A series of Cu1 complexes containing 1,10-phenanthroline derivative ligands: Synthesis, characterization, photophysical, and oxygen-sensing properties

Article abstract of DOI:10.1002/ejic.200900123

Five novel copper(I) complexes with the general formula [Cu(dpephos)(NN)]BF₄ {dpephos = bis[2-(diphenylphos- phanyl)phenyl] ether, NN = 2-phenyl-1H-imidazo[4,5-/]- [1,10]phenanthroline (pip, 1), 1-ethyl-2-phenyl-1H-imid- azo[4,5-/][1,10]phenant

Full text of DOI:10.1002/ejic.200900123

FULL PAPER
DOI: 10.1002/ejic.200900123
A Series of CuI Complexes Containing 1,10-Phenanthroline Derivative Ligands:
Synthesis, Characterization, Photophysical, and Oxygen-Sensing Properties
Linfang Shi[a,b] and Bin Li*[a]
Keywords: Luminescence / Copper / N ligands / Sensors
Five novel copper(I) complexes with the general formula
[Cu(dpephos)(NN)]BF4 {dpephos bis[2-(diphenylphos-
phanyl)phenyl] ether, NN 2-phenyl-1H-imidazo[4,5-f]-
[1,10]phenanthroline (pip, 1), 1-ethyl-2-phenyl-1H-imid-
azo[4,5-f][1,10]phenanthroline (epip, 2), 2-(naphthalen-1-yl)-
1H-imidazo[4,5-f][1,10]phenanthroline (nip, 3), 1-ethyl-2-
(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (enip,
using a combination of cyclic voltammetry and electronic ab-
sorption spectroscopy. It was found that 1–4 display broad-
band emission in the solid state upon excitation at λ =
400 nm, and the emission maxima are located in the range
530–558 nm; the excited-state lifetimes of these complexes
are 8.24, 1.97, 6.99, and 2.43 µs, respectively. As a result, the
emission intensity of complexes 1–4 is sensitive to oxygen
=
=
4), 2-(anthracen-9-yl)-1-ethyl-1H-imidazo[4,5-f][1,10]phen- concentration, and they display oxygen-sensing properties
anthroline (aeip, 5)} were rationally designed and synthe-
sized, and these complexes were characterized by 1H NMR
and IR spectroscopy and elemental analysis. X-ray crystal-
after they are encapsulated into mesoporous silica MCM-41
or SBA-15.
structure analysis of 3 and 4 are also presented. Their photo- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
physical properties at room temperature were examined by
Germany, 2009)
tested as oxygen-sensing probes and some of them dis-
played excellent performance.[3] However, few reports on
the application of copper complexes in oxygen sensing have
been published so far.[4]
Introduction
The photophysics of luminescent copper(I) complexes
has been the object of intensive investigation for the past
decades. Thanks to the pioneering work, the mechanism of
emission and quenching of luminescent copper(I) com-
plexes has been studied systematically.[1] In comparison to
some transition-metal complexes, copper(I)-based ones are
less toxic, inexpensive, and less environmentally hazardous.
These advantages make their practical application possible.
Recently, much effort has been devoted to the exploration
of the applications of copper(I) complexes in solar energy
conversion, biological probing, and organic light-emitting
devices (OLEDs).[2] Luminescence-based oxygen sensing is
another important application for luminescent metal com-
plexes, because the determination of the concentration of
oxygen in gaseous and aqueous samples and in biological
fluids has great significance. Oxygen is a powerful quencher
of the emission intensity and excited-state lifetime of some
luminescent complexes. Several metal complexes have been
In order to examine the possibility of practical applica-
tion of complexes based on this inexpensive metal in oxygen
sensing, we synthesized a series of copper(I) complexes ab-
breviated as [Cu(dpephos)(NN)]BF4 {dpephos = bis[2-(di-
phenylphosphanyl)phenyl] ether, NN = 2-phenyl-1H-imid-
azo[4,5-f][1,10]phenanthroline (pip, 1), 1-ethyl-2-phenyl-
1H-imidazo[4,5-f][1,10]phenanthroline (epip, 2), 2-(naph-
thalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (nip, 3),
1-ethyl-2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenan-
throline (enip, 4), 2-(anthracen-9-yl)-1-ethyl-1H-imidazo-
[4,5-f][1,10]phenanthroline (aeip, 5)} and studied their pho-
tophysical and oxygen-sensing properties. For practical ap-
plications in optical oxygen-sensing devices, it is necessary
to incorporate the dye molecules into a solid matrix that
can act as a medium for supporting the dye molecules and
for oxygen transportation from the environment. There are
many reports on luminescence-based oxygen sensors utiliz-
ing different matrixes,[3f,5] from which can be concluded
that the support does indeed have quite stringent criteria
for suitable performance. Additionally, for a suitable matrix,
it must lend itself to convenient attachment to the sensor
probe. Mesoporous silica particles are able to physically en-
capsulate and immobilize the probe molecules in the pores;
furthermore, the existence of channels in these materials al-
lows the transportation of small molecules including molec-
[a] Key Laboratory of Excited State Processes, Changchun Insti-
tute of Optics, Fine Mechanics and Physics, Chinese Academy
of Sciences,
Changchun 130033, P. R. China
Fax: +86-431-84627031
E-mail: lib020@yahoo.cn
[b] Graduate School of the Chinese Academy of Sciences, Chinese
Academy of Sciences,
Beijing 100039, P. R. China
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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Eur. J. Inorg. Chem. 2009, 2294–2302

CuI Complexes with 1,10-Phenanthroline Derivative Ligands
ular oxygen into the mesoporous materials. So, the lumines- cated at 1433Ϯ3 cm–1 is a characteristic vibration of P–
cence of probe molecules incorporated into mesoporous sil- Ar. The presence of aryl groups in the ligands and 1–5 is
ica could be quenched readily by oxygen molecules sur- confirmed by the absorptions at 737–747 and
rounding it.
