Coordination and Supramolecular Assemblies of Fully Substituted

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Coordination and Supramolecular Assemblies of Fully Substituted Cyclopentanocucurbit[6]uril with Lanthanide Cations in the Presence of Tetrachlorozincate Anions, and Their Potential Applications Yun-Xia Qu,† Kai-Zhi Zhou,† Kai Chen,*,‡ Yun-Qian Zhang,† Xin Xiao,† QingDi Zhou,§ Zhu Tao,† Pei-Hua Ma,*,† and Gang Wei*,§ †

Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, China Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China § Commonwealth Scientific and Industrial Research Organization (CSIRO), Manufacturing, Lindfield, New South Wales 2070, Australia ‡

S Supporting Information *

ABSTRACT: Coordination and supramolecular assemblies of a fully substituted cyclopentanocucurbit[6]uril (CyP6Q[6]) with a series of lanthanide cations (Ln3+) have been investigated in the presence of tetrachlorozincate anion ([ZnCl4]2−). X-ray singlecrystal diffraction analysis has revealed that the interaction of CyP6Q[6] and a series of Ln3+cations unexpectedly results in the formation of at least seven different CyP6Q[6]-based coordination complex adduct and supramolecular assemblies groups, including with (1) La3+, Ce3+cations; (2) Pr3+, Nd3+cations; (3) Eu3+, Gd3+, Tb3+, Dy3+ with P1̅ or P1 space group, in which CyP6Q[6] molecules coordinate alternatively with Ln3+cations and form linear coordination polymers; (4) CyP6Q[6] molecules interact alternatively with [Ho(H2O)8]3+ aqueous complexes and form linear supramolecular chains; CyP6Q[6] molecules can assemble two different Ln3+ free porous supramolecular assemblies from CyP6Q[6]−Ln(NO3)3−ZnCl2−HCl systems, Ln = Tm, Yb, and Lu; however, no solid crystals were obtained from system containing Er3+cation. Thus, these differences could lead CyP6Q[6] to be useful in not only the isolation of lighter lanthanides from their heavier lanthanides but also special selectivity for different volatile organic compounds.

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INTRODUCTION Numerous works have proven that cucurbit[n]urils (Q[n]s)1 can coordinate with various metal ions, which have longer ionic radius, such as alkali, alkaline earth, lanthanide cations and so on; interact metal complexes or clusters with ligands, such as water, amino and so on, through the intermolecular interactions by virtue of their portal carbonyl oxygens.2−6 Moreover, taking advantage of the outer-surface interaction of Q[n] could results in the formation of novel Q[n]-based coordination polymers and supramolecular assemblies in the presence of structuredirecting agents,7a such as polychloride transition metal complex anions and small aromatic compounds.7b It is well-known that the lanthanides have the so-called “lanthanide contraction” effect because the 4f orbitals exhibit poor shielding of the nuclear charge with increasing atomic number of the lanthanides,8 As a consequence, the lanthanides exhibit similar chemical properties and difficulty in chemically separating the lanthanides. However, our recent works revealed that various Q[n]s and their alkyl-substituted derivates can recognize lanthanide cations,9 the difference in the interaction © XXXX American Chemical Society

behaviors of a certain Q[n] with this series of ions tend to reflect the difference of ion radii between these ions, which decrease from 1.03 Å for La3+ to 0.86 Å for Lu3+.8 Generally, a selected Q[n] interacts with this series of cations and shows obvious difference between the lighter lanthanide cations and heavier lanthanide cations. For example, the unsubstituted Q[6] forms linear coordination polymers inserting in the cells of [Md‑blockCl4]2−-based honeycomb-like frameworks with a series of Ln3+cations, except for La3+, Ce3+, Pr3+, and Nd3+, which form precipitation with Q[6] under the same synthesis condition. Thus, Q[6] can divide the lanthanide series into two groups.10 Another Q[6], hexacyclohexanocucurbit[6]uril (HCyHQ[6]) can structurally classify the lanthanide series into four HCyHQ[6] complex groups: HCyHQ[6]/Ln3+ pair, HCyHQ[6]/Ln3+ molecular bowl, HCyHQ[6]/Ln3+ molecular capsule, and HCyHQ[6]/Ln3+-based one-dimensional coordination polymer.11 More detailed Q[n]/Ln3+ complexes and Received: April 16, 2018

