on the web 4th January 2005
An isomeric pair of novel imidazoanthraquinol fluorophores 2 and 3 exhibiting two tautomeric forms
(A and B) that are possible for the imidazole ring have been developed. In order to control the tautomeric
form to improve the fluorescence properties, the N-butylated imidazole derivatives 6 and 7 have further been
synthesized. The fluorescence intensity of the quinols was in the order 3 { 6 o 7 o 2 in benzene, which
is quite different from the order 3 { 2 { 6 o 7 in the crystalline state. To investigate the effect of
N-alkylation of imidazole ring on the photophysical properties of the quinol fluorophores in solution and
in the crystalline state, we have performed semi-empirical molecular orbital calculations (AM1 and INDO/S)
and X-ray crystallographic analysis. On the basis of the results of calculations and the X-ray crystal
structures, the N-alkylation effects on the chemical structure of the quinol fluorophores and on their
solid-state photophysical properties are discussed.
control of the tautomeric form by N-alkylation of the imida-
Introduction
zole ring. Therefore, we have further synthesized the N-buty-
lated derivatives 6 and 7. To elucidate the relationship between
the photophysical properties and the chemical and crystal
structures, semi-empirical molecular orbital calculations
(AM1 and INDO/S) and the X-ray crystallographic analysis
of 2a, 3a, 6 and 7 have been carried out.
Organic fluorophores have received much attention in recent
years, because of their many applications in the optoelectronics
industry such as dye lasers, solar energy converting materials,
and emitters in optoelectronic devices.1 A great number of
fluorescent compounds have been developed and the relation-
ship between their chemical structure and fluorescence proper-
ties examined. However, very little is known about the
influence of molecular packing structure of fluorophores on
their solid-state fluorescence properties.2–6 Therefore, the num-
ber of fluorescent compounds that exhibit strong solid-state
emission properties is relatively limited.
In Part 1 and Part 2 of this series of the heterocyclic quinol-
type fluorophores, we have reported benzofuranonaphtho-
quinol-type fluorophores that can form crystalline inclusion
compounds with various amine molecules.4 The fluorescence of
the quinols in the solid state is greatly quenched in comparison
with that in solution. However, the fluorescence of the quinol
crystals is enhanced in various degrees depending on the
enclathrated amine molecules. These specific properties of the
quinol fluorophores that exhibit dramatic fluorescence en-
hancement upon complexation with guest molecules will be
useful for fundamental research into solid state fluorescence
and for the development of new intense solid-emissive materi-
als. In connection with above research, we have developed
novel imidazoanthraquinol fluorophores 2 and 3 in which two
tautomeric forms (A and B) are possible for the imidazole
ring.7,8 On account of the tautomerism of the imidazole ring,
the two isomeric fluorophores were considered to show a
variety of photophysical properties in solution and in the
crystalline state. Moreover, new compounds exhibiting intense
solid-fluorescence properties were expected to be obtained by
Results and discussion
Synthesis of imidazoanthraquinol fluorophores
The synthesis of the isomeric pairs of imidazoanthraquinol
fluorophores is outlined in Scheme 1. We first prepared the
starting heterocyclic quinone 1 by refluxing an equimolar
amount of 1,2-diaminoanthraquinone with p-(diethylamino)-
benzaldehyde in acetic acid in the presence of copper(II)
acetate. Next, the heterocyclic quinone-type dye 1 was allowed
to react with organometallic reagents to give the isomeric pairs
of quinol compounds 2 and 3 in which two tautomeric forms
(A and B) are possible for the imidazole ring. As shown in
Table 1, the ratios of the products (2 : 3) were greatly depen-
dent on steric factors of the organometallic reagents. For
example, the reaction with MeMgI afforded a 2a : 3a ratio of
31 : 69 (entry 1), whereas the reaction with MeLi afforded a
2a : 3a ratio of 83 : 17 (entry 2): the selectively of 2a to 3a being
quite reversed. These results suggest that the relatively small
MeLi could preferentially attack the more electrophilic carbo-
nyl carbon to give 2a, while the relatively large and heavily
solvated MeMgI reagent attacks the less-hindered carbonyl
carbon to give 3a. The results given for entries 2–4 in Table 1
also suggest that the preparation of isomer 2 becomes difficult
as the counteranion (Rꢀ) of organo-lithium reagents becomes
bulky. On the other hand, the synthesis of N-alkylated imida-
zoanthraquinol derivatives was achieved according to Scheme 2.
The reaction of 1,2-diaminoanthraquinone with 1-iodobutane
produced 1-amino-2-butylaminoanthraquinone 4 in 66% yield.
The quinone 5 was synthesized in 77% yield by refluxing an
equimolar amount of 1-amino-2-butylaminoanthraquinone
w Part 3. For Part 2, see: ref. 4b.
z Electronic supplementary information (ESI) available: Table S1
Crystal data and structure refinement parameter for the quinol deri-
vatives 2a, 3a, 6 and 7. See http://www.rsc.org/suppdata/nj/b4/
b410311d/
T h i s j o u r n a l i s & T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 5
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6
447

View Article Online
Scheme 1
Table 1 Synthesis of the quinols 2 and 3 by the reaction of 1 with organo-lithium or magnesium reagent
Product
Entry
Reagent
Quinols
Yield (%)
Ratio 2 : 3
Recovery (%) of 1
1
2
3
4
MeMgI
MeLi
2a þ 3a
2a þ 3a
2b þ 3b
3c
82.1
66.5
73.6
33.3
31 : 69
83 : 17
34 : 66
0 : 100
11.8
17.0
7.6
n-BuLi
PhLi
63.8
with p-(diethylamino)benzaldehyde in acetic acid in the pre-
sence of copper(II) acetate, and then the reaction of 5 with
organometallic reagents at low temperature gave quinols 6 and
7 in 30 and 43% yields, respectively.
bands in the visible region at around 416 nm and 327 nm
and the corresponding fluorescence band observed at
around 480 nm; however, it was difficult to determine
exactly its quantum yield because of a feeble fluorescence
intensity. Comparing the absorption and fluorescence spectra
of 2a and 3a, the quinol 2a exhibits much stronger absorption
and fluorescence intensities than the quinol 3a in benzene.
Because of the non-conjugated linkage of the substituents
(R ¼ Me, Bu and Ph) to the chromophore skeleton,
the absorption and fluorescence spectra of the compounds
belonging to the same type of isomers resemble each other
very well.
