Thermosensitive Seven-Coordinate TbIII Complexes with LLCT Transitions

Article abstract of DOI:10.1002/ejic.201800281

Seven-coordinate Tb^III complexes with strong luminescence and thermosensing properties are reported. Mononuclear [Tb(tmh)₃(PEB)] [tmh: 2,2,6,6-tetramethyl-3,5-heptanedione, PEB: (diphenylphosphoryl)ethynyl]benzene and dinuclear [Tb

Full text of DOI:10.1002/ejic.201800281

A Journal of
Accepted Article
Title: Thermo-sensitive luminophores using seven-coordinate TbIII
complexes based on LLCT transition
Authors: Pedro Paulo Ferreira da Rosa, Takayuki Nakanishi, Yuichi
Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi, and
Yasuchika Hasegawa
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201800281
Link to VoR: http://dx.doi.org/10.1002/ejic.201800281

10.1002/ejic.201800281
European Journal of Inorganic Chemistry
FULL PAPER
Thermo-sensitive luminophores using seven-coordinate TbIII
complexes based on LLCT transition
Pedro Paulo Ferreira da Rosa,[b] Takayuki Nakanishi,[a] Yuichi Kitagawa, [a] Tomohiro Seki, [a]
Hajime Ito, [a] Koji Fushimi, [a] and Yasuchika Hasegawa*[a]
Abstract: Seven-coordinate TbIII complexes with strong-
luminescence and thermo-sensing properties are reported. Mono-
nuclear [Tb(tmh)3(PEB)] (tmh: 2,2,6,6-tetramethyl-3,5-heptanedione,
transition.[20] Control of the ligand field is essential for the design
of luminescent metal complexes.
The electronic transitions of luminescent lanthanide
complexes are much different from those of transition metal
PEB:
(diphenylphosphoryl)ethynyl)benzene))
(m-BPEB:
and
Di-nuclear
1,3-
[Tb2(tmh)6(m-BPEB)]
complexes. Lanthanide complexes have
characteristic
bis(diphenylphosphoryl)ethynyl)benzene) were characterized by
single-crystal X-ray analysis. The quantum yields of [Tb(tmh)3(PEB)]
and [Tb2(tmh)6(m-BPEB)] were estimated to be 71 and 39 %,
respectively. Thermo-sensing properties are evaluated by
temperature depended emission lifetime measurements (Arrhenius
analysis), which are affected by presence of ligand-to-ligand charge
transfer (LLCT) bands. The LLCT bands are confirmed by DFT
calculations.
photophysical properties derived from the metal centered 4f-4f
transitions. The 4f-4f emission is based on the electric-dipole
Laporte-forbidden transition with small offset, which leads to
distinctive emission with high color purity (fwhm ˂ 10 nm) and long
emission lifetime ( ˃1 μs).[21] It has been widely accepted that the
4f-4f intrinsically forbidden transitions can be partially allowed by
mixing 5d states through the ligand field effect, based on the
coordination structure. By the 4f-5d mixing, lanthanide complex
with highly asymmetrical coordination structure exhibits large
radiative rate constant (kr).[22,23] We reported strong luminescent
lanthanide complexes with asymmetric eight-coordinate square
antiprism (8-SAP, D4d), trigonal dodecahedron (8-TDH, D2d), and
nine-coordinate monocapped square antiprism (9-SAP, C4v)
structures.[24–26] Their coordination structures are composed of
EuIII ions, hexafluoroacetylacetonate and phosphine oxide ligands.
The level of symmetry in the coordination structure of lanthanide
complexes is important to improve their electronic transitions and
luminescence.
In order to obtain new symmetric structures around the
lanthanide ions, we successfully synthesized seven-coordinate
TbIII complex using sterically bulky tmh (2,2,6,6-tetramethyl-3,5-
heptanedione) and TPPO (triphenylphosphine oxide) ligands that
shows extremely high intrinsic emission quantum yield
([Tb(tmh)3(TPPO)]: Φff = 88%).[27] This high quantum yield is due
to both the formation of asymmetric seven-coordinate structure
(7-MCO, C3v) and high triplet state energy level of tmh ligand. The
asymmetric seven-coordination structure results in enlargement
of the kr of TbIII complex. The large energy gap between emitting
level of TbIII (5D4) and excited triplet level of tmh (T1) also leads to
suppression of back energy transfer (BEnT), resulting in decrease
of non-radiative rate constant (knr).[28] Seven-coordinate TbIII
complex with tmh and TPPO ligands provides high quantum
yields with large kr and small knr constants.