3053Ϯ4 cm–1, which should be attributed to the out-of-
In light of the reasons mentioned above, we choose plane deformation of C–H and the stretching vibration of
mesoporous silica mobil catalytic material 41(MCM-41) =C–H, respectively. The absorption located at 1562 cm–1 in
and Santa Barbara amorphous 15 (SBA-15) as matrix, be- the NN ligands is characteristic of C=C vibrations, and as
cause they possess high surface area and periodic nanoscale for complexes 1–5, this kind of vibration is in the region
pores that will facilitate the adsorption and desorption of 1564–1579 cm–1. The IR spectra of the five complexes to-
oxygen. We have conventionally encapsulated this series of gether with those of the NN ligands also include the char-
copper(I) complexes into the well-studied mesoporous silica acteristic absorption of C=N stretching vibrations located
MCM-41 and SBA-15 by a physical incorporation tech- in the region 1595–1627 cm–1. The presence of the [BF4]–
nique and tested their oxygen-sensing properties. The re- anion was found in the IR spectra with the ν(B–F) mode
sults of the experiments indicate that complexes 1–4 possess at 1074, 1055, 1070, 1058, and 1054 cm–1 for complexes 1–
oxygen-sensing properties after incorporation into such a 5, respectively.[6a] Scheme 1 depicts the molecular structures
matrix.
of this series of complexes.
For further confirmation of the structure of the com-
plexes, single crystals of 3·6C2H5OH and 4·2C2H5OH were
selected for X-ray diffraction analysis. The former crystal
was measured at 273 K and the latter was measured at
Results and Discussion
Synthesis and Characterization
The NN ligands and the corresponding copper(I) com-
plexes were prepared according to a reported method with
some modification.[6] Both the ligands and the complexes
1
were characterized by H NMR and IR spectroscopy and
elemental analysis. The aromatic protons of dpephos in
[Cu(dpephos)(NN)]BF4 appear as complex sets of mul-
tiplets (some overlapping) in the region δ = 7.324 to
6.285 ppm. The existence of dpephos can be further con-
firmed by IR spectroscopy: 1265, 1263, 1263, 1261,
1261 cm–1 for 1–5, respectively, which should be attributed
to the stretching vibration of Ar–O–Ar. The absorption lo-
Figure 1. ORTEP drawing of crystals of (a) 3·6C2H5OH and (b)
4·2C2H5OH with displacement ellipsoids at the 30% probability
level. Hydrogen atoms are omitted for clarity.
Scheme 1. Molecular structures of 1–5.
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L. Shi, B. Li
FULL PAPER
153 K. Being exposed to air at room temperature for 5 h, weight lost for 4 and 5 is ca. 312 and ca. 249 °C, respec-
they lost solvent molecules and the framework of the single tively, and the temperatures of complete loss of the diphenyl
crystals was broken down.
ether and other phenyl groups of dpephos for 4 and 5 are
Single-crystal X-ray structure determinations of ca. 413 and ca. 412 °C, respectively. At temperature higher
3·6C2H5OH and 4·2C2H5OH show that the copper(I) ion is than 500 °C, all five compounds began to dramatically dis-
in a N2P2 distorted tetrahedral environment in which the sociate. When the temperature reached ca. 600 °C, the com-
dpephos ligand was bound through its pair of P donor pounds totally decomposed and only CuBF4 remained.
atoms and the phenanthroline derivative through two di-
imine N atoms. Crystal data and refinement details for
3·6C2H5OH and 4·2C2H5OH are presented in Table S1
(Supporting Information). The ORTEP representations of
these structures are shown in Figure 1, whereas selected
bond lengths and bond angles are given in Table 1. It is
clearly seen from the data summarized in Table 1 that the
Cu–N bond lengths are almost identical in the two com-
plexes, as are those of Cu–P. The Cu–N and Cu–P distances
are within the normal range.[1e,1f,6a] The distortion presum-
ably arises from the restricted bite angle of the NN ligand
N(1)–Cu(1)–N(2) 80.84(11)° for 3·6C2H5OH and 80.48(18)°
for 4·2C2H5OH, whereas the corresponding diphosphane
bite angle P(1)–Cu(1)–P(2) is 113.67(4)° for 3·6C2H5OH
and 118.05(6)° for 4·2C2H5OH. The dihedral angle between
the Cu–N(1)–N(2) and Cu–P(1)–P(2) planes is 87.28° for
3·6C2H5OH and 89.62° for 4·2C2H5OH, which indicates
Figure 2. TGA curves of 1–5.
that the two planes are almost perpendicular.
Photophysical Properties
Table 1. Selected bond lengths [Å] and angles [°] for complexes
3·6C2H5OH and 4·2C2H5OH.[a]
As shown in Figure S1 (Supporting Information), the ab-
3·6C2H5OH
4·2C2H5OH
sorption spectra of 1–5 recorded in CH2Cl2 exhibit intense
π–π* ligand-centered bands in the region 220–350 nm and
weak and broad metal-to-ligand charge-transfer (MLCT)
bands with an onset at 450, 470, 460, 460, and 490 nm for
1–5, respectively. The absorption maxima in the visible re-
gion for 1–4 are 413, 407, 408, and 407 nm, respectively,
whereas complex 5 exhibits no absorption maximum in this
region. Their molar absorption coefficients are compiled in
Table 2.
