Eu(III) Chiral Coordination Polymer with a Structural Transformation

Apr 27, 2017 - The chiroptical properties of the monomer form in liquid media were characterized by using circular dichroism and circularly polarized ...
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Eu(III) Chiral Coordination Polymer with a Structural Transformation System Naoyuki Koiso,† Yuichi Kitagawa,‡ Takayuki Nakanishi,‡ Koji Fushimi,‡ and Yasuchika Hasegawa*,‡ †

TOSOH Corporation, 2743-1, Hayakawa, Ayase, Kanagawa 252-1123, Japan Faculty of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, Sapporo, Hokkaido 060-8628, Japan

‡

S Supporting Information *

ABSTRACT: A luminescent Eu(III) chiral coordination polymer with a structural transformation system, [Eu(hfa)3((R)-bidp)]n (hfa: haxafluoroacetylacetonato, (R)-bidp: (R)-1,1′-binaphthyl-2,2′-bis(diphenylphosphinate), is reported. Single-crystal X-ray analysis revealed a characteristic helical polymer structure of [Eu(hfa)3((R)bidp)]n with hydrogen−fluorine/π interactions. [Eu(hfa)3((R)bidp)]n shows high thermostability (decomposition temperature = 320 °C) and strong luminescence properties (the 4f−4f emission quantum yield = 76%) in the solid state due to its tight packing and asymmetric structure. [Eu(hfa)3((R)-bidp)]n is also transformed from a polymer to monomer structure in liquid media. The chiroptical properties of the monomer form in liquid media were characterized by using circular dichroism and circularly polarized luminescence spectra. In this study, structural and photophysical properties of a luminescent Eu(III) chiral coordination polymer with a structural transformation system were demonstrated.

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INTRODUCTION Lanthanide complexes have been regarded as attractive luminescent materials because of their characteristic narrow emission bands and long emission lifetimes.1−3 Lanthanide coordination polymers with luminescent properties have been widely studied for applications as highly thermostable materials,4,5 thermo-sensors,6,7 ion-sensors,8 and electroluminescence materials.9 To achieve high emission quantum yields of lanthanide coordination polymers, enhancement of radiative transition probabilities and suppression of vibration relaxation should be required. Lanthanide coordination compounds with asymmetric geometrical structures promote radiative transition probabilities related to radiative rate constants (kr).10,11 Introduction of a low-vibrational frequency ligand in the lanthanide coordination site also leads to a decrease of nonradiative rate constants (knr).12 Strong luminescent Eu(III) coordination polymers composed of low-vibrational frequency hexafluoroacetylacetonato (hfa) and phosphine oxide ligands have been reported.13 Luminescent lanthanide coordination polymers with large kr and small knr are promising candidates in the field of optical material science. Structural transforming in lanthanide coordination polymers depending on their surrounding environments is expected to show unique physical properties for material science. Previously, we prepared the Eu(III) coordination polymer with a structural transformation system, [Eu(hfa)3(bipypo)]n (bipypo: 3,3-bis(diphenylphosphoryl)-2,2-bipyridine). [Eu(hfa)3(bipypo)]n transformed from a polymer structure to individual Eu(III) complexes in solution.14,15 The Eu(III) © 2017 American Chemical Society

