Article pubs.acs.org/IC
closo-Dodecaborate Intercalated Yttrium Hydroxide as a First Example of Boron Cluster Anion-Containing Layered Inorganic Substances Alexey D. Yapryntsev, Alexander Yu. Bykov, Alexander E. Baranchikov, Konstantin Yu. Zhizhin, Vladimir K. Ivanov,* and Nikolay T. Kuznetsov Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow 119991, Russia S Supporting Information *
ABSTRACT: The first member, Y2(OH)5.46(B12H12)0.23Cl0.08· 4.98H2O, of a new family of boron-containing substances, closo-dodecaborate intercalated layered rare-earth hydroxides, was synthesized using a microwave-assisted hydrothermal method. The structure and composition of this compound were studied by X-ray diffraction, transmission and scanning electron microscopy, thermal analysis, inductively coupled plasma mass spectrometry, IR spectroscopy, and X-ray photoelectron spectroscopy. The title compound had the composition Y2(OH)5.46(B12H12)0.23Cl0.08·4.98H2O and crystallized in a form of plate-like, aggregated particles less than 10 nm thick. The coordination of closo-dodecaborate anions with yttrium hydroxide host layers was demonstrated.
■
INTRODUCTION The layered rare-earth hydroxides (LRHs) that have been discovered recently represent a new class of pillared inorganic materials with anion exchange properties.1,2 These materials are considered as structural analogues of well-known layered double hydroxides (LDHs) and currently attract a vast amount of attention, due to their unusual properties, combining features of host rare earth matrices and guest intercalated anions. Today’s most promising LRH applications include the design of luminescent materials and biomaterials.3−7 The properties of LRHs as anion exchangers arise from their structure, which is similar to the brucite-like structure of LDHs, with positively charged, metal-hydroxide layers shielded by the anions localized between them. However, the layers in LRHs,8 in comparison with LDHs,9 are composed of polyhedra of higher order, due to higher coordination numbers of rare-earth metals. The LRH phases have two types of lanthanide ion environment, containing nine- and eightfold coordinated ions. The eightfold coordinated lanthanide ion is surrounded by seven hydroxyl ions and one water molecule, forming a {Ln(OH)7(H2O)} dodecahedron. The ninefold coordinated lanthanide ion has oxygen atoms bonded to eight hydroxyls and one water molecule, forming a monocapped, square antiprism {Ln(OH)8(H2O)}, with the water molecule in the capping position. Each [LnO8] polyhedron is linked with two other [LnO8] polyhedra and four [LnO9] polyhedra via the edges.10 The functional properties of layered hydroxides are strictly dictated by the nature of the intercalated anions. To the best of our knowledge, until now, only a few classes of anions have been successfully intercalated in the interlayer space of LRHs © 2017 American Chemical Society
and LDHs. The geometrical dimensions and nature of the guest ions are of special importance in determining the distance between the layers. Crucial factors that should be considered are the number of guest layers (monolayer, bilayer) and the size and orientation of the guest ions, as well as the interactions between the negatively charged guest and positively charged host. Currently, the anions that can be intercalated into the interlayer space of LRHs belong to the following classes: (1) Simple inorganic anions: Cl−,11 Br−,12 I−,13 NO3−,14,15 SO42−,16 (CrO4)2−,17 ClO3−,13 MoO42−.18 (2) Polyoxoanions: Mo7O246−,18 [H2W12O42]10−.19 (3) Organic anions: oleate,20 aliphatic sulfates,21 aliphatic sulfonates,21 aliphatic carboxylates22 and dicarboxylates,14 anions of amino acids,23 aromatic acids,24,25 and others.26 (4) Metal−organic complex anions: carboxyethyl-substituted aza-crown ether coordinated with various cations,27 Pd complex with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS),28 rare-earth complexes with 2,2′-(4(2-ethoxyethoxy)pyridine-2,6-diyl)bis(4,5-dihydrooxazole) and picolinic acid.29 The majority of the above-mentioned anions have been successfully intercalated in the LDH structure, and general rules, which define the possibility of anion integration within the structure of these compounds, have been established.30,31 Plotting of ion-exchange isotherms between LDHs and Received: December 4, 2016 Published: March 3, 2017 3421
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry
Synthesis of Y2(OH)5Cl·xH2O (Cl-LYH) and Y2(OH)5NO3·xH2O (N-LYH). Caution! Although no problems were encountered in conducting the synthesis at 140 °C, one should always avoid overpressure and explosion of the autoclave, so the temperature of the hydrothermal treatment, and the f illing coeff icient, must be minded. Tef lon autoclaves used are not suitable for heating above 220 °C. Caution! Hexamethylenetetramine may cause irritation of the skin, eyes, mucous membranes and upper respiratory tract. This substance is also f lammable−any contact with a direct f lame must be avoided. Although very small quantities of hexamethylenetetramine were used in this study, thorough laboratory safety protocols were strictly followed while handling this compound. The starting aqueous solution of yttrium chloride was prepared by dissolving yttrium oxide in a stoichiometric amount of hot hydrochloric acid. In a typical experiment, 10 mL of 0.1 M YCl3 or Y(NO3)3 aqueous solution was added to 20 mL of an aqueous solution containing NaCl (or NaNO3) and hexamethylenetetramine (HMT), to give a reaction mixture of a desired concentration (cY3+ = 0.033 M, CNaCl/NaNO3 = 0.33 M, CHMT = 0.048 M). The reaction mixture was placed in 100 mL polytetrafluoroethylene autoclaves (with a filling coefficient of ∼30%) and subjected to microwave−hydrothermal (MWHT) treatment in a Berghof Speedwave MWS Four setup at 140 °C for 30 min. The heating rate at