Synthesis and crystal structure of Sr2Cu(OH)4[B(OH)4]2

Kunisawa, H.; Yamaura, J.; Nomura, T.

doi:10.1107/S2056989025011491

research communications

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 82| Part 1| January 2026| Pages 103-106

https://doi.org/10.1107/S2056989025011491

Open

access

Synthesis and crystal structure of Sr₂Cu(OH)₄[B(OH)₄]₂

Hibiki Kunisawa,^a Jun-ichi Yamaura ^b and Toshihiro Nomura ^a ^*

^aDepartment of Physics, Shizuoka University, Shizuoka 422-8529, Japan, and ^bInstitute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
^*Correspondence e-mail: [email protected]

Edited by M. Weil, Vienna University of Technology, Austria (Received 9 December 2025; accepted 20 December 2025; online 1 January 2026)

Single crystals of distrontium copper(II) tetrahydroxide bis(tetrahydroxidoborate), Sr₂Cu(OH)₄[B(OH)₄]₂, were obtained by an ammonia evaporation method at room temperature. The compound crystallizes in the triclinic system, space group P1, and is isotypic with the calcium analogue henmilite, Ca₂Cu(OH)₄[B(OH)₄]₂. The {Cu(OH)₄} units form a deformed square lattice in the ac plane, giving rise to a quasi-two-dimensional arrangement of Cu^II ions. An intricate network of O—H⋯O hydrogen bonds of medium strengths with the [B(OH)₄] units as the primary donor groups consolidate the framework structure.

Keywords: crystal structure; inorganic; hydroxyborate.

CCDC reference: 2517776

1. Chemical context

Hydroxidoborates containing Cu^II ions are of interest owing to their structural diversity and potential magnetic frustration. Among them is the mineral henmilite, Ca₂Cu(OH)₄[B(OH)₄]₂ (space group P $[\overline{1}]$ ) (Nakai et al., 1986 ; Nakai, 1986 ; Petrov, 2016 ), that exhibits a layered framework where {Cu(OH)₄} units form a quasi two-dimensional spin system (Yamamoto et al., 2021 ; Hayashi et al., 2023 ). Some basic properties of henmilite are reported elsewhere (Kusachi, 1992 ; Frost & Xi, 2013 ). Yamamoto et al. proposed the doubled unit cell containing two Cu^II ions compared to the original report by Nakai (a′ = 2a, b′ = b, c′ = c), suggesting an alternating Cu⋯Cu distance along the a axis. Thus, the exchange parameters are also alternatively modulated, and the system can be regarded as a coupled two-leg spin ladder (Yamamoto et al., 2021). The antiferromagnetic ordering temperature is reported to be approximately 0.2 K at zero magnetic fields.

In the present study, we have synthesized the strontium analogue, Sr₂Cu(OH)₄[B(OH)₄]₂, by an ammonia evaporation method at room temperature and report here its crystal structure.

2. Structural commentary

Sr₂Cu(OH)₄[B(OH)₄]₂ crystallizes in space group P $[\overline{1}]$ (Figs. 1 and 2) and is isotypic with henmilite. The mineral was described using a non-standard settings both for the basis cell (Nakai et al., 1986; Nakai, 1986) and for the doubled unit cell (Yamamoto et al., 2021). The current description of the Sr isotype uses the standard setting with the transformation of a′′ = c′, b′′ = b′, c′′ = a′, where the single primed parameters relate to the doubled unit cell reported by Yamamoto et al. (2021). We note that the crystal structure of the title compound is also doubled as clearly demonstrated by the superlattice reflections shown in Fig. 1.

Figure 1
Reconstructed precession image of the (h0l) plane, showing weak superstructure reflections at odd l positions (corresponding to half-integer l in the halved cell), consistent with a doubling of the unit cell along the c direction.

Figure 2
A view of the asymmetric unit of Sr₂Cu(OH)₄[B(OH)₄]₂. Displacement ellipsoids are drawn at the 50% probability level.

