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Acta Crystallographica Section C: Structural Chemistry logoLink to Acta Crystallographica Section C: Structural Chemistry
. 2022 Apr 20;78(Pt 5):299–304. doi: 10.1107/S2053229622003369

Synthesis and characterization of the ‘Japanese rice-ball’-shaped Molybdenum Blue Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O

Emir Al-Sayed a, Elias Tanuhadi a, Gerald Giester b, Annette Rompel a,*,‡
PMCID: PMC9069247  PMID: 35510436

The synthesis and crystal structure of a ‘Japanese rice-ball’-shaped Molybdenum Blue hybridized organically with 2-picolinic acid is presented. In addition to single-crystal X-ray analysis, the title com­pound was characterized with IR spectroscopy and elemental analyses to reinforce its framework structure, thermogravimetric analysis to qu­antify the water content, and Vis–NIR spectroscopy to determine the degree of reduction of the nanocluster.

Keywords: polyoxomolybdate, cerium, hybrid organic–inorganic, nanocluster, crystal structure, Molybdenum Blue

Abstract

The hybridized lanthanide-containing molybdenum blue (Ln-MB) wheel Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O ({Mo2(C6H4NO2)2}2{Mo120Ce6}) was assembled in an aqueous one-pot synthesis. The Ln-MB was hybridized with 2-picolinic acid through the generation of the organometallic counter-ion [Mo2O2(OH)4(C6H4NO2)2]2+. Control experiments demonstrated that the position of the carb­oxy­lic acid group (2-position to the N atom) in the hybridization com­ponent is critical in yielding single crystals of Ln-MB. In addition to single-crystal X-ray diffraction (XRD) analysis, which revealed a ‘Japanese rice-ball’-shaped Ln-MB as the anion, elemental analyses, IR spectroscopy, and thermogravimetric analysis (TGA) were performed to confirm its structure and com­position. Bond-valence-sum calculations (BVS) revealed that {Mo2(C6H4NO2)2}2{Mo120Ce6} is com­posed of a 24-electron re­duced anionic ring, which was confirmed by Vis–NIR spectroscopy.

Introduction

Polyoxometalates (POMs) are polynuclear oxo-bridged metal oxide clusters primarily com­posed of early transition metals in their highest oxidation states (Pope, 1987 ▸; Gumerova & Rompel, 2020 ▸). The early transition-metal ions (Mn+ ) are commonly MoV/VI, WV/VI, VIV/V, NbV, or TaV, which form {MO x } (x = 4–7) polyhedra that are typically linked together via corner- and edge-shared O atoms (Pope, 1987 ▸). Their structural diversity (size, shape, and com­position) and unique properties give rise to a plethora of potential applications from medicine (Stephan et al., 2013 ▸; Yamase, 2005 ▸; Bijelic et al., 2019 ▸; Tanuhadi et al., 2020 ▸) to catalysis (Al-Sayed et al., 2021 ▸; Chen et al., 2021 ▸) and macromolecular crystallography (Bijelic et al., 2015 ▸; Mauracher et al., 2014a ▸,b ▸; Breibeck et al., 2019 ▸).

Molybdenum Blues (MBs) are giant POMs with the general formula [XaYb H c MoVI x MoV y O z (H2O) v ] n− (a = number of organic ligands; b = number of metallic heteroelements; c = degree of protonation; x and y = number of unreduced and reduced molybdenum, respectively; z = number of O atoms; v = number of coordinated water; n = resulting charge of the nanosized scaffold) (Al-Sayed & Rompel, 2022 ▸), with versatile topologies and high structural flexibility. MBs are commonly con­structed by generating and combining the virtual building blocks {MoO6} ({Mo1}) and {Mo2O11} ({Mo2}), and the funda­mental building block {Mo8O35} ({Mo8}) with the pen­ta­gonal unit {MoO7Mo5O20} ({Mo(Mo)5}) (Müller & Gouzerh, 2012 ▸). {Mo1}, {Mo2}, and {Mo8} are formed upon acidification (pH ≤ 4.5) (Shishido & Ozeki, 2008 ▸) of an orthomolybdate ([MoO4]2−) solution (∼20–30 mM for lan­tha­nide-containing MBs in a one-pot synthesis approach) and subsequent addition of a reducing agent (e.g. N2H4 with c ∼ 1 mM) (Müller & Roy, 2002 ▸).