the non-isothermal stage was 30 °C/min. After the synthesis was complete, the autoclaves were cooled in air. The solid products were isolated by sedimentation and further decantation and washed repeatedly with distilled water, followed by drying at 60 °C and ∼75% relative humidity (RH) for 24 h. Synthesis of Cl-LYH yielded 0.138 g (87%) of white powder (IR (ATR, ν cm−1): 3659 (w), 3577 (m), 3538 (s), 3389 (s), 3335 (s), 1658 (w), 1638 (w), 1520 (m), 1357 (m), 1110 (vw), 1045 (w), 865 (vw), 787 (vw), 725 (vw), 639 (vw)). Synthesis of N-LYH yielded 0.143 g (78%) of white powder (IR (ATR, ν cm−1): 3600 (s), 3300 (m), 1763 (vw), 1634 (m), 1411 (s), 1350 (s), 1052 (w), 818 (w), 700 (vw)). Anion-Exchange between Y2(OH)5NO3·xH2O and K2B12H12. In a typical experiment, 65 mg of Y2(OH)5NO3·xH2O powder was dispersed in 30 mL of 0.02 M K2B12H12 aqueous solution (molar ratio Y:K 2 B 12 H12 = 1:3.3). The anion-exchange reaction between Y2(OH)5NO3·xH2O and K2B12H12 was carried out at room temperature, with continuous stirring, for 24 h, or at 60 °C in a glass autoclave for 24 h. The resulting precipitates were collected by centrifugation, washed with deionized water and dried at 60 °C for 24 h. One-step synthesis of Y2(OH)6−x(B12H12)2x·yH2O (B-LYH). In a typical experiment, 10 mL of YCl3·6H2O aqueous solution was added to 20 mL of an aqueous solution containing K2B12H12 and HMT, to give a reaction mixture of a desired concentration (CYCl3 = 0.016 M, CK2B12H12 = 0.1 M, CHMT = 0.024 M). Solutions were placed in 100 mL polytetrafluoroethylene autoclaves (with a filling coefficient of ∼30%) and subjected to microwave−hydrothermal (MWHT) treatment in a Berghof Speedwave MWS Four setup at 140 °C for 30 min. The heating rate at the non-isothermal stage was 30 °C/min. After the synthesis was complete, the autoclaves were cooled in air. The solid products were isolated by sedimentation and further decantation, and washed repeatedly with distilled water, followed by drying at 60 °C for 24 h. The synthesis yielded 0.065 g (67%) of white powder. Inductively coupled plasma mass spectrometry (ICP MS) found: B 7.7 wt %; Y 44.9 wt %; IR (ATR, ν cm−1): 3564 (m), 3250 (w), 2484 (m), 2384 (w), 2350 (w), 1600 (w), 1062 (vw), 720 (m). Characterization. Powder X-ray diffraction (XRD) patterns of the obtained samples were collected on a Bruker D8 Advance diffractometer (Bragg−Brentano geometry) with Cu Kα radiation. The morphology of LRH samples was investigated using highresolution scanning electron microscopy (Carl Zeiss NVision 40 equipped with an Oxford Instruments X-Max EDX detector). Thermogravimetric and differential thermal (TGA/DTA) analyses were performed using a Pyris Diamond thermoanalyzer (Perkin− Elmer) in the temperature range of 20−1200 °C, at a heating rate of 10 °C/min in the air or argon gas. Boron and yttrium content was determined by using ICP MS on an iCAP 6300 Duo inductively coupled plasma−atomic emission spectrometer. IR spectra of the
different anions has enabled determination of the orders of anion affinities and selectivity.32,33 The formation of intercalated compounds can be considered within the Pearson’s hard and soft (Lewis) acids and bases (HSAB) theory. According to HSAB theory, most divalent and trivalent metal ions in LDHs (including Mg and Al) being hard Lewis acids34 should preferably interact with hard bases such as water, carboxylates, and fluoride- and chloride-ions. The same postulate could be applied to LRHs as well.27 In intercalated LRHs, the bonding/coordination of the rareearth atoms to the anionic guest (Lewis base) usually occurs via the lone electron pairs, although anions without nonbonding electron pairs should also interact with rare-earth centers of LRHs. Among the latter type of anions, the appropriate candidates to be intercalated in LRHs are boron cluster anions [BnHn]2−. Boron cluster anions [BnHn]2− (n = 6−12) represent one of the few examples of completely nonmetal clusters. The stability and chemical behavior of such systems depend significantly on the spatially aromatic nature of chemical bonds within them. The aromaticity of polyhedral boron anions gives rise to some specific properties, extrinsic for other boron hydrides, such as the high thermal stability of the host boron system and a strongly defined tendency to participate in substitution reactions.35,36 High nuclear cross section for neutron absorption and low atomic number make 10B a candidate of choice for neutron/ gamma irradiation discrimination.37 The combinations of boron compounds with rare-earth matrices possessing luminescent (Tb, Eu),38 magnetic (Dy),39 and/or neutron-capturing (Gd)40 properties open new opportunities for the design of sensoric or theranostic biomedical materials. So far, only some salts of closo-dodecaborate anions with rare-earth metal cations have been reported in the literature.41 The intercalation of closododecaborate anions in the interlayer space of layered hydroxides (LDHs or LRHs) has not yet been reported. In comparison with LDHs, LRHs have higher surface charge density (0.045 vs 0.040 e/Å2),10 and they are not readily intercalated in ambient conditions. In this case, a hydrothermal treatment at 50−150 °C can be applied.26,27,42,43 Another synthetic approach toward LRH-based hybrid compounds implies precipitation in the presence of an excess of the desired anion. This method affords fine crystalline compounds containing porphyrins,28 dodecylsulfate anions,44 and a number of carboxylate ions.45 In the present study, we attempted to intercalate a [B12H12]2− anion into the basal spacing of a layered yttrium hydroxide using both standard ion-exchange technique and one-pot microwave-assisted synthesis.46 As a result, a first member of a new family of closo-dodecaborate intercalated layered hydroxides was successfully synthesized, with a high yield, in a few minutes.
