Synthesis and Structure of a New Iodate Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 with a Complex Framework Based on the Condensation of [Sc(IO 3 ) 6 ] Building Blocks

: Transparent single crystals of a new iodate Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 were synthesized under mild hydrothermal conditions. X-ray diffraction of single crystal was used to determine the large crystal structure with 52 independent atoms, sp. gr. P 2 1 / c . The building blocks [Sc(IO 3 ) 6 ] 3 − of Sc octahedra and six (IO 3 ) groups are condensed into a framework; the structure contains additional isolated (IO 3 ) groups. Large Cs cations occupy holes and form an intercrossing framework. Similar building blocks [M(IO 3 ) 6 ] are known for many iodates; however, most are isolated. Their topology and symmetry differ and determine the properties of the compounds.


Introduction
Iodates are a class of inorganic compounds possessing I 5+ ions in umbrella-like coordination in the form of (IO 3 ) − anionic groups.Due to the polar distribution of the electron density around the I 5+ ions, many iodates with non-centrosymmetric structures are characterized by optical nonlinearity (e.g., well-known α-LiIO 3 [1], α-In(IO 3 ) 3 [2], BiO(IO 3 ) [3], and others [4,5]).In the last decade, iodates have attracted attention as potential materials with not only optical nonlinearity, but also many other attractive characteristics, such as photoluminescence or magnetic properties.On the other hand, the compounds exhibit a wide variety of structures, which led to interest in structural and crystal chemical studies.Typically, (IO 3 ) groups have isolated positions; however, condensed iodate anions are also described, for example, in HBa 2.5 (IO 3 ) 6 (I 2 O 5 ) and HBa(IO 3 )(I 4 O 11 ) [6], or recently obtained K 2 Na(IO 3 ) 2 (I 3 O 8 ) [7].
One of the most important goals of material research is the directed synthesis of the desired crystals (the so-called tailoring design) or knowledge of the conditions for their production.Therefore, all new data on the correlation of synthesis and the resulting phases are important for further development.

