Sodium rubidium hydrogen citrate, NaRbHC6H5O7, and sodium caesium hydrogen citrate, NaCsHC6H5O7: crystal structures and DFT comparisons

Cigler, A.J.; Kaduk, J.A.

doi:10.1107/S205698901900063X

research communications

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ISSN: 2056-9890

Volume 75| Part 2| February 2019| Pages 223-227

https://doi.org/10.1107/S205698901900063X

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Sodium rubidium hydrogen citrate, NaRbHC₆H₅O₇, and sodium caesium hydrogen citrate, NaCsHC₆H₅O₇: crystal structures and DFT comparisons

Andrew J. Cigler ^a and James A. Kaduk ^a ^*

^aDepartment of Chemistry, North Central College, 131 S. Loomis St., Naperville IL 60540, USA
^*Correspondence e-mail: kaduk@polycrystallography.com

Edited by A. Van der Lee, Université de Montpellier II, France (Received 23 November 2018; accepted 12 January 2019; online 18 January 2019)

The crystal structure of sodium rubidium hydrogen citrate, NaRbHC₆H₅O₇ or [NaRb(C₆H₆O₇)]_n, has been solved and refined using laboratory powder X-ray diffraction data, and optimized using density functional techniques. This compound is isostructural to NaKHC₆H₅O₇. The Na atom is six-coordinate, with a bond-valence sum of 1.16. The Rb atom is eight-coordinate, with a bond-valence sum of 1.17. The distorted [NaO₆] octahedra share edges to form chains along the a-axis direction. The irregular [RbO₈] coordination polyhedra share edges with the [NaO₆] octahedra on either side of the chain, and share corners with other Rb atoms, resulting in triple chains along the a-axis direction. The most prominent feature of the structure is the chain along [111] of very short, very strong hydrogen bonds; the O⋯O distances are 2.426 and 2.398 Å. The Mulliken overlap populations in these hydrogen bonds are 0.140 and 0.143 electrons, which correspond to hydrogen-bond energies of about 20.3 kcal mol⁻¹. The crystal structure of sodium caesium hydrogen citrate, NaCsHC₆H₅O₇ or [NaCs(C₆H₆O₇)]_n, has also been solved and refined using laboratory powder X-ray diffraction data, and optimized using density functional techniques. The Na atom is six-coordinate, with a bond-valence sum of 1.15. The Cs atom is eight-coordinate, with a bond-valence sum of 0.97. The distorted trigonal–prismatic [NaO₆] coordination polyhedra share edges to form zigzag chains along the b-axis direction. The irregular [CsO₈] coordination polyhedra share edges with the [NaO₆] polyhedra to form layers parallel to the (101) plane, unlike the isolated chains in NaKHC₆H₅O₇ and NaRbHC₆H₅O₇. A prominent feature of the structure is the chain along [100] of very short, very strong O—H⋯O hydrogen bonds; the refined O⋯O distances are 2.398 and 2.159 Å, and the optimized distances are 2.398 and 2.347 Å. The Mulliken overlap populations in these hydrogen bonds are 0.143 and 0.133 electrons, which correspond to hydrogen-bond energies about 20.3 kcal mol⁻¹.

Keywords: powder diffraction; density functional theory; citrate; sodium; rubidium; caesium; crystal structure.

CCDC references: 1890745; 1890746; 1890747; 1890748

1. 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 ). The two title compounds (Figs. 1 and 2) are a further extension to citrates that contain more than one alkali metal cation.

Figure 1
The asymmetric unit of NaRbHC₆H₅O₇, with the atom numbering and 50% probability spheroids.

Figure 2
The asymmetric unit of NaCsHC₆H₅O₇, with the atom numbering and 50% probability spheroids.

2. Structural commentary

Sodium rubidium hydrogen citrate is isostructural to NaKHC₆H₅O₇ (Rammohan & Kaduk, 2016 ). Sodium caesium hydrogen citrate has a related but different structure. The root-mean-square deviations of the non-hydrogen atoms in the refined and optimized structures are 0.116 and 0.105 Å for NaRbHC₆H₅O₇ and NaCsHC₆H₅O₇, respectively. Comparisons of the refined and optimized structures are given in Figs. 3 and 4. The excellent agreement between the structures is strong evidence that the experimental structures are correct (van de Streek & Neumann, 2014 ). This discussion uses the DFT-optimized structures. All of the citrate bond distances, 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 occur in the normal planar arrangement.

Figure 3
Comparison of the refined and optimized structures of sodium rubidium hydrogen 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 caesium hydrogen citrate. The refined structure is in red, and the DFT-optimized structure is in blue.

In the Rb compound, the citrate chelates to Na19 through the terminal carboxylate oxygen O11 and the central carboxylate oxygen O16. The Na⁺ cation is six-coordinate, with a bond-valence sum of 1.16. The Rb⁺ cation is eight-coordinate, with a bond-valence sum of 1.17. Both cations are thus slightly crowded.

In the Cs compound, the citrate triply chelates to Na20 through the terminal carboxylate oxygen O12, the central carboxylate oxygen O15, and the hydroxyl oxygen O17. The Na⁺ cation is six-coordinate, with a bond-valence sum of 1.15. The Cs⁺ cation is eight-coordinate, with a bond-valence sum of 0.97. The Rb—O and Cs—O bonds are ionic, but the Na—O bonds have slight covalent character, according to the Mulliken overlap populations.

The Bravais–Friedel–Donnay–Harker (Bravais, 1866 ; Friedel, 1907 ; Donnay & Harker, 1937 ) method suggests that we might expect a platy morphology for NaRbHC₆H₅O₇, with {001} as the principal faces, and an elongated morphology for NaCsHC₆H₅O₇, with {010} as the long axis. Fourth-order spherical harmonic preferred orientation models were included in the refinements; the texture indices were 1.050 and 1.011, indicating that preferred orientation was slight for the rotated flat-plate specimen of NaRbHC₆H₅O₇, but not significant in this rotated capillary specimen of NaCsHC₆H₅O₇. Examination of the products under an optical microscope indicated that the morphologies were not especially anisotropic.