■
MATERIALS AND METHODS
Materials. Yttrium oxide (99.9%, Lanhit), yttrium nitrate hexahydrate (99.9%, Lanhit), hydrochloric acid (37 wt % in H2O, Sigma Tec), sodium chloride (99%, Chimmed), sodium nitrate (99%, Chimmed), and hexamethylenetetramine (99+%, Alfa Aesar) were used without further purification. Synthesis of K2B12H12. Caution! Several hazard notices are applicable, extensively indicated elsewhere.47 Potassium dodecahydro-closo-dodecaborate was obtained according to the previously reported procedure.47 The synthesis yielded 86% of white powder. IR (ATR, ν cm−1): 2477 (s), 1072 (s), 714 (m). 3422
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry
Figure 1. SEM images of (a) low-aggregated, plate-like crystals of layered yttrium hydroxochloride and (b) spheroidal aggregates of plate-like particles of layered yttrium hydroxonitrate, obtained by homogeneous precipitation under microwave-assisted hydrothermal treatment. obtained compounds were recorded on an ALPHA FTIR Spectrometer (Bruker) in the range of 4000−400 cm−1 with a resolution of 1 cm−1 in the attenuated total reflection mode. Photoelectron spectra (XPS) were obtained using PHI Quartera SXM Scanning X-ray Microprobe spectrometer with a ∼100 μm beam of monochromatic Al Kα radiation. Before measurement, the powders were compressed slightly into the sample holders, 5 mm in diameter and 0.5 mm in depth. A scanning area of ∼1400 × 1400 μm2 was chosen in the center of the sample. Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and electron energy loss spectroscopy (EELS) were conducted using a LEO 912 AB Omega energy-filtered transmission electron microscope.
composition of layered yttrium hydroxochloride as Y2(OH)5.16Cl0.84·1.37H2O, and yttrium hydroxonitrate Y2(OH)5.03(NO3)0.97·1.7H2O. According to scanning electron microscopy (SEM), yttrium hydroxochloride crystallized in the form of low-aggregated, plate-like particles, while hydroxonitrate formed spheroidal aggregates of plate-like particles (Figure 1), whose morphology has been reported earlier.48,49 The formation of such structures is believed to proceed via selfassembly of individual particles, as a result of their oriented attachment.50−52 The results of X-ray diffraction analysis indicated that anion exchange between Y2(OH)5NO3·xH2O and K2B12H12 did not occur, either at room temperature or at 60 °C. That is, the reaction scheme:
■
RESULTS AND DISCUSSION The synthesis of Cl-LYH and N-LYH was conducted according to our previously reported procedure46,48,49 and involved the following reactions:
Y2(OH)5 X·nH 2O + B12H12 2 − → Y2(OH)5 (B12H12)0.5 ·nH 2O + X−
Δ
C6N4H12 + 6H 2O → 6H 2CO + 4NH3
(1)
could not be accomplished. X-ray diffraction patterns (Figure S5, Supporting Information) of yttrium hydroxonitrate, before and after conditioning in K2B12H12 solution at different temperatures, showed that the {00l} series reflections shifts typical for anion exchange products did not occur. It is noteworthy that, in the case of yttrium hydroxochloride, ion exchange in the sodium dodecyl sulfate solution proceeded at room temperature in several minutes (Figure S6, Supporting Information). Such differences in behavior might have been caused by both the difference in size and charge of anions (contribution to Coulomb interaction), and the difference in donor−acceptor properties (formation of coordination or hydrogen bonds). Presumably, both causes were involved, but with different relations. Thus, for LDHs, the ion exchange constant has been reported to decrease with the increase in size, for a series of single-charged ions: OH− (133 pm), F− (133 pm), Cl− (184 pm), Br− (196 pm), and I− (220 pm), while an increase of charge in the case of CO32−, SO42−, and C10H4SN2O82− (Naphthol yellow S) has led to a sharp increase in the ion exchange constant value.32 High values of equilibrium constants for C10H4SN2O82− and dodecyl sulfate anions might be explained by the small size of ions, at least in one dimension, as against B12H122−. However, the values of ion exchange equilibrium constants might vary significantly, even for anions of very similar size and shape, for example, for oleate- and dodecyl sulfate anions. By comparison, the ion exchange reaction of nitrate-intercalated layered yttrium hydroxide with dodecyl sulfate proceeded at room temperature within several minutes,46 while the intercalation of oleate
2YX3 + 5NH3 + (n + 5)H 2O → Y2(OH)5 X ·nH 2O + 5NH4X
(3)
(2)
where, X = NO3, Cl. The X-ray diffraction experiments (Figure S1, Supporting Information) provided evidence of the formation of layered yttrium hydroxochloride/hydroxonitrate as a result of the homogeneous hydrolysis of yttrium chloride in the presence of NaCl/NaNO3 under microwave-assisted hydrothermal treatment. According to Sasaki et al.,8,10 layered rare-earth hydroxochlorides crystallize in the orthorhombic system (P21212 group). The unit cell parameters of orthorhombic Cl-LYH were determined using the Le Bail intensity extraction method. The experimental, calculated, and difference patterns are shown in Supporting Information (Figure S2). The final R factors were GOF = 1.75, Rp = 3.04, and wRp = 4.11. Calculated unit cell parameters a = 12.686(3) Å, b = 7.160(2) Å, c = 8.437(5) Å corresponded well with previously reported data for Cl-LYH (a = 12.6600(1) Å, b = 7.1431(1) Å, c = 8.4209(3) Å).12 SAED pattern (Figure S3, Supporting Information) of Cl-LYH was in good agreement with the data previously reported by Sasaki et al.8 In the case of the disordered pseudohexagonal structure of N-LYH, the unit cell parameters could only be roughly estimated: a = 12.7(3) Å, b = 7.1(0) Å, c = 18.2(4) Å.46 The formation of layered yttrium hydroxochloride/hydroxonitrate phases was well-supported by the results of TGA (Figure S4, Supporting Information), which established the 3423
