C. Yang et al. / Dyes and Pigments 92 (2011) 696e704
697
In this paper, to further improve the luminescent properties of
europium complexes, four novel trinuclear europium complexes
based on two tris-b-diketones ligands were designed and synthe-
sized. The structures of the ligands and trinuclear europium
complexes were characterized by FT-IR, UVevis, 1H NMR, 13C NMR,
ESI-MS, element analysis. The photoluminescent properties and
thermal stability were investigated by photoluminescent (PL)
spectroscopy and thermogravimetric analysis (TGA), respectively.
anhydrous Na2SO4. The volume was reduced to approximately
50 ml and then light petroleum (100 ml) was added. The solution
was placed in freezer and the resulting oily solid was filtered off.
This progress was repeated several times and the crops of oily solid
were combined. The product was then recrystallized from light
petroleum to yield 1,3,5-tris(bromomethyl)benzene as colorless
needles, yield 40% (1.5 g), mp 87e89 ꢀC 1H NMR (400 MHz, CDCl3):
d
4.44 (s, 6H, eCH2Br), 7.34(s, 3H, ArH). Anal. Calcd. for C9H9Br3: C,
For all trinuclear europium complexes, every tris-
b-diketones
30.29; H, 2.54; Found: C, 30.51; H, 2.37.
ligand contains three -diketones, and can coordinate with three
b
europium ions. We expect that these trinuclear complexes can
exhibit excellent luminescent properties.
2.4. General procedure of synthesis of tris-b-diketones
Tris-b-diketones were synthesized according to that discussed
2. Experimental section
in reference [21]. Dibenzoylmethane (30 mmol) was added to
a refluxing solution of tert-butanol (250 ml) and potassium tert-
butoxide (20 mmol). 10 mmol of 1,3,5-tris (bromomethyl)-2,4,6-
trimethylbenzene or 1,3,5-tris(bromomethanyl)benzene was then
added in some portions followed by a catalytic amount of potas-
sium iodide. The mixture solution was kept at reflux temperature
for 48 h, then tert-butanol was removed under reduced pressure,
the residue product was separated by dichloromethane (150 ml)
and water (100 ml), organic phase was dried over anhydrous
sodium sulfate. Some pale-yellow oil was given when dichloro-
methane was removed in vacuum, the oil was solidified for two
days to get pale-yellow solid. This was recrystallized from ethyl
acetate to give colorless crystalline.
2.1. Materials and measurements
Starting materials were of reagent grade and used without further
purification, unless otherwise stated. All solvents were purified with
conventional methods before used. Mesitylene, Dibenzoylmethane
(DBM), potassium tert-butoxide, 2-thenoyltrifluoroacetone (TTA), and
phenanthroline were purchased from Aldrich Chemical Company.
Eu2O3 (99.99%) was purchased from a Chinese company, Beijing
Founder. EuCl3.6H2O ethanol solution was obtained by dissolving
Eu2O3 in concentrated chlorhydric acid.
Melting points were determined on SGW X-4 micro-melting
point apparatus (Shanghai PSE Co. Ltd). Elemental analysis data
were obtained from Vario EL elemental analyzer. NMR spectra were
taken on a DRX-400 MHz (Bruker) superconducting-magnet NMR
spectrometer with TMS as an internal standard. FT-IR spectra were
carried out using an RFX-65A (Analects) Fourier Transform Infrared
Spectrometer. Thermogravimetric analysis (TGA) was performed
with Pyris 1 TGA instrument at a heating rate of 10 ꢀC/min under
nitrogen atmosphere. UVevis absorption spectrum was deter-
mined on a Shimadz spectrophotometer. The photoluminescence
(PL) measurements in solid state and THF solution were conducted
in a Hitachi F-4600 florescence spectrophotometer. Luminescence
lifetimes were obtained with the PLSP20 steady state spectrometer
with a pulsed xenon lamp. X-ray diffraction (XRD) measurements
were carried out with a Rigaku Diffractometer (D/MAX-12000).
1,3,5-Tris(30-methyl-20, 40-pentanedione)-2,4,6-trimethylbenzene
(H3L1) was synthesized in a yield 72%(5.9 g), mp 207e209 ꢀC 1H
NMR (400 MHz, CDCl3):
COCHCO), 3.40(6H, d, CH2), 1.90(9H, s, CH3). 13C NMR (100 MHz,
CDCl3): 17.2(CH3), 30.2(CH2), 58.2(CH), 128.6(CH), 128.7 (C),
133.5(CH),133.8(CH), 134.9(C), 135.9(C), 196.2(C]O). (Found: C,82.49;
d 7.24e7.69 (30H, m, Ph), 5.01(3H, t,
d
H, 5.96; C57H48O6 requires C, 82.57; H, 5.84) FT-IR(KBr): n (C]O) 1693,
1660 cmꢁ1. ESI-MS(m/z): 851(M þ Na)þ.
