Synthesis and luminescent properties of Zn complex based on 8-hydroxyquinoline group containing 3,5-bis(trifluoromethyl) benzene unit with unique crystal structure

Article abstract of DOI:10.1016/j.tet.2010.09.039

The use of a novel 2-substituted-8-hydroxyquinoline ligand (E)-2-{2-[3,5-bis (trifluoromethyl)phenyl]ethenyl}-8-hydroxyquinoline(4, BFHQ) characterized by EIMS, ¹H NMR spectroscopy, elemental analysis, and FTIR spectroscopy enabled the isolatio

Full text of DOI:10.1016/j.tet.2010.09.039

Tetrahedron 66 (2010) 8635e8640
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and luminescent properties of Zn complex based on
8-hydroxyquinoline group containing 3,5-bis(trifluoromethyl)
benzene unit with unique crystal structure
,
,
a
Yan-Ping Huo a b, Shi-Zheng Zhu b , Sheng Hu
*
a Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China
b Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2010
Received in revised form 8 September 2010
Accepted 10 September 2010
Available online 17 September 2010
The use of a novel 2-substituted-8-hydroxyquinoline ligand (E)-2-{2-[3,5-bis(trifluoromethyl)phenyl]
ethenyl}-8-hydroxyquinoline(4, BFHQ) characterized by EIMS, 1H NMR spectroscopy, elemental analysis,
and FTIR spectroscopy enabled the isolation of a trimeric Zn(II) complex with the formula Zn3(BFHQ)6 (5,
Scheme 1). X-ray structural analysis shows that 5 exhibits a trinuclear core, which is bridged by four
8-hydroxyquinoline rings. The trinuclear core is surrounded by three pairs of BFHQ ligands with offset
pep stacking, showing propeller-like molecular structure. The aggregation behavior of Zn(AcO)2 and the
Keywords:
8-Hydroxyquinoline
Metal complex
Crystal structure
Luminescence properties
ligand 4 in solution was investigated by UVevis. The luminescence properties of compound 5 were
investigated by UVevis and fluorescence spectra at room temperature. The experimental results show
that the complex 5 emits yellow luminescence at 553 nm (lem, max) in DMSO solution and at 610 nm
(
lem, max) in solid state. The thermogravimetric analysis was carried out to examine the thermal stability.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
large conjugated groups and tuned their luminescence to yellow-
light (lem¼610 nm). On the other hand, the fluorinated organic
Since Tang and VanSlyke developed multi-layered organic light-
emitting diodes (OLEDs) using tris-(8-hydroxyquinoline)aluminum
(AlQ3) as the emission and electron transport material,1 much effort
has been made to the development of highly efficient OLEDs,2e4
especially the white OLEDs.5e8 To obtain white emission, various
strategies have been developed. For small-molecule OLEDs, the
general approach is to fabricate multiplayer devices by consecutive
evaporation involving three primary colors (blue, green, and red) or
two special colors (blue and yellow). However, multiplayer con-
struction of devices will increase the cost of fabrication processes.
In order to reduce the cost and obtain white OLEDs with minimal
process of fabrication, it would be necessary to discover multi-
function and highly efficient yellow-light emitting materials.