3. Supramolecular features

In the crystal structure of NaRbHC₆H₅O₇ (Fig. 5), distorted [NaO₆] octahedra share edges to form chains along the a-axis direction. The irregular [RbO₈] coordination polyhedra share edges with the [NaO₆] octahedra on either side of the chain, resulting in triple chains along the a-axis direction. The most prominent feature of the structure is the chain along [111] of very short, very strong O—H⋯O hydrogen bonds (Table 1); the refined O⋯O distances are 2.180 (9) and 2.234 (20) Å, and the optimized distances are 2.426 and 2.398 Å. The Mulliken overlap populations in these hydrogen bonds are 0.140 and 0.143 electrons, which correspond to hydrogen-bond energies about 20.6 kcal mol⁻¹, according to the correlation in Rammohan & Kaduk (2018). H18 forms bifurcated hydrogen bonds: one is intramolecular to O15, and the other is intermolecular to O11.

Table 1
Hydrogen-bond geometry for [NaRb(C₆H₆O₇)]

D—H⋯A	D—H(Å)	H⋯A(Å)	D⋯A(Å)	D—H⋯A(°)	Mulliken overlap(electrons)	H-bond energy(kcal mol⁻¹)
O13—H22⋯O13ⁱ	1.199	1.199	2.398	180.0	0.143	20.7
O11—H21⋯O11ⁱⁱ	1.213	1.213	2.426	180.0	0.140	20.5
O17—H18⋯O15	0.979	1.873	2.575	126.2	0.059	13.3
O17—H18⋯O11ⁱⁱⁱ	0.979	2.507	3.180	125.8	0.016	6.9
C2—H8⋯O14^iv	1.094	2.478	3.541	163.7	0.018
Symmetry codes: (i) 2 − x, 2 − y, 2 − z; (ii) 1 − x, 1 − y, 1 − z; (iii) 1 + x, y, z; (iv) x − 1, y, z.

Figure 5
Crystal structure of NaRbHC₆H₅O₇, viewed down the a axis.

In the crystal structure of NaCsHC₆H₅O₇ (Fig. 6), distorted trigonal–prismatic [NaO₆] share edges to form zigzig chains along the b-axis direction. The irregular [CsO₈] coordination polyhedra share edges with the [NaO₆] polyhedra to form layers parallel to the (101) plane, unlike the isolated chains in NaKHC₆H₅O₇ and NaRbHC₆H₅O₇. A prominent feature of the structure is the chain along [100] of very short, and very strong O—H⋯O hydrogen bonds (Table 2); the refined O11⋯O11 and O14⋯O14 distances are 2.398 and 2.159 Å, and the optimized distances are 2.398 and 2.347 Å. The Mulliken overlap populations in these hydrogen bonds are 0.143 and 0.133 electrons, which correspond to hydrogen-bond energies about 20.3 kcal mol⁻¹. H18 forms an intramolecular hydrogen bond to O13, one of the terminal carboxylate oxygen atoms.

Table 2
Hydrogen-bond geometry for [NaCs(C₆H₆O₇)]

D—H⋯A	D—H(Å)	H⋯A(Å)	D⋯A(Å)	D—H⋯A(°)	Mulliken overlap(electrons)	H-bond energy(kcal mol⁻¹)
O14—H22⋯O14ⁱ	1.200	1.200	2.347	156.1	0.133	19.9
O11—H21⋯O11ⁱⁱ	1.203	1.203	2.398	170.6	0.143	20.7
O17—H18⋯O13¹¹¹	0.976	1.941	2.779	142.4	0.046	11.7
Symmetry codes: (i) − $[{1\over 2}]$ − x, − $[{1\over 2}]$ + y, $[{1\over 2}]$ − z; (ii) −x, y, −z; (iii) $[{1\over 2}]$ + x, − $[{1\over 2}]$ − y, − $[{1\over 2}]$ + z.

Figure 6
Crystal structure of NaCsHC₆H₅O₇, viewed down the b axis.

4. Database survey

Details of the comprehensive literature search for citrate structures are presented in Rammohan & Kaduk (2018). After manually locating the peaks in the pattern of NaRbHC₆H₅O₇, the pattern was indexed using Jade9.8 (MDI, 2017 ). A reduced-cell search in the Cambridge Structural Database (CSD Version 5.39, update of November 2018; Groom et al., 2016 ) yielded 39 hits, among which was NaKHC₆H₅O₇ (Rammohan & Kaduk, 2016).

After manually locating the peaks in the pattern of NaCsHC₆H₅O₇, the pattern was indexed on a C-centered monoclinic cell using Jade9.8 (MDI, 2017). A reduced-cell search in the CSD yielded no hits. The cell was converted to I-centered, to yield a β angle closer to 90°.

5. Synthesis and crystallization

Stoichiometric quantities of Na₂CO₃ and Rb₂CO₃ were added to a solution of 10.0 mmol citric acid monohydrate in 10 mL water. After the fizzing subsided, the clear solution was dried in an oven at 403 K to yield the white solid NaRbHC₆H₅O₇.

2.0236 g (10.0 mmol) of H₃C₆H₅O₇(H₂O) were dissolved in 10 mL of deionized water. 0.5318 g of Na₂CO₃ (1.0 mmol Na, Sigma–Aldrich) and 1.6911 g of Cs₂CO₃ (10.0 mmol of Ca, Sigma–Aldrich) were added to the citric acid solution slowly with stirring. The resulting clear colorless solution was evaporated to dryness in a 403 K oven to yield NaCsHC₆H₅O₇.

