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Slow magnetic relaxation in a Tb(III)-based coordination polymer

DaltonTransactions

Volume 47 Number 45 7 December 2018 Pages 15997–16360

A one-dimensional Tb-based coordination polymer (polyTb) was
synthesized, which showed ﬁeld-induced magnetic relaxation insolid and solution state as well as green luminescence due to f–ftransition.

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Slow magnetic relaxation in a Tb(III)-based
coordination polymer†
Takefumi Yoshida,
Masayoshi HiguchiaYemineni S. L. V. Narayana,a Hitoshi Abe
*a

b,c

and

A Tb(III)-based coordination polymer ( polyTb) was synthesized by complexation of Tb(NO3)3·(6H2O) and
4’,4’’’’-[1,1’-biphenyl]-4,4’-diylbis[6,6’’-bis(ethoxycarbonyl)2’:6’,2’’-terpyridine](L). The polymer structure
was determined by Job’s plots, DFT calculation, and X-ray absorption ﬁne structure (XAFS) measurement.
Job’s plots indicated that the mole ratio (Tb ion : L) is 1 : 1. The optimized model structures suggested a La
model: the LaN6⋯(OvC)2 model. The bond distances of La–O and La–N are ∼2.80 Å and 2.60 Å,
Received 31st July 2018,
Accepted 18th September 2018
DOI: 10.1039/c8dt03125h
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respectively. The EXAFS ﬁtting indicated that the bond distances of Tb–O and Tb–N are 2.65 Å and2.95 Å, respectively. polyTb shows ﬁeld-induced magnetic relaxation in the solid and solution state. The
luminescence of polyTb, originating from an f–f transition, was observed (ϕ = 6.9%). polyTb formed aporous structure on a Si substrate, whereas a ﬁbrous complex structure was formed on glass. polyTb
chains are orientated on glass, which were determined by XRD.

Introduction
Coordination polymers (CPs) have received much attention
due to their luminescence,1 electrochromism,1c,2 and ion conductivity.3 These properties greatly depend on the metal
species included in the polymer. The zinc and lanthanoid
polymers present good light emission properties. HoltenAndersen reported white-light-emitting lanthanoid metallogels
with switching properties.1d Luminescent CPs will realize practical probes and sensors.
As for the magnetic properties, Kurth reported spincrossover phenomena.4a Murray reported light induced excitedspin state trapping.4b A molecular magnet is one of the prime
candidates for quantum memory since it can store information on spin such as up spin and down spin. Organic
π-conjugated polymers with radicals show slow magnetic
relaxation owing to magnetic ordering.5 Although thereported polymer shows a larger magnetic moment, it isdiﬃcult to store the information on an independent spin
centre because of an isotropic π-orbital. Since lanthanoidaElectronic Functional Macromolecules Group, National Institute for Materials
Science (NIMS), Tsukuba 305-0044, Japan. E-mail: HIGUCHI.Masayoshi@nims.go.jpbInstitute of Materials Structure Science High Energy Accelerator Research
Organization (KEK) 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japanc
Department of Materials Structure Science, School of High Energy Accelerator
Science, SOKENDAI (the Graduate University for Advanced Studies) 1-1 Oho,
Tsukuba, Ibaraki 305-0801, Japan† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c8dt03125h

16066 | Dalton Trans., 2018, 47, 16066–16071(Ln) ions have strong intrinsic magnetic anisotropy and large
activation barriers (Δ) between up-spins and down-spins, as aresult of spin–orbital interaction, the complexes will act as
molecular magnets.6 There are several lanthanoid compounds with a 1D chain structure, but they have high crystallinity and cannot be treated like soft materials.6e–f Molecularorientation is one of the important factors for making molecular-based optical devices or memory, because there isorientation dependence for properties that arise from molecular polarization or magnetic anisotropy. Successful
research on molecular-based quantum devices has beenreported, where the molecule attaches onto a surface byvacuum deposition or Langmuir–Blodgett film formation.7
On the other hand, molecular-based bulk devices have beenreported, where the molecule attaches onto the surface bysimple coating.8 CPs have good film forming abilities andcan form composites of polyTb and other polymers.9 This
will extend the application of the CPs as molecular magnets
and/or luminescent sensors. We synthesized a Tb(III)-basecoordination polymer ( polyTb) using a terpyridine ligand(L: 4′,4′′′′-[1,1′-biphenyl]-4,4′-diylbis[6,6″-bis(ethoxycarbonyl)
2′:6′,2″-terpyridine], Fig. 1a) to reveal the expansivity of magnetic materials.

