Synthesis, crystal structures and spectroscopic properties of copper(I) complexes containing β-dialdiminato supporting ligands

Article abstract of DOI:10.1016/j.ica.2007.06.024

Two mononuclear neutral copper(I) complexes, Cu(L¹)PPh₃ (1), Cu(L²)(PPh₃)₂ (2) ([L¹]^- = [{N(C₆H₃ⁱPr₂-2,6)C(H)}₂CPh]^-

Full text of DOI:10.1016/j.ica.2007.06.024

Available online at www.sciencedirect.com
Inorganica Chimica Acta 362 (2009) 233–237
www.elsevier.com/locate/ica
Note
Synthesis, crystal structures and spectroscopic properties of
copper(I) complexes containing b-dialdiminato supporting ligands
a
b,c,
*
Xiaowei Li a,b,c, Junqiao Ding b,c, Weiqun Jin , Yanxiang Cheng
a
Department of Chemistry, Jilin University, Changchun 130012, PR China
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun 130022, PR China
b
c
Graduate School of the Chinese Academy of Sciences, Beijing 100039, PR China
Received 11 January 2007; received in revised form 4 June 2007; accepted 12 June 2007
Available online 29 June 2007
Dedicated to Professor Michael F. Lappert
Abstract
i
Two mononuclear neutral copper(I) complexes, Cu(L1)PPh3 (1), Cu(L2)(PPh3)2 (2) ([L1]À = [{N(C6H3 Pr2-2,6)C(H)}2CPh]À;
[L2]À = [{N(C6H5)C(H)}2CPh]À) have been synthesized and structurally characterized by X-ray crystallography. In complex 1, the
copper(I) atom is in a distorted three-coordinate trigonal planar environment, whereas in complex 2 with the less sterically hindered
b-dialdiminato ligand, the copper(I) atom is the centre of a four-coordinate distorted tetrahedron. At room temperature complexes 1
and 2 in a film of PMMA exhibit green emission at 543 and 549 nm with lifetimes of 5.28 and 5.32 ns, respectively.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Copper(I) complexes; Crystal structures; b-Dialdiminatoes; Triphenylphosphine; Photoluminescence
1. Introduction
b-Diketiminates are widely used as chelating ligands in
coordination chemistry due to their strong binding ability
to metals, and readily tunable steric and electronic
properties by means of changing the substituents [15].
Many of their Cu(I) complexes have been prepared and
studied mainly as models for active sites of metalloen-
zymes [16–18], but less attention has focused on photolu-
minescence (PL). b-Dialdiminato ligands in monoanionic
form are generally p-delocalized conjugated systems with
the conjugation often extending to the aromatic substitu-
ent in c–position and of the ligand to chelating N atoms
as in a phenanthroline ligand [19,20]. These facts afford
the possibility to synthesize neutral Cu(I) complexes
exhibiting photoluminescence. In this paper, we present
the syntheses and characterization of two new photolu-
minescent Cu(I) complexes of b-dialdinimine (Chart 1)
and PPh3 ligands.
Luminescent Cu(I) complexes are currently receiving
much attention mainly due to their potential applications
in organic light-emitting diodes (OLEDs) [1–6] and
photochemistry [7–10]. Most efforts have focused on the
synthesis and photophysical properties of these complexes
supported by pyridine-type ligands, such as bipyridine
and phenanthroline [11,12]. However, the utilization of
those ligands results in the formation of ionic Cu(I) com-
plexes, which have a long response time in light-emitting
devices with the distribution of counter ions [13,14].
*
Corresponding author. Address: State Key Laboratory of Polymer
Physics and Chemistry, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, PR China. Tel.: +86
431 85262106; fax: +86 431 85684937.
E-mail address: yanxiang@ciac.jl.cn (Y. Cheng).
0020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.06.024