8-Hydroxyquinoline aluminum (AlQ3) has been identified as an
excellent green-light emitting and electronic transporting material.1
In order to retain the excellent photoelectron properties of
8-hydroxyquinoline itself and achieve yellow-light emission, a fea-
sible approach is to modify the 2-, 5- or 7-position of the 8-hydroxy-
quinoline rings with different functional groups.9e14 For example,
Cui10 reported 2-substituted-8-hydroxyquinoline molecules with
semiconductors have been reported to possess a high electron mo-
bility, excellent air-stability, low sublimation temperature, and
perhaps a broadened energy gap, because of the strong electron-
withdrawing properties of the fluorine atom.15,16 It is supposed that
highly efficient yellow-light emitting materials could be realized
from fluorinated MQn derivatives. However, related reports on fluo-
rinated MQn derivatives are rare so far.17,18 In addition, research
suggests that the electron-transporting mobility of zinc complexes
with 8-hydroxyquinoline goes beyond that of aluminum complexes,
which is the most widely used electron-transporting material in
OLEDs. Thus zinc complexes may be potential candidates to enhance
the electron-transporting properties for OLEDs.24,25 Inspired by these
results, we designed and synthesized the novel ligand: (E)-2-{2-[3,5-
bis(trifluoromethyl)phenyl]ethenyl}-8-hydroxyquinoline(4) and the
corresponding Zn complex: Zn3(BFHQ)6.13 It is expected that a com-
bination of 3,5-bis(trifluoromethyl) benzene unit and 8-hydrox-
yquinoline could not only retain the excellent photoelectron
properties of 8-hydroxyquinoline itself but also achieve yellow-light
emission.
We report herein the first synthesis of light-emitting molecule
Zn3(BFHQ)6, which contains the 3,5-bis(trifluoromethyl) benzene
moiety and 8-hydroxyquinoline derivative. The synthetic strategies
for light-emitting molecule 5 is outlined in Scheme 1. We also in-
vestigated its thermal stability, fluorescence property, and crystal
* Corresponding author. Tel.: þ86 21 54925185; fax: þ86 21 64166128; e-mail
address: zhusz@mail.sioc.ac.cn (S.-Z. Zhu).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.09.039

8636
Y.-P. Huo et al. / Tetrahedron 66 (2010) 8635e8640
structure, which indicated that 5 emits yellow luminescence at
553 nm (lem, max) in DMSO solution and at 610 nm (lem, max) in solid
state, and has a highly symmetrical structure belonging to space
group of C2/c.
2.2. Structure description
X-ray structural analysis shows that 5 has a highly symmetrical
structure belonging to space group of C2/c. The asymmetric unit
contains one half of a formula unit, that is, 1.5 unique Zn(II) atoms
(Zn1 lies in a general position and Zn2 lies in a special position) and
three BFHQ ligands. The structure of 5 is built around a trimeric Zn
(II) structure (Fig. 2a). Three pairs of BFHQ ligands with offset face-
CHO
Ac2O
80%
H2O/pyridine
93 %
CF3
CF3
+
N
N
CH3
F3C
CF3
OCOCH3
OH
1
to-face pep stacking are arranged around the trimeric Zn(II) core in
2
3
a propeller-like form to generate a supramolecular chiral molecule,
in which chirality arises from the chelate Zn(II) centers. Although
the trimeric cluster is chiral, two enantiomers are present in the
same crystal (C2/c space group, Fig. 3). The zinc atoms (Zn1 and
Zn1A) found on either end of the trimeric unit is pentacoordinate,
resulting in a distorted trigonal bipyramidal geometry, and the
central zinc atom (Zn2) is hexacoordinate, resulting in a highly
distorted octahedral geometry. Four of the BFHQ ligands are in-
volved in bridging through the phenolato oxygens, while the
remaining two terminal ligands are bound to Zn(1) atoms only. In
detail, the Zn1 atom adopts a trigonal bipyramidal geometry with
the equatorial plane occupied by the N2O donors of three ligands
around the Zn1 and the apical position by two phenol oxygen atoms.
The Zn1eN and Zn1eO bond lengths range from 2.147(4) to 2.228
CF3
CF3
CF3
N
Zn(AcO)2.2H2O
72%
N
OH
O
6
(Zn)3
CF3
5
4
Scheme 1.