In contrast, the N-butylated compounds 6 and 7 showed
quite different absorption and fluorescence spectra compared
to those of 2a and 3a. The absorption maxima of 6 (lmax ¼ 352
and 315 nm) and 7 (lmax ¼ 389 and 297 nm) were shifted to
shorter wavelengths compared to those of 2a and 3a. The
N-butylation of 2a and 3a adversely affected their fluorescence
properties: the fluorescence quantum yield of 6 (lem ¼ 432 nm,
F ¼ 0.028) is smaller than that of 2a, while the fluorescence
Spectroscopic properties of the imidazoanthraquinol
fluorophores in solution
The absorption and fluorescence spectra of the quinol deriva-
tives 2, 3, 6 and 7 in benzene are summarized in Fig. 1 and
Table 2. The fluorescence spectra of the quinols were recorded
at the wavelengths of the longest absorption maximum.
The two kinds of isomers (2, 3 and 6, 7) have respectively the
same donor–acceptor chromogens, but a marked difference in
degree of the donor–acceptor conjugation, which leads to quite
different absorption and fluorescence spectra in benzene.
The quinol 2a exhibited absorption maximum at around 369
nm and structureless absorption band at around 316 nm and
fluorescence band at around 469 nm (F ¼ 0.20). On the other
hand, the compound 3a exhibited two distinct absorption
Scheme 2
448
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6

View Article Online
25–291 in spite of the tautomeric forms. On the other hand, the
calculated torsion angles of 6 and 7 were ca. 55.41 and 49.11,
respectively, which is attributed to steric hindrance between the
N-butyl group and the p-diethylaminophenyl group. The
INDO/S calculations show that the oscillator strength (f) of
the first excitation band (lmax ¼ 341 nm, f ¼ 0.97) is larger than
that of the second excitation band (lmax ¼ 314 nm, f ¼ 0.21) in
the case of 2a in A-form, while in B-form the f-value of the
second excitation band (lmax ¼ 309 nm, f ¼ 0.63) is larger than
that of the first excitation band (lmax ¼ 334 nm, f ¼ 0.59). On
the contrary, the f-value of the second excitation bands (lmax
¼
306 nm, f ¼ 0.69) is larger than that of the first excitation band
(lmax ¼ 358 nm, f ¼ 0.45) in the case of 3a in A-form, while in
the B-form the f-value of the first excitation band (lmax ¼ 352
nm, f ¼ 0.67) is larger than that of the second excitation band
(lmax ¼ 302 nm, f ¼ 0.40). From the calculation data it was
presumed that both of the compounds 2a and 3a probably exist
in A-form in benzene. In respect of the donor–acceptor con-
jugation, the A-form of 2a is more conjugative but the A-form
of 3a is less conjugative in comparison with the B-form of 3a.
In contrast, in the case of 6, the f-value of first excitation band
(lmax ¼ 324 nm, f ¼ 0.21) is smaller than that of the second
excitation band (lmax ¼ 294 nm, f ¼ 0.76). In the case of 7, the
f-value of the first excitation band (lmax ¼ 343 nm, f ¼ 0.48) is
larger than that of the second excitation band (lmax ¼ 302 nm,
f ¼ 0.29). The wavelengths of the first and second excitation
bands of 6 and 7 are shorter than those of 2a and 3a. These
calculated absorption wavelengths and the oscillator strength
values match relatively well the observed spectra in benzene,
although the calculated absorption spectra are blue shifted.
This deviation of the INDO/S calculations, giving high transi-
tion energies compared with the experimental values, has been
generally observed.11,12 The calculations also show that the
first excitation bands for the four quinols are mainly assigned
to the transition from the HOMO to the LUMO, where
HOMO were mostly localized on the p-diethylaminophenyl
and benzo-imidazole moieties, and the LUMO were mostly
localized on the anthraquinol moiety. The calculated electron
density changes accompanying the first electron excitation are
shown in Fig. 2, which shows a strong migration of intramo-
lecular charge-transfer character of the four quinols. As clearly
seen, the calculated electron density changes of 6 and 7 are
quite similar to those of the B-form of 2a and 3a, respectively.
On the other hand, as shown in Fig. 3, the values of the dipole
moment of the quinols are large except for that of the A-form
of 3a. It is noteworthy that the directions of the dipole moment
differ between the A-form and the B-form in both 2a and 3a. In
addition, the directions of the dipole moment of 6 and 7 are
almost the same as those of the B-forms of 2a and 3a,
respectively. These results clearly show that the N-alkylation
of the imidazole ring of 2a and 3a can fix the tautomeric
form and the resulting compounds 6 and 7 have the elec-
tronic natures corresponding to the B-forms of 2a and 3a,
respectively.
Fig. 1 (a) Absorption and (b) fluorescence spectra of compounds 2a,
3a, 6 and 7 in benzene.
quantum yield of 7 (lem ¼ 497 nm, F ¼ 0.041) is much larger
than that of 3a. These results show that the fluorescence
quantum yield becomes smaller when the control of the
tautomerism by the N-butylation decreases the degree of donor–
acceptor conjugation as in the case of 6, but when the control of
the tautomerism increases the degree of donor–acceptor conjuga-
tion, as in the case of 7, the fluorescence quantum yield becomes
larger.
Semi-empirical MO calculations (AM1, INDO/S)
We have carried out semi-empirical molecular orbital (MO)
calculations for the quinol fluorophores 2a and 3a (for both in
A- and B-form), 6 and 7 by the INDO/S9 after geometrical
optimizations using MOPAC/AM1 calculations.10 The calcu-
lated absorption wavelengths and the transition character of
the first and second absorption bands are collected in Table 3.
The calculated torsion angles between the p-diethylamino-
phenyl group and the imidazole ring of the 2a and 3a are ca.
Table 2 Absorption and fluorescence spectral data of 2, 3, 6 and 7 in benzene
Fluorescence (Obs.)
em/nm
Absorption (Obs.)
max/nm (emax/dm3 molꢀ1 cmꢀ1
SSa
Quinol
l
)
l
F
Dlmax/nm
2a
2b
3a
3b
3c
6
369 (25 300), 316 (22 800)
368 (26 200), 318 (22 700)
416 (13 000), 327 (32 900)
415 (15 000), 327 (33 400)
420 (13 000), 328 (31 400)
352 (18 000), 315 (32 300)
389 (17 700), 297 (24 500)
469
468
480
468
0.20
0.19
100
100
64
o0.001
o0.001
53
b
—
b
b
—
—
432
497
0.028
0.041
80
108
7
a
b
Stokes shift value. Too weak to be measured.
