The synthesis, spectroscopic characterization and structure of three bis(arylmethylidene)cyclopentanones

Article abstract of DOI:10.1016/j.dyepig.2009.12.010

Three bis(arylmethylidene)cyclopentanone dyes were synthesized and their structures and properties elucidated using single-crystal X-ray diffraction, mass spectrometry, ¹H nuclear magnetic resonance, IR and UV-Vis spectroscopy. X-ray analyses r

Full text of DOI:10.1016/j.dyepig.2009.12.010

Dyes and Pigments 86 (2010) 97e105
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
The synthesis, spectroscopic characterization and structure of three
bis(arylmethylidene)cyclopentanones
,
b
,
b
a
a
a
a
b
Yi-Feng Sun a , Zhu-Yuan Wang , Xue Zhao , Ze-Bao Zheng , Ji-Kun Li , Ren-Tao Wu , Yi-Ping Cui
*
a Department of Chemistry, Taishan University, Taian 271021, China
b Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three bis(arylmethylidene)cyclopentanone dyes were synthesized and their structures and properties
elucidated using single-crystal X-ray diffraction, mass spectrometry, 1H nuclear magnetic resonance, IR
and UVeVis spectroscopy. X-ray analyses revealed that two were monoclinic, with space group P21/c,
while the third dye was triclinic, with space group P1. All three molecules adopted an E-configuration
about the central olefinic bonds, exhibiting a butterfly-shaped geometry. Molecular structure optimi-
zation using density function theory revealed that the optimized geometer parameters were in
reasonably good agreement with experimental values. In addition, the highest occupied molecular
orbital and lowest unoccupied molecular orbital levels were deduced.
Received 2 November 2009
Received in revised form
7 December 2009
Accepted 10 December 2009
Available online 4 January 2010
Keywords:
Bis(arylmethylidene)cycloalkanone
Spectroscopy
Ó 2009 Elsevier Ltd. All rights reserved.
Crystal structure
Density function theory
Frontier orbital
Quantum chemical calculations
1. Introduction
probe, and exhibit promising two-photon absorption (TPA) prop-
erties [16e19]. For example, bis(benzylidene)cyclopentanone
The bis(arylmethylidene)cycloalkanone moiety is both a novel
pharmacophore and an important chromophore. Molecules that
comprise such a structural unit are of special interest owing to their
broad spectrum of activities and applications. Curcumin (Fig. 1) is
a naturally occurring yellow pigment isolated from the root of Cur-
cumalongarhizomes, and exhibits awiderangeofbiologicalactivities
[1e5]. As a class of conjugated monoketone analogues of Curcumin,
the bis(arylmethylidene)cycloalkanones have been already reported
to posses potential anti-HIV protease activity, cytotoxic, cancer che-
mopreventive and antioxidant properties [6e14]. Furthermore, these
compounds are more compact than Curcumin and are readily
synthesized. Recent, it has been reported that some compounds
containing the 3-(3,4,5-trimethoxyphenyl)-2-propenoyl group dis-
played potent multidrug resistance (MDR) reversal properties in
cancer chemotherapy. In particular, 2,5-bis(3,4,5-trimethoxyphen-
ylmethylene) cyclopentanone (TMPCP) (Fig. 1) was 31 times more
potent than Verapamil as a MDR revertant [15].
derivatives MPCP and EPCP (Fig. 1) are well-known high-efficient
sensitizing dye that is widely employed in photopolymerization
systems. Also, in a very recent study it was shown that these two bis
(benzylidene)cyclopentanone dyes displayed large two-photon
absorption cross-sections [20,21]. Besides, bis(arylmethylidene)
cycloalkanones are widely used as building blocks for the synthesis
of a new class of spiro pyrrolidines as antimicrobial and antifungal
agents, tricyclic thiazolo[3,2-a] thiapyrano[4,3-d] pyrimidines and
related analogues as potential anti-inflammatory agents and other
bioactive heterocycles [6,22,23].
