Sodium dirubidium citrate, NaRb₂C₆H₅O₇, and sodium dirubidium citrate dihydrate, NaRb₂C₆H₅O₇(H₂O)₂

The crystal structures of sodium dirubidium citrate and sodium dirubidium citrate dihydrate have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. Both structures contain Na chains and Rb layers, which link to form different three-dimensional frameworks.

Abstract

The crystal structures of sodium dirubidium citrate {poly[μ-citrato-dirubi­dium(I)sodium(I)], [NaRb₂(C₆H₅O₇)]_n} and sodium dirubidium citrate dihydrate {poly[di­aqua­(μ-citrato)dirubidium(I)sodium(I)], [NaRb₂(C₆H₅O₇)(H₂O)₂]_n} have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. Both structures contain Na chains and Rb layers, which link to form different three-dimensional frameworks. In each structure, the citrate triply chelates to the Na⁺ cation. Each citrate also chelates to Rb⁺ cations. In the dihydrate structure, the water mol­ecules are bonded to the Rb⁺ cations; the Na⁺ cation is coordinated only to citrate O atoms. Both structures contain an intra­molecular O—H⋯O hydrogen bond between the hy­droxy group and one of the terminal carboxyl­ate groups. In the structure of the dihydrate, each hydrogen atom of the water mol­ecules participates in a hydrogen bond to an ionized carboxyl­ate group.

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 ▸), and to sodium metal hydrogen citrates in Cigler & Kaduk (2019 ▸). These two compounds (Figs. 1 ▸ and 2 ▸) are a further extension to sodium dirubidium citrates.

Figure 1.

The asymmetric unit of NaRb₂C₆H₅O₇, with the atom numbering and 50% probability spheroids.

Figure 2.

The asymmetric unit of NaRb₂HC₆H₅O₇(H₂O)₂, with the atom numbering and 50% probability spheroids.

Structural commentary  

For NaRb₂C₆H₅O₇, the root-mean-square deviation of the non-hydrogen atoms in the refined and optimized structures is 0.095 Å (Fig. 3 ▸). The excellent agreement between the structures is strong evidence that the experimental structure is correct (van de Streek & Neumann, 2014 ▸). For NaRb₂C₆H₅O₇(H₂O)₂, the agreement of the refined and optimized structures is poorer (Fig. 4 ▸); the r.m.s. cartesian displacement is 0.45 Å. The largest differences are in the carboxyl group C5/O13/O14. Removing O13 and O14 from the displacement calculation yields a value of 0.222 Å, in the upper range of correct structures according to van de Streek & Neumann (2014 ▸). Apparently the refined structure is in error, perhaps because it was refined using laboratory X-ray powder data and the structure contains two heavy Rb atoms. This discussion uses the DFT-optimized structures.

Figure 3.

Comparison of the refined and optimized structures of sodium dirubidium citrate. The refined structure is in red, and the DFT-optimized structure is in blue.

Figure 4.

Comparison of the refined and optimized structures of sodium dirubidium citrate dihydrate. The refined structure is in red, and the DFT-optimized structure is in blue.

In both structures, all of the citrate bond lengths, bond angles, and torsion angles fall within the normal ranges indicated by a Mercury Mogul Geometry Check (Macrae et al., 2008 ▸). The citrate anion in both structures 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 (Rammohan & Kaduk, 2018 ▸). The central carboxyl­ate group and the hy­droxy group exhibit small twists (O15—C6—C3—O17 torsion angles of −16.0 and −18.2°) from the normal planar arrangement.

In NaRb₂C₆H₅O₇, the citrate anion triply chelates to Na19 through the terminal carboxyl­ate O14, the central carboxyl­ate O15, and the hydroxyl group O17. The citrate also chelates to Rb21 through the terminal carboxyl­ate O11 and the central carboxyl­ate O15. Each citrate oxygen atom bridges multiple metal atoms. The Na⁺ cation is six-coordinate, with a bond-valence sum of 1.12. The two Rb⁺ cations are seven-coordinate, with bond-valence sums of 0.99 and 1.16.

In the dihydrate, the citrate anion similarly triply chelates to Na19 through the terminal carboxyl­ate O12, the central carboxyl­ate O15, and the hy­droxy group O17 (the numberings of the oxygen atoms are partially arbitrary). Each terminal carboxyl­ate group chelates to a different Rb21 cation. Most of the oxygen atoms bridge multiple metal atoms, but O13 and O14 bind only to Rb cations, and O17 binds only to the Na⁺ cation. The Na coordination sphere is composed only of citrate oxygen atoms. Rb20 is coordinated by four H₂O, and Rb21 is bonded to two H₂O mol­ecules. Each water mol­ecule is coordinated to two Rb20 and and one Rb21 cations. The Na⁺ cation is six-coordinate (distorted octa­hedral), with a bond-valence sum of 1.19. The Rb20 and Rb21 cations are eight- and nine-coordinate, respectively. The coordination polyhedra are irregular, and the bond-valence sums are 0.94 and 1.03. The Mulliken overlap populations in both structures indicate that the Rb—O bonds are ionic, but that the Na—O bonds have some covalent character.

Supra­molecular features  

In the crystal structure of NaRb₂C₆H₅O₇ (Fig. 5 ▸), the distorted octa­hedral NaO6 coordination polyhedra share edges to form zigzag double chains along the a-axis direction. The RbO₇ polyhedra share edges to form layers parallel to the ac plane. These layers link the Na chains, forming a three-dimensional framework. The hydro­phobic methyl­ene groups of the citrate anions occupy cavities in this framework.

Figure 5.

Crystal structure of NaRb₂C₆H₅O₇, viewed down the a axis.

In the crystal structure of NaRb₂C₆H₅O₇(H₂O)₂ (Fig. 6 ▸), the NaO₆ coordination polyhedra share corners to form double zigzag chains along the c-axis direction. The Rb polyhedra share edges to form layers parallel to the ac plane. These layers share corners with each other and share edges with the Na chains, forming a three-dimensional framework. The hydro­phobic methyl­ene groups of the citrate anions also occupy cavities in this framework.

Figure 6.

Crystal structure of NaRb₂C₆H₅O₇(H₂O)₂, viewed down the a axis.