coordination polymer in the solid state and that in solution exhibits characteristic triboluminescence and metal ion-sensing properties, respectively. In this study, we prepared a novel Eu(III) coordination polymer with a structural transforming that shows high thermal stability in the solid state and chiroptical properties such as circular dichroism (CD) and circularly polarized luminescence (CPL) in solution. The Eu(III) coordination polymer is connected to a chiral binaphthyl phosphinate ligand ((R)-bidp: (R)-1,1′-binaphthyl2,2′-bis(diphenylphosphinate)).16 The phosphinate parts in the chiral (R)-bidp ligand lead to sterical flexibility compared with the chiral ligand for a mononuclear Eu(III) complex, binapo (1,1′-binaphthyl-2,2′-bis(diphenylphosphine) oxide).17,18 The sterical flexibility of oxygen spacers in (R)-bidp gives effective coordination geometry for construction of polymer structure. Binaphthyl derivatives with oxygen spacers are known as a chiral joint ligands for metal coordination polymers composed of Ni, Zn, Pd, Ag, Cd, and Hg elements.19−24 On the basis of structural findings in those studies, we designed a novel chiral lanthanide coordination polymer with a structural transformation system, [Eu(hfa)3((R)-bidp)]n (Figure 1). The structural properties were characterized by singlecrystal X-ray and thermogravimetric analysis (TGA). The photophysical properties were estimated by the emission spectra, lifetimes, and quantum yields. We found that there was an effective transformation from a polymer to a monomer Received: February 8, 2017 Published: April 27, 2017 5741

DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747

Article

Inorganic Chemistry

Figure 1. Conceptual transformation of the Eu(III) coordination polymer with the chiral (R)-bidp ligand. 8.56 (br, 8H). 19F NMR (376 MHz, acetone-d6, δ, ppm): −80.1. IR (ATR) 1651, 1497, 1437, 1248, 1179, 1129, 1034, 816, 792, 749, 728, 691, 657 cm − 1 . ESI-Mass (m/z): [M−hfa] + calcd for C54H34EuF12O8P2, 1253.1; found, 1253.1. Anal. Calcd for: C, 48.54; H, 2.42. Found: C, 48.75; H, 2.79%. Optical Measurements. Emission spectra of novel Eu(III) compound were recorded on a Horiba/Jobin-Yvon Fluorolog-3 spectro-fluorometer and a JASCO CPL-300 spectro-fluoropolarimeter. Emission lifetimes (τobs) were recorded on the combination of the third harmonics (355 nm) of a Q-switched Nd:YAG laser (Spectra Physiscs, INDI-50, full width at half-maximum (fwhm) = 5 ns, λ = 1064 nm), a photomultiplier (Hamamatsu photonics, R5108, response time ≤1.1 ns), and a digital oscilloscope (Sony Tektronix, TDS3052, 500 MHz). Emission lifetimes were evaluated from the slope of exponential plots of the emission decay profiles. Fine grinding samples were used for measuring solid-state emission properties. Samples for measurements in solution were prepared under deoxygenated conditions. UV−vis absorption and CD spectra were recorded on a JASCO J-1500 spectro-polarimeter. A CPL spectrum was recorded on a JASCO CPL-300 spectro-fluoropolarimeter. Single-Crystal X-ray Structure Determinations. X-ray crystal structures and crystallographic data for (R)-bidp and [Eu(hfa)3((R)bidp)]n are shown in Figure 2, Figure 3, Figure S1, Table 1, and Table

structure in solution. The chiroptical properties in liquid media were also characterized using CD and CPL spectra. Structural and photophysical properties of the novel luminescent Eu(III) chiral coordination polymer with a structural transformation system were demonstrated.