As a part of our continuous interest in the synthesis, crystallog-
raphy and optical evaluation of bis(arylmethylidene)cycloalkanone
derivatives, three bis(arylmethylidene) cyclopentanone dyes, 1, 2
and 3 (Fig. 2), were synthesized. Herein, we report the synthesis,
crystal structure and spectroscopic characterization of these three
dyes. At the same time, the molecular structures of 1 and 3 were
optimized using density function theory (DFT) at B3LYP/6-31G level.
On the other hand, some bis(arylmethylidene)cycloalkanones
are found be effective photosensitive materials and fluorescent
2. Experimental
2.1. Chemicals and instrument
* Corresponding author at: Department of Chemistry, Taishan University, Taian
271021, China. Tel.: þ86 538 6715546; fax: þ86 538 6715536.
E-mail address: sunyf50@yahoo.com.cn (Y.-F. Sun).
All melting points were determined with a WRS-1A melting
point apparatus and are uncorrected. Proton nuclear magnetic
0143-7208/$ e see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2009.12.010

98
Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
Fig. 1. The structures of Curcumin, TMPCP, MPCP and EPCP.
resonance (1H NMR) spectra were run on a Bruker AV-400 or DRX-
500 NMR spectrometer and chemical shifts expressed as (ppm)
(15 mL) of sodium hydroxide (75 mmol) was added dropwise with
stirring at room temperature. The reaction mixture was stirred for
a further 3 h and then poured into a mixture of ice and concen-
trated hydrochloric acid. The precipitate was filtered by suction and
washed thoroughly with water and finally with ethanol. The
product was dried at room temperature and crystallized from
ethanol to give 1 as yellow crystals, yield 67%, mp 155e157 ꢁC; 1H
d
values with TMS as internal standard. IR spectra were recorded
in KBr on a Nicolet NEXUS 870 FT-IR spectrophotometer. Vibra-
tional transition frequencies are reported in wave numbers (cmꢀ1).
The UV spectra were recorded using a Helios Alpha UVeVis
scanning spectrophotometer. Element analysis was taken with
a PerkineElmer 240 analyzer. Mass spectra (MS) were measured on
a LCQ Advantage MAX or VG ZAB-HS mass spectrometer. Single
crystal was characterized by Enraf-Nonius CAD-4 or Bruker Smart
1000 CCD X-ray single-crystal diffractometer. All the chemicals
are commercially available and they were used without further
purification.
NMR (400 MHz, CDCl3/TMS)
6H, Ar-H), 7.17 (t, J ¼ 7.3 Hz, 2H, Ar-H), 7.24 (t, J ¼ 1.8 Hz, 2H, Ar-H),
: 1685,
d: 3.04 (s, 4H, 2 ꢂ CH2), 7.03e7.08 (m,
7.32e7.44 (m, 8H, Ar-H), 7.55 (s, 2H, 2 ꢂ ]CHe). IR (KBr)
n
1629, 1593, 1568, 1496, 1455, 1434, 1230, 1199, 1158, 1071, 948, 892,
753, 671 cmꢀ1. MS m/z: 445 (M þ 1). Anal. calcd for C31H24O3: C
83.76, H 5.44; found: C 83.52, H 5.75.