In NaRb₂C₆H₅O₇, the only traditional hydrogen bond is an intra­molecular O17—H18⋯O11 one between the hydroxyl group and one of the terminal carboxyl­ate groups (Table 1 ▸). By the correlation of Rammohan & Kaduk (2018 ▸), this hydrogen bond contributes 14.0 kcal mol⁻¹ to the crystal energy. A weak C—H⋯O hydrogen bond also contributes to the crystal energy.

Table 1. Hydrogen-bond geometry (Å, °, electrons, kcal mol⁻¹) for [NaRb₂(C₆H₅O₇)].

D—H⋯A′	D—H	H⋯A	D⋯A	D—H⋯A	Mulliken overlap	H-bond energy
O17—H18⋯O11	0.996	1.662	2.585	152.3	0.072	14.7
C4—H10⋯O17i	1.088	2.451	3.515	165.5	0.017

Symmetry code: (i) 1 + x, y, z.

In NaRb₂C₆H₅O₇(H₂O)₂, each water mol­ecule hydrogen atom acts as a donor in an O—H⋯O hydrogen bond to a carboxyl­ate oxygen (Table 2 ▸). By the correlation of Rammohan & Kaduk (2018 ▸), these hydrogen bonds range from 11.0–14.0 kcal mol⁻¹ in energy. There is an intra­molecular O17—H18⋯O13 hydrogen bond between the hydroxyl group and one of the terminal carboxyl­ate groups, as well as a C—H⋯O hydrogen bond.

Table 2. Hydrogen-bond geometry (Å, °, electrons, kcal mol⁻¹) for [NaRb₂(C₆H₅O₇)(H₂O)₂].

D—H⋯A′	D—H	H⋯A	D⋯A	D—H⋯A	Mulliken overlap	H-bond energy
O23—H27⋯O15	0.986	1.755	2.721	165.6	0.064	13.8
O23—H26⋯O14i	0.974	1.934	2.833	152.2	0.041	11.1
O22—H25⋯O14ii	0.979	1.762	2.708	161.4	0.055	12.8
O22—H24⋯O13	0.980	1.779	2.718	159.0	0.053	12.6
O17—H18⋯O13	0.987	1.705	2.613	151.0	0.066	14.0
C4—H9⋯O13ii	1.096	2.402	3.374	147.0	0.016

Symmetry code: (i) − + x,  − y, z; (ii) x, y, −1 + z; (iii) 1 − x, 1 − y,  + z.

The two structures exhibit some similarities (Fig. 7 ▸), but a mechanism for inter­conversion of the structures is not obvious by visual inspection.

Figure 7.

Comparison of the crystal structures of sodium dirubidium citrate (left) and sodium dirbuidium citrate dihydrate (right).

Database survey  

Details of the comprehensive literature search for citrate structures are presented in Rammohan & Kaduk (2018 ▸). A reduced cell search for NaRb₂HC₆H₅O₇ in the Cambridge Structural Database (Groom et al., 2016 ▸) yielded no hits, while that for NaRb₂C₆H₅O₇(H₂O)₂ yielded 21 hits, but when including the chemistry of C, H, Na, O, and Rb only it yielded no hits.

Synthesis and crystallization  

NaRb₂C₆H₅O₇(H₂O)₂ was prepared by adding stoichiometric qu­anti­ties of Na₂CO₃ and Rb₂CO₃ to a solution of 10 mmol H₃C₆H₅O₇ in 10 ml of water. After the fizzing subsided, the clear solution was dried overnight at 348 K to yield a glass. This glass was heated at 450 K for 30 min to yield a pale-yellow solid. This solid was equilibrated in air at ambient conditions for 3 h. The anhydrous salt was prepared by heating the dihydrate at 450 K for 30 min.

Refinement  

Crystal data, data collection and structure refinement (Fig. 8 ▸) details are summarized in Table 3 ▸. The diffraction patterns of both compounds were indexed using N-TREOR (Altomare et al., 2013 ▸), and the cells were reduced using the tools in the PDF-4+ database (Fawcett et al., 2017 ▸). The systematic absences in the the pattern of NaRb₂C₆H₅O₇(H₂O)₂ suggested the space groups Pna2₁ and Pnam. The unit-cell volume indicates that Z = 4, so Pna2₁ was chosen, and confirmed by successful solution and refinement of the structure.

Figure 8.

Rietveld plot for NaRb₂C₆H₅O₇. The red crosses represent the observed data points, and the green line is the calculated pattern. The magenta curve is the difference pattern, plotted at the same scale as the other patterns. The vertical scale has been multiplied by a factor of 8 for 2θ > 44.0°. The row of black tick marks indicates the reflection positions for this phase.

Table 3. Experimental details.

	[NaRb2(C6H5O7)]	[NaRb2(C6H5O7)(H2O)2]
Crystal data
M r	383.02	419.05
Crystal system, space group	Triclinic, P	Orthorhombic, P n a21
Temperature (K)	300	300
a, b, c (Å)	5.5917 (4), 7.8862 (5), 11.6133 (6)	12.1101 (3), 17.2422 (5), 5.73715 (18)
α, β, γ (°)	83.456 (4), 89.243 (5), 84.488 (4)	90, 90, 90
V (Å3)	506.42 (8)	1197.94 (8)
Z	2	4
Radiation type	Cu Kα1, Cu Kα2, λ = 1.540593, 1.544451 Å	Kα1, Kα2, λ = 1.540593, 1.544451 Å
Specimen shape, size (mm)	Flat sheet, 25 × 25	Flat sheet, 25 × 25
Data collection
Diffractometer	Bruker D2 Phaser	Bruker D2 Phaser
Specimen mounting	Standard PMMA holder	Standard PMMA holder
Data collection mode	Reflection	Reflection
Scan method	Step	Step
2θ values (°)	2θmin = 5.001 2θmax = 100.007 2θstep = 0.020	2θmin = 5.001 2θmax = 100.007 2θstep = 0.020
Refinement
R factors and goodness of fit	R p = 0.023, R wp = 0.029, R exp = 0.022, R(F 2) = 0.06119, χ2 = 1.742	R p = 0.035, R wp = 0.047, R exp = 0.023, R(F 2) = 0.21645, χ2 = 4.494
No. of parameters	75	67
No. of restraints	29	29
H-atom treatment	Only H-atom displacement parameters refined	Only H-atom displacement parameters refined

The same symmetry and lattice parameters were used for the DFT calculations as for each powder diffraction study. Computer programs: Diffrac.Measurement (Bruker, 2009 ▸), PowDLL (Kourkoumelis, 2013 ▸), EXPO2014 (Altomare et al.), 2013 ▸), GSAS (Larson & Von Dreele, 2004 ▸), Mercury (Macrae et al., 2008 ▸), DIAMOND (Crystal Impact, 2015 ▸) and publCIF (Westrip, 2010 ▸).