Introduction
Luminescent metal complexes have attracted attention because
of their versatile photophysical properties for applications such as
, , cellular
displays[1–3] fluorescent lamps[4], LED lights[2,3,5–10]
probes and sensors.[11–17] The emission based on their charge
transfer (CT) bands are strongly affected by the organic ligand
moieties, coordination structure and coordination number.
Various types of luminescent transition metal complexes have
been reported, recently. Langton described that RuII complex with
rotaxane units shows iodide recognition based on the
enhancement of metal-ligand charge transfer (MLCT)
emission.[18] The luminescence properties of PtII pyridyl
complexes are depended strongly on the ligand-metal interaction
and metal-metal-to-ligand charge transfer (MMLCT) transition.[19]
Wärnmark demonstrated a FeIII triazol complex showing room-
temperature photoluminescence with enhanced emission lifetime
through the doublet ligand-to-metal charge transfer (LMCT)
[a]
Dr. Y. Kitagawa, Dr. T. Nakanishi, Dr. T. Seki, Prof. K. Fushimi, Prof.
H. Ito, Prof. Y. Hasegawa
Faculty of Engineering
In this study, we present strong luminescent seven-
coordinate TbIII complexes with thermo-sensing properties.
Various types of thermo-sensitive TbIII complexes based on the
thermal activation of BEnT have been reported.[29–31]
Temperature-sensitive luminescent lanthanide complexes have
potential applications in electronics, fluidics and aeronautical
engineering[32] as responsive dyes.[33–37] Strong-luminescent
seven-coordinate [Tb(tmh)3(TPPO)], however, does not show the
thermo-sensing property because of the suppression of BEnT
process. Here, we designed novel seven-coordinate TbIII
Hokkaido University
Kita-13 Jo, Nishi-8 Chome, Sapporo, Hokkaido 060-8628
(Japan)
E-mail: hasegaway@eng.hokudai.ac.jp
Mr. P.P. Ferreira da Rosa
Graduate School of Chemical Sciences and Engineering
Hokkaido University
[b]
Kita-13 Jo, Nishi-8 Chome, Sapporo, Hokkaido 060-8628
(Japan)
Supporting information for this article is given via a link at the end of
the document
This article is protected by copyright. All rights reserved.

10.1002/ejic.201800281
European Journal of Inorganic Chemistry
FULL PAPER
complexes by introducing ethynyl groups in the phosphine oxide
ligand in order to promote new energy transfer pathways (Figure
1a). The ethynyl group in the phosphine oxide ligands expands
the π-conjugation system, which stabilizes their excited states.
This stabilization allows interaction between tmh and phosphine
oxide ligand for formation of ligand-to-ligand charge transfer
(LLCT) band. New energy transfer pathway using LLCT band
induces thermo-sensing properties in seven-coordinate TbIII
complexes (Figure 1b).
Information, Scheme S1). [Tb(tmh)3(TPPO)] (Tb-TPPO) was also
synthesized by the same method for comparison with TbIII
complexes using ethynyl groups. The single crystals of Tb-PEB
and Tb-BPEB were obtained by recrystallization from methanol
solution. The structures of Tb-PEB and Tb-BPEB were
determined by single-crystal X-ray analyses (Figure 2a and 2b).
