Three-dimensional lanthanide frameworks constructed of two-dimensional squares strung on one-dimensional double chains: Syntheses, structures, and luminescent properties

Inorganica Chimica Acta 484 (2019) 13–18

Contents lists available at ScienceDirect

Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica

Research paper

Three-dimensional lanthanide frameworks constructed of two-dimensional squares strung on one-dimensional double chains: Syntheses, structures, and luminescent properties

T

⁎

Zhen-Tao Li, Zhi-Qin Wang, Qing-Yan Liu, Yu-Ling Wang

College of Chemistry and Chemical Engineering and Key Laboratory of Functional Small Organic Molecule of Ministry of Education, Jiangxi Normal University, Nanchang, Jiangxi 330022, PR China

A R T I C LE I N FO

A B S T R A C T

Keywords: 1D lanthanide-biphenyl-3,3′-disulfonyl-4,4′dicarboxylate chain 2D lanthanide-1,4-benzenedicarboxylate square Lanthanide luminescence Crystal structures

Two coordination polymers, {[Ln2(BPDSDC)(BDC)(H2O)6]·4H2O}n (Ln = Tb(1) and Eu(2)), constructed from biphenyl-3,3′-disulfonyl-4,4′-dicarboxylate (BPDSDC4–) and 1,4-benzenedicarboxylate (BDC2–) ligands were synthesized and structurally characterized. The solid state structure of {[Ln2(BPDSDC)(BDC)(H2O)6]·4H2O}n consists of one-dimensional (1D) Ln-BPDSDC double chains and two-dimensional (2D) Ln-BDC squares featuring the Ln2(COO)4 paddle-wheel units and the nanosized grids. Each grid of the 2D squares is threaded by a 1D LnBPDSDC double chain, wherein the two parts are interacted through coordination bonds between lanthanide centers of the 2D squares and sulfonate oxygen atoms from 1D chains. Thus the 1D Ln-BPDSDC double chains are threaded through the 2D squares stacked in an eclipsed fashion to give a three-dimensional (3D) distinct architecture. The two compounds emit the characteristic Tb(III) and Eu(III) emissions in the solid state, respectively. Temperature-dependent luminescent studies show the emission intensities for both compounds decrease as temperature increases, which indicates these compounds have the potential for sensing temperature.

1. Introduction Coordination polymers formed from metal ions and bridging organic ligands are an important class of functional materials displaying diverse physical properties and intriguing structural topologies [1–4]. The interesting physical properties such as magnetism, electricity, and luminescence endowed by inorganic metal ions and organic ligands can be incorporated into a single coordination polymer, providing access to a new kind of functionalized materials. As an important series of metal ions, lanthanide ions attracted much attention because they can display distinctive intrinsic optical and magnetic properties arising from 4f configuration [5–7]. Since the lanthanide ions have the binding preference for oxygen atom, the carboxylate ligands are extensively utilized to construct the lanthanide-based coordination polymers [8–10]. In fact, the carboxylate ligand with a rich diversity of coordination modes and appropriate connectivities proved to be an effective component in the design of the coordination polymers [11–13]. Additionally, the structural complexity can be further enhanced through the design of carboxylate derivatives such as the sulfonate–carboxylate ligand, leading to a new type of materials [14,15]. The sulfonate ligand is known as a poor ligand with the weaker ligation nature of the sulfonate group [16,17]. However,

⁎

the sulfonate-carboxylate ligand with the strong coordination ability of carboxylate group is expected to be an interesting class of organic ligand, although they are much less well-investigated [18–20]. For examples, a Cu(II) compound based on 5-sulfoisophthalate ligand undergo a thermally induced single-crystal to single-crystal structural transformation, involving the coordination bonds related to the sulfonate oxygen atoms [21]. A series of lanthanide compounds with 4,8-disulfonyl-2,6-naphthalenedicarboxylate ligand showing various structures and interesting luminescent and magnetic properties have been reported [22]. Recently, we demonstrated a series of lanthanide compounds based on a novel sulfonate–carboxylate ligand of biphenyl-3,3′-disulfonyl-4,4′-dicarboxylate (BPDSDC4–) exhibiting high proton conductivity associated with the hydrophilic channels decorated by sulfonate groups [23]. The BPDSDC4– ligand is based on the π-system of biphenyl backbone, which is expected to enhance the luminescent properties of the resulting lanthanide compounds. In this contribution, the 1,4-benzenedicarboxylate (BDC2–) is introduced into the lanthanide-BPDSDC system, providing novel compounds, {[Ln2(BPDSDC)(BDC)(H2O)6]·4H2O}n (Ln = Tb(1) and Eu(2)), which contain the 2D squares of lanthanide-BDC and 1D double chains of lanthanide-BPDSDC and exhibit interesting characteristic lanthanide luminescence.