2.2.2. 2,5-Bis-(3,5-di-tert-butyl-4-hydroxybenzylidene)
2.2. Synthesis
cyclopentanone (2)
The title compound was prepared by the acid catalyzed reaction
of 3,5-di-tert-butyl-4-hydroxybenzaldehyde with cyclopentanone,
as previously described in [24,25] with modification. 20 mmol of
3,5-di-tert-butyl-4-hydroxybenzaldehyde and 10 mmol of cyclo-
pentanone were dissolved in 30 mL of methanol. To this solution,
1.5 mL concentrated sulfuric acid was added dropwise with stirring
at room temperature, which continued for 0.5 h. Then, the reaction
mixture was refluxed for 3 h. After cooling, the mixture was treated
with cold water and filtered. The solid obtained was then washed
and dried. The crude product was recrystallized from ethanol to
give 2 as yellow crystals, yield 49%; 1H NMR (400 MHz, DMSO-d6/
2.2.1. 2,5-Bis-(3-phenoxybenzylidene)cyclopentanone (1)
For the preparation of the title compound, 5 mmol of cyclo-
pentanone and 10 mmol of 3-phenoxybenzaldehyde were dis-
solved in 20 mL of ethanol. To this solution, an aqueous solution
TMS)
d
: 1.42 (s, 36H, 12 ꢂ CH3), 3.05 (s, 4H, 2 ꢂ CH2), 7.37 (s, 2H,
OH), 7.44 (s, 4H, Ar-H), 7.52 (s, 2H, 2 ꢂ ]CHe). IR (KBr)
n: 3611,
3406, 1665, 1619, 1588, 1424, 1322, 1255, 1184, 1127, 1009, 943, 876,
774, 605, 492 cmꢀ1. MS m/z: 517 (M þ 1). Anal. calcd for C35H48O3: C
81.35, H 9.36; found: C 81.12, H 9.23.
2.2.3. 2,5-Bis-(9-anthrylmethylidene)cyclopentanone (3)
This compound was prepared according to the procedure
described for 1, from 20 mmol 9-anthrylaldehyde and 10 mmol
cyclopentanone. Red crystals, yield 56%, mp > 235 ꢁC; 1H NMR
(500 MHz, CDCl3/TMS)
d
: 2.30 (s, 4H, 2 ꢂ CH2), 7.48e7.54 (m, 8H, Ar-
H), 8.01e8.12 (m, 8H, Ar-H), 8.47 (s, 2H, Ar-H), 8.59 (s, 2H, 2 ꢂ ]CHe).
IR (KBr) n: 1676, 1634, 1627, 1441, 1408, 1359, 1310, 1207, 1157, 1089,
956, 890, 847, 796, 735, 728, 535, 512 cmꢀ1. MS m/z: 461.00 (M þ 1).
Anal. calcd for C35H24O: C 91.27, H 5.25; found: C 91.53, H 5.18.
2.3. X-ray crystallography
Suitable single crystals of 1, 2 and 3 for X-ray structural
Fig. 2. The structures of bis(arylmethylidene)cyclopentanones.
analysis were obtained by evaporation of ethanol or DMF

Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
99
Table 1
distances 0.093e0.097 nm and Uiso(H) ¼ 1.2Ueq(C). A summary of
the crystallographic data and structure refinement details is given in
Table 1.
Crystal data and structure refinement.
Compound
1
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
a (nm)
C31H24O3
444.50
293 (2)
Monoclinic
P21/c
C35H48O3$C2H6O C35H24O$C3H7NO
562.80
533.64
273 (2)
Triclinic
P1
3. Results and discussion
273 (2)
Monoclinic
P21/c
3.1. Synthesis
Derivatives of bis(arylmethylidene) cyclopentanone are usually
obtained by the ClaiseneSchmidt condensation. The properly
substituted arylaldehydes were reacted with cyclopentanone in the
presence of sodium hydroxide, to afford bis(benzylidene) cyclo-
pentanone derivatives 1 and 3 in 56e67% yields. On the other hand,
although compound 2 has been studied previously by other groups
[24,25], the crystal structure of 2 has not been reported. So, with
a modified method, we prepared the 2 by reaction of 3,5-di-tert-
butyl-4-hydroxybenzaldehyde with cyclopentanone in the pres-
ence of concentrated sulfuric acid in methanol under reflux.
Compared with the method reported in literature [24,25], such
a modified procedure for preparation of compound 2 affords the
advantage of short reaction time.
Concerning stereochemistry, the olefinic bis(arylmethylidene)
cyclopentanones were obtained in E-configuration for sterical
reasons since in the Z-isomers the aryl rings have to turn out of the
plane of the olefinic double bond because of interaction of the ortho
H atoms with the carbonyl O-atom. Also, the E-configuration of the
olefinic bond of 1, 2 and 3 was established by X-ray diffraction
crystal structure analysis in this work.
