Structures of dipotassium rubidium citrate monohydrate, K₂RbC₆H₅O₇(H₂O), and potassium dirubidium citrate monohydrate, KRb₂C₆H₅O₇(H₂O), from laboratory X-ray powder diffraction data and DFT calculations

The crystal structures of the isostructural mixed-cation compounds dipotassium rubidium citrate monohydrate and potassium dirubidium citrate monohydrate have been solved and refined using laboratory X-ray powder diffraction data and optimized using density functional techniques.

Abstract

The crystal structures of the isostructural compounds dipotassium rubidium citrate monohydrate, K₂RbC₆H₅O₇(H₂O), and potassium dirubidium citrate monohydrate, KRb₂C₆H₅O₇(H₂O), have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The compounds are isostructural to K₃C₆H₅O₇(H₂O) and Rb₃C₆H₅O₇(H₂O), but exhibit different degrees of ordering of the K and Rb cations over the three metal-ion sites. The K and Rb site occupancies correlate well to both the bond-valence sums and the DFT energies of ordered cation systems. The MO₆ and MO₇ coordination polyhedra share edges to form a three-dimensional framework. The water mol­ecule acts as a donor in two strong charge-assisted O—H⋯O hydrogen bonds to carboxyl­ate groups. The hydroxyl group of the citrate anion forms an intra­molecular hydrogen bond to one of the central carboxyl­ate oxygen atoms.

Chemical context  

A systematic study of the crystal structures of Group 1 (alkali metal) citrate salts has been reported in Rammohan & Kaduk (2018 ▸). The study was extended to lithium metal hydrogen citrates in Cigler & Kaduk (2018 ▸), to sodium metal hydrogen citrates in Cigler & Kaduk (2019a ▸), to sodium dirubidium citrates in Cigler & Kaduk (2019b ▸), to dilithium potassium citrate (Cigler & Kaduk, 2019c ▸), to lithium dipotassium citrate monohydrate in Cigler & Kaduk (2020 ▸), and to potassium rubidium hydrogen citrate in Gonzalez et al. (2020 ▸). These compounds represent further extensions to potassium rubidium citrates. The crystal structure of K₃C₆H₅O₇(H₂O), Cambridge Structural Database refcode ZZZHVI* has been reported multiple times (Burns & Iball, 1954 ▸; Carrell et al., 1987 ▸), and the structure of Rb₃C₆H₅O₇(H₂O) has been reported by Rammohan & Kaduk (2017 ▸).

Structural commentary  

The crystal structures of dipotassium rubidium citrate monohydrate K₂RbC₆H₅O₇(H₂O), (I), and potassium dirubidium citrate monohydrate KRb₂C₆H₅O₇(H₂O), (II), have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The two compounds are isostructural (Fig. 1 ▸). The powder patterns (Fig. 2 ▸) and the unit cells show that these compounds are isostructural to K₃C₆H₅O₇(H₂O) and Rb₃C₆H₅O₇(H₂O). In each compound, the K and Rb cations are disordered over the three cation sites: in (I), the K/Rb site occupancies are 0.93/0.07, 0.64/0.36, and 0.53/0.47 for the K19/Rb20, K21/Rb22 and K23/Rb24 sites, respectively and in (II) the refined K/Rb occupancies are 0.62/0.38, 0.39/0.61 and 0.36/0.64 for the same metal sites. The refined site occupancies correlate well to the bond-valence sums calculated for K and Rb at each cation site (Fig. 3 ▸). DFT calculations on ordered cation systems show that in (I) occupation of site 19 by Rb is disfavored by 0.19 kcal mol⁻¹, while in (II) occupation of this site by K is favored by 0.28 kcal mol⁻¹. These trends are consistent with the refined occupancies, but the energy differences are within the expected errors for such calculations.

Figure 1.

Overlay of the crystal structures of (I) and (II), viewed approximately down the a-axis direction.

Figure 2.

Comparison of the X-ray powder patterns (Mo K_α radiation) of K₃C₆H₅O₇(H₂O), K₂RbC₆H₅O₇(H₂O), KRb₂C₆H₅O₇(H₂O), and Rb₃C₆H₅O₇(H₂O).

Figure 3.

Correlations between the refined K and Rb site occupancies in (K,Rb)₃C₆H₅O₇(H₂O) and the bond valence sums for each cation at each of the three potential sites.

For (I), the root-mean-square Cartesian displacement of the non-H atoms of the citrate anion in the disordered refined structure and the ordered DFT-optimized structures is 0.114, 0.080, and 0.079 Å for Rb at site 19, 20, and 21 (Fig. 4 ▸). The average absolute difference in the cation positions is 0.085 (29) Å, and the average absolute difference in the position of the water oxygen atom is 0.26 (11) Å. For (II), the similar r.m.s. citrate-atom displacements are 0.077, 0.104, and 0.101 Å (Fig. 5 ▸). The average absolute difference in the cation positions is 0.084 (54) Å, and the average absolute difference in the position of the water mol­ecule oxygen atom is 0.28 (14) Å. The good agreement between the disordered refined structures and the ordered DFT-optimized structures provides confidence that the experimental structures are correct (van de Streek & Neumann, 2014 ▸).

Figure 4.

Comparison of the refined asymmetric unit of (I) (red) and the DFT-optimized structures with Rb at site 19 (blue), site 20 (green), and site 21 (purple).

Figure 5.

Comparison of the refined asymmetric unit of (II) (red) and the DFT-optimized structures with K at site 19 (blue), site 20 (green), and site 21 (purple).

Most of the citrate anion bond distances, bond angles and torsion angles in the experimental structures fall within the normal range indicated by a Mercury Mogul Geometry Check (Macrae et al., 2020 ▸). Only the O12—C1—C2 [113.9 (5) and 114.7 (5)°; average = 124 (3)°, Z-score = 3.6 and 3.3] and the O13—C5—C4 angles [114.4 (5) and 115.1 (5)°; average = 124 (5)°, Z-score = 5.1 and 4.8] are flagged as unusual. The citrate anion occurs in the trans, trans-conformation (about C2—C3 and C3—C4), which is one of the two low-energy conformations of an isolated citrate anion (Rammohan & Kaduk, 2018 ▸) and is typical for citrate salts of the larger Group 1 cations. The central carboxyl­ate group and the hydroxyl group exhibit small twist angles [O17—C3—C6—O16 torsion angle = −6 (2) and 0.5 (2)°] from the normal planar arrangement. The Mulliken overlap populations indicate that the K—O and Rb—O bonds are ionic. M19/20 is six-coordinate, and M21/22 and M23/24 are seven-coordinate. The water mol­ecule coordinates to M19/20 and M21/22.