The structure of NaRb₂HC₆H₅O₇ was solved using Monte Carlo simulated annealing techniques as implemented in EXPO2014 (Altomare et al., 2013 ▸). A citrate anion, a Na cation, and two Rb cations were used as fragments. The position of the active hydrogen atom H18 was deduced from the potential intra­molecular hydrogen-bonding pattern. Pseudovoigt profile coefficients were as parameterized in Thompson et al. (1987 ▸) and the asymmetry correction of Finger et al. (1994 ▸) was applied and microstrain broadening by Stephens (1999 ▸). The hydrogen atoms were included in fixed positions, which were re-calculated during the course of the refinement. The U _iso values of C2, C3, and C4 were constrained to be equal, and those of H7, H8, H9, and H10 were constrained to be 1.3 times that of these carbon atoms. The U _iso values of C1, C5, C6, and the oxygen atoms were constrained to be equal, and that of H18 was constrained to be 1.3 times this value. The U _iso values of Rb20 and Rb21 were constrained to be equal.

The structure of NaRb₂C₆H₅O₇(H₂O)₂ was solved using Monte Carlo simulated annealing techniques as implemented in EXPO2014 (Altomare et al., 2013 ▸). A citrate anion, a Na cation, two Rb cations, and three O atoms were used as fragments. In the best solution, one of the oxygen atoms was 1.30 Å from one of the Rb atoms, and was removed from the model. The positions of the active hydrogen atoms were deduced from potential hydrogen-bonding patterns. The same refinement strategy was used as for the anhydrous compound, and the U _iso values of the two water mol­ecule oxygen atoms were constrained to be equal. Comparison of the initial refined model to that from the DFT calculation revealed that the orientations of the carboxyl group C5/O13/O14 differed, so the Rietveld refinement (Fig. 9 ▸) was re-started from the DFT model.

Figure 9.

Rietveld plot for NaRb₂C₆H₅O₇(H₂O)₂. The red crosses represent the observed data points, and the green line is the calculated pattern. The magenta curve is the difference pattern, plotted at the same scale as the other patterns. The vertical scale has been multiplied by a factor of 10 for 2θ > 44.0°. The row of black tick marks indicates the reflection positions for this phase.

Density functional geometry optimizations (fixed experimental unit cells) were carried out using CRYSTAL14 (Dovesi et al., 2014 ▸). The basis sets for the H, C, and O atoms were those of Gatti et al. (1994 ▸), the basis sets for Na was that of Dovesi et al. (1991 ▸), and the basis set for Rb was that of Sophia et al. (2014 ▸). The calculations were run on eight 2.1 GHz Xeon cores (each with 6 GB RAM) of a 304-core Dell Linux cluster at Illinois Institute of Technology, using 8 k-points and the B3LYP functional, and took approximately 5 and 29 h.

Supplementary Material

CCDC references: 1901423, 1901422, 1901421, 1901420

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

supplementary crystallographic information

Poly[µ-citrato-dirubidium(I)sodium(I)] (KADU1685_publ). Crystal data

[NaRb2(C6H5O7)]	γ = 84.488 (4)°
Mr = 383.02	V = 506.42 (8) Å3
Triclinic, P1	Z = 2
Hall symbol: -P 1	Dx = 2.512 Mg m−3
a = 5.5917 (4) Å	CuKα1, CuKα2 radiation, λ = 1.540593, 1.544451 Å
b = 7.8862 (5) Å	T = 300 K
c = 11.6133 (6) Å	pale yellow
α = 83.456 (4)°	flat_sheet, 25 × 25 mm
β = 89.243 (5)°	Specimen preparation: Prepared at 450 K

Poly[µ-citrato-dirubidium(I)sodium(I)] (KADU1685_publ). Data collection

Bruker D2 Phaser diffractometer	Data collection mode: reflection
Radiation source: sealed Xray tube	Scan method: step
Ni filter monochromator	2θmin = 5.001°, 2θmax = 100.007°, 2θstep = 0.020°
Specimen mounting: standard PMMA holder

Poly[µ-citrato-dirubidium(I)sodium(I)] (KADU1685_publ). Refinement

Least-squares matrix: full	Profile function: CW Profile function number 4 with 27 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 0.000 #2(GV) = 0.000 #3(GW) = 5.109 #4(GP) = 0.000 #5(LX) = 6.277 #6(ptec) = 0.00 #7(trns) = 1.30 #8(shft) = -2.9593 #9(sfec) = 0.00 #10(S/L) = 0.0005 #11(H/L) = 0.0097 #12(eta) = 0.9000 Peak tails are ignored where the intensity is below 0.0100 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rp = 0.023	75 parameters
Rwp = 0.029	29 restraints
Rexp = 0.022	Only H-atom displacement parameters refined
R(F2) = 0.06119	Weighting scheme based on measured s.u.'s
4701 data points	(Δ/σ)max = 0.01
Excluded region(s): The region from 5-15 degrees was excluded to minimize the effects of beam spillover and surface roughness.	Background function: GSAS Background function number 1 with 3 terms. Shifted Chebyshev function of 1st kind 1: 1719.95 2: -345.196 3: 91.9837

