Synthesis, crystal structure and photoluminescence of 2,6-dimethylanthracene and its pseudo-triptycene derivatives

Article abstract of DOI:10.1016/j.molstruc.2009.10.017

A simple one-step synthesis of 2,6-dimethylanthracene, 1, in high yield is reported utilizing the easily accessible benzyl alcohol as the starting material. Based on 2,6-dimethylanthracene, two pseudo-triptycene compounds, cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-α,β-succinic anhydride, 2, and cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-α,β-succinyl amine, 3, are firstly synthesized in high yield and they are characterized by single crystal X-ray diffraction. Compound 2 crystallizes in triclinic P over(1, ?) space group and compound 3 crystallizes in monoclinic P2₁/c space group. Both compound 2 and 3 exhibit cis-configurations and endo-conformations. Compound 1 exhibits very intense photoluminescence property due to the delocalized electron in the whole molecule, whereas fluorescence quench happens to some extents due to the destruction of the conjugated structure in compound 2.

Full text of DOI:10.1016/j.molstruc.2009.10.017

Journal of Molecular Structure 963 (2010) 76–81
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, crystal structure and photoluminescence of 2,6-dimethylanthracene
and its pseudo-triptycene derivatives
a,b,*
a
a
a
b
Yun Gong
, Yuchao Zhou , Jianbo Qin , Jinghua Li , Rong Cao
a
Department of Chemistry, College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, PR China
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 July 2009
Received in revised form 3 October 2009
Accepted 10 October 2009
Available online 14 November 2009
A simple one-step synthesis of 2,6-dimethylanthracene, 1, in high yield is reported utilizing the easily
accessible benzyl alcohol as the starting material. Based on 2,6-dimethylanthracene, two pseudo-tripty-
cene compounds, cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-
cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo- ,b-succinyl amine, 3, are firstly synthesized in
high yield and they are characterized by single crystal X-ray diffraction. Compound 2 crystallizes in tri-
a,b-succinic anhydride, 2, and
a
ꢀ
1
clinic P1 space group and compound 3 crystallizes in monoclinic P2 /c space group. Both compound 2
Keywords:
and 3 exhibit cis-configurations and endo-conformations. Compound 1 exhibits very intense photolumi-
nescence property due to the delocalized electron in the whole molecule, whereas fluorescence quench
happens to some extents due to the destruction of the conjugated structure in compound 2.
Ó 2009 Elsevier B.V. All rights reserved.
2
,6-Dimethylanthracene
One-pot synthesis
Pseudo-triptycene
Crystal structure
Photoluminescence
1
. Introduction
Polycyclic aromatic hydrocarbons (PAHs), such as anthracene
rich property, has been found to be a useful building block for the
construction of novel receptors and porous structures [21–25]. The
constrained 120° angle between the phenyl rings and the shape of
triptycene hinders itself packing into dense structures. So this type
of compounds exhibit high chemical and thermal stability and can
be used to remove organic impurities from contaminated water
(such asparaquat derivatives) and has potential application in
environmental protection. However, pseudo-triptycene, 9,10-dihy-
are fused ring aromatic compounds. They are one of key com-
pounds for optical materials with a UV–vis light emission due to
the delocalized
investigated as electroluminescence (EL) devices [1,2], fluores-
cence materials [3,4] and chemosensors [5]. Alkyl group is elec-
tron-donating group, and alkyl-substituted anthracenes have
attracted researchers’ interests due to its inductive and hypercon-
jugative effects. The hyperconjugative effect is defined as the con-
jugation of alkyl groups with a multiple bond [6–8]. On the basis of
p electron in the aromatic system and have been
droanthracene-9,10-a,b-succinic compound with similar 3D struc-
ture and unique flexible C–C framework, is rarely explored. Herein,
we firstly report the syntheses and crystal structures of two novel
pseudo-triptycene compounds, cis-2,6-dimethyl-9,10-dihydroan-
molecular orbital theory, the methyl group, due to its higher
p
thracene-9,10-endo-
9,10-dihydroanthracene-9,10-endo-
a
,b-succinic anhydride, and cis-2,6-dimethyl-
,b-succinyl amine in high
symmetry, can conjugate more effectively with the orbitals of
p
a
multiple bonds than other alkyl groups, and this combination
allows a flow of electrons between the methyl group and the aro-
matic ring. So it is expected that methyl-substituted anthracenes,
such as 2,6-dimethylanthracene, and their derivatives to exhibit
good fluorescence properties. However, so far, the synthesis of
yield, utilizing 2,6-dimethylanthracene as starting material. Com-
pounds 2 and 3 are characterized by single crystal X-ray diffrac-
tion. The photoluminescence property has been reported.