There is extensive chelation of the citrate anion to the metal ions. The carboxyl­ate groups O11/O12 and O15/O16 chelate to separate metal cations 21/22. The terminal carboxyl­ate O12 and central carboxyl­ate O15 and O16 oxygen atoms chelate to M23/24 and M19/20. The terminal carboxyl­ate O14 and the central carboxyl­ate O15 and O16 chelate to M19/20 and M23/24. The hydroxyl O17 and terminal carboxyl­ate O11 and O13 chelate to M21/22 and M23/24.

The Bravais–Friedel–Donnay–Harker (Bravais, 1866 ▸; Friedel, 1907 ▸; Donnay & Harker, 1937 ▸) method suggests that we might expect blocky morphology for these two compounds. No preferred orientation model was necessary in the refinement.

Supra­molecular features  

The MO₆ and MO₇ coordination polyhedra in both structures share edges to form a three-dimensional framework (Fig. 6 ▸). The hydro­phobic methyl­ene group sides of the citrate anions occupy channels in the framework. The hydrogen bonds in the six ordered systems used for the DFT calculations differ slightly but the general pattern is similar: Tables 1 ▸–3 ▸ ▸ list the geometrical data for (I) with the Rb atom placed at the M19, M21 and M23 sites, respectively and the K atoms occupying the other two sites. Tables 4 ▸–6 ▸ ▸ present data for (II) with the K atom occupying the M19, M21 and M23 sites, respectively and the Rb atoms occupying the other two sites. The water mol­ecule O25/H26/H27 forms strong charge-assisted hydrogen bonds to the central carboxyl­ate oxygen atom O15 and the terminal carboxyl­ate O13. The energies of the O—H⋯O hydrogen bonds were calculated using the correlation of Rammohan & Kaduk (2018 ▸). The hydroxyl group O17 forms an intra­molecular hydrogen bond to the central carboxyl­ate O16. In some of the ordered models, the hydroxyl group also forms an inter­molecular hydrogen bond to the terminal carboxyl­ate O13.

Figure 6.

Crystal structure of K₂RbC₆H₅O₇(H₂O) and KRb₂C₆H₅O₇(H₂O) (shown for K₂RbC₆H₅O₇(H₂O)), viewed down the b-axis.

Table 1. Hydrogen-bond geometry (Å, °) for (I) M19 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O17—H18⋯O16	0.98	1.99	2.598	118
O17—H18⋯O13i	0.98	2.35	3.196	145
O25—H26⋯O13ii	0.99	1.66	2.641	174
O25—H27⋯O15	0.99	1.68	2.662	176

Symmetry codes: (i) ; (ii) .

Table 2. Hydrogen-bond geometry (Å, °) for (I) M20 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O17—H18⋯O16	0.98	1.96	2.598	118
O17—H18⋯O13i	0.98	2.37	3.203	142
O25—H26⋯O13ii	0.99	1.68	2.662	171
O25—H27⋯O15	0.98	1.72	2.696	176

Symmetry codes: (i) ; (ii) .

Table 3. Hydrogen-bond geometry (Å, °) for (I) M21 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O17—H18⋯O16	0.98	1.97	2.594	120
O17—H18⋯O13i	0.98	2.33	3.124	138
O25—H26⋯O13ii	0.99	1.66	2.643	175
O25—H27⋯O15	0.98	1.71	2.696	175

Symmetry codes: (i) ; (ii) .

Table 4. Hydrogen-bond geometry (Å, °) for (II) M19 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O17—H18⋯O16	0.98	1.93	2.579	122
O17—H18⋯O13i	0.98	2.45	3.220	136
O25—H26⋯O13ii	0.99	1.68	2.660	173
O25—H27⋯O15	0.98	1.72	2.700	174

Symmetry codes: (i) ; (ii) .

Table 5. Hydrogen-bond geometry (Å, °) for (II) M20 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O17—H18⋯O16	0.98	1.98	2.596	118
O25—H26⋯O13i	0.99	1.66	2.648	177
O25—H27⋯O15	0.99	1.69	2.671	177

Symmetry code: (i) .

Table 6. Hydrogen-bond geometry (Å, °) for (II) M21 .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O17—H18⋯O16	0.98	1.94	2.582	121
O25—H26⋯O13i	0.99	1.66	2.642	173
O25—H27⋯O15	0.98	1.69	2.669	175

Symmetry code: (i) .

Database survey  

Details of the comprehensive literature search for citrate structures are presented in Rammohan & Kaduk (2018 ▸). The powder pattern of K₂RbC₆H₅O₇(H₂O) was indexed on a primitive monoclinic unit cell having a = 7.2676, b = 11.8499, c = 13.1006 A, β = 98.234°, V = 1116.61 ų using DICVOL14 (Louër & Boultif, 2014 ▸). A similar cell was obtained using N-TREOR (Altomare et al., 2013 ▸). Analysis of the systematic absences using EXPO2014 (Altomare et al., 2013 ▸) suggested the space group of P2 ₁/n. The pattern of KRb₂C₆H₅O₇(H₂O) was indexed on a similar unit cell using N-TREOR, so the compounds were assumed to be isostructural. Reduced cell searches in the Cambridge Structural Database (Groom et al., 2016 ▸) yielded ten10 hits, including four for K₃C₆H₅O₇(H₂O), ZZZHVI* (Burns & Iball, 1954 ▸; Carrell et al., 1987 ▸; Rammohan & Kaduk, 2018 ▸).

Synthesis and crystallization  

Dipotassium rubidium citrate monohydrate, (I), was synthesized by adding stoichiometric qu­anti­ties of 1.382 g K₂CO₃ (Sigma–Aldrich) and 1.154 g Rb₂CO₃ (Sigma–Aldrich) to a solution of 2.03 g citric acid monohydrate (10.0 mmol, Sigma–Aldrich) in 10 ml of water. After the fizzing subsided, the clear solution was dried in a 403 K oven to yield a white solid. Potassium dirubidium citrate monohydrate, (II), was synthesized in the same way starting from 0.691 g of K₂CO₃ and 2.309 g of Rb₂CO₃.

Refinement  

Crystal data, data collection and structure refinement details for (I) are summarized in Table 7 ▸ (Fig. 7 ▸). To minimize Rb fluorescence, the pulse height discriminator lower level of the X’Celerator detector was raised from the default 39.0% to 51.0%. The structure was solved with FOX (Favre-Nicolin & Černý, 2002 ▸), using 2 K atoms, 1 Rb atom and a citrate anion as fragments. A Le Bail fit yielded R _wp = 3.73%. Initial refinement did not include the water mol­ecule, and yielded an acceptable fit (R _wp = 4.8%), but the U _iso values of the C atoms in the central part of the mol­ecule were relatively large (∼0.10 Ų). The bond-valence sums of the cations were, however, far too low, showing that the water mol­ecule was indeed present. It was inserted in the position from the known monohydrate structures.