Corresponding author. E-mail address: [email protected] (Y.-L. Wang).

https://doi.org/10.1016/j.ica.2018.09.017 Received 18 August 2018; Received in revised form 6 September 2018; Accepted 6 September 2018 Available online 07 September 2018 0020-1693/ © 2018 Elsevier B.V. All rights reserved.

Inorganica Chimica Acta 484 (2019) 13–18

Z.-T. Li et al.

2. Experimental

Table 1 Crystal data and structural refinements for Tb(1) and Eu(2).

2.1. General remarks Empirical Formula Molecular mass Temperature[K] Crystal system Space group Z a [Å] b [Å] c [Å] α, deg β, deg γ, deg V [Å3] Dc [g∙cm−3] μ[mm−1] Measured reflections Independent reflections Observed reflections.[ I > 2σ(I)] R[int] R1[obsd. refl.] wR2 [obsd. refl.]

All chemicals are commercially available and used as received without further purification. IR (KBr pellets) spectra were recorded in the 400–4000 cm–1 range using a Perkin-Elmer Spectrum One FT-IR spectrometer. Elemental analyses were carried out on Elementar Perkin-Elmer 2400CHN microanalyzer. Thermogravimetric analyses were carried out on a PE Diamond TG/DTA unit at a heating rate of 10 °C/min under an air atmosphere. Powder X-ray diffraction patterns were performed on a Rigaku Miniflex II powder diffractometer using Cu-Kα radiation (λ = 1.5418 Å). The excitation/emission spectra and decays were recorded on an Edinburgh FLS980 fluorescence spectrophotometer equipped with both continuous (450 W) Xenon and pulsed flash lamps. Temperature-dependent emission spectra were recorded using an Oxford Instruments liquid nitrogen flow cryostat.

2.2. Syntheses of compounds 2.2.1. Synthesis of {[Tb2(BPDSDC)(BDC)(H2O)6]·4H2O}n (1) A mixture of Tb(NO3)3·6H2O (0.0272 g, 0.06 mmol), H4BPDSDC(0.0161 g, 0.04 mmol), and 1,4-benzenedicarboxylic acid (0.0132 g, 0.08 mmol) in H2O (10 mL) was introduced into a 25 mL Parr Teflon-lined stainless steel vessel. The vessel was sealed and heated to 100 °C for 3 days. Then the resulting mixture was cooled naturally to form colorless block crystals. (yield: 29% on the basis of Tb (NO3)3·6H2O). Anal. calcd. for C22H30O24S2Tb2 (1060.42): C, 24.92; H, 2.85%. Found: C, 24.90; H, 2.81%. Main IR features (cm−1, KBr pellet): 3414 (m), 1605 (s), 1576 (s), 1396 (s), 1229 (m), 1165 (s), 1090 (m), 1024 (m), 861 (m), 848 (m), 788 (m), 753 (s), 671 (w), 626 (m), 587 (w), 524 (m), 431 (m).