2. Results and discussion
2.1. 1H NMR and FTIR spectra
The 1H NMR spectra of 4 and 5 in (CD3)2SO solvent are shown in
Fig. 1. In the 1H NMR spectrum of 4 the proton signals at 9.58,
8.35e8.43, 8.06, 7.87, 7.76, 7.38e7.47, 7.13 can be easily assigned to
each the corresponding hydrogen, respectively, which indicate the
presence of the hydroxyquinoline and vinylene. The proton signal
at 9.58 ppm corresponds to HeO proton of the quinoline. One
doublet at 7.87 with a coupling constant¼15.9 Hz, indicates the
presence of trans configuration in the vinylene units. In the 1H NMR
spectrum of 5 the proton signals at 8.85, 8.49, 8.39, 8.19, 8.10, 8.04,
7.04, 6.93 can also be easily assigned to each the corresponding
hydrogen, respectively. Compared to that of the ligand 4, the proton
signal at 9.58 ppm corresponding to HeO proton of the quinoline is
not observed in the 1H NMR spectrum of 5. Two doublets at 8.85,
8.04 with a coupling constant¼16.5 Hz, indicate the presence of
trans configuration in the vinylene units. Overall, the resonances in
the pyridyl ring of the complex 5 shifted downfield with respect to
that of the free ligand, and the resonances in the phenoxide ring of
the complex 5 shifted upfield with respect to that of the free ligand
(Fig. 1). These results indicate the occurrence of the coordination
between the ligand 4 and Zn(OAc)2.
ꢀ
ꢀ
(4) A and from 1.953(3) to 2.041(3) A, respectively, the cis-bond
angles around the Zn1 atom range from 79.14(13)ꢁ to 124.99(15)ꢁ,
while the trans-bond angle is 125.05(13)ꢁ. The coordination envi-
ronment of the Zn2 ion is a distorted octahedron and the equatorial
Fig. 1. 1H NMR spectra of 4 and 5.
The absorption peak of OeH is observed at 3365 cmꢀ1, the ab-
sorption peak at 1693 cmꢀ1 is assigned to C]C bond stretching
frequency, respectively, in the IR spectrum of the ligand 4. A sharp
peak at 743 cmꢀ1 can be assigned to the out of-plane bending mode
of the transvinylene groups, suggesting that the generated double
bond is mainly in the trans-configuration. The IR spectrum of the
complex 5 has similar absorption bands but a little shift, compared
to that of the ligand 4. The C]C band shifts to 1638 cmꢀ1. The ab-
sorption band at 3365 cmꢀ1 corresponding to OeH stretching fre-
quency is not observed in the IR spectrum of the complex 5. At the
same time, some new sharp bands are observed at 566e505 cmꢀ1
Fig. 2. (a) Perspective views of the coordination geometries of Zn(II) atoms in 5 (some
equivalent atoms have been generated to complete the Zn coordination, H atoms
omitted for clarity). (b) Space-filling and stick-and-ball representation of the propeller
structure of 5.
for 5, which assigned to the n(MeO) stretching vibration, and ob-
served at 496e442 cmꢀ1 for 5, which assigned to the
n(MeN)
stretching vibration.19,20

Y.-P. Huo et al. / Tetrahedron 66 (2010) 8635e8640
8637
Fig. 3. Space-filling representation of the two enantiomers present in 5. For clarity each BFHQ ligand is represented in a different color.
plane occupied by the NO3 donors of three ligands, while the apical
position by one phenol oxygen atom and a pyridine atom. The
3,5-bis(trifluoromethyl) benzene moiety. The absorption bands of
the complex 5 exhibit a red shift comparing to that of ligand 4,
which can be attributed to the increasing conjugated degree of the
complex.
ꢀ
Zn2eN bond lengths are 2.208(4) A and Zn2eO bond lengths range
ꢀ
from 1.992(3) to 2.208(3) A, respectively, the cis-bond angles
around the Zn2 atom range from 75.74(13) to 109.39(14)ꢁ, while the
trans-bond angles range from 154.82(14)ꢁ to 167.79(16)ꢁ.