Table 7. Experimental details.

	(I)	(II)
Crystal data
Chemical formula	2K+·Rb+·C6H5O7 3−·H2O	K+·2Rb+·C6H5O7 3−·H2O
M r	365.78	399.97
Crystal system, space group	Monoclinic, P21/n	Monoclinic, P21/n
Temperature (K)	300	300
a, b, c (Å)	7.2407 (10), 11.8145 (3), 13.062 (2)	7.3507 (5), 11.8468 (4), 13.2275 (12)
β (°)	98.334 (7)	98.109 (4)
V (Å3)	1105.56 (9)	1140.37 (6)
Z	4	4
Radiation type	Kα1,2, λ = 0.70932, 0.71361 Å	Kα1,2, λ = 0.70932, 0.71361 Å
Specimen shape, size (mm)	Cylinder, 12 × 0.5	Cylinder, 12 × 0.5
Data collection
Diffractometer	PANalytical Empyrean	PANalytical Empyrean
Specimen mounting	Glass capillary	Glass capillary
Data collection mode	Transmission	Transmission
Scan method	Step	Step
2θ values (°)	2θmin = 1.021 2θmax = 49.985 2θstep = 0.017	2θmin = 1.021 2θmax = 49.985 2θstep = 0.017
Refinement
R factors and goodness of fit	R p = 0.026, R wp = 0.033, R exp = 0.018, R(F 2) = 0.04795, χ2 = 3.549	R p = 0.024, R wp = 0.032, R exp = 0.018, R(F 2) = 0.06949, χ2 = 3.426
No. of parameters	70	70
No. of restraints	29	29
H-atom treatment	Only H-atom displacement parameters refined	Only H-atom displacement parameters refined
(Δ/σ)max	0.205	0.722

Computer programs: FOX (Favre-Nicolin & Černý, 2002 ▸), GSAS-II (Toby & Von Dreele, 2013 ▸), Mercury (Macrae et al., 2020 ▸), Materials Studio (Dassault Systems, 2019 ▸), DIAMOND (Crystal Impact, 2015 ▸) and publCIF (Westrip, 2010 ▸).

Figure 7.

Rietveld plot for (I). The blue crosses represent the observed data points, and the green line is the calculated pattern. The cyan curve is the normalized error plot. The vertical scale has been multiplied by a factor of 3× for 2θ > 26.0°. The row of blue tick marks indicates the calculated reflection positions. The red line is the background curve.

The structure was refined by the Rietveld method using GSAS-II (Toby & Von Dreele, 2013 ▸). The hydrogen atoms were included in fixed positions, which were recalculated during the course of the refinement using Materials Studio (Dassault Systems, 2019 ▸). All C—C and C—O bond distances and all bond angles were restrained based on previous citrate structures: C1—C2 = C4—C5 = 1.51 (1) Å, C2—C3 = C3—C4 = 1.54 (1) Å, C3—C6 = 1.55 (1) Å, C3—O17 = 1.42 (3) Å, C(carbox­yl)—O(carbox­yl) = 1.27 (3) Å, C1—C2—C3 = C3—C4—C5 = 115 (3)°, all angles about C3 = 109 (3)°, carboxyl C—C—O = 115 (3)°, and carboxyl O—C—O = 130 (3)°. Each of the three cation sites was modeled as a mixture of K and Rb; the sums of the site occupancies were constrained to be unity, but the total K and Rb contents were not constrained/restrained, to provide an inter­nal consistency check. The U _iso of the atoms in the central and outer portions of the citrate anion were constrained to be equal, and the U _iso of the hydrogen atoms were constrained to be 1.3× those of the atoms to which they are attached. The U_iso of the cations were constrained to be equal. A capillary absorption model (fixed μ.R = 0.84, calculated using the tool on the 11-BM web site) was included into the refinement. A Chebyschev polynomial function with four coefficients, along with a peak at 13.11° to model the scattering of the glass capillary, was used to model the background.

Because DFT techniques cannot accommodate disordered systems, three density functional geometry optimizations (with Rb at each of the three cations sites, and K at the other two) were carried out using CRYSTAL14 (Dovesi et al., 2014 ▸). The basis sets for the H, C, N, and O atoms were those of Gatti et al. (1994 ▸), and the basis sets for K and Rb were those of Peintinger et al. (2013 ▸). The calculations were run on eight 2.1 GHz Xeon cores (each with 6 Gb RAM) of a 304-core Dell Linux cluster at IIT, using 8 k-points and the B3LYP functional.

Crystal data, data collection and structure refinement details for (II) are summarized in Table 7 ▸ (Fig. 8 ▸). The same solution and refinement strategy as for (I) was followed. Three density functional geometry optimizations (with K at each of the three cations sites, and Rb at the other two) were carried out using CRYSTAL17 (Dovesi et al., 2018 ▸) with atom basis sets and computer hardware as described in the previous paragraph.

Figure 8.

Rietveld plot for (II). The blue crosses represent the observed data points, and the green line is the calculated pattern. The cyan curve is the normalized error plot. The vertical scale has been multiplied by a factor of 3× for 2θ > 26.0°. The row of blue tick marks indicates the calculated reflection positions. The red line is the background curve.

Supplementary Material

CCDC references: 2025972, 2025973, 2025974, 2025975, 2025976, 2025977, 2025978, 2025979

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Dipotassium rubidium citrate monohydrate (I). Crystal data

2K+·Rb+·C6H5O73−·H2O	V = 1105.56 (9) Å3
Mr = 365.78	Z = 4
Monoclinic, P21/n	Dx = 2.198 Mg m−3
Hall symbol: -P 2yn	Kα1,2 radiation, λ = 0.70932, 0.71361 Å
a = 7.2407 (10) Å	T = 300 K
b = 11.8145 (3) Å	white
c = 13.062 (2) Å	cylinder, 12 × 0.5 mm
β = 98.334 (7)°	Specimen preparation: Prepared at 403 K

Dipotassium rubidium citrate monohydrate (I). Data collection

PANalytical Empyrean diffractometer	Data collection mode: transmission
Radiation source: sealed X-ray tube	Scan method: step
Specimen mounting: Glass capillary	2θmin = 1.021°, 2θmax = 49.985°, 2θstep = 0.017°

