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Article

A Series of Lanthanide Complexes with Keggin-Type Monolacunary Phosphotungstate: Synthesis and Structural Characterization

by
Vladimir S. Korenev
*,
Taisiya S. Sukhikh
and
Maxim N. Sokolov
Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Lavrentieva St. 3, 630090 Novosibirsk, Russia
*
Author to whom correspondence should be addressed.
Inorganics 2023, 11(8), 327; https://doi.org/10.3390/inorganics11080327
Submission received: 30 June 2023 / Revised: 27 July 2023 / Accepted: 27 July 2023 / Published: 1 August 2023
(This article belongs to the Special Issue Advances in Polyoxometalates for Supramolecular Architecture, Biomimetics and Bioapplications)
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Abstract

:
The coordination of rare-earth metal ions (Ln3+) to polyoxometalates (POM) is regarded as a way of modifying and controlling their properties, such as single-molecular magnetism or luminescent behavior. The half-sandwich complexes of Ln3+ with monolacunary Keggin POMs (Ln3+/POM = 1:1) are of particular interest, since the Ln3+ retains its ability to coordinate extra ligands. Thus, the knowledge of the exact structures of 1:1 Ln/POM complexes is important for the development of reliable synthetic protocols for hybrid complexes. In this work, we isolated three 1:1 Gd3+/POM complexes of the general formula Cat4Gd(PW11O39)·xH2O (Cat = K+ or Me4N+). Complex (Me4N)2K2[Gd(H2O)2PW11O39]·5H2O (1) is polymeric, revealing a layered structural motif via bridging Gd3+ and K+ ions. Complexes (Me4N)6K2[Gd(H2O)3PW11O39]2·20H2O (2) and (Me4N)7K[Gd(H2O)3PW11O39]2·12H2O (3) are classified as dimeric; the difference between them consists of the different crystal packing of the polyoxometalates, which is induced by a variation in the cationic composition. Isostructural complexes have also been characterized for praseodymium, europium, terbium and dysprosium. The coordination number of Ln3+ (8) persists in all the compounds, while the binding mode of the POM varies, giving rise to different architectures with two or three H2O co-ligands per Ln3+. However, whatever the particular structure and exact composition, the {Ln(PW11O39)} moieties are always involved in bonding with each other with the formation either of polymeric chains or dimeric units. In water, these aggregates can dissociate with the formation of [Ln(H2O)4PW11O39]4-. This behavior must be taken into account when choosing L for the design of hybrid {Ln(L)POM} complexes.

