Poly[[hexa­aqua­tris­[μ2-2,5-dihy­droxy-1,4-benzoquinona­to(2−)]diholmium(III)] octa­deca­hydrate]

Nakabayashi, K.; Ohkoshi, S.

doi:10.1107/S1600536810028989

metal-organic compounds

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ISSN: 2056-9890

Volume 66| Part 10| October 2010| Page m1300

doi:10.1107/S1600536810028989

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Poly[[hexaaquatris[μ₂-2,5-dihydroxy-1,4-benzoquinonato(2−)]diholmium(III)] octadecahydrate]

Koji Nakabayashi ^a and Shin-ichi Ohkoshi ^a ^*

^aDepartment of Chemistry, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-0033, Japan
^*Correspondence e-mail: ohkoshi@chem.s.u-tokyo.ac.jp

(Received 7 July 2010; accepted 20 July 2010; online 25 September 2010)

In the polymeric title compound, {[Ho₂(C₆H₂O₄)₃(H₂O)₆]·18H₂O}_n, the Ho^III ion is nine-coordinated by six O atoms derived from three bidentate 2,5-dihydroxy-1,4-benzoquinonate (DHBQ²⁻) ligands and three O atoms from three water molecules. The Ho^III ions are connected via three ligands, resulting in the formation of a two-dimensional honeycomb layer parallel to the ab plane. The layer is racemic in which Δ- and Λ-coordination geometries around Ho^III ions are alternately arranged. The asymmetric unit comprises a third of a Ho^III ion, located on a threefold axis, one-half of a DHBQ²⁻ ion, located on a centre of inversion, one coordinated water molecule and three uncoordinated water molecules.

Related literature

For general background, see: Kitagawa & Kawata (2002 ); Nakabayashi & Ohkoshi (2009 ); Ohkoshi et al. (2001 ). For details of the synthesis, see: Weider et al. (1985 ). For related structures, see: Robl & Sheldrick (1988 ); Weiss et al. (1986 ).

Experimental

Crystal data

[Ho₂(C₆H₂O₄)₃(H₂O)₆]·18H₂O
M_r = 1176.46
Trigonal, $[R \overline 3]$
a = 14.1407 (3) Å
c = 18.0629 (5) Å
V = 3127.93 (12) Å³
Z = 3
Mo Kα radiation
μ = 3.88 mm⁻¹
T = 90 K
0.10 × 0.10 × 0.04 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ) T_min = 0.704, T_max = 0.856
11262 measured reflections
1594 independent reflections
1525 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.023
wR(F²) = 0.063
S = 1.23
1594 reflections
86 parameters
H-atom parameters constrained
Δρ_max = 0.65 e Å⁻³
Δρ_min = −0.30 e Å⁻³

Table 1
Selected bond lengths (Å)

Ho1—O1	2.371 (2)
Ho1—O2	2.463 (2)
Ho1—O3	2.385 (3)

Data collection: PROCESS-AUTO (Rigaku, 1998 ); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku, 2007 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997 ) and pyMOL (DeLano, 2007 ); software used to prepare material for publication: CrystalStructure.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810028989/tk2691sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810028989/tk2691Isup2.hkl

checkCIF report

Comment top

Lanthanide complexes have attracted attention as magnetic and luminescent materials due to the properties of the 4f orbitals in lanthanide ions. Although the magnetism of mononuclear lanthanide complexes are well understood, studies on polynuclear lanthanide complexes are much less advanced (Ohkoshi et al., 2001). The dimensionality of complexes and coordination geometry around lanthanide ions are key factors to control their magnetic properties. From this viewpoint, constructing polynuclear lanthanide complexes with various topologies are interesting. In our previous work, we reported the 3-D monometallic lanthanide metal assembly, Na₅[{Ho(THB^4-)₂}.7H₂O]_n (THB = 1,2,4,5-tetrahydroxybenzene) (Nakabayashi et al., 2009). In this work, we synthesized a 2-D honeycomb network composed of holmium ions (Ho^III) and 2,5-dihydroxy-1,4-benzoquinonate, [{Ho₂ (DHBQ^2-)₃ (H₂O)₆}.18H₂O]_n (Kitagawa et al., 2002; Robl et al., 1988).