234
X. Li et al. / Inorganica Chimica Acta 362 (2009) 233–237
1
77.5; H, 7.2; N, 3.7%. H NMR (C6D6, 300 MHz, ppm): d
7.83 (s, 2H), 7.27–7.04 (m, 20H), 6.79–6.75 (m, 6H), 3.41
(septet, J = 6.8 Hz, 4H), 1.16 (d, J = 6.8 Hz, 12H), 0.71
(d, J = 6.8 Hz, 12H).
NH
N
2.2.2. Synthesis of Cu(L2)(PPh3)2 (2)
NH
N
Under an N2 atmosphere nBuLi (0.5 ml, 1.6 M) was
added dropwise to a stirred solution of HL2 (150 mg,
0.5 mmol) in 10 ml THF at room temperature. After stir-
ring for 1 h, the above solution was added to a slurry of
[Cu(CH3CN)4][BF4] (160 mg, 0.5 mmol) in 10 ml THF.
After stirring for 4 h, PPh3 (350 mg, 1.3 mmol) was added
to give a yellow-green solution and the mixture was
allowed to stir for 12 h. The solvent was then removed
under reduced pressure to yield a yellow residue which
was extracted into pentane (20 ml)/toluene (40 ml). The
resulting mixture was filtered. The filtrate was stored at
À20 ꢁC overnight to afford orange-red crystals (466 mg,
95%). M.p. 105–106 ꢁC. Anal. Calc. for C64H55CuN2P2:
C, 78.6; H, 5.7; N, 2.9. Found: C, 78.4; H, 5.7; N, 3.0%.
1H NMR (C6D6, 300 MHz, ppm): d 8.21 (s, 2H), 7.45–
7.17 (m, 40H), 7.04–6.92 (m, 10H), 2.40 (s, 3H).
HL1
HL2
Chart 1.
2. Experimental
2.1. Materials and methods
All manipulations were performed under nitrogen using
standard Schlenk techniques. The solvents THF, toluene
and diethyl ether were distilled from Na/benzophenone.
Pentane was distilled from CaH2 under nitrogen. The
Cu(I) starting materials: (PPh3)3CuCl [21] and
[Cu(CH3CN)4]BF4 [22] were prepared according to the lit-
erature procedures. Ligand precursors HL1 and HL2 were
synthesized using the reported procedures [23].
2.3. X-ray crystallography
Intensity data for 1 and 2 were collected at 293(2) K on
NMR data were recorded on a Bruker Avance 300 spec-
trometer (300 MHz) with TMS as internal standard. Ele-
mental analyses (C, H and N) were determined using a
Bio-Rad elemental analysis system. UV–Vis absorption
and emission spectra were recorded on a Perkin–Elmer
Lambda 35 UV–Vis spectrophotometer and a Perkin–
Elmer LS 50B fluorescence spectrophotometer, respec-
tively. Thermal gravimetric analysis (TGA) was carried
out using the Perkin–Elmer-TGA7 instrument under a
a Bruker SMART CCD diffractometer with graphite-
monochromated Mo Ka radiation (k = 0.71073 A). The
˚
structures were solved by direct methods and refined by
full-matrix least-squares refinement based on F2 using
the SHELXL package [24]. The hydrogen atoms were placed
in idealized positions and refined as riding atoms, except
the disordered toluene molecule in complex 2. Further
details of the structural analyses are summarized in Table
1. Selected bond lengths and bond angles are shown in
Table 2.
nitrogen atmosphere at a heating rate of 20 ꢁC minÀ1
.
Emission lifetime measurements were recorded by a system
equipped with a Quanty-Ray DCR-2 pulsed Nd:YAG laser
with a THG 355 nm output and ca. 3 ns pulse width. Melt-
ing points were taken in sealed capillaries and are
uncorrected.
3. Results and discussion
3.1. Syntheses
Complex 1 was obtained by the reaction of (PPh3)3CuCl
and LiL1 in a 1:1 molar ratio under a nitrogen atmosphere.
However, complex 2 was not obtained by this procedure.
Instead, its synthesis was achieved by the reaction of
[Cu(CH3CN)4][BF4], LiL2 and 2 equiv. of PPh3. Both com-
plexes were fully characterized by 1H NMR, elemental
analysis, thermal gravimetric analysis (TGA) and found
to be air-stable in the solid state at room temperature.
TGA data revealed that the two complexes are thermally
stable; their decomposition temperature (Td) was 184 ꢁC
for 1 and 202 ꢁC for 2.1
2.2. Synthesis of complexes
2.2.1. Synthesis of Cu(L1)(PPh3) (1)
Under an N2 atmosphere, nBuLi (0.75 ml, 1.6 M) was
added dropwise to a stirred solution of HL1 (460 mg,
1.0 mmol) in 10 ml THF at room temperature. After stir-
ring for 1 h, the above solution was added to a slurry of
(PPh3)3CuCl (850 mg, 1.0 mmol) in 10 ml THF to give a
light yellow-green solution and the mixture was allowed
to stir for 6 h. The solvent was then removed under reduced
pressure to yield a yellow solid which was extracted into
pentane (10 ml)/diethyl ether (40 ml). The resulting mixture
was filtered and the filtrate was stored at À20 ꢁC to afford
light yellow crystals (508 mg, 64%). M.p. 142–157 ꢁC. Anal.
Calc. for C51H56CuN2P: C, 77.4; H, 7.1; N, 3.5. Found: C,
1
The crystals of complex 2 start to decompose at 103 ꢁC due to the loss
of the solvent toluene molecular.