In air-equilibrated CH2Cl2 solutions, all five complexes
exhibit no luminescence, which is similar to that of [Cu-
(dpephos)(1,10-phenanthroline)]BF4.[6a] In the solid state,
1–4 exhibit luminescence from the MLCT excited states.
For comparison purposes, the emission spectra of the five
complexes in the solid state at room temperature are pre-
sented in Figure 3 and the solid-state photoluminescence
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–P(1)
Cu(1)–P(2)
2.058(3)
2.070(3)
Cu(1)–N(1)
Cu(1)–N(2)
2.2697(10) Cu(1)–P(1)
2.2273(10) Cu(1)–P(2)
2.074(4)
2.036(5)
2.2259(16)
2.2539(17)
80.48(18)
122.57(15)
109.14(13)
113.11(14)
104.45(14)
118.05(6)
N(1)–Cu(1)–N(2) 80.84(11)
N(1)–Cu(1)–N(2)
N(2)–Cu(1)–P(1)
N(1)–Cu(1)–P(1)
N(2)–Cu(1)–P(2)
N(1)–Cu(1)–P(2)
P(1)–Cu(1)–P(2)
N(1)–Cu(1)–P(2)
N(2)–Cu(1)–P(2)
N(1)–Cu(1)–P(1)
N(2)–Cu(1)–P(1)
P(2)–Cu(1)–P(1)
124.87(9)
116.11(8)
108.14(8)
108.39(8)
113.67(4)
[a] Numbers in parentheses are estimated standard deviations in
the least significant digits.
Thermal Stability
Thermogravimetric analysis (TGA) was performed on quantum yield of 1–4 are compiled in Table 2. Upon exci-
the powder samples of 1–5 under a nitrogen atmosphere to tation at λ = 400 nm, powders of 1–4 show broad band
investigate their stable characteristics, and the TGA traces emission at λmax = 530, 558, 543, and 548 nm, respectively,
of the five complexes are presented in Figure 2. Complex 1 whereas the emission intensity is strikingly different: 1ϾϾ4
began to lose weight when it was heated to 222 °C, which Ͼ 3 ≈ 2. The emission of 5 is extremely weak relative to
should be attributed to the loss of the diphenyl ether moiety that of 1–4. As a result, we have not obtained its solid-state
of dpephos. The thermal characteristics of 2 are similar to photoluminescence lifetime decay and quantum yield data.
those of 1: it began to decompose gradually at 231 °C and As shown in Figure S2 (Supporting Information), the pho-
totally lost the diphenyl ether group at 391 °C. Complex 3 toluminescence spectra of 1–4 are composed of two ex-
began to decompose at ca. 260 °C, and when it was heated ponential decays, and the values are in the order of micro-
to 410 °C, diphenyl ether and the other four phenyl groups seconds. The average excited-state lifetimes (τ) of 1–4 are
of the dpephos ligand were completely lost. As can be seen presented in Table 2.
from their TGA traces, the thermal stability of 4 and 5 is
Because all of the emission spectra are recorded under
better than that of 1, 2, and 3. The initial temperature of the same conditions, the differences in the emission spectra
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Eur. J. Inorg. Chem. 2009, 2294–2302

CuI Complexes with 1,10-Phenanthroline Derivative Ligands
Table 2. Photophysical characteristics of 1–5.
bone of pip mainly consists of an imidazo ring, a phenyl
ring, and a phenanthroline ring. As for nip, enip, and aeip,
the substitution group at the 2-position of the imidazo ring
is naphthyl and anthryl, respectively. The imidazo[4,5-f]-
[1,10] phenanthroline moiety of the pip molecule is copla-
nar with the phenyl ring, and as for epip, this moiety is not
coplanar with the phenyl ring as a result of the grating of
the ethyl group to the nitrogen atom on the imidazo ring;[7]
thus, the pip molecule is more flattened than epip. A flat-
tening of the ligand will lead to extended intraligand elec-
tron delocalization and minimized excited-state distortion
of the corresponding complex.[8] This is not only the reason
why 1 exhibits higher emission intensity and energy than 2
does, but also the cause for its exhibiting the strongest emis-
sion and highest emission energy among the five complexes.
The imidazo[4,5-f]1,10-phenanthroline moiety is not copla-
nar with the naphthyl and anthryl ring in nip, enip, or aeip.
The dihedral angles between the imidazo ring and the aryl
group is 40.4, 76.36, and 83.63° for nip, enip, and aeip,
respectively. In particular, the two planes are almost perpen-
dicular in aeip, which results in the worst coplanarity of the
NN ligand, and thus, the weakest emission of 5 among the
series of complexes is not a surprise. As for the difference
in emission intensity between 3 and 4 (i.e., 4 Ͼ 3), it should
be the effect of the ethyl substituent in enip that can pre-
sumably decrease the energy loss coming from N–H vi-
bration.[9]
Complex
λmax,abs [nm][a] [Lmol–1cm–1] λmax,em [nm][b] Φ[c] τ [µs][d]
1
226
281
413
226
270
407
227
262
295
408
226
259
288
407
227
256
286
350
368
389
81100
88520
8450
147820
156110
15020
103780
65910
58100
8870
135740
82010
63820
7180
71590
194540
35050
11280
14760
14880
530
558
0.14
0.02
8.24
1.97
2
3
543
548
0.02
0.04
6.99
2.43
4
5[e]
[a] Measured from dichloromethane with the concentration of
1ϫ10–5 molL–1. [b] Solid-state emission maxima of the complexes.
