Communications
solid was separated by filtration, washed with acetone, and purified by
column chromatography.
similar. Thus, the intensities of the vibrational transitions are
strongly shifted towards the 00 transition. This effect com-
bined with the appearance of the 00 band above 800 nm in the
spectrum results in 4a’ coming close to being an ideal
selective NIR absorber (intense absorption in the near-
infrared range, but extremely low absorptions in the visible
range from 700 to 380 nm), as is shown by the absorption of
4a’ in methylcyclohexane (Figure 3). Selective NIR absorbers
are of technical interest for NIR laser welding of transparent
polymers.[16]
3a: Column chromatography (silica gel/CHCl3) afforded 3a as a
green crystalline powder in 33% yield. 1H NMR (400 MHz, CDCl3):
d = 14.78 (brs, 2H; N-H), 7.96 (d, 3J = 8.8 Hz, 2H; H-4’), 7.77 (m, 8H;
3
AA’, H-7’, H-8’), 7.65 (d, J = 8.8 Hz, 2H; H-3’), 7.63 (s, 2H; H-5’),
7.14 (m, 4H; XX’), 4.10 (t, 3J = 6.6 Hz, 4H; OCH2), 1.86 (m, 4H;
OCH2CH2), 1.6–1.3 (m, 38H; alkyl, tert-butyl), 0.92 ppm (t, 3J =
6,8 Hz, 6H; CH3). MALDI-MS: m/z calcd: 957.6 [M+H]+, 979.6
[M+Na]+, 995.5 [M+K]+; found: 956.8, 978.8, 995.7; UV/Vis/NIR
(CHCl3): n00 = 13700 cmꢀ1 (l00 = 731 nm); e00 = 118000mꢀ1 cmꢀ1, f =
0.71. Elemental analysis calcd (%) for C64H72N6O2 [M =
957.30 gmolꢀ1]: C 80.30, H 7.58, N8.78; found: C 80.36, H 7.67, N
8.37.
4a: BF3·Et2O (0.98 mL, 1.77 g, 7.38 mmol) was added to a
solution of 3a (500 mg, 0.52 mmol) in ortho-dichlorobenzene
(15 mL) at reflux in a nitrogen atmosphere. After 10 min, Hünigꢀs
base (0.22 mL, 169 mg, 1.31 mmol) was added and the mixture heated
at reflux for a further 10 min. The reaction was then stopped. After
removal of the solvent and excess BF3·Et2O, the crude product was
dissolved in methanol in an ultrasonic bath and separated by
filtration. Column chromatography (silica gel/CH2Cl2) afforded 4a
in 76% yield (420 mg, 0.40 mmol) as a green powder. 1H N MR
(400 MHz, C2D2Cl4): d = 8.42 (m, 2H; H-8’), 8.14 (d, 3J = 9.3 Hz, 2H;
H-4’), 7.74 (dd, 3J = 9.5 Hz, 4J = 2.2 Hz, 2H; H-7’), 7.72 (d, 4H; AA’),
3
7.66 (m, 4H; H-3’,H-5’), 7.06 (m, 4H; XX’), 4.08 (t, J = 6.6 Hz, 4H;
OCH2), 1.85 (m, 4H; OCH2CH2), 1.53 (m, 4H; O(CH2)2CH2), 1.45–
1.2 (brs, 16H; alkyl), 1.36 (s, 18H; tert-butyl), 0.91 ppm (t, 6H; CH3).
MALDI-MS: m/z calcd: 1053.6 [M+H]+, 1075.6 [M+Na]+; found:
1053.1, 1076.1; UV/Vis/NIR (CHCl3): nA00 = 13260 cmꢀ1 (l0A0
=
=
754 nm), e00 = 205000mꢀ1 cmꢀ1
,
f = 0.83; nF00 = 12940 cmꢀ1 (lF00
773 nm), FF = 0.59. Elemental analysis calcd (%) for
C64H70B2F4N6O2 [M = 1052.90 gmolꢀ1]: C 73.01, H 6.70, N7.98;
found: C 72.51, H 6.95, N7.83.
Figure 3. Absorption (c) and fluorescence (g) of 4a’ in methyl-
cyclohexane at room temperature.