Dipotassium rubidium citrate monohydrate (I). Refinement

Least-squares matrix: full	29 restraints
Rp = 0.026	15 constraints
Rwp = 0.033	Only H-atom displacement parameters refined
Rexp = 0.018	Weighting scheme based on measured s.u.'s
R(F2) = 0.04795	(Δ/σ)max = 0.205
2931 data points	Background function: Background function: "chebyschev-1" function with 4 terms: 2307(6), -280(6), 22(5), -43(4), Background peak parameters: pos, int, sig, gam: 10.29(6), 1.13(5)e5, 2.80(23)e4, 0.100,
Profile function: Finger-Cox-Jephcoat function parameters U, V, W, X, Y, SH/L: peak variance(Gauss) = Utan(Th)2+Vtan(Th)+W: peak HW(Lorentz) = X/cos(Th)+Ytan(Th); SH/L = S/L+H/L U, V, W in (centideg)2, X & Y in centideg 19.949, 12.795, 0.000, 2.075, 0.000, 0.032, Crystallite size in microns with "isotropic" model: parameters: Size, G/L mix 1.000, 1.000, Microstrain, "generalized" model (106 * delta Q/Q) parameters: S400, S040, S004, S220, S202, S022, S301, S103, S121, G/L mix 21847.124, 158.305, 5787.320, 10788.591, 22832.702, -379.772, 23098.342, 3225.801, 2172.138, 1.000,	Preferred orientation correction: Spherical Harmonics correction. Order = 2 Model: cylindrical Orientation angles: omega = 0.00; chi = 0.00; phi = 0.00; Coefficients: 0::C(2,0,-2) = -0.0803; 0::C(2,0,0) = 0.1239; 0::C(2,0,2) = 0.2546; Simple spherical harmonic correction Order = 2 Coefficients: 0:0:C(2,-2) = 0.0000; 0:0:C(2,0) = 0.0000; 0:0:C(2,2) = 0.0000
70 parameters

Dipotassium rubidium citrate monohydrate (I). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	0.385 (2)	0.3957 (7)	0.1274 (12)	0.033 (4)*
C2	0.3114 (18)	0.2874 (6)	0.1675 (13)	0.016 (6)*
C3	0.4195 (10)	0.1791 (7)	0.1480 (7)	0.016*
C4	0.3077 (19)	0.0749 (7)	0.1745 (12)	0.016*
C5	0.358 (2)	−0.0357 (7)	0.1277 (11)	0.033*
C6	0.6126 (11)	0.1800 (17)	0.2170 (9)	0.033*
H7	0.31533	0.29370	0.25488	0.021*
H8	0.15997	0.27640	0.13043	0.021*
H9	0.32956	0.06167	0.26187	0.021*
H10	0.15318	0.09193	0.14804	0.021*
O11	0.267 (3)	0.4511 (11)	0.0657 (13)	0.033*
O12	0.535 (2)	0.4299 (12)	0.1794 (12)	0.033*
O13	0.236 (3)	−0.0732 (15)	0.0569 (13)	0.033*
O14	0.489 (2)	−0.0890 (10)	0.1815 (12)	0.033*
O15	0.6078 (18)	0.186 (2)	0.3140 (9)	0.033*
O16	0.7512 (13)	0.1662 (17)	0.1688 (11)	0.033*
O17	0.4449 (16)	0.1744 (11)	0.0424 (8)	0.033*
H18	0.51930	0.13650	0.01110	0.043*
K19	−0.1246 (11)	0.4396 (6)	0.1156 (8)	0.0280 (14)*	0.928
Rb20	−0.1246	0.4396	0.1156	0.0280*	0.072
K21	0.9916 (7)	0.1613 (4)	0.3832 (5)	0.0280*	0.645
Rb22	0.9916	0.1613	0.3832	0.0280*	0.355
K23	0.8338 (8)	−0.0689 (4)	0.1125 (4)	0.0280*	0.534
Rb24	0.8338	−0.0689	0.1125	0.0280*	0.466
O25	0.374 (3)	0.2108 (17)	0.4690 (15)	0.080 (11)*
H26	0.34120	0.28290	0.45890	0.104*
H27	0.44720	0.20590	0.41980	0.104*

Dipotassium rubidium citrate monohydrate (I). Geometric parameters (Å, º)