The asymmetric unit comprises a third of a Ho^III ion, being located on a three-fold axis, one-half of a DHBQ^2- ion, being disposed about a centre of inversion, one coordinated water molecule, and three zeolitic water molecules.

The C—O distances of 1.276 (4) Å (C1—O1) and 1.274 (3) Å (C2—O2) in this compound agree with those of the DHBQ^2- ligands which were previously reported, e.g. 1.276 (6) Å (Weiss et al. 1986). In the coordination geometry, a Ho^III ion is coordinated to six O atoms from three bidentate DHBQ^2- ligands and three O atoms from three water molecules (Fig. 1 and Table 1). The Ho^III ion is connected via three ligands, which results in a two-dimensional honeycomb layer with a diameter of 16.6 Å. The layer has a racemic structure in which Δ- and Λ-coordination geometries around Ho^III ions are alternately arranged (Fig. 2). The zeolitic water molecules occupy regions between the layers.

The product of the molar magnetic susceptibility (χ_M) and temperature (T), χ_MT, values at room temperature was 13.6 cm³ K mol^-1. This value nearly corresponds to the expected value of 13.9 cm³ K mol^-1 due to Ho^III ions (J = 8, L = 6, S = 2, and g = 5/4).

All known compounds of this type have two specific structures, honeycomb or racemic, and show paramagnetism. Mixing lanthanide ions, the chiral lanthanide assemblies with Δ- or Λ-coordination geometries are targeted for synthesis, which should show a magneto-chiral dichroism. A study to clarify this hypotheses, work is currently under way.

Related literature top

For general background, see: Kitagawa & Kawata (2002); Nakabayashi & Ohkoshi (2009); Ohkoshi et al. (2001). For details of the synthesis, see: Weider et al. (1985). For related structures, see: Robl & Sheldrick (1988); Weiss et al. (1986).

Experimental top

Under air, aqueous solutions of 0.1 M Ho(NO₃)₃ and 0.4 M 1,2,4,5-tetrahydroxybenzene (THB) (Weider et al., 1985) mixed. THB was gradually oxidized to 2,5-dihydroxy-1,4-benzoquinone (DHBQ) in the mixed solution, and slow complexation of Ho(NO₃)₃ and DHBQ) produced red crystals of the title polymer in 24% yield within a week. The obtained polycrystalline compound was dried under air. Elemental analysis indicated the formula was [Ho₂(C₆H₂O₄)₃(H₂O)₆].17H₂O, C₁₈H₅₂O₃₅Ho₂, calcd. Ho, 28.18%; C, 18.47%; H, 4.49%, found. Ho, 28.29%; C, 18.23%; H, 4.64%. There is a slight difference of zeolitic water molecules between the elemental analysis and the crystallographic formulation because zeolitic water molecules are easy to be lost from the crystals and their number depends on the drying processes.

Computing details top

Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and pyMOL (DeLano, 2007); software used to prepare material for publication: CrystalStructure (Rigaku, 2007).

Figures top

	Fig. 1. A part of the title polymeric compound, thermal ellipsoids are shown at the 50% probability level. Blue, gray, and red represent Ho, C and O atoms, respectively. The labeled atoms indicate all independent atoms.
	Fig. 2. A layer with a honeycomb structure. Blue spheres and gray sticks represent Ho atoms and other atoms (C and O), respectively.