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DOI: 10.1021/acs.inorgchem.8b01039 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

2[ZnCl4]·(H3O)·20(H2O) (5) was obtained from Sm(NO3)3·6H2O (0.029 g), anal. calcd. for 5, C54H115O39 N24Cl8Zn2Sm (%): H, 5.06; C, 28.33; N, 14.68; found: H, 5.14; C, 28.40; N, 14.59; {Eu(H2O)5· (C54H60N24O12)}·2[ZnCl4]·(H3O)·1(H2O) (6) was obtained from Eu(NO3)3·6H2O (0.029 g), anal. calcd for 6, C54H95O29N24Cl8Zn2Eu (%): H, 4.54; C, 30.73; N, 15.93; found: H, 4.62; C, 30.66; N, 16.01; {Gd(H2O)5·(C54H60N24O12)}·2[ZnCl4]·(H3O)·11(H2O) (7) was obtained from Gd(NO3)3 ·5H2 O (0.029 g), anal. calcd. for 7, C54H95O29N24Cl8Zn2Gd (%): H, 4.53; C, 30.65; N, 15.89; found: H, 4.47; C, 30.57; N, 15.79; {Tb(H2O)5·CyP6Q[6]}·2[ZnCl4]·(H3O)· 32(H2O) (8) was obtained from Tb(NO3)3·6H2O (0.029 g), anal. calcd. for 8, C54H137O50N24Cl8Zn2Tb (%): H, 5.53; C, 25.98; N, 13.47; found: H, 5.43; C, 25.83; N, 13.36; {Dy(H2O)5·(C54H60N24O12)}· [ZnCl4]·(H3O)·12(H2O) (9) was obtained from Dy(NO3)3·6H2O (0.030 g), anal. calcd. for 9, C54H97O30N24Zn2Cl8Dy (9): H, 4.57; C, 30.32; N, 15.71; found: H, 4.61; C, 30.37; N, 15.79; CyP6Q[6]· [Ho(H2O)8]·[ZnCl4]· [Zn(H2O)Cl3]·15(H2O) (10) was obtained from HoCl3·6H2O (0.025 g), anal. calcd. for 10, C54H108O36N24Cl7Zn2Ho (%): H, 4.92; C, 29.30; N,15.19; found: H, 5.01; C, 29.37; N, 15.23; 11 was obtained from Er(NO3)3·5H2O (0.029 g); CyP6Q[6]·2[ZnCl4]·(H3O)·8(H2O) (12) was obtained from Tm(NO 3 ) 3 ·5H 2 O (0.029 g), anal. calcd. for 12, C54H79O21N24Cl8Zn2 (%): H, 4.39; C, 35.74;N, 18.52; found: H, 4.41; C, 35.77; N, 18.49; CyP6Q[6]·2[ZnCl4]·4(H3O)·19(H2O) (13) was obtained from Yb(NO3)3•5H2O (0.029 g), anal. calcd. for 13, C54H110O35 N24Cl8Zn2 (%): H, 5.36; C, 31.33; N, 16.24; found: H, 5.41; C, 31.28; N, 16.29; CyP6Q[6]·2[ZnCl4]·4(H3O)·24(H2O) (14) was obtained from LuCl3·6H2O (0.019 g), anal. calcd for 14, C54H120O40N24Cl8Zn2 (%): H, 5.60; C, 30.03; N, 15.56; found: H, 5.68; C, 30.07; N, 15.59. X-ray Crystallography. A suitable single crystal (∼0.2 × 0.2 × 0.1 mm3) was taken up in paraffin oil and mounted on a Bruker SMART Apex II CCD diffractometer equipped with a graphite-monochromated Mo−Kα (λ = 0.71073 Å, μ = 0.828 mm−1) radiation source operating in the ω-scan mode. Data were corrected for Lorentz and polarization effects (SAINT), and semiempirical absorption corrections based on equivalent reflections were also applied (SADABS). The structure was elucidated by direct methods and refined by the fullmatrix least-squares method on F2 with the SHELXS-97 and SHELXL97 program packages, respectively.17 All non-hydrogen atoms were refined anisotropically. Carbon-bound hydrogen atoms were introduced at calculated positions, and were treated as riding atoms with an isotropic displacement parameter equal to 1.2 times that of the parent atom. Most of the water molecules in the compounds were omitted using the SQUEEZE option of the PLATON program.18 The squeezed water molecules are 16, 14, 14, 16, 21, 12, 12, 33, 13, 15, 9, 23, and 28 for compounds 1−10, 12−1419 respectively. Moreover, Analytical expressions for neutral-atom scattering factors were employed, and anomalous dispersion corrections were incorporated. Details of the crystal parameters, data collection conditions, and refinement parameters for these compounds are summarized in contain the supplementary crystallographic data for this paper. In addition, the crystallographic data for the reported structures have been deposited at the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC-1825839 (1), 1473197 (2), 1825849 (3), 1825850 (4), 1473199 (5), 1825868 (6), 1825871 (7), 1825547 (8), 1825872 (9), 1825875 (10), 1825873 (12), 1825874 (13) and 1825876 (14). These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_ [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: + 44 1223 336033. Powder X-ray diffraction analyses of compounds 1, 3, 5, 10, 12, and 14, and comparison with simulations, showed that the bulk of the samples essentially consisted of pure crystalline phases (Figure S10). Vapor Absorption Studies for 12 and 14. The required solid complex (0.5−1.0 g) contained in a tared open glass phial was added to a sealed glass vessel which was then evacuated with the aid of a vacuum pump. Pumping was continued until the sample achieved constant weight. A second open container containing a few mL of the