Complex 5
There are significant hydrogen bonds in 5. Weak nonclassical
CeH/O intramolecular hydrogen bonds between the phenolato
oxygen and the CeH group of quinoline ring or ethenyl
0.8
4(L)
L
Zn(AcO)2:L=1:8
Zn(AcO)2:L=1:6
ꢁ
ꢁ
ꢀ
0.6
(C/O¼2.995e3.232 A; CeH/O¼140.0 e150.0 ) as well as inter-
molecular nonclassical CeH/F hydrogen bonds involving the aro-
matic CeH groups and trifluoromethyls of adjacent 3,5-bis
(trifluoromehyl)benzene units of BFHQ ligands (C/F¼2.704e
Zn(AcO)2:L=1:4
0.4
0.2
0.0
Zn(AcO)2:L=1:2
Zn(AcO)2:L=1:1
Zn(AcO)2:L=2:1
ꢁ
ꢁ
ꢀ
3.325 A; CeH/F¼100 e142 ) play a vital role in the consolidation of
the solid structure (Fig. 4). Moreover, it is notable thateach clusterof 5
involves abundant intramolecular
shown in Fig. 3, almost all aromatic rings of BFHQ possess significant
offset face-to-face stacking interactions with closest interplanar
pep stacking interactions. As
pep
200
300
400
500
ꢀ
and centroidecentroid separations are in 3.07e3.51 and 3.62e3.62 A,
Wavelength/nm
respectively.
Fig. 5. UVevis titrations of L (methanol) with Zn(AcO)2 (H2O).
Fig. 4. (a) The trinuclear zinc molecule of 5 and its CeH/O intramolecular hydrogen bonding (red dashed lines) are included. (b) The supramolecular 3D structure of 5 mediated by
CeH/F hydrogen bonding (red dashed lines).
2.3. UVevis absorption titration
In order to investigate the interaction mode of ligand 4 (L) with
Zn(II) ion in solution, the coordination reaction of L with Zn(II) ion
was monitored through a UVevis spectroscopic titration. After the
addition of Zn(II) ion, the absorption band of 4 at 209 nm exhibits
hypochromism 35% for 5, while the absorption bands of 4 at 226
and 300 nm showed significant bathochromism about 7 and 8 nm
for those of 5 at 233 and 308 nm. From the absorption spectrum of
4 at 345 nm, in the presence of increasing amounts of Zn(II) ion, the
peak was found to become weak and disappear in the end; thus
a new band at 430 nm can be observed in the absorption spectrum
The UVevis absorption spectra of 4 (L) and complex 5 in
methanol solution are shown in Fig. 5. The absorption spectrum of
4 contains four bands at 209, 226, 300, and 345 nm, whereas the
absorption spectrum of 5 contains four bands at 209, 233, 308, and
430 nm. In the absorption spectrum of the ligand 4 the absorption
band at 300 nm originates from intraligand
quinoline moiety. While, the absorption at around 345 nm is at-
tributed to the charge transfer from the quinoline moiety to the
pep transition of
*

8638
Y.-P. Huo et al. / Tetrahedron 66 (2010) 8635e8640
of complex 5. No differences were observed in the absorption
spectra after the 1:2 ratio of Zn(II)/L, as shown in Fig. 5, so this
experiment clearly showed that the coordination reaches the end
point at a 1:2 ratio of Zn(II)/L.
Compared with the ligand 4, the corresponding complex 5 ex-
hibits a red shift in DMSO solution and in the solid state, the reason
has two-folds: the coordination of metal ions enhances the mo-
bility of the electron transition in backbone due to back-coupling
p-bond between the metal and the ligand, and decreases the
electron transition energy of intraligand charge transfer. On the
other hand, the ligand is coordinated with metal ions to form ad-
2.4. Fluorescence emission spectra
ditional five-membered rings, which increases the
tion length and the conformational coplanarity, accordingly
pep conjuga-
*
Luminescent properties of compounds 4 and 5 were in-
vestigated in DMSO solution and in solid state at room tempera-
ture. The fluorescence emission spectra of ligand 4 and the complex
5 are shown in Figs. 6 and 7. The luminescent data of the com-
pounds are summarized in Table 1. The fluorescent spectra of 4 and
5 display maximum emission wavelengths at 473 and 553 nm with
excitation wavelengths at 436 and 467 nm in DMSO solution, and
maximum emission wavelengths at 487 and 610 nm with excita-
tion wavelengths at 342 and 330 nm in the solid state, respectively.