Tb(1)

Eu(2)

C22H30O24S2Tb2 1060.42 296(2) Triclinic P-1 2 10.4693(2) 11.0590(2) 14.9262(3) 72.580(2) 80.777(2) 80.196(2) 1613.80(6) 2.182 4.575 33,249 6596 6134 0.0354 0.0252 0.0635

C22H30O24S2Eu2 1046.50 296(2) Triclinic P-1 2 10.4060(5) 11.0721(5) 14.9186(5) 72.552(4) 80.225(3) 79.695(4) 1600.93(13) 2.171 4.112 32,655 6529 6157 0.0414 0.0248 0.0617

Table 2 Selected bond distances (Å) for Tb(1) and Eu(2). Tb(1) Tb1–O6 Tb1–O9 Tb1–O1B Tb1–O3B Tb1–O6A Tb1–O7A Tb1–O1W Tb1–O2W Tb1–O3W Tb2–O8 Tb2–O11 Tb2–O13 Tb2–O12C Tb2–O14C Tb2–O4W Tb2–O5W Tb2–O6W

2.2.2. Synthesis of {[Eu2(BPDSDC)(BDC)(H2O)6]·4H2O}n (2) A mixture of Eu(NO3)3·6H2O (0.0272 g, 0.06 mmol), H4BPDSDC(0.0161 g, 0.04 mmol), and 1,4-benzenedicarboxylic acid (0.0132 g, 0.08 mmol) in H2O (10 mL) was introduced into a 25 mL Parr Teflon-lined stainless steel vessel. The vessel was sealed and heated to 100 °C for 3 days. Then the resulting mixture was cooled naturally to form colorless block crystals. (yield: 26% on the basis of Eu (NO3)3·6H2O). Anal. calcd. for C22H30O24S2Eu2 (1046.50): C, 25.25; H, 2.89%. Found: C, 25.28; H, 2.79%. Main IR features (cm−1, KBr pellet): 3423 (m), 1614 (s), 1577 (s), 1475 (w), 1396 (s), 1223 (m), 1165 (s), 1091 (m), 1025 (m), 861 (m), 848 (m), 788 (m), 754 (s), 671 (w), 628 (m), 585 (w), 523 (m), 431 (m).

Eu(2) 2.447(3) 2.402(3) 2.323(3) 2.462(3) 2.567(3) 2.504(3) 2.474(3) 2.402(3) 2.366(3) 2.521(3) 2.293(3) 2.321(3) 2.346(3) 2.321(3) 2.448(3) 2.422(3) 2.507(4)

Eu1–O6 Eu1–O9 Eu1–O1B Eu1–O3B Eu1–O6A Eu1–O7A Eu1–O1W Eu1–O2W Eu1–O3W Eu2–O8 Eu2–O11 Eu2–O13 Eu2–O12C Eu2–O14C Eu2–O4W Eu2–O5W Eu2–O6W

2.460(2) 2.420(3) 2.335(3) 2.453(3) 2.577(2) 2.513(2) 2.503(3) 2.429(3) 2.389(3) 2.510(2) 2.349(3) 2.338(2) 2.381(3) 2.344(3) 2.480(3) 2.451(3) 2.509(3)

Symmetry transformation for equivalent atoms: A – x + 1, – y, – z + 2; B – x + 1, – y, – z + 1; C – x, – y + 1, – z + 1.

3. Results and discussion 3.1. Crystal structure of {[Ln2(BPDSDC)(BDC)(H2O)6]·4H2O}n Single-crystal X-ray diffraction analyses revealed that the two compounds are isomorphous and crystallize in a triclinic P-1 space group (Table 1). The Tb(1) was selected for describing their structures. There two Tb(III) ions, one BPDSDC4− ligand, two half-occupied BDC2– ligands, six coordinated water molecules, and four lattice water molecules compose the asymmetric unit of Tb(1). The Tb(III) ions have the coordination number of 8 and 9. Tb1 ion is nine-coordinated by two sulfonate oxygen atoms and four carboxylate oxygen atoms from three BPDSDC4– ligand, and three aqua ligands (Fig. 1). The coordination polyhedron of Tb2 ion consists of four carboxylate oxygen atoms of four BDC2– ligands, one sulfonate oxygen atom of a BPDSDC4– ligand, and three water oxygen atoms. The Tb–O bond lengths are in the range of 2.293(3)–2.567(3) Å (Table 2), which are comparable to those in other lanthanide-carboxylate compounds [23,27]. The BPDSDC4– and BDC2– ligands all are coordinated to four lanthanide ions (Scheme S1 in Supplementary material). The BPDSDC4– ligand binds to four metal ions through its two unidentate carboxylate oxygen atoms, three unidentate

