In summary, two novel F-B cored fluorescent complexes
were designed and efficiently synthesized. Their crystal struc-
tures and photophysical and electrochemical properties were
investigated. The well-ordered molecular packing, strong lu-
minescence, and low LUMO levels indicated their potential as
electron-transport materials in electroluminescent (EL) devices.
Efforts for further electron-optical applications are underway.
Experimental Section
Compound 5: Route A. A solution of compound 4 (0.40 g, 3
mmol), 2-pyridylaldehyde (0.64 g, 6 mmol), and K CO (0.80 g, 6
2 3
mmol) in 20 mL of toluene was heated to 100 °C for 12 h. Toluene
was removed in vacuum, and the resulting mixture was extracted
with dichloromethane. The extract was purified by silica gel column
chromatography using ethyl acetate as eluent to afford compound
FIGURE 7. Diagrams showing the HOMO and LUMO levels of 1
and 2.
5. Yield: 0.44 g (68%). The products were used without further
purifications.
TABLE 1. Values of the Electronic States (HOMO/LUMO Levels)
and Energy Gap (eV)
Route B. In a sealed kettle 1.00 g of 3 (6.8 mmol), 3 mL of
2-methylpyridine (34 mmol), and 0.20 g of fresh melted zinc
chloride were mixed together and heated at 170 °C for 6 h. The
resulting brown mixture was extracted with water/dichloromethane.
The extract was purified by silica gel column chromatography using
ethyl acetate as eluent to afford compound 5. Yield: 1.11 g (74%).
LUMO
HOMO
Eg
cmpd
Vcv
Vca
Vcv
Vca
Vcv
Vca
VUV
1
2
-3.22
-3.45
-2.67
-2.83
-6.07
-6.05
-6.20
-6.09
2.85
2.60
3.53
3.26
2.54
2.32
Compound 1. To the solution of 0.17 g of 5 (0.75 mmol) in 10
a
Vcv: the value from cyclic voltammetry; Vca: the value from MO
calculation; VUV: the value estimated by using the UV-vis absorption edge.
mL of CH
Cl
were added 0.4 mL of N-ethyldiisopropylamine and
O. The mixture was stirred under nitrogen for 3 h
2
2
1
mL of BF
3
‚Et
2
at room temperature. The residues were purified by silica gel column
chromatography using dichloromethane as eluent to afford com-
pound 1. Yield: 0.1 g (50%), mp: 247-249 °C. H NMR (500
The diagrams of the HOMO and LUMO levels of TM-
BODIPY were studied for comparison (Supporting Information).
It showed that the HOMO and LUMO levels of TM-BODIPY
were delocalized in the whole atomic part, with small differences
in the dipole moments.13 In the present work, the LUMO
distribution of both compounds was donated by all atomic
orbitals in the aromatic rings, while contributions to the HOMO
distribution were mainly from part A. Therefore, intramolecular
charge transfer (ICT) from part A to part B was suggested in 1
and 2, which could partly explain their broad bands in
1
MHz, DMSO) δ 6.96 (s, H), 7.68-7.72 (m, 2H), 7.77-7.81 (m,
H), 7.84 (s, H), 7.86 (s, H), 8.06-8.08 (d, H), 8.31-8.34 (m, H),
8
1
1
.75-8.77 (d, H); 13C NMR (100 MHz, DMSO) δ 94.7, 122.1,
23.1, 123.6, 125.4, 130.3, 131.9, 133.3, 136.0, 142.5, 143.7, 144.7,
+
49.4, 170.5; TOF MS EI : calcd for C14
H
9
2 2
BF N O 270.0776,
found 270.0781.
Compound 2. Starting from compound 3 (0.40 g, 3 mmol),
-quinoline carbaldehyde (0.94 mL, 6 mmol), and K CO (0.80 g,
mmol) in 20 mL of toluene, compound 6 was synthesized and
2
6
2
3
1
4
15
absorption and large Stokes shifts.
The calculated HOMO-LUMO band gap of 1 was larger
than that of 2, which was consistent with the trend of the spectra.
purified by a procedure similar to that of route A for compound 5
described above. Yield: 0.48 g (60%).
To the solution of 0.217 g of compound 6 (0.8 mmol) in 10 mL
(Table 1) The increased conjugation system in 2 reduced the
of CH
mL of BF
2
Cl
2
were added 0.5 mL of N-ethyldiisopropylamine and 1
O. The mixture was stirred under nitrogen for 3 h at
LUMO energy effectively but the HOMO energy weakly, hence
red-shifting both absorption and emission spectra.
3
‚Et
2
room temperature. The residues were purified in a way similar to
that for purifying compound 1. Yield: 0.141 g (55%), mp: 278-
1
(
12) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
280 °C. H NMR (500 MHz, DMSO) δ 7.07 (s, H), 7.75-7.78
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K.
N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo, J.;
Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.;
Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels,
A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I. R.; Martin, L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03,
Revision B.05; Gaussian, Inc.: Pittsburgh, PA, 2003.
(
8
m, 2H), 7.82-7.85 (m, 2H), 7.89-7.90 (d, H), 7.98-8.02 (m, H),
.13-8.17 (m, 2H), 8.71-8.73 (d, H), 8.77-8.78 (d, H); 13C NMR
(
1
400 MHz, DMSO) δ 95.6, 122.7, 123.4, 123.9, 127.5, 127.6, 129.8,
+
30.4, 132.5, 133.0, 133.6, 135.4, 143.7, 152.9; TOF MS EI : calcd
for C18 O 320.0932, found 320.0936.
2 2
H11BF N
Acknowledgment. This work was supported by NSF of
China (No. 20406004, 20572012, 20536010). We also thank
Dr. Cheng He for the suggestions on the crystallographic
analyses.
Supporting Information Available: General experimental
methods, compound characterization data, crystallographic informa-
tion files (CIF), crystallographic analyses based on X-ray deter-
mination and related H-bond data for 1 and 2. This material is
available free of charge via the Internet at http://pubs.acs.org.
(
13) Bergstrom, F.; Mikhalyoy, I.; Hagglof, P.; Wortmann, R.; Ny, T.;
Johansson, L. J. Am. Chem. Soc. 2002, 124, 196-204.
14) Cui, Y.; Liu, Q.; Bai, D.; Jia, W.; Tao, Y.; Wang, S. Inorg. Chem.
005, 44, 601-609.
15) Peng, X.; Song, F.; Lu, E.; Wang, Y.; Zhou, W.; Fan, J.; Gao, Y.
J. Am. Chem. Soc. 2005, 127, 4170-4171.
(
2
(
JO702265X
1
574 J. Org. Chem., Vol. 73, No. 4, 2008