0.61260 (12)
4.3862 (9)
0.85740 (17)
90
97.20 (3)
90
2.2857 (8), 4
1.292
0.082
1.0812 (17)
1.878 (3)
1.895 (3)
90
99.55 (3)
90
1.05631 (15)
1.10456 (15)
1.36961 (19)
98.092 (2)
90.018 (3)
115.825 (3)
1.4207 (3), 2
1.247
b (nm)
c (nm)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
Volume (nm3), Z
Dcalc (Mg/m3)
Absorption
3.794 (10), 4
0.985
0.062
0.076
coefficient (mmꢀ1
F (0 0 0)
)
936
1232
564
Crystal size (mm)
0.30 ꢂ 0.20 ꢂ 0.10 0.21 ꢂ 0.16 ꢂ 0.12 0.20 ꢂ 0.15 ꢂ 0.11
q
range for data
collection (ꢁ)
1.86e25.33
1.54e25.05
1.51e25.05
Limiting indices
ꢀ7 ꢃ h ꢃ 7
0 ꢃ k ꢃ 52
0 ꢃ l ꢃ 10
ꢀ12 ꢃ h ꢃ 11
ꢀ17 ꢃ k ꢃ 22
ꢀ20 ꢃ l ꢃ 22
16162/6478
[Rint ¼ 0.0723]
0.9926
ꢀ12 ꢃ h ꢃ 12
ꢀ12 ꢃ k ꢃ 13
ꢀ16 ꢃ l ꢃ 16
7592/5009
[Rint ¼ 0.0270]
0.9917
Reflections
4503/4132
[Rint ¼ 0.0509]
0.9918
collected/unique
Max. and min.
transmission
Data/restraints/
parameters
and 0.9758
4132/147/307
and 0.9871
6478/1/374
and 0.9849
5009/0/371
Goodness-of-fit on F2 1.002
Final R indices
[I > 2 sigma (I)]
R indices (all data)
1.009
1.010
R1 ¼ 0.0878
R1 ¼ 0.0643
wR2 ¼ 0.1463
R1 ¼ 0.1614
wR2 ¼ 0.1917
0.0035 (7)
214 and 175
R1 ¼ 0.0576
wR2 ¼ 0.1411
R1 ¼ 0.1092
wR2 ¼ 0.1734
0.0059 (19)
240 and 203
All the synthesized compounds have been characterized on the
basis of their physical data and spectral analysis. The IR spectra of
these compounds showed two strong bands at 1665e1685 and
1619e1634 cmꢀ1 due to C]O and C]C double bond, respectively,
indicating the formation of arylmethylidenecyclopentanone back-
wR2 ¼ 0.1532
R1 ¼ 0.1864
wR2 ¼ 0.1897
Extinction coefficient
Largest diff. peak
240 and 207
750903
and hole (e.nmꢀ3
)
bone. In the IR spectra of 2, the n(OeH) vibrations occur as very
CCDC
750906
750902
strong absorption at 3611 and 3406 cmꢀ1. All the compounds show
the NMR signals for different kinds of protons at their respective
positions. The values are consistent with their predicted structures.
The complete chemical shifts for all compounds are listed in
Experimental part.
solution. The diffraction data for three structures were collected
with a Enraf-Nonius CAD-4 diffractometer or Bruker Smart Apex
1000 CCD area detector using a graphite monochromated Mo K
a
radiation (
l
¼ 0.071073 nm) at 293 (2) K or 273 (2) K. The
3.2. Crystal structure
structures were solved by direct methods with SHELXS-97
program and refinements on F2 were performed with SHELXL-97
program by full-matrix least-squares techniques with anisotropic
thermal parameters for the non-hydrogen atoms. All H atoms
were initially located in a difference Fourier map. The methyl H
atoms were then constrained to an ideal geometry, with
CeH ¼ 0.096 nm and Uiso(H) ¼ 1.5Ueq(C). The hydroxyl H atom was
treated as a riding atom, with OeH ¼ 0.082 nm and Uiso(H) ¼
1.5Ueq(O). All other H atoms were placed in geometrically idealized
positions and constrained to ride on their parent atoms with CeH
X-ray diffraction crystal structure analysis reveals that the three
molecules, 1, 2 and 3, are remarkably similar. All three are adopt an
E-configuration about the central olefinic bonds, exhibiting
a butterfly-shaped geometry, which is similar to that of TMPCP
[26], as shown in Fig. 3e10. Both compound 1 and 2 crystallized
monoclinically with space group P21/c, while compound 3 crys-
tallized in the triclinic P1 space group.