2.3. X-ray crystallographic study Single-crystal X-ray diffraction experiments were performed at 293(2) K using a Rigaku Oxford SuperNova diffractometer equipped with an Eos detector and a Mo-Ka radiation (λ = 0.71073 Å). CrysAlisPro software package was used for collecting data, absorption correction and data reduction [24]. The structure was solved by the direct methods using SHELXT [25] and refined by the full-matrix least-squares method on F2 using SHELXTL [26]. All non-hydrogen atoms are refined with anisotropic thermal parameters. Hydrogen atoms bonded to carbon atoms were assigned to calculated positions. Water hydrogen atoms couldn’t be located. The R1 values are defined as R1 = Σ||Fo| – |Fc|| / Σ|Fo| and wR2 = {Σ[w(Fo2 – Fc2)2] / Σ[w (Fo2)2]}1/2. Details of the crystal parameters, data collection, and refinement are summarized in Table 1. Important bond lengths are listed in Table 2. 14

Inorganica Chimica Acta 484 (2019) 13–18

Z.-T. Li et al.

Fig. 1. The coordination environments of the Tb(III) ions (Symmetric codes see Table 2).

3.2. IR spectrum, thermogravimetric analysis and powder X-ray diffraction

sulfonate oxygen atoms, and one bidentate carboxylate oxygen atom, with three sulfonate oxygen atoms and one carboxylate oxygen atom uncoordinated. The present coordination mode of BPDSDC4– is different from those in reported lanthanide compounds, wherein the BPDSDC4– coordinates to four lanthanide ions and four K+ ions through one unidentate carboxylate oxygen atom, three bidentate carboxylate oxygen atoms, four unidentate sulfonate oxygen atoms, and one bidentate sulfonate oxygen atom [23] or binds to three Tb3+ ions and three K+ ions through four bidentate carboxylate oxygen atoms and four unidentate sulfonate oxygen atoms [28] (Scheme S2 in Supplementary material). The BDC2– ligand coordinated four metal ions via its four unidentate carboxylate atoms. As shown in Fig. 2, a pair of Tb2 atoms are linked by four carboxylate bridgings with a μ2-η1:η1 fashion to give a paddle-wheel-like Tb2(COO2)4 unit with the Tb···Tb separation of 4.225 Å, which is connected by the benzene linkers to form a 2D square propagating along ab plane. Such a 2D square based on the paddle-wheel-like Ln2(COO2)4 units for lanthanide compounds is uncommon due to the flexible coordination geometry and high coordination number of lanthanide ions. Each grid in the 2D square is nanosized with the dimensionality of about 10.4 × 11.1 Å (based on the Tb atoms). As depicted in Fig. 2, a pair of Tb1 ions are bridged by a pair of carboxylate groups with the μ2-η2:η1 fashion to give a dinuclear Tb2(COO2)2 unit with the Tb···Tb separation of 4.205 Å. The dinuclear Tb2(COO2)2 units are linked by the biphenyl to generate a 1D double chain structure. As shown in Fig. 2, the double chain is extended along c axis, which is therefore perpendicular to the 2D squares running along ab plane. As depicted in Fig. 2, each 1D double chain is encircled by a grid of the 2D square. The 1D chains are threaded through the grids of 2D squares and interacts with the 2D squares through Tb2–O8 coordination bonds. Thus the 1D double chains are threaded through the 2D squares stacked in an eclipsed fashion to form a 3D framework. It should be noted in this compound the Tb1 ions are linked by the sulfonate-carboxylate ligands to form 1D double chains, while the Tb2 ions are bridged by the carboxylate to generate the 2D structures. The two individual substructures are linked together through the Tb–O coordination bonds to give the final 3D architecture. Such a structural feature is rarely observed for the coordination polymers with mixed ligands.