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EXPERIMENTAL SECTION

General Methods. All chemicals were reagent-grade and used as received. [Eu(hfa)3(H2O)2] was prepared according to the literature.25 Infrared spectra were measured using a Shimadzu IRPrestige 21 FTIR8400S. Electrospray ionization (ESI) mass spectra were observed on a Thermo Scientific Exactive. Elemental analyses were performed using a J-Science Lab JM 10 Micro Corder. TGA was performed using a Seiko Instruments Inc. EXSTAR 6000 (TG-DTA 6300) at a heating rate of 5 °C min−1 with flowing argon gas. 1H NMR (400 MHz), 19F NMR (376 MHz), and 31P NMR (162 MHz) spectra were measured on a Bruker Avance HD 400 and JEOL ECX400. Preparation of ((R)-1,1′-Binaphthyl-2,2′-bis(diphenylphosphinate) ((R)-bidp). (R)-bidp was prepared according to the literature.16 Sodium hydride (60%, dispersion in paraffin liquid) (0.88 g, 22 mmol) was added to a solution of (R)-1,1′-bi-2naphthol (2.9 g, 10 mmol) in dry tetrahydrofuran (THF; 50 mL) at 0 °C. The mixture was stirred for 30 min at 0 °C, after which diphenylphosphinic chloride (5.3 g, 22 mmol) was added dropwise at 0 °C. After it was stirred for 3 h at room temperature, the solvent was concentrated to ca. 5 mL in vacuo. The resultant was extracted with dichloromethane (50 mL), washed with water (50 mL) three times, and dried with anhydrous Na2SO4. The extract was concentrated to ca. 10 mL and recrystallized from dichloromethane/diethyl ether (10 mL/ 90 mL). The clear crystals that formed were filtered off and dried in vacuo (6.3 g, 9.2 mmol, 92%). 1H NMR (400 MHz, CDCl3, δ, ppm): 6.99−7.38 (m, 26H), 7.89 (d, J = 8.1 Hz, 2H), 7.96 (d, J = 9.0 Hz, 2H), 8.07 (d, J = 9.0 Hz, 2H). 31P NMR (162 MHz, CDCl3, δ, ppm): 30.4 (s). Anal. Calcd for: C, 76.96; H, 4.70. Found: C, 76.75; H, 4.50%. Preparation of [Eu(hfa)3((R)-bidp)]n. (R)-bidp (0.43 g, 0.63 mmol) and [Eu(hfa)3(H2O)2] (0.51 g, 0.63 mmol) were dissolved in methanol (30 mL). The solution was refluxed while stirring for 3 h. The solvent was evaporated, and the obtained solid was dried in vacuo (0.74 g, 0.51 mmol, 81%). Crystals suitable for single-crystal X-ray analysis and thermophysical and photophysical measurements were obtained by diffusion of the methanol solution and cool methanol washing. 1H NMR (400 MHz, acetone-d6, δ, ppm): 4.51 (br, 3H), 7.05 (d, J = 8.2 Hz, 2H), 7.21 (dd, J = 8.2 and 7.6 Hz, 2H), 7.28 (dd, J = 7.6 and 7.8 Hz, 2H), 7.34 (d, J = 8.8 Hz, 2H), 7.61−7.64 (m, 8H), 7.72 (t, J = 7.2 Hz, 4H), 7.88 (d, J = 7.8 Hz, 2H), 7.92 (d, J = 8.8 Hz, 2H).

Figure 2. (a) A view of the right-handed helical polymer structure of [Eu(hfa)3((R)-bidp)]n. (b) A view of the 21 helical axis along the a axis of [Eu(hfa)3((R)-bidp)]n. 5742

DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747

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Inorganic Chemistry

bidp)]n were obtained by recrystallization from dichloromethane/diethyl ether solution and methanol solution, respectively. Their crystallographic data are summarized in Supporting Information, Table S1. The crystal structure of [Eu(hfa)3((R)-bidp)]n is shown in Figure 2. [Eu(hfa)3((R)bidp)]n shows a purely right-handed helical polymer structure with the chiral space group P212121. The helical polymer chains have 21 axes for all three dimensions and extend along 21 helices for the a axis. The coordination sites of [Eu(hfa)3((R)bidp)]n consist of three hfa ligands and two phosphinate ligands. Selected bond lengths and angles are summarized in Table 1. In this study, we regard hydrogen and fluorine atoms within 3 Å or less as having associative interactions.26 And hydrogen−π interactions are also observed within 2.9 Å, which is the sum of van der Waals radii of hydrogen and carbon atoms. We observed multiple intramolecular hydrogen− fluorine interactions in each of the monomer units shown in Figure 3: five hydrogen−fluorine interactions (red dotted lines) and two hydrogen−π interactions (blue dotted lines). Two intrachain hydrogen−fluorine interactions between monomer units (green dotted lines) were also found. These intrachain interactions promote fixation of the helical structure in crystals. Intermolecular hydrogen−fluorine interactions between two polymer chains were also observed (Table 1). The Eu···Eu distance in [Eu(hfa)3((R)-bidp)]n was determined to be 11.4 Å. This distance may be longer than the critical distance for nonradiative dipole−dipole energy transfer between Eu(III) ions.6 The dihedral angle for binaphthyl rings of the (R)-bidp ligand was found to be 64° (Supporting Information, Figure S1). The dihedral angle for binaphthyl rings of the coordination polymer [Eu(hfa)3((R)-bidp)]n was found to be 87°, which is larger than that of the (R)-bidp crystal. The nearly 90° dihedral angle in [Eu(hfa)3((R)-bidp)]n provides a 21 helical structure in the crystal. Generally, the coordination geometry of an eightcoordinated lanthanide complex exhibits a square antiprism structure (8-SAP) or trigonal dodecahedron structure (8TDH). On the basis of the crystal data, we calculated the continuous symmetry shape measures factor S to estimate the degree of distortion of the coordination structure in the first coordination sphere. The S value is given by

Figure 3. Perspective drawing (showing 50% probability displacement ellipsoids) for the monomer unit of [Eu(hfa)3((R)-bidp)]n focused on hydrogen−fluorine/π interactions.

Table 1. Structural Parameters of [Eu(hfa)3((R)-bidp)]n bond lengths (Å) Eu−O1 Eu−O2 Eu−O3 Eu−O4 Eu−O5 Eu−O6 Eu−O7 Eu−O8 Eu···Eue

2.369(7) 2.403(10) 2.373(9) 2.421(8) 2.344(8) 2.385(7) 2.356(8) 2.322(8) 11.448

atomic distance (Å) H20−F3a H21−F3a H43−F11a H42−F12a H43−F12a H39−Cent.1b H17−Cent.2b H57−F13c,e H57−F15c,e H38−F2d,f H19−F7d,f dihedral angle of binaphthyl ring (deg)

2.673 2.983 2.728 2.858 2.858 2.889 2.700 2.782 2.800 2.764 2.832 87

a Intramolecular hydrogen−fluorine interactions. bIntramolecular hydrogen−π interactions. cIntrachain hydrogen−fluorine interactions. d Intermolecular hydrogen−fluorine interactions. eAtoms in the same polymer chain. fAtoms in the different polymer chain.

N

S = min

S1. Single crystals for X-ray diffraction analysis were mounted on a MiTeGen micromesh with paraffin oil. X-ray diffraction measurements were performed on a Rigaku RAXIS RAPID imaging plate area detector with graphite monochromated Mo Kα radiation. Calculations were made using CrystalStructure version 4.1 (Rigaku Corporation) crystallographic software package. Corrections for decay and Lorentz polarization effects were made based on empirical absorption correction, solved by direct methods, and expanded using Fourier techniques. Non-hydrogen atoms and hydrogen atoms were refined using the anisotropic model and the riding model, respectively. The final cycle of full-matrix least-squares refinement was performed using detected reflections and variable parameters. The check CIF/ PLATON service was used for confirming the CIF data of this paper. Additional crystallographic information is available in the Supporting Information.