2
. Experimental
2
,6-dimethylanthracene is complicated and usually involved
multi-step reactions [9–17], and some reactions are involved poi-
sonous chemicals [18] and much side products.
2.1. Synthesis and characterization
Triptycene [19,20], which is a class of compounds with a unique
propeller-like three dimensional (3D) rigid structure and electron-
All chemicals purchased were of reagent grade and used with-
out further purification. C, H, N elemental analyses were performed
on Perkin-Elmer 240c elemental analyzer. Infrared spectra were
recorded as KBr pellets on a Nicolet 170SXFT/IR spectrometer.
Excitation and emission spectra were obtained on a Spex FL-2T2
spectrofluorometer equipped with a 450 W xenon lamp as the
*
Corresponding author. Address: Department of Chemistry, College of Chemistry
and Chemical Engineering, Chongqing University, Chongqing 400044, PR China.
Tel./fax: +86 023 67577410.
E-mail address: gongyun7211@yahoo.com.cn (Y. Gong).
0
022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.10.017

Y. Gong et al. / Journal of Molecular Structure 963 (2010) 76–81
77
excitation source. The melting point was determined using an
uncorrected X-4 melting point apparatus of Beijing Kaifu Company.
H spectra were recorded on a Bruker 500 MHz apparatus with tet-
ramethylsilane (TMS) as internal standard. All measurements were
performed at room temperature.
been shown to have no effect on the anhydride). The mixture
was filtered and the bicarbonate-insoluble residue (the anhydride)
was washed with water (3ꢀ 100 mL). Colorless block crystals were
obtained when recrystallized from benzene (yield: ca. 98% based
1
38 6
on 2,6-dimethylanthracene). Elemental Anal. Calcd. for C46H O :
1
C, 80.45; H, 5.58%. Found: C, 80.29; H, 5.10%. H NMR (in
DMSO-d ): d, 2.24 (s, 6H), 3.61 (d, 2H, J = 3.0 Hz), 4.75 (d, 2H,
J = 3.0 Hz), 6.97 (t, 2H, J = 7.0 Hz), 7.18 (d, 2H, J = 7.5 Hz), 7.32 (d,
2.2. Synthesis of 2,6-dimethylanthracene, 1
6
ꢁ1
To dry toluene (240 mL), benzyl alcohol (14 g, 0.14 mol) was
2H, J = 7.5 Hz). Melting point (170–171 °C). IR (cm ): 3855(w),
3650(w), 2960(s), 2369(w), 1863(m), 1778(s), 1618(w), 1484(m),
1459(w), 1381(w), 1324(w), 1290(w), 1225(s), 1204(m), 1190
(m), 1135(w), 1073(s), 976(m), 952(s), 931(s), 920(s), 841(w),
814(m), 791(m), 767(w), 741(w), 624(m), 533(s).
added dropwise in an ice-bath while stirring. AlCl
3
(51.98 g,
0
.385 mol) was then added in one lot. The reaction mixture was
heated on an oil-bath at 110 °C for 3 h. Then it was cooled, decom-
posed with crushed ice (45 g), water (100 mL) and concentrated
HCl (65 mL). The mixture was filtered and the residual was washed
with water (3ꢀ 90 mL), ethyl acetate (3ꢀ 40 mL), saturated NaH-
CO
3
solution (2ꢀ 40 mL) and water (3ꢀ 90 mL) and dried at
2.4. Synthesis of cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-
8
0 °C in vacuum for 2 h (yield: ca. 60% based on benzyl alcohol).