[c] The photoluminescence quantum yield calculated according to
a literature method.[10] [d] Solid-state excited-state lifetime mea-
sured on powder samples of 1–4. [e] No absorption peak in the
visible region was observed. As a result of its extremely weak emis-
sion, photoluminescence lifetime decay and quantum yield data
have not been obtained.
Cyclic Voltammetry
Cyclic voltammograms of complexes 1, 2, 4, and 5 exhi-
bit irreversible metal-centered oxidation and ligand-based
reduction behavior in CH3CN solution, which are in consis-
tent with phenanthroline-based CuI diimine complexes re-
ported in the literature.[1f,11] The reduction process of 3 ap-
pears reversible, whereas the oxidation process is irrevers-
ible. Their onset oxidation and reduction potential vs. SCE
are summarized in Table 3.
The energy levels of the highest-occupied molecular or-
bital (HOMO) and the lowest-unoccupied molecular orbital
(LUMO) are calculated from the onset oxidation [Eonset(Ox)
and reduction [Eonset(Red)] potentials with the formula
]
Figure 3. Emission spectra of 1–5 in the solid state at room tem-
perature upon excitation at λ = 400 nm.
EHOMO = –4.74 – Eonset(Ox) (–4.74 V for SCE with respect
[12]
to the zero vacuum level) and ELUMO = –4.74 – Eonset(Red)
.
should be attributed to their molecular structure. The five The data of EHOMO, ELUMO, and gaps between the LUMO
complexes contain an identical phosphane ligand (i.e., and HOMO energy levels are presented in Table 3. These
dpephos), and only the structures of the NN ligands are values are in good agreement with those obtained from UV/
different. As presented in Scheme 1, the molecular back- Vis spectroscopy.
Table 3. Electrochemical data for 1–5.
V1/2 [V]
Eonset(Ox) [V]
E1/2 [V]
Eonset(Red) [V]
EHOMO [eV]
ELUMO [eV]
Egel [eV][a]
Egpt [eV][b]
1
2
3
4
5
1.83
1.46
1.77
1.68
1.57
1.56
0.97
1.05
1.59
1.17
1.58
1.58
1.94
1.52
1.56
–1.24
–1.30
–1.39
–1.36
–0.79
–6.30
–5.71
–5.79
–6.33
–5.91
–3.50
–3.44
–3.35
–3.38
–3.95
2.80
2.27
2.44
2.95
1.96
2.76
2.64
2.70
2.70
2.53
[a] Band gaps obtained from electrochemical data. [b] Band gaps obtained from UV/Vis absorption spectrum.
Eur. J. Inorg. Chem. 2009, 2294–2302
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L. Shi, B. Li
FULL PAPER
Oxygen-Sensing Properties
The oxygen-sensing properties of this series of complexes
were tested by physically incorporating them into MCM-41
and SBA-15 (designated as complex/MCM-41 and com-
plex/SBA-15, respectively) with three loading levels of 40,
60, and 80 mgg–1, respectively. The sensitivity properties of
our present samples are discussed on the basis of lumines-
cence intensity quenching.
As can be seen from Figure 4, the powder small-angle
X-ray diffraction (SAXRD) measurements reveal that the
prepared samples (i.e., 1–4/MCM-41 and 1–4/SBA-15) are
structurally mesoporous MCM-41 and SBA-15, respec-
tively.[13] For the MCM-41 systems, the close d100 spacing
values of all of these samples indicate that their framework
hexagonal ordering was preserved after the introduction of
the complexes. Very similar SAXRD results were also ob-
tained in the SBA-15 systems, as shown in Figure 4; all
samples exhibit similar patterns typically observed for SBA-
15. The UV/Vis absorption spectra of the composite sys-
tems show similar profiles to those of pure complexes in
dichloromethane (Figure S3, Supporting Information);
moreover, the composite samples exhibit characteristic
emission of the corresponding complexes. The above-men-
tioned results prove that the copper(I) complexes were as-
sembled within the mesoporous silica. As depicted in the
Stern–Volmer plots of these systems (Figure S4, Supporting
Information), the luminescence of the samples can be effec-
tively quenched by oxygen. Owing to weak luminescence
properties, attempts to test the oxygen-sensing properties of
5 by using the same method as that used for 1–4 failed.
The Stern–Volmer plots are nonlinear within a wide
range of oxygen concentrations. The nonlinearity of these
plots in our present work indicates the presence of hetero-
geneity in the composite system. This phenomenon can be
explained by the fact that the luminophore molecules are
distributed simultaneously between two or more sites within
the silicate support in which one site is more heavily
quenched than the others. As a result, the ideal Stern–
Volmer equation[5d,14] is not suitable for the nonlinear
Stern–Volmer plots, because the different microhetero-
Figure 4. Powder SAXRD spectra of MCM-41 and SBA-15 and
the corresponding 40 mgg–1 loading level systems.
The response time (tȇ) and recovery time (tȆ)[3h] are also
very important parameters in evaluating an oxygen sensor.
Response property tests were carried out on all of the sam-
ples and the values of tȇ and tȆ are displayed in Table 4.
It can be observed that tȇ of the MCM-41 system is slightly
longer than that of the SBA-15 system, whereas tȆ of the
former is significantly shorter than that of the latter. We
think the difference lies in the nature of the support. The
size of the pores in SBA-15 is larger than that in MCM-41;
thus, the adsorption and transportation of oxygen in SBA-
geneous sites exhibit different quenching constant (KSV
)
and unquenched lifetime τ0 values. In the microhetero-
geneous solid-based oxygen sensing systems, Demas “two-
site” model has been proved to have excellent ability to fit
the downward turning of the Stern–Volmer plots.[5d,15,16] If
we change the item “I0/I” in Demas model to “I/I0”, then
the equation takes on the expression given in Equation (1).