The Tb-PEB is composed of one phosphine oxide ligand (PEB)
and Tb(tmh)3 unit forming a seven-coordinate structure. For di-
nuclear Tb-BPEB, two Tb(tmh)3 units are bridged by m-BPEB
ligand. The selected bond length between TbIII and O (phosphine
oxide) in Tb-PEB and Tb-BPEB were 2.31 and 2.35 Å,
respectively. Their bond lengths are similar to that in Tb-TPPO
(2.31 Å). We also found specific intermolecular CH/O and π/π
interactions that are only observed in the Tb-PEB structure
(Figure 2c). The selected distances and angles between the TbIII
and the O atoms directly reflect the coordination geometry of the
complex. Based on the crystal structures, we performed
continuous shape measures (CShM) calculations using
SHAPE[39–41] to determine the coordination geometrical structures
around the TbIII ions in the first coordination sphere. The SCShM
criterion represents the degree of deviation from ideal
coordination structure and is given by Equation (1):
Mono- and di-nuclear seven-coordinate TbIII complexes with
ethynyl
introduced
phosphine
oxides,
PEB
((diphenylphosphoryl)ethynyl)benzene) and m-BPEB (1,3-
bis(diphenylphosphoryl)ethynyl)benzene), were synthesized
(Figure 1c and 1d). Previously reported seven-coordinate
[Tb(tmh)3(TPPO)] was also prepared as a reference.[27] Their
coordination structures were characterized using single-crystal X-
ray diffraction analysis. Luminescence performances of the TbIII
complexes were evaluated using emission spectra, total emission
quantum yields and emission lifetimes. Their temperature-
sensitivities are estimated using temperature depended emission
lifetime measurements (Arrhenius analysis). We also discuss
about LLCT characteristics from density functional theory (DFT)
calculations. The seven-coordinate TbIII complex with ethynyl
group exhibits remarkable LLCT-assisted thermo-sensitive
luminescence, while maintaining high emission quantum yield.
The conceptual molecular design for strong luminescent and
thermo-sensitive TbIII complex can expand the frontier field of
coordination chemistry, photophysics and material science.
N
SCShM = min ∑∑
22 ×100
|
(1)
|
|
Q
- P
- Q
k
k
k
N
|
Q
k
0
k
where Qk is the vertices of an actual structure, Q0 is the center of
mass of an actual structure, Pk is the vertices of an ideal structure,
and N is the number of vertices. The estimated SCShM values of
the TbIII complexes are summarized in Table S2. On the basis of
the minimal value of SCShM, the pseudo-coordination polyhedral
structures of Tb-PEB and Tb-BPEB were categorized to be 7-
MCTP (monocapped-trigonal prismatic, point group: C2v) and 7-
MCO (monocapped-octahedral, point group: C3v), respectively.
Tb-TPPO was characterized as 7-MCO in a previous report.[27]
The asymmetric Tb-PEB with C2v point group is expected to
provide high emission quantum yield related to larger kr.
Figure 1. (a) Conceptual molecular design, (b) Energy diagram of TbIII
complexes with ethynyl group, (c) Mono-nuclear [Tb(tmh)3(PEB)], and (d) Di-
nuclear [Tb2(tmh)6(m-BPEB)].
Results and Discussion
Structure
Seven-coordinate
[Tb(tmh)3(PEB)]
(Tb-PEB)
and
Figure 2. Perspective view of (a) Tb-PEB and (b) Tb-BPEB without hydrogen
atoms, showing 50% probability displacement ellipsoids. (c) Representation of
intermolecular CH/O and π/π interactions in Tb-PEB.
[Tb2(tmh)6(m-BPEB)] (Tb-BPEB) were synthesized by the
complexation of phosphine oxide ligands (PEB and m-BPEB) with
precursor [Tb2(tmh)6][38] in methanol for 12 h (see Supporting
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10.1002/ejic.201800281
European Journal of Inorganic Chemistry
FULL PAPER
Φ
1
k
r
ff
Photophysical properties
τobs
=
=
, Φff =
(3)
k
k
+ k
k + k
r nr
r
r
nr
Excitation and emission spectra of Tb-PEB and Tb-BPEB in
solids are shown in Figure 3a. The transition bands at around 350
nm in excitation spectra are assigned to π-π* and/or σ-π*
transitions of the organic tmh ligands. The shoulder bands at
approximately 380 nm are due to 4f-4f transitions of TbIII (5G6,
5D3←7F6).[42] The emission bands at 490, 544, 582, 615 and 642
nm are caused by typical 4f-4f transitions of TbIII ions (5D4→7FJ (J
= 6,5,4,3 and 2)), respectively. The spectral shapes including the
stark splittings of Tb-PEB and Tb-BPEB are much similar to those
of Tb-TPPO and previous TbIII complexes with low-symmetrical
seven-coordinate structures (see Supporting Information, Figure
S1).[27,43,44]
In our experiments, the τobs and Φtot of Tb-PEB were larger than
those of Tb-TPPO. According to X-ray analysis and continuous
shape factor calculations, the coordination geometry of Tb-PEB
was categorized to be monocapped-trigonal prismatic structure
(7-MCTP, point groups: C2v). The combination of asymmetric C2v
structure and tight-packed molecular interactions (CH/O and π/π)
should provide a larger kr and smaller knr, respectively. The larger
kr and smaller knr enhances the Φff of Tb-PEB, which provides
longer τobs according to Equation 3.