Results and discussion
First, we investigated the complexation behavior of Tb ionsand L by Job’s plots. A Job’s plot at 340 nm is shown in
Fig. 1b. The intensity at 340 nm gradually increases, when theThis journal is © The Royal Society of Chemistry 2018

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Andreiadis reported the synthesis of a similar Eu complex of
discrete small molecules by simple mixing of the metal salt
and ligand in a solvent.10 To L (9 mg, 0.01 mmol) was added
Tb(NO3)3·6H2O (4 mg, 0.01 mmol) in 20 ml CH2Cl2 solution.
After several hours, a yellow solution of polyTb was obtained.
After evaporation, we obtained a yellow solid of polyTb. polyTb
was characterized by elemental analysis and IR spectra. The
UV/vis spectra of polyTb and L are shown in Fig. 1c. There are
π–π* transition peaks of L at 250 nm 300 nm. There is a clear
metal-to-ligand charge transition (MLCT) or ligand-to-metal
charge transition (LNCT) peak of polyTb at 340 nm.
To estimate the coordination structure of polyTb, we madea La model: the LaN6⋯(OvC)2 model instead of a Tb model(to avoid errors of calculation induced by multiple f 8 spins)
and optimized the structures (Fig. 3). The optimized coordination structure of each model is shown in Fig. S1† (coordinates in Table S1†). The La ions have D4h.11 The bond distances of La–O and La–N are ∼2.80 Å and 2.60 Å, respectively.
These distances are similar to the reported coordination structure of the Eu complex with the terpyridine ligand which is ananalogue of L, where there are an Eu–O bond (∼2.44 Å) and an
Eu–N bond (∼2.68 Å).10 Therefore, these models are appropriate for determining the coordination structure of polyTb. In
addition, the intramolecular La–La distance was estimated tobe more than 22 Å and the shortest intermolecular La–La distance was at least 11 Å (diameter of the ligand). Therefore, we
concluded that there is no magnetic ordering among the Tb
ions of polyTb due to long Tb–Tb distances.
For further evidence, we performed X-ray absorption finestructure measurements at the L3-edge of the Tb ion at the
Synchrotron Facility (BL-9A KEK). X-ray absorption near edge
structures (XANES) at the Tb L3-edge are shown in Fig. 4. The

Fig. 1 (a) A structure of L; (b) Job’s plots for the complexation ofTb(NO3)3 and L at 350 nm; (c) UV/vis spectrum of L and polyTb.

amount of Tb ion is increased up to 0.5. Then the intensity
gradually decreases up to 1. These results indicated that themole ratio is 1 : 1, or they formed a 1D chain structure (Fig. 2).
According to the results of Job’s plots, we synthesized
polyTb by 1 : 1 complexation of Tb(NO3)3·(6H2O) and L. We
described the synthesis of L in the Experimental section.

Fig. 2

An expected structure of polyTb.

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Fig. 3 The optimized structures of the La model. The ethoxycarbonylgroups were replaced with methoxycarbonyl groups for simplifying the
calculation. Hydrogen atoms are omitted for clarity.

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Fig. 4

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XANES of Tb2O3 and polyTb.