Table 4. Values of tȇ, tȆ, and sensitivity (I0/I100).
Loading
level
[mgg–1]
tȇ [s]
tȆ [s]
I0/I100
MCM- SBA- MCM- SBA- MCM-
SBA-
15
41
15
41
15
41
1
2
3
4
40
60
80
5
5
13
3
3
4
84
80
60
181
178
185
5.56
7.27
6.53
6.56
7.44
6.73
40
60
80
6
5
8
3
3
4
34
36
50
135
148
158
2.86
4.40
3.71
2.47
2.50
5.68
(1)
where f0i are the fractional contribution from each oxygen
accessible site and KSVi are the associated Stern–Volmer
quenching constants for each accessible site. The results of
nonlinear fitting are compiled in Table S2 (Supporting In-
formation), from which can be seen that the Demas model
is applicable to our data.
40
60
80
3
3
7
2
3
3
60
66
68
132
113
119
3.72
3.68
4.01
4.82
4.95
5.51
40
60
80
6
6
8
3
3
3
36
20
39
139
125
126
3.78
3.83
5.95
4.95
4.63
5.18
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CuI Complexes with 1,10-Phenanthroline Derivative Ligands
15 should be faster than that in MCM-41, so the quenching and their photophysical properties are strongly affected by
time of the former is shorter than the latter. When the at- the molecular structure of the NN ligands. Particularly, in
mosphere changed from oxygen to nitrogen, it should take view of solid-state emissions at room temperature, the vari-
more time for the SBA-15 system to desorb the larger ation trend can be concluded as follows: the more coplanar
amount of oxygen that was adsorbed in the channels tightly the NN ligand, the stronger the emission and the higher the
(oxygen molecule is notorious for its strong adsorption on emission energy of the corresponding complex. Complexes
silica surface). Consequently, the recovery time of the SBA- 1–4 show oxygen-sensing properties upon incorporation
15 systems is longer than that of the MCM-41 systems. For into mesoporous silica (MCM-41 and SBA-15). It is envi-
both the MCM-41 and SBA-15 systems, the recovery times ronmentally and economically attractive to employ compar-
are longer than the response times. This phenomenon has atively inexpensive and nontoxic metal complexes in oxygen
been rationalized by the above-mentioned fact: the oxygen sensing.
molecule is well known to be adsorbed strongly on silica
surfaces, and thus, the longer recovery time may be attrib-
uted to slow desorption of oxygen from the silica surface in
the support.
Experimental Section
Starting Materials: Bis[2-(diphenylphosphanyl)phenyl] ether
(dpephos), 1,10-phenanthroline monohydrate (phen·H2O), benzal-
dehyde, 1-naphthaldehyde, 1-anthrathaldehyde, and bromoethane
were purchased from Aldrich Chemical Co. [Cu(NCCH3)4]BF4 was
prepared according to a literature procedure.[6b]
The sensitivity (I0/I100, where I0 and I100 represent the
luminescent intensities in 100% nitrogen and 100% oxygen,
respectively) values of all of the samples are also displayed
in Table 4. Composite systems containing 1 showed the
highest sensitivity whether utilizing MCM-41 or SBA-15 as
matrix as a result of its intense emission. Complex 2 encap-
sulated in MCM-41 with a loading level of 60 mgg–1 exhi-
bits the highest sensitivity, and as for the SBA-15 systems,
a loading level of 80 mgg–1 displays the best sensitivity.
Complex 3 incorporated into MCM-41 and SBA-15 with a
loading of 80 mgg–1 showed higher sensitivity than load-
ings at the 40 and 60 mgg–1 levels. The same variation trend
in sensitivity was also found for systems containing 4.
We speculate that this complex variation trend in sensi-
tivity can be explained as follows: There are at least two
opposite factors affecting the sensitivity of the samples:
emission intensity from the probe molecules and adverse
interaction between probe molecules (e.g., aggregation).
When the loading level is low, the emission from the probe
is comparatively weak, which will result in low sensitivity,
and when it is high, aggregation between the probe mole-
cules in the pores of the support may become serious. The
two opposite factors mentioned above probably affect the
sensing properties of the composite systems with different
contributions. For samples containing 1, the influence from
the two opposite factors may be equivalent, so sensing
properties at a loading level of 60 mgg–1 is the highest
among the three. As for 3 and 4, which exhibit much weaker
emission than 1, composite systems containing them with
the highest loading level shows the highest sensitivity, which
indicates that the emission intensity factor plays the pri-
mary role. In case of complex 2, it exhibits different varia-
tion trends in different supports. When encapsulated in
MCM-41, it displays behavior similar to that of 1 (influence
from the two opposite factors is almost equivalent):
60 mgg–1 is its optimal loading level, and when incorpo-
rated into SBA-15, it takes on the sensitivity variation trend
of 3 and 4 (emission intensity is the leading factor).