C1—C2	1.5094 (19)	K19—O11	3.00 (2)
C1—O11	1.269 (5)	K19—O11i	2.763 (16)
C1—O12	1.263 (6)	K19—O12iv	2.714 (19)
C2—C1	1.5094 (19)	K19—O14ix	2.711 (18)
C2—C3	1.5398 (19)	K19—O15ix	3.05 (3)
C3—C2	1.5398 (19)	Rb20—O11	3.00 (2)
C3—C4	1.5398 (19)	Rb20—O11i	2.763 (13)
C3—C6	1.5501 (19)	Rb20—O12iv	2.714 (17)
C3—O17	1.419 (5)	Rb20—O14ix	2.711 (15)
C4—C3	1.5398 (19)	Rb20—O15ix	3.05 (2)
C4—C5	1.5100 (19)	Rb20—O25viii	2.61 (2)
C5—C4	1.5100 (19)	K21—O11vii	3.055 (16)
C5—O13	1.263 (5)	K21—O12vii	2.852 (15)
C5—O14	1.261 (5)	K21—O14ii	3.077 (14)
C6—C3	1.5501 (19)	K21—O15	2.809 (14)
C6—O15	1.273 (5)	K21—O16	3.076 (16)
C6—O16	1.271 (5)	K21—O17x	2.899 (12)
O11—C1	1.269 (5)	K21—O25iii	2.89 (2)
O11—K19	3.00 (2)	Rb22—O11vii	3.055 (15)
O11—K19i	2.763 (16)	Rb22—O12vii	2.852 (14)
O11—K21ii	3.055 (16)	Rb22—O14ii	3.077 (13)
O12—C1	1.263 (6)	Rb22—O15	2.809 (13)
O12—K19iii	2.714 (19)	Rb22—O16	3.076 (13)
O12—K21ii	2.852 (15)	Rb22—O17x	2.899 (11)
O12—K23ii	2.746 (15)	Rb22—O25iii	2.89 (2)
O13—C5	1.263 (5)	K23—O12vii	2.746 (15)
O13—K23iv	3.11 (2)	K23—O13iii	3.11 (2)
O13—K23v	2.766 (19)	K23—O13v	2.766 (19)
O14—C5	1.261 (5)	K23—O14	2.784 (16)
O14—K19vi	2.711 (18)	K23—O15vii	3.07 (2)
O14—K21vii	3.077 (14)	K23—O16	2.96 (2)
O14—K23	2.784 (16)	K23—O17v	2.922 (14)
O15—C6	1.273 (5)	Rb24—O12vii	2.746 (15)
O15—K19vi	3.05 (3)	Rb24—O13iii	3.11 (2)
O15—K21	2.809 (14)	Rb24—O13v	2.766 (19)
O15—K23ii	3.07 (2)	Rb24—O14	2.784 (16)
O16—C6	1.271 (5)	Rb24—O15vii	3.07 (2)
O16—K21	3.076 (16)	Rb24—O16	2.957 (18)
O16—K23	2.96 (2)	Rb24—O17v	2.922 (13)
O17—C3	1.419 (5)	O25—K19x	2.61 (2)
O17—K21viii	2.899 (12)	O25—K21iv	2.89 (2)
O17—K23v	2.922 (14)
C2—C1—O11	114.7 (5)	O11i—K19—O25viii	74.2 (5)
C2—C1—O12	113.9 (5)	O12iv—K19—O25viii	106.8 (6)
O11—C1—O12	128.8 (5)	O14ix—K19—O25viii	126.5 (6)
C1—C2—C3	115.7 (5)	K19i—K19—O25viii	69.1 (5)
C2—C3—C4	109.32 (17)	K21ix—K19—O25viii	123.5 (5)
C2—C3—C6	109.59 (17)	K21xi—K19—O25viii	46.3 (4)
C4—C3—C6	109.52 (17)	O11i—Rb20—O12iv	92.3 (4)
C2—C3—O17	109.46 (17)	O11i—Rb20—O14ix	159.0 (4)
C4—C3—O17	109.51 (17)	O12iv—Rb20—O14ix	84.9 (5)
C6—C3—O17	109.43 (17)	O11i—Rb20—O25viii	74.2 (5)
C3—C4—C5	115.7 (5)	O12iv—Rb20—O25viii	106.8 (6)
C4—C5—O13	114.5 (5)	O14ix—Rb20—O25viii	126.5 (5)
C4—C5—O14	114.4 (5)	O12vii—Rb22—O15	89.0 (6)
O13—C5—O14	128.3 (5)	O12vii—Rb22—O17x	146.8 (4)
C3—C6—O15	115.3 (4)	O15—Rb22—O17x	87.1 (4)
C3—C6—O16	114.9 (4)	O12vii—Rb22—O25iii	109.1 (5)
O15—C6—O16	129.5 (5)	O15—Rb22—O25iii	162.0 (6)
C1—O11—K19i	156.8 (15)	O17x—Rb22—O25iii	78.0 (4)
C1—O12—K19iii	126.7 (14)	O12vii—K23—O13v	142.4 (5)
C1—O12—K23ii	132.9 (11)	O12vii—Rb24—O13v	142.4 (4)
K19iii—O12—K23ii	96.1 (6)	O12vii—Rb24—O14	82.9 (5)
C5—O13—K23v	113.6 (12)	O13v—Rb24—O14	104.0 (4)
C5—O14—K19vi	128.2 (8)	O12vii—Rb24—O17v	142.0 (4)
O11i—K19—O12iv	92.3 (5)	O13v—Rb24—O17v	71.1 (4)
O11i—K19—O14ix	159.0 (6)	O14—Rb24—O17v	68.0 (4)
O12iv—K19—O14ix	84.9 (6)

Symmetry codes: (i) −x, −y+1, −z; (ii) −x+3/2, y+1/2, −z+1/2; (iii) x+1, y, z; (iv) x−1, y, z; (v) −x+1, −y, −z; (vi) −x+1/2, y−1/2, −z+1/2; (vii) −x+3/2, y−1/2, −z+1/2; (viii) x+1/2, −y+3/2, z+1/2; (ix) −x+1/2, y+1/2, −z+1/2; (x) x+3/2, −y+3/2, z+3/2; (xi) x−1/2, −y+3/2, z+1/2.

(I_19_DFT). Crystal data

C6H7K2O8Rb	b = 11.8185 Å
Mr = 370.73	c = 13.0617 Å
Monoclinic, P21/n	β = 98.3340°
Hall symbol: -P 2yn	V = 1105.95 Å3
a = 7.24070 Å	Z = 4

(I_19_DFT). Data collection

h = →	l = →
k = →

(I_19_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.387602	0.396247	0.134453	0.03300*
C2	0.300752	0.285078	0.161529	0.01600*
C3	0.414116	0.177979	0.149608	0.01600*
C4	0.291736	0.078893	0.178301	0.01600*
C5	0.334003	−0.034533	0.132030	0.03300*
C6	0.607979	0.177590	0.217853	0.03300*
H7	0.270788	0.289262	0.240834	0.02100*
H8	0.169692	0.273835	0.110202	0.02100*
H9	0.306865	0.072548	0.262250	0.02100*
H10	0.146495	0.099677	0.150816	0.02100*
O11	0.304860	0.450602	0.058045	0.03300*
O12	0.533995	0.429648	0.191070	0.03300*
O13	0.215316	−0.069216	0.056951	0.03300*
O14	0.478172	−0.088049	0.169573	0.03300*
O15	0.612096	0.186020	0.315093	0.03300*
O16	0.748786	0.165708	0.173006	0.03300*
O17	0.441499	0.169428	0.042803	0.03300*
H18	0.572418	0.148527	0.042548	0.04300*
Rb19	−0.115564	0.432699	0.114377	0.02800*
K20	−0.016156	0.159711	0.384860	0.02800*
K21	0.829410	−0.070765	0.109841	0.02800*
O25	0.354682	0.211581	0.439575	0.08000*
H26	0.328247	0.293138	0.446004	0.10400*
H27	0.445803	0.203599	0.390877	0.10400*

(I_19_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O16	0.98	1.99	2.598	118
O17—H18···O13i	0.98	2.35	3.196	145
O25—H26···O13ii	0.99	1.66	2.641	174
O25—H27···O15	0.99	1.68	2.662	176

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1/2, y+1/2, −z+1/2.