Poly[µ-citrato-dirubidium(I)sodium(I)] (KADU1685_publ). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.124 (2)	−0.2349 (14)	0.1360 (11)	0.010 (3)*
C2	0.250 (3)	−0.0724 (15)	0.1222 (10)	0.023 (7)*
C3	0.1816 (19)	0.0398 (11)	0.2201 (7)	0.023 (7)*
C4	0.319 (3)	0.2010 (14)	0.2001 (10)	0.023 (7)*
C5	0.286 (2)	0.3027 (17)	0.3028 (11)	0.010 (3)*
C6	0.251 (2)	−0.0599 (17)	0.3397 (9)	0.010 (3)*
H7	0.20437	−0.00565	0.04596	0.030 (9)*
H8	0.42788	−0.10242	0.12401	0.030 (9)*
H9	0.25594	0.27385	0.12877	0.030 (9)*
H10	0.49370	0.16615	0.18985	0.030 (9)*
O11	−0.099 (2)	−0.227 (2)	0.1578 (14)	0.010 (3)*
O12	0.225 (3)	−0.3679 (14)	0.0961 (14)	0.010 (3)*
O13	0.465 (3)	0.366 (2)	0.3415 (15)	0.010 (3)*
O14	0.075 (3)	0.351 (2)	0.3358 (13)	0.010 (3)*
O15	0.088 (3)	−0.118 (2)	0.4057 (11)	0.010 (3)*
O16	0.457 (3)	−0.051 (2)	0.3819 (13)	0.010 (3)*
O17	−0.070 (2)	0.0903 (16)	0.2172 (12)	0.010 (3)*
H18	−0.12093	−0.00352	0.20357	0.013 (4)*
Na19	−0.247 (3)	0.1397 (17)	0.4081 (11)	0.010 (5)*
Rb20	0.7394 (9)	0.4509 (7)	0.1312 (3)	0.0224 (13)*
Rb21	−0.2414 (10)	−0.3662 (5)	0.4096 (3)	0.0224 (13)*

Poly[µ-citrato-dirubidium(I)sodium(I)] (KADU1685_publ). Geometric parameters (Å, º)