Tb L3-edge spectra of 1 was not shifted from 7519 eV ( peak topof the edge of the standard sample of Tb2O3). The results indicate that the oxidation state of Tb ions of 1 is trivalent.12 From
the EXAFS region, the fitting revealed that the coordinationbond lengths around the Tb ions (Tb–O, Tb–N) are 2.67 Å and2.84 Å (R-factor; 1.5%, Table 1, EXAFS oscillation is shown in
Fig. S2†). Both results relatively match to each model.
The χT vs. T plots for polyTb are shown in Fig. 5a (χ: magnetic susceptibility). The χT value for polyTb was constant at
10.5 cm3 mol−1 K in the range of 100–300 K, consistent withthe expected value for an uncoupled Tb ion (11.82 cm3 mol−1K). The values decreased with a decrease in temperature in therange of 10–100 K. These decrements were attributed to thedepopulation of the mJ state of the Tb ion, and not to magnetic
ordering. The reduced magnetization plots for polyTb almost
overlapped each other, indicating that the magnetic anisotropyof polyTb is small (Fig. 5a inset). The magnetization vs. fieldplots for polyTb are shown in Fig. S3.† No hysteresis wasobserved.
No clear frequency dependence in zero dc field wasobserved for polyTb, because of a fast quantum tunnelingrelaxation process. However as soon as a dc field was applied,
polyTb shows a clear frequency dependency of magnetic relaxation or slow magnetic relaxation, in which quantum tunneling is suppressed (Fig. 5b and S5†). Only a single relaxation
time (τ) was obtained from the magnetic data acquired in a
3000 Oe field (although the τ values increase or the QTM is
gradually suppressed up to 4000 Oe (Fig. S4†), we acquired thedata using an applied field of 3000 Oe because of the
maximum χ″ and symmetric relaxation curve) in the temperature range 2–4 K. Each relaxation was fitted using the Cole–

Table 1

Tb–O
Tb–N

Fitting results for Tb–O and Tb–N distances from EXAFS

N

R (Å)

σ2 (Å2)E0 (eV)

4
6

2.83
2.67

0.025
0.012

−8.03
−8.03

N: coordination number, R: radius.

16068 | Dalton Trans., 2018, 47, 16066–16071

Fig. 5 (a) χT vs. T plots for polyTb measured under a ﬁeld of 3000 Oe
in the T range of 10–300 K. Inset: reduced magnetization of polyTb atvarious temperatures. (b) χ’’ vs. T plots for polyTb under a ﬁeld of 3000
Oe in the T range of 2–4 K.

Cole model.13 All τ values are almost constant up to 4 K, a
direct process (τ̄−1 = AH4T ) or the Orbach process (τ̄ 1 = exp(−Δ/kBT )) with a small Δ being dominant (Fig. S6†).
Upon further investigation, we found that polyTb showsmagnetic relaxation in the isolated state for making composites of polyTb and other polymers. We measured the AC susceptibility of a 1 mM CH2Cl2 solution of polyTb. There is magnetic relaxation which is faster than that in the solid-state(Fig. S7†). This is properly attributed to the coordination geometry change around the Tb ion that arises from the absenceof stacking among the polymers, where the coordination
environment around the Tb ion is less distorted. However,there is potential for composites of polyTb and other polymers
showing magnetic properties under diluted conditions.
At room temperature (RT), upon excitation at 300 nm
assigned to the π–π* transition of polyTb, the characteristic
luminescence of the 5D4 → 7Fn f–f transitions (n = 6, 5, 4, 3) of
Tb ions was observed at 490, 542, 584, and 623 nm (Fig. 6). In
addition, at 77 K, the characteristic luminescence of the f–ftransitions of Tb ions was observed at 493, 543, 583, and621 nm. The quantum yield of the region between 450 and
650 nm is 6.9% for the Tb f–f transition at RT. This low
quantum yield is probably because of the high symmetry of
the coordination sphere in the solution.14 The excitation
spectra of polyTb probed at 640 nm are shown in Fig. S8.† A