6. Refinement

The initial structural model for NaRbHC₆H₅O₇ was taken from Rammohan & Kaduk (2016), replacing the K by Rb and changing the lattice parameters to the observed values. Pseudovoigt profile coefficients were as parameterized in Thompson et al. (1987 ) and the asymmetry correction of Finger et al. (1994 ) was applied as well as the microstrain broadening description by Stephens (1999 ). The hydrogen atoms were included in fixed positions, which were re-calculated during the course of the refinement. Crystal data, data collection and structure refinement (Fig. 7) details are summarized in Table 3. The U_iso of C2, C3, and C4 were constrained to be equal, and those of H7, H8, H9, and H10 were constrained to be 1.3 × that of these carbon atoms. The U_iso of C1, C5, C6, and the oxygen atoms were constrained to be equal, and that of H18 was constrained to be 1.3 × this value. The U_iso of H21 and H22 were fixed.

Table 3
Experimental details

	[NaRb(C₆H₆O₇)]	[NaCs(C₆H₆O₇)]
Crystal data
M_r	298.57	346.00
Crystal system, space group	Triclinic, P $[\overline{1}]$	Monoclinic, I2
Temperature (K)	300	300
a, b, c (Å)	5.9864 (2), 8.4104 (3), 10.2903 (3)	10.8913 (5), 5.5168 (2), 17.7908 (8)
α, β, γ (°)	74.798 (3), 76.756 (3), 72.878 (2)	90, 97.014 (4), 90
V (Å³)	471.28 (3)	1060.96 (6)
Z	2	4
Radiation type	Kα₁, Kα₂, λ = 1.540593, 1.544451 Å	Kα₁, Kα₂, λ = 0.709319, 0.713609 Å
μ (mm⁻¹)	–	2.09
Specimen shape, size (mm)	Flat sheet, 24 × 24	Cylinder, 12 × 0.3

Data collection
Diffractometer	Bruker D2 Phaser	PANalytical Empyrean
Specimen mounting	Standard holder	Glass capillary
Data collection mode	Reflection	Transmission
Scan method	Step	Step
2θ values (°)	2θ_min = 5.001 2θ_max = 100.007 2θ_step = 0.020	2θ_min = 1.011 2θ_max = 49.991 2θ_step = 0.017

Refinement
R factors and goodness of fit	R_p = 0.028, R_wp = 0.038, R_exp = 0.022, R(F²) = 0.13613, χ² = 3.028	R_p = 0.045, R_wp = 0.059, R_exp = 0.026, R(F²) = 0.08622, χ² = 5.570
No. of parameters	84	80
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 ), FOX (Favre-Nicolin & Černý, 2002), GSAS (Larson & Von Dreele, 2004 ), Mercury (Macrae et al., 2008), DIAMOND (Crystal Impact, 2015 ) and publCIF (Westrip, 2010 ).

Figure 7
Rietveld plot for NaRbHC₆H₅O₇. 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 > 46.0°. The row of black tick marks indicates the reflection positions for this phase.

Analysis of the systematic absences in the pattern of NaCsHC₆H₅O₇ suggested the space groups I2, Im, or I2/m. The volume of the unit cell corresponded to Z = 4. Space group I2 was selected, and confirmed by successful solution and refinement of the structure. The structure was solved with FOX (Favre-Nicolin & Černý, 2002 ). The maximum sin θ/λ used for structure solution was 0.55 Å, and a citrate, Cs, Na, and O (water molecule) were used as fragments. The solution with the lowest cost factor has the Cs, Na, and O on top of each other, but the Cs was eight-coordinate and all six carboxylate oxygen atoms were coordinated to the Cs atom. The structure was examined for voids using Materials Studio (Dassault Systemes, 2017 ). One void at approximately 0.375,0.600,0.379 had acceptable coordination to O atoms, and was assigned as Na20. Another void was assigned as O21, but this moved too close to the citrate anion on refinement and was discarded. Active hydrogen atoms were placed by analysis of hydrogen-bonding interactions. The refinement strategy (Fig. 8) was similar to that used for the Rb compound. Cs19 was refined anisotropically.

Figure 8
Rietveld plot for NaCsHC₆H₅O₇. 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 > 28.8°. 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 sets for Rb and Cs were those 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 10.8 and 7.5 h.

Supporting information

CCDC references: 1890745; 1890746; 1890747; 1890748

Crystal structure: contains datablocks KADU1716_publ, kadu1716_DFT, ACIG017_publ, acig017_DFT. DOI: https://doi.org/10.1107/S205698901900063X/vn2138sup1.cif

checkCIF report

Computing details top

Data collection: DIFFRAC.Measurement (Bruker, 2009) for KADU1716_publ, ACIG017_publ. Program(s) used to solve structure: FOX (Favre-Nicolin & Černý, 2002) for KADU1716_publ, ACIG017_publ. Program(s) used to refine structure: GSAS (Larson & Von Dreele, 2004) for KADU1716_publ, ACIG017_publ. Molecular graphics: Mercury (Macrae et al., 2008), DIAMOND (Crystal Impact, 2015) for KADU1716_publ, ACIG017_publ. Software used to prepare material for publication: publCIF (Westrip, 2010) for KADU1716_publ, ACIG017_publ.