C1—C2	1.5108 (13)	O14—Rb21vi	3.130 (17)
C1—O11	1.269 (4)	O15—C6	1.269 (4)
C1—O12	1.273 (4)	O15—Na19	2.63 (2)
C2—C1	1.5108 (13)	O15—Na19vi	2.33 (2)
C2—C3	1.5411 (13)	O15—Rb21	2.810 (17)
C3—C2	1.5411 (13)	O16—C6	1.270 (4)
C3—C4	1.5405 (13)	O16—Na19iv	2.38 (2)
C3—C6	1.5507 (13)	O16—Na19vi	2.74 (2)
C3—O17	1.423 (4)	O16—Rb21iv	2.858 (16)
C4—C3	1.5405 (13)	O17—C3	1.423 (4)
C4—C5	1.5100 (13)	O17—Na19	2.473 (18)
C5—C4	1.5100 (13)	O17—Rb20vii	3.003 (13)
C5—O13	1.270 (4)	Na19—O13vii	2.35 (2)
C5—O14	1.269 (4)	Na19—O14	2.637 (19)
C6—C3	1.5507 (13)	Na19—O15	2.63 (2)
C6—O15	1.269 (4)	Na19—O15vi	2.33 (2)
C6—O16	1.270 (4)	Na19—O16vii	2.38 (2)
O11—C1	1.269 (4)	Na19—O16vi	2.74 (2)
O11—Rb20i	2.823 (13)	Na19—O17	2.473 (18)
O11—Rb21	3.124 (16)	Rb20—O11v	2.823 (13)
O12—C1	1.273 (4)	Rb20—O12viii	3.098 (16)
O12—Rb20i	3.187 (16)	Rb20—O12v	3.187 (16)
O12—Rb20ii	3.098 (16)	Rb20—O12iii	2.791 (15)
O12—Rb20iii	2.791 (15)	Rb20—O13	2.914 (19)
O13—C5	1.270 (4)	Rb20—O14iv	3.034 (19)
O13—Na19iv	2.35 (2)	Rb20—O17iv	3.003 (13)
O13—Rb20	2.914 (19)	Rb21—O11	3.124 (16)
O13—Rb21v	2.978 (12)	Rb21—O13i	2.978 (12)
O13—Rb21vi	3.135 (19)	Rb21—O13vi	3.135 (19)
O14—C5	1.269 (4)	Rb21—O14ii	2.912 (14)
O14—Na19	2.637 (19)	Rb21—O14vi	3.130 (17)
O14—Rb20vii	3.034 (19)	Rb21—O15	2.810 (17)
O14—Rb21viii	2.912 (14)	Rb21—O16vii	2.858 (16)
C2—C1—O11	119.8 (5)	O13vii—Na19—O14	85.8 (5)
C2—C1—O12	119.0 (4)	O13vii—Na19—O15	160.3 (8)
O11—C1—O12	118.7 (3)	O13vii—Na19—O15vi	121.1 (8)
O11—C1—Rb20i	51.1 (6)	O13vii—Na19—O16vii	87.2 (8)
O12—C1—Rb20i	67.9 (5)	O13vii—Na19—O16vi	97.3 (8)
C1—C2—C3	111.6 (4)	O13vii—Na19—O17	97.2 (7)
C2—C3—C4	108.2 (3)	O14—Na19—O15	89.0 (8)
C2—C3—C6	110.4 (4)	O14—Na19—O15vi	89.2 (7)
C2—C3—O17	109.9 (4)	O14—Na19—O16vii	154.3 (7)
C4—C3—C6	109.6 (3)	O14—Na19—O16vi	134.2 (7)
C4—C3—O17	109.1 (4)	O14—Na19—O17	66.1 (6)
C6—C3—O17	109.7 (3)	O15—Na19—O15vi	77.7 (8)
C3—C4—C5	110.2 (4)	O15—Na19—O16vii	89.3 (6)
C4—C5—O13	119.4 (4)	O15—Na19—O16vi	99.9 (6)
C4—C5—O14	119.7 (3)	O15—Na19—O17	63.5 (5)
O13—C5—O14	119.6 (5)	O15vi—Na19—O16vii	115.4 (7)
O13—C5—Rb20	56.5 (8)	O15vi—Na19—O16vi	50.3 (3)
O13—C5—Rb21vi	65.7 (8)	O15vi—Na19—O17	133.2 (9)
O14—C5—Rb20	140.2 (13)	O16vii—Na19—O16vi	71.3 (7)
O14—C5—Rb21vi	65.4 (8)	O16vii—Na19—O17	90.3 (7)
C1—O11—Rb20i	108.4 (7)	O16vi—Na19—O17	155.9 (7)
C1—O11—Rb21	116.0 (11)	O11v—Rb20—O12viii	88.4 (4)
Rb20i—O11—Rb21	76.6 (4)	O11v—Rb20—O12v	42.1 (2)
C1—O12—Rb20i	90.4 (5)	O11v—Rb20—O12iii	113.3 (4)
C1—O12—Rb20ii	130.7 (9)	O11v—Rb20—O13	104.5 (4)
C1—O12—Rb20iii	130.3 (12)	O11v—Rb20—O14iv	79.8 (5)
Rb20i—O12—Rb20ii	125.7 (4)	O11v—Rb20—O17iv	132.4 (4)
Rb20i—O12—Rb20iii	90.3 (4)	O12viii—Rb20—O12v	125.7 (4)
Rb20ii—O12—Rb20iii	86.5 (4)	O12viii—Rb20—O12iii	93.5 (4)
C5—O13—Na19iv	108.6 (13)	O12viii—Rb20—O13	72.1 (5)
C5—O13—Rb20	102.2 (10)	O12viii—Rb20—O14iv	135.5 (4)
C5—O13—Rb21v	158.1 (13)	O12viii—Rb20—O17iv	133.1 (4)
C5—O13—Rb21vi	92.7 (9)	O12v—Rb20—O12iii	89.7 (4)
Na19iv—O13—Rb20	92.1 (7)	O12v—Rb20—O13	130.1 (4)
Na19iv—O13—Rb21v	93.3 (5)	O12v—Rb20—O14iv	68.4 (5)
Na19iv—O13—Rb21vi	90.8 (7)	O12v—Rb20—O17iv	101.1 (4)
Rb20—O13—Rb21v	77.6 (4)	O12iii—Rb20—O13	139.1 (4)
Rb20—O13—Rb21vi	163.0 (4)	O12iii—Rb20—O14iv	130.6 (5)
Rb21v—O13—Rb21vi	85.5 (4)	O12iii—Rb20—O17iv	89.5 (4)
C5—O14—Na19	123.9 (14)	O13—Rb20—O14iv	69.8 (3)
C5—O14—Rb20vii	111.3 (9)	O13—Rb20—O17iv	75.4 (5)
C5—O14—Rb21viii	145.9 (12)	O14iv—Rb20—O17iv	55.0 (4)
C5—O14—Rb21vi	92.9 (8)	O11—Rb21—O13i	96.0 (5)
Na19—O14—Rb20vii	84.2 (5)	O11—Rb21—O13vi	158.9 (5)
Na19—O14—Rb21viii	89.2 (5)	O11—Rb21—O14ii	77.0 (5)
Na19—O14—Rb21vi	91.2 (6)	O11—Rb21—O14vi	138.7 (4)
Rb20vii—O14—Rb21viii	76.8 (4)	O11—Rb21—O15	67.5 (3)
Rb20vii—O14—Rb21vi	153.5 (5)	O11—Rb21—O16vii	80.2 (5)
Rb21viii—O14—Rb21vi	77.1 (3)	O13i—Rb21—O13vi	94.5 (4)
C6—O15—Na19	105.0 (9)	O13i—Rb21—O14ii	70.6 (3)
C6—O15—Na19vi	104.8 (10)	O13i—Rb21—O14vi	123.3 (6)
C6—O15—Rb21	138.4 (12)	O13i—Rb21—O15	162.7 (5)
Na19—O15—Na19vi	102.3 (8)	O13i—Rb21—O16vii	106.4 (5)
Na19—O15—Rb21	94.2 (6)	O13vi—Rb21—O14ii	123.9 (6)
Na19vi—O15—Rb21	106.6 (5)	O13vi—Rb21—O14vi	41.01 (19)
C6—O16—Na19iv	143.9 (11)	O13vi—Rb21—O15	102.7 (3)
C6—O16—Na19vi	85.3 (8)	O13vi—Rb21—O16vii	79.4 (5)
C6—O16—Rb21iv	115.0 (12)	O14ii—Rb21—O14vi	102.9 (3)
Na19iv—O16—Na19vi	108.7 (7)	O14ii—Rb21—O15	99.4 (5)
Na19iv—O16—Rb21iv	98.5 (6)	O14ii—Rb21—O16vii	156.4 (4)
Na19vi—O16—Rb21iv	89.6 (5)	O14vi—Rb21—O15	71.9 (4)
C3—O17—Na19	114.2 (7)	O14vi—Rb21—O16vii	98.0 (4)
C3—O17—Rb20vii	121.1 (6)	O15—Rb21—O16vii	76.9 (3)
Na19—O17—Rb20vii	87.7 (5)

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

(kadu1685_DFT). Crystal data

C6H5NaO7Rb2	α = 83.4560°
Mr = 383.02	β = 89.2430°
Triclinic, P1	γ = 84.4880°
a = 5.5917 Å	V = 506.42 Å3
b = 7.8862 Å	Z = 2
c = 11.6133 Å

(kadu1685_DFT). Data collection

h = →	l = →
k = →

(kadu1685_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.12954	−0.24091	0.13258	0.01020*
C2	0.26324	−0.07916	0.13201	0.02320*
C3	0.17418	0.04028	0.22411	0.02320*
C4	0.29971	0.20638	0.20696	0.02320*
C5	0.27264	0.31378	0.31043	0.01020*
C6	0.24131	−0.05121	0.34701	0.01020*
H7	0.23583	−0.00707	0.04568	0.03000*
H8	0.45556	−0.11740	0.14158	0.03000*
H9	0.22830	0.28512	0.12888	0.03000*
H10	0.48942	0.17037	0.19211	0.03000*
O11	−0.09135	−0.22959	0.16288	0.01020*
O12	0.24168	−0.37299	0.09935	0.01020*
O13	0.46259	0.36227	0.34992	0.01020*
O14	0.06361	0.34542	0.35028	0.01020*
O15	0.07766	−0.11340	0.40960	0.01020*
O16	0.45856	−0.05647	0.37654	0.01020*
O17	−0.07963	0.08108	0.21210	0.01020*
H18	−0.13612	−0.03134	0.19953	0.01300*
Na19	−0.23798	0.12272	0.40262	0.01000*
Rb20	0.74402	0.44949	0.13375	0.02240*
Rb21	−0.24917	−0.36450	0.40909	0.02240*