Synthesis of the NN Ligands
2-Phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (pip): The pip li-
gand was synthesized according to reported procedures.[6c,6d]
1-Ethyl-2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (epip): This
compound was synthesized according to a literature procedure with
some minor modifications.[6e] NaH (0.74 g, 20 mmol) was added to
anhydrous N,N-dimethylformamide (30 mL) in a 100 mL flask; the
mixture was stirred violently for 1 h. Then, pip (2.96 g, 10 mmol)
was added to the flask, and the mixture was stirred for 1 h. Bromo-
ethane (1.09 g, 10 mmol) was added to the resulting mixture, which
was heated at reflux for 24 h, cooled to room temperature, poured
into cold water and stirred for 30 min. A pale-purple precipitate
was obtained. The crude product was collected by filtration and
purified by recrystallization from methanol to give the product
(2.14 g, 72%) as a milk-white powder. 1H NMR (300 MHz, CDCl3,
25 °C): δ = 9.168 (m, 2 H, 2-H, 9-H), 9.070 (m, 1 H, 7-H), 8.610
(m, 1 H, 4-H), 7.729 (m, 4 H, 10-H, 14-H, 3-H, 8-H), 7.576 (m, 3
H, 11-H, 12-H, 13-H), 4.636 (q, 2 H, CH2), 1.594 (t, 3 H, CH3)
ppm. C21H16N4 (324.39): calcd. C 77.76, H 4.97, N 17.27; found C
77.74, H 4.99, N 17.25. IR (KBr pellet): ν = 3055, 2987, 2937,
˜
2879, 1595, 1562, 781, 739, 706, 548 cm–1.
2-(Naphthalen-1-yl)-1H-imidazo(4,5-f)(1,10)phenanthroline
(nip):
This compound was synthesized following methods reported in the
literature.[6c,6d,6f] 1-Naphthaldehyde (1.56 g, 10 mmol), 1,10-phen-
anthroline-5,6-dione (2.10 g, 10 mmol), ammonium acetate (0.15 g,
20 mmol), and acetic acid (30 mL) were added to a 100 mL flask.
The mixture was heated at reflux for 12 h. The product (3.25 g,
85%) was obtained was as a pale-yellow powder. 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 11.609 (s, 1 H, N-H), 9.124 (m, 2
H, 2-H, 9-H), 8.786 (m, 1 H, 16-H), 8.535 (m, 1 H, 7-H), 7.942 (m,
3 H, 4-H, 12-H, 13-H), 7.717 (m, 1 H, 10-H), 7.633 (m, 1 H, 11-
H), 7.560 (m, 4 H, 3-H, 8-H, 14-H, 15-H) ppm. C23H14N4 (346.39):
calcd. C 79.75, H 4.07, N 16.17; found C 79.73, H 4.06, N 16.19.
IR (KBr pellet): ν = 3049, 1608, 1562, 885, 798, 775, 738 cm–1.
˜
1-Ethyl-2-(naphthalen-1-yl)-1H-imidazo(4,5-f)(1,10)phenanthroline
(enip): The synthesis procedure for enip was similar to that of epip,
except nip (3.18 g, 10 mmol) was used in place of pip. The product
(3.14 g, 74 %) was obtained as a milk-white powder. 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 9.176 (m, 2 H, 2-H, 9-H), 9.090 (d,
J = 4.5 Hz, 1 H, 16-H), 8.654 (m, 1 H, 7-H), 8.089 (m, 1 H, 4-H),
Conclusions
A series of luminescent copper(I) complexes {[Cu-
(dpephos)(NN)]BF4} were synthesized and characterized, 7.987 (m, 1 H, 13-H), 7.721 (m, 3 H, 10-H, 11-H, 12-H), 7.669 (m,
Eur. J. Inorg. Chem. 2009, 2294–2302
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2299

L. Shi, B. Li
FULL PAPER
1 H, 8-H), 7.543 (m, 2 H, 3-H, 15-H), 7.489 (m, 1 H, 14-H), 4.421
(q, 2 H, CH2), 1.435 (t, 3 H, CH3) ppm. C25H18N4 (374.45): calcd. 103 mg (84%). H NMR (300 MHz, CDCl3, 25 °C): δ = 9.128 (m,
Complex 4: The enip ligand (37 mg, 0.1 mmol) was used. Yield:
1
C 80.19, H 4.85, N 14.96; found C 80.17, H 4.86, N 14.98. IR (KBr
2 H, 2-H, 9-H), 8.742 (d, J = 5.4 Hz, 2 H, 4-H, 7-H), 8.109 (d, J
= 6.0 Hz, 1 H, 16-H), 7.999 (d, J = 6.0 Hz, 1 H, 13-H), 7.617 (m,
7 H, 3-H, 8-H, 10-H, 11-H, 12-H, 14-H, 15-H), 7.318 (m, 6 H, 21-
H, 26-H, 31-H, 34-H, 39-H, 44-H), 7.145 (m, 8 H, 20-H, 22-H, 25-
H, 27-H, 38-H, 40-H, 43-H, 45-H), 6.998 (m, 12 H, 19-H, 23-H,
24-H, 28-H, 29-H, 32-H, 33-H, 36-H, 37-H, 41-H, 42-H, 46-H),
6.285 (m, 2 H, 29-H, 36-H), 4.593 (q, 2 H, CH2), 1.445 (t, 3 H,
CH3) ppm. C61H46BCuF4N4OP2 (1063.36): calcd. C 68.90, H 4.36,
pellet): ν = 3050, 2987, 1616, 1562, 875, 793, 739 cm–1.
˜
2-(Anthracen-9-yl)-1-ethyl-1H-imidazo(4,5-f)(1,10)phenanthroline
(aeip): The synthesis procedure for aeip was similar to that of enip,
except 1-anthrathaldehyde (2.36 g, 10 mmol) was used in place of
1
1-naphthaldehyde. H NMR (300 MHz, CDCl3, 25 °C): δ = 9.256
(m, 2 H, 2-H, 9-H), 9.148 (m, 1 H, 10-H), 8.718 (m, 2 H, 4-H, 7-
H), 8.151 (m, 2 H, 14-H, 15-H), 7.777 (m, 2 H, 11-H, 18-H), 7.571
(m, 4 H, 3-H, 8-H, 16-H, 13-H), 7.468 (m, 2 H, 12-H, 17-H), 4.329
(q, 2 H, CH2), 1.320 (t, 3 H, CH3) ppm. C29H20N4 (424.51): calcd.