supramolecular assemblies have summarized in a recent review9 and works.12−15 These researches revealed that Q[n]s could be useful in not only in the isolation of lighter lanthanides from their heavier lanthanides or in turn but also in the selective adsorption for different volatile organic compounds. In the present work, a fully cyclopentano-substituted cucurbit[6]uril (CyP6Q[6]) was selected as a ligand (Figure 1),16 and interaction behavior of CyP6Q[6] with a series of

Figure 1. Structure of CyP6Q[6] viewed from (a) the top and (b) the side.

lanthanide cations in an acidic (HCl 3M) aqueous solution in the presence of tetrachlorozincate anion ([ZnCl4]2−) as a structure directing agent7 has been systematically investigated. The experimental results revealed that CyP6Q[6] molecule exhibited the highest ability in the recognition of lanthanide cations and can structurally classify the lanthanide series into seven CyP6Q[6]-based coordination and supramolecular assemblies groups: three different CyP6Q[6]/Ln3+-based linear coordination polymers with La3+, Ce3+; Pr3+, Nd3+ and Eu3+, Gd3+, Tb3+, Dy3+ cations, respectively, CyP6Q[6]/Ln3+molecular capsule with Sm3+cation, and adduct of CyP6Q[6] with Ho3+, three different porous Ln3+ free CyP6Q[6]-based supramolecular assemblies with Tm 3+, Yb 3+ and Lu 3+, respectively. Thus, the different crystal habits and crystal structures of CyP6Q[6] with series of Ln3+ cations offer potential applications in separating different Ln3+ cations or selective adsorption for volatile organic compounds.