Materials and Methods
Single crystals of a new iodate Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 were synthesized under mild hydrothermal conditions in highly concentrated solutions.A mixture of standard oxides, analytical grade, and Cs carbonate of Sc 2 O 3 :Cs 2 CO 3 :I 2 O 5 = 1:4:8, which, in mass ratio, corresponded to 0.5 g (3.63 mmol) Sc 2 O 3 , 2 g (6.14 mmol) Cs 2 CO 3 and 4 g (11.98 mmol) I 2 O 5 , was dissolved in 10 mL of distilled water.The solution was hermetically sealed in a 30 mL PTFE-lined stainless steel pressure vessel and stored at T = 553 K for 7 days.Final cooling after synthesis to room temperature was carried out within 24 h.The grown crystals were isolated by filtration of the stock solution and washed with hot water.
The experiment revealed two phases.The first was colorless, transparent, and had the shape of predominantly hexagonal flat-prismatic crystals up to 0.5 mm in size.The second phase differed in morphology and was pale pink, transparent, isometric in shape, and up to 2 mm in size.The ratio of mass amounts of both phases was ~1:5.The overall mass yield of the experiment was close to ~95%.
The unit cell parameters for both morphological varieties were determined on single crystals using an XCalibur S diffractometer equipped with a CCD area detector (ω scanning mode) and graphite monochromatic Mo K α radiation source (λ = 0.71073 Å).The first phase was known as the trigonal compound Sc(IO 3 ) 3, whose symmetry correlated with the morphology of the crystals.The second phase had a monoclinic cell with a = 21.4044(3),b = 10.86740(14), c = 17.5707(3)Å, and β = 108.335(2)• .No such monoclinic unit was found for any compound in ICSD [30], so this phase was proposed as a new one.
Elemental analysis was carried out on crystal surfaces of the new phase using a Jeol JSM-6480LV scanning electronic microscope in combination with WDX analysis.The test revealed the presence of Cs, I, and Sc atoms.
An experimental powder XRD pattern was obtained for morphologically separated crystals of this new iodate phase using an STOE STADY diffractometer (Cu-Kα, Figure 1).After crystal structure determination (see below), a theoretical powder pattern (Figure 1) was calculated on the base of the .ciffile using the program Powder Cell [31].The calculated pattern matches well with the experimental one.Second harmonic generation measurements were carried out on the crys samples according to the Kurtz and Perry scheme [32] using a Minilite-I YAG:Nd operating in Q-switched mode at the repetition rate of 10 Hz at wavelength λω = mcm.The incident-beam peak power was about 0.1 MW on a spot 5 mm in diame the sample surface.A standard α-SiO2 powder sample with a 5 mcm grain size wa as a reference.The measured signal intensity (I2ω) from the sample was an order les respect to α-quartz Q = I2ω/I2ω (SiO2), indicating that crystals of the new phase wer trosymmetric.
An IR spectroscopic study was performed on an "FSM-1201" Fourier spectro (Russia) in transmission mode in air at room temperature in the wavenumber rang 400 to 4000 cm -1 ; the signal was accumulated over 50 scans at a resolution of 4 c sample prepared as a suspension of mineral powder in Vaseline oil was studied prepared suspension was applied to a plate of KBr, which was also used as a ref sample before applying the mineral suspension to it.
The spectrum of the studied Cs5[Sc2(IO3)9](IO3)2 sample (Figure 2) is represen two broad multicomponent absorption bands.According to [33] (p.179 high-frequency nine-component band corresponds to the stretching vibrations of t bonds in the "umbrellas" [IO3] − .The highest frequency components at 793, 812, an cm −1 are symmetrical stretching vibrations (symmetry type A1 for point symmetry C3v), and components with absorption maxima at 696, 723, 739, 753, and 767 cm −1 b to the stretching degenerate mode (symmetry type E, C3v).A large number of abso band components is associated with a decrease in the symmetry of the groups [IO therefore with a splitting of the E-type vibrations.In addition, factor group splitting absorption bands is also possible (Z = 4).
A complex absorption band with low intensity and absorption maxima at 42 Second harmonic generation measurements were carried out on the crystalline samples according to the Kurtz and Perry scheme [32] using a Minilite-I YAG:Nd laser operating in Q-switched mode at the repetition rate of 10 Hz at wavelength λ ω = 1.064 mcm.The incident-beam peak power was about 0.1 MW on a spot 5 mm in diameter on the sample surface.A standard α-SiO 2 powder sample with a 5 mcm grain size was used as a reference.The measured signal intensity (I 2ω ) from the sample was an order less with respect to αquartz Q = I 2ω /I 2ω (SiO 2 ), indicating that crystals of the new phase were centrosymmetric.
An IR spectroscopic study was performed on an "FSM-1201" Fourier spectrometer (Russia) in transmission mode in air at room temperature in the wavenumber range from 400 to 4000 cm −1 ; the signal was accumulated over 50 scans at a resolution of 4 cm −1 .A sample prepared as a suspension of mineral powder in Vaseline oil was studied.The prepared suspension was applied to a plate of KBr, which was also used as a reference sample before applying the mineral suspension to it.
The spectrum of the studied Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 sample (Figure 2) is represented by two broad multicomponent absorption bands.According to [33] (p.179), the highfrequency nine-component band corresponds to the stretching vibrations of the O-I bonds in the "umbrellas" [IO 3 ] − .The highest frequency components at 793, 812, and 820 cm −1 are symmetrical stretching vibrations (symmetry type A 1 for point symmetry group C 3v ), and components with absorption maxima at 696, 723, 739, 753, and 767 cm −1 belong to the stretching degenerate mode (symmetry type E, C 3v ).A large number of absorption band components is associated with a decrease in the symmetry of the groups [IO 3 ] − and therefore with a splitting of the E-type vibrations.In addition, factor group splitting of the absorption bands is also possible (Z = 4).
A complex absorption band with low intensity and absorption maxima at 420, 432, 450 and 460 cm    Differential thermal analyses (DTA) measurements were performed by means of STA 449 F5 Jupiter equipment (Netzsch, Germany) in the temperature range of 50-1000 °C with a heating rate of 20 °C/min in Ar gas flow.A PtRh20 crucible of 85 µL volume was used in the DTA experiments.The decomposition of the sample (Figure 3) begins at a temperature of 494 °C, with a sharp weight loss and the successive formation of several intermediate phases with decomposition temperatures of 536 and 566 °C.Weight loss in this case is 46%.With further heating, the final stable phase melts at a temperature of 626 °C, the melt decomposes at a rate that increases with increasing temperature up to 914 °C.The weight loss in this case reaches 94% of the initial mass of the sample.The final crystalline phase is stable at 1000 °C and does not experience any phase transitions upon further cooling of the sample to room temperature.