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degrees are enhanced, whereas other peaks became weaker.
These results indicated that polyTb formed random orientation on the Si substrate like powder and preferred orientation on the glass substrate. Although we couldn’t index eachpeak because of low crystallinities, we expected that polymer
chains along with the glass substrate, where peaks are correlated to inter-chain and/or inter-chain Tb–Tb distances, areenhanced. From the results of SEM and XRD, the polymer
chains of polyTb properly formed an orientated fibrous structure along with the glass substrate by drop-casting. This isproperly because polymer chains have a high aﬃnity to glass.
These properties enable the easy formation of polarized luminescence7c and orientated magnetic devices.7a,b,8Fig. 6 Emission spectra of polyTb at RT and 77 K in CHCl3 solution.
Quantum yield was calculated as 6.9% at RT.

Conclusions
broad band with a peak at 300 nm was observed, where theshape of the edge is similar to that of the absorption spectraof polyTb in the range of 340–400 nm (corresponding to MLCTor LMCT: CT). This result indicated that the intra-molecularenergy transfer terminated at the 1CT band during irradiation.
Then, energy transfer occurs in 1CT → 3T1 → 5D4.
To investigate the film-forming properties of polyTb, wemeasured the morphology of polyTb on the surface by scanning electron microscopy (SEM), where we prepared a film bydrop-casting. The SEM images of polyTb on Si and glass areshown in Fig. 7. polyTb formed a porous structure (diameter ofthe particle is about several 10 μm) on a Si substrate, whereasa fibrous complex structure (diameter of fibres is about severalμm) was formed on glass. To investigate the diﬀerence of eachsurface, we performed X-ray diﬀraction (Fig. S9†). There arecharacteristic diﬀraction patterns, similar to the patterns of
the powder sample, at 11.9, 12.5, 13.4, 15.8, 16.8 and 17.6
degrees on the Si substrate. There are also characteristic diﬀraction patterns at 11.9, 12.5, 13.4, 15.8, 16.8 and 17.6 degrees
on the glass substrate. However, the peaks at 13.4 and 17.6

Among Tb-based CPs, polyTb was synthesized by complexation of Tb(NO3)3·(6H2O) and L. The coordination structure(TbN6O4) is determined by Job’s plots, DFT calculation, and
X-ray absorption fine structure measurement; a 1D chain
coordination polymer is formed. polyTb shows field-induced
magnetic relaxation in the solid and solution state. The
luminescence of polyTb, originating from an f–f transition,
was observed ( f = 6.9%). The coordination structure aroundLn ions is the dominant factor for both magnetism andluminescence. However, it is hard to obtain information
about the structure due to low crystallinity. In this work, weestimated the structure of CPs by DFT calculation and XAFS
measurement. It is an eﬀective method for designing highperformance CPs which are molecular magnets. In addition,
polyTb formed a porous structure on the Si substrate,
whereas a fibrous complex structure was formed on glass.
The polyTb film is orientated on glass, determined by XRD.
In conclusion, we synthesized materials which show slow
magnetic relaxation and orientation on the surface. These
properties will simplify the fabrication of optical and magnetic devices.

Experimental
Synthesis of polyTb

Fig. 7SEM image of polyTb on (a,b) glass, (c) Si and (d) powder.

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To 40 mL of a DMSO solution of diethyl 4′-(4-bromophenyl)[2,2′:6′,2″-terpyridine]-6,6″-dicarboxylate (0.30 g, 0.56 mmol)
were added bis( pinacolato)diboron (0.157 g, 0.62 mmol),
K2CO3 (0.39 g, 2.81 mmol), and PdCl2(PPh3)2 (0.035 g,
0.56 mmol). The resultant reaction mixture was stirred at
100 °C under a nitrogen atmosphere for 12 h. After completionof the reaction, the solvent was removed under reducedpressure at 100 °C. The reaction mixture was cooled to room
temperature and CHCl3 (50 mL) was added. The catalyst wasremoved by filtration and washed thoroughly with CHCl3. The
filtrate was then washed with H2O. The separated organic layer
was dried over Na2SO4, filtered, concentrated, and purified bycolumn chromatography on silica gel (CHCl3/n-hexane =Dalton Trans., 2018, 47, 16066–16071 | 16069