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6
449

View Article Online
Table 3 Geometry optimization and calculated absorption spectra for the compounds 2a and 3a (for both in A- and B-form), 6 and 7
Absorption (calc.)
max/nm
a
b
c
d
Quinol
Torsion angle/1
l
f
CI component
m/D
2a-A-form
28.5
341
314
334
0.97
0.21
0.59
HOMO - LUMO (65%)
HOMO - 1-LUMO (52%)
HOMO - LUMO (46%)
HOMO - LUMO þ 1 (22%)
HOMO - LUMO þ 1 (63%)
HOMO - LUMO (65%)
HOMO - LUMO þ 1 (77%)
HOMO - LUMO (75%)
HOMO - 1-LUMO (47%)
HOMO - LUMO þ 1 (21%)
HOMO - LUMO (41%)
HOMO - 1-LUMO (18%)
HOMO - LUMO þ 1 (73%)
HOMO - LUMO (60%)
HOMO - 1-LUMO (30%)
HOMO - 2-LUMO (27%)
c
9.12
2a-B-form
27.5
9.04
309
358
306
352
302
0.63
0.45
0.69
0.67
0.40
3a-A-form
3a-B-form
27.8
25.6
3.04
8.14
6
7
a
55.4
49.1
324
0.21
9.82
6.82
294
343
302
0.76
0.48
0.29
b
Torsion angle between imidazole ring and p-diethylaminophenyl group. Oscillator strength. The transition is shown by an arrow from one
d
orbital to another, followed by its percentage CI (configuration interaction) component. The values of the dipole moment in the ground state.
98 nm in comparison with the values of the absorption and
fluorescence maxima of 2a in benzene, respectively. Such large
bathochromic shifts of the absorption and fluorescence wave-
lengths on going from solution to the solid state have been
observed in other chromophores having intramolecular charge
transfer character.13–15 The fluorescence excitation and emis-
Spectroscopic properties of the imidazoanthraquinol
fluorophores in solid state
Interesting results have been obtained from the solid-state
fluorescence excitation and emission spectra of the crystals
2a, 3a, 6 and 7, which are shown in Fig. 4. The quinols 6 and 7
exhibit much stronger fluorescence intensities than 2a and 3a,
the fluorescence intensity increases in the order 3a { 2a { 6 o
7 in the crystalline state, which is quite different from the order
3a { 6 o 7 o 2a in benzene. The longest wavelength of
fluorescence excitation and emission maxima of 2a is located at
around 520 and 567 nm, which are red-shifted by 151 and
sion maxima of 6 (lex ¼ 413 nm, lem ¼ 457 nm) and 7 (lex
¼
445 nm, lem ¼ 513 nm) show a blue shift with intense
fluorescence compared with those of 2a and 3a, respectively.
While the fluorescence quantum yield of 2a is ca. 7-fold larger
than that of 6 in benzene, the fluorescence intensity of 6 is
ca. 52-fold larger than that of 2a in the crystalline state. The
red-shifts of the longest wavelengths of the excitation and the
emission maxima of 6 and 7 in the solid state are small
Fig. 2 Calculated electron density changes accompanying the first
electronic excitation of 2a, 3a (A-form and B-form), 6 and 7. The red
and blue lobes signify decrease and increase in electron density
accompanying the electronic transition. Their areas indicate the
magnitude of the electron density change.
Fig. 3 The directions of dipole moments of 2a, 3a (A-form and
B-form), 6 and 7.
450
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6

View Article Online
large dipole moment of the host molecules is counteracted.
However, such arrangement is not observed in the crystal
packing structure of 3a, because of small dipole moment of
3a in the A-form. The packing structures demonstrate that the
all quinols except for 3a are built up from a centrosymmetric
dimer unit, and that the molecules are arranged in a ‘‘herring-
bone’’ fashion in 2a, 3a and 7 and in a ‘‘bricks in a wall’’
fashion in 6, respectively.
Fig. 5(a) shows the molecular packing structure for the
crystal of 2a. The tautomeric form for the crystal of 2a is
A-form. The crystal of 2a having the herringbone packing is
built up by a centrosymmetric dimer unit which is composed of
a pair of enantiomers bound cofacially by two intermolecular
hydrogen bonds between the hydroxyl oxygen and imidazole
nitrogen through the hydroxyl proton, which is realized on
both sides of the molecules (O(1)H(1)ꢁ ꢁ ꢁN(2)* angle ¼ 168(4)1,
O(1)ꢁ ꢁ ꢁN(2)* distance ¼ 2.985 (4) A) as shown in Fig. 5(b). The
phenyl group is twisted out of the plane of the heterocyclic
quinol skeleton by 12.01, which is smaller than that of the
optimized geometries of 2a (28.51 in Table 3) by MOPAC/
AM1 calculations. The intramolecular hydrogen bonding
formation is also observed between the imidazole amino
proton and the hydroxyl oxygen in each quinol molecule
(N(1)H(2)ꢁ ꢁ ꢁO(1) angle ¼ 115(2)1, N(1)ꢁ ꢁ ꢁO(1) distance ¼
2.894(3) A). A side view of the dimer unit and its upside view
together with the non-bonded interatomic distances of less
than 3.60 A are shown in Fig. 5(c) and (d), respectively. The
p-stacking between a pair of quinol enantiomers is overlapping
the whole molecule from the donor unit of p-diethylamino-
phenyl moiety to the acceptor unit of imidazoanthraquinol
moiety, there are 18 (¼ 9 ꢂ 2) short interatomic p–p contacts in
the pair of enantiomers. The interplanar distance between the
imidazole plates is ca. 3.39 A, which suggests strong p–p
interactions. No hydrogen bonding interactions and no short
p–p contacts of less than 3.60 A are observed between neigh-
bouring units. Therefore, such strong intermolecular interac-
tions between the enantiomers are considered to induce the
large red-shift of the absorption and fluorescence maxima and
an intense fluorescence quenching in the crystalline state.
Fig. 4 Solid-state excitation (ꢁ ꢁ ꢁ) and emission (—) spectra of the
crystals of 2a, 6 and 7; 2a: lex ¼ 520 nm, lem ¼ 567 nm; 6: lex ¼ 413 nm,
lem ¼ 457 nm; 7: lex ¼ 445 nm, lem ¼ 513 nm.
compared to those of 6 and 7 in benzene, which is a quite
different behaviour from 2a. These results indicate that
the larger the red-shift value of the absorption and the fluor-
escence maximum from the solution to the solid state, the
greater the fluorescence quenching.
X-Ray crystal structures of the imidazoanthraquinol
fluorophores
In order to investigate the effect of the crystal structure on the
solid-state photophysical properties, we have performed X-ray
crystallographic analysis of 2a, 3a, 6 and 7. The crystal systems
were a monoclinic space group P21/c with Z ¼ 4 for 2a, an
orthorhombic space group Pna21 with Z ¼ 4 for 3a, a mono-
clinic space group P21/c with Z ¼ 4 for 6 and a monoclinic
space group P21/n with Z ¼ 4 for 7 (Table S1z). In the crystal
packing structures of 2a, 6 and 7, the two host enantiomers are
arranged to form a centrosymmetric dimer unit in which a
Fig. 5 Crystal packing and hydrogen bonding pattern of 2a: (a) a stereoview of the molecular packing structure, and (b) a schematic structure, (c)
a side view, and (d) a top view of the pairs of enantiomers.