Poly[(µ-hydrogen citrato)rubidiumsodium] (KADU1716_publ) top

Crystal data top

[NaRb(C₆H₆O₇)]	V = 471.28 (3) Å³
M_r = 298.57	Z = 2
Triclinic, P1	D_x = 2.104 Mg m⁻³
Hall symbol: -P 1	Kα₁, Kα₂ radiation, λ = 1.540593, 1.544451 Å
a = 5.9864 (2) Å	T = 300 K
b = 8.4104 (3) Å	Particle morphology: powder
c = 10.2903 (3) Å	white
α = 74.798 (3)°	flat_sheet, 24 × 24 mm
β = 76.756 (3)°	Specimen preparation: Prepared at 403 K
γ = 72.878 (2)°

Data collection top

Bruker D2 Phaser diffractometer	Data collection mode: reflection
Radiation source: selaed X-ray tube	Scan method: step
Specimen mounting: standard holder	2θ_min = 5.001°, 2θ_max = 100.007°, 2θ_step = 0.020°

Refinement top

Least-squares matrix: full	84 parameters
R_p = 0.028	29 restraints
R_wp = 0.038	2 constraints
R_exp = 0.022	Only H-atom displacement parameters refined
R(F²) = 0.13613	Weighting scheme based on measured s.u.'s
4701 data points	(Δ/σ)_max = 0.03
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) = 2.580 #2(GV) = 0.000 #3(GW) = 1.999 #4(GP) = 0.000 #5(LX) = 4.181 #6(ptec) = 1.74 #7(trns) = 4.34 #8(shft) = -2.5167 #9(sfec) = 0.00 #10(S/L) = 0.0235 #11(H/L) = 0.0200 #12(eta) = 0.0000 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0	Background function: GSAS Background function number 1 with 10 terms. Shifted Chebyshev function of 1st kind 1: 1751.95 2: -322.287 3: 62.9433 4: -1.65870 5: 15.3537 6: -30.8122 7: 27.0452 8: -10.7829 9: 5.15006 10: -0.147912

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.592 (2)	0.5051 (13)	0.6742 (10)	0.021 (2)*
C2	0.556 (2)	0.5974 (17)	0.7878 (10)	0.003 (6)*
C3	0.7655 (17)	0.6762 (10)	0.7701 (7)	0.003 (6)*
C4	0.744 (2)	0.7373 (16)	0.9020 (8)	0.003 (6)*
C5	0.905 (3)	0.851 (3)	0.8880 (9)	0.021 (2)*
C6	0.7512 (17)	0.8313 (11)	0.6487 (8)	0.021 (2)*
H7	0.54367	0.50387	0.89029	0.004 (7)*
H8	0.38434	0.70246	0.78480	0.004 (7)*
H9	0.79156	0.62260	0.98785	0.004 (7)*
H10	0.55240	0.80973	0.93127	0.004 (7)*
O11	0.507 (2)	0.5851 (14)	0.5670 (8)	0.021 (2)*
O12	0.657 (3)	0.3441 (14)	0.6967 (12)	0.021 (2)*
O13	0.898 (3)	0.9131 (19)	0.9900 (15)	0.021 (2)*
O14	1.045 (2)	0.8875 (18)	0.7771 (10)	0.021 (2)*
O15	0.914 (3)	0.8275 (16)	0.5451 (11)	0.021 (2)*
O16	0.5597 (18)	0.9458 (15)	0.6434 (12)	0.021 (2)*
O17	0.983 (2)	0.5533 (13)	0.7469 (11)	0.021 (2)*
H18	1.06896	0.61913	0.65793	0.027 (3)*
Na19	0.2740 (17)	0.8715 (12)	0.5586 (9)	0.038 (5)*
Rb20	0.1828 (6)	0.2215 (5)	0.7148 (3)	0.060 (2)*
H21	0.5	0.5	0.5	0.03*
H22	1.0	1.0	1.0	0.03*

Geometric parameters (Å, º) top

C1—C2	1.5091 (17)	O14—Rb20^iv	3.028 (14)
C1—O11	1.261 (3)	O15—C6	1.269 (3)
C1—O12	1.267 (3)	O15—Na19ⁱⁱ	2.332 (16)
C2—C1	1.5091 (17)	O15—Na19^v	2.504 (13)
C2—C3	1.5403 (17)	O15—Rb20ⁱ	3.013 (16)
C3—C2	1.5403 (17)	O16—C3	2.429 (6)
C3—C4	1.5392 (17)	O16—C6	1.263 (3)
C3—C6	1.5486 (17)	O16—O15	2.193 (8)
C3—O17	1.419 (3)	O16—O16^v	3.04 (2)
C4—C3	1.5392 (17)	O16—Na19	2.382 (17)
C4—C5	1.5111 (17)	O16—Na19^v	2.439 (13)
C5—C4	1.5111 (17)	O16—Rb20^vi	2.839 (11)
C5—O13	1.275 (3)	O17—C3	1.419 (3)
C5—O14	1.274 (3)	O17—Rb20ⁱⁱ	2.769 (10)
C6—C3	1.5486 (17)	Na19—O11	2.393 (16)
C6—O15	1.269 (3)	Na19—O12ⁱ	3.453 (14)
C6—O16	1.263 (3)	Na19—O14^vii	2.366 (13)
O11—C1	1.261 (3)	Na19—O15^vii	2.332 (16)
O11—Na19	2.393 (16)	Na19—O15^v	2.504 (13)
O11—Rb20ⁱ	3.366 (12)	Na19—O16	2.382 (17)
O12—C1	1.267 (3)	Na19—O16^v	2.439 (13)
O12—C2	2.411 (8)	Rb20—O11ⁱ	3.366 (12)
O12—Rb20	3.246 (14)	Rb20—O12^vii	3.044 (13)
O12—Rb20ⁱⁱ	3.044 (13)	Rb20—O12	3.246 (14)
O13—C5	1.275 (3)	Rb20—O13ⁱⁱⁱ	2.931 (16)
O13—Rb20ⁱⁱⁱ	2.931 (16)	Rb20—O14^viii	3.028 (14)
O13—H22	1.117 (10)	Rb20—O15ⁱ	3.013 (16)
O14—C4	2.433 (14)	Rb20—O16^ix	2.839 (11)
O14—C5	1.274 (3)	Rb20—O17^vii	2.769 (10)
O14—Na19ⁱⁱ	2.366 (13)