The coordinative attachment of organic ligands onto {Mo2} building blocks, the {Mo2} substitution by metal ions of suitable size, such as lanthanide ions (LnIII ), and the incorporation of long-chain organic surfactants as charge-balancing cations enable structural modifications and changes in the physical properties (e.g. solubility) of the MB cluster. The modifications include organically functionalized nanocavities, which allow the stabilization of anionic templates in their centre via hydrogen bonds, as well as the construction of mol­ecular shapes (‘Japanese rice-ball’, ‘egg’ and ellipsoid) that deviate from the {Mo154–x } (x = number of defect sites) wheels (circle-shaped) (Al-Sayed & Rompel, 2022 ▸). The introduction of long-chain organic surfactants (e.g., dido­decyl­dimethyl­am­monium, DDMA) increases the hydro­phobicity and allows the polarity of the cluster to be modulated (Polarz et al., 2001 ▸; Jing et al., 2013 ▸). The Ln-MB crystal structure library is rather small, with about 30 crystal structures of Ln-MB ring systems (of which five are ‘Japanese rice-ball’-shaped Ln-MBs; Table 1 ▸) reported to date (as of January 2022).

Table 1. List of purely inorganic and hybridized inorganic–organic lanthanide-containing Molybdenum Blue wheels exhibiting a ‘Japanese rice-ball’ shape [based on the Inorganic Crystal Structure Database (FIZ, Karlsruhe; http://www.fiz-informationsdienste.de/DB/icsd/www-recherche.htm) and the Cambridge Structural Database (CSD; Groom et al., 2016 ▸), January 2022].

Formula Building blocks of the ‘Japanese rice-ball’ Reference
Na6[Mo120O366(H2O)48H12{Pr(H2O)5}6] 12 {Mo1}, 6 {Mo2}, 12 {Mo8}, 6 {Pr} Müller et al. (2000 ▸)
Na6[Mo120Ce6O366H12(H2O)78] 12 {Mo1}, 6 {Mo2}, 12 {Mo8}, 6 {Ce} Duros et al. (2017 ▸)
[NH4]4[Mo120O366H14(H2O)48{La(H2O)5}6] 12 {Mo1}, 6 {Mo2}, 12 {Mo8}, 6 {La} Yamase et al. (2006 ▸)
(C5H14N2O2)2[{Mo8O26}0.5 Inline graphic H12Mo124Ce4O376(H2O)60(C5H13N2O2)6] 12 {Mo1}, 8 {Mo2}, 12 {Mo8}, 4 {Ce} Xuan et al. (2019 ▸)
Na2(C10H17N5O4)[Mo122Ce5O371(H2O)69H12(C10H16N5O4)3] 12 {Mo1}, 7 {Mo2}, 12 {Mo8}, 5 {Ce} She et al. (2021 ▸)
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Previously, tryptophan has been utilized as a hybridizing ligand for functionalizing the inner ring of an ellipsoidal Ln-MB, yielding the cluster {Mo124Ce4(tryptophan)4}, featuring unprecedented kynurenine counter-cations as a result of tryptophan oxidation (Xuan et al., 2018 ▸) that occurred in situ during the self-assembly of {Mo124Ce4(tryptophan)4}. Fol­lowing the kynurenine pathway (Tan et al., 2012 ▸), which is a metabolic pathway and starts with the oxidation of tryptophan, the catabolite 2-picolinic acid was identified as a bidentate chelating agent. Herein 2-picolinic acid is utilized as an {Mo2}-hybridizing ligand, yielding the isolation of the new Ln-MB Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O featuring the organometallic coun­ter-cation [Mo2O2(OH)4(C6H4NO2)2]2+.