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6
451

View Article Online
Fig. 6 Crystal packing and hydrogen bonding pattern of 3a: (a) a stereoview of the molecular packing structure, and (b) a schematic structure,
(c) intra- and intermolecular hydrogen bond between enantiomers and (d) the nearest contact between enantiomers.
Fig. 6(a) shows the molecular packing structure for the
crystal of 3a. The tautomeric form for the crystal of 3a is
the A-form. The phenyl group is twisted out of the plane of
the heterocyclic quinol skeleton by 4.81 as shown in Fig. 6(b).
The value of torsion angle of 3a in the crystalline state is
smaller than that of the optimized geometries of 3a (27.81 in
Table 3) by MOPAC/AM1 calculations. The intramolecular
hydrogen bonding formation is observed between the imida-
zole amino proton and the carbonyl oxygen (N(1)H(2)ꢁ ꢁ ꢁO(2)
angle ¼ 112(3)1, N(1)ꢁ ꢁ ꢁO(2) distance ¼ 2.794(6) A). Further-
more, a one-dimensional chain is formed through the inter-
molecular hydrogen bonding between the hydroxyl proton and
imidazole nitrogen of neighbouring enantiomers, which con-
tributes to stabilize the crystal structure (O(1)H(1)ꢁ ꢁ ꢁN(2)*
angle ¼ 158(4)1, O(1)ꢁ ꢁ ꢁN(2)* distance ¼ 2.855(4) A). The
existence of the intermolecular hydrogen bonding may raise the
melting temperature: the melting point of 3a (223–224 1C) is
considerably higher than that of the structural isomer 2a
(decomposition at 180 1C). As shown in Fig. 6(c) and (d),
there are three kinds of non-bonded short interatomic contacts
of less than 3.60 within one-dimensional chain
A
a
(C(12)ꢁ ꢁ ꢁC(18)* ¼ 3.582(6) A) and between the one-dimen-
sional chains (O(2)ꢁ ꢁ ꢁC(5)* ¼ 3.387(6) A and O(2)ꢁ ꢁ ꢁC(4)* ¼
3.333(6) A). These results suggest that non-fluorescence of 3a
in the crystalline state is attributed to the A-form being
unfavourable for donor–acceptor conjugation and the large-
range intermolecular hydrogen bonds forming a one-dimen-
sional chain16 and that non-bonded short interatomic contacts
between the fluorophores would also be the factors for
fluorescence quenching in the solid state.
Fig. 7(a) shows the molecular packing structure for the
crystal of 6. The crystal of 6 has stacking arrangement that
avoid short contacts between the chromophores. The forma-
tion of intramolecular hydrogen bonding is observed between
the hydroxyl oxygen and imidazole nitrogen through the
hydroxyl proton (O(1)H(1)ꢁ ꢁ ꢁN(1) angle
¼
145(2)1,
O(1)ꢁ ꢁ ꢁN(1) distance ¼ 2.852(2) A) (Fig. 7(b)). However, there
are no intermolecular hydrogen bonding interactions and no
Fig. 7 Crystal packing and hydrogen bonding pattern of 6: (a) a stereoview of the molecular packing structure, and (b) a schematic structure, (c)
a side view and (d) a top view of the pairs of enantiomers.
452
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6

View Article Online
Fig. 8 Crystal packing and hydrogen bonding pattern of 7: (a) a stereoview of the molecular packing structure, and (b) a schematic structure, (c)
a side view and (d) a top view of the pairs of enantiomers.
short p–p contacts of less than 3.60 A between the neighbour-
ing fluorophores (Fig. 7(c) and (d)). The phenyl group is
twisted out of the plane of the heterocyclic quinol skeleton
by 50.81, which is large compared to the torsion angle of 2a.
The value of the torsion angle of 6 in the crystalline state is
close to that of the optimized geometries of 6 (55.41 in Table 3)
by MOPAC/AM1 calculations. It is clear that the large torsion
angle of 6 is attributed to the steric effect of the N-butyl group.
Consequently, the N-butylation of imidazole ring of 2a pre-
vents the formation of intermolecular hydrogen bonding and
short p–p contacts between the fluorophores in the solid state,
which leads to the crystal of 6 exhibiting much stronger
fluorescence with a blue-shift of the fluorescence wavelength
compared to the crystal of 2a.
state fluorescence compounds have been prepared by control of
the tautomeric form by N-alkylation of the imidazole ring. The
relationship between the photophysical properties and the
chemical and crystal structures has been elucidated by means
of semi-empirical MO calculations (AM1 and INDO/S) and
the X-ray crystallographic analysis. The intermolecular p–p
interactions and hydrogen bonding between neighbouring
fluorophores are found to influence the solid-state photophy-
sical properties, such as absorption and fluorescence
wavelengths and solid-state fluorescence intensity. The
effectiveness of the control of the tautomeric form and the
crystal structure, which is important for both the basic science
and the development of new solid-emissive materials, has been
shown.
On the other hand, the crystal of 7 is built up by a
centrosymmetric dimer unit which is composed of a pair of
quinol enantiomers bound cofacially by two intermolecular
hydrogen bonds between the hydroxyl oxygen and imidazole
nitrogen through the hydroxyl proton (O(1)H(1)ꢁ ꢁ ꢁN(1)*
angle ¼ 173(12)1, O(1)ꢁ ꢁ ꢁN(1)* distance ¼ 2.960(7) A), which
is realized on both sides of the molecules (Fig. 8(a) and (b)).
The phenyl group is twisted out of the plane of the hetero-
cyclic-quinol skeleton by 33.21, which is large compared to the
case of 3a. The value of torsion angle of 7 in the crystalline
state is smaller than that of the optimized geometries of 7 (49.11
in Table 3) by MOPAC/AM1 calculations. As shown in
Fig. 8(c) and (d), the p-stacking between a pair of enantiomers
is observed between the acceptor units of imidazoanthraquinol
moiety. There are 16 short interatomic p–p contacts of less
than 3.6 A in the pair of enantiomers. The interplanar distance
between the imidazoanthraquinole plates is ca. 3.45 A, suggest-
ing a strong offset-like p–p stacking.17 Considering the strong
solid-emissive properties of 7, such an offset-like p-stacking
may not cause a significant fluorescence quenching. The fixa-
tion of the tautomeric form by the N-butylation to produce 7
having a favourable structure for a donor–acceptor conjuga-
tion system is considered the second reason for the improve-
ment of the solid-emissive properties.