∑i = 1 |Q i − Pi|2 N

∑i = 1 |Q i − Q 0|2

× 100 (1)

where N, Qi, Q0, and Pi are the number of vertex atoms, position vectors of their atoms, position vectors of the geometrical center, and the position vectors of the corresponding vertex in the reference structure, respectively.27 The S value of [Eu(hfa)3((R)-bidp)]n for 8-SAP (point group D4d, S = 0.99) is smaller than that for 8-TDH (point group D2d, S = 1.15). The coordination geometry of [Eu(hfa)3((R)-bidp)]n was thus estimated to be an 8-SAP structure. TGA profiles for [Eu(hfa)3((R)-bidp)]n and mononuclear precursor [Eu(hfa)3(H2O)2] as a standard reference are shown in Figure 4. The decomposition temperature of [Eu(hfa)3((R)bidp)]n was found to be 320 °C, which is much higher than that of [Eu(hfa)3(H2O)2] (temperature of coordinated water elimination = 75 °C, decomposition temperature = 220 °C). The increase in the decomposition temperature of [Eu(hfa)3((R)-bidp)]n may be caused by the characteristic polymer structure. The polymer chains in the crystal are fixed by multiple hydrogen−fluorine/π interactions, three-dimension-

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RESULTS AND DISCUSSION Crystal Structure. The luminescent Eu(III) chiral coordination polymer [Eu(hfa)3((R)-bidp)]n was synthesized by reaction of the phosphinate ligand (R)-bidp with [Eu(hfa)3(H2O)2] in methanol at 65 °C (Supporting Information, Scheme S1). Single crystals of (R)-bidp and [Eu(hfa)3((R)5743

DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747

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Inorganic Chemistry

ment surrounding the lanthanide ions.28 We found that the emission spectral shape at ∼610 nm in acetone-d6 is much different from that in the solid state. The spectral shapes are based on their geometrical structure in the coordination site. This result indicates structural transformation of the coordination geometry in solution. From the photophysical findings, we consider that [Eu(hfa)3((R)-bidp)]n might be a transformed polymer to a monomer structure in solution. The transformation in liquid media is similar to that of previously reported [Eu(hfa)3(bipypo)]n.14,15 The time-resolved emission decay profiles of [Eu(hfa)3((R)bidp)]n in the solid state (black line) and in acetone-d6 (red line) are shown in Figure 5b. Single-exponential decays with millisecond-scale lifetimes were observed in both the solid state and in acetone-d6. The single exponential behavior in acetoned6 strongly supports existence of monomer structure as a single emissive component in solution. The emission lifetimes (τobs) were determined from the slope of exponential plots of the emission decay profiles. The emission lifetimes for [Eu(hfa)3((R)-bidp)]n in the solid state and in acetone-d6 were determined to be 0.69 and 0.94 ms, respectively. The 4f−4f emission quantum yields (Φf−f) and the radiative (kr) and nonradiative (knr) constants were estimated by using the following equations:

Figure 4. TGA profiles of [Eu(hfa)3((R)-bidp)]n (solid line) and [Eu(hfa)3(H2O)2] (dotted line) under an argon atmosphere.

ally. The tight packing structure in [Eu(hfa)3((R)-bidp)]n leads to enhancement of thermal stability at a high temperature. Photophysical Properties. The emission spectra for [Eu(hfa)3((R)-bidp)]n in the solid state (black line) and in acetone-d6 (red line) are shown in Figure 5a. In the solid state,

Φf − f =

τ kr = obs τrad k r + k nr

⎛I ⎞ 1 = AMD,0n3⎜ tot ⎟ τrad ⎝ IMD ⎠

kr = k nr =

1 τrad 1 1 − τobs τrad

(2)

(3)

(4)

(5)