Experimental

Synthesis and crystallization

25 ml of a 3.6 mM CeIII stock solution [0.9 mmol CeCl3·7H2O (0.335 g) dissolved in 250 ml H2O] were com­bined with 25 ml of a 40 mM [MoO4]2− stock solution [10 mmol Na2MoO4·2H2O (2.42 g) dissolved in 250 ml H2O]. Following the addition of 2-picolinic acid (0.14 mmol, 0.0172 g), the solution was reduced with 0.5 ml of an aqueous hydrazine ([N2H4]·2HCl) solution (0.1 M), acidified with 4.5 ml HClO4 (1 M) to pH ∼1.4, and subsequently heated between 85–90 °C for 1.5 h in an Erlenmeyer flask covered with a watch glass. The resulting clear deep-blue solution was left to crystallize in the open Erlenmeyer flask for two weeks at room temperature. Deep-blue block-shaped crystals were filtered off, washed with ice-cold H2O and air-dried (yield: 45 mg, 22.5%, based on Mo). Elemental analysis calculated (%): C 1.18, H 2.44, N 0.23, Na 0.38, Mo 48.77, Ce 3.45; found: C 1.37, H 1.45, N 0.39, Na 0.35, Mo 51.5, Ce 4.0. FT–IR (cm−1): 3252 (br), 1606 (m), 1411 (m), 1092 (m), 967 (m), 904 (m), 866 (m), 806 (s), 746 (s), 620 (s), 528 (s).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. C—H bond lengths were constrained to 0.95 Å for pyridine-2-carboxyl­ate C—H groups and refined in riding modes, with U iso(H) values set to 1.2U eq(C). SADI (equal distance) restraints were applied to the C—N and C—C bonds of one pyridine-2-carboxyl­ate ring (N2—C7, C8—C7, C9—C8, C10—C9, C10—C11 and N2—C11) and to the C—O bonds C12—O224 and C6—O225. The bond between the aromatic carbon C1 and the carboxyl­ate carbon C6 (C1—C6) was restrained to 1.43 (2) Å. In addition, all C atoms and some O atoms of the nanoring had to be refined using the constraint of equivalent anisotropic displacement parameters (EADP). One of two sodium ions in the asymmetric unit was refined with two positions (Na2 and Na3), each with 0.5 occupation factor. The refining of (disordered) H2O mol­ecules with positioned H atoms proved unachievable due to the high number of (disordered) H2O mol­ecules. Residual electron density arising from disordered H2O mol­ecules could be identified during crystal structure refinement. Considering the disorder of the H2O mol­ecules preventing a satisfactory refinement the corresponding electron densities were described employing a solvent mask to stabilize the refinement, and the qu­antity of H2O mol­ecules determined with TGA was entered into the CIF file.

Table 2. Experimental details.

Crystal data
Chemical formula Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O
M r 24391.76
Crystal system, space group Monoclinic, C2/c
Temperature (K) 200
a, b, c (Å) 54.272 (10), 38.896 (7), 31.734 (6)
β (°) 112.145 (4)
V (Å3) 62047 (19)
Z 4
Radiation type Mo Kα
μ (mm−1) 2.97
Crystal size (mm) 0.18 × 0.15 × 0.08
 
Data collection
Diffractometer Bruker APEXII CCD
Absorption correction Multi-scan (SADABS; Bruker, 2016 ▸)
T min, T max 0.583, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections 373860, 32484, 23243
R int 0.101
θmax (°) 20.9
(sin θ/λ)max (Å−1) 0.502
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.083, 0.234, 1.07
No. of reflections 32484
No. of parameters 2814
No. of restraints 239
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 3.03, −2.19
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Computer programs: APEX2 (Bruker, 2016 ▸), SAINT (Bruker, 2016 ▸), SHELXT2018 (Sheldrick, 2015a ▸), PLATON (Spek, 2020 ▸), SHELXL2018 (Sheldrick, 2015b ▸), OLEX2 (Dolomanov et al., 2009 ▸), DIAMOND (Brandenburg, 2006 ▸) and shelXle (Hübschle et al., 2011 ▸).

Elemental analyses

The content of C/H/N/O was determined using an EA 1108 CHNS-O elemental analyzer from Carlo Erba Instruments at the Mikroanalytisches Laboratorium, Faculty of Chemistry, University of Vienna. The determination of Na/Mo/Ce was performed by Technische Universität Hamburg, Zentrallabor Chemische Analytik, Hamburg, Germany.

Vis–NIR spectroscopy

Vis–NIR spectroscopy was carried out at 298 K on a Shimadzu UV-2401PC spectrophotometer using a quartz cuvette with a 1.0 cm optical path length.

Thermogravimetric analysis (TGA)

TGA was conducted using a thermal analyzer (TA instruments model Q50, USA). The sample, having an initial mass of ∼15 mg, was subjected to a temperature range of 298–1173 K at a heating rate of 5 K min−1.