We have further found that the fluorophore 2 undergo a
dramatic fluorescence enhancement behaviour upon enclathra-
tion of various kinds of organic solvent molecules. The details
of the solid-state fluorescence enhancement behaviour will be
reported in this series.
Experimental
Melting points were measured with a Yanaco micro melting
point apparatus MP-500D. IR spectra were recorded on a
JASCO FT/IR-5300 spectrophotometer for samples in KBr
pellet form. Absorption spectra were observed with a JASCO
U-best30 spectrophotometer and fluorescence spectra were
measured with a JASCO FP-777 spectrophotometer. Single-
crystal X-ray diffraction was performed on Rigaku AFC7S
diffractometer. Absorption spectra were measured with U-
best-30 spectrophotometer. For the measurement of the so-
lid-state fluorescence excitation and emission spectra of the
crystals, a JASCO FP-777 spectrometer equipped with a
JASCO FP-1060 attachment was used. The fluorescence quan-
tum yields (F) were determined using 9,10-diphenylanthracene
(F ¼ 0.67, lex ¼ 357 nm)18 in benzene as the standard.
Elemental analyses were recorded on a Perkin Elmer 2400 II
CHN analyzer. 1H NMR spectra were recorded on
a
JNM-LA-400 (400 MHz) FT NMR spectrometer with tetra-
methylsilane (TMS) as an internal standard. Column chroma-
tography was performed on silica gel (KANTO CHEMICAL,
60N, spherical, neutral) or alumina (WAKO, about 300 mesh).
Semi-empirical molecular orbital (MO) calculations were
Conclusion
We have developed novel imidazoanthraquinol fluorophores
that undergo tautomerism on the imidazole ring. Intense solid-
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6
453

View Article Online
2-[(4-Diethylamino)phenyl]-11-butyl-11-hydroxyimidazo
[5,4-a]-anthracen-6(11H)-one (2b)
performed on FUJITSU FMV-ME4/657 by using the Win-
MOPAC Ver. 3 package (Fujitsu, Chiba, Japan).
166–167 1C (decomposition); IR (KBr)/cmꢀ1 3435 (NH), 1641
1
(C O); H NMR(DMSO, TMS) d ¼ 0.51 (3H, t), 0.60 (2H,
Q
m), 0.88 (2H, m), 1.15 (6H, t), 2.12 (2H, m), 3.44 (4H, q), 6.67
(1H, s), 6.84 (2H, d, J ¼ 8.5 Hz), 7.55 (1H, t, J ¼ 7.3 Hz), 7.59–
7.61 (1H, m), 7.77 (1H, t, J ¼ 7.3 Hz), 7.96 (2H, d, J ¼ 8.5 Hz),
8.04 (1H, d, J ¼ 8.8 Hz), 8.13–8.15 (1H, m), 8.20 (1H, d,
J ¼ 8.8 Hz), 11.95 (1H, br). (Found: C, 76.59; H, 6.75; N, 9.11.
C29H31N3O2 requires: C, 76.79; H, 6.89; N, 9.26%).
Synthesis of 2-[(4-diethylamino)phenyl]imidazo
[5,4-a]anthraquinone (1)
To a solution of p-diethylaminobenzaldehyde (2.23 g, 12.6
mmol) and Cu(OCOCH3)2 (4.58 g, 25.2 mmol) in acetic acid
(100 ml) was add dropwise a solution of 1,2-diaminoanthra-
quinone (3.00 g, 12.6 mmol) in acetic acid (100 ml) with stirring
at 90 1C. After further stirring for 2 h, the solvent was removed
and the black residue was extracted with CHCl3. The organic
extract was washed with water, dried and concentrated. The
2-[(4-Diethylamino)phenyl]-6-butyl-6-hydroxyimidazo
[5,4-a]anthracen-11(6H)-one (3b)
deep red residue was chromatographed on silica gel (CH2Cl2
:
1
Mp 185–187 1C; IR (KBr)/cmꢀ1 3445 (NH), 1647 (C O); H
Q
ethyl acetate ¼ 3 : 1 as eluent) to give 1 (3.83 g, yield 77%); m.p.
NMR (CD3COCH3, TMS) d ¼ 0.58 (3H, t), 0.64 (2H, m), 1.00
(2H, m), 1.21 (6H, t), 2.11 (2H, m), 3.49 (4H, q), 5.18 (1H, s),
6.83 (2H, d, J ¼ 8.5 Hz), 7.52 (1H, t, J ¼ 7.8 Hz), 7.74 (1H, t,
J ¼ 7.8 Hz), 7.76–7.79 (1H, m), 7.89–7.92 (1H, m), 8.02–8.04
(1H, m), 8.17 (2H, d, J ¼ 8.5 Hz), 8.20–8.22 (1H, m), 11.55
(1H, br). (Found: C, 76.51; H, 6.85; N, 9.21. C29H31N3O2
requires: C, 76.79; H, 6.89; N, 9.26%).
228–229 1C; IR(KBr)/cmꢀ1 3439 (NH), 1606 (C O); 1H
Q
NMR (CDCl3/TMS) d ¼ 1.24 (6H, t), 3.46 (4H, q), 6.77
(2H, d, J ¼ 9.0 Hz), 7.77–7.80 (2H, m), 7.98 (2H, d, J ¼ 9.0
Hz), 8.01 (1H, d, J ¼ 8.3 Hz), 8.19 (1H, d, J ¼ 8.3 Hz),
8.25–8.28 (1H, m), 8.32-8.34 (1H, m), 11.08 (1H, br) (Found:
C, 76.06; H, 5.32; N, 10.33. C25H21N3O2 requires C, 75.93;
H, 5.37; N, 10.63%).