The τobs and Φtot of Tb-BPEB are estimated as 0.81 ms and
39 %, respectively. The Φtot in Tb-BPEB is smaller than those of
Tb-TPPO, although their τobs and coordination structure (7-MCO,
point groups: C3v) are similar to those of Tb-TPPO. We propose
that the smaller Φtot of Tb-BPEB is due to inefficient energy
transfer (small ηsens) related to the presence of new energy
transfer pathways in the ethynyl-introduced TbIII complex.
Table 1. Photophysical properties
[a]
[b]
[c]
Chemical
formula
Point group
(geometry)
τobs
ms
/
Φtot
%
/
A[c]
s-1
/
Ea /
Name
cm-1
Tb-
PEB
[Tb(tmh)3
(PEB)]
C2v
(7-MCTP)
1.1 ×
108
3.6 ×
103
1.2
71
39
66
Tb-
BPEB
[Tb2(tmh)6
(m-BPEB)]
9.3 ×
108
3.8 ×
103
C3v (7-MCO)
C3v (7-MCO)
0.81
0.73
Tb-
TPPO
[Tb(tmh)3
(TPPO)][27]
－
－
[a] Emission lifetime (τobs) of the TbIII complexes were measured by
excitation at 355 nm (Nd:YAG 3ω) at room temperature. [b] Total emission
quantum yield (excited at 360 nm). [c] lnꢀ(1/τobs - 1/τ100K) = lnꢀ(kEnT) = lnꢀ(A) -
(Ea/kBT).
Figure 3. (a) Excitation and emission spectra of Tb-PEB (red line) and Tb-BPEB
(green line) in solids at room temperature. Excitation spectra were recorded in
respect to emission at 544 nm (5D4→7F6) and were normalized at 350 nm.
Emission spectra were excited at 350 nm. (b) Emission decay profiles of Tb-
PEB (red line) and Tb-BPEB (green line) in solids at room temperature excited
at 355 nm (Nd:YAG 3ω).
DFT calculations
The new energy transfer pathway in TbIII complexes with
ethynyl group was investigated using TD-DFT calculations
(B3LYP, 6-31G(d)) of excited Tb-TPPO and Tb-PEB using AlIII
ions instead of TbIII ions. Their molecular orbital representations
by Natural Transition Orbitals (NTO) are shown in Figure 4a and
4b (Complementary data: see Figure S2-S5). The NTO images
and energy levels of Tb-BPEB were also calculated (see
Supporting Information, Figure S6-S7). The electron densities for
S0-S1 and S0-T1 transitions of Tb-TPPO are localized in π orbitals
of tmh ligands (Figure 4a). On the other hand, the electron
densities in ground and excited states of Tb-PEB are located at
tmh and PEB ligand, respectively. These transitions from Tb-PEB
are interpreted to be ligand-to-ligand charge transfer (LLCT)
transitions. The energy levels of the lowest excited singlet (S1)
and triplet (T1) states of Tb-TPPO, Tb-PEB and Tb-BPEB were
Time-resolved emission profiles of Tb-PEB and Tb-BPEB at
room temperature reveal single-exponential decays with
millisecond scale lifetimes. The emission lifetimes observed from
the 5D4 excited level (τobs) were determined from the slope of the
logarithmic decay profiles (Figure 3b). Total emission quantum
yields Φtot for excitation at 360 nm were directly measured with an
integrating-sphere unit. The τobs and Φtot of Tb-PEB, Tb-BPEB and
Tb-TPPO are summarized in Table 1. The Φtot is composed of
intrinsic emission quantum yield (Φff) and energy transfer
efficiency (ηsens) as expressed in Equation 2. The τobs is also
directly related to Φff by Equation 3.