(kadu1685_DFT). Bond lengths (Å)

C1—C2	1.539	O14—Na19	2.568
C1—O11	1.277	O14—Rb20vii	3.091
C1—O12	1.260	O14—Rb21v	3.018
C2—C3	1.551	O14—Rb21viii	2.884
C2—H7	1.100	O15—Na19v	2.359
C2—H8	1.092	O15—Rb21	2.821
C3—C4	1.537	O16—Na19iv	2.354
C3—C6	1.558	O16—Rb21iv	2.785
C3—O17	1.430	O17—H18	0.996
C4—C5	1.545	O17—Na19	2.418
C4—H9	1.096	O17—Rb20vii	3.019
C4—H10	1.088	Na19—O15v	2.359
C5—O13	1.271	Na19—O13vii	2.429
C5—O14	1.264	Na19—O16vii	2.354
C6—O15	1.262	Rb20—O12viii	3.026
C6—O16	1.262	Rb20—O14iv	3.091
O11—Rb20i	2.832	Rb20—O17iv	3.019
O11—Rb21	3.083	Rb20—O11vi	2.832
O12—Rb20ii	3.026	Rb20—O12vi	3.233
O12—Rb20i	3.233	Rb20—O12iii	2.838
O12—Rb20iii	2.838	Rb21—O16vii	2.785
O13—Na19iv	2.429	Rb21—O13v	3.029
O13—Rb20	2.994	Rb21—O14v	3.018
O13—Rb21v	3.029	Rb21—O13i	2.957
O13—Rb21vi	2.957	Rb21—O14ii	2.884

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

(kadu1685_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O17—H18···O11	0.996	1.662	2.585	152.3
C4—H10···O17	1.088	2.451	3.515	165.5

Poly[diaqua(µ-citrato)dirubidium(I)sodium(I)] (KADU1681_publ). Crystal data

[NaRb2(C6H5O7)(H2O)2]	V = 1197.94 (8) Å3
Mr = 419.05	Z = 4
Orthorhombic, Pna21	Dx = 2.342 Mg m−3
Hall symbol: P 2c -2n	Kα1, Kα2 radiation, λ = 1.540593, 1.544451 Å
a = 12.1101 (3) Å	T = 300 K
b = 17.2422 (5) Å	flat_sheet, 25 × 25 mm
c = 5.73715 (18) Å	Specimen preparation: Prepared at 450 K

Poly[diaqua(µ-citrato)dirubidium(I)sodium(I)] (KADU1681_publ). Data collection

Bruker D2 Phaser diffractometer	Data collection mode: reflection
Radiation source: sealed X-ray tube	Scan method: step
Ni filter monochromator	2θmin = 5.001°, 2θmax = 100.007°, 2θstep = 0.020°
Specimen mounting: standard PMMA holder

Poly[diaqua(µ-citrato)dirubidium(I)sodium(I)] (KADU1681_publ). Refinement

Least-squares matrix: full	67 parameters
Rp = 0.035	29 restraints
Rwp = 0.047	Only H-atom displacement parameters refined
Rexp = 0.023	Weighting scheme based on measured s.u.'s
R(F2) = 0.21645	(Δ/σ)max = 0.04
4701 data points	Background function: GSAS Background function number 1 with 3 terms. Shifted Chebyshev function of 1st kind 1: 1693.18 2: -250.425 3: 22.2802
Profile function: CW Profile function number 4 with 18 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 0.000 #2(GV) = 0.000 #3(GW) = 5.109 #4(GP) = 0.000 #5(LX) = 3.634 #6(ptec) = 0.00 #7(trns) = 1.30 #8(shft) = -4.0778 #9(sfec) = 0.00 #10(S/L) = 0.0295 #11(H/L) = 0.0097 #12(eta) = 0.9000 #13(S400 ) = 3.3E-04 #14(S040 ) = 2.5E-05 #15(S004 ) = 0.0E+00 #16(S220 ) = 6.5E-03 #17(S202 ) = 9.2E-04 #18(S022 ) = 3.0E-03 Peak tails are ignored where the intensity is below 0.0100 times the peak Aniso. broadening axis 0.0 0.0 1.0

Poly[diaqua(µ-citrato)dirubidium(I)sodium(I)] (KADU1681_publ). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.1222 (10)	0.4396 (8)	0.41415	0.024 (4)*
C2	0.2395 (12)	0.4503 (9)	0.498 (5)	0.034 (12)*
C3	0.2929 (9)	0.5252 (5)	0.405 (5)	0.034 (12)*
C4	0.4049 (12)	0.5361 (8)	0.528 (6)	0.034 (12)*
C5	0.4633 (12)	0.6091 (6)	0.450 (6)	0.024 (4)*
C6	0.2178 (17)	0.5957 (9)	0.460 (6)	0.024 (4)*
H7	0.28466	0.40490	0.44629	0.045 (15)*
H8	0.24038	0.45278	0.67213	0.045 (15)*
H9	0.45297	0.49037	0.49350	0.045 (15)*
H10	0.39304	0.53952	0.70018	0.045 (15)*
O11	0.0717 (10)	0.3782 (9)	0.471 (7)	0.024 (4)*
O12	0.0665 (13)	0.4969 (9)	0.337 (6)	0.024 (4)*
O13	0.5481 (13)	0.6042 (9)	0.322 (7)	0.024 (4)*
O14	0.4444 (16)	0.6727 (8)	0.552 (7)	0.024 (4)*
O15	0.196 (2)	0.6441 (11)	0.301 (7)	0.024 (4)*
O16	0.195 (2)	0.6118 (13)	0.670 (6)	0.024 (4)*
O17	0.3087 (15)	0.5187 (14)	0.159 (5)	0.024 (4)*
H18	0.34428	0.55892	0.13326	0.031 (5)*
Na19	0.1149 (15)	0.5624 (9)	−0.072 (8)	0.048 (8)*
Rb20	0.3036 (3)	0.7303 (2)	0.995 (6)	0.0662 (17)*
Rb21	0.0285 (3)	0.3392 (3)	0.968 (5)	0.0662 (17)*
O22	0.5625 (14)	0.7125 (12)	−0.060 (9)	0.05*
O23	0.2385 (16)	0.7991 (12)	0.489 (12)	0.05*
H24	0.52628	0.68621	0.03931	0.065*
H25	0.54984	0.69167	−0.19160	0.065*
H26	0.17964	0.82566	0.50138	0.065*
H27	0.21772	0.75215	0.47697	0.065*

