Chemistry Letters Vol.33, No.10 (2004)
1245
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0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
3
4
5
6
7
A typical procedure of 2c: To a mixture of 1 (546 mg,
1 mmol) and tetrakis(triphenylphosphine) palladium (0)
(150 mg, 5.0 mol %) in benzene (20 mL) were added 1-naph-
thylboronic acid (600 mg, 3.5 mmol) in ethanol (5 mL) and
aqueous 2 M sodium carbonate solution (5 mL) under an ar-
gon atmosphere and the mixture was heated at 80 ꢄC for 15 h.
After the reaction mixture was evaporated in vacuo to re-
move benzene, it was filtered off and washed with water.
The insoluble solid was dissolved in chloroform and washed
with brine. The water layer was extracted with chloroform.
The combined organic layers were dried over anhydrous
magnesium sulfate and evaporated in vacuo to dryness.
The residue was recrystallized from chloroform to give 2c
in 74% yield (508 mg, 0.74 mmol) as white powder: mp
312–313 ꢄC; IR (KBr, cmꢂ1) 1608, 1570, 1364, 1180,
1019, 851, 436, 787, 772; 1H NMR (CDCl3) ꢁ 7.48–7.60
(m, 12 H, naphthyl H), 7.77 (d, J ¼ 8:3 Hz, 6 H, phenylene
H), 7.91–8.01 (m, 9 H, naphthyl H), 8.99 (d, J ¼ 8:3 Hz, 6 H,
phenylenþe H); FAB–MS (NBA, positive) m=z 688
0
1
2
3
4
5
Time /
µs
Figure 1. Transient photocurrent signal for a 2c single device
between ITO anode and Al cathode recorded at field
E ¼ 3:8 ꢁ 10ꢂ5 V cmꢂ1 and at 25 ꢄC. The film thickness was
3.31 mm.
is the applied voltage. High electron drift mobility can be esti-
mated for 2c to be 8:0 ꢁ 10ꢂ4 cm2 Vꢂ1 sꢂ1 at 25 ꢄC (3:8 ꢁ
10ꢂ5 V cmꢂ1), depending on the temperature and the electric
field in the range from 3:2 ꢁ 10ꢂ4 to 1:2 ꢁ 10ꢂ3 cm2 Vꢂ1 sꢂ1
(from ꢂ50 to 60 ꢄC) and from 7:6 ꢁ 10ꢂ4 to 1:1 ꢁ 10ꢂ3
cm2 Vꢂ1 sꢂ1 (from 3:0 ꢁ 10ꢂ5 to 7:6 ꢁ 10ꢂ5 V cmꢂ1).10 The
electron drift mobility of 2c is 4 times as large as that
(2:0 ꢁ 10ꢂ4 cm2 Vꢂ1 sꢂ1 at 27 ꢄC/6:4 ꢁ 10ꢂ5 V cmꢂ1) of a
silole-based material5 and competes with bathophenanthroline6
(5:2 ꢁ 10ꢂ4 cm2 Vꢂ1 sꢂ1 at 25 ꢄC/5:5 ꢁ 10ꢂ5 V cmꢂ1).
.
½ðM þ 1Þ ꢅ. Anal. C51H33N3 0.05CHCl3: C, 88.38; H,
4.80; N, 6.06. Found: C, 88.15; H, 4.86, N 6.05.
J. Pang, Y. Tao, S. Freiberg, X.-P. Yang, M. D’Iorio, and
S. Wang, J. Mater. Chem., 12, 206 (2000).
8
9
In conclusion, 2,4,6-tris[4-(1-naphthyl)phenyl]-1,3,5-tri-
azine is an attractive amorphous glassy electron-transporting
material, which has high electron drift mobility of 8:0 ꢁ 10ꢂ4
cm2 Vꢂ1 sꢂ1 at 25 ꢄC (3:8 ꢁ 10ꢂ5 V cmꢂ1).
Electron-transport in disordered glassy amorphous mole-
cules occurs via a hopping mechanism. Many electron-trans-
porting materials including heterocyclic rings resulted in dis-
persive electron transport,2a,2e,6 which is attributed to dipolar
disorder arising from a fluctuation of energy in electron hop-
This work was financially supported in part by a Grant-
in-Aid for Scientific Priority Area (No. 15750157) from the
Ministry of Education, Culture, Sports, Science and Technology
of Japan.
ping sites: P. M. Borsenberger and H. Bassler, J. Chem.
Phys., 95, 5327 (1991).
¨
10 Probably, the high electron mobility in 2c is attributed to fa-
vored ꢂ-stacking among the molecules to enjoy the electron
hopping even in the amorphous state, as it is known that
some 1,3,5-triazine derivatives tend to aggregate via the
ꢂ-stacking interactions: i.e. columnar liquid crystals. For
triazine-based columnar liquid crystals see: a) C. Lee and
T. Yamamoto, Tetrahedron Lett., 42, 3993 (2001). b) K.
Pieterse, A. Lauritsen, A. P. H. J. Schenning, J. A. J. M.
Vekeman, and E. W. Meijer, Chem.—Eur. J., 9, 5597
(2003). c) H. Lee, D. Kim, H.-K. Lee, W. Qiu, N.-K. Oh,
W.-C. Zin, and K. Kim, Tetrahedron Lett., 45, 1019
(2004). d) H. Bock, A. Babeau, I. Seguy, P. Jolinat, and
P. Destruel, ChemPhysChem, 2002, 532.
References and Notes
For reviews of OLEDs see: a) U. Mitschke and P Bauerle, J.
1
¨
Mater. Chem., 10, 1471 (2000). b) Y. Shirota, J. Mater.
Chem., 10, 1 (2000). c) S. R. Forrest, D. D. C. Gradley,
and M. E. Thompson, Adv. Mater., 15, 1043 (2003).
2
For selected references of electron-transporting materials
see: a) J. Bettenhausen, P. Strohriegl, W. Brutting, H.
¨
Tokuhisa, and T. Tsutsui, J. Appl. Phys., 82, 4957 (1997).
b) J. Kido, M. Kimura, and K. Nagai, Chem. Lett., 1996,
47. c) M. Jandke, P. Strohriegl, S. Berleb, E. Werner, and
W. Brutting, Macromolecules, 31, 6434 (1998). d) T. Noda
¨
and Y. Shirota, J. Am. Chem. Soc., 120, 9714 (1998). e)
Published on the web (Advance View) August 28, 2004; DOI 10.1246/cl.2004.1244