Chemistry Letters Vol.33, No.11 (2004)
1451
104 Mꢂ1 cmꢂ1) for 2. As for as the IR is concerned, the com-
pound 1 and 2 have a very similar pattern ranging from 3000
to 1000 cmꢂ1. But 1 has an additional middle and broad absorp-
tion at ꢃ3450 cmꢂ1 assigned to the N–H stretching vibration as
compared to 2.
(1993), Vol. 2; (1993), Vol. 3; (1996), Vol. 4.
2
M. J. Stillman and T. Nyokong, in ‘‘Phthalocyanines:
Properties and Applications,’’ ed. by C. C. Lez-noff and
A. B. P. Lever, VCH, New York (1989), Vol. 1, Chap. 3.
M. Aouia, G. Cheng, V. O. Kennedy, M. E. Kenny, and
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Commun., 1997, 1353.
N. Kobayashi, N. Sasaki, Y. Higashi, and T. Osa, Inorg.
Chem., 34, 1636 (1995).
M. J. Cook, A. J. Dunn, S. D. Howe, and A. J. Thomson,
J. Chem. Soc., Perkin Trans. 1, 1988, 2453.
H. Kobayashi, Y. Higashi, and T. Osa, Chem. Lett., 1994,
1813.
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3
4
5
6
7
1.25
1.00
0.75
1
2
0.50
0.25
0.00
8
9
400
500
600
700
800
Wave length (nm)
Figure 2. The absorption spectra of compound 1 and 2 adsorb-
ed in thin TiO2 film.
10 Compound 1 and 2 should be the mixture of their regioisomers.
11 H. Isago, Y. Kagava, and S. I. Nakajima, Chem. Lett., 2003,
112.
12 T. Muto, T. Temma, M. Kimura, K. Hanabusa, and H. Shirai,
J. Org. Chem., 66, 6109 (2001).
13 There are too many references upon this, so we just list some of
them here: a) J. Fasihi, Y. Yamini, F. Nourmohammadan, and
N. Bahramifar, Dyes Pigm., 63, 161 (2004). b) M. S. Yen and
I. J. Wang, Dyes Pigm., 63, 1 (2004). c) T. Hihara, Y. Okada,
and Z. Morita, Dyes Pigm., 61, 199 (2004). d) P. Makedonski,
M. Brandes, W. Grahn, W. Kowalsky, J. Wichern, S. Wiese,
and H. H. Johannes, Dyes Pigm., 61, 109 (2004).
It is very interesting that 1 and 2 can easily and stably be ad-
sorbed onto the surface of TiO2. Their absorption spectra adsorb-
ed onto thin TiO2 film is shown in Figure 2. They show more in-
tensive absorption in the visible region than the Q-band in the
near-IR region, and the Q-band turns much broad compared to
their spectra in THF solution.
Previous reports on Pcs were mainly focused on the near-IR
absorption band and gave little indication of the absorptions in
the visible region owing to their very weak absorptions com-
pared to the Q-band. The notable red-shift of the Q-band as well
as the shoulder is a common feature of Pcs’ electronic absorption
spectra, which can be assigned to an electronic transition to a
higher energy level, and to the elongation of ꢀ-system of phtha-
locyanines.12 The new and obvious absorption band appearing in
the visible region for the new Pcs could be attributed to the com-
bination of the red-shift of B-band and the absorption of the azo
group introduced onto the Pc ring. It is well known that azo com-
pounds usually show intense absorptions in the visible region
(400–650 nm).13 For instance, the precursor 3 produces an in-
tense absorption from 450 to 550 nm (Figure 1). Obviously, here
is the first observation of the new absorption band having effec-
tively broadened the spectral absorption range of the Pcs. This
kind of additional absorptions is really uncommon, and might
entrust some novel opto-electronic properties to the Pcs.
In summary, we have prepared a new class of Pcs containing
azo structure on the periphery and enriched categories of Pcs.
The present result provides an important suggestion for enhanc-
ing the absorptions and enlarging the range of spectral absorp-
tions for Pcs, which may entrust some new optical, electronic,
and chemical properties to them. They are expected to find
applications in organic opto-electronic conversion devices such
as solar cells and photoconductors, in which research is currently
under way.
14 Preparation: Compound 3 was obtained by following normal
method for synthesis of azo compounds. Compound 1: 40-
N,N-diethylaminoazobenzene-3,4-dicarbonitrile (3.3 mmol),
DBU (0.5 mL) and 1-pentanol (30 mL) were mixed in a 100-
mL three-neck flask equipped with a mechanical stir and re-
fluxed for 24 h. A black powder was filtered off, washed with
ethanol and acetone, in turn, then extracted with ethanol in a
Soxhlet apparatus thoroughly, and dried under vacuum, giving
the product of 301 mg (yield: 31%). Compound 2: According
to the same conditions as synthesis of 1 except that CuAc2
(2 mmol) was added in reaction mixture. A black-brown pow-
der was filtered off, washed with ethanol, dilute hydrochloric
acid, water, ethanol and acetone, in turn, then extracted with
ethanol in a Soxhlet apparatus thoroughly, and dried under
vacuum, giving the product of 440 mg (yield: 41%). Selected
Data: Compound 3: mp 116–118 ꢄC; UV–vis ꢁmax (THF)
495 nm; MS (EI) m=z (relative intensity) 303 [Mþ, 65], 288
(100), 260 (15), 148 (25), 133 (28); 1H NMR (300 MHz,
CDCl3) ꢂ 1.20 (t, 6H), 3.47 (q, 4H), 6.97–7.25 (m, 7H); Anal.
Calcd for 3: C, 71.29; H, 5.61; N, 23.10%. Found: C, 71.26; H,
5.67; N, 23.30%. Compound 1: UV–vis (THF) ꢁmax (log ")
759 (5.176), 525 (4.775), 415 (4.876); IR (KBr, cmꢂ1) 3450
(m), 2970 (w), 1599 (s), 1513 (m), 1392 (m), 1351 (m), 1269
(w), 1139 (m), 1092 (w); MS (MALDI-TOF) m=z calcd for 1
1215.4, found 1214.1 ½Mþ ꢂ 1ꢅ; Anal. Calcd for 1: C, 71.17;
H, 5.77; N, 23.06%. Found: C, 70.62; H: 5.79; N, 22.70%.
Compound 2: UV–vis (THF) ꢁmax (log ") 735 (5.212), 510
(4.722), 415 (4.770); IR (KBr, cmꢂ1) 2970 (w), 1598 (s),
1512 (m), 1390 (m), 1346 (m), 1268 (w), 1140 (m),
1092(w); MS (MALDI-TOF) m=z calcd. for 2: 1276.9, found:
1275.3 ½Mþ ꢂ 1ꢅ; Anal. Calcd for 2: C, 67.74; H, 5.33; N,
21.95%. Found: C, 67.34; H, 5.19; N, 21.45%.
This work was supported by the National 863 Program
of China (715-Z36-1-98) and the National Natural Science
Foundation of China (Project no. 60276007).
References and Notes
‘‘Phthalocyanines: Properties and Applications,’’ ed. by C. C.
Leznoff and A. B. P. Lever, VCH, New York (1989), Vol. 1;
1
Published on the web (Advance View) October 9, 2004; DOI 10.1246/cl.2004.1450