Elemental Anal. Calcd. for C16 14: C, 93.20; H, 6.80%. Found: C,
3.59; H, 6.68%. H NMR (in CDCl ): d, 2.52 (s, 6H), 7.26 (d, 2H,
J = 8.5 Hz), 7.71 (s, 2H), 7.87 (d, 2H, J = 8.5 Hz), 8.25 (s, 2H). Melting
a,b-succinyl amine, 3
H
1
9
3
An aqueoussolution(10 mL)of compound 2 (0.05 mmol, 0.014 g)
was adjusted to pH 6 by 2 N aqueous ammonia solution, then trans-
ferred into a Teflon-lined autoclave. The reaction mixture was
heated at 120 °C for 2 h, then followed by slow cooling to room tem-
perature. The resulting colorless crystals were filtered off and
washed with distilled water (yield: ca. 98% based on cis-2,6-
ꢁ1
point (241–242 °C). IR (cm ): 2909(s), 1633(s), 1539(m), 1455(s),
1
376(m), 1307(m), 1272(w), 1171(w), 1036(w), 962(s), 916(m),
8
94(s), 790(s), 767(w), 742(w), 599(w), 476(s).
2
a
.3. Synthesis of cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-
,b-succinic anhydride, 2
dimethyl-9,10-dihydroanthracene-9,10-endo-
dride). Elemental Anal. Calcd. for C20 N: C, 79.19; H, 5.65; N,
3
.61%. Found: C, 79.45; H, 5.33; N, 4.63%. H NMR (in CDCl ): d,
a,b-succinic anhy-
17 2
H O
1
4
A solution of 3.227 g (0.0157 mol) of 2,6-dimethylanthracene
2.28 (s, 6H), 3.23 (d, 2H, J = 3.0 Hz), 4.67 (d, 2H, J = 3.0 Hz), 6.95 (t,
2H, J = 7.0 Hz), 7.17 (d, 2H, J = 7.5 Hz), 7.22 (d, 2H, J = 7.5 Hz), 7.35
(s, 1H). Melting point (180–181 °C). IR (cm ): 3272(m), 1779(m),
1721(s), 1699(s), 1483(m), 1358(m), 1167(m), 994(m), 825(m),
812(m), 631(m), 616(m), 535(m), 418(w).
and 5.451 g (0.0471 mol) of maleic acid in 50 mL of dioxane was
refluxed for 30 h. The dioxane was removed in a current of air on
a steam-bath and the residue was shaken for 2 h at room temper-
ature with excess, dilute sodium bicarbonate (this treatment had
ꢁ1
Table 1
Crystal data and structure refinements for compounds 2 and 3.