Φtot =Φff × ηsens
(2)
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10.1002/ejic.201800281
European Journal of Inorganic Chemistry
FULL PAPER
Temperature-depended emission lifetimes were measured to
investigate the temperature sensitivity of the TbIII complexes
(Figure 5a). The emission lifetimes of Tb-TPPO were also
measured as a reference. Tb-TPPO did not show any change in
the emission lifetime from 100 to 400 K. We found that TbIII
complexes with ethynyl groups showed decrease in the emission
lifetime from 340 to 400 K. These emission lifetimes changes are
caused by the energy transfer to the LLCT transitions in Tb-PEB
and Tb-BPEB. This quenching process is depended on the
energy-transfer rate kEnT
.
Figure 5. (a) Temperature-depended emission lifetimes of Tb-TPPO (black
square), Tb-PEB (red triangle) and Tb-BPEB (green circle) excited at 355 nm
(Nd:YAG 3ω), and the (b) Arrhenius plot for energy-transfer rate of Tb-PEB (red
triangle) and Tb-BPEB (green circle). Arrhenius equation: lnꢀ(1/τobs - 1/τ100K) =
lnꢀ(kEnT) = lnꢀ(A) - (Ea/kBT).
From the Arrhenius plots of the energy-transfer rate kEnT
5
from the D4 to the LLCT state, the activation energy Ea and the
Figure 4. Molecular orbital representations of the lowest triplet and singlet
excited states of (a) Tb-TPPO and (b) Tb-PEB simplified by NTO showing the
highest transition probability. (c) Energy diagram for the lowest triplet and singlet
excited states for Tb-TPPO, Tb-PEB and Tb-BPEB. DFT calculations were
performed using AlIII ions instead of TbIII ions for all complexes.
frequency factor A were estimated (Figure 5b, Table 1). The Ea of
Tb-PEB (3.6×103 cm-1) are similar to that of Tb-BPEB (3.8×103
cm-1). We consider that thermo-quenching process from 5D4
excited state of TbIII to the LLCT state in Tb-PEB is similar to that
of Tb-BPEB.
summarized in Figure 4c.
With the introduction of the ethynyl group in phosphine
oxides, their π-conjugation systems were expanded allowing for
the effective stabilization of LUMO (HOMO and LUMO levels: see
Supporting Information, Table S3 and Figure S8). The lower
LUMO in PEB and m-BPEB facilitates the interaction between tmh
and phosphine oxide ligand for formation of ligand-to-ligand
charge transfer (LLCT) bands (frequency oscillator of S0-S1 and
S0-T1 transition: see Table S4-S6); the oscillator strengths of
LLCT bands are explained using calculated and measured
absorption spectra: see Figure S9). These charge transfer bands
in Tb-PEB and Tb-BPEB provide new energy transfer pathways
in lower energetic levels, which are closer to the TbIII excited
states (5D4 : 20500 cm-1).[42]
Figure 6. Potential curves showing the energy transfer from TbIII excited state
(5D4) to the ligands’ excited states.
Thermo-sensitivity
Thermo-sensitive measurements through change in
emission lifetime have been reported as a precise and reliable
evaluation for estimation of performance in thermo-sensors.[45–48]
In order to understand the thermo-sensitivity of Tb-PEB and
Tb-BPEB, the potential curves of those complexes were
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10.1002/ejic.201800281
European Journal of Inorganic Chemistry
FULL PAPER
Preparation
of
(diphenylphosphoryl)ethynyl)benzene
(PEB):
hypothesized (Figure 6). The left potential curve in Figure 6 is a
5
combination of excited D4 (TbIII) and grounded S0 (tmh) states,
Ethynylbenzene (A, 1.02 g, 10 mmol) was dissolved in dry THF (60 mL),
and a solution of n-BuLi (7.5 mL, 1.6 M hexane, 12 mmol) was added
dropwise at -80 °C in ca. 15 min. The mixture was allowed to stir for 3h at
-10 °C, after which (2.28 mL, 12 mmol) was added dropwise at -80 °C. The
mixture was gradually brought to room temperature and stirred for 15 h.
The product was extracted with dichloromethane, washed with brine three
times, and dried over with anhydrous MgSO4. The solvent was evaporated,
and the obtained pale white solid was placed with dichloromethane (30
mL) in a flask. The solution was cooled to 0 °C, and then 30% H2O2
aqueous solution (5 mL) was added to it. The reaction mixture was stirred
for 3 h. The product was extracted with dichloromethane; the extracts were
purified by column chromatography on SiO2 using ethyl acetate and
hexane as mixed eluent (silica gel, ethyl acetate:hexane = 3:1) to afford
PEB.