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EXPERIMENTAL SECTION

Synthesis. Chemicals, such as lanthanide nitrates was of reagent grade and was used without further purification. CyP6Q[6] was prepared as reported elsewhere.1 Elemental analyses were carried out on a EURO EA-3000 elemental analyzer. A similar process was used to prepare crystals of related compounds: La(NO3)3·6H2O (0.0647 mmol) was dissolved in 1.0 mL of 3.0 M HCl (solution A), CyP6Q[6] (10 mg, 0.0081 mmol) was dissolved in 0.5 mL of neutral water (solution B), and was then added in the solution A with stirring. X-ray quality crystals were obtained from the solution over a period of 1−3 weeks. The color of crystals was dependent on the lanthanide ions. Summarizing the preparations, {La(H2O)6·(C54H60N24O12)}·2[ZnCl4]·Cl·2(H3O)·14(H2O) (1) was obtained from La(NO3)3· 6H2O (0.028 g), anal. calcd for 1, C54H106O34N24Cl9Zn2La (%): H, 4.80; C, 29.16; N, 15.11; found: H, 4.92; C, 29.08; N, 15.03; {Ce(H2O)6·(C54H60N24O12)}·2[ZnCl4]·Cl·2(H3O)·12(H2O) (2) was obtained from Ce(NO3)3·6H2O (0.028 g), anal. calcd for 2, C54H102 O32N24 Cl9Zn2Ce (%): H, 4.70; C, 29.62; N, 15.35; found: H, 4.62; C, 30.11; N, 15.51; {Pr(H2O)5·CyP6Q[6]}·2[ZnCl4]·(H3O)·16(H2O) (3) was obtained from Pr(NO3)3·6H2O (0.028 g), anal. calcd. for 3, C54 H105O34N24Cl8Zn2Pr (%): H, 5.40; C, 32.73; N, 16.07; found: H, 5.48; C, 32.62; N, 16.11; {Nd(H2O)5CyP6[Q6]}·2[ZnCl4]·(H3O) · 15(H2O) (4) was obtained from Nd(NO3)3·6H2O(0.028 g), anal. calcd. for 4, C54H95O29N24Cl8Zn2Nd (%): H, 4.55; C, 30.84; N, 15.98; found: H, 4.52; C, 30.95; N, 16.10; {Sm(H2O)6· (C54H60N24O12)}· B

DOI: 10.1021/acs.inorgchem.8b01039 Inorg. Chem. XXXX, XXX, XXX−XXX

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interaction of Q[n],7 but also the coordinated La3+ cations through electrostatic interaction in the CyP6Q[6]/La3+-based supramolecular assembly. The substituted cyclopentano seem somewhat to prevent the [ZnCl4]2− anions from the outer surface of CyP6Q[6] molecules (Figure 2e). The coordination and supramolecular assembly behaviors in compound 2 are similar to those in compound 1 (see Figure S1). They exhibit some differences in bond lengths due to the increase of atomic number. The Ce−Owater distances are in the range 2.479−2.687 Å, and the average distance is 2.555 Å, 0.017 Å shorter than that of La−Owater, and The Ce−Ocarbonyl distances are in the range 2.505−2.566 Å and the average distance is 2.530 Å, 0.013 Å shorter than that of La−Ocarbonyl. In the second isomorphic group, CyP6Q[6] coordinates with Pr3+ or Nd3+ cations, respectively and forms isomorphic compounds 3 and 4. Figure 3a shows an overview of supramolecular assembly in the compound 3 constructed of a deformed [ZnCl4]2− anion-based honeycomb-like framework (Figure 3b) and linear coordination polymers assembled by alternative CyP6Q[6] molecules and Pr3+ cations which are filled in the cells in the framework (Figure 3c). Figure 3d shows the detailed coordination of a CyP6Q[6] molecule with two Pr3+ cations. Each Pr3+ cation (Pr1 occupies two position with 50% occupancy) coordinates to nine oxygens, five water molecules (O1W, O2W, 2O3W, O4W), four portal carbonyl oxygens (O1, O2 from a CyP6Q[6] molecule, O1′, O2’ from another CyP6Q[6] molecule of two neighboring CyP6Q[6] molecules). The Pr−Owater distances are in the range 2.213− 2.722 Å and the average distance is 2.436 Å, and the Pr− Ocarbonyl distances are in the range 2.298−2.603 Å and the average distance is 2.427 Å. Generally, the coordination and supramolecular assemblies of the first isomorphic group and the second isomorphic group are basically the same, except the deformed [ZnCl4]2− anion-based honeycomb-like framework in the second isomorphic group. However, interaction between CyP6Q[6] molecules and [ZnCl4]2− anions in the second isomorphic group are quite different from that in the first isomorphic group (Figure 3e). Two [ZnCl4]2− anions surround the coordinated Pr3+ cation through electrostatic interaction, and four [ZnCl4]2− anions surround the CyP6Q[6] molecule through the so-called outer surface interaction of Q[n]. Close inspection reveals that [ZnCl4]2− anions are closed to the fivemember ring of glycoluril moieties of CyP6Q[6] molecules. The coordination and supramolecular assembly behaviors in compound 4 are similar to those in compound 3 (See Figure S2 in the ESI). The Nd−Owater distances and the Nd−Ocarbonyl distances are in the range 2.167−2.939 Å and 2.349−2.584 Å, respectively, the average distance is 2.553 and 2.4667 Å, respectively. The third isomorphic group contains only one compound 5, in which each CyP6Q[6] coordinates with two Sm3+cations, and forms molecular capsule-like complex. These capsules interact with [ZnCl4]2− anions through the outer surface interaction of Q[n] and electrostatic interaction, and form a novel supramolecular assembly with numerous small channels (Figure 4a). This assembly constructed of CyP6Q[6]-based layers. Figure 4b shows a CyP6Q[6]-based layer with a topological grid sheet, in which CyP6Q[6] molecules occupy each interaction point (Figure 4b), every four CyP6Q[6] molecules construct of a grid, and overlapping of these grids forms a channel in the supramolecular assembly (Figure 4c). Each CyP6Q[6]/Sm3+ complex is surrounded by eight [ZnCl4]2− anions through the electrostatic interaction and the