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry
which amounts to ∼5.5 Å, according to X-ray diffraction data for K2B12H12.54 One should mention that the reflections of a layered compound obtained in the presence of K2B12H12 demonstrated significant broadening in comparison with analogous reflections of layered Cl-LYH and N-LYH phases. According to estimations deduced from XRD data using Williamson−Hall plotting,55 B-LYH crystallites had the sizes of ∼6 nm (4 nm along 001 direction and 12 nm along the 110 direction), and no crystal strain was revealed. SEM analysis indicated that the BLYH phase consisted of aggregates of fused, plate-like particles that were less than 10 nm thick (Figure 3). TEM analysis also showed the formation of very thin particles of the B-LYH phase (see Figure 4), containing roundish defects 10−20 nm in diameter. SAED data indicated only two broad reflections corresponding to interplanar distances of 2.8 and 1.9 Å. This could be evidence of the disordering of the layered structure of the B-LYH phase. The formation of an yttrium compound with high boron content was confirmed by the EELS and elemental analysis. The B K-shell excitation spectra of the B-LYH showed 1s→π* (193 eV) and 1s→σ* (∼200 eV) transitions characteristic of boron atoms (Figure S7, Supporting Information).56 The content of yttrium and boron in B-LYH was found to be 44.9 and 7.7 wt %, respectively, corresponding to molar ratios of Y/ B = 1:1.4 (0.72) and Y/B12H12 = 1:0.12 (8.33), with, on average, one B12H122− anion on each unit cell of B-LYH. The ratio of Y/Cl amounted to 25:1, based on the results of an energy-dispersive X-ray investigation. Consequently, the composition of B-LYH was established as Y2(OH)5.46(B12H12)0.23Cl0.08·4.98H2O. The closo-dodecaborate salts with thermally stable cations have demonstrated a high thermal stability. For example, Cs2[B12H12] has not changed its composition upon heating to 810 °C.41 The results of the K2B12H12 thermal analysis (Figure 5) suggested no significant mass change in the sample, up to 900 °C. The weight loss curves for Cl-LYH and B-LYH indicated the presence of two decomposition stages up to 500 °C, associated with the removal of physically bound water from the interlayer space (∼110 °C) and the removal of chemically bound water (∼300 °C), which was accompanied by the destruction of the layered structure and the formation of an oxide phase. When heated above 500 °C, the weight-loss curve for B-LYH showed a weight increase, which may be attributed to the oxidation of the B12H122− anion by air oxygen inside the oxide matrix. This also confirmed the formation of an LYH structure intercalated with B12H122− anions. Discrepancies in the values for water content in B-LYH, as obtained by thermal analysis (1.2H2O) and elemental analysis (2.48H2O), as well as the oxidation of B12H122− at 500 °C, could be explained by an assumption that, in the course of B-LYH synthesis, the B12H122− anion transformed into a B12H(12−n)OHn2− anion. For example, the B12H12−2 anion in a dilute aqueous solution under hydrothermal treatment (150 °C) has been shown to convert into B12H11OH2−.41 Y 3d photoelectron spectra were interpreted considering both NIST data and previously reported results.57−60 Analysis of core-level Y 3d high-resolution spectra (Y 3d3/2 and Y 3d5/2 spin−orbit components) in the 154−164 eV region showed that a reliable difference in binding energy values for the ClLYH and B-LYH samples is observed (see Figure S8, Supporting Information). Y 3d core levels for closo-dodecaborate intercalated layered yttrium hydroxide shifted (ca. 0.5
anions required hydrothermal treatment.53 Such behavior can be explained in the context of donor−acceptor properties of anions within Pearson’s HSAB theory. According to Pearson’s theory, the absence (low rate) of anion exchange between LYH and the aqueous solution of K2B12H12 accounts for the fact that B12H122− is a soft Lewis acid. Furthermore, it seems difficult to introduce a bulky B12H122− ion into an LRH structure, assuming that LRH’s anion exchange proceeds by a topotactic mechanism.30 However, presuming the reported formation of complexes of rare-earth metal cations with borates41 and the high charge of the anion B12H122−, one can expect the existence of the corresponding intercalated compounds, whose synthesis is described in the following section. One-Pot Synthesis. Among other efficient methods of anion introduction into the layered hydroxides structure, one should mention one-pot synthesis of intercalated LRHs in excess of the chosen anion. This approach overcomes limitations on the size of anion and its donor−acceptor properties. The use of this method made it possible to obtain the layered yttrium hydroxide intercalated with the B12H122− anion according to the scheme ⎛ 1 ⎞ 5 1 C6N4H12 + ⎜12 + n⎟H 2O + B12H12 2 − ⎝ ⎠ 4 2 2 Δ 1 → Y2(OH)5 (B12H12)0.5 ·nH 2O + 7 H 2CO + 5NH4 + 2
2Y3 + +
(4)
According to X-ray diffraction data (Figure 2), during the synthesis of layered yttrium hydroxide in the presence of
Figure 2. X-ray diffraction patterns for the products of hydrothermalmicrowave treatment of the reaction mixtures containing HMT, yttrium chloride and (a) K2B12H12, (b) NaNO3, (c) NaCl.