Synthesis of 2-[(4-diethylamino)phenyl]-6-hydroxy-6-phenyl-
imidazo[5,4-a]-anthracen-11(6H)-one (3c)
Synthesis of isomeric quinols 2a–2b and 3a–3c by the reaction
of 1 with organolithium or Grignard reagents
Mp 226–230 1C; IR (KBr)/cmꢀ1 3439 (NH), 1643 (C O); H
1
Q
NMR (CDCl3, TMS) d ¼ 1.15 (6H, t), 3.44 (4H, q), 6.77 (2H,
d, J ¼ 8.5 Hz), 6.95 (1H, s), 7.08–7.11 (1H, m), 7.19–7.23 (2H,
m), 7.30–7.32 (2H, m), 7.36 (1H, d, J ¼ 8.3 Hz), 7.52 (1H, t,
J ¼ 7.8 Hz), 7.63 (1H, t, J ¼ 7.8 Hz), 7.64 (1H, d, J ¼ 7.8 Hz),
7.82 (1H, d, J ¼ 8.3 Hz), 8.18 (2H, d, J ¼ 8.5 Hz), 8.22 (1H, d,
J ¼ 7.8 Hz), 12.43 (1H, Br). (Found: C, 76.47; H, 5.66; N,
8.57. C31H27N3O2 requires C, 78.62; H, 5.75; N, 8.87%).
General procedure. To a THF solution (200 ml) of 1 under an
Ar atmosphere was added ethereal solution of organolithium
(RLi: MeLi, BuLi and PhLi) or MeMgBr at ꢀ108 1C 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 alumina (CH2Cl2 as eluent). The column
chromatography gave 1 and a mixture of 2 and 3. The mixture
was chromatographed on silica gel (CH2Cl2 : AcOEt ¼ 3 : 1 as
eluent) to give 2 as an orange powder, 3 as a brown-red
powder. The yields of 2 and 3 and the recovery of 1 are shown
in Table 1.
Synthesis of 3-butyl-2-[(4-diethylamino)phenyl]-3H-anthra
[1,2-a]imidazole-6,11-dione (5)
To a solution of 1,2-diaminoanthraquinone (5.0 g, 21 mmol),
N-methyl pyrrolidone (80 ml), and sodium carbonate (25 ml)
was added dropwise a solution of butyl iodide (11.58 g, 63
mmol) in N-methyl pyrrolidone (30 ml) with stirring at 90 1C.
After further stirring for 3 h at the same temperature, to the
reaction mixture was added water, then a black-purple pre-
cipitate was obtained, which was separated by filtration and
recrystallized from pyridine–water to give 1-amino-2-butyl-
amino-anthraquinone (4) (4.12 g, 66%).
2-[(4-Diethylamino)phenyl]-11-hydroxy-11-methylimidazo
[5,4-a]-anthracen-6(11H)-one (2a)
To a solution of p-diethylaminobenzaldehyde (2.23 g, 12.6
mmol) and Cu(OCOCH3)2 (4.58 g, 25.2 mmol) in acetic acid
(100 ml) was added dropwise the above compound (4) (3.71 g,
12.6 mmol) in acetic acid solution (100 ml) with stirring at
90 1C. After further stirring for 2 h at the same temperature,
the solvent was removed and the red-brown residue was
extracted with CH2Cl2. The organic extract was washed with
water, dried and concentrated. The red residue was chromato-
graphed on silica gel (CH2Cl2 : ethyl acetate ¼ 3 : 1 as eluent) to
give 5 (4.38 g, yield 77%): mp 145–146 1C; IR (KBr)/cmꢀ1 1608
178–180 1C (decomposition); IR (KBr)/cmꢀ1 3445 (NH), 3223
(OH), 1647(C O); 1H NMR (CDCl , TMS) d ¼ 1.09 (6H, t),
Q
3
1.79 (3H, q), 3.38 (4H, q), 6.59 (1H, s), 6.74 (2H, d, J ¼ 9.0 Hz),
7.38–7.45 (1H, m), 7.47 (1H, d, J ¼ 8.5 Hz), 7.60–7.64 (1H, m),
7.94 (1H, d, J ¼ 8.5 Hz), 7.95 (1H, d, J ¼ 0.73 Hz), 7.99 (2H,
d, J ¼ 9.0 Hz), 8.09 (1H, d, J ¼ 0.73 Hz) (Found: C, 75.89; H,
6.29; N, 10.31. C26H25N3O2 requires C, 75.89; H, 6.12;
N, 10.21%).
(C O); 1H NMR (DMSO/TMS) d ¼ 0.82 (3H, t), 1.15 (6H, t),
Q
1.20–1.26 (2H, m), 1.70–1.74 (2H, m), 3.44 (4H, q), 4.40 (2H,
t), 6.86 (2H, d, J ¼ 9.0 Hz), 7.71 (2H, d, J ¼ 8.8 Hz), 7.85–7.92
(2H, m), 8.07–8.18 (4H, m). (Found: C, 76.96; H, 6.62; N, 9.33.
C29H29N3O2 requires: C, 77.13; H, 6.47; N, 9.31%).
2-[(4-Diethylamino)phenyl]-6-hydroxy-6-methylimidazo
[5,4-a]anthracen-11(6H)-one (3a)
Mp 223–224 1C; IR (KBr)/cmꢀ1 3435 (NH), 3207 (OH), 1647
1
(C O); H NMR (CD COCD , TMS) d ¼ 1.08 (6H, t), 1.60
Q
3
3
(3H, s), 3.38 (4H, q), 4.96 (1H, s), 6.73 (2H, d, J ¼ 9.0 Hz), 7.41
(1H, td, J ¼ 1.2 and 6.6 Hz), 7.63 (1H, td, J ¼ 1.2 and 6.6 Hz),
7.69–7.71 (1H, m), 7.80–7.82 (1H, m), 7.95–7.97 (1H, m), 8.08
(2H, d, J ¼ 9.0 Hz), 8.09–8.11 (1H, m), 11.46 (1H, Br). (Found:
C, 76.07; H, 6.20; N, 10.17. C26H25N3O2 requires: C, 75.89; H,
6.12; N, 10.21%).
Synthesis of isomeric quinols 6 and 7 by the reaction of 5
with methyllithium
To a THF solution (400 ml) of 5 under an Ar atmosphere was
added 1.0 equivalent of an ethereal solution of methyllithium
at ꢀ108 1C over 30 min. During the course of addition, the red
454
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6

View Article Online
solution turned to a reddish brown suspension. After stirring
for 30 min, the reaction was quenched with saturated aqueous
NH4Cl. The solvent was evaporated and the residue was
extracted with CH2Cl2. The organic extract was washed with
water. The CH2Cl2 solvent was evaporated and the residue was
chromatographed on alumina (CH2Cl2 as eluent). The column
chromatography gave 5 and a mixture of 6 and 7. The mixture
was further chromatographed on silica gel (CH2Cl2 : ethyl
acetate ¼ 3 : 1 as eluent) to give 6 (30%) as a yellowish green
powder, 7 (43%) as a yellow powder.
crystallographic software package of Molecular Structure
Corporation.
Crystal structure determination of compound 2a
Crystals of 2a were recrystallized from dichloromethane–
n-hexane as air stable orange prisms. The one selected had
approximate dimensions 0.45 ꢂ 0.25 ꢂ 0.45 mm. The transmis-
sion factors ranged from 0.97 to 1.00. The crystal structure was
solved by direct methods using SIR 92.20 The structures were
expanded using Fourier techniques.21 The non-hydrogen
atoms were refined anisotropically. Some hydrogen atoms were
refined isotropically, the rest were fixed geometrically and not
refined.