For the IR spectra for both compounds, the asymmetric stretching bands of carboxylate groups can be observed between 1570 and 1620 cm–1. The symmetric stretching band for both compounds is at 1396 cm–1. The broad absorption bands centred at 3414 and 3423 cm−1 can be ascribed to the O–H stretching vibrations for Tb(1) and Eu(2), respectively. The strong peaks between 1000 and 1200 cm−1 for both compounds are typical for sulfonate groups. The sharp peaks at 626 and 628 cm−1 for Tb(1) and Eu(2), respectively, are the C–S stretching vibrations. The result of thermo-gravimetric analysis (TGA) for compounds Tb (1) and Eu(2) showed the loss of lattice water molecules are observed between 30 and 100 °C (measured 6.94%, theoretical 6.79% for Tb(1); measured 7.01%, theoretical 6.88% for Eu(2)) (Fig. S1). Then the coordinated water molecules are removed from 100 to 200 °C (measured 10.22%, theoretical 10.18% for Tb(1); measured 10.36%, theoretical 10.32% for Eu(2)). The combustion of organic ligands occurred at 420 °C. The measured powder X-ray diffraction (PXRD) patterns for Tb (1) and Eu(2) are close to the simulated pattern (Fig. S2), demonstrating the purity of the bulk samples. 3.3. Photoluminscent properties The solid state luminescent properties of Tb(1) and Eu(2) were studied at room temperature. The excitation and emission spectra of Tb (1) are presented in Fig. 3. The excitation spectrum of Tb(1) shows a broad excitation band between 250 and 390 nm, which can be primarily attributed to the π-electron transition of the organic ligand. Although the intensities are weak, two additional peaks can be found in the excitation spectrum. The shoulder peaks at 368 and 378 nm can be ascribed to the f–f transitions of 6F7 → 5L10 and 6F7 → 5G6, respectively. The broad band overlapping with the additional weak sharp f–f peaks in the excitation spectrum indicates that the Tb(III) luminescence is mainly excited via an effective sensitized process involving the organic ligand excited states. Upon excited at 336 nm, Tb(1) exhibits characteristic emission spectrum with the peaks at 490, 544, 586, 622, 650, 667, and 680 nm (Fig. 3). These emission peaks are assigned to the 15

Inorganica Chimica Acta 484 (2019) 13–18

Z.-T. Li et al.

Fig. 2. View of the 3D framework constructed from the 2D squares and 1D double chains.

D4 → 7FJ (J = 6–0) of Tb(III) ion. It should be mentioned that the rarely observed 5D4 → 7F1 and 5D4 → 7F0 are also detected in the emission spectrum. The 5D4 → 7F5 transition is the most intense among the series, leading to a green color for Tb(1) material. Furthermore, the temperature-dependent photoluminescence emission spectra of Tb(1) were examined from 100 to 300 K. As depicted in Fig. 4, the emission 5

intensity decreases gradually with increasing the temperature. For the dominant 5D4 → 7F5 (544 nm) transition, the intensity at 300 K is about 72% of that at 100 K. Such a phenomenon can be assigned to the thermal activation of nonradiative-decay [29–31]. Finally, the lifetimes of 5D4 emitting level for Tb(1) were monitored at 544 nm at different temperature. The lifetimes for 5D4 → 7F5 decrease with the increasing of

16

Inorganica Chimica Acta 484 (2019) 13–18

Z.-T. Li et al.

Fig. 6. Temperature-dependent emission spectra of Eu(2).