Single Crystal Structure Determination
For single-crystal X-ray diffraction studies, a transparent isometric crystal with area dimensions of 0.230 × 0.195 × 0.140 mm was selected and glued onto glass fiber (Figure 4).
Symmetry 2023, 15, x FOR PEER REVIEW

Single Crystal Structure Determination
For single-crystal X-ray diffraction studies, a transparent isometric crystal w dimensions of 0.230 × 0.195 × 0.140 mm was selected and glued onto glass fiber (F To collect experimental data, the same diffractometer was used (Table 1) exposure time of 20 s per frame and control frames measured during data collect data were integrated using the CrysAlis program [34], and the monoclinic P21 group was proposed.The centrosymmetric space group explains the absence of t signal.The search for a structural model was carried out by direct methods in c tion with an analysis of the residual electron density.It was proposed to conside itial unit cell content to be similar to K8Ce2I18O53, since this compound had sim parameters and volume [35].The direct method suggested 10 common 4e position Cs atom.However, only one was correct, and the remaining nine positions corres to I atoms: all I atoms were coordinated by three O atoms from the residual peaks.I-O distances were standard, and all I atoms had umbrella-like coordinat number of Cs atoms was large and corresponded to five.In addition, three dral-coordinated positions corresponding to Sc atoms were discovered at the density: two of them are special (2a and 2b), with the symmetry of the inversion The total amount of oxygen was 33, all in common positions.The final structur corresponded to the formula Cs5[Sc2(IO3)9](IO3)2, Z = 4.The structure is confirme Poling valence sum, in which all oxygen atoms are O 2− .The experimental data w rected for absorption in the CrysAlis program [34] using face indexing.The fina ment using SHELXL [36] with the anisotropic approximation of the thermal displ parameters for all the atoms and the refinement of the weighting scheme led structural characteristics.It was proposed to split the O33 position, but this was n into account and was explained by a freer temperature displacement of this apic in the IO3 unit.Crystallographic data, atomic coordinates, and selected bonds for iodate are presented in Tables 1, S1, and S2, CCDC deposit number 2285771 (s plementary Materials).ATOMS and VESTA programs [37,38] were used for the s visualization.collect experimental data, the same diffractometer was used (Table 1) with an exposure time of 20 s per frame and control frames measured during data collection.The data were integrated using the CrysAlis program [34], and the monoclinic P2 1 /c space group was proposed.The centrosymmetric space group explains the absence of the SHG signal.The search for a structural model was carried out by direct methods in combination with an analysis of the residual electron density.It was proposed to consider the initial unit cell content to be similar to K 8 Ce 2 I 18 O 53 , since this compound had similar cell parameters and volume [35].The direct method suggested 10 common 4e positions of the Cs atom.However, only one was correct, and the remaining nine positions corresponded to I atoms: all I atoms were coordinated by three O atoms from the residual density peaks.I-O distances were standard, and all I atoms had umbrella-like coordination.The number of Cs atoms was large and corresponded to five.In addition, three octahedral-coordinated positions corresponding to Sc atoms were discovered at the residual density: two of them are special (2a and 2b), with the symmetry of the inversion center.The total amount of oxygen was 33, all in common positions.The final structural result corresponded to the formula Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 , Z = 4.The structure is confirmed by the Poling valence sum, in which all oxygen atoms are O 2− .The experimental data were corrected for absorption in the CrysAlis program [34] using face indexing.The final refinement using SHELXL [36] with the anisotropic approximation of the thermal displacement parameters for all the atoms and the refinement of the weighting scheme led to good structural characteristics.It was proposed to split the O33 position, but this was not taken into account and was explained by a freer temperature displacement of this apical atom in the IO 3 unit.Crystallographic data, atomic coordinates, and selected bonds for the new iodate are presented in Tables 1, S1 and S2, CCDC deposit number 2285771 (see Supplementary Materials).ATOMS and VESTA programs [37,38] were used for the structure visualization.1.654 and −5.170The new iodate Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 has a large unit cell with 52 independent atoms possessing 463 parameters (Table 1 and Table S1); therefore, it is one of the most complex iodate structures, and demonstrates a new structure type.All I1-I11 atoms have typical umbrella-like coordination with regular bonds from 1.773 to 1.842 Å being standard.This coordination can be characterized as pyramidal or tetrahedral, in which the fourth vertex is represented by the I 5+ lone pair.Three independent Sc atoms are coordinated by regular octahedrons located in two special positions at inversion centers and one in a common position.Despite the differences, the octahedra are similar to each other with average Sc-O interatomic distances of 2.079, 2.091, and 2.087 Å (Table S2).The Sc octahedra are surrounded by six IO 3 groups attached via common oxygen vertices.These structural units, or building blocks with the formula [Sc(IO 3 ) 6 ] 3− (Figure 5a,b), are known in the previously studied iodates mentioned in the introduction.In the new iodate, there is a classical block with six IO 3 groups applied to every oxygen corner; however, the topology and symmetry of the block deviate significantly from the standard trigonal (Figure 5a,b), while the Sc1 and Sc2 blocks are centrosymmetric, and the Sc3 block is asymmetric.