volatile liquid, chosen in turn from acetonitrile, methanol, ethanol, methane, diethyl ether or dichloromethane, was then added and the vessel resealed. The weight change of the sample was then determined at ∼0.25−1 h intervals over 24 h to obtain the vapor absorption profile.

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RESULTS AND DISCUSSION Description of the crystal structures of the compounds. Generally, isomorphic solidstate products of a selected Q[n] with the series of Ln3+cations can be obtained under the same synthetic condition, whereas the compounds obtained from the CyP6Q[6]−Ln(NO3)3−ZnCl2−HCl systems can be classified into seven isomorphous groups with different unit cell parameters according to their crystal data (Table S1). We introduce them with increasing atomic number of lanthanide. In the first isomorphic group, CyP6Q[6] coordinates with La3+ or Ce3+cations, respectively and forms isomorphic compounds 1 and 2. Figure 2a shows an overview of supramolecular

Figure 2. Crystal structures of 1: (a) overall view of the supramolecular assembly constructed of [ZnCl4]2− and CyP6Q[6]/ La3+ complexes; (b) [ZnCl4]2−-based honeycomb-like framework; (c) CyP6Q[6]/La3+ complex-based 1D supramolecular chain; (d) detailed interactions of a La3+ cation with a CyP6Q[6] molecule; (e) CyP6Q[6]/La3+ complex surrounded by six [ZnCl4]2− anions (La3+ cations in the complex are omitted for clarity).

assembly constructed of CyP6Q[6]/La3+ complexes and [ZnCl4]2− anions in the compound 1. The assembly can be also read as a combination of a [ZnCl4]2−-based honeycomblike framework (Figure 2b) and CyP 6Q[6]/La 3+-based coordination polymers, which are filled in the cells in the framework (Figure 2c). Each linear polymer is constructed of alternatively CyP6Q[6] molecules and La3+ cations through direct coordination. Each CyP6Q[6] molecule is sandwiched by two La3+ cations and each La3+ cation (La1) coordinates to nine oxygens, six water molecules (O1W, O2W, O3W, O4W, O5W, O6W), three portal carbonyl oxygens (O1, O6 from a CyP6Q[6] molecule, O10 from another CyP6Q[6] molecule of two neighboring CyP6Q[6] molecules). The La−Owater distances are in the range 2.512−2.672 Å (average distance, 2.572 Å), and the La−Ocarbonyl distances are in the range 2.525−2.573 Å (average distance, 2.543 Å) (Figure 2d). [ZnCl4]2− anions surround not only the outer surface of Q[6] molecules through the so-called the outer surface C