Poly[[hexaaquatris[µ₂-2,5-dihydroxy-1,4-benzoquinonato(2-)]diholmium(III)] octadecahydrate] top

Crystal data top

[Ho₂(C₆H₂O₄)₃(H₂O)₆]·18H₂O	D_x = 1.796 Mg m⁻³
M_r = 1176.46	Mo Kα radiation, λ = 0.71075 Å
Trigonal, R3	Cell parameters from 9640 reflections
Hall symbol: -R 3	θ = 3.4–27.5°
a = 14.1407 (3) Å	µ = 3.88 mm⁻¹
c = 18.0629 (5) Å	T = 90 K
V = 3127.93 (12) Å³	Platelet, red
Z = 3	0.10 × 0.10 × 0.04 mm
F(000) = 1608.00

Data collection top

Rigaku R-AXIS RAPID diffractometer	1525 reflections with F² > 2σ(F²)
Detector resolution: 10.00 pixels mm^-1	R_int = 0.025
ω scans	θ_max = 27.5°
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	h = −18→18
T_min = 0.704, T_max = 0.856	k = −18→18
11262 measured reflections	l = −23→23
1594 independent reflections

Refinement top

Refinement on F²	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.023	w = 1/[σ²(F_o²) + (0.0248P)² + 19.995P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.063	(Δ/σ)_max = 0.002
S = 1.23	Δρ_max = 0.65 e Å⁻³
1594 reflections	Δρ_min = −0.30 e Å⁻³
86 parameters

Crystal data top

[Ho₂(C₆H₂O₄)₃(H₂O)₆]·18H₂O	Z = 3
M_r = 1176.46	Mo Kα radiation
Trigonal, R3	µ = 3.88 mm⁻¹
a = 14.1407 (3) Å	T = 90 K
c = 18.0629 (5) Å	0.10 × 0.10 × 0.04 mm
V = 3127.93 (12) Å³

Data collection top

Rigaku R-AXIS RAPID diffractometer	1594 independent reflections
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	1525 reflections with F² > 2σ(F²)
T_min = 0.704, T_max = 0.856	R_int = 0.025
11262 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.023	H-atom parameters constrained
wR(F²) = 0.063	w = 1/[σ²(F_o²) + (0.0248P)² + 19.995P] where P = (F_o² + 2F_c²)/3
S = 1.23	Δρ_max = 0.65 e Å⁻³
1594 reflections	Δρ_min = −0.30 e Å⁻³
86 parameters

Special details top

Geometry. loop_ _Bond lengths and angles

Ho1 - Distance Angles O1_$1 2.3715 (0.0023) O1 2.3715 (0.0024) 78.04 (0.09) O1_$2 2.3715 (0.0023) 78.05 (0.09) 78.05 (0.09) O3_$2 2.3851 (0.0025) 138.54 (0.09) 85.02 (0.10) 134.88 (0.09) O3_$1 2.3851 (0.0025) 134.88 (0.09) 138.54 (0.09) 85.02 (0.10) 80.68 (0.11) O3 2.3852 (0.0025) 85.02 (0.10) 134.88 (0.09) 138.54 (0.09) 80.68 (0.11) 80.68 (0.11) O2_$1 2.4626 (0.0024) 65.01 (0.08) 134.82 (0.08) 69.90 (0.08) 140.07 (0.09) 69.92 (0.09) 68.65 (0.09) O2 2.4626 (0.0023) 69.90 (0.08) 65.01 (0.08) 134.82 (0.08) 68.65 (0.09) 140.07 (0.09) 69.92 (0.08) 119.91 (0.01) O2_$2 2.4626 (0.0023) 134.82 (0.08) 69.90 (0.08) 65.01 (0.08) 69.92 (0.08) 68.65 (0.09) 140.07 (0.09) 119.91 (0.01) Ho1 - O1_$1 O1 O1_$2 O3_$2 O3_$1 O3 O2_$1

O1 - Distance Angles C1 1.2764 (0.0041) Ho1 2.3715 (0.0023) 123.38 (0.21) O1 - C1