Compound
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
2
C
3
43
H
32
O
6
20 2
C H16NO
644.69
298(2)
0.71073
Triclinic
P1ꢀ
302.34
298(2)
0.71073
Monoclinic
P2 /c
1
9.4720(10)
12.7619(18)
b (Å)
12.8081(14)
9.4138(14)
c (Å)
14.2639(17)
13.688(2)
a
(°)
b (°)
(°)
89.475(2)
85.0550(10)
86.1960(10)
1720.2(3)
90
104.862(2)
90
1589.4(4)
c
3
Volume (Å )
Z
q
2
4
calc (mg m 3
ꢁ
)
1.245
0.082
1.263
0.082
Absorption coefficient (mmꢁ1)
F(0 0 0)
Crystal size (mm )
h range (°)
676
636
3
0.29 ꢀ 0.30 ꢀ 0.42
0.42 ꢀ 0.21 ꢀ 0.12
2.60–25.01
1.65–25.02
Limiting indices
ꢁ10 6 h 6 11, ꢁ15 6 k 6 15, ꢁ14 6 l 6 16
ꢁ13 6 h 6 15, ꢁ11 6 k 6 7, ꢁ16 6 l 6 16
Reflections collected
Independent reflections
Absorption correction
Max. and min. transmission
Refinement method
Data, restraints, parameters
Goodness-of-fit on F2
8764
5756
7672
2803
w
-scan
w-scan
0.977 and 0.971
Full-matrix least-squares on F2
5756, 0, 499
0.990 and 0.980
Full-matrix least-squares on F2
2803, 0, 221
0.945
1.052
Final R indices [I > 2
r
(I)]
R
1
= 0.0988,
wR = 0.2072
= 0.2344,
wR = 0.2641
0.324 and ꢁ0.253
R
1
= 0.0637,
wR = 0.1644
= 0.1440,
wR = 0.2215
0.429 and ꢁ0.223
2
2
R indices (all data)
R
1
R
1
2
2
Largest diff. peak and hole
P
P
½wðF0 ꢁ F Þ ꢂ= ½wðF Þꢂ ꢂ1=2.
2
2
c
2
2
0
2
R
1
=
R
||F
0
| ꢁ |F
c
||/
R
|F
0
|; wR
2
¼

7
8
Y. Gong et al. / Journal of Molecular Structure 963 (2010) 76–81
2.5. X-ray crystallography
3
reaction, in which AlCl acts as catalyst and the possible mechanism
for the ring-closure reaction is expected (Scheme 2) [18]. As shown
in Scheme 2, in the reaction, toluene plays important role in the
preparation of compound 1, it is not only a solvent, but also a starting
material [18], which is proved by the parallel experiments: Under
similar conditions, we replace toluene with p-xylene, the yield of
compound 1 will be decreased dramatically; when m-xylene is used
instead, no product can be obtained. The amount of toluene is not
necessarily very precise, as long as it is excessive. The synthesis is
sensitive to the reaction temperature. When the temperature is low-
er (such as 80 °C, 95 °C) or higher (such as 140 °C), the yield will be
decreased. The reaction time is also important. When the reaction
time is longer than 10 h, no products and a lot of unidentified black
tar will be obtained. In the present work, it is found that the optimal
condition is to reflux at 110 °C for 3–5 h.
The synthesis of compound 2 is a Diels–Alder reaction, in which
compound 1, 2,6-dimethylanthracene, acts as diene and maleic
acid acts as dienophile. As known, Diels–Alder reaction works best
when there is a marked difference between the electron densities
in the diene and the alkene with which it reacts, the dienophile.
Usually the dienophile has electron-attracting groups attached to
it, e.g., electron-attracting carboxylic group, while the diene is elec-
tron rich, e.g., electron-donating methyl group. So the reaction of
2,6-dimethylanthracene with maleic acid is easy to proceed and
the yield of compound 2 is higher than 95%.
3
Single crystals of dimensions 0.29 ꢀ 0.30 ꢀ 0.42 mm for com-
3
pound 2, 0.42 ꢀ 0.21 ꢀ 0.12 mm for compound 3 were used for
structure determination. XRD data of compounds 2 and 3 were col-
lected on a Bruker-AXS CCD area detector-equipped diffractometer
with graphite-monochromatized Mo Ka (k = 0.71073 Å) radiation
at room temperature. A total of 8764 (5756 unique, Rint = 0.0978)
reflections of compound
14 6 l 6 16, 2.60 < h < 25.01) and a total of 7672 (2803 unique,
int = 0.0582) reflections of compound 3 (ꢁ13 6 h 6 15, ꢁ11 6 k
7, ꢁ16 6 l 6 16, 1.65 < h < 25.02) were measured. An empirical
absorption correction from -scan was applied. All the structure
2
(ꢁ10 6 h 6 11, ꢁ15 6 k
6 15,
ꢁ
R
6
w
was solved by direct methods and expanded using Fourier tech-
niques. The nonhydrogen atoms were refined anisotropically.