The results indicate that the complex 5 has yellow-light emission in
DMSO solution and in the solid state, respectively. The emission of
the complex 5 in the solid state predominantly originates from
metal-to-ligand charge transfer (MLCT) transition.
reduces the energy gap between the
p
and
*
p molecular orbital of
the ligand.21
2.5. Thermal stability
In the TGA curve of complex 5 (Fig. 8), the thermal degradation
temperature Td (5% weight loss) is 347 ꢁC, furthermore, the char
yield of 5 at 800 ꢁC is 16.5%. From TGA results, the polymeric
complex is found to have formed stable five-membered chelate
rings,22 which may be attributed to the fact that the MeN and MeO
bonds are highly polarized.23
200
100
4
5
5
80
150
60
40
20
0
100
50
0
200
400
600
800
450
500
550
600
650
700
Temperature ( degree )
Wavelength/nm
Fig. 8. TGA curve of 5.
Fig. 6. Emission spectra of the ligand 4 and Zn complex 5 in DMSO.
3. Conclusion
200
5
4
In summary, a propeller-like trinuclear complex Zn3(BFHQ)6
is constructed by self-assembly of Zn(II) ions with a novel
2-substituted-8-hydroxyquinoline ligand. Unlike 8-hydroxyquino-
line ligands with a short and rigid spacer that are generally used for
the constructions of tris-(8-hydroxyquinoline)aluminum analogs,
aromatic stacking interactions and nonclassical CeH/F hydrogen
bonds derived from pendant 3,5-bis(trifluoromethyl)benzene
group of the BFHQ ligand may play a vital role in the formation of
the solid structure and increasing the structural stabilities. More-
over, the aggregation behavior of Zn(AcO)2 and the BFHQ ligand in
solutions was investigated by UVevis. The luminescence properties
of compound (5) were investigated by UVevis and fluorescence
spectra at room temperature. The experimental results show that
the complex 5 emits yellow luminescence at 553 nm (lem, max) in
DMSO solution and at 610 nm (lem, max) in solid state.
150
100
50
0
400
450
500
550
600
650
Wavelength/nm
Fig. 7. Emission spectra of the ligand 4 and Zn complex 5 in solid state.
Table 1
Luminescent properties of the ligand 4 and complex 5
4. Experimental section
Compounds Absorption (nm) Fluorescence spectra (nm)
4.1. Chemicals and instruments
In DMSO (10ꢀ4 M)
In solid
All of the chemicals and reagents were purified before use. The
FTIR spectra were obtained on a Nicolet AV-360 spectrometer (KBr
pellet). NMR spectra were recorded on a Bruker NMR AM-300
spectrometer at room temperature in DMSO-d6 or CDCl3 using TMS
lem, max
209, 226, 300, 345 473
209, 233, 308, 430 553
lex, max
lem, max lex, max
4
5
436
467
487
610
342
330

Y.-P. Huo et al. / Tetrahedron 66 (2010) 8635e8640
8639
as the internal reference. Lower resolution mass spectra were
obtained on an Applied Biosystems Mariner time-of-flight mass
spectrometer using an electrospray ionization technique (ESI). The
elemental analysis is achieved on a PerkinElmer 2400 micro-
analyser. Thermogravimetric analysis (TGA) was conducted under
nitrogen atmosphere at a heating rate 20 K minꢀ1 with a Shimadzu
TGA-7. Ultravioletevisible (UVevis) spectra were measured with
Shimadzu UV-2501 spectrophotometer. The fluorescence spectra
were conducted on a PerkinElmer LS55 luminescence spectrometer
with a xenon lamp as the light source.
trinuclear zinc complex with half of a formula unit in the asym-
metric unit. The CCDC number is 784898 (Tables 2 and 3).