TbIII*-L. The right potential curves are composed of grounded 7F6
(TbIII) and excited states of ligands, TbIII-L*. Here, we normalized
the energy level of left curve for comparison of activation energy
in energy transfer process (thermo-sensitivity). The cross-points
represent the activation energies (Ea). In the case of Tb-PEB and
Tb-BPEB, the energy level of right potential curve is decreased
by the formation of LLCT transitions, resulting in smaller Ea. The
smaller Ea leads to effective thermo-sensing property in seven-
coordinate TbIII complex. On the other hand, Tb-TPPO does not
show thermo-sensitivity because of the high energy level in which
the cross-point is situated.
The A values for Tb-PEB and Tb-BPEB are 1.1×108 and
9.3×108 s-1, respectively. The A value is affected by the electronic
coupling of the 5D4 configuration with the LLCT state. This
calculation results indicate that the degree of electronic coupling
Yield: 1.45 g (48%). 1H NMR (400 MHz, CDCl3, 25°C): δ 7.87-7.94 (q, 4H,
-CH), δ 7.62-7.43 (m, 9H, -CH), δ 7.36-7.41 (t, 2H, -CH) ppm. 13C NMR
(100 MHz, CDCl3, 25°C): δ 133.8, 132.7, 132.4, 131.2, 131.1, 130.8, 128.9,
128.7, 83.8, 82.1 ppm. 31P NMR (162 MHz, CDCl3, 25°C): δ 8.96 (s, 1P)
ppm. ESI-MS (m/z): calcd. for C20H16OP [PEB+H]+: 303.09, found 303.09.
Elemental analysis calcd.(%) for C20H15OP: C, 79.46; H, 5.00. Found C,
79.13; H, 4.92.
5
of D4 and the LLCT state for Tb-PEB is smaller than that of Tb-
BPEB. The Ea and A values of seven-coordinate TbIII complex are
depended on the presence of LLCT band. We successfully
observed thermo-sensing ability in TbIII complexes with ethynyl
groups.
Preparation of 1,3-bis(diphenylphosphoryl)ethynyl)benzene (m-
BPEB): 1,3-diethynylbenzene (B, 1.26 g, 10 mmol) was dissolved in dry
THF (60 mL), and a solution of n-BuLi (15 mL, 1.6 M hexane, 24 mmol)
was added dropwise at -80 °C in ca. 15 min. The mixture was allowed to
stir for 3h at -10 °C, after which (4.56 mL, 24 mmol) was added dropwise
at -80 °C. The mixture was gradually brought to room temperature and
stirred for 15 h. The product was extracted with dichloromethane, washed
with brine three times, and dried over with anhydrous MgSO4. The solvent
was evaporated, and the obtained pale white solid was placed with
dichloromethane (30 mL) in a flask. The solution was cooled to 0 °C, and
then 30% H2O2 aqueous solution (10 mL) was added to it. The reaction
Conclusion
Novel mono- and di-nuclear seven-coordinate TbIII
complexes with ethynyl groups in the phosphine oxide ligand were
synthesized. Tb-PEB showed remarkable total emission quantum
yield due to a large kr and small knr from an asymmetrical
coordination structure and strong intermolecular interactions. We
also successfully demonstrated the thermo-sensing properties of
Tb-PEB and Tb-BPEB from 340 to 400 K. These thermo-sensing
properties are enabled by the introduction of ethynyl groups in the
phosphine oxide ligand. DFT calculations of Tb-PEB and Tb-
BPEB prove the formation of ligand-to-ligand charge transfer
(LLCT) band from tmh to phosphine oxide ligands. We consider
that new energy transfer pathway using LLCT band induces
thermo-sensing properties in seven-coordinate TbIII complexes.
Highly luminescent seven-coordinate TbIII complexes with
thermo-sensitive properties have the potential to break new
ground in fields of coordination chemistry, thermodynamics and
photophysical science.
mixture was stirred for
3 h. The product was extracted with
dichloromethane; the extracts were washed with ethyl acetate to afford a
white powder. The powder was recrystallized from methanol to give
colorless chunk-shaped crystals.