Hydrogen atoms were added in their calculated positions. All cal-
culations were performed using the SHELXTL-97 program [26–
7]. The CCDC reference numbers are the following: 721286 for 2
and 721767 for 3. Crystal data and structure refinements for com-
pounds 2 and 3 are listed in Table 1.
2
3
. Results and discussion
3
.1. Synthesis
The synthetic routine for compounds 1–3 are shown in Scheme 1.
The synthesis of 2,6-dimethylanthracene, 1, is a Friedel–Crafts
Diels–Alder reaction is a concerted reaction, in which several
bonds in the transition state are simultaneously made and broken.
Scheme 1. The synthetic routine for compounds 1–3.
Scheme 2. The possible mechanism for the formation of compound 2.

Y. Gong et al. / Journal of Molecular Structure 963 (2010) 76–81
79
0
0
When a cyclic diene and a cyclic dienophile react with each other
in the present reaction, more than one stereoisomer may be
formed. Usually two stereoisomers, endo- and exo-conformations
will be obtained. However, the isomer that predominates is the
C(33 ) are disordered over two locations, C(40) and C(40 ) are disor-
dered over two locations. Each site of them is half-occupied. Two
phenyl rings 5, 6 and one five-membered ring 7 are composed of C
atoms from C27 to C32, C34 to C39, and C21, C22, C23, C24, O4,
respectively. The dihedral angles between rings 5 and 6, 5 and 7, 6
and 7 are 121.7°, 176.0° and 58.8°, respectively. Ring 7 is apart from
ring 5, indicating the molecule is also an endo-isomer. Strong
C–Hꢃ ꢃ ꢃC H-bonds are observed between the molecule and solvent
benzene molecule, for example, the H43ꢃ ꢃ ꢃC40B and C43ꢃ ꢃ ꢃC40B dis-
tances are 3.338 and 4.206 Å, respectively, the C43–H43ꢃ ꢃ ꢃC40B an-
gle is 133.5° (atom with additional label B refers to the symmetry
operation: 1 ꢁ x, 2 ꢁ y, 1 ꢁ z), indicating recrystallization from ben-
zene is effective for the separation of the endo-isomer. The H(22)–
C(22)–C(21) and H(23)–C(23)–C(24) bond angles are 110.2° and
endo-conformation which involves maximum overlap of
p elec-
trons in the transition state. Compound 2 is obtained by recrystal-
lizing from benzene. The crystal structure of compound 2 proves
the product is the endo-isomer.
The synthesis of compound 3 is a typical formation reaction of
acyl amine and the reaction is not sensitive to reaction conditions.
Compound 3 can be obtained in high yield without changing the
conformation of reactant. The crystal structure of compound 3
indicates that the acyl amine is also the endo-isomer.
1
10.0°, respectively, indicating the molecule also exhibits
a
3.2. Structure description
cis-configuration.