Graphical Abstract

1. Introduction

The class of polyoxometalates (POMs) is characterized by great structural diversity with a small number of stable, well-studied structural types [1,2,3]. Heterometallic derivatives of POMs obtained for a large number of chemical elements with different electronic configurations exhibit various electronic [4,5], magnetic [6,7,8,9,10], catalytic [11,12,13,14], optical [15], or other useful properties [16,17]. The wide possibilities of modification determine POM applicability in such areas as biology and medicine, electrochemistry, materials and surface sciences, solar energy conversion, etc. [18,19,20,21]. It has been shown that almost all transition and non-transition metals can be included in the vacancy of lacunary Keggin-type POMs, which are the most common [22].
The combination of polyoxometalates with lanthanide (Ln) ions is also interesting from the point of view of unique functional properties, such as, for example, luminescence [23]. One of the principles for the formation of new functional materials is the binding of POM fragments through the Ln ions due to their large coordination numbers, resulting in solid-state oligomers [24,25] and large ring structures [26,27]. POMs can serve as connectors and transfer agents for different monolacunary POMs [28].
A lot of different lanthanide complexes with the monovacant Keggin-type anion, [PW11O39]7–, have been well studied to date. These Ln-POMs can be divided into several structurally determined types. First of all, there are the monomeric species containing only one polyoxometalate unit. A series of chromophore-Ln-POMs [N(CH3)4]3K2[Ln(C7H5O2)(H2O)2(PW11O39)]·11H2O (Ln = Eu, Tb, Tm, Lu) was prepared using LnCl3·6H2O and benzoic acid. Also, with the variation of the molar ratio of Eu:Tb:Tm ions, a series of multicenter-Ln analogues [N(CH3)4]3K2[EuxTbyTm1−x−y(C7H5O2)(H2O)2(PW11O39)]·11H2O were synthesized [29]. More organic–inorganic hybrid lanthanide-based POMs, [N(CH3)4]3K2[Ln(C7H5O2)(H2O)2(PW11O39)]·11H2O, were synthesized using the same conditions with HoCl3·6H2O [30], SmCl3·6H2O [31] and TbCl3·6H2O [32]. In all these cases, the dilacunary [P2W19O69(H2O)]14– was used as a source of the resulting Keggin anion. The interaction of phthalocyanine complexes of lanthanides, [Ln(Pc)(OAc)] (Ln = Y, Dy, Tb), with the [PW11O39]7– anion in a 1:1:1 mixture of CH3CN:MeOH:CH2Cl2 also yielded a row of monomeric complexes (N(nBu)4)4H2[Ln(Pc)(PW11O39)] [33].
The second group includes dimeric complexes connected through the organic bridging ligands. In 2009, the series of polyoxoanions, [{(PW11O39)Ln(H2O)(CH3COO)}2]10– (Ln = Sm, Eu, Gd, Tb, Ho, Er), constructed from two monolanthanide substituted {PW11-Ln} units bridged by two acetato ligands, was published [34]. The row was continued with Dy-, Y- and Lu-containing analogues in 2012 [35]. In 2013, Na2[Cu(en)2(H2O)]4[{(PW11O39)Sm(H2O)(CH3COO)}2]·10H2O [36] and K2[Cu(en)2(H2O)]4[{(PW11O39)Tb(H2O)(CH3COO)}2]·15H2O [37] had the same hybrid acetate-bridging dimeric structures modified by [Cu(en)2(H2O)]2+ (en = 1,2-ethylenediamine) fragments. In 2012, four new oxalate-bridging