K2B12H12, a layered phase was formed with intense basal {00l} diffraction reflection series (d001 = 11.0 Å, d002 = 5.7 Å, d003 = 3.8 Å). The 001 reflection corresponds to basal spacing d = 11 Å, (while for yttrium hydroxochloride d = 8.3 Å). This value could be used to estimate interlayer distance, on the basis of the average thickness of the metal-hydroxide layer, which amounted to ∼5.5 Å:8,10 dinterlayer = 11−5.5 = 5.5 Å. The value obtained was in good agreement with the diameter of a B12H122− ion, 3424
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry
Figure 3. SEM images of fused, plate-like crystals (thickness ∼10 nm) of layered boron-containing compound synthesized by hydrothermalmicrowave treatment of reaction mixtures containing HMT, yttrium chloride, and K2B12H12.
Figure 4. TEM (a) and SAED (b) images of plate-like crystals of layered boron-containing compound synthesized by hydrothermal-microwave treatment of the solution containing HMT, yttrium chloride, and K2B12H12.
Figure 5. Weight loss curves (a−c) and their first derivatives (d−f), for samples Cl-LYH (a, d), K2B12H12 (b, e), and B-LYH (c, f).
dodecaborate intercalated layered yttrium hydroxide to higher binding energy, compared with yttrium hydroxide chloride (see Figure S8, Supporting Information). There was no detectable shift in boron binding energy upon intercalation of closododecaborate anions between yttruim hydroxide host layers: B 1s binding energy was 187.3 and 187.5 eV, for K2B12H12 and closo-dodecaborate intercalated layered yttrium hydroxide, respectively.
eV) to higher binding energy, compared with yttrium hydroxide chloride (157.8 and 157.3 eV, respectively, for 3d5/2). We found that the direct coordination of [B12H12]2− with yttrium ions was most probably absent, and the interaction between yttrium hydroxide host layers and [B12H12]2− could have been primarily due to dihydrogen bonding between hydrogen atoms linked with boron and hydroxyl groups linked with an yttrium ion (B12H11−H···HO−Y).61−63 This supposition was confirmed also by the ∼0.5 eV shift in O 1s core levels for closo3425
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry
Hydroxides Rigidly Pillared by Sulfate Ions. Chem. Mater. 2010, 22, 6001−6007. (4) Wang, Z.; Li, J.-G.; Zhu, Q.; Li, X.; Sun, X. Sacrificial Conversion of Layered Rare-Earth Hydroxide (LRH) Nanosheets into (Y1−xEux)PO4 Nanophosphors and Investigation of Photoluminescence. Dalt. Trans. 2016, 45, 5290−5299. (5) Wang, L.; Yan, D.; Qin, S.; Li, S.; Lu, J.; Evans, D. G.; Duan, X. Tunable Compositions and Luminescent Performances on Members of the Layered Rare-Earth Hydroxides (Y1‑xLnx)2(OH)5NO3·nH2O (Ln = Tb, Eu). Dalt. Trans 2011, 40, 11781−11787. (6) Gu, Q.; Chen, W.; Duan, F.; Ju, R. Fabrication of a Nano-Drug Delivery System Based on Layered Rare-Earth Hydroxides Integrating Drug-Loading and Fluorescence Properties. Dalt. Trans. 2016, 45, 12137−12143. (7) Wu, X.; Li, J. G.; Zhu, Q.; Li, J.; Ma, R.; Sasaki, T.; Li, X.; Sun, X.; Sakka, Y. The Effects of Gd3+ Substitution on the Crystal Structure, Site Symmetry, and Photoluminescence of Y/Eu Layered Rare-Earth Hydroxide (LRH) Nanoplates. Dalt. Trans 2012, 41, 1854−1861. (8) Geng, F.; Xin, H.; Matsushita, Y.; Ma, R.; Tanaka, M.; Izumi, F.; Iyi, N.; Sasaki, T. New Layered Rare-Earth Hydroxides with AnionExchange Properties. Chem. - Eur. J. 2008, 14, 9255−9260. (9) Newman, S. P.; Jones, W. Synthesis, Characterization and Applications of Layered Double Hydroxides Containing Organic Guests. New J. Chem. 1998, 22, 105−115. (10) Geng, F.; Matsushita, Y.; Ma, R.; Xin, H.; Tanaka, M.; Izumi, F.; Iyi, N.; Sasaki, T. General Synthesis and Structural Evolution of a Layered Family of Ln8(OH)20Cl4·nH2O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y). J. Am. Chem. Soc. 2008, 130, 16344−16350. (11) Hu, L.; Ma, R.; Ozawa, T. C.; Sasaki, T. Synthesis of a Solid Solution Series of Layered EuxGd1‑x(OH)2.5Cl0.5·0.9H2O and Its Transformation into (EuxGd1‑x)2O3 with Enhanced Photoluminescence Properties. Inorg. Chem. 2010, 49, 2960−2968. (12) Poudret, L.; Prior, T. J.; McIntyre, L. J.; Fogg, A. M. Synthesis and Crystal Structures of New Lanthanide Hydroxyhalide Anion Exchange Materials, Ln2(OH)5X·1.5H2O (X = Cl, Br; Ln = Y, Dy, Er, Yb). Chem. Mater. 