The crystal structure is composed of square-planar {Cu(OH)₄} units, {Sr(OH)₈} polyhedra, and tetrahedral [B(OH)₄] units (Fig. 2). The {Sr(OH)₈} polyhedra centred by the Sr1 and Sr2 sites are close to square antiprisms, but are notably distorted in the triclinic lattice. The edge-sharing {Sr(OH)₈} units form chains extending parallel to [110], which are interconnected by {Cu(OH)₄} and [B(OH)₄] units into a framework structure (Fig. 3). As a result, Cu^II ions form a quasi two-dimensional system in the ac plane arranged in a deformed square lattice. The nearest-neighbour distance between Cu^II ions is 5.84880 (11) Å along the a axis. Along the c axis, the Cu⋯Cu distances alternate between 5.8959 (5) Å and 5.9681 (5) Å.

Figure 3
Crystal structure of Sr₂Cu(OH)₄[B(OH)₄]₂.

3. Supramolecular features

In the three-dimensional hydrogen-bonding network of Sr₂Cu(OH)₄[B(OH)₄]₂, tetrahedral [B(OH)₄] units play a central role (Table 1, Fig. 4). The [B1(OH)₄] tetrahedron donates via atoms H1–H4 and accepts via O1 and O3 atoms, while the [B2(OH)₄] tetrahedron donates via atoms H5–H7 and accepts via O5, O7, and O8 with surrounding [B(OH)₄] tetrahedra and {Cu(OH)₄} plaquettes. The hydrogen-bonding distances of 2.35 Å at O8—H8⋯O12 and 2.39 Å O12—H12⋯O10 are relatively long and omitted in Fig. 4. The hydrogen-bonding network is topologically identical in henmilite and the title compound.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O12ⁱ	0.81 (3)	2.10 (3)	2.886 (2)	164 (3)
O2—H2⋯O3ⁱⁱ	0.77 (3)	2.07 (3)	2.8060 (18)	162 (3)
O3—H3⋯O5ⁱⁱⁱ	0.82 (2)	2.07 (2)	2.8563 (19)	163 (2)
O4—H4⋯O8^iv	0.89 (2)	1.93 (2)	2.8125 (18)	176 (2)
O5—H5⋯O10^v	0.81 (3)	2.01 (3)	2.7961 (19)	163 (3)
O6—H6⋯O7^vi	0.79 (3)	2.05 (3)	2.8129 (18)	162 (3)
O7—H7⋯O1^vii	0.78 (2)	2.10 (2)	2.8592 (19)	166 (2)
O8—H8⋯O12^viii	0.74 (3)	2.35 (3)	3.073 (2)	166 (3)
O12—H12⋯O10^ix	0.72 (3)	2.39 (3)	3.1076 (19)	171 (3)
Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) ; (ix) .

Figure 4
Hydrogen-bonding network in Sr₂Cu(OH)₄[B(OH)₄]₂ in different views (a) and (b). Sr^II ions are omitted for clarity. [Symmetry codes: (i) −x + 1, −y + 1, −z + 1; (ii) x + 1, y, z + 1; (iii) x − 1, y + 1, z; (iv) −x + 2, −y + 1, −z + 1; (v) −x + 1, −y + 2, −z; (vi) −x, −y + 1, −z; (vii) −x + 2, −y, −z + 1; (viii) x − 1, y, z; (ix) x + 1, y − 1, z + 1; (x) −x + 1, −y + 2, −z; (xi) x + 2, y, z; (xii) x + 1, y + 1, z.]

We note that the hydrogen atoms H9, H10, and H11 of the {Cu(OH)₄} unit are not involved in notable hydrogen-bonding interactions with the surrounding [B(OH)₄] and {Cu(OH)₄} units. A similar situation is observed in henmilite, where the hydrogen bonds donated by the{Cu(OH)₄} unit are relatively long (two of them exceed 2.4 Å). In the title compound, the larger unit-cell volume (by 9.4%) results in increased intermolecular separations, and consequently such hydrogen bonds are absent.

4. Database survey

According to the Inorganic Crystal Structure Database (ICSD (version 2025-1), FIZ Karlsruhe; Zagorac et al., 2019 ), no hydroxidoborates containing Cu^II and alkaline-earth metal ions have been reported, except for henmilite. Based on the layered structure, Sr₂Cu(OH)₄[B(OH)₄]₂ is also expected to show features of a low-dimensional spin system. Due to the larger ionic radius of Sr^II, Cu⋯Cu distances in Sr₂Cu(OH)₄[B(OH)₄]₂ are longer than those in henmilite as summarized in Fig. 5. This indicates that the exchange interaction in Sr₂Cu(OH)₄[B(OH)₄]₂ is weaker than in henmilite, and hence, the ordering temperature is expected to be even lower than 0.2 K.