ꢀ
Because compound 2 is obtained utilizing compound 1 as start-
ing material, the crystal structure of compound 2 proves the
synthesis of methyl-substituted anthracene is accurate and Fri-
edel–Crafts reaction is an effective routine to get polycyclic
aromatic hydrocarbons. Due to the disorder of methyl group in
Compound 2 crystallizes in triclinic P1 space group with two
cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo- ,b-succinic
a
anhydride molecules and one solvent molecule, benzene in the
asymmetric unit. As shown in Fig. 1, in one crystallographically un-
ique 2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-a,b-succinic
anhydride, the substituted methyl group has two positions owing to
0
the crystallographic disorder of C(13) and C(13) . Each of them has
5
0% occupancy over the two positions. Two phenyl rings 1, 2 and
one five-membered ring 3 are composed of C atoms from C14 to
C19, C7 to C12, and C1, C2, C3, C4, O1, respectively. The dihedral an-
gles between rings 1 and 2, 1 and 3, 2 and 3 are 122.3°, 177.0° and
6
0.7°, respectively. Ring 3 is apart from ring 1, indicating it is an
endo-isomer. Strong edge-to-face stacking interactions exist
p–p
between five-membered ring 3 and benzene ring 4, for example,
the dihedral angle between planes 3 and 4 is 115.9 °C and the dis-
tance between C41A and plane 4 is 4.391 Å (atom with additional
label A refers to the symmetry operation: 1 ꢁ x, 2 ꢁ y, 2 ꢁ z), which
indicates that solvent molecule, benzene plays important in the sep-
aration of the endo-isomer from the endo- and exo-mixtures. The
H(2)–C(2)–C(1) and H(3)–C(3)–C(4) bond angles are 109.4° and
1
10.1°, respectively, indicating the molecule exhibits a cis-configu-
ration. In another crystallographically unique 2,6-dimethyl-9,10-
dihydroanthracene-9,10-endo- ,b-succinic anhydride, C(33) and
Fig. 2. ORTEP drawing of compound 3 with the atomic numbering scheme and
displacement ellipsoids at the 30% probability level (H atoms omitted for clarity).
a
Fig. 1. ORTEP drawing of compound 2 with the atomic numbering scheme and displacement ellipsoids at the 30% probability level (H atoms omitted for clarity).

8
0
Y. Gong et al. / Journal of Molecular Structure 963 (2010) 76–81
Scheme 3. Chiral cis-2,7-dimethyl-9,10-dihydroanthracene-9,10-endo-a,b-succinyl amine (a) and nonchiral cis-2,6-dimethyl-9,10-dihydroanthracene-9,10-endo-a,b-
succinyl amine (b), asterisk indicating the chiral centers.
the crystal structure of compound 2, the position of the methyl
group cannot be determined. In order to make sure the two methyl
groups are in 2,6-positions or 2,7-positions, we use compound 2 as
starting material and obtain the crystal structure of compound 3.
Compound 3 is obtained using compound 2 as starting material.
anthracene in compound 2, the characteristic peaks of phenyl rings
in the 920–1618 cm range shift obviously.
ꢁ
1
3.4. UV–visible spectra
Compound 3 crystallizes in monoclinic P2
dimethyl-9,10-dihydroanthracene-9,10-endo-
1
/c space group with one
,b-succinyl amine
In the solid state, the UV–visible spectrum of compound 1
exhibits one strong peak at 404 nm ascribed to * transition
28]. Compound 2 exhibits a strong absorption peak at 280 nm in
its UV spectrum. The obvious hypsochromic shift of absorption
peak in the UV spectrum of compound 2 is attributed to the
destruction of the conjugated structure of anthracene. Electron
cannot be delocalized over the whole molecule and more energy
a
p
? p
molecule in the asymmetric unit. As shown in Fig. 2, C(20) and
[
0
C(20 ) are disordered over two locations and each site of them is
half-occupied. Two phenyl rings 1, 2 and one five-membered ring
3
are composed of C atoms from C7 to C12, C14 to C19, and C1,
C2, C3, C4, N1, respectively. The dihedral angles between rings 1
and 2, 1 and 3, 2 and 3 are 119.6°, 178.0° and 62.3°, respectively.
The H(3)–C(3)–C(2) and H(4)–C(4)–C(1) bond angles are 110.2°
and 109.5°, respectively, indicating compound 3 has the endo-con-
formation and it exhibits the cis-configuration.
is needed for the
p ? p* transition.