2008, 20, 7447−7453. (13) Kim, H.; Lee, B.-I.; Jeong, H.; Byeon, S.-H. Relationship between Interlayer Anions and Photoluminescence of Layered Rare Earth Hydroxides. J. Mater. Chem. C 2015, 3, 7437−7445. (14) McIntyre, L. J.; Jackson, L. K.; Fogg, A. M. Ln2(OH)5NO3· xH2O (Ln = Y, Gd−Lu): A Novel Family of Anion Exchange Intercalation Hosts. Chem. Mater. 2008, 20, 335−340. (15) Frolova, E. A.; Kondakov, D. F.; Yapryntsev, A. D.; Baranchikov, A. E.; Ivanov, V. K.; Danilov, V. P. Synthesis of Basic Yttrium Nitrate. Russ. J. Inorg. Chem. 2015, 60, 259−264. (16) Geng, F.; Ma, R.; Matsushita, Y.; Liang, J.; Michiue, Y.; Sasaki, T. Structural Study of a Series of Layered Rare-Earth Hydroxide Sulfates. Inorg. Chem. 2011, 50, 6667−6672. (17) Kim, H.; Lee, B. I.; Byeon, S. H. The Inner Filter Effect of Cr(VI) on Tb-Doped Layered Rare Earth Hydroxychlorides: New Fluorescent Adsorbents for the Simple Detection of Cr(VI). Chem. Commun. 2015, 51, 725−728. (18) Lee, B. I.; Byeon, S. H. Highly Enhanced Photoluminescence of a Rose-like Hierarchical Superstructure Prepared by Self-Assembly of Rare-Earth Hydroxocation Nanosheets and Polyoxomolybdate Anions. Chem. Commun. 2011, 47, 4093−4095. (19) Jeong, H.; Lee, B.-I.; Byeon, S.-H. Directional Self-Assembly of Rare-Earth Hydroxocation Nanosheets and Paradodecatungstate Anions. Dalt. Trans. 2012, 41, 14055. (20) Lee, B.-I. B. Il; Bae, J. S. J.-S.; Lee, E.-S. E. S.; Byeon, S.-H. S. H. Synthesis and Photoluminescence of Colloidal Solution Containing Layered Rare-Earth Hydroxide Nanosheets. Bull. Korean Chem. Soc. 2012, 33, 601−607. (21) Lee, K.-H.; Byeon, S.-H. Extended Members of the Layered Rare-Earth Hydroxide Family, RE2(OH)5NO3·nH2O (RE = Sm, Eu, and Gd): Synthesis and Anion-Exchange Behavior. Eur. J. Inorg. Chem. 2009, 2009, 929−936.
The results of IR spectroscopy of the B-LYH sample (Table S1, Supporting Information) indicated the presence of B−H valence and “cage” vibrations of B12H122−,41 together with OHvibrations typical of layered hydroxides.46 The intensity decrease of “cage” vibrations at 1062, 1023 cm−1 of B-LYH, in comparison with K2B12H12, was attributed to a polarization of the B12 cage.41 This suggests the interaction of closododecaborate anion with yttrium hydroxide host layers, while the splitting of the B−H valence vibration peak (2484, 2384 and 2350 cm−1) of B-LYH (in comparison with 2477 cm−1 of K2B12H12) provided additional evidence of the formation of dihydrogen bonds between host layers and B12H122− anions.64
■
CONCLUSIONS A new approach to the design of boron-containing solid-state materials was developed, based on the intercalation of closododecaborate anion [B12H12]2− into the interlayer space of layered hydroxides. The first member of rare-earth metals layered hydroxo-complexes, closo-dodecaborate intercalated yttrium hydroxide, was obtained using one-step, microwaveassisted hydrothermal synthesis. The title compound had the composition Y2(OH)5.46(B12H12)0.23Cl0.08·4.98H2O and crystallized in a form of plate-like, aggregated particles less than 10 nm thick. The coordination of closo-dodecaborate anions with yttrium hydroxide host layers was demonstrated.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b02948. The experimental, calculated and differential X-ray diffraction patterns. Thermal analysis data. XPS survey and high resolution Y 3d and B 1s spectra. EELS spectra. IR band assignment table (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Vladimir K. Ivanov: 0000-0003-2343-2140 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was supported by the Russian Foundation for Basic Research (Project No. 14-03-00907) and GOVT (Ministry of Education and Science of the Russian Federation), according to the Grant No.14.595.21.0001 (Unique Identifier RFMEFI59514 × 0001).
■
REFERENCES
(1) Haschke, J. M. Preparation, Phase Equilibriums, Crystal Chemistry, and Some Properties of Lanthanide Hydroxide Nitrates. Inorg. Chem. 1974, 13, 1812−1818. (2) Gándara, F.; Perles, J.; Snejko, N.; Iglesias, M.; Gómez-Lor, B.; Gutiérrez-Puebla, E.; Monge, M. Á . Layered Rare-Earth Hydroxides: A Class of Pillared Crystalline Compounds for Intercalation Chemistry. Angew. Chem., Int. Ed. 2006, 45, 7998−8001. (3) Liang, J.; Ma, R.; Geng, F.; Ebina, Y.; Sasaki, T. Ln2(OH)4SO4· nH2O (Ln = Pr to Tb; n ∼ 2): A New Family of Layered Rare-Earth 3426