Figure 5
Cu sublattice in Sr₂Cu(OH)₄[B(OH)₄]₂ with Cu⋯Cu distances. Values in parentheses are the corresponding distances in Ca₂Cu(OH)₄[B(OH)₄]₂ (Yamamoto et al., 2021

). The crystallographic axes and unit cell are drawn for Sr₂Cu(OH)₄[B(OH)₄]₂.

5. Synthesis and crystallization

Single crystals were grown by slow ammonia evaporation at room temperature. A mixture of CuCO₃·Cu(OH)₂ (0.1 g), H₃BO₃ (0.2 g), and Sr(OH)₂·8H₂O (1.6 g) was dissolved in 20 ml of 5%_wt aqueous ammonia. All reagents were purchased from FUJIFILM Wako and used as received. The beaker was placed in a sealed container at room temperature together with 6%_wt nitric acid to control the evaporation rate. After 1–2 weeks, violet–blue rhombic crystals were obtained. We picked a 30 × 30 × 10 µm³ single crystal and performed the XRD at room temperature. We note that a powder sample of henmilite can also be obtained in a similar method, starting from Ca(OH)₂ instead of Sr(OH)₂·8H₂O.

6. Refinement

The crystallographic data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were located from difference syntheses. Refinement trials were carried out with both AFIX and DFIX restraints (Sheldrick, 2015 ) on hydrogen atoms. The AFIX-based model converged with R₁ = 0.0203, but yielded unrealistic O—H geometries. Therefore, all O—H distances were restrained to 0.82 (5) Å using DFIX, giving a final R₁ = 0.0178.

Table 2
Experimental details

Crystal data
Chemical formula	Sr₂Cu(OH)₄[B(OH)₄]₂
M_r	464.51
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	293
a, b, c (Å)	5.8488 (1), 8.2051 (2), 11.8619 (3)
α, β, γ (°)	83.789 (2), 87.614 (2), 70.499 (2)
V (Å³)	533.44 (2)
Z	2
Radiation type	Cu Kα
μ (mm⁻¹)	15.83
Crystal size (mm)	0.03 × 0.03 × 0.01

Data collection
Diffractometer	Four-circle diffractometer
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2023 )
T_min, T_max	0.763, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	6151, 2224, 1927
R_int	0.014
(sin θ/λ)_max (Å⁻¹)	0.635

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.018, 0.055, 1.09
No. of reflections	2224
No. of parameters	203
No. of restraints	12
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.41, −0.60
Computer programs: CrysAlis PRO (Rigaku OD, 2023), OLEX2.solve (Bourhis et al., 2015 ), SHELXL (Sheldrick, 2015), VESTA 3 (Momma & Izumi, 2011 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2517776

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989025011491/wm5783sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989025011491/wm5783Isup3.hkl

checkCIF report

Computing details top

Strontium copper(II) tetrahydroxide bis(tetrahydroxyborate) top

Crystal data top

Sr₂Cu(OH)₄[B(OH)₄]₂	Z = 2
M_r = 464.51	F(000) = 446
Triclinic, P1	D_x = 2.892 Mg m⁻³
a = 5.8488 (1) Å	Cu Kα radiation, λ = 1.54184 Å
b = 8.2051 (2) Å	Cell parameters from 3611 reflections
c = 11.8619 (3) Å	θ = 5.7–77.7°
α = 83.789 (2)°	µ = 15.83 mm⁻¹
β = 87.614 (2)°	T = 293 K
γ = 70.499 (2)°	Plate, translucent, blue-violet
V = 533.44 (2) Å³	0.03 × 0.03 × 0.01 mm

Data collection top

Four-circle diffractometer	R_int = 0.014
Radiation source: Rotating-anode X-ray tube	θ_max = 78.1°, θ_min = 3.8°
ω scans	h = −6→7
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2023)	k = −10→10
T_min = 0.763, T_max = 1.000	l = −13→14
6151 measured reflections	Standard reflections: not measured; every not measured reflections
2224 independent reflections	intensity decay: not measured
1927 reflections with I > 2σ(I)

