Inorganic Chemistry Communications 64 (2016) 13–15
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Inorganic Chemistry Communications
Short communication
A tris-diketonate-Eu(III) complex with the brominated 2,2′-bpy ancillary
ligand doped in PMMA for high color-purity red luminescence
a
a
a
a
a,
b
c
Yani He , Lin Liu , Zhao Zhang , Guorui Fu , Xingqiang Lü ⁎, Wai-Kwok Wong , Richard A. Jones
a
School of Chemical Engineering, Shaanxi Key Laboratory of Degradable Medical Material, Northwest University, Xi'an 710069, Shaanxi, China
Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Kowloon Tong, Hong Kong, China
Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165, United States
b
c
a r t i c l e i n f o
a b s t r a c t
Through the physical doping of a new red-emitting (Ф = 34.9%) tris-β-diketonate Eu3+-complex
[
5
L
Article history:
Received 21 October 2015
Received in revised form 8 December 2015
Accepted 12 December 2015
Available online 14 December 2015
Eu
Eu(DBM)
-Br-2,2′-bpy (5-bromo-2-(pyridin-2-yl)pyridine) in PMMA (poly(methyl methacrylate), the obtained
hybrid material 1@PMMA exhibits significantly improved physical properties including the enhanced
3
(5-Br-2,2′-bpy)] (1; DBM = dibenzoylmethane) with the brominated 2,2′-bpy ancillary ligand
3
+
L
Eu -based color-purity red luminescence (ФEu = 53.7%).
©
2015 Elsevier B.V. All rights reserved.
Keywords:
Tris-β-diketonate Eu3+-complex
Heavy-atom effect
PMMA-supported doping material
High color-purity red luminescence
Although β-diketonate-type ligands, as one of the most popular
chromophores for obtaining neutral tris-β-diketonate Eu -complexes,
polymer-supported and purely red-luminescence hybrid materials is
worth exploring.
3
+
are widely realized to effectively sensitize the high color-purity red
As a matter of fact, heavy-atom effect of organic ligands, as one of the
good approaches to the enhanced photophysical property [12], contrib-
utes to more efficient energy transfer with the strengthened optical
absorption and inter-system crossing besides a higher stability of the re-
lated complexes. Herein, based on a new ancillary ligand 5-Br-2,2′-bpy,
3
+
emissions of Eu
ion with the potential applications in OLEDs [1],
color-tuning pigments [2] or fluoro-immunoassays [3], aspiring to
their excellent performances, such as large quantum yield, high thermal
stability and good film-forming property, is still in demand [4]. In
this context, within the reported series of β-diketonate derivatives,
DBM (dibenzoylmethane) is proved to be a more suitable one because
3
the obtained tris-β-diketonate complex [Eu(DBM) (5-Br-2,2′-bpy)] (1)
endowing higher efficiency red-light luminescence is expected, and
PMMA-supported high color-purity red-luminescence hybrid material
by doping is also anticipated.
The N,N-chelate ancillary precursor 5-Br-2,2′-bpy was synthesized
by the Stille coupling reaction from 2,5-dibromopyridine and 2-
3
of its strong optical absorption and the compatibility of its π–π*
−
1
(
(
20,700 cm ) energy level with the first excited state level
−
1
5
3+
17,286 cm , D
0
) of Eu
ion [5]. However, in contrast to the low
L
quantum yields (ΦEu = 0.10–0.47%) from the use of large conjugation
DBM derivatives [6], the introduction of the N,N-chelate [7], PO-linked
(tributylstannyl)pyridine in the presence of Pd(PPh
Scheme 1S, further through the self-assembly of DBM, 5-Br-2,2′-bpy
and LnCl ·6H O (Eu or Gd) in a molar ratio of 3:1:1, two tris-β-
diketonate [Ln(DBM) (5-Br-2,2′-bpy)] complexes (Ln = Eu, 1 or
Ln = Gd, 2) were isolated, respectively. The precursor 5-Br-2,2′-bpy
and its complexes 1–2 were well characterized by EA, FT-IR and ESI-
MS (in Supporting information), and X-ray quality single crystals were
3 4
) . As shown in
[
8] or O,O-chelate [9] ancillary ligands gave rise to distinctively larger
L
pure red-light quantum yields (ΦEu = 12.7–45.6%) due to effective de-
crease of oscillator-induced luminescent quenching [10]. On the other
hand, in view of the obtainment of improved physical properties be-
sides high color-purity red emission, the doping is relatively simple
while more efficient than another alternative approach to grafting
3
2
3
[
11]. Moreover, to the best of our knowledge, the introduction of
3
obtained for complex [Gd(DBM) (5-Br-2,2′-bpy)] (2) as the representa-
heavy-atom on the ancillary ligands to further optimize the pure red-
light emission of the obtained DBM-based Eu3 -complexes has not
been concerned, and their physical doping for the formation of
tive of complexes 1–2 with crystallographic data in Tables 1–2S.
Complex 2 crystallizes with two independent mononuclear molecules
in the asymmetrical unit. As shown in Fig. 1, within each mononuclear
unit, three deprotonated DBM ligands with the similar O,O-chelate
mode and one 5-Br-2,2′-bpy ancillary ligand with the N,N-chelate
mode coordinate to one Gd3 ion in a square anti-prismatic pattern,
+
+
⁎
3
+
resulting in the formation of a typical tris-β-diketonate Ln complex
387-7003/© 2015 Elsevier B.V. All rights reserved.
1