Attenuated total reflectance Fourier-transform infrared spectroscopy (ATR FT–IR)

All FT–IR spectra were recorded on a Bruker Vertex 70 IR spectrometer equipped with a single-reflection diamond ATR unit. Frequencies are given in cm−1 and intensities are denoted as w = weak, m = medium, s = strong, and br = broad.

Results and discussion

The 2-picolinic acid/Ce/Mo ratio (0.14/0.9/1) was critical for producing single crystals of Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O ({Mo2(C6H4NO2)2}2{Mo120Ce6}). When the concentration of 2-picolinic acid was lower (0.03–0.12 mol equivalents), either small weakly scattering crystals formed or the reaction solution remained clear with no crystals forming. {Mo2(C6H4NO2)2}2{Mo120Ce6} is a ‘Japanese rice-ball’-shaped com­plete Ln-MB ring system, which crystallizes in the space group C2/c. The inner and outer diameters of the Ln-MB anion {Mo120Ce6} are ∼17 and ∼31 Å, respectively (Fig. 1 ▸). The {Mo124Ce6} scaffold is com­posed of 12 {Mo1}, 6 {Mo2}, 12 {Mo8}, and 6 {Ce} (= {CeIIIO9}) building units. In the ‘Japanese rice-ball’ {Mo2(C6H4NO2)2}2{Mo120Ce6}, six {Mo2} groups are replaced by six {CeIII} groups. The average size of the incorporated {CeIII} in the inner ring (O—CeIII—O) is 4.8 Å, while the corner-sharing {Mo2} units (O—Mo—O—Mo—O) are 7.3 Å, forcing the cluster into a ‘more contracted’ architecture exhibiting an irregular ring shape and a lower symmetry (D 3) com­pared to that of the ideal circular parent structure {Mo154} (D 7d ) (Müller et al., 1996 ▸). All cerium ions on both the upper and lower surfaces of {Mo120Ce6} are trivalent and exhibit tricapped trigonal prismatic coordination spheres (Fig. 1 ▸). Each CeIII ion is coordinated by five water mol­ecules ({CeIII(H2O)5}) and is linked to the Ln-MB scaffold via six μ2-O atoms. The negative charge of 8− of the ‘Japanese rice-ball’ is balanced by two [Mo2O2(OH)4(C6H4NO2)2]2+ ({Mo2(C6H4NO2)2}2+) organometallic cations and four Na+ ions (Fig. 2 ▸), which are located in the outer shell of the cluster. In {Mo2(C6H4NO2)2}2+, two 2-picolinic acid mol­ecules are coordinated equatorially and axially onto both MoVI ions, which are linked together via monoprotonated edge-shared O atoms (Fig. 3 ▸). Control experiments revealed that neither nicotinic acid nor isonicotinic acid (both isomers of 2-picolinic acid) can yield hybridized Ln-MB frameworks under otherwise identical synthetic conditions.

Figure 1.

Figure 1

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Polyhedral representation [and inner (left) and outer (right) diameters of the respective ring/rim] of the ‘Japanese rice-ball’ in {Mo2(C5H5N)2}2{Mo120Ce6}. Colour code: {MoO6} yellow, {Mo2O11} red, {Mo8O35} blue, with the central {MoO7} unit in cyan, and {CeO9} green.

Figure 2.

Figure 2

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Ball-and-stick representation of the packing mode of {Mo2(C6H4NO2)2}2{Mo120Ce6} along the (a) y axis and (b) z axis. Colour code: Mo blue, Ce green, O red, Na turquoise, C grey, and N pink.

Figure 3.

Figure 3

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Ball-and-stick representation of the charge-balancing cation [Mo2O2(OH)4(C6H4NO2)2]2+ ({Mo2(C6H4NO2)2}2+) coordinated to Na+ ions. Colour code: Mo dark blue, C grey, N pink, O red, H white, and Na turquoise.