Poly[diaqua(µ-citrato)dirubidium(I)sodium(I)] (KADU1681_publ). Geometric parameters (Å, º)

C1—C2	1.511 (2)	O16—C6	1.267 (6)
C1—O11	1.265 (6)	O16—Na19vi	1.97 (4)
C1—O12	1.275 (6)	O16—Rb20	3.06 (3)
C2—C1	1.511 (2)	O16—Rb21iv	3.07 (3)
C2—C3	1.541 (2)	O17—C3	1.426 (6)
C3—C2	1.541 (2)	O17—Na19	2.80 (3)
C3—C4	1.541 (2)	O17—Rb20iii	3.77 (2)
C3—C6	1.550 (2)	Na19—O11iv	2.49 (2)
C3—O17	1.426 (6)	Na19—O12	2.67 (4)
C4—C3	1.541 (2)	Na19—O12iv	2.48 (2)
C4—C5	1.512 (2)	Na19—O15	2.74 (4)
C5—C4	1.512 (2)	Na19—O16iii	1.97 (4)
C5—O13	1.264 (6)	Na19—O17	2.80 (3)
C5—O14	1.264 (6)	Rb20—O11vii	2.967 (14)
C6—C3	1.550 (2)	Rb20—O14	3.22 (2)
C6—O15	1.266 (6)	Rb20—O14vi	3.76 (3)
C6—O16	1.267 (6)	Rb20—O15vi	2.65 (3)
O11—C1	1.265 (6)	Rb20—O16	3.06 (3)
O11—Na19i	2.49 (2)	Rb20—O17vi	3.77 (2)
O11—Rb20ii	2.967 (14)	Rb20—O22vi	3.165 (18)
O11—Rb21iii	3.01 (4)	Rb20—O22viii	3.099 (18)
O11—Rb21	2.97 (4)	Rb20—O23	3.24 (7)
O12—C1	1.275 (6)	Rb20—O23vi	3.17 (7)
O12—Na19	2.67 (4)	Rb21—O11	2.97 (4)
O12—Na19i	2.48 (2)	Rb21—O11vi	3.01 (4)
O12—Rb21iii	3.48 (2)	Rb21—O12vi	3.48 (2)
O12—Rb21iv	3.142 (17)	Rb21—O12i	3.142 (17)
O13—C5	1.264 (6)	Rb21—O14ix	2.929 (15)
O13—O14	2.171 (10)	Rb21—O15i	2.89 (3)
O14—C5	1.264 (6)	Rb21—O16i	3.07 (3)
O14—O13	2.171 (10)	Rb21—O22x	3.65 (4)
O14—Rb20iii	3.76 (3)	Rb21—O23ix	2.91 (2)
O14—Rb20	3.22 (2)	O22—Rb20iii	3.165 (18)
O14—Rb21v	2.929 (15)	O22—Rb20xi	3.099 (18)
O15—C6	1.266 (6)	O22—Rb21xii	3.65 (4)
O15—Na19	2.74 (4)	O23—Rb20iii	3.17 (7)
O15—Rb20iii	2.65 (3)	O23—Rb20	3.24 (7)
O15—Rb21iv	2.89 (3)	O23—Rb21v	2.91 (2)
C2—C1—O11	118.3 (6)	O12iv—Na19—O15	133.7 (13)
C2—C1—O12	120.8 (6)	O12iv—Na19—O16iii	117.4 (19)
O11—C1—O12	118.8 (6)	O15—Na19—O16iii	100.9 (9)
C1—C2—C3	112.7 (5)	O11vii—Rb20—O14	87.7 (7)
C2—C3—C4	108.2 (5)	O11vii—Rb20—O15vi	140.0 (11)
C2—C3—C6	109.9 (5)	O11vii—Rb20—O16	139.7 (11)
C2—C3—O17	109.6 (6)	O11vii—Rb20—O22vi	64.8 (5)
C4—C3—C6	109.1 (5)	O11vii—Rb20—O22viii	101.6 (4)
C4—C3—O17	110.1 (6)	O11vii—Rb20—O23	76.5 (9)
C6—C3—O17	110.0 (5)	O11vii—Rb20—O23vi	81.1 (8)
C3—C4—C5	112.2 (5)	O14—Rb20—O15vi	127.8 (6)
C4—C5—O13	119.7 (6)	O14—Rb20—O16	62.6 (6)
C4—C5—O14	120.0 (6)	O14—Rb20—O22vi	50.7 (9)
O13—C5—O14	118.3 (5)	O14—Rb20—O22viii	121.2 (11)
C3—C6—O15	119.7 (6)	O14—Rb20—O23	62.2 (7)
C3—C6—O16	119.6 (6)	O14—Rb20—O23vi	162.3 (6)
O15—C6—O16	119.6 (6)	O15vi—Rb20—O22vi	120.1 (9)
C1—O11—Na19i	94.0 (9)	O15vi—Rb20—O22viii	77.3 (8)
C1—O11—Rb20ii	119.0 (11)	O15vi—Rb20—O23	132.9 (7)
C1—O11—Rb21iii	91.3 (19)	O15vi—Rb20—O23vi	59.7 (7)
C1—O11—Rb21	122 (2)	O16—Rb20—O22vi	107.4 (7)
Na19i—O11—Rb20ii	145.0 (7)	O16—Rb20—O22viii	75.3 (8)
Na19i—O11—Rb21iii	80.7 (12)	O16—Rb20—O23	66.0 (7)
Na19i—O11—Rb21	91.7 (12)	O16—Rb20—O23vi	133.4 (6)
Rb20ii—O11—Rb21iii	86.6 (9)	O22vi—Rb20—O22viii	162.5 (13)
Rb20ii—O11—Rb21	81.4 (7)	O22vi—Rb20—O23	100.8 (11)
Rb21iii—O11—Rb21	146.9 (5)	O22vi—Rb20—O23vi	111.8 (11)
C1—O12—Na19	121.0 (17)	O22viii—Rb20—O23	64.0 (10)
C1—O12—Na19i	94.4 (9)	O22viii—Rb20—O23vi	74.8 (10)
C1—O12—Rb21iv	144.0 (17)	O23—Rb20—O23vi	127.2 (6)
Na19—O12—Na19i	123.6 (13)	O11—Rb21—O11vi	146.9 (5)
Na19—O12—Rb21iv	84.8 (6)	O11—Rb21—O12i	68.4 (5)
Na19i—O12—Rb21iv	89.8 (6)	O11—Rb21—O14ix	111.2 (6)
C5—O14—Rb20	137.0 (10)	O11—Rb21—O15i	79.9 (7)
C5—O14—Rb21v	138.7 (12)	O11—Rb21—O16i	117.1 (6)
Rb20—O14—Rb21v	83.6 (4)	O11—Rb21—O23ix	85.6 (14)
C6—O15—Na19	107.4 (16)	O11vi—Rb21—O12i	95.2 (4)
C6—O15—Rb20iii	138 (2)	O11vi—Rb21—O14ix	92.3 (6)
C6—O15—Rb21iv	91.6 (15)	O11vi—Rb21—O15i	117.3 (6)
Na19—O15—Rb20iii	87.0 (10)	O11vi—Rb21—O16i	74.3 (5)
Na19—O15—Rb21iv	88.6 (9)	O11vi—Rb21—O23ix	81.1 (14)
Rb20iii—O15—Rb21iv	128.9 (5)	O12i—Rb21—O14ix	164.1 (5)
C6—O16—Na19vi	137 (2)	O12i—Rb21—O15i	59.2 (6)
C6—O16—Rb20	129 (2)	O12i—Rb21—O16i	61.2 (5)
C6—O16—Rb21iv	83.8 (15)	O12i—Rb21—O23ix	125.4 (6)
Na19vi—O16—Rb20	92.4 (12)	O14ix—Rb21—O15i	104.9 (6)
Na19vi—O16—Rb21iv	88.1 (12)	O14ix—Rb21—O16i	107.8 (6)
Rb20—O16—Rb21iv	115.2 (5)	O14ix—Rb21—O23ix	69.6 (5)
O11iv—Na19—O12	83.5 (11)	O15i—Rb21—O16i	43.0 (3)
O11iv—Na19—O12iv	52.2 (4)	O15i—Rb21—O23ix	161.4 (14)
O11iv—Na19—O15	92.0 (12)	O16i—Rb21—O23ix	155.2 (15)
O11iv—Na19—O16iii	110.2 (17)	Rb20iii—O22—Rb20xi	153.1 (9)
O12—Na19—O12iv	79.4 (8)	Rb20iii—O23—Rb20	127.2 (6)
O12—Na19—O15	67.0 (11)	Rb20iii—O23—Rb21v	79.1 (12)
O12—Na19—O16iii	162.5 (17)	Rb20—O23—Rb21v	83.6 (12)