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry (22) Lee, K.-H.; Byeon, S.-H. Synthesis and Aqueous Colloidal Solutions of RE2(OH)5NO3·nH2O (RE = Nd and La). Eur. J. Inorg. Chem. 2009, 2009, 4727−4732. (23) Gu, Q.; Sun, Y.; Chu, N.; Ma, S.; Jia, Z.; Yang, X. Intercalation of Amino Acids into Eu3+-Doped Layered Gadolinium Hydroxide and Quenching of Eu3+Luminescence. Eur. J. Inorg. Chem. 2012, 2012, 4407−4412. (24) Gu, Q.; Pan, G.; Ma, T.; Huang, G.; Sun, G.; Ma, S.; Yang, X. Eu3+ Luminescence Enhancement by Intercalation of Benzenepolycarboxylic Guests into Eu3+-Doped Layered Gadolinium Hydroxide. Mater. Res. Bull. 2014, 53, 234−239. (25) Chu, N.; Sun, Y.; Zhao, Y.; Li, X.; Sun, G.; Ma, S.; Yang, X. Intercalation of Organic Sensitisers into Layered Europium Hydroxide and Enhanced Luminescence Property. Dalt. Trans 2012, 41, 7409− 7414. (26) Liu, L.; Wang, Q.; Gao, C.; Chen, H.; Liu, W.; Tang, Y. Dramatically Enhanced Luminescence of Layered Terbium Hydroxides as Induced by the Synergistic Effect of Gd3+and Organic Sensitizers. J. Phys. Chem. C 2014, 118, 14511−14520. (27) Li, W.; Gu, Q.; Su, F.; Sun, Y.; Sun, G.; Ma, S.; Yang, X. Intercalation of Azamacrocyclic Crown Ether into Layered Rare-Earth Hydroxide (LRH): Secondary Host-Guest Reaction and Efficient Heavy Metal Removal. Inorg. Chem. 2013, 52, 14010−14017. (28) Demel, J.; Kubat, P.; Millange, F.; Marrot, J.; Cisarova, I.; Lang, K. Lanthanide-Porphyrin Hybrids: From Layered Structures to MetalOrganic Frameworks with Photophysical Properties. Inorg. Chem. 2013, 52, 2779−2786. (29) Shen, T.; Zhang, Y.; Liu, W.; Tang, Y. Novel Multi-Color Photoluminescence Emission Phosphors Developed by Layered Gadolinium Hydroxide via in Situ Intercalation with Positively Charged Rare-Earth Complexes. J. Mater. Chem. C 2015, 3, 1807− 1816. (30) Radha, A. V.; Vishnu Kamath, P.; Shivakumara, C. Mechanism of the Anion Exchange Reactions of the Layered Double Hydroxides (LDHs) of Ca and Mg with Al. Solid State Sci. 2005, 7, 1180−1187. (31) Costantino, U.; Vivani, R.; Bastianini, M.; Costantino, F.; Nocchetti, M. Ion Exchange and Intercalation Properties of Layered Double Hydroxides towards Halide Anions. Dalt. Trans. 2014, 43, 11587. (32) Miyata, S. Anion-Exchange Properties of Hydrotalcite-Like Compounds. Clays Clay Miner. 1983, 31, 305−311. (33) Theiss, F. L.; Ayoko, G. A.; Frost, R. L. Removal of Boron Species by Layered Double Hydroxides: A Review. J. Colloid Interface Sci. 2013, 402, 114−121. (34) Wang, L.; Wang, F.; Xu, L. Layered Double Hydroxides Based on Different Cations as Catalysts for Synthesis of poly(1, 5-Pentadiol) Carbonate Diols. Indian J. Chem. 2015, 54, 607−612. (35) Kuznetsov, N. Reactivity of Polyhedral Cluster Anions BnHn2− (n = 10, 12) as Spatial Aromatic Systems. Russ. J. Inorg. Chem. 2002, 47, S68−S104. (36) Kuznetsov, N.; Ionov, S.; Solntsev, K. Razvitiye Kontseptsii Aromatichnosti. Poliedricheskiye Struktury; Nauka: Moscow, Russia, 2009. (In Russian). (37) Bertrand, G. H. V.; Hamel, M.; Sguerra, F. Current Status on Plastic Scintillators Modifications. Chem. - Eur. J. 2014, 20, 15660− 15685. (38) Liu, L.; Yu, M.; Zhang, J.; Wang, B.; Liu, W.; Tang, Y. Facile Fabrication of Color-Tunable and White Light Emitting NanoComposite Films Based on Layered Rare-Earth Hydroxides. J. Mater. Chem. C 2015, 3, 2326−2333. (39) Monteiro, B.; Coutinho, J. T.; Pereira, C. C. L.; Pereira, L. C. J.; Marçalo, J.; Almeida, M.; Baldoví, J. J.; Coronado, E.; Gaita-Ariño, A. Magnetic Properties of the Layered Lanthanide Hydroxide Series YxDy8‑x(OH)20Cl4·6H2O: From Single Ion Magnets to 2D and 3D Interaction Effects. Inorg. Chem. 2015, 54, 1949−1957. (40) Stefanakis, D.; Ghanotakis, D. F. Synthesis and Characterization of Gadolinium Nanostructured Materials with Potential Applications in Magnetic Resonance Imaging, Neutron-Capture Therapy and Targeted Drug Delivery. J. Nanopart. Res. 2010, 12, 1285−1297.
