A NEW CLASS OF ELECTROLUMINESCENT METAL COMPLEXES
313
Table 1. Elemental analysis results and melting points of compounds L1, L2, I, and II
Content (found/calculated), %
Compound Empirical formula
Mp, °C
C
H
N
S
Zn
L1
L2
I
C10H10N2O2S
55.74/54.04 4.78/4.54 12.15/12.60 14.34/14.34
54.00/56.25 4.21/3.15 8.70/8.75 10.37/10.01
47.57/47.30 3.99/3.57 10.36/11.03 11.46/12.63 12.86/12.87
7.65/7.96 9.10/9.10
146.5–147
119–119.5
>380
C15H10F2N2O2S
C20H18N4O4S2Zn
II
C30H18F4N4O4S2Zn 52.00/51.19 3.32/2.58
308–309
0.01 mol) in methanol (6 ml)) was added at room tem- dination bond with the zinc atom, which is confirmed
perature to a suspension of ligand L1 (2.22 g, 0.01 mol)
by the fact that the IR spectra of the complexes contain
in anhydrous methanol (25 ml). A precipitate of ligand
no absorption bands caused by the ν(N–H) vibrations.
L1 sodium salt was formed. The mixture was stirred for
The IR spectra of the ligands and complexes
(Table 2) also exhibit absorption bands assigned to
30 min, a solution of anhydrous zinc chloride (0.68 g,
0.005 mol) in anhydrous methanol (5 ml) was added
dropwise, and the resulting mixture was stirred for 2 h vibrations of the quinoline rings at 1600 and 1500 cm−1
on heating to 50–55°ë. After cooling, a white precipi-
tate was filtered off, washed successively with water
and methanol, and dried in vacuo over P2O5. The yield
of compound I was 2.41 g (95.1%). The substance was
recrystallized from tetrahydrofuran. The product does
not melt up to 380°ë.
characteristic of 8-hydroxyquinoline and its complexes
with zinc and aluminum [9–13]. In addition, the bands
characteristic of vibrations of the sulfo group at 1300–
1400 and 1120–1190 cm–1 are observed [14–16].
The electronic absorption and photoluminescence
spectra of the synthesized compounds in the visible
spectral range are presented in the figure. The elec-
tronic absorption spectra of the ligands exhibit maxima
Synthesis of zinc bis[8-(3,5-difluorophenylsulfa-
nylamino)quinolinate] (II). Ligand L2 (1.92 g,
0.06 mol) was suspended in anhydrous methanol
(25 ml), and a solution of sodium methoxide (prepared at 242, 312 nm (L1)) and 237, 283, 300, 320 nm (L2). In
by the dissolution of sodium (0.14 g, 0.06 mol) in meth-
anol (6 ml)) was added at room temperature. The result-
ing mixture was stirred for 30 min on heating to 35–
40°ë, and a solution of anhydrous zinc chloride
(0.41 g, 0.003 mol) in methanol (10 ml) was added
dropwise. A white precipitate was formed. The solution
with the precipitate was stirred for 1 h at 35–40°ë,
cooled to room temperature, and the precipitate was fil-
tered off, washed with water and methanol, and dried.
The yield of compound II was 2.01 g (95%). The prod-
uct was recrystallized from tetrahydrofuran.
the electronic absorption spectra of the complexes, the
maxima are observed at 242, 265, 382 nm (I) and 265,
370 nm (II), and the longest-wavelength absorption
band shifts substantially compared to that in the spectra
of the corresponding ligands (from 320 to ~380 nm).
The powders of complexes I and II possess intense
photoluminescence with a maximum at 500 nm (I) and
465 nm (II). No appreciable photoluminescence was
observed for ligands L1 and L2. The photoluminescence
quantum yield of the powders of complexes I and II is
20 and 90%, respectively, which is comparable with or
exceeds the quantum yield of the widely used electrolu-
minescent material AlQ3, being 32% [7, 17].
The results of elemental analyses for ligands L1 and
L2 and complexes I and II are given in Table 1.
Owing to good luminescence properties, complexes
I and II can be used as emitting materials in electrolu-
minescence devices. As compared to traditionally used
8-hydroxyquinoline derivatives [2–5], they have sev-
eral advantages: bulky substituents at the nitrogen atom
should prevent the fast crystallization of the metal com-
plexes during the operation of a device and also can
shield the approach of a water molecule to the nitro-
gen–metal bond, thus impeding the hydrolysis of the
metal complex. All these factors retard degradation
properties and enhance the time source of the electrolu-
RESULTS AND DISCUSSION
The structures of compounds L1, L2, I, and II were
determined by elemental analysis and 1H NMR, mass,
and IR spectroscopy (Table 2). The mass spectra of
ligands L1 and L2 exhibit lines corresponding to their
molecular mass (222 and 320, respectively). Ligands L1
and L2 contain the N–H bond with the corresponding
signals at 9.39 (L1) and 10.5 (L2) in the 1H NMR spectra.
The IR spectra of the ligands exhibit the absorption
bands corresponding to the ν(N–H) vibrations at 3295
(L1) and 3265 cm–1 (L2). In complexes I and II, the
nitrogen atom of the sulfanylamino group forms a coor- minescence devices [2, 3].
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 35 No. 4 2009
Yakushchenko