lanthanide-substituted phosphotungstates {[(PW11O39)Ln(H2O)]2(C2O4)}10− (Ln = Y, Dy, Ho, Er) were synthesized by the reaction of a Keggin-type anion with Ln cations and oxalate ligands in aqueous solution [38]. The double-tartaric bridged phosphotungstates formulated as [N(CH3)4]6K3H7[Ln(C4H2O6)(PW11O39)]2·27H2O (Ln = Dy, Er, Yb [39] and Tm [40]) have been obtained using the dilacunary [P2W19O69(H2O)]14– as a precursor. In 2012, the hydrothermal conditions were successfully used to prepare the three-dimensional architectures [Ln(HL)(L)(H2O)6{Ln(H2L)0.5(PW11O39H)Ln(H2O)4}]2·nH2O (Ln = La, Ce, Pr; H2L = 2,5-pyridinedicarboxylic acid) based on lanthanide-substituted POM units [41].
The largest number of examples to date refers to the third type—dimeric complexes in which POM fragments are linked directly through lanthanide cations. In 1971, Peacock and Weakley isolated several dimeric compounds, formulated as K11[CeIII(PW11O39)2]·24H2O, K10[CeIII(PW11O39)2]·25H2O, K11[Pr(PW11O39)2]·22H2O K11[Nd(PW11O39)2]·26H2O [42]. In 2004, the structure of Cs11Eu(PW11O39)2]·28H2O was published [43]. The CeIV sandwiched between two lacunary Keggin-type [PW11O39]7– anions resulted in a lanthanide polyoxometalate (NH4)2[N(CH3)4]6Na2[Ce(PW11O39)2]·14H2O [44]. The central {CeIVO8} polyhedron reveals the square-antiprismatic geometry. The analogues dimeric compound was further prepared for praseodymium, [(CH3)4NH]4Na3[Pr(PW11O39)2]·12H2O [45]. The two isostructural anions, [CeIII(PW11O39)2]11– and [CeIV(PW11O39)2]10–, were isolated as dimethylammonium salts with the same square-antiprismatic coordination of the central {CeIII/IVO8} polyhedron [46]. Interestingly that for similar complexes, [N(CH3)4]10H[La(PW11O39)2]·21H2O and [N(CH3)4]10H[Ce(PW11O39)2]·19H2O, an approximate cubic {LnO8} geometry was found [47]. Potassium- or mixed potassium/caesium salts of [Ln(PW11O39)2]11− dimeric anions were obtained and characterized for ten lanthanids (Ln = Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) [48]. Three phosphors based on polyoxotungstates, K3Cs8[Eu(PW11O39)2]·11H2O, K3Cs8[Sm(PW11O39)2]·10H2O and K5Cs6[Dy(PW11O39)2]·15H2O, were prepared and characterized [49]. In 2017, a dysprosium-containing phosphotungstate compound, K2[N(CH3)4]5H4[Dy(PW11O39)2]·21H2O, was published [50].
Separately, a series of novel polyoxometalate trimers, H3[N(CH3)4]14[NaLn(PW11O39)3]·18H2O (Ln = Nd, Sm, Eu), can be noted. Herein, the dimeric unit {Ln(PW11O39)2} and Na-substituted POM monomer {NaPW11O39} linked to form an unprecedented linear structure [51].
Organic–inorganic hybrid enantiomeric compounds of K1.3Na3.2H6.5[L-Pr(PW11O39)2]·8.3L-proline·21.5H2O, K1.3Na3.2H6.5[D-Pr(PW11O39)2]·8.3D-proline·17H2O, K1.3Na3.2H6.5[L-Er(PW11O39)2]·8.3L-proline·22.5H2O [52] and KNa3[Hproline]7[Sm(PW11O39)2]·D-proline·18H2O [53] were obtained by using L- and D-proline as chiral auxiliary agents. The series was expanded by the isolation of [Ln(PW11O39)2]11– polyanions (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb and Y) using proline [54].