where AMD,0, n, and Itot/IMD are the spontaneous emission probability for the 5D0−7F1 transition in vacuo (14.65 s−1), the refractive indexes (nsolid = 1.5 and nacetone‑d6 = 1.36, respectively29), and the ratio of the total area of the corrected Eu(III) emission spectrum to the area of the 5D0−7F1 band. These photophysical parameters in the solid state, in acetoned6, and in acetone are summarized in Table 2. The 4f−4f emission quantum yields of [Eu(hfa)3((R)-bidp)]n in the solid state, in acetone-d6, and in acetone were calculated to be 76%, 65%, and 55%, respectively. These emission quantum yields are much larger than those of the precursor [Eu(hfa)3(H2O)2] (Φf−f, solid = 19%, Φf−f, acetone‑d6 = 11%).30,31 The difference of the value of kr is mainly originated from the difference of refractive indexes of solid and solution. We found that knr values of [Eu(hfa)3((R)-bidp)]n in the solid state and in acetone-d6 are similar, and knr value of [Eu(hfa)3((R)-bidp)]n in acetone is larger than those of [Eu(hfa)3((R)-bidp)]n in the solid state and in acetone-d 6 . The tight packing structure based on intermolecular hydrogen−fluorine/π interactions in the solid state and low vibration property of deuterium in acetone-d6 promote suppression of vibrational relaxation.32 Chiroptical Properties. The UV−vis absorption and CD spectra of [Eu(hfa)3((R)-bidp)]n (black lines) and (R)-bidp ligand (orange lines) in methanol are shown in Figure 6a,b, respectively. The CD spectra band of (R)-bidp ligand at 327 nm is assigned to the π−π* transition of the binaphthyl

Figure 5. (a) Emission spectra excited at 380 nm and (b) decay profiles excited at 355 nm of [Eu(hfa)3((R)-bidp)]n in the solid state (black) and in 1.0 × 10−3 M acetone-d6 solution (red).

emission bands are observed at ∼578, 592, 611, 651, and 699 nm and are attributed to the f−f transitions of Eu(III) (5D0−7FJ: J = 0, 1, 2, 3, and 4, respectively). Generally, thermostable lanthanide coordination polymers are insoluble in water and organic solvents. The Eu(III) chiral coordination polymer [Eu(hfa)3((R)-bidp)]n exhibits high solubility in various organic solvents such as methanol and acetone. The emission spectra for [Eu(hfa)3((R)-bidp)]n in the solid state and acetone-d6 as shown in Figure 5a are normalized with respect to the magnetic dipole transition intensity at 592 nm (5D0−7F1), which is known to be insensitive to the environ5744

DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747

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Inorganic Chemistry Table 2. Photophysical Properties of Eu(III) Compounds Tda (°C) [Eu(hfa)3(H2O)2]

220

[Eu(hfa)3((R)-bidp)]n

320

state

τobs (ms)

b

solid solutionc solidd solutione solutionf

0.22 0.40 0.69 0.94 0.76

Φf−f (%)

kr (s−1)

19 11 76 65 55

× × × × ×

8.8 2.8 1.1 6.9 7.2

knr (s−1) 2

10 102 103 102 102

3.7 2.2 3.5 3.7 6.0

× × × × ×

103 103 102 102 102

Td means decomposition temperature. bRef 30. cRef 31. 5.0 × 10−2 M acetone-d6 solution. The knr was calculated using eq 2. dThe τobs of the Eu(III) complexes were measured by excitation at 355 nm (Nd:YAG 3ω). The Φf−f, kr, and knr were calculated using eqs 2−5. e1.0 × 10−3 M acetone-d6 solution. f1.0 × 10−3 M acetone solution. The τobs of the Eu(III) complexes were measured by excitation at 355 nm (Nd:YAG 3ω). The Φf−f, kr and knr were calculated using eqs 2−5. a

where IL and IR are the left and right circularly polarized emission intensities, respectively. In general, gCPL values at the magnetic-dipole transition are notably larger than those at the electric-dipole transition in Eu(III) compounds. The gCPL values at the magnetic-dipole and the electric-dipole transitions of [Eu(hfa)3((R)-bidp)]n were estimated to be 0.0133 and −0.0009, respectively. The gCPL value at the magnetic-dipole transition is close to that of previously reported [Eu(hfa)3(binapo)] (gCPL = 0.03).18 We propose that the [Eu(hfa)3((R)-bidp)]n polymer should be monomerized in liquid media, resulting in the formation of a chiral monomeric Eu(III) complex such as [Eu(hfa)3(binapo)].