C 82.05, H 4.75, N 13.20; found C 82.03, H 4.77, N 13.19. IR
N 5.27; found C 68.92, H 4.34, N 5.25. IR (KBr pellet): ν = 3055,
˜
2995, 1597, 1566, 1435, 1261, 1058, 874, 804, 777, 741 cm–1.
Complex 5: The aeip ligand (42 mg, 0.1 mmol) was used. Yield:
1
(KBr pellet): ν = 3052, 2985, 2931, 1627, 1598, 1562, 736, 688, 661,
˜
109 mg (86%). H NMR (300 MHz, CDCl3, 25 °C): δ = 9.266 (m,
688 cm–1.
1 H, 9-H), 9.186 (d, J = 6.3 Hz, 1 H, 2-H), 8.811 (d, J = 5.5 Hz, 1
H, 7-H), 8.762 (s, 1 H, 4-H), 8.683 (d, J = 5.5 Hz, 1 H, 10-H),
8.167 (d, J = 6.3 Hz, 2 H, 14-H, 15-H), 8.105 (m, 1 H, 11-H), 7.648
(m, 1 H, 18-H), 7.548 (m, 2 H, 3-H, 8-H), 7.481 (m, 4 H, 12-H,
13-H, 16-H, 17-H), 7.324 (m, 6 H, 21-H, 26-H, 31-H, 34-H, 39-H,
44-H), 7.167 (m, 8 H, 20-H, 22-H, 25-H, 27-H, 38-H, 40-H, 43-H,
45-H), 7.095 (d, J = 6.3 Hz, 2 H, 32-H, 33-H), 7.017 (t, 10 H, 19-
H, 23-H, 24-H, 28-H, 37-H, 41-H, 42-H, 46-H, 30-H, 35-H), 6.817
(m, 2 H, 29-H, 36-H), 4.472 (q, 2 H, CH2), 1.347 (t, 3 H, CH3)
ppm. C65H48BCuF4N4OP2 (1113.42): calcd. C 70.12, H 4.35, N
Synthesis of Complexes 1–5: The five complexes were synthesized
following a procedure similar to that reported in the literature.[6a]
A typical procedure is outlined for 1. The synthesis procedures for
2–5 were essentially identical to that described for 1, only the quan-
tities of the NN ligands differed.
Complex 1: A 100 mL flask was charged with [Cu(CH3CN)4]BF4
(31 mg, 0.1 mmol), dpephos (54 mg, 0.1 mmol) and dichlorometh-
ane (10 mL), and the mixture was stirred for 1 h. Then, pip (30 mg,
0.1 mmol) was added, and the mixture was stirred for 1 h. After
evaporation of the solvent, the product (80 mg, 70%) was obtained
as a yellow powder. 1H NMR (300 MHz, CDCl3, 25 °C): δ = 9.253
(d, J = 5.4 Hz, 2 H, 2-H, 9-H), 8.547 (d, J = 5.5 Hz, 2 H, 4-H, 7-
H), 8.436 (d, J = 5.7 Hz, 2 H, 10-H, 14-H), 7.629 (m, 2 H, 3-H, 8-
H), 7.580 (m, 2 H, 11-H, 13-H), 7.472 (t, 1 H, 12-H), 7.296 (m, 2
H, 31-H, 34-H), 7.240 (m, 4 H, 29-H, 32-H, 33-H, 36-H), 7.097 (t,
12 H, 20-H, 21-H, 22-H, 25-H, 26-H, 27-H, 38-H, 39-H, 40-H, 43-
H, 44-H, 45-H), 6.980 (m, 8 H, 19-H, 23-H, 24-H, 28-H, 37-H, 41-
H, 42-H, 46-H), 6.811 (m, 2 H, 30-H, 35-H) ppm. C55H40BCuF4-
N4OP2 (985.25): calcd. C 67.05, H 4.09, N 5.69; found C 67.03, H
5.03; found C 70.14, H 4.33, N 5.05. IR (KBr pellet): ν = 3054,
˜
2931, 2859, 1627, 1564, 1429, 1261, 1054, 802, 738, 688, 509 cm–1.
Preparation of Mesoporous Silica MCM-41, SBA-15, and the Com-
posite Systems: Mesoporous silica MCM-41 and SBA-15 were pre-
pared following the reported procedure with some minor modifica-
tions.[17] As can be seen from Figure 4, the SAXRD measurements
reveal that blank MCM-41 show three well-resolved broad Bragg
reflections that can be indexed as d100, d110, and d200, which are
the characteristics of a well-ordered hexagonal mesostructure.[13a]
SAXRD results of the undoped SBA-15 consists of a strong (100)
reflection at a low-angle region ranging from 0.7 to 1° (2θ) and
three small peaks (110, 200, 210) located at the higher angle ran-
ge.[13b] The pore size of SBA-15 is larger than that of MCM-41.
Complex/MCM-41 and complex/SBA-15 composite materials were
prepared respectively by the following procedure. In a typical prep-
aration, 1 (4 mg) was added into dichloromethane (10 mL), and the
mixture was stirred for 1 h. Then MCM-41 or SBA-15(0.10 g) was
added into the dichloromethane solution of 1. The mixture was
stirred for 24 h at room temperature and filtered. The obtained
powder was washed several times with the solvent until no 1 existed
in the filtrate. The powder was dried in air, and target sample 1/
MCM-41 or 1/SBA-15 was obtained. The samples with different
loading levels (40, 60, and 80 mgg–1 MCM-41 or SBA-15) were
prepared by altering the concentration of initial solution of 1, 2, 3,
and 4, respectively.