3.5. Photoluminescence property
1
As mentioned above, compound 3 crystallizes in nonchiral P2 /c
In the solid state, compound 1 exhibits very intense emission in
the 413–816 nm range when excitation at 268 nm at room temper-
ature (see Fig. 3a), which is attributable to the * ? n transition
29]. Whereas compound 2 exhibits weak emission in the same
range when excitation at 268 nm (Fig. 3b). The emission intensity
of compound 2 is much lower than that of compound 1, indicating
fluorescence quench happens to some extents due to the destruc-
tion of the conjugated structure of anthracene and undelocalized
electron in compound 2.
space group. As we know, the Diels–Alder reaction has been used
extensively in the synthesis of natural products because it is regio-
selective and a number of chiral centers can be formed in the reac-
tion. Both Diels–Alder reaction and the synthesis of acyl amine
from acid anhydride do not change the position of methyl groups
of the starting material. So if compound 1 is 2,7-dimethylanthra-
cene, as shown in Scheme 3a, compound 3 would be cis-2,7-di-
p
[
methyl-9,10-dihydroanthracene-9,10-endo-
which is a chiral compound, and compound 3 would crystallize
in a chiral space group, it is inconsistence with the P2 /c space
a,b-succinyl
amine,
1
group. If compound 1 is 2,6-dimethylanthracene, as shown in
Scheme 3b, compound 3 would be cis-2,6-dimethyl-9,10-dihydro-
anthracene-9,10-endo-a,b-succinyl amine, which is a nonchiral
compound, and compound 3 would crystallized in a nonchiral
space group, it is consistence with our experimental result. The
data proves that the positions of the methyl groups in compounds
1–3 are 2,6-positions. It is indicated that the synthesis of com-
pound 1 is accurate and the mechanism for the formation of com-
pound 1 is possible.
3.3. IR spectra
As shown in Scheme 1, compound 1 is a planar aromatic struc-
ture and compound 2 is a 3D structure. The IR spectra of com-
pounds 1 and 2 are different. Compound 1 shows characteristic
ꢁ1
bands of anthracene in the 894–1633 cm range. Compound 2
shows characteristic bands of carboxyl groups at 1863 and
Fig. 3. Solid-state emission spectra of compounds
temperature.
1 (a) and 2 (b) at room
ꢁ1
1
778 cm . Due to the destruction of the conjugated structure of

Y. Gong et al. / Journal of Molecular Structure 963 (2010) 76–81
81
4
. Conclusion
Appendix A. Supplementary data
In summary, in the present paper, utilizing the easily accessible
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2009.10.017.
benzyl alcohol as the starting material, we report a simple one-step
synthesis of 2,6-dimethylanthracene, 1, in high yield. Based on 2,6-
dimethylanthracene, two pseudo-triptycene compounds, cis-2,6-di-
References
methyl-9,10-dihydroanthracene-9,10-endo-
a
,b-succinic anhydride,
[
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(
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a,b-suc-
cinyl amine, 3, are firstly synthesized in high yield and they are char-
acterized by single crystal X-ray diffraction. Both compound 2 and 3
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3
[
1
exhibits very intense photoluminescence property due to the delo-
1
calized electron in the whole molecule, whereas fluorescence quench
happens to some extents due to the destruction of the conjugated
structure in compound 2. Compound 1 may be an excellent candidate
for potential photoactive material, whereas compound 2 may be a
good ligand for the construction of porous metal–organic framework
due to its unique 3D structure.
4
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. Supporting materials
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[
[
1
parameters are available from the authors on request. Copies of
X-ray crystallographic files in CIF format for the structure determi-
nation may be obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 IEZ, UK (fax: +44 1223 336033;
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This work was supported by Natural Science Young Scholars
Foundation of Chongqing University, Large-scale Instrument and
Equipment Open Foundation of Chongqing University, Scientific
Research Start-up Foundation of Chongqing University, Chongqing
University Postgraduate Science (No. 200911A1B0010317), Inno-
vative Talent Training Project, the Third Stage of ‘‘211 project” of
Chongqing University (No. S-09103).
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