O2 - Distance Angles C2 1.2739 (0.0041) Ho1 2.4626 (0.0023) 119.92 (0.21) O2 - C2

O3 - Distance Angles Ho1 2.3852 (0.0025) O3 -

C1 - Distance Angles O1 1.2764 (0.0041) C3 1.3846 (0.0049) 125.21 (0.32) C2 1.5290 (0.0046) 114.26 (0.29) 120.50 (0.30) C1 - O1 C3

C3 - Distance Angles C1 1.3846 (0.0049) C2_$3 1.3982 (0.0048) 119.67 (0.32) H3 0.9500 120.16 120.16 C3 - C1 C2_$3

C2 - Distance Angles O2 1.2739 (0.0041) C3_$3 1.3982 (0.0048) 124.89 (0.31) C1 1.5290 (0.0046) 115.30 (0.29) 119.80 (0.30) C2 - O2 C3_$3

Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

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

	x	y	z	U_iso*/U_eq
Ho1	0.0000	0.0000	0.754297 (13)	0.01802 (8)
O1	−0.1198 (2)	−0.12391 (19)	0.66415 (13)	0.0270 (5)
O2	−0.00678 (19)	−0.17736 (19)	0.75023 (13)	0.0252 (4)
O3	0.1248 (2)	−0.0026 (2)	0.84201 (15)	0.0366 (6)
O4	0.1390 (2)	−0.1541 (2)	0.93023 (18)	0.0481 (7)
O5	0.2672 (2)	0.1817 (2)	0.92192 (19)	0.0508 (7)
O6	−0.1882 (2)	−0.0598 (2)	0.54192 (17)	0.0474 (7)
C1	−0.1492 (2)	−0.2252 (2)	0.66312 (19)	0.0246 (6)
C3	−0.2332 (2)	−0.3039 (2)	0.6206 (2)	0.0283 (7)
C2	−0.0802 (2)	−0.2555 (2)	0.71218 (18)	0.0237 (6)
H3	−0.2770	−0.2850	0.5912	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ho1	0.01630 (11)	0.01630 (11)	0.02146 (14)	0.00815 (5)	0.0000	0.0000
O1	0.0310 (13)	0.0178 (11)	0.0320 (12)	0.0121 (10)	−0.0067 (9)	−0.0020 (9)
O2	0.0240 (11)	0.0194 (11)	0.0316 (12)	0.0103 (9)	−0.0047 (9)	−0.0032 (9)
O3	0.0363 (14)	0.0309 (14)	0.0405 (14)	0.0154 (12)	−0.0164 (11)	−0.0020 (11)
O4	0.0455 (18)	0.0513 (18)	0.0552 (18)	0.0299 (15)	−0.0062 (14)	0.0051 (15)
O5	0.0490 (18)	0.0453 (18)	0.0558 (19)	0.0218 (15)	−0.0121 (15)	−0.0078 (14)
O6	0.0528 (19)	0.0470 (18)	0.0418 (16)	0.0244 (15)	−0.0105 (13)	0.0015 (13)
C1	0.0241 (16)	0.0227 (15)	0.0271 (15)	0.0116 (13)	0.0016 (12)	0.0014 (12)
C3	0.0274 (17)	0.0235 (17)	0.0334 (17)	0.0122 (14)	−0.0049 (13)	0.0001 (13)
C2	0.0228 (15)	0.0236 (16)	0.0241 (15)	0.0111 (13)	0.0019 (12)	0.0005 (12)

Geometric parameters (Å, º) top

Ho1—O1	2.371 (2)	Ho1—O3ⁱⁱ	2.385 (2)
Ho1—O1ⁱ	2.371 (2)	O1—C1	1.276 (4)
Ho1—O1ⁱⁱ	2.371 (2)	O2—C2	1.274 (3)
Ho1—O2	2.463 (2)	C1—C3	1.385 (4)
Ho1—O2ⁱ	2.4625 (19)	C1—C2	1.529 (6)
Ho1—O2ⁱⁱ	2.463 (3)	C3—C2ⁱⁱⁱ	1.398 (5)
Ho1—O3	2.385 (3)	C3—H3	0.950
Ho1—O3ⁱ	2.385 (3)