DOI: 10.1021/acs.inorgchem.8b01039 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 3. Crystal structures of 3: (a) oerall view of the supramolecular assembly constructed of [ZnCl4]2− and CyP6Q[6]/Pr3+ complexes; (b) [ZnCl4]2−-based honeycomb-like framework; (c) CyP6Q[6]/Pr3+ complex-based 1D supramolecular chain; (d) detailed interactions of a Pr3+ cations with a CyP6Q[6] molecule; (e) CyP6Q[6]/Pr3+ complex surrounded by six [ZnCl4]2− anions (Pr3+ cations in the complex are omitted for clarity).

Figure 4. Crystal structures of 5: (a) overall view of the CyP6Q[6]/Sm3+-[ZnCl4]2−-based supramolecular assembly with numerous small channels; (b) CyP6Q[6]-based layer with a topological grid sheet; (c) channel formed by the overlapped CyP6Q[6]-based grids; (d) CyP6Q[6]/Sm3+ complex surrounded by eight [ZnCl4]2− anions (Sm3+ cations in the complex are omitted for clarity); (e) detailed interactions of a Sm3+ cation with a CyP6Q[6] molecule.

outer surface interaction of Q[n] (Figure 4d). Each Sm3+ cation (Sm1) in the CyP6Q[6]/Sm3+ complex coordinates to eight oxygens, six water molecules (O1W, O2W, O3W, O4W, O5W, O6W) and two portal carbonyl oxygens (O1 and O2 of the CyP6Q[6] molecule). The Sm−Owater distances are in the range

2.346−2.557 Å and the average distance is 2.433 Å, and the Sm−Ocarbonyl distances are in the range 2.466−2.514 Å and the average distance is 2.490 Å (Figure 4e). According to unit-cell parameters, the fourth isomorphic group includes four compounds 6-9 containing Eu3+, Gd3+, D

DOI: 10.1021/acs.inorgchem.8b01039 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 5. Crystal structures of 10: (a) overall view of the supramolecular assembly constructed of [ZnCl4]2− anions, [Zn(H2O)Cl3]− anions, [Ho(H2O)8]3+ complexes, and CyP6Q[6] molecules; (b) deformed [ZnCl4]2− and [Zn(H2O)Cl3]−-based honeycomb-like framework; (c) 1D supramolecular chain constructed of alternative CyP6Q[6] molecules and [Ho(H2O)8]3+ complexes; (d) detailed interactions of [Ho(H2O)8]3+ complexes with a CyP6Q[6] molecule; (e) CyP6Q[6] molecule surrounded by three [ZnCl4]2− anions and three [Zn(H2O)Cl3]− anions.

Figure 6. Crystal structures of 12: (a) overall view of the supramolecular assembly constructed of [ZnCl4]2− anions and CyP6Q[6] molecules; (b) channel in the framework constructed of [ZnCl4]2− anions and CyP6Q[6] molecules; (c−e) interaction of CyP6Q[6] molecules with [ZnCl4]2− anions.

The fifth group also contains only one compound 10, in which Ho3+ cation does not directly coordinate to the portal carbonyl oxygens but interacts with eight water molecules and form a [Ho(H2O)8]3+ complex. Figure 5a shows an overview of the supramolecular assembly constructed of CyP6Q[6] molecules, [Ho(H2O)8]3+ complexes, [ZnCl4]2− anions, and [Zn(H2O)Cl3]− anions, in which [ZnCl4]2− anions and

Tb3+, Dy3+ cations, respectively. Looking into the coordination of CyP6Q[6] molecules with these four Ln3+ cations and corresponding supramolecular assemblies reveals that they are almost exactly the same as those in compounds 3 and 4. The related coordination complexes and CyP6Q[6]/Ln3+-based supramolecular assemblies of compounds in the fourth group are shown in Figures S3−S6. E

DOI: 10.1021/acs.inorgchem.8b01039 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 7. Crystal structures of 13: (a) overall view of the supramolecular assembly constructed of CyP6Q[6]-[ZnCl4]2−-based layers; (b) a CyP6Q[6]-[ZnCl4]2−-based gridlike layer; (c) interaction of a CyP6Q[6] molecule with four [ZnCl4]2− anions; (d) interaction of CyP6Q[6] molecules with [ZnCl4]2− anions in a grid.