4.11, N 5.66. IR (KBr pellet): ν = 3483, 3055, 1612, 1433, 1265,
˜
1074, 804, 737, 694, 515 cm–1.
Complex 2: The epip ligand (32 mg, 0.1 mmol) was used. Yield:
1
85 mg (73%). H NMR (300 MHz, CDCl3, 25 °C): δ = 9.112 (m,
2 H, 2-H, 9-H), 8.696 (d, J = 6.0 Hz, 1 H, 7-H), 8.656 (d, J =
5.5 Hz, 1 H, 4-H), 7.985 (m, 1 H, 12-H), 7.775 (m, 2 H, 10-H, 14-
H), 7.618 (m, 4 H, 3-H, 8-H, 11-H, 13-H), 7.312 (t, 2 H, 31-H, 34-
H), 7.238 (m, 4 H, 21-H, 26-H, 39-H, 44-H), 7.113 (m, 10 H, 20-
H, 22-H, 25-H, 27-H, 38-H, 40-H, 43-H, 45-H, 30-H, 35-H), 6.989
(t, 10 H, 19-H, 23-H, 24-H, 28-H, 29-H, 36-H, 37-H, 41-H, 42-H,
46-H), 6.781 (m, 2 H, 29-H, 36-H), 4.832 (q, 2 H, CH2), 1.619 (t,
3 H, CH3) ppm. C57H44BCuF4N4OP2 (1013.30): calcd. C 67.56, H
4.38, N 5.53; found C 67.54, H 4.40, N 5.55. IR (KBr pellet): ν =
˜
3469, 3057, 2943, 2875, 1626, 1566, 1435, 1263, 1055, 804, 740,
696, 513 cm–1.
Physical Measurements: The IR spectra were acquired with a
Complex 3: The nip ligand (35 mg, 0.1 mmol) was used. Yield:
Magna560 FTIR spectrophotometer. Element analyses were per-
1
100 mg (83%). H NMR (300 MHz, CDCl3, 25 °C): δ = 12.673 (s, formed with a Vario Element Analyzer. 1H NMR spectra were ob-
1 H, N-H), 9.281 (m, 3 H, 2-H, 9-H, 16-H), 8.566 (m, 2 H, 4-H, tained with a Bruker Avance 300 MHz spectrometer with tet-
7-H), 8.338 (m, 1 H, 13-H), 7.903 (m, 2 H, 10-H, 12-H), 7.654 (m,
ramethylsilane as the internal standard. The absorption spectra
4 H, 3-H, 8-H, 14-H, 15-H), 7.524 (m, 1 H, 11-H), 7.304 (m, 2 H, were recorded with a Shimadzu Model 3100 spectrometer and the
31-H, 34-H), 7.231 (m, 4 H, 21-H, 26-H, 39-H, 44-H), 7.114 (m, 8 photoluminescence spectra were obtained by a Hitachi F-4500
H, 20-H, 22-H, 25-H, 27-H, 38-H, 40-H, 43-H, 45-H), 7.074 (m, 4
H, 30-H, 32-H, 33-H, 35-H), 7.000 (t, 8 H, 19-H, 23-H, 24-H, 28-
fluorescence spectrophotometer equipped with a monochromator
(resolution: 0.2 nm) and a 150W Xe lamp as the excitation source.
H, 37-H, 41-H, 42-H, 46-H), 6.805 (m, 2 H, 29-H, 36-H) ppm. The excited-state lifetimes were determined by using a conventional
C59H42BCuF4N4OP2 (1035.31): calcd. C 68.45, H 4.09, N 5.41;
Nd:YAG (neodymium yttrium aluminum garnet) laser system. The
photoluminescence quantum yield is defined as the number of pho-
tons emitted per photon absorbed by the system and was measured
found C 68.43, H 4.07, N 5.43. IR (KBr pellet): ν = 3504, 3055,
˜
1564, 1433, 1263, 1070, 771, 741, 696, 509 cm–1.
2300
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 2294–2302

CuI Complexes with 1,10-Phenanthroline Derivative Ligands
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1–10° with 0.01° step and scanning speed was 1 sstep–1.
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[2]
[3]
Crystallography: Yellow single crystals of 3·6C2H5OH and
4·2C2H5OH suitable for X-ray diffraction studies were obtained by
slow evaporation from dichloromethane/ethanol solution and mea-
sured with a Bruker Smart Apex CCD single-crystal diffractometer
by using λ(Mo-Kα) radiation (0.7107 Å at 273 K). An empirical
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Table S1 (Supporting Information), whereas selected bond lengths
and angles were given in Table 1. CCDC-717860 (for 3·6C2H5OH),
and -717861 (for 4·2C2H5OH) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
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www.ccdc.cam.ac.uk/data_request/cif.
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Oxygen-Sensing Properties Test: Oxygen-sensing properties of our
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different concentrations via gas flow controllers and passed directly
to the sealed gas chamber. We typically allowed 1 min between
changes in the N2/O2 concentration to ensure that a new equilib-
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the luminescence intensity remained constant. The sensor response
curves were obtained by using a similar method. The experiments
were carried out in the dark at room temperature.
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Supporting Information (see footnote on the first page of this arti-
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4·2C2H5OH; Demas model oxygen-quenching fitting parameters
for the composite systems; absorption spectra of 1–5 the ligands;
solid-state photoluminescence lifetime decay curve of 1–4; UV/Vis
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[9]
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[11]
Acknowledgments
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The authors are grateful for the financial support of the Chinese
Academy of Sciences (One Hundred Talents Project) and the
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