Ho1···C1	3.253 (3)	O6···C1	3.444 (5)
Ho1···C1ⁱ	3.253 (3)	O6···C1ⁱⁱ	3.369 (4)
Ho1···C1ⁱⁱ	3.253 (4)	O6···C3	3.485 (5)
Ho1···C2	3.289 (3)	O6···C3^xi	3.326 (5)
Ho1···C2ⁱ	3.289 (2)	C1···Ho1	3.253 (3)
Ho1···C2ⁱⁱ	3.289 (4)	C1···O1ⁱ	3.592 (3)
O1···O1ⁱ	2.986 (3)	C1···O2	2.372 (4)
O1···O1ⁱⁱ	2.986 (3)	C1···O3ⁱⁱ	3.481 (4)
O1···O2	2.599 (4)	C1···O6	3.444 (5)
O1···O2ⁱⁱ	2.770 (4)	C1···O6ⁱ	3.369 (4)
O1···O3ⁱⁱ	3.214 (3)	C1···C1ⁱⁱⁱ	2.847 (5)
O1···O4^iv	3.464 (4)	C1···C3ⁱⁱⁱ	2.533 (6)
O1···O6	2.740 (4)	C1···C2ⁱⁱⁱ	2.406 (4)
O1···O6ⁱ	3.390 (4)	C3···O1	2.363 (3)
O1···C1ⁱⁱ	3.592 (5)	C3···O2ⁱⁱⁱ	2.370 (4)
O1···C3	2.363 (3)	C3···O6	3.485 (5)
O1···C2	2.360 (5)	C3···O6^xii	3.326 (4)
O1···C2ⁱⁱ	3.458 (5)	C3···C1ⁱⁱⁱ	2.533 (6)
O2···O1	2.599 (4)	C3···C3ⁱⁱⁱ	2.927 (6)
O2···O1ⁱ	2.770 (3)	C3···C2	2.531 (5)
O2···O3	2.778 (3)	C2···Ho1	3.289 (3)
O2···O3ⁱⁱ	2.734 (4)	C2···O1	2.360 (5)
O2···O4^v	2.868 (5)	C2···O1ⁱ	3.458 (3)
O2···O5ⁱⁱ	3.325 (4)	C2···O3ⁱⁱ	3.254 (5)
O2···C1	2.372 (4)	C2···O4^v	3.499 (5)
O2···C3ⁱⁱⁱ	2.370 (4)	C2···C1ⁱⁱⁱ	2.406 (4)
O3···O1ⁱ	3.214 (3)	C2···C3	2.531 (5)
O3···O2	2.778 (3)	C2···C2ⁱⁱⁱ	2.855 (4)
O3···O2ⁱ	2.734 (3)	O1···H3	2.608
O3···O3ⁱ	3.088 (5)	O2···H3ⁱⁱⁱ	2.614
O3···O3ⁱⁱ	3.088 (4)	O4···H3^ix	3.259
O3···O4	2.757 (5)	O4···H3^vi	3.484
O3···O5	2.772 (3)	O5···H3^ix	3.135
O3···C1ⁱ	3.481 (4)	O6···H3	2.918
O3···C2ⁱ	3.254 (3)	O6···H3^xi	3.032
O4···O1^vi	3.464 (5)	C1···H3	2.035
O4···O2^v	2.868 (5)	C1···H3ⁱⁱⁱ	3.400
O4···O3	2.757 (5)	C2···H3	3.396
O4···O5ⁱⁱ	2.753 (4)	C2···H3ⁱⁱⁱ	2.048
O4···O5^vii	2.802 (4)	H3···O1	2.608
O4···C2^v	3.499 (5)	H3···O2ⁱⁱⁱ	2.614
O5···O2ⁱ	3.325 (4)	H3···O4^x	3.259
O5···O3	2.772 (3)	H3···O4^iv	3.484
O5···O4ⁱ	2.753 (6)	H3···O5^x	3.135
O5···O4^viii	2.802 (4)	H3···O6	2.918
O5···O6^ix	2.728 (4)	H3···O6^xii	3.032
O6···O1	2.740 (4)	H3···C1	2.035
O6···O1ⁱⁱ	3.390 (3)	H3···C1ⁱⁱⁱ	3.400
O6···O5^x	2.728 (4)	H3···C2	3.396
O6···O6^xi	2.801 (4)	H3···C2ⁱⁱⁱ	2.048
O6···O6^xii	2.801 (5)