3-Butyl-2-[(4-diethylamino)phenyl)]-11-hydroxy-11-methyl-1H,
11H-anthra[1,2-a]imidazol-6-one (6)
1
Mp 167–168 1C; IR (KBr)/cmꢀ1 3061 (OH), 1608 (C O); H
Q
NMR (DMSO/TMS) d ¼ 0.83 (3H, t), 1.15 (6H, t), 1.23–1.29,
(2H, m), 1.74–1.77 (2H, m), 1.89 (3H, s), 3.43 (4H, q), 4.39(2H,
t), 6.41(1H, s), 6.85 (2H, d, J ¼ 9.0 Hz), 7.54 (1H, t, J ¼ 7.1
Hz), 7.68 (2H, d, J ¼ 9.0 Hz), 7.77 (1H, t, J ¼ 7.1 Hz), 7.78
(1H, d, J ¼ 8.5 Hz), 7.98 (1H, d, J ¼ 7.1 Hz), 8.05 (1H, d, J ¼
8.5 Hz), 8.13–8.15 (1H, m). (Found: C, 76.93; H, 7.19; N, 8.99.
C30H33N3O2 requires: C, 77.06; H, 7.11; N, 8.99%).
Crystal data. C26H25N3O2,
M
¼
411.50, monoclinic,
a ¼ 11.111(2), b ¼ 16.954(2), c ¼ 12.318(2) A, b ¼ 113.97(1)1,
U ¼ 2120.3(5) A3, T ¼ 296.2 K, space group P21/c (no. 14),
Z ¼ 4, m(Mo-Ka) ¼ 0.8 cmꢀ1, 3936 reflections measured, 3735
unique (Rint ¼ 0.020) which were used in all calculations. The
final R indices [I 4 2s(I)], R1 ¼ 0.0623, wR(F2) ¼ 0.1457.
Crystal structure determination of compound 3a
3-Butyl-2-[(4-diethylamino)phenyl)]-6-hydroxy-6-methyl-3H,
6H-anthra[1,2-a]imidazol-11-one (7)
Crystals of 3a were recrystallized from dichloromethane–
n-hexane as air stable orange-brown prisms. The one selected
had approximate dimensions 0.30 ꢂ 0.45 ꢂ 0.25 mm. The
transmission factors ranged from 0.98 to 1.00. The crystal
structure was solved by direct methods using SIR 92.20 The
structures were expanded using Fourier techniques.21 The non-
hydrogen atoms were refined anisotropically. Some hydrogen
atoms were refined isotropically, the rest were fixed geometri-
cally and not refined.
Mp 228–230 1C; IR (KBr)/cmꢀ1 3443 (OH), 1607 (C O);
Q
1HNMR (DMSO/TMS) d ¼ 0.81 (3H, t) 1.15 (6H, t), 1.21 (2H,
m), 1.58 (3H, s), 1.71 (2H, m), 3.43 (4H, q), 4.35 (2H, t), 6.17
(1H, s), 6.83 (2H, d, J ¼ 9.0 Hz), 7.48–7.51 (1H, m), 7.64 (2H,
d, J ¼ 9.0 Hz), 7.67-7.71 (1H, m), 7.82 (1H, d, J ¼ 8.5 Hz), 7.94
(1H, d, J ¼ 8.5 Hz), 7.95–7.97 (1H, m), 8.03–8.05 (1H, m).
(Found: C, 76.80; H, 7.17; N, 8.82. C30H33N3O2 requires: C,
77.06; H, 7.11; N, 8.99%).
Crystal data. C26H25N3O2, M ¼ 411.50, orthorhombic,
a ¼ 13.405(6), b ¼ 10.911(2), c ¼ 14.405(3) A, U ¼ 2106(1) A3,
T ¼ 296.2 K, space group Pna21 (no.33), Z ¼ 4, m(Mo-Ka) ¼
0.8 cmꢀ1, 2758 reflections measured, 2516 unique (Rint ¼ 0.000)
which were used in all calculations. The final R indices [I 4 2s
(I)], R1 ¼ 0.0424, wR(F2) ¼ 0.0987.
Computational methods
All calculations were performed on FUJITSU FMV-ME4/657.
The semi-empirical calculations were carried out with the
WinMOPAC Ver. 3 package (Fujitsu, Chiba, Japan). Geome-
try calculations in the ground state were carried out using the
AM1 method.10 All geometries were completely optimized
(keyword PRECISE) by the eigenvector following routine
(keyword EF). Experimental absorption spectra of the seven
quinol derivatives were studied with the semi-empirical method
INDO/S (intermediate neglect of differential overlap/spectro-
scopic).9 All INDO/S calculations were performed using single
excitation full SCF/CI (self-consistent field/configuration inter-
action), which includes the configuration with one electron
excited from any occupied orbital to any unoccupied orbital,
225 configurations were considered for the configuration inter-
action [keyword CI (15 15)].
Crystal structure determination of compound 6
Crystals of 6 were recrystallized from ethanol as air stable
yellowish green prisms. The one selected had approximate
dimensions 0.60 ꢂ 0.20 ꢂ 0.40 mm. The transmission factors
ranged from 0.92 to 0.99. The crystal structure was solved by
direct methods using SIR 92.20 The structures were expanded
using Fourier techniques.21 The non-hydrogen atoms were
refined anisotropically. Some hydrogen atoms were refined
isotropically, the rest were fixed geometrically and not refined.
Crystal data. C30H33N3O2, M ¼ 467.61, monoclinic, a ¼
16.130(3), b ¼ 8.793(3), c ¼ 18.260(3) A, b ¼ 96.12(1)1,
U ¼ 2575.1(9) A3, T ¼ 296.2 K, space group P21/c (no. 14),
Z ¼ 4, m(Mo-Ka) ¼ 0.8 cmꢀ1, 4697 reflections measured, 4696
unique (Rint ¼ 0.017) which were used in all calculations. The
final R indices [I 4 2s(I)], R1 ¼ 0.0439, wR(F2) ¼ 0.1093.