[Zn(H2O)Cl3]− anions assemble a deformed honeycomb-like framework (Figure 5b), and linear supramolecular chains with alternative CyP6Q[6] molecules and [Ho(H2O)8]3+ complexes are filled in the cells of the framework (Figure 5c). Interaction of CyP6Q[6] molecules and [Ho(H2O)8]3+ complexes belongs to the hydrogen bonding of the coordinated water molecules and portal carbonyl oxygens of the CyP6Q[6] molecule (Figure 5d). The Ho−Owater distances are in the range 2.331−2.357 Å (average distance, 2.342 Å), and the Owater−Ocarbonyl distances are in the range 2.668−2.819 Å. Figure 5e shows interaction of a CyP6Q[6] molecule with three [ZnCl4]2− anions and three [Zn(H2O)Cl3]− anions through the outer surface interaction of Q[n], that is, the ion−dipole interaction of the electropositive outer surface of CyP6Q[6] molecule and chloride atom from [ZnCl4]2− or [Zn(H2O)Cl3]− anions.7 In the last two isomorphic groups, one group contains two compounds 12−13, obtained from CyP6Q[6]−Tm or Yb(NO3)3−ZnCl2−HCl systems, and one group contains only compound 14 obtained from CyP6Q[6]−Lu(NO3)3−ZnCl2− HCl system, respectively. It is worth noting that despite numerous attempts, all the efforts thus far paid failed to obtain a satisfactory quality single crystals for compound 11, but the basic structure are present. Compounds 12-14 show no Ln3+ cations, the supramolecular assemblies show the porous structure features. For example, the supramolecular assembly in compound 12 shows a grid-like framework (Figure 6a), each core is constructed of four CyP6Q[6] molecules. Figure 6b shows a channel in the framework is constructed of CyP6Q[6] molecules [ZnCl4]2− anions through the outer surface interaction of Q[n]. Close inspection reveals the detailed interaction between the two components (Figures. 6c-e). Whereas the supramolecular assembly in compound 14 (Figure 7a) is constructed of CyP6Q[6]-[ZnCl4]2−-based grid-like layers, every four CyP6Q[6] molecules construct of a grid in a layer (Figure 7b). The overlapped CyP6Q[6]-based layers yield numerous channels (Figure 7a). How could the supramolecular assembly be formed? Close inspection reveals

that every two neighboring CyP6Q[6]-based layers are linked by a [ZnCl4]2−-based layer (Figure 7a). Each CyP6Q[6] molecule interacts with four [ZnCl4]2− anions (Figure 7c), and the four CyP6Q[6] molecule of each grid in the CyP6Q[6]based layer linked by four [ZnCl4]2− anions through the outer surface interaction of Q[n] (Figure 7d). CyP6Q[6] shows more sensitive to the lanthanide cations than the other Q[6] and alkyl-substituted Q[6]s based on the size differences between these ions. Under the same interaction condition, unsubstituted Q[6] can divide the lanthanide series into two isomorphic groups;10 HCyHQ[6], four isomorphic groups;11 the inverted cucurbit[6]uril (iQ[6]), six isomorphic groups;17 CyP6Q[6], even up to seven isomorphic groups. Thus, we first consider CyP6Q[6] to be useful for recognize and isolate the series of lanthanides from each other. As operated in the previous works, 11 typical Ln3+lighter− Ln3+heaviyer−CyP6Q[6]−ZnCl2−HCl (3M) systems were selected as representative examples with a Ln3+lighter: Ln3+heavier in 1:1 ratios. They included La3+−Ho3+, La3+−Tm3+, La3+−Lu3+, Ce3+−Ho3+, Ce3+−Tm3+, Ce3+−Lu3+, Pr3+−Eu3+, Pr3+−Er3+, Pr3+−Lu3+, Nd3+−Eu3+, Nd3+−Er3+, Nd3+−Lu3+ systems, and energy dispersive spectroscopy (EDS) showed general rules that the more far from each other the two Ln3+ elements in the series of lanthanides, the better the isolation results. For example, the solid products collected from the most selected systems contained almost 100% of light lanthanide elements (Figure S7), whereas The Nd3+−Eu3+ and Pr3+−Eu3+ systems contained a higher proportion of the 60.78−68.69% lighter element (Figure S8). Considering that some of CyP6Q[6]-based supramolecular assemblies have numerous pores and channels, which could selectively adsorb volatile compounds, thus, the porosity properties of two selected compounds 12 and 14 which have microporous features were tested using a Micrometrics ASAP2020HD88 automated sorption analyzer. Gas (CH3OH) sorption isotherms for the microporous material were measured at 285 K, and the BET surface area of F