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CONCLUSION

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ASSOCIATED CONTENT

We investigated a Eu(III) chiral coordination polymer, [Eu(hfa)3((R)-bidp)]n, with a structural transformation system. The Eu(III) coordination polymer has a helical polymer structure with characteristic hydrogen−fluorine/π interactions in the crystal, which shows high thermostability (decomposition temperature = 320 °C) and strong luminescence properties (Φf−f = 76%) in the solid state. We also found transformation of the emission spectrum of [Eu(hfa)3((R)bidp)]n in solution. The results of a photophysical study suggested that the coordination polymer is transformed to individual complexes in solution. The individual complexes in liquid media show chiroptical properties under their chiral coordination environment. A lanthanide compound with a structural transformation system has multifunctional properties. Such a lanthanide coordination polymer with a structural transformation system is expected to open a frontier field of coordination chemistry and materials science.

Figure 6. (a) UV−vis absorption and (b) CD spectra of 2.0 × 10−5 M; [Eu(hfa)3((R)-bidp)]n (black line), 1.0 × 10−4 M; (R)-bidp (orange line); in methanol. (c) Emission and (d) CPL spectra of [Eu(hfa)3((R)-bidp)]n in 8.4 × 10−4 M acetone excited at 355 nm.

group.33 The π−π* chiral transition band was broadened by complexation of (R)-bidp with Eu(III) ion. The transition in the CD spectrum of [Eu(hfa)3((R)-bidp)]n showed the positive sign, which indicates that exciton coupling does not occur.34 The result is consistent with the interpretation of the monomeric state of the Eu(III) complex in solution. The emission and CPL spectra of [Eu(hfa)3((R)-bidp)]n in acetone excited at 355 nm are shown in Figure 6c,d, respectively. The CPL signals are given by the difference between the left and right circularly polarized emission intensities (ICPL = IL − IR). Effective CPL signals were observed at ∼595 and 614 nm, based on 5D0−7F1 and 5D0−7F2 transitions, respectively. The degree of CPL signals is usually evaluated by the luminescent dissymmetry factor gCPL, which is defined as follows: I − IR gCPL = 1 L (I + IR ) (6) 2 L

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b00337. Synthetic schemes of (R)-bidp and [Eu(hfa)3((R)bidp)]n; crystallographic data for (R)-bidp and [Eu(hfa)3((R)-bidp)]n; crystal structures of (R)-bidp; DOSY−NMR measurement; CD measurement; preparation of [Tb(hfa)3((R)-bidp)]n (PDF) X-ray crystallographic data of (R)-bidp and [Eu(hfa)3((R)-bidp)]n (CIF) X-ray crystallographic data (CIF) 5745

DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747

Article

Inorganic Chemistry

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AUTHOR INFORMATION

Corresponding Author

*Phone/Fax: +81 11 706 7114. E-mail: hasegaway@eng. hokudai.ac.jp. ORCID

Naoyuki Koiso: 0000-0001-8513-3408 Yasuchika Hasegawa: 0000-0002-6622-8011 Notes

The authors declare no competing financial interest. The Cambridge Crystallographic Data Centre (www.ccdc.cam. ac.uk/data_request/cif) provides the supplementary crystallographic data for (R)-bidp (CCDC-1503315) and [Eu(hfa)3((R)-bidp)]n (CCDC-1503316). The continuous symmetry shape measures factor S was calculated using SHAPE version 2.1, which can be obtained from http://www.ee.ub. edu/.

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ACKNOWLEDGMENTS We are particularly grateful for experimental assistance by Prof. H. Ito and Asst. Prof. T. Seki of Hokkaido Univ. We appreciate the support of JASCO Corporation for the CPL measurement.

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REFERENCES

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DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747

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DOI: 10.1021/acs.inorgchem.7b00337 Inorg. Chem. 2017, 56, 5741−5747