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90 : 10, then pure CHCl3), and then finally purified by HPLC
(CHCl3) aﬀording the desired product (L) (0.17 g, 33%) as awhite solid. 1H NMR (300 MHz, CHCl3, 298 K) 8.94 (s, 4H),
8.88 (d, 4H), 8.18 (d, 4H), 8.04 (m, 8H), 7.90 (s, 4H), 4.51 (q,8H), 1.49 (t, 12H), HR-MS: found m/z: 927.32 [M + Na];C54H44N6O8 [M] requires 904.32. To L (9 mg, 0.01 mmol) was
added Tb(NO3)3·6H2O (4 mg, 0.01 mmol) in 20 ml CH2Cl2
solution. After several hours, a yellow solution of polyTb was
obtained. After evaporation, we obtained a yellow solid of
polyTb. Elemental analysis: Found: C, 45.49; H, 4.00; N, 9.07
Calc. for [TbL](NO3)3·(6H2O + CH2Cl2) = C55H58N9O23Cl2Tb: C,
45.78; H, 4.05; N, 8.74%. IR spectrum (KBr, cm−1): 3051 (m),2999 (m), 1604 (s), 1628 (s), 1587 (s), 1567 (m), 1540 (m), 1469(m), 1395 (s), 798 (m), 725 (m).
Calculation
Structural optimizations were performed on the Gaussian16
program package.15 The molecular structure was determinedusing the model made by Avogadro.16 The B3LYP17 functional
was used with the LanL2DZ basis set including the eﬀective
core potential.18 The SCF procedure was performed under very
strict conditions. An ultrafine integration grid was used for
integration. Publication materials were visualized by
Avogadro.16
XAFS measurement
X-ray absorption fine structure (XAFS) measurements werecarried out at the BL9A beamline of the Photon Factory, theHigh Energy Accelerator Research Organization (KEK), under
the proposal no. 2017PF-04. Structural analysis was performedon the Demeter software platform.19 We used the optimized
structure and reported crystal data10 for calculating Feﬀ.
Spectroscopy
UV-vis spectra were acquired on a SHIMADZU UV-2550 UVvisible spectrophotometer. FT-IR spectra were acquired on a
FTIR-8400S infrared spectrophotometer. Emission and excitation spectra were acquired in CHCl3 solution on a
SHIMADZU RF-5300PC spectrofluorophotometer with Oxford
OptistatDN cryostats. The absolute emission quantum yields
and emission lifetimes were measured on a Hamamatsu
Photonics K. K. absolute PL quantum yield spectrometer 992002G.
Magnetometry
DC and AC magnetic susceptibility measurements were performed on a solid polycrystalline sample on a Quantum
Design MPMS SQUID magnetometer under an applied dc fieldof 3000 Oe.

Conﬂicts of interest
There are no conflicts to declare.

16070 | Dalton Trans., 2018, 47, 16066–16071

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Acknowledgements
This research is financially supported by the JST-CREST
project (grant number: JPMJCR1533). This work was conducted at the AIST Nano-Processing Facility, supported by the“Nanotechnology Platform Program” of the Ministry of
Education, Culture, Sports, Science and Technology (MEXT),
Japan. The calculations in this study were performed on a
Numerical Materials Simulator at NIMS. XAFS measurements
were performed under the approval of PF-PAC No. 2017PF-04.