DOI: 10.1021/acs.inorgchem.8b01039 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 8. Absorption profiles on (left) compound 12 and (right) compound 14 for six volatile compounds.

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compounds 12 and 14 calculated from the isotherm were 422.8 and 1013.0 m2 g−1, respectively. Further sorption experiments confirmed our conjecture. Figure 8 shows sorption profiles for several volatile materials on compounds 12 and 14, the absorption capacities for the selected volatile compounds with different polarities are methanol 0.183, 0.389 g/g; dichloridemethane 0.175, 0.401g/g; methane 0.182, 0.349 g/g; diethyl ether 0.167, 0.206 g/g; acetonitrile 0.078, 0.201 g/g; and ethanol 0.0734, 0.152 g/g, respectively. Different sorption capacities for these two porous compounds are consistent with the porous sizes, as shown in Figures 6a and 7b, and which have different porous sizes and the BET surface areas. The stable framework after the sorption experiments also ensured by PXRD (Figure S9).

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*E-mail: [email protected] (P.H.M.). *E-mail: [email protected] (K.C.). *E-mail: [email protected] (G.W.). ORCID

Kai Chen: 0000-0002-5852-3264 Xin Xiao: 0000-0001-6432-2875 Pei-Hua Ma: 0000-0002-4965-0632 Notes

The authors declare no competing financial interest.

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CONCLUSIONS

ACKNOWLEDGMENTS We thank the National Natural Science Foundation of China (Grants 21601090 and 21762011), the Natural Science Foundation of Jiangsu Province (Grant BK20160943), the “Chun Hui” Project of the Chinese Ministry of Education (Grant Z2016010) and the Major Program for Creative Research Groups of Guizhou Provincial Education Department (2017-028) and the graduate student innovative funding of Guizhou University (2017006).

In the present work, we investigated the interaction of CyP6Q[6] with a series of Ln3+ cations in the presence of [ZnCl4]2− anion as a structure directing agent. Single-crystal Xray diffraction analyses revealed that the CyP6Q[6]/Ln3+[ZnCl4]2−-based interaction products can be structurally classified into seven CyP6Q[6]-based coordination and supramolecular assemblies groups. More importantly, CyP6Q[6] can form solid products with lighter lanthanide cations, whereas heavier lanthanides from Tm3+ to Lu3+ cations do not coordinate to CyP6Q[6] portals under employed crystallization conditions. Thus, this property of CyP6Q[6]/Ln3+ could be used for the isolation lighter lanthanides from the heavier lanthanides. Moreover, the CyP6Q[6]/Ln3+-[ZnCl4]2−-based supramolecular assemblies have different structure features; some of them are characterized by porous features and could be used for the sorption of volatile organic molecules.

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AUTHOR INFORMATION

Corresponding Authors

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REFERENCES

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S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b01039. Figures S1−S10 and Table S1 (PDF) Accession Codes

CCDC 1473197, 1473199, 1825547, 1825839, 1825849− 1825850, 1825868, and 1825871−1825876 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/ data_request/cif, or by emailing [email protected]. uk, or by contacting The Cambridge Crystallographic Data G

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