Crystal Chemical Features of Cs
In addition to the IO 3 groups included in the block, there are two positions (I5 and I11) that do not participate in the blocks and are isolated in the structure.The building blocks are connected in chains through common IO 3 umbrellas for each octahedral pair, as in Sn(IO 3 ) 4 or Sn(IO 3 ) 2 F 2 .The chains are slightly curved and consist of triplet [Sc(IO 3 )] 3− blocks.They are extended along the solid diagonal of the monoclinic cell (Figure 5a)-crossing chains run in a diagonal ac projection up and down along the b-axis.The connection of neighboring chains to the framework occurs through other (IO 3 ) groups in common pairs of blocks.Thus, of the six (IO 3 ) groups in the blocks, I6, I1, and I8 connect the Sc octahedra into a framework, and the remaining I2, I9, and I7 belong to the apical IO 3 groups.
nected by common IO3 groups; there are no free IO3 groups in the structure (Figure 7a).It is trigonal, sp.gr.R3, and the blocks are more regular because the symmetry of the blocks is higher.K and Cl atoms occupy holes in the framework, alternating levels along the c-axis.The smaller ionic radii of K + compared to Cs + resulted in the filling of framework holes without any additional IO3 groups.The recently studied Cs3[Ta(IO3)6](IO3)2 [24] contains iodate layers of [Ta(IO3)6] − blocks, which alternate with isolated IO3 groups along the c-axis (Figure 7b).Five independent Cs atoms demonstrate typical bond lengths with the O atoms up to 3.529 Å and form different polyhedra with coordination numbers (CN) = 8, 9, 6, 7, and 6 for Cs1, Cs2, Cs3, Cs4, and Cs5, respectively.The polyhedral representation shows that the Cs atoms form their own framework (Figure 6), which intercrosses with the previous Sc blocks' framework.A sufficiently large number of Cs atoms significantly determines the topology of the framework-it is the second coordination sphere of the Cs atoms that affects the topology of the blocks and their deviation of trigonal symmetry (Figure 5b).
the topology of the framework-it is the second coordination sphere of the Cs atoms that affects the topology of the blocks and their deviation of trigonal symmetry (Figure 5b).
The complex iodate K8Ce2I18O53 [35] with similar cell parameters and volume mentioned before has another type of block [Ce(IO3)8] 4− with the central Ce 4+ in a distorted cube and eight (IO3) groups attached by O vertices.Such blocks are isolated in structure and differ significantly from those described [Sc(IO3)6] 3− Among the iodates, KSc(IO3)Cl [18] is closest to the new Cs5[Sc2(IO3)9](IO3)2 structure and has a framework composed of the same building blocks [Sc(IO3)6] 3− .They are connected by common IO3 groups; there are no free IO3 groups in the structure (Figure 7a).It is trigonal, sp.gr.R3, and the blocks are more regular because the symmetry of the blocks is higher.K and Cl atoms occupy holes in the framework, alternating levels along the c-axis.The smaller ionic radii of K + compared to Cs + resulted in the filling of framework holes without any additional IO3 groups.The recently studied Cs3[Ta(IO3)6](IO3)2 [24] contains iodate layers of [Ta(IO3)6] − blocks, which alternate with isolated IO3 groups along the c-axis (Figure 7b).The complex iodate K 8 Ce 2 I 18 O 53 [35] with similar cell parameters and volume mentioned before has another type of block [Ce(IO 3 ) 8 ] 4− with the central Ce 4+ in a distorted cube and eight (IO 3 ) groups attached by O vertices.Such blocks are isolated in structure and differ significantly from those described [Sc(IO 3 ) 6 ] 3− .Among the iodates, KSc(IO 3 )Cl [18] is closest to the new Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 structure and has a framework composed of the same building blocks [Sc(IO 3 ) 6 ] 3− .They are connected by common IO 3 groups; there are no free IO 3 groups in the structure (Figure 7a).It is trigonal, sp.gr.R3, and the blocks are more regular because the symmetry of the blocks is higher.K and Cl atoms occupy holes in the framework, alternating levels along the c-axis.The smaller ionic radii of K + compared to Cs + resulted in the filling of framework holes without any additional IO 3 groups.The recently studied Cs 3 [Ta(IO 3 ) 6 ](IO 3 ) 2 [24] contains iodate layers of [Ta(IO 3 ) 6 ] − blocks, which alternate with isolated IO 3 groups along the c-axis (Figure 7b).The excess of the iodate component during the synthesis was used in the crystallization of both compounds, the new Cs5[Sc2(IO3)9](IO3)2, and the previously studied Cs3[Ta(IO3)6](IO3)2.The crystals have an unusual pink color, which was absent for crystal powder, so it belongs to their surface.A similar effect was discovered for