In 2008, compound [Cu(en)2]2H8[Gd(PW11O39)2]·(H2en)0.5·3H2O prepared under hydrothermal conditions was described [55]. In 2010, more inorganic–organic hybrid Ln-POM compounds with en-copper-complexes, H8[Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][La(PW11O39)2]}2·18H2O, H6[Na2(en)2(H2O)5][Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][Ce(PW11O39)2]}2·16H2O, H6[Na2(en)2(H2O)5][Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][Pr(PW11O39)2]}2·18H2O, H6[Na2(en)2(H2O)4][Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][Nd(PW11O39)2]}2·14H2O, H6[Na2(en)2(H2O)5][Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][Sm(PW11O39)2]}2·20H2O and H7[Cu(en)2]2[Sm(PW11O39)2]·10H2O, were published [56]. In 2011, complexes H14[Cu(en)2]4[Ce(PW11O39)2]2·2en·21H2O, H14[Cu(en)2]4[Pr(PW11O39)2]2·11H2O and H8[Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][Pr(PW11O39)2]}2·2en·12H2O were presented [57]. A series of 3d–4f heterometallic monovacant Keggin phosphotungstate derivatives, [Cu(dap)(H2O)2]0.5[Cu(dap)2]4H2[Pr(PW11O39)2]·3H2O (dap = 1,2-diaminopropane), [Cu(en)2(H2O)]2[Cu(en)2]1.5H4[Pr(PW11O39)2]·10H2O [58], [Cu(en)2]2H6[Ce(PW11O39)2]·8H2O, [Cu(dap)2(H2O)][Cu(dap)2]4.5[Dy(PW11O39)2]·4H2O [59], [Cu(dap)2]5.5[Y(PW11O39)2]·4H2O [60], Cu(dap)2(H2O)][Cu(dap)2]4.5[Sm(PW11O39)2]·5H2O, [Cu(dap)2(H2O)][Cu(dap)2]4.5[Er(PW11O39)2]·4H2O [61], [Cu(dap)2(H2O)][Cu(dap)2]4.5[La(PW11O39)2]·4H2O [62] and H[Cu(dap)2(H2O)][Cu(dap)2]4[Eu(PW11O39)2]·13H2O [63], was prepared in hydrothermal conditions.
The first 2:2 type monolanthanide substituted POM dimers, [{(PW11O39H)Ln(H2O)3}2]6− (Ln = Nd, Gd), have been published in 2009. The binding of the [PW11O39Ln(H2O)3]4− anionic fragments in this structure was provided by two Ln-O-W bridges [34]. In 2017, a dysprosium-containing 2:2 type dimer, Na2[N(CH3)4]4H2[{Dy(PW11O39)(H2O)3}2]·28H2O, was obtained [50].
One more types of compounds include the chains built from Ln-POMs. Complex Al(H3O)[Eu(H2O)2PW11O39]·20H2O was obtained in 2004, and in the solid state, it was an infinite one-dimensional zigzag polymer. A Europium atom coordinated to the POM vacant site was served as the linking element and connected to neighboring {PW11O39} units via terminal oxygen atoms [43]. In 2011, the same 1-D zigzag chain was found for [N(CH3)4]4[Ce(H2O)2(PW11O39)]·2H2O with linking [Ce(H2O)2]3+ cations [64]. Another chain-like structure was found for [N(CH3)4]4[Tb(H2O)2(PW11O39)]·2H2O. In this case, the Tb3+ cation coordinated with the POM unit vacancy was connected to the terminal oxygen of only one adjacent {PW11O39} to form a linear chain [65].
Herein, we present a series of 1:1 Ln3+/POM complexes (Ln = Pr, Eu, Gd, Tb, Dy) of the general formula Cat4Ln(PW11O39)·xH2O (Cat = K+ or Me4N+). In the case of gadolinium compounds, we found three types of structures: complex (Me4N)2K2[Gd(H2O)2PW11O39]·5H2O (1Gd) is polymeric, revealing a layered structural motif, and complexes (Me4N)6K2[Gd(H2O)3PW11O39]2·20H2O (2Gd) and (Me4N)7K[Gd(H2O)3PW11O39]2·12H2O (3Gd) are classified as dimeric. For the sake of simplicity, we formulate the compounds with the K+ ions outside the brackets, even though they coordinate directly with the POMs. Other Ln-containing complexes are isostructural with the gadolinium analogues.