1,3,5-Tris(2,2-dibenzoylethyl) benzene (H3L2) was prepared in
a yield 65%(5.1 g), mp 87e89 ꢀC 1H NMR (400 MHz, CDCl3):
d 16.88
(s, 3H, eOH) 7.97e7.99 (d, 12H, Ph) 7.52e7.56 (t, 6H, Ph) 7.46e7.50
(t, 12H, Ph), 6.85 (s, 3H, Ph), 3.41 (s, 6H, eCH2). 13C NMR(100 MHz,
CDCl3):
d 34.8(CH2), 58.5(CH), 128.5(CH), 128.8(CH), 133.5(CH),
135.8(C.), 139.9(C), 195.4(C]O). (Found: C,81.73; H, 5.87; C54H42O6
requires C, 82.42; H, 5.38) FT-IR(KBr):
n .
(C]O) 1697, 1670 cmꢁ1
2.2. Synthesis of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene
ESI-MS (m/z): 810(M þ Na)þ.
1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene was prepared
according to the procedure described in the literature with some
modification [20]. Mesitylene (12 g, 100 mmol), paraformaldehyde
(10.26 g, 340 mmol) and 75 ml of glacial acetic acid was rapidly added
to a 150 ml three neck round bottom flask with 75 ml of HBr/acetic
acid solution during magic stirring. The mixture solution was heated
to 95 ꢀC and kept at this temperature for 8 h, then poured into 200 ml
of water to give amounts of white solid. The product from filtering
was washed with 200 ml of anhydrous ethanol, and then was filtered
and dried overnight at 60 ꢀC to give 33.5 g of title compound, yield
85%, mp 183e186 ꢀC. FT-IR (KBr) (cmꢁ1): 785, 1446.1, 2922. 1H NMR
2.5. General procedure of synthesis of trinuclear Eu-complexes
Ligand H3L1 or H3L2 (0.5 mmol), Phen.H2O( 1.5 mmol) and 0.2 g
potassium tert-butoxide were dissolved in 50 ml anhydrous
ethanol, then the solution was heated to 60 ꢀC, 20 ml anhydrous
ethanol with EuCl3.6H2O (1.5 mmol) was gradually added to the
solution. After 1 h, corresponding b-diketone (3 mmol) was added
to the mixed solution and reacted at this temperature for another
10 h, mixed solution was cooled to room temperature and removed
solvents, residual solid was dissolved by 50 ml chloroform, and
washed three times with 80 ml water every time, then removed
chloroform through reduced pressure to give the desired trinuclear
europium complexes.
(400 MHz, CDCl3):
d
2.44 (s, 9H, AreCH3), 4.56(s, 6H,eCH2Br). 13C
12.1, 27.5, 134.7, 137.1.
NMR (100 MHz, CDCl3):
d
Eu3(DBM)3(phen)33H2OL1 was prepared in a yield 70% as
2.3. Synthesis of 1,3,5-tris(bromomethanyl)benzene
light-yellow powder. 1H NMR (400 MHz, CDCl3):
d, ppm 10.96(br
s, PheneH), 10.58(br s, PheneH), 9.94(br s, PheH), 8.93(br s, PheH),
7.98e8.13(br d, PheH), 7.24e7.48(br d, PheH), 6.49e6.70(br d,
PheH), 5.84(br s, PheH), 4.71(br s, COCHCO), 3.13(br s, eCH2),
2.72(br s, H2O), 2.32(br s, eCH3). (Found: C, 63.92; H, 4.15; N, 3.01.
Eu3C138H114N6O18 requires C, 63.74; H, 4.42; N, 3.23) FT-IR(KBr):
Mesitylene (10.12 g, 84 mmol), NBS (45.30 g, 255 mmol) and
AIBN (45.9 mg) were heated to reflux at 90 ꢀC in 120 ml of dry CCl4
under N2 with stirring for 40 h. The solution was then cooled in an
ice bath and the succinimide was filtered off and washed with
carbon tetrachloride. The filtrate was washed by saturated sodium
hydrogen carbonate solution and water, and then dried with
n
(C]O) 1596, 1551 cmꢁ1, (C]C)1518 cmꢁ1, (Eu/O) 515 cmꢁ1
,
(Eu/N) 422 cmꢁ1
.