C2—C1—O11	118.7 (8)	O11—Na19—O15^v	158.0 (5)
C2—C1—O12	120.3 (6)	O11—Na19—O16	92.2 (5)
O11—C1—O12	119.1 (7)	O11—Na19—O16^v	108.6 (6)
C1—C2—C3	109.8 (5)	O14^vii—Na19—O15^vii	75.6 (5)
C2—C3—C4	107.2 (4)	O14^vii—Na19—O15^v	93.6 (5)
C2—C3—C6	110.0 (4)	O14^vii—Na19—O16	84.7 (5)
C2—C3—O17	110.1 (5)	O14^vii—Na19—O16^v	140.0 (6)
C4—C3—C6	108.9 (5)	O15^vii—Na19—O15^v	82.9 (6)
C4—C3—O17	110.8 (5)	O15^vii—Na19—O16	159.9 (7)
C6—C3—O17	109.9 (4)	O15^vii—Na19—O16^v	114.6 (6)
C3—C4—C5	113.0 (7)	O15^v—Na19—O16	94.3 (7)
C4—C5—O13	118.6 (6)	O15^v—Na19—O16^v	52.7 (2)
C4—C5—O14	121.5 (11)	O16—Na19—O16^v	78.1 (5)
O13—C5—O14	119.9 (8)	O11ⁱ—Rb20—O12^vii	109.5 (3)
C3—C6—O15	119.6 (5)	O11ⁱ—Rb20—O12	53.0 (3)
C3—C6—O16	119.2 (5)	O11ⁱ—Rb20—O13ⁱⁱⁱ	151.0 (3)
O15—C6—O16	120.1 (6)	O11ⁱ—Rb20—O14^viii	130.8 (3)
C1—O11—Na19	118.5 (9)	O11ⁱ—Rb20—O15ⁱ	67.2 (3)
C1—O11—Rb20ⁱ	123.9 (10)	O11ⁱ—Rb20—O16^ix	77.9 (3)
Na19—O11—Rb20ⁱ	81.1 (4)	O11ⁱ—Rb20—O17^vii	82.2 (3)
C1—O12—Rb20	105.2 (8)	O12^vii—Rb20—O12	144.3 (4)
C1—O12—Rb20ⁱⁱ	110.5 (10)	O12^vii—Rb20—O13ⁱⁱⁱ	93.8 (4)
Rb20—O12—Rb20ⁱⁱ	144.3 (4)	O12^vii—Rb20—O14^viii	78.6 (3)
C5—O13—Rb20ⁱⁱⁱ	132.3 (10)	O12^vii—Rb20—O15ⁱ	68.6 (3)
C5—O14—Na19ⁱⁱ	160.1 (13)	O12^vii—Rb20—O16^ix	135.6 (4)
C5—O14—Rb20^iv	118.0 (12)	O12^vii—Rb20—O17^vii	66.2 (4)
Na19ⁱⁱ—O14—Rb20^iv	81.6 (5)	O12—Rb20—O13ⁱⁱⁱ	98.0 (3)
C6—O15—Na19ⁱⁱ	118.8 (12)	O12—Rb20—O14^viii	137.1 (3)
C6—O15—Na19^v	90.6 (6)	O12—Rb20—O15ⁱ	117.4 (3)
C6—O15—Rb20ⁱ	119.3 (11)	O12—Rb20—O16^ix	76.0 (3)
Na19ⁱⁱ—O15—Na19^v	97.1 (6)	O12—Rb20—O17^vii	79.7 (3)
Na19ⁱⁱ—O15—Rb20ⁱ	121.9 (4)	O13ⁱⁱⁱ—Rb20—O14^viii	69.3 (3)
Na19^v—O15—Rb20ⁱ	79.8 (4)	O13ⁱⁱⁱ—Rb20—O15ⁱ	140.0 (3)
C6—O16—Na19	112.9 (12)	O13ⁱⁱⁱ—Rb20—O16^ix	97.6 (4)
C6—O16—Na19^v	93.8 (6)	O13ⁱⁱⁱ—Rb20—O17^vii	92.2 (4)
C6—O16—Rb20^vi	158.9 (12)	O14^viii—Rb20—O15ⁱ	72.0 (3)
Na19—O16—Na19^v	101.9 (5)	O14^viii—Rb20—O16^ix	66.0 (4)
Na19—O16—Rb20^vi	85.5 (4)	O14^viii—Rb20—O17^vii	139.1 (4)
Na19^v—O16—Rb20^vi	92.3 (4)	O15ⁱ—Rb20—O16^ix	75.4 (4)
O11—Na19—O14^vii	107.9 (5)	O15ⁱ—Rb20—O17^vii	110.9 (4)
O11—Na19—O15^vii	97.9 (6)	O16^ix—Rb20—O17^vii	154.8 (3)

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

(kadu1716_DFT) top

Crystal data top

C₆H₆NaO₇Rb	α = 74.7995°
M_r = 298.57	β = 76.7573°
Triclinic, P1	γ = 72.8749°
a = 5.9859 Å	V = 471.23 Å³
b = 8.4102 Å	Z = 2
c = 10.2904 Å

Data collection top

h = →	l = →
k = →

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.58312	0.48855	0.68564	0.01800*
C2	0.57651	0.57925	0.79638	0.00600*
C3	0.76841	0.67872	0.76846	0.00600*
C4	0.73694	0.75315	0.89436	0.00600*
C5	0.90081	0.86416	0.88638	0.01800*
C6	0.74570	0.82427	0.63974	0.01800*
H7	0.60167	0.48235	0.88975	0.00700*
H8	0.40172	0.66683	0.81269	0.00700*
H9	0.76305	0.64923	0.98397	0.00700*
H10	0.55518	0.83019	0.91496	0.00700*
O11	0.50420	0.58854	0.57498	0.01800*
O12	0.65090	0.33239	0.70086	0.01800*
O13	0.87388	0.91272	0.99960	0.01800*
O14	1.04257	0.90330	0.78197	0.01800*
O15	0.91969	0.81409	0.54210	0.01800*
O16	0.56046	0.94323	0.63928	0.01800*
O17	0.99694	0.56509	0.74766	0.01800*
H18	1.06896	0.61913	0.65793	0.02340*
Na19	0.25929	0.87959	0.56024	0.02900*
Rb20	0.19358	0.22247	0.71319	0.05030*
H21	0.50000	0.50000	0.50000	0.03000*
H22	1.00000	1.00000	1.00000	0.03000*

