Azadipyrromethene dye with a fully chelated boron atom

Full text of DOI:10.1007/s10593-009-0179-9

Chemistry of Heterocyclic Compounds, Vol. 44, No. 10, 2008
AZADIPYRROMETHENE DYE WITH
A FULLY CHELATED BORON ATOM
Yu. P. Kovtun, V. P. Yakubovskiy, and M. P. Shandura
Keywords: azadipyrromethene dye, dipyrromethene dye, BODIPY.
Among the variety of approaches to the modification of the basic structure of boron complexes of
dipyrromethene dyes, also known as 4-bora-3a,4a-diaza-s-indacenes or BODIPY (BDP), the method proposed
by Kim et al. [1] stands out for its originality. Structure 2 described by Kim [1] is a dipyrromethene with a fully
chelated boron atom.
I
NO2
O
NH4OAc
HOAc
N
N
B
OMe
OH
O
O
2
1
OMe
OMe
MeO
MeO
N
N
B
BF3–Et2O
N
N
N
N
i-Pr2NEt
HO
OH
O
O
3
4
1 – λmax 630 nm (ε 46 000), λem 654 nm, φ 0.41; 3 – λmax 623 nm (ε 54 000);
4 – λmax 726 nm (ε 70 000), λem = 741 nm, φ 0.38
__________________________________________________________________________________________
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev 02094, Ukraine;
e-mail: kovtun@ioch.kiev.ua. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1591-1592,
October, 2008. Original article submitted May 23, 2007, submitted after revision February 12, 2008.
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0009-3122/08/4410-1298©2008 Springer Science+Business Media, Inc.

This dye is much more intense in its color than starting difluoroboryl derivative and its fluorescence
properties also are significantly altered (here and subsequently, the spectral properties are given for chloroform
solutions). However, the most interesting feature for dye 1 is its spiral chirality, the first example for this type of
compound.
Azapyrromethenes are preparatively more available because their synthesis needs no correspondingly
substituted pyrroles. Out of the known Scheme (for example, [2]) we obtained the azaanalogue of dye 1.
As expected, dye 4 has a more intense color than its analog 1, while its quantum yield at 38% for the
near IR region is very high, which makes preparatively-available azadipyrromethene 4 among the most efficient
long-wavelength luminophores.
1
The H NMR spectra were taken on a Varian VXR-300 spectrometer at 300 MHz with TMS as the
internal standard. The electronic absorption spectra were taken on a Shimadzu UV-3100 spectrophotometer. The
fluorescence spectra were taken on a Varian Cary Eclipse spectrometer.
[5-(2-Hydroxyphenyl)-3-(4-methoxyphenyl)-1H-pyrrol-2-yl][5-(2-hydroxyphenyl)-3-(4-methoxy-
phenyl)pyrrol-2-ylidene]amine (3). A mixture of nitro ketone 2 (1.5 g, 5 mmol), ammonium acetate (7.7 g,
100 mmol), and acetic acid (18 ml) was heated at 100°C for 4 h. After cooling, the precipitate was filtered off
and washed with acetic acid to give 0.41 g (38%) compound 3, mp >250°C. 1H NMR spectrum (DMSO), δ, ppm
(J, Hz): 3.85 (6H, s, 2OCH3); 7.03 (6H, m, H arom); 7.13 (2H, d, J = 8.1, H arom); 7.37 (2H, t, J = 7.8, H arom);
7.65 (2H, s, H-4); 8.05 (6H, m, H arom); 11.7 (2H, br. s, OH). Found, %: C 75.32; H 4.94; N 7.81. C34H27N3O4.
Calculated, %: C 75.40; H 5.02; N 7.76.
Boron Chelate of [5-(2-Hydroxyphenyl)-3-(4-methoxyphenyl)-1H-pyyrol-2-yl][5-(2-hydroxy-
phenyl)-3-(4-methoxyphenyl)pyrrol-2-ylidene]amine (4).
A mixture of
dipyrromethene 3 (0.27 g,
0.5 mmol), diisopropylethylamine (0.64 g, 5 mmol), and boron trifluoride etherate (1.06 g, 7.5 mmol) in
anhydrous toluene (40 ml) was heated at reflux for 1 h. Then, the solution was washed with water, dried over
sodium sulfate, evaporated, and subjected to chromatography on an alumina column using carbon tetrachloride–
1
ethyl acetate as the eluent to give 0.14 g (50%) compound 4 mp >250°C. H NMR spectrum (CDCl3), δ, ppm
(J, Hz): 3.91 (6H, s, 2OCH3); 7.01 (6H, m, H arom); 7.09 (2H, d, J = 7.5, H arom); 7.13 (2H, s, H-4); 7.40 (2H,
t, J = 8.4, H arom); 7.85 (2H, d, J = 7.8, H arom); 8.13 (2H, d, J = 9.0, H arom). Mass spectrum, m/z (Irel, %):
549 [M]+ (100). Found, %: C 74.82; H 4.51; N 7.81. C34H24BN3O4. Calculated, %: C 74.33; H 4.40; N 7.65.
REFERENCES
1.
2.
H. Kim, A. Burghart, M. B. Welch, J. Reibenspies, and K. Burges, Chem. Commun., 1889 (1999).
M. J. Hall, S. O. McDonnel, J. Killoran, and D. F. O'Shea, J. Org. Chem., 70, 5571 (2005).
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