Refinement top

Refinement on F²	Hydrogen site location: difference Fourier map
Least-squares matrix: full	All H-atom parameters refined
R[F² > 2σ(F²)] = 0.018	w = 1/[σ²(F_o²) + (0.036P)² + 0.0131P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.055	(Δ/σ)_max = 0.001
S = 1.09	Δρ_max = 0.41 e Å⁻³
2224 reflections	Δρ_min = −0.60 e Å⁻³
203 parameters	Extinction correction: SHELXL-2019/2 (Sheldrick 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
12 restraints	Extinction coefficient: 0.00104 (13)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	U_iso*/U_eq
Sr1	0.26270 (2)	0.74355 (2)	0.00346 (2)	0.01241 (9)
Sr2	0.72436 (3)	0.25409 (2)	0.49668 (2)	0.01266 (9)
Cu	0.49102 (3)	0.49916 (3)	0.25177 (2)	0.01478 (10)
B1	−0.2578 (4)	0.9087 (3)	−0.11486 (17)	0.0133 (4)
B2	1.2500 (4)	0.0957 (3)	0.61569 (17)	0.0138 (4)
O1	−0.4028 (2)	0.79592 (18)	−0.13154 (11)	0.0159 (3)
O2	−0.1918 (2)	0.89861 (17)	0.00634 (11)	0.0157 (3)
O3	−0.4046 (2)	1.09031 (16)	−0.14559 (11)	0.0153 (3)
O4	−0.0262 (2)	0.85237 (17)	−0.17663 (11)	0.0166 (3)
O5	1.3820 (2)	0.21430 (18)	0.63596 (12)	0.0168 (3)
O6	1.1846 (2)	0.10388 (17)	0.49505 (11)	0.0161 (3)
O7	1.4086 (2)	−0.08390 (16)	0.64487 (12)	0.0160 (3)
O8	1.0151 (2)	0.13438 (17)	0.67660 (11)	0.0166 (3)
O9	0.3483 (2)	0.47831 (17)	0.40103 (11)	0.0166 (3)
O10	0.8087 (2)	0.43586 (17)	0.32424 (12)	0.0177 (3)
O11	0.6323 (2)	0.52314 (16)	0.10290 (11)	0.0161 (3)
O12	0.1793 (2)	0.56215 (19)	0.17586 (13)	0.0220 (3)
H1	−0.320 (5)	0.695 (4)	−0.135 (3)	0.032 (7)*
H2	−0.290 (5)	0.879 (4)	0.045 (2)	0.026 (7)*
H3	−0.435 (4)	1.117 (3)	−0.213 (2)	0.019 (6)*
H4	−0.009 (3)	0.938 (3)	−0.225 (2)	0.017 (5)*
H5	1.300 (5)	0.315 (4)	0.642 (3)	0.038 (8)*
H6	1.284 (5)	0.121 (4)	0.453 (3)	0.037 (8)*
H7	1.436 (4)	−0.109 (3)	0.709 (2)	0.012 (6)*
H8	0.991 (4)	0.201 (4)	0.717 (2)	0.033 (7)*
H9	0.232 (4)	0.453 (4)	0.399 (2)	0.017 (6)*
H10	0.891 (4)	0.372 (4)	0.286 (2)	0.031 (7)*
H11	0.756 (4)	0.548 (4)	0.108 (2)	0.019 (7)*
H12	0.089 (4)	0.543 (4)	0.213 (2)	0.030 (7)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sr1	0.01143 (11)	0.01167 (12)	0.01307 (12)	−0.00243 (7)	−0.00086 (7)	−0.00093 (7)
Sr2	0.01190 (11)	0.01148 (12)	0.01352 (12)	−0.00246 (7)	−0.00113 (7)	−0.00087 (7)
Cu	0.01638 (18)	0.01437 (17)	0.01296 (18)	−0.00402 (13)	−0.00138 (13)	−0.00159 (12)
B1	0.0125 (9)	0.0130 (9)	0.0143 (10)	−0.0042 (7)	−0.0006 (7)	−0.0008 (7)
B2	0.0146 (9)	0.0134 (9)	0.0130 (10)	−0.0045 (7)	−0.0009 (7)	−0.0004 (7)
O1	0.0142 (6)	0.0138 (6)	0.0202 (7)	−0.0051 (5)	0.0012 (4)	−0.0032 (5)
O2	0.0122 (5)	0.0221 (6)	0.0122 (6)	−0.0053 (5)	0.0003 (5)	−0.0005 (5)
O3	0.0167 (6)	0.0118 (6)	0.0149 (7)	−0.0013 (5)	−0.0025 (5)	−0.0002 (5)
O4	0.0139 (5)	0.0161 (6)	0.0172 (6)	−0.0025 (4)	0.0035 (4)	0.0005 (5)
O5	0.0160 (6)	0.0143 (6)	0.0210 (7)	−0.0061 (5)	0.0005 (5)	−0.0028 (5)
O6	0.0132 (6)	0.0221 (6)	0.0127 (6)	−0.0058 (5)	−0.0004 (4)	−0.0002 (5)
O7	0.0172 (6)	0.0132 (6)	0.0144 (7)	−0.0007 (5)	−0.0033 (5)	−0.0007 (5)
O8	0.0148 (6)	0.0180 (6)	0.0167 (7)	−0.0048 (5)	0.0033 (5)	−0.0039 (5)
O9	0.0167 (6)	0.0173 (6)	0.0149 (7)	−0.0041 (5)	0.0004 (5)	−0.0031 (5)
O10	0.0171 (6)	0.0185 (6)	0.0170 (7)	−0.0051 (5)	−0.0007 (5)	−0.0019 (5)
O11	0.0169 (6)	0.0157 (6)	0.0145 (7)	−0.0035 (5)	−0.0006 (5)	−0.0026 (5)
O12	0.0183 (6)	0.0297 (7)	0.0192 (7)	−0.0114 (6)	−0.0034 (5)	0.0044 (6)