Table 2
Crystal data and structure refinement for 5
5 (293 K)
Empirical formula
C114H60F36N6O6Zn3
2489.79
0.71073
Monoclinic
C2/C
25.641(9)
21.243(7)
19.411(7)
101.460(5)
10,362(6)
4
M
ꢀ
Wavelength (A)
Crystal system
Space group
ꢀ
a/A
ꢀ
4.2. Synthesis
b/A
ꢀ
c/A
ꢁ
b
/
4.2.1. Synthesis of (E)-2-{2-[3,5-bis(trifluoromethyl)phenyl]ethenyl}-
8-acetoxyquinoline (3). To a solution of 8-hydroxyquinaldine (1)
(0.68 g, 4.25 mmol) in acetic anhydride (5 mL) was added 3,5-bis
(trifluoromethyl)benzaldehyde (1.0 g, 4.13 mmol). The mixture was
heated under reflux for 10 h. After cooled, it was subsequently
poured into ice water (50 ml) and stirred overnight. The yellow
solid obtained was filtered and washed with water. The solid resi-
due was recrystallized from CH2Cl2 to afford 3 (1.4 g, 80%): mp
3
ꢀ
V/A
Z
rcalcd/g cmꢀ3
1.596
0.814
m
/mmꢀ1
Reflns collected
Unique reflns
Rint
21,315
9120
0.0773
S
0.809
0.0546
0.1314
a
R1 (I>2
wR2 (all data)
s
(I))
b
159e161 ꢁC; 1H NMR (CDCl3, 300 MHz)
d
8.20 (d, J¼8.4 Hz,1H), 8.02
P
P
a
(s, 2H), 7.82 (s, 1H), 7.72 (d, J¼16.2 Hz, 1H), 7.72 (dd, J¼9.6 Hz,
R1¼ kFojꢀjFck/ jFoj.
P
P
b
J¼1.2 Hz, 1H), 7.67 (d, J¼8.7 Hz, 1H), 7.53 (d, J¼16.2 Hz, 1H),
wR2¼[ w(Fo2ꢀFc2)2/ w(F2o)2]1/2
.
7.44e7.52 (m, 2H), 2.59(s, 3H); 19F NMR (CDCl3, 282 MHz)
d
ꢀ63.76
(6F, s); IR (KBr, cmꢀ1): 3056, 1717, 1593, 1502, 1433, 1285, 1126, 977,
868, 756, 700; ESI-MS m/z: 426.5([MþH]þ); elemental analysis:
found C: 59.24, H: 3.20, N: 3.10 calculated for (C21H13F6NO2) C:
59.30, H: 3.08, N: 3.29 (%).
Table 3
Selected bond lengths (A) and angles ( ) for 5
a
ꢁ
ꢀ
Zn(1)eO(2)
Zn(1)eO(3)
Zn(1)eO(1)
Zn(1)eN(3)
Zn(1)eN(2)
Zn(2)eO(1)
1.953(4)
2.016(3)
2.041(3)
2.147(4)
2.228(4)
1.992(3)
Zn(2)eO(1a)
Zn(2)eN(1)
Zn(2)eN(1a)
Zn(2)eO(3)
Zn(2)eO(3a)
1.992(3)
2.208(4)
2.208(4)
2.208(3)
2.208(3)
4.2.2. Synthesisof (E)-2-{2-[3,5-bis(trifluoromethyl) phenyl] ethenyl}-
8-hydroxyquinoline (BFHQ) (4). A solution of acetoxyquinoline 3
(0.85 g, 2.0 mmol) in pyridine (10 mL) was heated under reflux,
water (5 mL) was then added, and the reaction mixture refluxed for
3 h. After the mixture cooled, water (20 mL) was added to the
mixture. The yellow solid obtained was filtered and washed with
water and dried in vacuo to give compound of 4 (0.71 g, 93%): mp
O(2)eZn(1)eO(3)
O(2)eZn(1)eO(1)
O(3)eZn(1)eO(1)
O(2)eZn(1)eN(3)
O(3)eZn(1)eN(3)