2. Results and Discussion

2.1. Synthesis

Several approaches were described in the literature for the preparation of Ln-POM complexes differing in the lacunary phosphotungstate precursors, such as [PW9O34]9− [43] or [P2W19O69(H2O)]14− [50]. In our work, we used a monolacunary [PW11O39]7− polyoxoanion to react with Ln cations, and the pH value was set at 5.4. As a result, we obtained crystals of three different kinds simultaneously. We were succeeded in structurally characterizing all three types of crystals for the gadolinium-containing compounds, and the unit cell parameters for the three types were also determined in the case of europium. For praseodymium, it was possible to determine the parameters of two types of crystals, and only one type was characterized in the case of dysprosium and terbium (Table 1). The resulting phases were additionally characterized by IR spectroscopy (Figure S1).

2.2. Structural Description

The structure of (Me4N)2K2[Gd(H2O)2PW11O39]·5H2O (1Gd) is presented in Figure 1a,b. The Gd is incorporated to the vacant site of the {PW11O39} POM, coordinating via four O atoms (Figure 1a). The Gd further coordinates two neighboring POMs, thus forming a chain with the {Gd2(POM)2} secondary building unit (Figure 1b), similarly to that in works [43,64]. The coordination sphere of Gd is supplemented by two H2O ligands, resulting in a {GdO8} polyhedron with the typical Gd–O distances. Potassium counterions join the chains into layers via K–O bonds with the POMs (Figure 2a,b). Me4N+, and disordered hydrate molecules are located between the layers.
The structure of 2Gd and 3Gd somewhat resembles 1Gd in that they comprise a {Gd2(POM)2} secondary building unit. However, in 2Gd and 3Gd, it is not interlocked in a chain but is supplemented by two terminating H2O ligands, thus forming a centrosymmetric dimer structure (Figure 3). Analogous dimeric structures with different counterions (Na+/H+/Me4N+) have recently been reported [34,50]. The coordination polyhedron {GdO8} is similar in the compounds. Contrary to 1Gd, the structures of 2Gd and 3Gd reveal a disorder of K+ and Me4N+, i.e., the latter take partial occupancy, sharing similar positions with the hydrate molecules. The ratio of the cations is approximately similar within the series (tested for several crystals of 2 or 3). Due to the complicated disorder, positions of the counterions and the hydrate molecules are rather arbitrary. We speculate that the disordered K+ can both coordinate directly with the POM and bind via a hydrogen bond network. The number of the outer-sphere H2O and Me4N+ in 2Gd and 3Gd is larger than in 1Gd, so the POM species are more separated from each other in the former. The difference between 2Gd and 3Gd consists in different crystal packing of the POMs, which is induced by a variation in the outer-sphere composition (Figure 4). Specifically, in 2Gd, the POMs are located one above the other with the translation relation (P–1 space group), while in 3Gd, neighboring POMs are oriented by an angle of ca. 40° with respect to each other (relation by two-fold screw symmetry; P21/c space group).
Other lanthanide analogues with Pr, Eu, Tb and Dy also constitute three structural types 1–3, which are identified by unit cell parameters of single crystals (Table 1). One can note that the unit cell parameters generally correlate with the ionic radius of the lanthanides. At the same time, experiments within one lanthanide series reveal a quite large variation of the parameters above the instrument accuracy. Specifically, the unit cell volume for several crystals of 3Pr varies by 100 Å3, while the difference in parameter c can be up to 0.46 Å (Table 2). This is likely a consequence of the non-stoichiometric composition of disordered hydrate molecules in the compounds, which varies from crystal to crystal.

3. Experimental Section

3.1. Materials and Methods

The K7[PW11O39]·14H2O precursor was prepared according to the literature [66] and confirmed by IR spectra. Other chemicals were purchased commercially from Sigma Aldrich and used without further purification. Infrared spectra (4000–400 cm−1) were recorded on a Scimitar FTS 2000 spectrophotometer in KBr pressed pellets.

3.2. Synthesis

Synthesis of Cat4Gd(PW11O39)·xH2O: First, 1.00 g (0.31 mmol) of K7[PW11O39]·14H2O was dissolved in 15 mL of water, which was followed by the addition of 0.20 g (0.54 mmol) of GdCl3·6H2O in 15 mL of water dropwise, resulting in a pH = 4.7. The pH value was adjusted to 5.4 using 2M KOH solution under stirring. The reaction mixture was heated at 80 °C for 1 h after the solution was cooled to room temperature and filtered. Then, 0.20 g (1.30 mmol) of tetramethylammonium bromide was added under stirring. After 0.5 h, the resulting solution was filtered and left to evaporate at room temperature. A crystalline phase was obtained after one week. Yield: ca. 43% (based on K7[PW11O39]·14H2O).
Synthesis of Cat4Pr(PW11O39)·xH2O: The synthetic procedure was identical to that for Gd-POMs, but we used 0.2 g (0.54 mmol) of PrCl3·7H2O as the Ln reagent. A crystalline phase was obtained after one week. Yield: ca. 35% (based on K7[PW11O39]·14H2O).
Synthesis of Cat4Eu(PW11O39)·xH2O: The synthetic procedure was identical to that for Gd-POMs, but we used 0.2 g (0.55 mmol) of EuCl3·6H2O as the Ln reagent. A crystalline phase was obtained after one week. Yield: ca. 51% (based on K7[PW11O39]·14H2O).
Synthesis of Cat4Tb(PW11O39)·xH2O: The synthetic procedure was identical to that for Gd-POMs, but we used 0.2 g (0.54 mmol) of TbCl3·6H2O as the Ln reagent. A crystalline phase was obtained after one week. Yield: ca. 24% (based on K7[PW11O39]·14H2O).
Synthesis of Cat4Dy(PW11O39)·xH2O: The synthetic procedure was identical to that for Gd-POMs, but we used 0.2 g (0.53 mmol) of DyCl3·6H2O as the Ln reagent. A crystalline phase was obtained after one week. Yield: ca. 27% (based on K7[PW11O39]·14H2O).