4a’: A mixture of 3a (250 mg, 0.26 mmol) and (321 mg, 1.6 mmol)
chlorodiphenylborane was refluxed in absolute xylene (15 mL) under
nitrogen. After 10 min at reflux, the reaction was stopped, xylene
removed, and the residue purified by column chromatography (silica
gel/CH2Cl2) to afford 4a’ as a yellow solid in 56% yield (189 mg,
In conclusion, the condensation of sufficiently soluble
diketopyrrolopyrroles with 2-heteroarylacetonitriles provides
a new approach to dyes 3 with strong NIR absorptions.
Stiffening the chromophore affords NIR fluorophores 4
which results in spectacular properties becoming available.
Future applications of the dyes as NIR labels could be
accomplished by their functionalization. The first steps
towards this goal were already achieved by the synthesis of
systems with terminal alkene groups.
1
3
0.147 mmol). H NMR (400 MHz, C2D2Cl4): d = 8.18 (d, J = 9.5 Hz,
2H; H-8’), 7.83 (d, 3J = 9.3 Hz, 2H; H-4’), 7.58 (d, 3J = 9.3 Hz, 2H; H-
3
4
3’), 7.34 (m, 10H; H-5’, m-phenyl), 7.15 (dd, J = 9.5 Hz, J = 2.2 Hz,
2H; H-7’), 7.10 (m, 12H; o- ,p-phenyl), 6.52 (d, 4H; AA’), 6.06 (m,
4H; XX’), 4.02 (t, J = 6.6 Hz, 4H; OCH2), 1.86 (m, 4H; OCH2CH2),
1.53 (m, 4H; O(CH2)2CH2), 1.48–1.25 (brs, 16H; alkyl), 1.16 (s, 18H;
tert-butyl), 0.93 ppm (m, 6H; CH3). MALDI-MS: m/z calcd: 1285.7
[M+H], found: 1285.5; UV/Vis/NIR (CHCl3): nA00 = 12210 cmꢀ1 (l0A0
=
821 nm), e00 = 256000mꢀ1 cmꢀ1
,
f = 0.76; nlF00 = 12030 cmꢀ1 (lF00
=
831 nm), FF = 0.53. Elemental analysis calcd (%) for C88H90B2N6O2
[M = 1285.32 gmolꢀ1]: C 82.23, H 7.06, N6.54; found: C 81.59, H 7.11,
N6.49.
Experimental Section
The fluorescence quantum yields were determined on diluted
solutions (c < 2 10ꢀ6 m) with
a A
home-made spectrometer.[7]
Received: November 23, 2006
Revised: January 11, 2007
Published online: April 5, 2007
HeNe laser or a 804-nm diode laser were used as the excitation
sources, and a germanium diode (NORTHCOAST) used as the
detector. CZ 144 (= DY-665-X, Dyomics) was used as a reference dye
(FF = 0.60 in CH2Cl2).[17]
Keywords: chromophores · dyes/pigments · fluorophores ·
General procedure for the synthesis of NIR dyes 3: POCl3
(8 mmol) was added to a mixture of DPP 1 (1 mmol) and hetero-
arylacetonitrile 2 (2.5 mmol) in absolute toluene (20 mL) at reflux in
a nitrogen atmosphere. The reaction was monitored by UV/Vis/NIR
spectroscopy and thin-layer chromatography. As soon as the DPP was
used up or short-wavelength-absorbing by-products increased, the
reaction was stopped. After removal of the toluene and excess POCl3
by vacuum distillation, the crude product was dissolved in CH2Cl2 and
neutralized with aqueous NaHCO3 solution. The organic phase was
separated and dried with MgSO4. After removing the solvent, the
residue was dissolved in acetone in an ultrasonic bath. The remaining
.
polymerwelding · UV/Vis/NIR spectroscopy
[1] G. Scheibe, E. Daltrozzo, O. Wörz, J. Heiß, Z. Phys. Chem. N. F.
1969, 64, 97 – 114.
[2] a) E. Daltrozzo, W. Sulger, 9th International Colour Symposium,
Engelberg 1985, Abstracts p. 26; b) E. Daltrozzo, PhD thesis,
Technical University of Munich, 1965; c) W. Sulger, PhD thesis,
University of Konstanz, 1981.
3752
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2007, 46, 3750 –3753