Bond lengths (Å) top

C1—C2	1.516	C4—H10	1.095
C1—O11	1.318	C5—O13	1.294
C1—O12	1.233	C5—O14	1.243
C2—C3	1.546	C6—O15	1.271
C2—H7	1.092	C6—O16	1.256
C2—H8	1.094	O11—H21	1.213
C3—C4	1.533	O13—H22	1.199
C3—C6	1.551	O17—H18	0.979
C3—O17	1.426	H21—O11ⁱ	1.213
C4—C5	1.517	H22—O13ⁱⁱ	1.199
C4—H9	1.096

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O13—H22···O13	1.199	1.199	2.398	180.0
O11—H21···O11	1.213	1.213	2.426	180.0
O17—H18···O15	0.979	1.873	2.575	126.2
O17—H18···O11	0.979	2.507	3.180	125.8
C2—H8···O14	1.094	2.478	3.541	163.7

Poly[(µ-hydrogen citrato)caesiumsodium] (ACIG017_publ) top

Crystal data top

[CsNa(C₆H₆O₇)]	Z = 4
M_r = 346.00	D_x = 2.166 Mg m⁻³
Monoclinic, I2	Kα₁, Kα₂ radiation, λ = 0.709319, 0.713609 Å
Hall symbol: I 2y	µ = 2.09 mm⁻¹
a = 10.8913 (5) Å	T = 300 K
b = 5.5168 (2) Å	Particle morphology: powder
c = 17.7908 (8) Å	white
β = 97.014 (4)°	cylinder, 12 × 0.3 mm
V = 1060.96 (6) Å³	Specimen preparation: Prepared at 403 K

Data collection top

PANalytical Empyrean diffractometer	Data collection mode: transmission
Radiation source: sealed X-ray tube	Scan method: step
Specimen mounting: glass capillary	2θ_min = 1.011°, 2θ_max = 49.991°, 2θ_step = 0.017°

Refinement top

Least-squares matrix: full	80 parameters
R_p = 0.045	29 restraints
R_wp = 0.059	2 constraints
R_exp = 0.026	Only H-atom displacement parameters refined
R(F²) = 0.08622	Weighting scheme based on measured s.u.'s
2932 data points	(Δ/σ)_max = 0.06
Profile function: CW Profile function number 4 with 21 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) = 53.860 #2(GV) = 0.000 #3(GW) = 0.786 #4(GP) = 0.000 #5(LX) = 1.886 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = 0.0000 #9(sfec) = 0.00 #10(S/L) = 0.0151 #11(H/L) = 0.0173 #12(eta) = 0.5113 #13(S400 ) = 1.1E-01 #14(S040 ) = 4.6E-01 #15(S004 ) = 6.1E-03 #16(S220 ) = 2.3E-01 #17(S202 ) = 3.5E-02 #18(S022 ) = 7.8E-02 #19(S301 ) = 8.2E-02 #20(S103 ) = -1.3E-02 #21(S121 ) = 7.3E-02 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0	Background function: GSAS Background function number 1 with 3 terms. Shifted Chebyshev function of 1st kind 1: 711.736 2: 51.3623 3: -153.142

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.5180 (19)	0.183 (7)	0.3879 (6)	0.027 (3)*
C2	0.5919 (14)	0.118 (3)	0.3242 (6)	0.002 (7)*
C3	0.5465 (10)	0.234 (2)	0.2470 (5)	0.002 (7)*
C4	0.6279 (14)	0.138 (3)	0.1886 (6)	0.002 (7)*
C5	0.588 (2)	0.249 (3)	0.1120 (6)	0.027 (3)*
C6	0.4103 (11)	0.162 (3)	0.2216 (9)	0.027 (3)*
H7	0.58724	−0.0875	0.31719	0.003 (9)*
H8	0.69162	0.17452	0.33886	0.003 (9)*
H9	0.61841	−0.06615	0.18447	0.003 (9)*
H10	0.72772	0.19018	0.20703	0.003 (9)*
O11	0.5625 (17)	0.129 (4)	0.4554 (6)	0.027 (3)*
O12	0.4121 (17)	0.285 (4)	0.3756 (9)	0.027 (3)*
O13	0.601 (3)	0.476 (3)	0.1023 (8)	0.027 (3)*
O14	0.5515 (19)	0.112 (3)	0.0558 (7)	0.027 (3)*
O15	0.3392 (15)	0.319 (3)	0.1871 (10)	0.027 (3)*
O16	0.3821 (15)	−0.062 (3)	0.2172 (12)	0.027 (3)*
O17	0.5558 (14)	0.490 (2)	0.2509 (8)	0.027 (3)*
H18	0.54799	0.56496	0.20157	0.036 (4)*
Cs19	0.3269 (3)	0.70766	0.05362 (15)	0.04276
Na20	0.3483 (18)	0.742 (6)	0.2891 (9)	0.124 (8)*
H21	0.5	0.102	0.5	0.05*
H22	0.5	0.124	0.0	0.05*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cs19	0.039 (3)	0.038 (3)	0.051 (3)	0.006 (5)	0.006 (2)	−0.007 (5)