O(1)eZn(1)eN(3)
O(2)eZn(1)eN(2)
O(3)eZn(1)eN(2)
O(1)eZn(1)eN(2)
N(3)eZn(1)eN(2)
O(1)eZn(2)eO(1a)
O(1)eZn(2)eN(1)
O(1a)eZn(2)eN(1)
179.15(16)
101.06(15)
79.14(13)
99.94(16)
80.60(15)
122.71(14)
80.37(18)
98.79(17)
110.80(14)
124.99(15)
167.68(19)
79.35(14)
109.39(14)
O(1)eZn(2)eN(1a)
109.39(14)
O(1a)eZn(2)eN(1a)
N(1)eZn(2)eN(1a)
O(1)eZn(2)eO(3)
O(1a)eZn(2)eO(3)
N(1)eZn(2)eO(3)
N(1a)eZn(2)eO(3)
O(1)eZn(2)eO(3a)
O(1a)eZn(2)eO(3a)
N(1)eZn(2)eO(3a)
N(1a)eZn(2)eO(3a)
O(3)eZn(2)eO(3a)
79.35(14)
93.39(19)
75.74(13)
95.79(13)
154.82(14)
91.45(12)
95.79(13)
75.74(13)
91.45(12)
154.82(14)
94.61(17)
186e188 ꢁC; 1H NMR (d6-DMSO, 300 MHz)
d
7.13 (dd, J¼7.0 Hz,
J¼1.7 Hz, 1H), 7.38e7.47 (m, 2H), 7.76 (d, J¼8.1 Hz, 1H), 7.87 (d,
J¼15.9 Hz, 1H), 8.06 (s, 1H), 8.35e8.43 (m, 4H), 9.58 (s, 1H); 19F
NMR (CDCl3, 282 MHz)
d
ꢀ61.38 (s, 6F); IR (KBr, cmꢀ1): 3365, 3052,
1693, 1567, 1517, 1468, 1381, 1276, 1162, 1127, 965, 890, 843, 743,
682; ESI-MS m/z: 383.9 ([MþH]þ); elemental analysis: found C:
59.22, H: 3.30, N: 3.50 calculated for (C19H11F6NO) C: 59.54, H:
2.89, N: 3.65 (%).
a
1
Symmetry codes: a) ꢀxþ2, y, ꢀzþ /2.
4.2.3. Synthesis of Zn3(BFHQ)6 (5). A mixture of Zn(AcO)2$2H2O
(3.7 mg, 0.01 mmol), 4 (3.8 mg, 0.01 mmol), H2O (0.5 mL), and
MeOH (2 mL) in a capped vial was heated at 80 ꢁC for one day. Red
rod-like crystals of 5 were filtered, washed with MeOH and Et2O,
and dried at room temperature. Yield: 3.0 mg (72%). 1H NMR (d6-
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (20802010, 21032006, 20972178) and 211
project of Guangdong Province.
DMSO, 300 MHz)
d
6.93 (d, J¼7.2 Hz, 1H), 7.04 (d, J¼8.7 Hz, 1H),
7.43 (t, J¼8.1 Hz, 1H), 8.04 (d, J¼16.5 Hz, 1H), 8.10 (s, 1H), 8.19 (d,
J¼9.0 Hz, 1H), 8.39 (s, 2H), 8.49 (d, J¼8.1 Hz, 1H), 8.85 (d,
Supplementary data
J¼16.5 Hz, 1H); 19F NMR (CDCl3, 282 MHz)
ꢀ61.32 (s, 6F); IR (KBr,
d
n
/cmꢀ1): 3053, 2917, 1638, 1458, 1308, 1105, 944, 797, 701, 684,
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2010.09.039. These data in-
clude MOL files and InChiKeys of the most important compounds
described in this article.
566, 536, 505, 496, 442; elemental analysis: found C: 55.12, H:
2.30, N: 3.50 calculated for (C38H20F12N2O2Zn) C: 54.99, H: 2.43, N:
3.38 (%).
4.3. X-ray crystallography
References and notes
1. Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913.