Yield: 2.61g (49.6%). 1H NMR (400 MHz, CDCl3, 25°C): δ 7.85-7.92 (q, 8H,
-CH), δ 7.82 (s, 1H, -CH), δ 7.65-7.68 (d, 2H, -CH), δ 7.48-7.60 (m, 12H, -
CH), δ 7.40-7.44 (t, 1H, -CH) ppm. 13C NMR (100 MHz, CDCl3, 25°C): δ
136.3, 134.4, 133.3, 132.6, 132.1, 131.2, 131.1, 129.2, 129.0, 128.8, 85.4,
83.7 ppm. 31P NMR (162 MHz, CDCl3, 25°C): δ 9.15 (s, 2P) ppm. ESI-MS
(m/z): calcd. for C34H25P2O2 [m-BPEB+H]+
: 527.13, found 527.13.
Elemental analysis calcd.(%) for C34H24P2O2: C, 77.56; H, 4.59. Found C,
77.51; H, 4.48.
Preparation of [Tb(tmh)3(TPPO)] (Tb-TPPO), [Tb(tmh)3(PEB)] (Tb-
PEB), [Tb2(tmh)6(m-BPEB)] (Tb-BPEB): The precursor complex,
[Tb2(tmh)6], was synthesized as described in previous report.[38]
[Tb2(tmh)6] (0.87 g, 0.6 mmol), and phosphine oxide ligands (TPPO: 0.33
g, 1.2 mmol; PEB: 0.36 g, 1.2 mmol; m-BPEB: 0.32 g, 0.6 mmol) were
dissolved in methanol. The solutions were heated at reflux while stirring
for 12 h. The solution was concentrated by an evaporator, and then filtrated
with addition of new methanol into solution. That mixture was left to
recrystallize giving colorless crystals.
Experimental Section
General Methods: All chemicals were reagent grade and used without
further purification. Infrared spectra were recorded on a JASCO FT/IR-420
spectrometer. ESI-MS spectra were measured using a JEOL JMS-T100LP
and a Thermo Scientific Exactive. Elemental analyses were performed on
a J-Science Lab JM 10 Micro Corder and an Exeter Analytical CE440. 1H
NMR (400 MHz) spectra were recorded on a JEOL ECS400. 13C NMR
(100 MHz) and 31P NMR (162 MHz) spectra were recorded on a JEOL
ECX400. Chemical shifts were reported in δ ppm, referenced to an internal
tetramethylsilane standard for 1H NMR and internal 85% H3PO4 standard
for 31P NMR.
ꢁ
[Tb(tmh)3(TPPO)] (Tb-TPPO): Yield: 0.48 g (40%). IR (ATR) ꢀ = 2835-
3002 (m, C-H), 1573 (s, C=O), 1194 (s, P=O). ESI-MS (m/z): calcd. for
C51H73O7PTb [(Tb-TPPO)+H]+: 987.42, found 987.43. Elemental analysis
calcd.(%) for C51H72O7PTb: C, 62.06; H, 7.35. Found C, 62.02; H, 7.30.
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ꢁ
[Tb(tmh)3(PEB)] (Tb-PEB): Yield: 0.28 g (23%). IR (ATR) ꢀ = 2835-3002
(m, C-H), 1571 (s, C=O), 1194 (s, P=O). ESI-MS (m/z): calcd. for
C42H53O5PTb[(Tb-PEB)-tmh]+: 827.29, found 827.30. Elemental analysis
calcd.(%) for C53H72O7PTb: C, 62.96; H, 7.18. Found C, 62.77; H, 7.16.
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Keywords: Terbium • Luminescence • Lanthanide • Thermo-
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Novel seven coordinate TbIII
Thermo-sensitive luminophore
complexes with ethynyl group in
phosphine oxide ligands are
Pedro Paulo Ferreira da Rosa,
Takayuki Nakanishi, Yuichi Kitagawa,
Tomohiro Seki, Hajime Ito, Koji
Fushimi, Yasuchika Hasegawa*
synthesized and their photophysical
properties are investigated. The
introduction of ethynyl groups
promoted thermo-sensing properties
through LLCT transitions while
showing intense luminescence.
Page No. – Page No.
Thermo-sensitive luminophores
using seven-coordinate TbIII
complexes based on LLCT
transition
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