Geometric parameters (Å, º) top

C1—C2	1.512 (2)	O14—Cs19^iv	3.341 (19)
C1—O11	1.274 (7)	O15—C6	1.272 (7)
C1—O12	1.278 (7)	O15—Cs19	3.189 (17)
C2—C1	1.512 (2)	O15—Na20	2.95 (3)
C2—C3	1.540 (2)	O15—Na20ⁱ	2.18 (2)
C3—C2	1.540 (2)	O16—C6	1.272 (7)
C3—C4	1.540 (2)	O16—Cs19ⁱⁱⁱ	3.17 (2)
C3—C6	1.548 (2)	O16—Na20ⁱⁱⁱ	1.75 (3)
C3—O17	1.419 (7)	O16—Na20ⁱ	3.01 (3)
C4—C3	1.540 (2)	O17—C3	1.419 (7)
C4—C5	1.509 (2)	O17—Na20	2.81 (3)
C5—C4	1.509 (2)	Cs19—O11^v	3.211 (17)
C5—O13	1.272 (7)	Cs19—O12^vi	3.057 (15)
C5—O14	1.275 (7)	Cs19—O13	3.27 (3)
C6—C3	1.548 (2)	Cs19—O13ⁱⁱ	3.236 (17)
C6—O15	1.272 (7)	Cs19—O14^vii	3.309 (17)
C6—O16	1.272 (7)	Cs19—O14^viii	3.341 (19)
O11—C1	1.274 (7)	Cs19—O15	3.189 (17)
O12—C1	1.278 (7)	Cs19—O16^vii	3.17 (2)
O12—Cs19ⁱ	3.057 (15)	Cs19—H18	3.435 (3)
O12—Na20	2.99 (4)	Na20—O12	2.99 (4)
O13—C5	1.272 (7)	Na20—O15	2.95 (3)
O13—Cs19	3.27 (3)	Na20—O15^vi	2.18 (2)
O13—Cs19ⁱⁱ	3.236 (17)	Na20—O16^vii	1.75 (3)
O14—C5	1.275 (7)	Na20—O16^vi	3.01 (3)
O14—O14ⁱⁱ	2.16 (3)	Na20—O17	2.81 (3)
O14—Cs19ⁱⁱⁱ	3.309 (17)

C2—C1—O11	118.3 (5)	C3—O17—H18	112.6 (12)
C2—C1—O12	121.9 (7)	O11^v—Cs19—O12^vi	59.4 (3)
O11—C1—O12	119.8 (6)	O11^v—Cs19—O13	145.2 (5)
C1—C2—C3	115.3 (5)	O11^v—Cs19—O13ⁱⁱ	76.9 (5)
C2—C3—C4	108.1 (6)	O11^v—Cs19—O14^vii	135.3 (5)
C2—C3—C6	110.2 (6)	O11^v—Cs19—O14^viii	99.6 (4)
C2—C3—O17	110.9 (6)	O11^v—Cs19—O15	105.5 (4)
C4—C3—C6	108.9 (6)	O11^v—Cs19—O16^vii	127.7 (5)
C4—C3—O17	109.3 (6)	O12^vi—Cs19—O13	137.9 (6)
C6—C3—O17	109.4 (6)	O12^vi—Cs19—O13ⁱⁱ	135.7 (6)
C3—C4—C5	110.0 (6)	O12^vi—Cs19—O14^vii	124.5 (5)
C4—C5—O13	119.6 (8)	O12^vi—Cs19—O14^viii	124.4 (5)
C4—C5—O14	119.7 (6)	O12^vi—Cs19—O15	75.3 (5)
O13—C5—O14	120.4 (7)	O12^vi—Cs19—O16^vii	68.9 (5)
C3—C6—O15	118.0 (6)	O13—Cs19—O13ⁱⁱ	76.3 (5)
C3—C6—O16	118.9 (7)	O13—Cs19—O14^vii	67.1 (4)
O15—C6—O16	120.4 (6)	O13—Cs19—O14^viii	90.1 (5)
C1—O11—Cs19^ix	134 (2)	O13—Cs19—O15	65.5 (4)
C1—O12—Cs19ⁱ	131.6 (15)	O13—Cs19—O16^vii	81.3 (4)
C5—O13—Cs19	107.5 (19)	O13ⁱⁱ—Cs19—O14^vii	91.2 (5)
C5—O13—Cs19ⁱⁱ	123.3 (10)	O13ⁱⁱ—Cs19—O14^viii	67.1 (3)
Cs19—O13—Cs19ⁱⁱ	85.8 (4)	O13ⁱⁱ—Cs19—O15	112.4 (5)
C5—O14—Cs19ⁱⁱⁱ	124.4 (14)	O13ⁱⁱ—Cs19—O16^vii	155.3 (6)
C5—O14—Cs19^iv	138.3 (18)	O14^vii—Cs19—O14^viii	37.9 (4)
Cs19ⁱⁱⁱ—O14—Cs19^iv	83.5 (4)	O14^vii—Cs19—O15	118.7 (4)
C6—O15—Cs19	141.8 (14)	O14^vii—Cs19—O16^vii	70.2 (4)
C6—O15—Na20ⁱ	107.7 (14)	O14^viii—Cs19—O15	154.1 (4)
Cs19—O15—Na20ⁱ	108.7 (8)	O14^viii—Cs19—O16^vii	102.9 (4)
C6—O16—Cs19ⁱⁱⁱ	117.6 (13)	O15—Cs19—O16^vii	66.3 (3)
C6—O16—Na20ⁱⁱⁱ	129 (2)	O15^vi—Na20—O16^vii	107.9 (15)
Cs19ⁱⁱⁱ—O16—Na20ⁱⁱⁱ	113.1 (11)

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

(acig017_DFT) top

Crystal data top

C6H6CsNaO₇	c = 17.7909 Å
M_r = 346.0	β = 97.0160°
Monoclinic, I2	V = 1060.98 Å³
a = 10.8918 Å	Z = 4
b = 5.5166 Å