In compound 1 (Fig. 3), the central cyclopentanone ring is
essentially planar. And the cyclopentanone ring, the olefinic bonds
Fig. 3. The molecular structure of 1, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small spheres of
arbitrary radius.

100
Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
Fig. 4. The side elevation of 1. H atoms are omitted for clarity.
Fig. 5. A packing diagram for 1, viewed down the c axis. The dashed lines indicate hydrogen bonds.
Fig. 6. The molecular structure of 2, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small spheres of
arbitrary radius. Ethanol molecule is omitted for clarity.
Fig. 7. The side elevation of 2. Ethanol molecule and H atoms are omitted for clarity.

Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
101
Fig. 10. The side elevation of 3. DMF molecule and H atoms are omitted for clarity.
and the two phenyl rings (C7eC12 and C20eC25) are almost
coplanar [r.m.s. deviation ¼ 0.01373 nm, maximum devia-
tion ¼ 0.0099 nm for atom C18], which allows conjugation.
However, the two terminal phenyl rings (C1eC6 and C26eC31)
make a dihedral angle of 65.5ꢁ, and are twisted out of the plane of
the central cyclopentanone unit on the two sides. The dihedral
angles between the cyclopentanone ring plane and the C1eC6 and
C26eC31 phenyl ring planes are 68.5 and 62.6ꢁ, respectively.
Therefore, apart from the two phenyl rings (C1eC6 and C26eC31),
the rest of the molecule is nearly coplanar (Fig. 4).
The molecules are linked together by weak intermolecular
CeH.O (C15eH15B.O2: CeH ¼ 0.097 nm, H15B.O2 ¼ 0.25 nm,
C15.O2 ¼ 0.3339 (5) nm, C15eH15B.O2 ¼147ꢁ) hydrogen bonds
into a one-dimensional chain along the a-axis. The molecules are
assembled to form a layer structure (Fig. 5).
The molecule structure of 2 is shown in Fig. 6. Like molecule 1,
in 2 also, the central cyclopentanone ring is planar. The dihedral
angles between the cyclopentanone ring plane and the C1eC6
and C22eC27 phenyl ring planes are 13.1 and 11.3ꢁ, respectively.
Therefore, apart from the terminal methyl groups, the rest of the
molecule exhibits a bent planar configuration, as observed in
Fig. 7.
In addition, of the twelve methyl groups C10, C14, C29 and C35
are coplanar with one of the benzene rings, with the others
showing out-of-plane twists ranging from w59.3 to 64.5ꢁ.
The molecules are linked into a zigzag one-dimensional chain
along the b-axis by intermolecular OeH.O (O3eH3.O4:
OeH ¼ 0.082 nm, H3.O4 ¼ 0.24 nm, O3.O4 ¼ 0.2974 (5) nm,
O3eH3.O4 ¼131ꢁ; O4eH4.O2i: OeH ¼ 0.082 nm, H4.O2 ¼
0.21 nm, O4.O2 ¼ 0.2968 (5) nm, O4eH4.O2 ¼ 178ꢁ, symmetry
Fig. 8. The chain structure formed via hydrogen bonds in 2. The dashed lines indicate
hydrogen bonds.
Fig. 9. The molecular structure of 3, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small spheres of
arbitrary radius. DMF molecule is omitted for clarity.