F0 → 5L6 (394 nm), 7F0 → 5D3 (415 nm), 7F0 → 5D2 (464 nm), 7F0 → D1 (534 nm), and 7F1 → 5D1 (534 nm) transitions (Fig. 5) [33]. The presence of strong sharp peaks of Eu(III) in the excitation spectrum indicates that the Eu(III) luminescence is not efficiently sensitized by the ligand. The emission peaks at 579, 592, 614, 650, 699, and 741 nm are the 5D0 → 7FJ (J = 0–5) transitions of Eu(III), respectively (Fig. 5). The dominant peak in the emission spectrum is 5D0 → 7F2 transition, which is electric-dipole. The intensity of 5D0 → 7F2 emission is extremely sensitive to the site symmetry and increases with the site symmetry of Eu(III) decreasing. The intensity of 5D0 → 7F2 transition is about 5.9 times that of 5D0 → 7F1 transition that related to the magnetic-dipole, which indicates the low site symmetry for Eu(III) ions in Eu(1) [34]. In addition, the 5D0 → 7F0 emission, which is induced by crystal-field J mixing, is also detected in the emission spectrum. It is well-known that the 5D0 → 7F0 transition is only allowed for Cs, Cn, or Cnv site symmetry for Eu(III) ion according to the electric-dipole selection rule [35]. As mentioned above, compound Eu(2) is crystallized in the triclinic crystal system and the Eu(III) ions lie on general positions. Therefore, the site symmetry of Eu(III) ions is C1. As a result, the detection of 5D0 → 7F0 emission in the emission spectrum of Eu(2) is not unreasonable. Finally, the presence of splitting for 5D0 → 7F1 and 5 D0 → 7F2 transitions are observed, further confirming the low site symmetry for Eu(III) ions (i.e. C1 with triclinic crystal system) [36]. Finally, the strong 5D0 → 7F2 emission appears, which is caused by the system rigidity, indicating the formation of a MOF network, in agreement with single-crystal X-ray analysis. Similar to that of Tb(1), The intensity of the emission of Eu(2) is decreased as the temperature increasing (Fig. 6). The intensity of the strongest peak of 5D0 → 7F2 transition at 300 K is 0.65 times lower than that at 100 K. This result indicates that the present compounds can be potentially as the luminescent thermometers. 7 5

Fig. 3. The excitation and emission spectra for Tb(1) at room temperature.

Fig. 4. Temperature-dependent emission spectra of Tb(1).

the temperature (Fig. S3). As case of Eu(2), the excitation spectrum (Fig. 5) shows the broad band between 280 and 420 nm overlaps a series of strong sharp peaks of the Eu(III) energy-level structure [32], suggesting a negligible contribution from the ligand. These 4f transitions in the excitation spectrum can be attributed to 7F0 → 5G6 (361 nm), 7F0 → 5H4 (374 nm),

4. Conclusions In conclusion, two lanthanide coordination polymers based on the carboxylate and sulfonate-carboxylate mixed ligands have been synthesized and characterized. In these structures, the sulfonate-carboxylate ligands connect the lanthanide ions to give the 1D chains, while the carboxylate ligands link the lanthanide ions to form 2D squares. The two parts are held together through the coordination bonds to generate a 3D structure. The luminescent properties studies show that the two compounds exhibit the characteristic lanthanide emissions. This work demonstrates that diverse structures can be obtained using the mixed ligands bearing different functional groups. Acknowledgements Fig. 5. The excitation and emission spectra for Eu(2) at room temperature.

This work was supported by the NNSF of China (21661014 and 17

Inorganica Chimica Acta 484 (2019) 13–18

Z.-T. Li et al.

21561015), and the key project of Natural Science Foundation of Jiangxi Province (20171ACB20008 and 20181BAB203001).