(I_20_DFT). Crystal data

C6H7K2O8Rb	b = 11.81851 Å
Mr = 370.73	c = 13.06177 Å
Monoclinic, P21/n	β = 98.3340°
Hall symbol: -P 2yn	V = 1105.95 Å3
a = 7.24070 Å	Z = 4

(I_20_DFT). Data collection

h = →	l = →
k = →

(I_20_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.381013	0.394055	0.130708	0.03300*
C2	0.293184	0.285132	0.162434	0.01600*
C3	0.402898	0.176581	0.151416	0.01600*
C4	0.280001	0.078045	0.180294	0.01600*
C5	0.331506	−0.034836	0.136729	0.03300*
C6	0.595245	0.173140	0.220658	0.03300*
H7	0.271064	0.293099	0.242888	0.02100*
H8	0.157764	0.275194	0.114842	0.02100*
H9	0.292673	0.072933	0.264274	0.02100*
H10	0.135438	0.097397	0.149747	0.02100*
O11	0.281987	0.455743	0.064950	0.03300*
O12	0.544521	0.418712	0.173263	0.03300*
O13	0.223087	−0.071101	0.058155	0.03300*
O14	0.475237	−0.085389	0.180008	0.03300*
O15	0.598209	0.186110	0.317414	0.03300*
O16	0.735216	0.152795	0.177058	0.03300*
O17	0.432382	0.165351	0.045123	0.03300*
H18	0.563594	0.143536	0.047223	0.04300*
K19	−0.115017	0.445349	0.113268	0.02800*
Rb20	−0.002640	0.165932	0.384727	0.02800*
K21	0.828073	−0.069128	0.116190	0.02800*
O25	0.395879	0.216870	0.472957	0.08000*
H26	0.348848	0.295195	0.468149	0.10400*
H27	0.464202	0.205158	0.414130	0.10400*

(I_20_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O16	0.98	1.96	2.598	118
O17—H18···O13i	0.98	2.37	3.203	142
O25—H26···O13ii	0.99	1.68	2.662	171
O25—H27···O15	0.98	1.72	2.696	176

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1/2, y+1/2, −z+1/2.

(I_21_DFT). Crystal data

C6H7K2O8Rb	b = 11.81851 Å
Mr = 370.73	c = 13.06177 Å
Monoclinic, P21/n	β = 98.3340°
Hall symbol: -P 2yn	V = 1105.95 Å3
a = 7.24070 Å	Z = 4

(I_21_DFT). Data collection

h = →	l = →
k = →

(I_21_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.382779	0.395000	0.126384	0.03300*
C2	0.303121	0.285782	0.163456	0.01600*
C3	0.416131	0.178071	0.152587	0.01600*
C4	0.292970	0.079198	0.180960	0.01600*
C5	0.340745	−0.036619	0.141034	0.03300*
C6	0.608466	0.175258	0.222408	0.03300*
H7	0.283206	0.295370	0.244113	0.02100*
H8	0.166028	0.272600	0.118520	0.02100*
H9	0.302026	0.076170	0.264923	0.02100*
H10	0.149042	0.098595	0.149226	0.02100*
O11	0.276815	0.453687	0.061403	0.03300*
O12	0.547206	0.422937	0.164156	0.03300*
O13	0.230533	−0.074038	0.063533	0.03300*
O14	0.479179	−0.089554	0.186680	0.03300*
O15	0.609842	0.181247	0.319718	0.03300*
O16	0.750451	0.162898	0.178807	0.03300*
O17	0.446845	0.169433	0.046354	0.03300*
H18	0.579348	0.151603	0.047775	0.04300*
K19	−0.112854	0.436953	0.108689	0.02800*
K20	−0.012954	0.157061	0.389284	0.02800*
Rb21	0.837466	−0.072521	0.114962	0.02800*
O25	0.361121	0.209555	0.452481	0.08000*
H26	0.324995	0.290235	0.450230	0.10400*
H27	0.446472	0.197835	0.401325	0.10400*

(I_21_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O16	0.98	1.97	2.594	120
O17—H18···O13i	0.98	2.33	3.124	138
O25—H26···O13ii	0.99	1.66	2.643	175
O25—H27···O15	0.98	1.71	2.696	175

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1/2, y+1/2, −z+1/2.

Potassium dirubidium citrate monohydrate (II). Crystal data

K+·2Rb+·C6H5O73−·H2O	V = 1140.37 (6) Å3
Mr = 399.97	Z = 4
Monoclinic, P21/n	Dx = 2.330 Mg m−3
Hall symbol: -P 2yn	Kα1,2 radiation, λ = 0.70932, 0.71361 Å
a = 7.3507 (5) Å	T = 300 K
b = 11.8468 (4) Å	white
c = 13.2275 (12) Å	cylinder, 12 × 0.5 mm
β = 98.109 (4)°	Specimen preparation: Prepared at 403 K

Potassium dirubidium citrate monohydrate (II). Data collection

PANalytical Empyrean diffractometer	Data collection mode: transmission
Radiation source: sealed X-ray tube	Scan method: step
Specimen mounting: glass capillary	2θmin = 1.021°, 2θmax = 49.985°, 2θstep = 0.017°

Potassium dirubidium citrate monohydrate (II). Refinement

Least-squares matrix: full	29 restraints
Rp = 0.024	15 constraints
Rwp = 0.032	Only H-atom displacement parameters refined
Rexp = 0.018	Weighting scheme based on measured s.u.'s
R(F2) = 0.06949	(Δ/σ)max = 0.722
2931 data points	Background function: Background function: "chebyschev-1" function with 4 terms: 2587(5), -233(6), 10(4), -28(4), Background peak parameters: pos, int, sig, gam: 10.54(5), 1.39(5)e5, 3.08(20)e4, 0.100,
Profile function: Finger-Cox-Jephcoat function parameters U, V, W, X, Y, SH/L: peak variance(Gauss) = Utan(Th)2+Vtan(Th)+W: peak HW(Lorentz) = X/cos(Th)+Ytan(Th); SH/L = S/L+H/L U, V, W in (centideg)2, X & Y in centideg 19.949, 12.795, 0.000, 2.075, 0.000, 0.032, Crystallite size in microns with "isotropic" model: parameters: Size, G/L mix 1.000, 1.000, Microstrain, "generalized" model (106 * delta Q/Q) parameters: S400, S040, S004, S220, S202, S022, S301, S103, S121, G/L mix 629.894, 666.269, 773.433, -118.805, -89.875, -165.278, 167.735, 57.322, 73.783, 1.000,	Preferred orientation correction: Spherical Harmonics correction. Order = 2 Model: cylindrical Orientation angles: omega = 0.00; chi = 0.00; phi = 0.00; Coefficients: 0::C(2,0,-2) = -0.0045; 0::C(2,0,0) = 0.1825; 0::C(2,0,2) = 0.1091; March-Dollase correction coef. = 1.000 axis = [0, 0, 1]
70 parameters