3.3. X-Ray Diffraction on Single Crystals

Single-crystal XRD data for the compounds were collected at 150 K (Table S1) with a Bruker D8 Venture diffractometer with a CMOS PHOTON III detector (Bruker, Madison, Wisconsin, USA) and IμS 3.0 microfocus source (MoKα radiation (λ = 0.71073 Å), collimating Montel mirrors; Incoatec GmbH, Geesthacht, Germany). The crystal structures were solved using the SHELXT [67] and were refined using the SHELXL [68] programs with OLEX2 GUI [69]. Atomic displacement parameters for non-hydrogen atoms were refined in anisotropic approximation with the exception for the disordered hydrate molecules and Me4N+. For the latter, EADP constraints and SADI restraints were applied where needed. Hydrogen atoms were placed geometrically and refined in the riding model with the exception for those of the disordered hydrate molecules, which were not localized. The structures of 1–3Gd were deposited to the Cambridge Crystallographic Data Centre (CCDC) as a supplementary publication, No. 2270528-2270530.

4. Conclusions

A series of 1:1 Ln3+/POM (Ln = Pr, Eu, Gd, Tb, Dy) complexes of the general formula Cat4Ln(PW11O39)·xH2O (Cat = K+ or Me4N+) was synthesized in an aqueous solution. It was shown that the {Ln(PW11O39)} fragments are always involved in binding with each other to form either polymer chains or dimeric units, and the Ln3+ coordination number is the same in all cases and equals 8. It was also found that for the isostructural compounds, the unit cell parameters mainly correlate with the corresponding ionic radius of the lanthanides. The description of these compounds is important for the study of other monovacant POMs of the Keggin type in an aqueous solution and should be taken into account when developing {Ln-POM} hybrid complexes.

Supplementary Materials

The supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/inorganics11080327/s1, Figure S1: IR spectra of Cat4Ln(PW11O39)·xH2O complexes (Ln from the top to the bottom): Gd, Eu, Pr, Tb and Dy; Table S1. Crystal data and structure refinement for 1–3Gd.

Author Contributions

Conceptualization, M.N.S.; methodology, V.S.K. and M.N.S.; analysis, V.S.K. and T.S.S.; investigation, V.S.K. and T.S.S.; writing—original draft preparation, V.S.K. and T.S.S.; writing—review and editing, V.S.K. and M.N.S.; visualization, V.S.K. and T.S.S. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Ministry of Science and Higher Education of the Russian Federation, № 121031700313-8 (The Nikolaev Institute of Inorganic Chemistry SB RAS).

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The authors thank the NIIC SB RAS team for the access to IR and SCXRD facilities.

Conflicts of Interest

The authors declare no conflict of interest.