X. Li et al. / Inorganica Chimica Acta 362 (2009) 233–237
235
Table 1
Crystallographic data for complexes 1 and 2
Complex
1
2
Empirical formula
Molecular weight
Crystal system
Space group
C51H56CuN2P
791.49
Monoclinic
P21/c
C64H55CuN2P2
977.58
Monoclinic
C2/c
˚
a (A)
21.5472(9)
11.4189(5)
17.8966(8)
101.5640(10)
4314.0(3)
4
24.216(3)
14.0411(17)
17.525(2)
117.743(2)
5273.7(11)
4
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
Dcalc (g/cm3)
1.219
1.128
F(000)
1680
0.580
1876
0.511
Absorption coefficient (mmÀ1
)
h range (ꢁ)
Crystal size (mm)
Reflections collected
1.93–26.03
0.21 · 0.17 · 0.11 0.21 · 0.18 · 0.11
23916
1.73–26.03
15037
Fig. 1. Molecular structure of complex 1 with hydrogen atoms omitted for
clarity.
Independent reflections (Rint
Goodness-of-fit on F2
)
8465(0.0557)
1.016
5195(0.0777)
1.020
Final R indices [I > 2r(I)], R1,
wR2
0.0546, 0.1144
0.0546, 0.1041
R indices (all data) R1, wR2
0.0885, 0.1303
0.1017, 0.1131
Table 2
Selected bond lengths (A) and angles (ꢁ) for complexes 1 and 2
˚
Complex 1
Complex 2
Cu–N1
Cu–N2
Cu–P
1.954(2)
1.956(2)
2.1645(8)
1.319(4)
1.399(4)
1.405(4)
1.313(3)
1.497(4)
1.432(4)
1.442(4)
1.825(3)
1.830(3)
1.824(3)
Cu–N
Cu–P
2.053(3)
2.2917(10)
1.320(4)
1.403(4)
1.484(6)
1.421(4)
1.823(4)
1.831(4)
1.836(3)
C1–N
C1–C2
C2–C3
C7–N
P–C13
P–C19
P–C25
C1–N1
C1–C2
C2–C3
C3–N2
C2–C4
N1–C10
N2–C22
P–C34
P–C40
P–C46
N1–Cu–N2
N1–Cu–P
N2–Cu–P
96.16(10)
132.50(8)
130.97(7)
N–Cu–N0A
N–Cu–P
N–Cu–P0A
P–Cu–P0A
93.13(15)
106.85(8)
113.90(8)
119.27(5)
Fig. 2. Molecular structure of complex 2 with hydrogen atoms and the
solvent toluene molecular omitted for clarity.
Symmetry transformations to generate equivalents atoms for 2: 0A Àx, y,
Àz + 3/2.
˚
and Cu–P [2.1645(8) A] in 1 are much closer to those in
Me2Lipr,SMeCu(PPh3) [Cu–N 1.956(3) and 1.950(3); Cu–P
2.1687(11) A] and shorter than those in Me2Lipr2Cu(PPh3)
˚
3.2. Crystal structures
˚
˚
[Cu–N 1.9683(19) and 1.975(2) A; Cu–P 2.1813(7) A].
Interestingly, the Cu(I) atom in complex 2 exhibits a dis-
torted tetrahedral coordination geometry, being bonded
to the two N atoms from L2 and two P atoms from the
two triphenylphosphine ligands. The bond lengths Cu–N
The molecular structures of complexes 1 and 2 were
determined by X-ray crystallography and are shown in
Figs. 1 and 2, respectively. The Cu(I) atom in complex 1
is coordinated by two N-donor atoms from the bidentate
ligand L1 and the P atom from PPh3 to form a three-coor-
dinate environment, which is similar to that found in
˚
and Cu–P are 2.053(3) and 2.2917(10) A, respectively,
which are longer than those in complex 1 due to the more
crowded coordination environment around Cu(I) in 2.
The mean deviations of the CuNCCCN six-membered-
ring plane [19] are 0.0469 A in complex 1 and 0.0124 A in
2. The torsion angles are 74.8ꢁ [C1, N1, C10 and C11],
Me2Lipr2Cu(PPh3) (Me2Lipr2 = [{N(C6H3 Pr2-2,6)C(CH3)}2-
i
C(H)]) [25] and Me2Lipr,SMeCu(PPh3)(Me2Lipr,SMe
[N(C6H3 Pr2-2,6) C(CH3)C(H)C(CH3)N (C6H3 Pr2-2)(SMe-6)])
=
i
i
˚
˚
˚
[18]. The bond distances Cu–N [1.954(2) and 1.956(2) A]

236
X. Li et al. / Inorganica Chimica Acta 362 (2009) 233–237
4. Conclusion
Two neutral luminescent copper(I) complexes were syn-
thesized by using b-dialdiminato ligands, which exhibit
green emission in the solid state at room temperature. They
are air and thermally stable and might be used as emitter in
light-emitting devices.
5. Supplementary material
CCDC 629129 and 6219130 contain the supplementary
crystallographic data for 1 and 2. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
300
400
500
600
700
Wavelength / nm
Fig. 3. Absorption and emission spectra of complexes Cu(L1)PPh3 (1,
solid line) and Cu(L2)(PPh3)2 (2, dashed line) in THF at room
temperature.
Acknowledgements
90.5ꢁ [C3, N2, C22 and C23] in 1 and 43.7ꢁ [C1, N, C7 and
C8] in 2, respectively, which indicate that complex 2 is
more strongly conjugated than complex 1, although the
torsion angles are 37.0ꢁ [C1, C2, C4 and C5] in 1 and
39.4ꢁ [C1, C2, C3 and C4] in 2, respectively.
We gratefully acknowledge supports from the National
Natural Science Foundation of China (No. 20474062)
and ‘‘973’’ project (No. 2002CB613401) of the Ministry
of Science and Technology of China.
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