Potassium dirubidium citrate monohydrate (II). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	0.395 (3)	0.3900 (9)	0.1268 (15)	0.035 (5)*
C2	0.317 (2)	0.2852 (8)	0.1695 (15)	0.022 (8)*
C3	0.4170 (10)	0.1747 (9)	0.1508 (8)	0.022*
C4	0.303 (2)	0.0734 (8)	0.1788 (14)	0.022*
C5	0.348 (2)	−0.0379 (9)	0.1324 (16)	0.035*
C6	0.6080 (12)	0.173 (2)	0.2178 (11)	0.035*
H7	0.32318	0.29412	0.25575	0.028*
H8	0.16642	0.27663	0.13442	0.028*
H9	0.32518	0.06108	0.26513	0.028*
H10	0.15106	0.09267	0.15353	0.028*
O11	0.280 (3)	0.4464 (15)	0.0661 (16)	0.035*
O12	0.552 (3)	0.4191 (15)	0.1714 (16)	0.035*
O13	0.229 (3)	−0.0728 (16)	0.0599 (16)	0.035*
O14	0.489 (3)	−0.0872 (13)	0.1775 (16)	0.035*
O15	0.606 (2)	0.188 (3)	0.3132 (11)	0.035*
O16	0.7441 (14)	0.167 (2)	0.1683 (15)	0.035*
O17	0.4399 (19)	0.1676 (15)	0.0464 (9)	0.035*
H18	0.51790	0.14150	0.01080	0.046*
K19	−0.1195 (9)	0.4371 (6)	0.1136 (6)	0.0293 (13)*	0.621
Rb20	−0.1195	0.4371	0.1136	0.0293*	0.379
K21	0.9951 (6)	0.1642 (5)	0.3815 (5)	0.0293*	0.394
Rb22	0.9951	0.1642	0.3815	0.0293*	0.606
K23	0.8366 (8)	−0.0671 (5)	0.1150 (5)	0.0293*	0.356
Rb24	0.8366	−0.0671	0.1150	0.0293*	0.644
O25	0.387 (4)	0.205 (3)	0.456 (2)	0.122 (15)*
H26	0.34760	0.27190	0.45840	0.159*
H27	0.46070	0.20620	0.41170	0.159*

Potassium dirubidium citrate monohydrate (II). Geometric parameters (Å, º)

C1—C2	1.5099 (18)	O17—K23v	2.981 (16)
C1—O11	1.270 (5)	K19—O11	3.09 (3)
C1—O12	1.267 (5)	K19—O11i	2.855 (17)
C2—C1	1.5099 (18)	K19—O12iv	2.65 (2)
C2—C3	1.5403 (18)	K19—O14ix	2.81 (2)
C3—C2	1.5403 (18)	K19—O25viii	2.69 (3)
C3—C4	1.5402 (18)	Rb20—O11	3.09 (2)
C3—C6	1.5508 (18)	Rb20—O11i	2.855 (16)
C3—O17	1.417 (5)	Rb20—O12iv	2.65 (2)
C4—C3	1.5402 (18)	Rb20—O14ix	2.81 (2)
C4—C5	1.5104 (18)	Rb20—O15ix	3.12 (3)
C5—C4	1.5104 (18)	Rb20—O25viii	2.69 (3)
C5—O13	1.270 (5)	K21—O11vii	3.09 (2)
C5—O14	1.264 (5)	K21—O12vii	2.995 (19)
C6—C3	1.5508 (18)	K21—O14ii	3.053 (17)
C6—O15	1.277 (5)	K21—O15	2.890 (16)
C6—O16	1.272 (5)	K21—O17x	3.024 (15)
O11—C1	1.270 (5)	K21—O25iii	2.95 (3)
O11—K19	3.09 (3)	Rb22—O11vii	3.092 (19)
O11—K19i	2.855 (17)	Rb22—O12vii	2.995 (19)
O11—K21ii	3.09 (2)	Rb22—O14ii	3.053 (16)
O12—C1	1.267 (5)	Rb22—O15	2.890 (15)
O12—K19iii	2.65 (2)	Rb22—O16	3.145 (17)
O12—K21ii	2.995 (19)	Rb22—O17x	3.024 (14)
O12—K23ii	2.83 (2)	Rb22—O25iii	2.95 (3)
O13—C5	1.270 (5)	K23—O12vii	2.83 (2)
O13—K23iv	3.08 (3)	K23—O13iii	3.08 (3)
O13—K23v	2.83 (2)	K23—O13v	2.83 (2)
O14—C5	1.264 (5)	K23—O14	2.81 (2)
O14—K19vi	2.81 (2)	K23—O15vii	3.06 (3)
O14—K21vii	3.053 (17)	K23—O16	2.96 (2)
O14—K23	2.81 (2)	K23—O17v	2.981 (16)
O15—C6	1.277 (5)	Rb24—O12vii	2.83 (2)
O15—Rb20vi	3.12 (3)	Rb24—O13iii	3.08 (3)
O15—K21	2.890 (16)	Rb24—O13v	2.83 (2)
O15—K23ii	3.06 (3)	Rb24—O14	2.81 (2)
O16—C6	1.272 (5)	Rb24—O15vii	3.06 (3)
O16—Rb22	3.145 (17)	Rb24—O16	2.96 (2)
O16—K23	2.96 (2)	Rb24—O17v	2.981 (15)
O17—C3	1.417 (5)	O25—K19x	2.69 (3)
O17—K21viii	3.024 (15)	O25—K21iv	2.95 (3)
C2—C1—O11	114.5 (5)	O15—C6—O16	129.5 (5)
C2—C1—O12	114.7 (5)	C1—O12—K19iii	134.2 (17)
O11—C1—O12	129.2 (5)	O12iv—K19—O25viii	107.0 (8)
C1—C2—C3	115.05 (18)	O11i—Rb20—O12iv	89.6 (5)
C2—C3—C4	109.49 (17)	O11i—Rb20—O14ix	155.8 (6)
C2—C3—C6	109.51 (17)	O12iv—Rb20—O14ix	84.7 (6)
C4—C3—C6	109.52 (17)	O11i—Rb20—O25viii	72.9 (7)
C2—C3—O17	109.43 (17)	O12iv—Rb20—O25viii	107.0 (8)
C4—C3—O17	109.41 (17)	O14ix—Rb20—O25viii	131.2 (7)
C6—C3—O17	109.47 (17)	K19i—Rb20—O25viii	65.7 (7)
C3—C4—C5	115.04 (18)	K21ix—Rb20—O25viii	122.7 (6)
C4—C5—O13	115.1 (5)	K21xi—Rb20—O25viii	46.7 (6)
C4—C5—O14	115.1 (5)	K23ix—Rb20—O25viii	136.0 (7)
O13—C5—O14	129.4 (4)	O12vii—Rb24—O13v	147.2 (5)
C3—C6—O15	115.3 (5)	O12vii—Rb24—O14	81.4 (6)
C3—C6—O16	114.9 (5)	O13v—Rb24—O14	103.4 (5)

Symmetry codes: (i) −x, −y+1, −z; (ii) −x+3/2, y+1/2, −z+1/2; (iii) x+1, y, z; (iv) x−1, y, z; (v) −x+1, −y, −z; (vi) −x+1/2, y−1/2, −z+1/2; (vii) −x+3/2, y−1/2, −z+1/2; (viii) x+1/2, −y+3/2, z+1/2; (ix) −x+1/2, y+1/2, −z+1/2; (x) x+3/2, −y+3/2, z+3/2; (xi) x−1/2, −y+3/2, z+1/2.