102
Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
code: (i) ꢀx þ 2, y ꢀ 1/2, ꢀz þ 1/2) hydrogen bonds (Fig. 8). The
ethanol molecule plays a significant role in the crystal packing as it
is the acceptor in one hydrogen bond and a donor in another.
The compound 3 formed crystalline clathrates with DMF in a 1:1
molar ratio. As can be seen from Fig. 9, in 3, the central cyclo-
pentanone ring is essentially planar, while the two anthracene
rings (C7eC20 and C22eC35) is rotated significantly out of the
plane of the central cyclopentanone unit (Fig. 10), and make
a dihedral angle of 57.6ꢁ. The dihedral angles between the cyclo-
pentanone ring plane and the C7eC20 and C22eC35 anthracene
ring planes are 67.3 and 61.8ꢁ, respectively. As a result, the whole
compound is not a planar molecule. Similar geometry has been
observed in related anthracene analogues, which were reported
previously [27]. But these structural characteristics of compound 3
are remarkably different from those of in 1 and 2. Comparison with
1 and 2 suggests that the anthracene system caused a significantly
rotation relative to the substituted phenyl system, owing to the
larger steric effect of the anthracene ring. In addition, the crystal
packing of 3 is stabilized by weak intermolecular hydrogen bonds
Fig. 11. Absorption spectra of the bis(arylmethylidene)cyclopentanones in chloroform
solution. The inset shows an expansion of the 430 nm absorption peak of 3.
and pep stacking interactions.
Fig. 12. Optimized structures of (a) 1 and (b) 3 by DFT method.

Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
103
3.3. Absorption spectra
frontier molecular orbital were obtained. The optimal structures of
1 and 3 are depicted in Fig. 12. The HOMO (highest occupied
molecular orbital) and LUMO (lowest unoccupied molecular
orbital) levels of 1 and 3 are shown in Figs. 13 and 14.
It was found that the B3LYP/6-31G optimized structures of 1 and
3 (Fig. 12) are in good agreement with the X-ray crystallographic
data. Therefore, the results using DTF at B3LYP/6-31G level is
creditable.
Generally, the energy values of LUMO and HOMO and their
energy gap reflect the chemical activity of the molecule. HOMO as
an electron donor represents the ability to donate an electron,
while LUMO as an electron acceptor represents the ability to obtain
an electron. The smaller the LUMO and HOMO energy gaps, the
easier it is for the HOMO electrons to be excited [28].
The structures of the target molecules are shown in Fig. 2. These
molecules consist of a typical De
substituted phenyl or anthryl, vinyl and carbonyl groups are
employed as donor (D), -conjugated center ( ) and acceptor (A)
moieties, respectively. Moreover, such a structural modification
could be expected to result in notable changes in the
length and red shifts in the absorption spectra.
UVevis absorption spectra of these molecules in diluted chlo-
roform solutions (2 ꢂ 10ꢀ5 M) are given in Fig.11. It can be seen from
Fig. 11 that, the compounds comprise two bands in the wavelength
range from 250 to 550 nm, while almost no linear absorption was
observed beyond 550 nm. The bands at shorter wavelength
peAepeD structure, where the
p
p
p-conjugated
(250e280 nm) are due to localized
p
e
p
* transition of the phenyl
Figs.13 and 14 show the frontier orbitals of the molecules. Based
on the calculations, the electron cloud of HOMO for compound 1 is
mainly focused on four benzene rings, which is composed of
pep
and anthryl moieties, while the longer wavelength bands with lmax
ranging from 362 to 430 nm can be assigned to the intramolecular
charge-transfer transitions involving the whole electronic system of
the compounds with a considerable charge-transfer character
originating mainly from the substituted phenyl or anthryl moiety
and pointing towards the carbonyl group. And, the maximum
absorption peaks of the first absorption band of the target molecules
orbits from CeC. Compared with HOMO, the electron cloud on the
central cyclopentanone of LUMO increases clearly, especially on
carbonyl group (Fig. 13). The above suggests that electrons transfer
from benzene ring to carbonyl group to some extent. Similarly, for
compound 3, the electron cloud of HOMO is focused on two
anchracene rings. Also, the electron cloud on the central cyclo-
pentanone of LUMO increases clearly (Fig. 14). Therefore, when
electrons transfer from HOMO to LUMO, the electron cloud density
on cyclopentanone increases, indicating that electrons transfer
from benzene or anchracene rings to cyclopentanone.