O1—Ho1—O1ⁱ	78.04 (8)	O2—Ho1—O3ⁱ	140.07 (9)
O1—Ho1—O1ⁱⁱ	78.04 (8)	O2—Ho1—O3ⁱⁱ	68.65 (10)
O1—Ho1—O2	65.01 (9)	O2ⁱ—Ho1—O2ⁱⁱ	119.91 (9)
O1—Ho1—O2ⁱ	134.81 (7)	O2ⁱ—Ho1—O3	68.65 (8)
O1—Ho1—O2ⁱⁱ	69.90 (9)	O2ⁱ—Ho1—O3ⁱ	69.92 (8)
O1—Ho1—O3	134.88 (10)	O2ⁱ—Ho1—O3ⁱⁱ	140.07 (8)
O1—Ho1—O3ⁱ	138.54 (11)	O2ⁱⁱ—Ho1—O3	140.07 (9)
O1—Ho1—O3ⁱⁱ	85.02 (8)	O2ⁱⁱ—Ho1—O3ⁱ	68.65 (9)
O1ⁱ—Ho1—O1ⁱⁱ	78.04 (10)	O2ⁱⁱ—Ho1—O3ⁱⁱ	69.92 (10)
O1ⁱ—Ho1—O2	69.90 (8)	O3—Ho1—O3ⁱ	80.68 (11)
O1ⁱ—Ho1—O2ⁱ	65.01 (8)	O3—Ho1—O3ⁱⁱ	80.68 (9)
O1ⁱ—Ho1—O2ⁱⁱ	134.81 (8)	O3ⁱ—Ho1—O3ⁱⁱ	80.68 (9)
O1ⁱ—Ho1—O3	85.02 (10)	Ho1—O1—C1	123.4 (2)
O1ⁱ—Ho1—O3ⁱ	134.88 (7)	Ho1—O2—C2	119.9 (2)
O1ⁱ—Ho1—O3ⁱⁱ	138.54 (10)	O1—C1—C3	125.2 (4)
O1ⁱⁱ—Ho1—O2	134.81 (8)	O1—C1—C2	114.3 (2)
O1ⁱⁱ—Ho1—O2ⁱ	69.90 (8)	C3—C1—C2	120.5 (3)
O1ⁱⁱ—Ho1—O2ⁱⁱ	65.01 (8)	C1—C3—C2ⁱⁱⁱ	119.7 (4)
O1ⁱⁱ—Ho1—O3	138.54 (7)	O2—C2—C1	115.3 (3)
O1ⁱⁱ—Ho1—O3ⁱ	85.02 (9)	O2—C2—C3ⁱⁱⁱ	124.9 (3)
O1ⁱⁱ—Ho1—O3ⁱⁱ	134.88 (11)	C1—C2—C3ⁱⁱⁱ	119.8 (2)
O2—Ho1—O2ⁱ	119.91 (9)	C1—C3—H3	120.2
O2—Ho1—O2ⁱⁱ	119.91 (7)	C2ⁱⁱⁱ—C3—H3	120.2
O2—Ho1—O3	69.92 (9)