(II_19_DFT). Crystal data

C6H7KO8Rb2	b = 11.846841 Å
Mr = 417.10	c = 13.227547 Å
Monoclinic, P21/n	β = 98.1091°
Hall symbol: -P 2yn	V = 1140.37 Å3
a = 7.350692 Å	Z = 4

(II_19_DFT). Data collection

h = →	l = →
k = →

(II_19_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.379147	0.393481	0.127092	0.03533*
C2	0.297157	0.284667	0.161900	0.02188*
C3	0.408299	0.176847	0.153108	0.02188*
C4	0.288255	0.078471	0.182726	0.02188*
C5	0.337989	−0.036751	0.142957	0.03533*
C6	0.597428	0.175190	0.221702	0.03533*
H7	0.274230	0.294909	0.241047	0.02844*
H8	0.163702	0.272328	0.115834	0.02844*
H9	0.299322	0.075476	0.265689	0.02844*
H10	0.146079	0.097106	0.152122	0.02844*
O11	0.275146	0.455071	0.065511	0.03533*
O12	0.542964	0.417971	0.163384	0.03533*
O13	0.230948	−0.074562	0.066665	0.03533*
O14	0.476999	−0.086921	0.187735	0.03533*
O15	0.599178	0.183712	0.317526	0.03533*
O16	0.736783	0.160796	0.178156	0.03533*
O17	0.439851	0.165051	0.048570	0.03533*
H18	0.571275	0.148706	0.051908	0.04593*
K19	−0.115873	0.442248	0.109784	0.02929*
Rb20	0.997078	0.165805	0.384557	0.02929*
Rb21	0.835191	−0.069923	0.115567	0.02929*
O25	0.393473	0.216240	0.468716	0.12179*
H26	0.342581	0.293118	0.460336	0.15833*
H27	0.461303	0.202302	0.411083	0.58330*

(II_19_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O16	0.98	1.93	2.579	122
O17—H18···O13i	0.98	2.45	3.220	136
O25—H26···O13ii	0.99	1.68	2.660	173
O25—H27···O15	0.98	1.72	2.700	174

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1/2, y+1/2, −z+1/2.

(II_20_DFT). Crystal data

C6H7KO8Rb2	b = 11.846841 Å
Mr = 417.10	c = 13.227549 Å
Monoclinic, P21/n	β = 98.1091°
Hall symbol: -P 2yn	V = 1140.37 Å3
a = 7.350692 Å	Z = 4

(II_20_DFT). Data collection

h = →	l = →
k = →

(II_20_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.384218	0.392861	0.126973	0.03533*
C2	0.305212	0.282429	0.160374	0.02188*
C3	0.419109	0.170061	0.149253	0.02188*
C4	0.298983	0.076671	0.177466	0.02188*
C5	0.342101	−0.038417	0.135603	0.03533*
C6	0.608783	0.176423	0.217478	0.03533*
H7	0.280007	0.289357	0.239365	0.02844*
H8	0.173856	0.268336	0.112922	0.02844*
H9	0.309871	0.072365	0.260330	0.02844*
H10	0.156529	0.096601	0.148599	0.02844*
O11	0.294864	0.443191	0.051752	0.03533*
O12	0.531397	0.429050	0.177561	0.03533*
O13	0.227200	−0.075640	0.061912	0.03533*
O14	0.481315	−0.091449	0.176152	0.03533*
O15	0.610259	0.180902	0.313492	0.03533*
O16	0.749135	0.169196	0.173663	0.03533*
O17	0.448775	0.168279	0.044235	0.03533*
H18	0.579224	0.151337	0.044285	0.04593*
Rb19	−0.113845	0.425126	0.111367	0.02929*
K20	0.978236	0.156277	0.385143	0.02929*
Rb21	0.839459	−0.073164	0.110994	0.02929*
O25	0.343562	0.206112	0.429428	0.12179*
H26	0.316358	0.287413	0.435388	0.15833*
H27	0.438648	0.197642	0.384416	0.5833*

(II_20_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O16	0.98	1.98	2.596	118
O25—H26···O13i	0.99	1.66	2.648	177
O25—H27···O15	0.99	1.69	2.671	177

Symmetry code: (i) −x+1/2, y+1/2, −z+1/2.

(II_21_DFT). Crystal data

C6H7KO8Rb2	b = 11.846841 Å
Mr = 417.10	c = 13.227549 Å
Monoclinic, P21/n	β = 98.1091°
Hall symbol: -P 2yn	V = 1140.37 Å3
a = 7.350692 Å	Z = 4

(II_21_DFT). Data collection

h = →	l = →
k = →

(II_21_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.384640	0.395404	0.135647	0.03533*
C2	0.297849	0.285289	0.163395	0.02188*
C3	0.407572	0.177871	0.151465	0.02188*
C4	0.288381	0.079456	0.181825	0.02188*
C5	0.330118	−0.032430	0.134234	0.03533*
C6	0.599433	0.176950	0.217300	0.03533*
H7	0.271618	0.290599	0.242332	0.02844*
H8	0.167350	0.274630	0.114157	0.02844*
H9	0.307767	0.072515	0.264723	0.02844*
H10	0.144764	0.100005	0.156692	0.02844*
O11	0.298137	0.452327	0.063566	0.03533*
O12	0.534747	0.425208	0.187730	0.03533*
O13	0.213385	−0.065891	0.060067	0.03533*
O14	0.473694	−0.085091	0.170046	0.03533*
O15	0.605990	0.187134	0.313101	0.03533*
O16	0.736153	0.162119	0.171402	0.03533*
O17	0.433433	0.166966	0.045915	0.03533*
H18	0.563251	0.147163	0.047130	0.04593*
Rb19	−0.115589	0.436888	0.115484	0.02929*
Rb20	0.997021	0.166511	0.381875	0.02929*
K21	0.826737	−0.066349	0.111425	0.02929*
O25	0.389886	0.220556	0.456407	0.12179*
H26	0.349411	0.300046	0.455368	0.15833*
H27	0.463621	0.210092	0.400608	0.15833*

(II_21_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O16	0.98	1.94	2.582	121
O25—H26···O13i	0.99	1.66	2.642	173
O25—H27···O15	0.98	1.69	2.669	175

Symmetry code: (i) −x+1/2, y+1/2, −z+1/2.