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

(kadu1681_DFT). Crystal data

C6H9NaO9Rb2	b = 17.2422 Å
Mr = 419.05	c = 5.7371 Å
Orthorhombic, Pna21	V = 1197.94 Å3
a = 12.1101 Å	Z = 4

(kadu1681_DFT). Data collection

h = →	l = →
k = →

(kadu1681_DFT). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.11349	0.44294	0.51714	0.02400*
C2	0.23597	0.45666	0.57421	0.03400*
C3	0.28367	0.52794	0.45370	0.03400*
C4	0.40500	0.54379	0.52712	0.03400*
C5	0.45823	0.61018	0.38987	0.02400*
C6	0.21792	0.60115	0.52617	0.02400*
H7	0.28454	0.40572	0.52464	0.04500*
H8	0.24316	0.46248	0.76364	0.04500*
H9	0.45422	0.49133	0.49852	0.04500*
H10	0.40815	0.55714	0.71290	0.04500*
O11	0.07326	0.37761	0.57270	0.02400*
O12	0.05725	0.49630	0.42197	0.02400*
O13	0.44070	0.61196	0.17085	0.02400*
O14	0.51674	0.65996	0.49354	0.02400*
O15	0.19321	0.64945	0.36630	0.02400*
O16	0.19781	0.61091	0.73943	0.02400*
O17	0.27723	0.51384	0.20845	0.02400*
H18	0.33394	0.54823	0.14074	0.03100*
Na19	0.10971	0.56678	0.07196	0.04800*
Rb20	0.28861	0.74043	0.99974	0.06620*
Rb21	0.02821	0.33790	1.05852	0.06620*
O22	0.55613	0.71905	−0.07701	0.05000*
O23	0.24192	0.79591	0.51019	0.05000*
H24	0.52483	0.68516	0.04328	0.06500*
H25	0.54732	0.68753	−0.21777	0.06500*
H26	0.17541	0.82757	0.50229	0.06500*
H27	0.21390	0.74353	0.47482	0.06500*

(kadu1681_DFT). Bond lengths (Å)

C1—C2	1.537	C4—H10	1.091
C1—O11	1.268	C5—O13	1.275
C1—O12	1.268	C5—O14	1.262
C2—C3	1.524	C6—O15	1.275
C2—H7	1.095	C6—O16	1.259
C2—H8	1.095	O17—H18	0.987
C3—C4	1.553	O22—H24	0.980
C3—C6	1.549	O22—H25	0.979
C3—O17	1.430	O23—H26	0.974
C4—C5	1.532	O23—H27	0.986
C4—H9	1.096

(kadu1681_DFT). Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O23—H27···O15	0.986	1.755	2.721	165.6
O23—H26···O14	0.974	1.934	2.833	152.2
O22—H25···O14	0.979	1.762	2.708	161.4
O22—H24···O13	0.980	1.779	2.718	159.0
O17—H18···O13	0.987	1.705	2.613	151.0
C4—H9···O13	1.096	2.402	3.374	147.0