BiO(IO3) crystals treated in special conditions [29], as a result of which the resulting oxygen vacancies on the surface acquired a pink color.In addition to iodates, similar building blocks with a central M octahedron and six tetrahedra instead of pyramidal IO3 groups are known for phosphates in the NASICON structure type, silicate minerals such as beryl, benitoite, wadeite, and hilairite, and synthetic germanates [39].Some of them are shown in Figure 8a-g.The topology and symmetry of the blocks vary from high symmetrical 32, −3 up to centrosymmetric −1, or asymmetric 1.The latter is characteristic of building blocks in new iodate compounds (Figure 3b).The positions of IO3 groups in the blocks are replaced by PO4, GeO4, or SiO4 tetrahedra with a general formula (M(TO4)6).The key point is the method of block condensation: for highly charged P 5+ or I 5+ , sharing of PO4 tetrahedra or pyramidal IO3 groups between octahedral pairs is preferable in contrast to Ge 4+ or Si 4+ tetrahedra with vertex condensation.
One can assume the synthesis of such hypothetical compounds in which both iodate and tetrahedral groups would be present in one block.There is an example of borophosphate with BO4 and PO4 tetrahedra in NaIn[BP2O8(OH)] [40].Such blocks would be asymmetric in structure and provide promising properties to the crystals.The excess of the iodate component during the synthesis was used in the crystallization of both compounds, the new Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 , and the previously studied Cs 3 [Ta(IO 3 ) 6 ](IO 3 ) 2 .The crystals have an unusual pink color, which was absent for crystal powder, so it belongs to their surface.A similar effect was discovered for BiO(IO 3 ) crystals treated in special conditions [29], as a result of which the resulting oxygen vacancies on the surface acquired a pink color.
In addition to iodates, similar building blocks with a central M octahedron and six tetrahedra instead of pyramidal IO 3 groups are known for phosphates in the NASICON structure type, silicate minerals such as beryl, benitoite, wadeite, and hilairite, and synthetic germanates [39].Some of them are shown in Figure 8a-g.The topology and symmetry of the blocks vary from high symmetrical 32, −3 up to centrosymmetric −1, or asymmetric 1.The latter is characteristic of building blocks in new iodate compounds (Figure 3b).The positions of IO 3 groups in the blocks are replaced by PO 4 , GeO 4 , or SiO 4 tetrahedra with a general formula (M(TO 4 ) 6 ).The key point is the method of block condensation: for highly charged P 5+ or I 5+ , sharing of PO 4 tetrahedra or pyramidal IO 3 groups between octahedral pairs is preferable in contrast to Ge 4+ or Si 4+ tetrahedra with vertex condensation.
One can assume the synthesis of such hypothetical compounds in which both iodate and tetrahedral groups would be present in one block.There is an example of borophosphate with BO 4 and PO 4 tetrahedra in NaIn[BP 2 O 8 (OH)] [40].Such blocks would be asymmetric in structure and provide promising properties to the crystals.Such blocks are found in many iodates and present stable structural configurations.Interestingly, the same configuration is valid for phosphates, silicates, and germanates with the replacement of the umbrella-like IO3 groups (also described as tetrahedral) with six apical PO4, SiO4, or GeO4 tetrahedra.The blocks have different topologies and symmetry with point groups of 3, 32, −3, −1, and 1 regardless of the class of compounds.They are predominantly isolated from each other, but, in rare structures, are condensed into chains, layers, or frameworks.The method of block condensation is different: highly charged P 5+ or I 5+ , tetrahedra, or pyramidal IO3 groups are shared between octahedral pairs in contrast to vertex condensation of Ge 4+ or Si 4+ tetrahedra.The transformation of block symmetry from centrosymmetric to polar due to F introduction or the influence of alkali metals from the second coordination sphere leads to the manifestation of optical nonlinearity, as was discovered in Sn(IO3)2F2 [22] or Rb3Sc(IO3)6 [17].The polar orientation of additional isolated IO3 groups enhances such properties.
15,  x FOR PEER REVIEW was calculated on the base of the .ciffile using the program Powder Cell[31].The lated pattern matches well with the experimental one.
−1 can be attributed to translational vibrations of cation-oxygen.The resulting spectrum does not contain absorption bands related to deformation (angular) vibrations (O-I-O) in the [IO 3 ] groups, since the wave numbers of these vibrations are below 400 cm −1 .vibrations (O-I-O) in the [IO3] groups, since the wave numbers of these v below 400 cm −1 .