(41) Muetterties, E. L.; Balthis, J. H.; Chia, Y. T.; Knoth, W. H.; Miller, H. C. Chemistry of Boranes. VIII. Salts and Acids of B10H10−2 and B12H12−2. Inorg. Chem. 1964, 3, 444−451. (42) Zhu, Q.; Xu, Z.; Li, J.-G.; Li, X.; Qi, Y.; Sun, X. HydrothermalAssisted Exfoliation of Y/Tb/Eu Ternary Layered Rare-Earth Hydroxides into Tens of Micron-Sized Unilamellar Nanosheets for Highly Oriented and Color-Tunable Nano-Phosphor Films. Nanoscale Res. Lett. 2015, 10, 132. (43) Sun, Y.; Chu, N.; Gu, Q.; Pan, G.; Sun, G.; Ma, S.; Yang, X. Hybrid of Europium-Doped Layered Yttrium Hydroxide and Organic Sensitizer - Effect of Solvent on Structure and Luminescence Behavior. Eur. J. Inorg. Chem. 2013, 2013, 32−38. (44) Zhao, Y.; Li, J.-G.; Guo, M.; Yang, X. Structural and Photoluminescent Investigation of LTbH/LEuH Nanosheets and Their Color-Tunable Colloidal Hybrids. J. Mater. Chem. C 2013, 1, 3584. (45) Watanabe, M.; Fujihara, S. One-Step Synthesis of Layered Yttrium Hydroxides in Immiscible Liquid−liquid Systems: Intercalation of Sterically-Bulky Hydrophobic Organic Anions and Doping of Europium Ions. J. Solid State Chem. 2014, 210, 130−137. (46) Yapryntsev, A. D.; Baranchikov, A. E.; Skogareva, L. S.; Goldt, A. E.; Stolyarov, I. P.; Ivanova, O. S.; Kozik, V. V.; Ivanov, V. K. HighYield Microwave Synthesis of Layered Y2(OH)5NO3·xH2O Materials. CrystEngComm 2015, 17, 2667−2674. (47) Miller, H. C.; Muetterties, E. L.; Boone, J. L.; Garrett, P.; Hawthorne, M. F. Borane Anions. In Inorganic Syntheses; McGrawHill: New York, 1967; Vol. 10, pp 81−91. (48) Yapryntsev, A.; Baranchikov, A.; Goldt, A.; Ivanov, V. Microwave-Assisted Hydrothermal Synthesis of Layered Europium Hydroxynynitrate, Eu2(OH)5NO3•xH2O. Curr. Microw. Chem. 2016, 3, 3−8. (49) Yapryntsev, A. D.; Baranchikov, A. E.; Zabolotskaya, A. V.; Borilo, L. P.; Ivanov, V. K. Synthesis of Gadolinium Hydroxo Nitrate under Microwave-Hydrothermal Treatment Conditions. Russ. J. Inorg. Chem. 2014, 59, 1383−1391. (50) Fedorov, P. P.; Ivanov, V. K. Cooperative Formation of Crystals by Aggregation and Intergrowth of Nanoparticles. Dokl. Phys. 2011, 56, 205−207. (51) Banfield, J. F.; Welch, S. A.; Zhang, H.; Ebert, T. T.; Penn, R. L. Aggregation-Based Crystal Growth and Microstructure Development in Natural Iron Oxyhydroxide Biomineralization Products. Science 2000, 289, 751−754. (52) Ivanov, V. K.; Baranchikov, A. Y.; Osiko, V. V.; Fedorov, P. P. Oriented Aggregation of Particles: 100 Years of Investigations of NonClassical Crystal Growth. Russ. Chem. Rev. 2014, 83, 1204−1222. (53) Zhu, Q.; Li, X. D.; Sun, X. D.; Li, J. G. Ultra-Large Unilamellar Nanosheets Efficiently Exfoliated from (Y0.95Eu0.05)2(OH)5NO3·nH2O and Their Self-Assembly into Oriented Oxide Film with Enhanced Photoluminescence Properties. Key Eng. Mater. 2014, 602−603, 1017−1020. (54) Wunderlich, J. A.; Lipscomb, W. N. Structure of B12H12−2 ION. J. Am. Chem. Soc. 1960, 82, 4427−4428. (55) Powder Diffraction; Dinnebier, R. E., Billinge, S. J. L., Eds.; Royal Society of Chemistry: Cambridge, England, 2008. (56) Meller, A. B Boron Compounds; Faust, J., Niedenzu, K., Eds.; Springer Berlin Heidelberg: Berlin, Germany, 1991. (57) Uwamino, Y.; Ishizuka, T.; Yamatera, H. X-Ray Photoelectron Spectroscopy of Rare-Earth Compounds. J. Electron Spectrosc. Relat. Phenom. 1984, 34, 67−78. (58) Vasquez, R. P. XPS Core Level Spectra of Some Y Compounds. J. Electron Spectrosc. Relat. Phenom. 1990, 50, 167−170. (59) Simon, V.; Eniu, D.; Takács, A.; Magyari, K.; Neumann, M.; Simon, S. X-Ray Photoemission Study of Yttrium Contained in Radiotherapy Systems. J. Optoelectron. Adv. Mater. 2005, 7, 2853− 2857. (60) Ulrich, M. D.; Rowe, J. E.; Niu, D.; Parsons, G. N. Bonding and Structure of Ultrathin Yttrium Oxide Films for Si Field Effect Transistor Gate Dielectric Applications. J. Vac. Sci. Technol., B: Microelectron. Process. Phenom. 2003, 21, 1792. 3427
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
Article
Inorganic Chemistry (61) Alcock, N. W. Adv. Inorg. Chem. Radiochem. 1972, 15, 1−58. (62) Belkova, N. V.; Epstein, L. M.; Filippov, O. A.; Shubina, E. S. Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides. Chem. Rev. 2016, 116, 8545−8587. (63) Malinina, E. A.; Avdeeva, V. V.; Goeva, L. V.; Polyakova, I. N.; Kuznetsov, N. T. Specific Interactions in Metal Salts and Complexes with Cluster Boron Anions BnHn2− (n = 6, 10, 12). Russ. J. Inorg. Chem. 2011, 56, 687−697. (64) Shubina, E. S.; Tikhonova, I. A.; Bakhmutova, E. V.; Dolgushin, F. M.; Antipin, M. Y.; Bakhmutov, V. I.; Sivaev, I. B.; Teplitskaya, L. N.; Chizhevsky, I. T.; Pisareva, I. V.; Bregadze, V. I.; Epstein, L. M.; Shur, V. B. Crown Compounds for Anions: Sandwich and HalfSandwich Complexes of Cyclic Trimeric Perfluoro-O-Phenylenemercury with Polyhedralcloso-[B10H10]2− Andcloso-[B12H12]2− Anions. Chem. - Eur. J. 2001, 7, 3783−3790.
3428
DOI: 10.1021/acs.inorgchem.6b02948 Inorg. Chem. 2017, 56, 3421−3428