The sum formula of {Mo2(C6H4NO2)2}2{Mo120Ce6} was determined based on single-crystal X-ray diffraction (XRD), elemental, bond-valence-sum (BVS; Brown, 1981 ▸), and thermogravimetric (TGA) analysis. Furthermore, BVS was carried out to calculate the number of MoV centres within the Ln-MB and UV–Vis–NIR spectroscopy was performed to determine the contribution of each MoV centre to the overall reduction state of the nanocluster. Due to the low water solubility of {Mo2(C6H4NO2)2}2{Mo120Ce6}, which is a frequently encountered problem in the case of hybridized Ln-MBs (Xuan et al., 2019 ▸; She et al., 2021 ▸), redox titration to determine the number of reduced electrons in {Mo2(C6H4NO2)2}2{Mo120Ce6} was not feasible.

BVS calculations revealed that {Mo2(C6H4NO2)2}2{Mo120Ce6} is constructed of a 24-electron reduced wheel containing 14 mono- and 76 diprotonated O atoms. 12 monoprotonated O atoms are the μ3-O of the 12 {Mo5O6}-incom­plete double-cubane-type com­partments in the equatorial plane of the wheel (Fig. 4 ▸). They exhibit an average BVS value of 1.2 (= monoprotonation), consistent with previous work (Müller & Serain, 2000 ▸; Xuan et al., 2018 ▸). The average BVS value of the Mo centres in the equatorial plane of the wheel spanning the 12 {Mo5O6} com­partments is 5.6, demonstrating the presence of two 4d electrons delocalized in each com­partment, which is in accordance with previous work (Müller & Serain, 2000 ▸; Xuan et al., 2018 ▸).

Figure 4.

Figure 4

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Polyhedral representation of {Mo2(C5H5N)2}2{Mo120Ce6}, with one of 12 {Mo5O6}-incom­plete double-cubane-type com­partments highlighted in a ball-and-stick representation. Colour code: {MoO6} yellow, {Mo2O11} red, {Mo8O35} blue, with the central {MoO7} unit in cyan, {CeO9} green, Mo blue and yellow spheres, and O red spheres.

The molar extinction coefficient (ɛM) of Ln-MBs around 750 nm (in aqueous medium) is associated with the total number of reduced MoV centres present in the nanocluster (Müller & Gouzerh, 2012 ▸). The ɛM of {Mo2(C6H4NO2)2}2{Mo120Ce6} was determined to be 6.76 × 104 l mol−1 cm−1 (in a 0.5 M H2SO4 solution to ensure com­plete dissolution) which is in the range typical for ‘Japanese rice-ball’-shaped Ln-MBs with 24 MoV centres (2.6–14.4 × 104 l mol−1 cm−1) (Yamase, 2005 ▸; Duros et al., 2017 ▸). Consequently, the average contribution to the determined ɛM is approximately 2.82 × 103 l mol−1 cm−1 per MoV centre at 745 nm (Fig. 5 ▸), which corresponds to the inter­valence charge transfer between MoVI and MoV.

Figure 5.

Figure 5

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Vis–NIR spectrum of {Mo2(C6H4NO2)2}2{Mo120Ce6} in 0.5 M H2SO4 (c = 1.56 × 10−5 mol l−1).

TGA was carried out to determine the number of crystal, coordinated, and structural water mol­ecules in {Mo2(C6H4NO2)2}2{Mo120Ce6}. The obtained TG curve shows three main steps (I, II, and IV) of weight losses and one step (III) of weight increase in the range between 25 and 900 °C (Fig. 6 ▸). The first weight loss (∼13%) occurs between 25 and 110 °C, corresponding to ∼172 crystalline H2O. The second weight loss (∼10%) takes place between 110 and 473 °C, which can be assigned to ∼104 H2O (= 76 coordinated H2O + 28 structure H2O), and ∼4 2-picolinic acid ligands. The third step (III) emerges between 473 and 630 °C, and represents an increase in weight (∼1.75%) attributed to the oxidation of ∼3 2-pico­linic acid ligands to 2-picolinic acid N-oxide by {Mo2(C6H4NO2)2}2{Mo120Ce6}, which is consistent with previous observations made for MoVI/V-containing POMs of the Keplerate archetype as catalysts for the conversion of picolinic acid derivatives to the corresponding N-oxides in excellent yields (Yang et al., 2015 ▸). The fourth and last weight loss (∼75%) occurs between 635 and 900 °C, and is related to the decom­position of the metal oxide framework of Ln-MB.

Figure 6.