Notes and references
1 (a) D. Yang, Y. Wang, D. Liu, Z. Li and H. Li, J. Mater.
Chem. C, 2018, 6, 1944–1950; (b) R. Aoki, R. Toyoda,
J. F. Kögel, R. Sakamoto, J. Kumar, Y. Kitagawa, K. Harano,
T. Kawai and H. Nishihara, J. Am. Chem. Soc., 2017, 139,
16024–16027; (c) S. Pai, M. Moos, M. H. Schreck,
C. Lambert and D. G. Kurth, Inorg. Chem., 2017, 56, 1418–
1432; (d) P. Chen, Q. Li, S. Grindy and N. Holten-Andersen,
J. Am. Chem. Soc., 2015, 137, 11590–11593; (e) R. Dobrawa
and F. Würthner, Chem. Commun., 2002, 1878–1879, DOI:
10.1039/B205478G; (f ) S. C. Yu, C. C. Kwok, W. K. Chanand C. M. Che, Adv. Mater., 2003, 15, 1643–1647.
2 (a) S. Pai, M. Moos, M. H. Schreck, C. Lambert and
D. G. Kurth, Inorg. Chem., 2017, 56, 1418–1432;(b) C. Chakraborty, R. K. Pandey, U. Rana, M. Kanao,
S. Moriyama and M. Higuchi, J. Mater. Chem. C, 2016, 4,
9428–9437.
3 R. K. Pandey, U. Rana, C. Chakraborty, S. Moriyama and
M. Higuchi, ACS Appl. Mater. Interfaces, 2016, 8, 13526–
13531.
4 (a) Y. Bodenthin, G. Schwarz, Z. Tomkowicz, T. Geue,
W. Haase, U. Pietsch and D. G. Kurth, J. Am. Chem. Soc.,
2009, 131, 2934–2941; (b) T. M. Ross, B. Moubaraki,
D. R. Turner, G. J. Halder, G. Chastanet, S. M. Neville,
J. D. Cashion, J. F. Létard, S. R. Batten and K. S. Murray,
Eur. J. Inorg. Chem., 2011, 2011, 1395–1417.
5 (a) A. Rajca, J. Wongsriratanakul and S. Rajca, Science,
2001, 294, 1503–1505; (b) N. A. Zaidi, S. R. Giblin, I. Terryand A. P. Monkman, Polymer, 2004, 45, 5683–5689.
6 (a) T. P. Latendresse, V. Vieru, B. O. Wilkins,
N. S. Bhuvanesh, L. F. Chibotaru and M. Nippe, Angew.
Chem., Int. Ed., 2018, 57, 8164–8169; (b) M. Perfetti,
M. A. Sørensen, U. B. Hansen, H. Bamberger, S. Lenz,
P. P. Hallmen, T. Fennell, G. G. Simeoni, A. Arauzo,
J. Bartolomé, E. Bartolomé, K. Lefmann, H. Weihe,
J. Slageren and J. Bendix, Adv. Funct. Mater., 2018, 1801846;(c) K. Katoh, S. Yamashita, N. Yasuda, Y. Kitagawa,
B. K. Breedlove, Y. Nakazawa and M. Yamashita, Angew.
Chem., Int. Ed., 2018, 57, 9262–9267; (d) J. Goura,
E. Colacio, J. M. Herrera, E. A. Suturina, I. Kuprov, Y. Lan,
W. Wernsdorfer and V. Chandrasekhar, Chem. – Eur. J.,
2017, 23, 16621–16636; (e) E. Bartolomé, J. Bartolomé,
A. Arauzo, J. Luzón, R. Cases, S. Fuertes, V. Sicilia,