O1—Ho1—O1ⁱ—C1ⁱ	166.8 (3)	O3—Ho1—O1ⁱⁱ—C1ⁱⁱ	−125.1 (2)
O1ⁱ—Ho1—O1—C1	86.7 (2)	O3ⁱ—Ho1—O1ⁱⁱ—C1ⁱⁱ	−55.3 (2)
O1—Ho1—O1ⁱⁱ—C1ⁱⁱ	86.7 (2)	O3ⁱⁱ—Ho1—O1ⁱⁱ—C1ⁱⁱ	16.3 (2)
O1ⁱⁱ—Ho1—O1—C1	166.8 (2)	O2—Ho1—O2ⁱ—C2ⁱ	34.3 (2)
O1—Ho1—O2—C2	−10.8 (2)	O2ⁱ—Ho1—O2—C2	−139.8 (2)
O2—Ho1—O1—C1	13.5 (2)	O2—Ho1—O2ⁱⁱ—C2ⁱⁱ	−139.8 (2)
O1—Ho1—O2ⁱ—C2ⁱ	−49.0 (3)	O2ⁱⁱ—Ho1—O2—C2	34.3 (2)
O2ⁱ—Ho1—O1—C1	121.7 (2)	O3—Ho1—O2—C2	171.3 (2)
O1—Ho1—O2ⁱⁱ—C2ⁱⁱ	−96.6 (2)	O3ⁱ—Ho1—O2—C2	126.2 (2)
O2ⁱⁱ—Ho1—O1—C1	−125.7 (2)	O3ⁱⁱ—Ho1—O2—C2	83.8 (2)
O3—Ho1—O1—C1	16.3 (3)	O2ⁱ—Ho1—O2ⁱⁱ—C2ⁱⁱ	34.3 (2)
O3ⁱ—Ho1—O1—C1	−125.1 (2)	O2ⁱⁱ—Ho1—O2ⁱ—C2ⁱ	−139.8 (2)
O3ⁱⁱ—Ho1—O1—C1	−55.3 (2)	O3—Ho1—O2ⁱ—C2ⁱ	83.8 (2)
O1ⁱ—Ho1—O1ⁱⁱ—C1ⁱⁱ	166.8 (2)	O3ⁱ—Ho1—O2ⁱ—C2ⁱ	171.3 (2)
O1ⁱⁱ—Ho1—O1ⁱ—C1ⁱ	86.7 (3)	O3ⁱⁱ—Ho1—O2ⁱ—C2ⁱ	126.2 (2)
O1ⁱ—Ho1—O2—C2	−96.6 (2)	O3—Ho1—O2ⁱⁱ—C2ⁱⁱ	126.2 (2)
O2—Ho1—O1ⁱ—C1ⁱ	−125.7 (3)	O3ⁱ—Ho1—O2ⁱⁱ—C2ⁱⁱ	83.8 (2)
O1ⁱ—Ho1—O2ⁱ—C2ⁱ	−10.8 (2)	O3ⁱⁱ—Ho1—O2ⁱⁱ—C2ⁱⁱ	171.3 (2)
O2ⁱ—Ho1—O1ⁱ—C1ⁱ	13.5 (3)	Ho1—O1—C1—C3	167.6 (2)
O1ⁱ—Ho1—O2ⁱⁱ—C2ⁱⁱ	−49.0 (2)	Ho1—O1—C1—C2	−14.4 (4)
O2ⁱⁱ—Ho1—O1ⁱ—C1ⁱ	121.7 (3)	Ho1—O2—C2—C1	8.1 (3)
O3—Ho1—O1ⁱ—C1ⁱ	−55.3 (3)	Ho1—O2—C2—C3ⁱⁱⁱ	−171.9 (2)
O3ⁱ—Ho1—O1ⁱ—C1ⁱ	16.3 (3)	O1—C1—C3—C2ⁱⁱⁱ	176.2 (3)
O3ⁱⁱ—Ho1—O1ⁱ—C1ⁱ	−125.1 (3)	O1—C1—C2—O2	3.4 (4)
O1ⁱⁱ—Ho1—O2—C2	−49.0 (2)	O1—C1—C2—C3ⁱⁱⁱ	−176.5 (3)
O2—Ho1—O1ⁱⁱ—C1ⁱⁱ	121.7 (2)	C3—C1—C2—O2	−178.4 (3)
O1ⁱⁱ—Ho1—O2ⁱ—C2ⁱ	−96.6 (2)	C3—C1—C2—C3ⁱⁱⁱ	1.7 (5)
O2ⁱ—Ho1—O1ⁱⁱ—C1ⁱⁱ	−125.7 (2)	C2—C1—C3—C2ⁱⁱⁱ	−1.7 (5)
O1ⁱⁱ—Ho1—O2ⁱⁱ—C2ⁱⁱ	−10.8 (2)	C1—C3—C2ⁱⁱⁱ—O2ⁱⁱⁱ	−178.5 (3)
O2ⁱⁱ—Ho1—O1ⁱⁱ—C1ⁱⁱ	13.5 (2)	C1—C3—C2ⁱⁱⁱ—C1ⁱⁱⁱ	1.6 (5)