Figure 6

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Thermogravimetric curve of {Mo2(C5H5N)2}2{Mo120Ce6}, exhibiting three steps (I, II and IV) of weight loss and one step (III) of weight increase.

The FT–IR spectrum of {Mo2(C6H4NO2)2}2{Mo120Ce6} is depicted in Fig. 7 ▸, with the main vibrational bands listed in Table 3 ▸. The sharp and broad bands in the region between 1606 and 3252 cm−1 correspond to the stretching and bending vibrations ν/δ(O—H) of H2O. The vibrational bands ν(C—N) and ν(C=N) of 2-picolinic acid emerge between 1092 and 1411 cm−1, which are missing in a pure inorganic cerium-containing ‘Japanese rice-ball’ (Duros et al., 2017 ▸). The vib­rational bands ν(C=C) (∼1600 cm−1) and ν(=C—H) (∼3000 cm−1) of 2-picolinic acid are obscured as they are likely overlaid by the water bands in this particular region. The vibrational band at 967 cm−1, which is very sharp and characteristic for molybdenum-based POM structures, is attributed to terminal Mo=O groups. All bands appearing below 967 cm−1 correspond to the deformation vibrations ν(Mo—O—Mo) of the Mo—O—Mo bridging units.

Figure 7.

Figure 7

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FT–IR spectrum of {Mo2(C6H4NO2)2}2{Mo120Ce6} in the region between 4000 and 450 cm−1.

Table 3. Summary of the main vibrational bands observed for {Mo2(C6H4NO2)2}2{Mo120Ce6}.

Intensities are denoted as: w = weak, m = medium, s = strong, and br = broad.

Wavenumber (cm−1) Assignment
3252 (br) ν(O—H) of H2O
1606 (m) δ(O—H) of H2O
1411 (m) ν(C=N) 2-picolinic acid
1092 (m) ν(C—N) 2-picolinic acid
967 (m) ν(Mo=O) of Ln-MB
904 (m) ν(Mo—O—Mo) of Ln-MB
866 (m) ν(Mo—O—Mo) of Ln-MB
806 (s) ν(Mo—O—Mo) of Ln-MB
746 (s) ν(Mo—O—Mo) of Ln-MB
620 (s) ν(Mo—O—Mo) of Ln-MB
528 (s) ν(Mo—O—Mo) of Ln-MB
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Conclusion

The successful construction of {Mo2(C5H5N)2}2{Mo120Ce6} enlarged the sparse crystal structure library of ‘Japanese rice-ball’-shaped Ln-MBs. As {Mo2}-type building blocks, resulting from the self-assembly process of Ln-MB clusters, are organically modifiable, grafting organic ligands onto them yields unique hybridized inorganic–organic Ln-MB frameworks. {Mo2(C5H5N)2}2{Mo120Ce6} is the first reported ‘Japanese rice-ball’-shaped Ln-MB containing a metal–organic charge-balancing unit com­plexed aromatically with 2-picolinic acid in the outer shell.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2053229622003369/ky3215sup1.cif

c-78-00299-sup1.cif (11.4MB, cif)

Structure factors: contains datablock(s) I. DOI: 10.1107/S2053229622003369/ky3215Isup2.hkl

c-78-00299-Isup2.hkl (2.5MB, hkl)

CCDC reference: 2161749

Acknowledgments

The authors thank Mag. Johannes Theiner (Mikroanalytisches Laboratorium Universität Wien) and Dr Magnus Bo-Elfers (Technische Universität Hamburg, Zentrallabor Chemische Analytik, Hamburg, Germany) for elemental analyses. TGA measurements were carried out at the Institute of Materials Chemistry, Faculty of Chemistry, University of Vienna. ET and AR acknowledge the University of Vienna for awarding an Uni:docs fellowship.

Funding Statement

Funding for this research was provided by: Austrian Science Fund FWF (award No. P33089 to AR).

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2053229622003369/ky3215sup1.cif

c-78-00299-sup1.cif (11.4MB, cif)

Structure factors: contains datablock(s) I. DOI: 10.1107/S2053229622003369/ky3215Isup2.hkl

c-78-00299-Isup2.hkl (2.5MB, hkl)

CCDC reference: 2161749

Articles from Acta Crystallographica. Section C, Structural Chemistry are provided here courtesy of International Union of Crystallography

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