This journal is © The Royal Society of Chemistry 2018

View Article Online

Open Access Article. Published on 18 September 2018. Downloaded on 9/27/2024 9:01:09 AM.
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A. I. Sánchez-Cano, J. Aporta, S. Melnic, D. Prodius andS. Shova, J. Mater. Chem. C, 2018, 6, 5286–5299;(f ) H.-L. Tsai, C.-I. Yang, W. Wernsdorfer, S.-H. Huang,
S.-Y. Jhan, M.-H. Liu and G.-H. Lee, Inorg. Chem., 2012, 51,
13171–13180.
7 (a) H. Imada, K. Miwa, M. Imai-Imada, S. Kawahara,
K. Kimura and Y. Kim, Phys. Rev. Lett., 2017, 119, 013901;(b) E. Moreno Pineda, T. Komeda, K. Katoh, M. Yamashita
and M. Ruben, Dalton Trans., 2016, 45, 18417–18433;(c) M. Hasegawa, S. Kunisaki, H. Ohtsu and F. Werner,
Monatsh. Chem., 2009, 140, 751–763.
8 I. Osaka, M. Saito, T. Koganezawa and K. Takimiya, Adv.
Mater., 2014, 26, 331–338.
9 (a) D. G. Kurth, J. Pitarch López and W.-F. Dong, Chem.
Commun., 2005, 2119–2121; (b) D. G. Kurth, F. Caruso and
C. Schüler, Chem. Commun., 1999, 1579–1580.
10 E. S. Andreiadis, R. Demadrille, D. Imbert, J. Pécaut and
M. Mazzanti, Chem. – Eur. J., 2009, 15, 9458–9476.
11 (a) S. Alvarez, P. Alemany, D. Casanova, J. Cirera, M. Llunelland D. Avnir, Coord. Chem. Rev., 2005, 249, 1693–1708;(b) A. Ruiz-Martínez, D. Casanova and S. Alvarez, Chem. –Eur. J., 2008, 14, 1291–1303.
12 A. Potdevin, G. Chadeyron, V. Briois, F. Leroux and
R. Mahiou, Dalton Trans., 2010, 39, 8718–8724.
13 K. S. Cole and H. Robert, J. Chem. Phys., 1941, 9, 341.
14 Y. Hasegawa, M. Yamamuro, Y. Wada, N. Kanehisa, Y. Kai
and S. Yanagida, J. Phys. Chem. A, 2003, 107, 1697–1702.
15 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,

This journal is © The Royal Society of Chemistry 2018

Paper

G. A. Petersson, H. Nakatsuji, X. Li, M. Caricato,A. V. Marenich, J. Bloino, B. G. Janesko, R. Gomperts,
B. Mennucci, H. P. Hratchian, J. V. Ortiz, A. F. Izmaylov,
J. L. Sonnenberg, D. Williams-Young, F. Ding, F. Lipparini,
F. Egidi, J. Goings, B. Peng, A. Petrone, T. Henderson,
D. Ranasinghe, V. G. Zakrzewski, J. Gao, N. Rega, G. Zheng,
W. Liang, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, K. Throssell, J. A. Montgomery Jr.,J. E. Peralta, F. Ogliaro, M. J. Bearpark, J. J. Heyd,
E. N. Brothers, K. N. Kudin, V. N. Staroverov, T. A. Keith,
R. Kobayashi, J. Normand, K. Raghavachari, A. P. Rendell,J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi,
J. M. Millam, M. Klene, C. Adamo, R. Cammi,
J. W. Ochterski, R. L. Martin, K. Morokuma, O. Farkas,
J. B. Foresman and D. J. Fox, Gaussian16 (Revision B.01),
Gaussian, Inc., Wallingford CT, 2016.
16 M. D. Hanwell, D. E. Curtis, D. C. Lonie,
T. Vandermeersch, E. Zurek and G. R. Hutchison,J. Cheminf., 2012, 4, 17.
17 (a) A. D. Becke, J. Chem. Phys., 1993, 98, 5648–5652;(b) C. Lee, W. Yang and R. G. Parr, Phys. Rev. B: Condens.
Matter Mater. Phys., 1988, 37, 785–789.
18 (a) T. H. Dunning Jr. and P. J. Hay, Modern Theoretical
Chemistry, ed. H. F. Schaefer III, Plenum, New York, Vol. 3,
1977; (b) P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82,
270–283.
19 B. Ravel and M. Newville, J. Synchrotron Radiat., 2005, 12,
537–541.

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