Data collection top

DFT calculation	k = →
h = →	l = →

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.01539	−0.29133	−0.11491	0.02190*
C2	0.08720	−0.37073	−0.17866	0.00770*
C3	0.04485	−0.25744	−0.25560	0.00770*
C4	−0.36770	0.15585	0.18731	0.00770*
C5	−0.40727	0.26100	0.10948	0.02190*
C6	−0.09031	−0.33701	−0.28568	0.02190*
H7	0.07745	0.43212	−0.18341	0.01000*
H8	0.18550	−0.33438	−0.16183	0.01000*
H9	−0.36925	−0.04136	0.18368	0.01000*
H10	−0.27329	0.21290	0.20759	0.01000*
O11	0.06648	−0.36068	−0.04898	0.02190*
O12	−0.08435	−0.17967	−0.12642	0.02190*
O13	−0.41832	0.48425	0.09987	0.02190*
O14	−0.43234	0.10103	0.05664	0.02190*
O15	0.33500	0.32450	0.18636	0.02190*
O16	0.38339	−0.05889	0.21767	0.02190*
O17	0.05257	−0.00031	−0.24718	0.02190*
H18	0.04799	0.06496	−0.29843	0.02800*
Cs19	0.31925	−0.29064	0.05016	0.04080*
Na20	−0.15569	0.10811	−0.21537	0.10800*
H21	0.00000	−0.34288	0.00000	0.05000*
H22	0.00000	−0.35387	0.50000	0.05000*

Bond lengths (Å) top

C1—C2	1.519	O15—Na20^xii	2.339
C1—O11	1.293	O16—C6^xii	1.260
C1—O12	1.244	O16—Cs19	3.240
C2—C3	1.524	O16—Na20^xiii	2.258
C2—H7ⁱ	1.095	O16—Na20^vii	2.641
C2—H8	1.095	O17—H18	0.976
C3—C4ⁱⁱ	1.551	O17—Na20	2.477
C3—C6	1.566	Cs19—Cs19^vi	5.517
C3—O17	1.428	Cs19—Cs19ⁱ	5.517
C4—C3ⁱⁱⁱ	1.551	Cs19—O15ⁱ	3.210
C4—C5	1.515	Cs19—O12^vii	3.100
C4—H9	1.090	Cs19—O13^xiv	3.143
C4—H10	1.094	Cs19—O14^xv	3.453
C5—O13	1.247	Cs19—O14^vii	3.220
C5—O14	1.294	Cs19—O13^xvi	3.246
C6—O15^iv	1.267	Cs19—Cs19^xvii	4.517
C6—O16^iv	1.260	Cs19—Na20^xiii	4.184
C6—Na20^v	2.785	Cs19—Na20^vii	4.234
H7—C2^vi	1.095	Na20—O15^vii	2.398
O11—Cs19	3.107	Na20—C6^xviii	2.785
O11—H21	1.203	Na20—Na20^xviii	3.568
O12—Cs19^vii	3.100	Na20—Na20^v	3.568
O12—Na20	2.308	Na20—O16^xi	2.258
O13—Cs19^viii	3.143	Na20—O15^iv	2.339
O13—Cs19^ix	3.246	Na20—O16^vii	2.641
O14—Cs19^x	3.453	Na20—Cs19^xi	4.184
O14—Cs19^vii	3.220	Na20—Cs19^vii	4.234
O14—H22^xi	1.200	H21—O11^vii	1.203
O15—C6^xii	1.267	H22—O14^xix	1.200
O15—Cs19^vi	3.210	H22—O14^xiii	1.200
O15—Na20^vii	2.398

Symmetry codes: (i) x, y−1, z; (ii) x+1/2, y−1/2, z−1/2; (iii) x−1/2, y+1/2, z+1/2; (iv) x−1/2, y−1/2, z−1/2; (v) −x−1/2, y−1/2, −z−1/2; (vi) x, y+1, z; (vii) −x, y, −z; (viii) x−1, y+1, z; (ix) −x, y+1, −z; (x) x−1, y, z; (xi) x−1/2, y+1/2, z−1/2; (xii) x+1/2, y+1/2, z+1/2; (xiii) x+1/2, y−1/2, z+1/2; (xiv) x+1, y−1, z; (xv) x+1, y, z; (xvi) −x, y−1, −z; (xvii) −x+1, y, −z; (xviii) −x−1/2, y+1/2, −z−1/2; (xix) −x−1/2, y−1/2, −z+1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O14—H22···O14	1.200	1.200	2.347	156.1
O11—H21···O11	1.203	1.203	2.398	170.6
O17—H18···O13	0.976	1.941	2.779	142.4

Hydrogen-bond geometry (Å, °, electrons, kcal mol^-1) for [NaRb(C₆H₆O₇)] top

D—H···A	D—H	H···A	D···A	D—H···A	Mulliken overlap	H-bond energy
O13—H22···O13ⁱ	1.199	1.199	2.398	180.0	0.143	20.7
O11—H21···O11ⁱⁱ	1.213	1.213	2.426	180.0	0.140	20.5
O17—H18···O15	0.979	1.873	2.575	126.2	0.059	13.3
O17—H18···O11ⁱⁱⁱ	0.979	2.507	3.180	125.8	0.016	6.9
C2—H8···O14^iv	1.094	2.478	3.541	163.7	0.018

Symmetry codes: (i) 2 - x, 2 - y, 2 - z; (ii) 1 - x, 1 - y, 1 - z; (iii) 1 + x, y, z; (iv) x - 1, y, z.

Hydrogen-bond geometry (Å, °, electrons, kcal mol^-1) for [CsNa(C₆H₆O₇)] top

D—H···A	D—H	H···A	D···A	D—H···A	Mulliken overlap	H-bond energy
O14—H22···O14ⁱ	1.200	1.200	2.347	156.1	0.133	19.9
O11—H21···O11ⁱⁱ	1.203	1.203	2.398	170.6	0.143	20.7
O17—H18···O13¹¹¹	0.976	1.941	2.779	142.4	0.046	11.7

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

Acknowledgements

We thank Andrey Rogachev for the use of computing resources at the Illinois Institute of Technology.

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Volume 75| Part 2| February 2019| Pages 223-227

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