Geometric parameters (Å, º) top

Sr1—Cu	3.4266 (3)	Cu—O9	1.9410 (13)
Sr1—Cuⁱ	3.7726 (3)	Cu—O10	1.9630 (13)
Sr1—B1ⁱⁱ	3.263 (2)	Cu—O11	1.9369 (13)
Sr1—B1	3.204 (2)	Cu—O12	1.9516 (13)
Sr1—O1ⁱⁱⁱ	2.5936 (13)	B1—O1	1.481 (2)
Sr1—O2	2.5358 (12)	B1—O2	1.491 (2)
Sr1—O2ⁱⁱ	2.8149 (13)	B1—O3	1.465 (2)
Sr1—O3ⁱⁱ	2.5996 (13)	B1—O4	1.469 (2)
Sr1—O4	2.6640 (13)	B2—O5	1.472 (2)
Sr1—O11ⁱ	2.5285 (12)	B2—O6	1.485 (2)
Sr1—O11	2.5448 (13)	B2—O7	1.469 (2)
Sr1—O12	2.5255 (15)	B2—O8	1.479 (2)
Sr2—Cu	3.4028 (3)	O1—H1	0.82 (3)
Sr2—Cu^iv	3.7257 (3)	O2—H2	0.77 (3)
Sr2—B2	3.230 (2)	O3—H3	0.82 (2)
Sr2—B2^v	3.250 (2)	O4—H4	0.89 (3)
Sr2—O5^vi	2.6250 (13)	O5—H5	0.82 (3)
Sr2—O6^v	2.7961 (13)	O6—H6	0.79 (3)
Sr2—O6	2.5595 (12)	O7—H7	0.78 (2)
Sr2—O7^v	2.5914 (13)	O8—H8	0.73 (3)
Sr2—O8	2.6730 (13)	O9—H9	0.78 (2)
Sr2—O9	2.5620 (13)	O10—H10	0.75 (3)
Sr2—O9^iv	2.5267 (13)	O11—H11	0.82 (2)
Sr2—O10	2.5296 (14)	O12—H12	0.72 (3)
Sr2—H10	2.83 (3)