are red-shifted from 1 (lmax ¼ 362 nm,
3
¼ 3.87 ꢂ 104 L molꢀ1 cmꢀ1
)
3
to
2
(
lmax ¼ 402 nm,
3
¼ 4.52 ꢂ 104 L molꢀ1 cmꢀ1), and to
(lmax ¼ 430 nm,
3
¼ 7.18 ꢂ 103 L molꢀ1 cmꢀ1). Obviously, the
anthracene system caused a bathochromic effect of approximately
28e68 nm relative to the substituted phenyl system. The results
above imply that more
p
-electrons and longer
p
-conjugated
The energies of the HOMO and LUMO for compound 1 based on
the optimized structure were computed at ꢀ5.91 and ꢀ2.27 eV,
respectively. Similarly, the energies of the HOMO and LUMO of
compound 3 are ꢀ5.22 and ꢀ2.29 eV, respectively. Obviously, the
LUMO energy of 3 is slight lower than that of compound 1, and the
energy gap of 3 is smaller than that of 1. But the HOMO energy of
compound 3 is higher than that of compound 1. Consequently, the
electrons transfer from HOMO to LUMO in 3 is relatively easier than
that in 1. Furthermore, we noticed that the presence of anthracene
makes the HOMO rather high in energy and decrease the energy
gap between HOMO and LUMO. So, compared to 1, a bathochromic
shift of 3 can be observed in the electron absorption spectrum.
These results are quite consistent with those from the experiment
structure may be involved in 3 than those in other. As a result, the
red shift of absorption can possibly occur. Additionally, it could be
recognized that the absorption band of 2 exhibited a red-shift of
40 nm compared to that of 1. This difference might be attributed to
the stronger electron-donating effect of hydroxy group.
3.4. Quantum chemical calculations
The geometry structures of 1 and 3 were optimized with density
function theory (DFT) at the B3LYP/6-31G level, all structure opti-
mizations and energy calculations were performed with the
GAUSSIAN 98 program. Their structure parameters and energy of
Fig. 13. Molecular orbital surface and energies of the main frontier molecular orbitals for 1.

104
Y.-F. Sun et al. / Dyes and Pigments 86 (2010) 97e105
Fig. 14. Molecular orbital surface and energies of the main frontier molecular orbitals for 3.
in this work. In addition, we also found a pair of doublet split in
energy, HOMO-1 and HOMO-2.
In all, the different substituents on cyclopentanone derivatives
can affect the energy and gap of frontier molecular orbital greatly,
which provide reference for the molecular design and energy gap
adjustment.
Center as supplementary publication no. CCDC 750903, 750906 and
750902. Copy of this information may be obtained free of charge via
www: http://www.ccdc.cam.ac.uk or from The Director, CCDC, 12
Union Road, Cambridge CB221EZ, UK (fax: þ44 1223/336 033;
email: deposite@ccdc.cam.ac.uk). Structural factors are available on
request from the authors.
4. Conclusions
Acknowledgements
The synthesis, characterization and crystal structures deter-
mined by single-crystal X-ray diffraction, of three bis(arylmethyli-
dene) cyclopentanone dyes, 1, 2 and 3, are reported. The absorption
spectra of these three molecules were discussed. With the
anchracene moiety, the edge of absorption spectra of 3 was shift to
long wavelength side. The molecular structures of 1 and 3 were
optimized using density function theory (DFT) at B3LYP/6-31G level
while the HOMO and LUMO levels of 1 and 3 were deduced.
This project was supported by the National Natural Science
Foundation of China (No. 60877024) and the Foundation of Taishan
University (No. Y04-2-02).
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