X-ray crystallographic studies y
The reflection data were collected at 23 ꢃ 1 1C on a Rigaku
AFC7S four-circle diffractometer by 2y-o scan technique, and
using graphite-monochromated Mo-Ka (l ¼ 0.710 69 A)
radiation at 50 kV and 30 mA. In all case, the data were
corrected for Lorentz and polarization effects. A correction for
secondary extinction was applied. Crystal data, data collection
and refinement parameters are summarized in Table S1. The
reflection intensities were monitored by three standard reflec-
tions for every 150 reflections. An empirical absorption correc-
tion based on azimuthal scans of several reflections was
applied. All calculations were performed using the teXsan19
Crystal structure determination of compound 7
Crystals of 7 were recrystallized from ethanol as air stable
yellow prisms. The one selected had approximate dimensions
0.20 ꢂ 0.10 ꢂ 0.20 mm. The transmission factors ranged from
0.93 to 1.00. The crystal structure was solved by direct methods
using SIR 92.20 The structures were expanded using Fourier
techniques.21 The non-hydrogen atoms were refined aniso-
tropically. Some hydrogen atoms were refined isotropically,
the rest were fixed geometrically and not refined.
y CCDC reference numbers 236773–236776. See http://www.rsc.org/
suppdata/nj/b4/b410311d/ for crystallographic data in .cif or other
electronic format.
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6
455

View Article Online
Y. Ooyama, S. Tanikawa and S. Watanabe, J. Chem. Soc., Perkin
Trans. 2, 2002, 708–714.
C. J. Tonzola, M. M. Alam, W. K. Kaminsky and S. A. Jenekhe,
J. Am. Chem. Soc., 2003, 125, 13548.
E. Horiguchi, S. Matsumoto, K. Funabiki and M. Matui, Chem.
Lett., 2004, 170.
K. Yoshida, J. Yamazaki, Y. Tagashira, H. Miyazaki and
S. Watanabe, Chem. Lett., 1996, 9.
K. Yoshida, T. Tachikawa, J. Yamasaki, S. Watanabe and
S. Tokita, Chem. Lett., 1996, 1027.
(a) J. E. Ridley and M. C. Zerner, Theor. Chim. Acta, 1973, 32,
111; (b) J. E. Ridley and M. C. Zerner, Theor. Chim. Acta, 1976,
42, 223; (c) A. D. Bacon and M. C. Zerner, Theor. Chim. Acta,
1979, 53, 21.
Crystal data. C30H33N3O2, M ¼ 467.61, monoclinic, a ¼
12.007(3), b ¼ 13.152(4), c ¼ 16.196(5) A, b ¼ 102.99(2)1, U ¼
2492(1) A3, T ¼ 296.2 K, space group P21/n (no.14), Z ¼ 4,
m(Mo-Ka) ¼ 0.8 cmꢀ1, 4766 reflections measured, 4390 unique
(Rint ¼ 0.095) which were used in all calculations. The final R
indices [I 4 2s(I)], R1¼0.0763, wR(F2) ¼ 0.1490.
5
6
7
8
9
Acknowledgements
This work was partially supported by Regional Science Pro-
motion (RSP) program by the Ministry of Education, Culture,
Sports, Science and Technology (MEXT), Japan. Y.O. was
supported by a research fellowships from the Japan Society for
the Promotion of Science (JSPS) for young scientists.
10 M. J. S. Dewar, E. G. Zoebisch, E. F. Healy and J. J. Stewart,
J. Am. Chem. Soc., 1985, 107, 389.
11 M. Adachi, Y. Murata and S. Nakamura, J. Org. Chem., 1993, 58,
5238.
12 W. M. F. Fabian, S. Schuppler and O. S. Wolfbesis, J. Chem. Soc.,
Perkin Trans. 2, 1996, 853.
13 (a) J. Aihara, G. Kushibiki and Y. Matsunaga, Bull. Chem. Soc.
Jpn., 1973, 46, 3584; (b) J. Aihara, Bull. Chem. Soc. Jpn., 1974, 47,
2063.
14 G. R. Desiraju, I. C. Paul and D. Y. Curtin, J. Am. Chem. Soc.,
1977, 99, 1594.
References
1
(a) C. W. Tang and S. A. VansSlyke, Appl. Phys. Lett., 1987, 51,
913; (b) C. W. Tang, S. A. VansSlyke and C. H. Chen, J. Appl.
Phys., 1989, 65, 3610; (c) J. Schi and C. W. Tang, Appl. Phys.
Lett., 1997, 70, 1665; (d) K. Koller, Appl. Fluorescence Technol.,
15 M. Tanaka, H. Hayashi, S. Matsumoto, S. Kashino and K. Mogi,
Bull. Chem. Soc. Jpn., 1997, 70, 329.
16 K. Yoshida, K. Uwada, H. Kumaoka, L. Bu and S. Watanabe,
Chem. Lett., 2001, 808.
17 M. Cotrait, P. Marsau, L. Kessab, S. Grelier, A. Nourmamode
and A. Castellan, Aust. J. Chem., 1994, 47, 423.
18 C. A. Heller, R. A. Henry, B. A. Mclaughlin and D. E. Bills,
J. Chem. Eng. Data, 1974, 19, 214.
19 teXsan: Crystal Structure Analysis Package, Molecular Structure
Corporation, The Woodlands, TX, 1985 and 1992.
20 A. Altomare, M. C. Burla, M. Camalli, M. Cascarano, C.
Giacovazzo, A. Guagliardi and G. Polidori, J. Appl. Cryst.,
1994, 27, 435.
¨
1989, 1, 1; (e) A. Kraft, A. C. Grimsdale and A. B. Holmes,
Angew. Chem. Int. Ed., 1998, 37, 402; (f) R. H. Friend, R. W.
Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani,
¨
D. D. C. Bradley, D. A. DosSantos, J. L. Bredas, M. LOgdlund
´
and W. R. Salaneck, Nature, 1999, 397, 121; (g) U. Mitschke and
P. Bauerle, J. Mater. Chem., 2000, 10, 1471; (h) K. Hirano, S.
¨
Minakata and M. Komatsu, Chem. Lett., 2001, 8; (i) K. Hirano,
Y. Oderaotoshi, S. Minakata and M. Komatsu, Chem. Lett., 2001,
1262.
2
3
H.-J. Knolker, R. Boese and R. Hitzemann, Chem. Ber., 1990,
123, 327.
¨
(a) K. Shirai, A. Yanagizawa, H. Takahashi, K. Fukunishi and M.
Matsuoka, Dye Pigm., 1998, 39, 49–68; (b) J. H. Kim, S. R. Shin,
M. Matsuoka and K. Fukunishi, Dye Pigm., 1998, 39, 341–357.
(a) K. Yoshida, Y. Ooyama, H. Miyazaki and S. Watanabe,
J. Chem. Soc., Perkin Trans. 2, 2002, 700–707; (b) K. Yoshida,
21 DIRDIF94. P. T. Beurskens, G. Admiraal, G. Beurskens, W. P.
Bosman, R. de Gelder, R. Israel and J. M. M. Smits, The
DIRIF94 program system, Technical Report of the Crystallogra-
phy Laboratory, University of Nijmegen, The Netherlands, 1994.
4
456
N e w J . C h e m . , 2 0 0 5 , 2 9 , 4 4 7 – 4 5 6