Symmetry codes: (i) −y, x−y, z; (ii) −x+y, −x, z; (iii) −x−1/3, −y−2/3, −z+4/3; (iv) x−y−2/3, x−1/3, −z+5/3; (v) −x+1/3, −y−1/3, −z+5/3; (vi) y+1/3, −x+y−1/3, −z+5/3; (vii) y, −x+y, −z+2; (viii) x−y, x, −z+2; (ix) x+2/3, y+1/3, z+1/3; (x) x−2/3, y−1/3, z−1/3; (xi) y, −x+y, −z+1; (xii) x−y, x, −z+1.

Experimental details

Crystal data
Chemical formula	[Ho₂(C₆H₂O₄)₃(H₂O)₆]·18H₂O
M_r	1176.46
Crystal system, space group	Trigonal, R3
Temperature (K)	90
a, c (Å)	14.1407 (3), 18.0629 (5)
V (Å³)	3127.93 (12)
Z	3
Radiation type	Mo Kα
µ (mm⁻¹)	3.88
Crystal size (mm)	0.10 × 0.10 × 0.04

Data collection
Diffractometer	Rigaku R-AXIS RAPID diffractometer
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995)
T_min, T_max	0.704, 0.856
No. of measured, independent and observed [F² > 2σ(F²)] reflections	11262, 1594, 1525
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.063, 1.23
No. of reflections	1594
No. of parameters	86
No. of restraints	?
H-atom treatment	H-atom parameters constrained
	w = 1/[σ²(F_o²) + (0.0248P)² + 19.995P] where P = (F_o² + 2F_c²)/3
Δρ_max, Δρ_min (e Å⁻³)	0.65, −0.30

Computer programs: PROCESS-AUTO (Rigaku, 1998), CrystalStructure (Rigaku, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and pyMOL (DeLano, 2007).

Selected bond lengths (Å) top

Ho1—O1	2.371 (2)	Ho1—O3	2.385 (3)
Ho1—O2	2.463 (2)

Acknowledgements

We are thankful for a Grant-in-Aid for Young Scientists (S) from JSPS, the Global COE Program, "Chemistry Innovation through Cooperation of Science and Engineering" from MEXT Japan, the Photon Frontier Network Program from MEXT, the Izumi Science and Technology Foundation and Asahi Glass Foundation. We also thank the Cryogenic Research Center and the Center for Nano Lithography & Analysis, The University of Tokyo, supported by MEXT Japan. This work has been approved by the Photon Factory Program Advisory Committee (Proposal 2009 G678).

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