Figure 2 .
Figure 2. IR absorption spectrum of Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 ; *-absorption bands of Vaseline oil.Differential thermal analyses (DTA) measurements were performed by means of STA 449 F5 Jupiter equipment (Netzsch, Selb, Germany) in the temperature range of 50-1000 • C with a heating rate of 20 • C/min in Ar gas flow.A PtRh20 crucible of 85 µL volume was used in the DTA experiments.The decomposition of the sample (Figure 3) begins at a temperature of 494 • C, with a sharp weight loss and the successive formation of several intermediate phases with decomposition temperatures of 536 and 566 • C. Weight loss in this case is 46%.With further heating, the final stable phase melts at a temperature of 626 • C, the melt decomposes at a rate that increases with increasing temperature up to 914 • C. The weight loss in this case reaches 94% of the initial mass of the sample.The final crystalline phase is stable at 1000 • C and does not experience any phase transitions upon further cooling of the sample to room temperature.

Figure 4 .
Figure 4. Image of crystal used in a diffraction experiment from hydrothermal experimen orless transparent crystal has sizes of 0.230 × 0.195 × 0.140 mm.

Figure 4 .
Figure 4. Image of crystal used in a diffraction experiment from hydrothermal experiments: a colorless transparent crystal has sizes of 0.230 × 0.195 × 0.140 mm.

Figure 5 .
Figure 5. Crystal structure of Cs 5 [Sc 2 (IO 3 ) 9 ](IO 3 ) 2 in ac projection (a); [Sc(IO 3 ) 6 ] 3− building blocks with centrosymmetric configuration of Sc1 and Sc2 and asymmetric of Sc3 (b); Sc octahedra are shown in yellow, IO 3 groups and Cs atoms are shown as ball-and-stick presentation-Cs in white, I in orange, O in red in IO 3 groups in [Sc(IO 3 ) 6 ] 3− building blocks, and green for free IO 3 groups.

Figure 7 .
Figure 7. Crystal structures of KSc(IO3)Cl (a) and Cs3[Ta(IO3)6](IO3)2 (b) in diagonal projection.All the atoms are shown in ball-and-stick presentation, K and Cs in white, I in orange, Cl in green, and O in red balls.

Figure 7 .
Figure 7. Crystal structures of KSc(IO 3 )Cl (a) and Cs 3 [Ta(IO 3 ) 6 ](IO 3 ) 2 (b) in diagonal projection.All the atoms are shown in ball-and-stick presentation, K and Cs in white, I in orange, Cl in green, and O in red balls.