2. Rai, V. K.; Srivastava, R.; Kamalasanan, M. N. Synth. Met. 2009, 159, 234.
3. Matsumoto, N.; Miyazaki, T.; Nishiyama, M.; Adachi, C. J. Phys. Chem. C 2009,
113, 6261.
Red rod-like crystals of Zn3L6, 5 were obtained in high yield by
heating 4 and Zn(AcO)2$2H2O at 80 ꢁC in H2O/MeOH for one day.
A single-crystal X-ray diffraction study on 5 revealed a neutral

8640
Y.-P. Huo et al. / Tetrahedron 66 (2010) 8635e8640
4. Liu, Z. W.; Bian, Z. Q.; Hao, F.; Nie, D. B.; Ding, F.; Chen, Z. Q.; Huang, C. H. Org.
Electron. 2009, 10, 247.
15. Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue, Y.; Sato, F.;
Tokito, S. J. Am. Chem. Soc. 2004, 126, 8138.
5. Tao, Y. T.; Wang, Q.; Shang, Y.; Yang, C. L.; Ao, L.; Qin, J. G.; Ma, D. G.; Shuai, Z. G.
Chem. Commun. 2009, 77.
16. Shi, M. M.; Chen, H. Z.; Sun, J. Z.; Ye, J.; Wang, M. Chem. Commun. 2003, 1710.
17. Shi, Y. W.; Shi, M. M.; Huang, J. C.; Chen, H. Z.; Wang, M.; Liu, X. D.; Ma, Y. G.; Xu,
H.; Yang, B. Chem. Commun. 2006, 1941.
18. Matsumura, M.; Akai, T. Jpn. J. Appl. Phys. 1996, 35, 5357.
19. Zhong, C.; Wu, Q.; Guo, R.; Zhang, H. Opt. Mater. 2007, 30, 870.
20. Ramesh, V.; Umasundari, P.; Das, K. K. Spectrochim. Acta, Part A 1998, 54, 285.
21. Perkovic, M. W. Inorg. Chem. 2000, 39, 4962.
22. El-Dissouky, A. Spectrochim. Acta, Part A 1987, 43, 1177.
23. Wu, Q.; Esteghamatian, M.; Hu, N. X.; Popovic, Z. D. Chem. Mater. 2000, 12, 79.
24. Huang, Q. L.; Li, J. F.; Marks, T. J. J. Appl. Phys. 2007, 101, 093101.
25. Sapochak, L. S.; Benincasa, F. E.; Schofield, R. S.; Baker, J. L.; Riccio, K. K. C.;
Fogarty, D.; Kohlmann, H.; Ferris, K. F.; Burrows, P. E. J. Am. Chem. Soc. 2002, 124,
6119.
6. Chang, C. H.; Lu, Y. J.; Liu, C. C.; Yeh, Y. H.; Wu, C. J. Display Technol. 2007, 3, 193.
7. Liedtke, A.; O’Neill, M.; Wertmoller, A.; Kitney, S. P.; Kelly, S. M. Chem. Mater.
2008, 20, 3579.
8. Gather, M. C.; Alle, R.; Becker, H.; Meerholz, K. Adv. Mater. 2007, 19, 4460.
9. Mishra, A.; Nayak, P. K.; Periasamy, N. Tetrahedron Lett. 2004, 45, 6265.
10. Cui, Z.; Kim, S. H. Chin. Sci. Bull. 2004, 49, 797.
11. Xie, J.; Ning, Z.; Tian, H. Tetrahedron Lett. 2005, 46, 8559.
12. Radek, P.; Pavel, A. J. Org. Lett. 2003, 5, 2769.
13. Wang, T. T.; Zeng, G. C.; Zeng, H. P.; Liu, P. Y.; Wang, R. X.; Zhang, Z. J.; Xiong, Y. L.
Tetrahedron 2009, 65, 6325.
14. Zeng, H. P.; Wang, G. R.; Zeng, G. C.; Li, J. Dyes Pigments 2009, 83, 155.