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Inorganics 11 00327 g001
Figure 1. (a) The structure of {Gd(H2O)2PW11O39} unit in compound 1Gd; (b) the corresponding {Gd(H2O)2PW11O39}n chain. The WO6 moieties are depicted as octahedra.
Figure 1. (a) The structure of {Gd(H2O)2PW11O39} unit in compound 1Gd; (b) the corresponding {Gd(H2O)2PW11O39}n chain. The WO6 moieties are depicted as octahedra.
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Inorganics 11 00327 g002
Figure 2. (a) The structure of a layer composed from {Gd(H2O)2PW11O39}n chains bound with K+ cations in compound 1Gd; (b) the crystal packing of the layers. Me4N+ and hydrogens are not shown, the WO6 moieties are depicted as octahedra.
Figure 2. (a) The structure of a layer composed from {Gd(H2O)2PW11O39}n chains bound with K+ cations in compound 1Gd; (b) the crystal packing of the layers. Me4N+ and hydrogens are not shown, the WO6 moieties are depicted as octahedra.
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Inorganics 11 00327 g003
Figure 3. The structure of a dimer {Gd(H2O)3PW11O39}2 in compounds 2Gd and 3Gd.
Figure 3. The structure of a dimer {Gd(H2O)3PW11O39}2 in compounds 2Gd and 3Gd.
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Inorganics 11 00327 g004
Figure 4. Crystal packing of the dimers in compounds 2Gd (a) and 3Gd (b). The WO6 moieties are depicted as octahedra, hydrate molecules, hydrogens and the disorder are not shown.
Figure 4. Crystal packing of the dimers in compounds 2Gd (a) and 3Gd (b). The WO6 moieties are depicted as octahedra, hydrate molecules, hydrogens and the disorder are not shown.
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Table 1. Unit cell parameters for selected crystals of the compounds: V (Å3), a (Å), b (Å), c (Å), α (°), β (°), and γ (°).
Table 1. Unit cell parameters for selected crystals of the compounds: V (Å3), a (Å), b (Å), c (Å), α (°), β (°), and γ (°).
Ln1, P–12, P–13, P21/c
Pr249811.82 12.28 19.62
94.6 91.0 118.1		 605313.11 22.08 21.35
90 101.7 90
Eu238611.8 11.9 19.4
96.0 92.1 117.7		330512.81 13.04 23.41
73.1 83.9 62.1		585613.0 22.1 20.7
90 100.0 90
Gd238011.73 11.92 19.39
95.85 92.30 117.57		328912.8 13.0 23.3
73.8 84.3 61.8		579912.96 22.10 20.68
90 100.11 90
Tb240711.75 11.97 19.53
96.1 92.1 117.7
Dy 326712.72 13.04 23.20
74.0 81.3 62.1
Table 2. Unit cell parameters for several crystals of 3Pr (P21/c space group): V (Å3), a (Å), b (Å), c (Å), and β (°).
Table 2. Unit cell parameters for several crystals of 3Pr (P21/c space group): V (Å3), a (Å), b (Å), c (Å), and β (°).
Vabcβ
crystal 15969.5 (9)13.0360 (8)21.9985 (11)21.228 (2)101.300 (9)
crystal 25889.3 (9)13.0069 (10)22.0055 (16)20.908 (3)100.228 (9)
crystal 35878.9 (6)13.0061 (7)22.0170 (14)20.858 (2)100.174 (6)
crystal 45851.2 (5)13.0038 (10)21.9926 (12)20.7695 (12)99.905 (5)
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Korenev, V.S.; Sukhikh, T.S.; Sokolov, M.N. A Series of Lanthanide Complexes with Keggin-Type Monolacunary Phosphotungstate: Synthesis and Structural Characterization. Inorganics 2023, 11, 327. https://doi.org/10.3390/inorganics11080327

AMA Style

Korenev VS, Sukhikh TS, Sokolov MN. A Series of Lanthanide Complexes with Keggin-Type Monolacunary Phosphotungstate: Synthesis and Structural Characterization. Inorganics. 2023; 11(8):327. https://doi.org/10.3390/inorganics11080327

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Korenev, Vladimir S., Taisiya S. Sukhikh, and Maxim N. Sokolov. 2023. "A Series of Lanthanide Complexes with Keggin-Type Monolacunary Phosphotungstate: Synthesis and Structural Characterization" Inorganics 11, no. 8: 327. https://doi.org/10.3390/inorganics11080327

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