G.K.H. Shimizu, Nat. Chem. 1 (2009) 705. [15] T. Kurc, J. Janczak, J. Hoffmann, V. Videnova-Adrabinska, Cryst. Growth Des. 12 (2012) 2613. [16] A.P. Côté, G.K.H. Shimizu, Coord. Chem. Rev. 245 (2003) 49. [17] G.K.H. Shimizu, R. Vaidhyanathan, J.M. Taylor, Chem. Soc. Rev. 38 (2009) 1430. [18] S. Horike, R. Matsuda, D. Tanaka, M. Mizuno, K. Endo, S. Kitagawa, J. Am. Chem. Soc. 128 (2006) 4222. [19] Q.-Y. Liu, W.-L. Xiong, W.-Y. Xu, Y.-L. Wang, X.-W. Peng, L.-H. Xiong, Inorg. Chim. Acta 405 (2013) 222. [20] W.-W. Zhang, Y.-L. Wang, Q. Liu, Q.-Y. Liu, Inorg. Chem. 57 (2018) 7805. [21] B. Xiao, P.J. Byrne, P.S. Wheatley, D.S. Wragg, X. Zhao, A.J. Fletcher, K.M. Thomas, L. Peters, J.S.O. Evans, J.E. Warren, W. Zhou, R.E. Morris, Nat. Chem. 1 (2009) 289. [22] Q.-Y. Liu, W.-F. Wang, Y.-L. Wang, Z.-M. Shan, M.-S. Wang, J.K. Tang, Inorg. Chem. 51 (2012) 2381. [23] L.-J. Zhou, W.-H. Deng, Y.-L. Wang, G. Xu, S.-G. Yin, Q.-Y. Liu, Inorg. Chem. 55 (2016) 6271. [24] CrysAlisPro. Rigaku Oxford Diffraction: The Woodlands 2015 TX. [25] G.M. Sheldrick, Acta Cryst. A71 (2015) 3. [26] G.M. Sheldrick, Acta Crystallogr. C 71 (2015) 3. [27] Q. Lei, Q.-Y. Liu, Y.-L. Wang, L.-L. Chen, S.-G. Yin, Chinese, J. Struct. Chem. 35 (2016) 566. [28] H.-H. Wang, L.-J. Zhou, Y.-L. Wang, Q.-Y. Liu, Inorg. Chem. Commun. 73 (2016) 94. [29] M.L. Bhaumik, J. Chem. Phys. 40 (1964) 3711. [30] S.I. Weissman, J. Chem. Phys. 10 (1942) 214. [31] H.S. Peng, M.I.J. Stich, J.B. Yu, L.-N. Sun, L.H. Fischer, O.S. Wolfbeis, Adv. Mater. 22 (2010) 716. [32] M. Albin, R.R. Whittle, W.D. Horrocks Jr., Inorg. Chem. 24 (1985) 4591. [33] L.F. Marques, C.C. Correa, S.J. Ribeiro, M.V. Dos Santos, J.D.L. Dutra, R.O. Freire, F.C. Machado, J. Solid State Chem. 227 (2015) 68. [34] A.F. Kirby, D. Foster, F.S. Richardson, Chem. Phys. Lett. 95 (1983) 507. [35] M. Nogami, Y. Abe, Non-Cryst. Solids 197 (1996) 73. [36] C. Görller-Walrand, K. Binnemans, Handbook on the Physics and Chemistry of Rare Earths, Elsevier, Amsterdam, 1996.

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.ica.2018.09.017. References [1] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629. [2] S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed. 43 (2004) 2334. [3] M. Eddaoudi, D.B. Moler, H.L. Li, B.L. Chen, T.M. Reineke, M. O’Keeffe, O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319. [4] L.E. Kreno, K. Leong, O.K. Farha, M. Allendorf, R.P.V. Duyne, J.T. Hupp, Chem. Rev. 112 (2012) 1105. [5] J. Rocha, L.D. Carlos, F.A.A. Paz, D. Ananias, Chem. Soc. Rev. 40 (2011) 926. [6] Y. Cui, Y. Yue, G. Qian, B. Chen, Chem. Rev. 112 (2012) 1126. [7] L. Sorace, C. Benelli, D. Gatteschi, Chem. Soc. Rev. 40 (2011) 3092. [8] J.M. Taylor, T. Komatsu, S. Dekura, K. Otsubo, M. Takata, H. Kitagawa, J. Am. Chem. Soc. 137 (2015) 11498. [9] D.-X. Xue, A.J. Cairns, Y. Belmabkhout, L. Wojtas, Y. Liu, M.H. Alkordi, M. Eddaoudi, J. Am. Chem. Soc. 135 (2013) 7660. [10] Y.-L. Wang, C.-B. Han, Y.-Q. Zhang, Q.-Y. Liu, C.-M. Liu, S.-G. Yin, Inorg. Chem. 55 (2016) 5578. [11] Y.-J. Li, Y.-L. Wang, Q.-Y. Liu, Inorg. Chem. 56 (2017) 2159. [12] Q.-Y. Liu, Y.-L. Li, Y.-L. Wang, C.-M. Liu, L.-W. Ding, Y. Liu, CrystEngComm 16 (2014) 486. [13] Y. Cui, H. Xu, Y. Yue, Z. Guo, J. Yu, Z. Chen, J. Gao, Y. Yang, G. Qian, B. Chen, J. Am. Chem. Soc. 134 (2012) 3979. [14] J.A. Hurd, R. Vaidhyanathan, V. Thangadurai, C.I. Ratcliffe, I.L. Moudrakovsk,

18