ChemComm
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DOI: 10.1039/C8CC05147J
Journal Name
COMMUNICATION
Turbomole (B3LYP/def-SV(P)) were carried out. The quantum the electric-dipole transitions of [Eu(+tfc)3(dpbp)]n were
chemical calculation indicates that the absorption energies of estimated to be 0.17 and – 0.015, respectively. The gCPL value
ligand moieties in the [Eu(+tfc)3(dpbp)]n are higher than those of [Eu(+tfc)3(dpbp)]n is twice as large as that of corresponding
in the [Eu(+tfc)3(tppo)2] (see Supplementary Information [Eu(+tfc)3(tppo)2] (gCPL at 586 nm = 0.09, see Supplementary
Figure S4), which is consistent with the excitation spectra Information Figure S7b). Recently, Yuasa reported large gCPL
where the band due to the +tfc ligand is shift to the blue side value of aggregated Cs[Eu(+/-hfbc)4].10 The spiral structure of
in [Eu(+tfc)3(dpbp)]n compared with [Eu(+tfc)3(tppo)2] (Fig. 3). the poly-nuclear Eu(III) coordination polymers also promotes
The experimentally estimated Ea (Table 1) also indicates that T1 enhancement of optical activity in solid state.
level of [Eu(+tfc)3(dpbp)]n is higher than those in the The spiral Eu(III) coordination polymer [Eu(+/-tfc)3(dpbp)]n
[Eu(+tfc)3(tppo)2]. Since T1 level of a dpbp ligand (21900 cm-1)7 successfully provides high emission quantum yield, thermo-
is much higher than emitting level of Eu(III) ion (17200 cm-1)8, stability and chiroptical activity. We also found remarkable
the T1 states in Eu(III) complexes are mainly composed of enhancement of the photosensitized energy transfer efficiency
localized excited states of tfc moiety. The T1 levels of tfc should of [Eu(+tfc)3(dpbp)]n for luminescent materials. The spiral
be dependent on the distortion angles of π-conjugated plane Eu(III) coordination polymers with CPL are expected to
in tfc ligands (see Supplementary Information). We consider contribute to the novel molecular design for optically active
the energy level of T1 in [Eu(+tfc)3(dpbp)]n is higher than that molecular materials.
of [Eu(+tfc)3(tppo)2]. Thus, the higher energy level of ligand
moieties in the [Eu(+tfc)3(dpbp)]n suppress back energy
Notes and references
transfer from excited Eu(III) to ligands, resulting in the high
+
emission quantum yield.
[Eu(+tfc)3(dpbp)]n: Yield 0.16 g (56%). FAB-Mass (m/z): [M − tfc]
The CD and CPL spectra of [Eu(+/-tfc)3(dpbp)]n in solid state
are shown in Fig. S6 and Fig. 4, respectively (experimental
condition: see Supplementary Information). We observed CD
signals of the coordinated +/-tfc in π−π∗ transition band (350
nm). The absence of CD signals at around 300 nm might be
caused by weakly exciton coupled CD signals.9 Small CD signals
at around 420 and 440 nm are considered to be due to 4f-4f
transitions of Eu(III) (7F0-5Lx).
calcd for [C60H56EuF6O6P2], 1201.2; found, 1201.2. Anal. Calcd for
[C72H70EuF9O8P2]: C, 59.71; H, 4.87. Found: C, 59.47; H, 4.86.
[Eu(-tfc)3(dpbp)]n: Anal. Calcd for [C72H70EuF9O8P2]: C, 59.71; H,
4.87. Found: C, 59.03; H,4.68.
Experimental details, thermogravimetric analysis, X-ray crystal
data, shape measure calculations, temperature dependent
emission lifetimes, DFT calculations, dihedral angles of tfc
ligands, chiroptical properties of [Eu(+/-tfc)3dpbp]n and
[Eu(+tfc)3(tppo)2]: see Supplementary Information.
The CPL signals are given by the difference between the left
and right circularly polarized emission intensities (ICPL = IL − IR ).
Crystallographic data: CCDC-1037529 (for [Eu(-tfc)3(dpbp)]n) and
CCDC 1037531 (for [Eu(+tfc)3(dpbp)]n). These data can be
obtained free of charge from The Cambridge Crystallographic
This work was supported by JSPS KAKENHI Grant Number
JP18H04497. This work was also partially supported by Grant-in-
Aid for Scientific Research on the 18H02041 and 18H04496.
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Fig. 4 Emission (upper figure) and CPL (lower figure) spectra of
[Eu(+tfc)3(dpbp)]n (black continuous lines) and [Eu(-
tfc)3(dpbp)]n (red dotted lines) in solid state.
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Effective CPL signals were observed at around 585 and 610
nm, based on D0−7F1 and D0−7F2 transitions, respectively. In
general, gCPL values for the magnetic-dipole transition are
notably larger than those for the electric-dipole transition in
Eu(III) compounds. The gCPL values for the magnetic-dipole and
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