Cu—Sr1—Cuⁱ	111.901 (5)	O9^iv—Sr2—O7^v	151.18 (4)
B1ⁱⁱ—Sr1—Cuⁱ	140.29 (4)	O9—Sr2—O7^v	75.86 (4)
B1—Sr1—Cuⁱ	90.00 (4)	O9^iv—Sr2—O8	76.98 (4)
B1—Sr1—Cu	136.70 (4)	O9—Sr2—O8	150.04 (4)
B1ⁱⁱ—Sr1—Cu	89.41 (4)	O9^iv—Sr2—O9	75.64 (5)
B1—Sr1—B1ⁱⁱ	96.70 (5)	O9^iv—Sr2—O10	85.48 (4)
O1ⁱⁱⁱ—Sr1—Cuⁱ	55.25 (3)	O9^iv—Sr2—H10	98.9 (6)
O1ⁱⁱⁱ—Sr1—Cu	112.83 (3)	O9—Sr2—H10	74.6 (5)
O1ⁱⁱⁱ—Sr1—B1	110.35 (5)	O10—Sr2—Cu^iv	113.76 (3)
O1ⁱⁱⁱ—Sr1—B1ⁱⁱ	86.00 (4)	O10—Sr2—Cu	34.87 (3)
O1ⁱⁱⁱ—Sr1—O2ⁱⁱ	74.11 (4)	O10—Sr2—B2^v	100.51 (5)
O1ⁱⁱⁱ—Sr1—O3ⁱⁱ	86.24 (4)	O10—Sr2—B2	102.07 (5)
O1ⁱⁱⁱ—Sr1—O4	85.65 (4)	O10—Sr2—O5^vi	143.85 (4)
O2—Sr1—Cu	114.33 (3)	O10—Sr2—O6^v	123.60 (4)
O2ⁱⁱ—Sr1—Cu	116.43 (3)	O10—Sr2—O6	83.73 (4)
O2ⁱⁱ—Sr1—Cuⁱ	119.92 (3)	O10—Sr2—O7^v	86.32 (4)
O2—Sr1—Cuⁱ	115.87 (3)	O10—Sr2—O8	124.66 (4)
O2—Sr1—B1	27.04 (5)	O10—Sr2—O9	64.78 (4)
O2ⁱⁱ—Sr1—B1ⁱⁱ	27.13 (4)	O10—Sr2—H10	14.8 (5)
O2ⁱⁱ—Sr1—B1	78.43 (4)	Sr1—Cu—Sr1ⁱ	68.098 (5)
O2—Sr1—B1ⁱⁱ	81.29 (5)	Sr1—Cu—Sr2^iv	112.094 (6)
O2—Sr1—O1ⁱⁱⁱ	130.80 (4)	Sr2—Cu—Sr1ⁱ	111.304 (6)
O2—Sr1—O2ⁱⁱ	73.23 (5)	Sr2—Cu—Sr1	179.289 (7)
O2—Sr1—O3ⁱⁱ	100.66 (4)	Sr2^iv—Cu—Sr1ⁱ	177.080 (7)
O2—Sr1—O4	53.81 (4)	Sr2—Cu—Sr2^iv	68.482 (6)
O2—Sr1—O11	147.73 (4)	O9—Cu—Sr1	132.38 (4)
O3ⁱⁱ—Sr1—Cuⁱ	138.39 (3)	O9—Cu—Sr1ⁱ	143.20 (4)
O3ⁱⁱ—Sr1—Cu	65.76 (3)	O9—Cu—Sr2^iv	38.85 (4)
O3ⁱⁱ—Sr1—B1	120.90 (4)	O9—Cu—Sr2	48.33 (4)
O3ⁱⁱ—Sr1—B1ⁱⁱ	25.91 (4)	O9—Cu—O10	88.64 (6)
O3ⁱⁱ—Sr1—O2ⁱⁱ	51.33 (4)	O9—Cu—O12	92.85 (6)
O3ⁱⁱ—Sr1—O4	132.21 (4)	O10—Cu—Sr1ⁱ	94.45 (4)
O4—Sr1—Cuⁱ	66.17 (3)	O10—Cu—Sr1	132.02 (4)
O4—Sr1—Cu	156.76 (3)	O10—Cu—Sr2	47.45 (4)
O4—Sr1—B1ⁱⁱ	106.49 (5)	O10—Cu—Sr2^iv	83.30 (4)
O4—Sr1—B1	27.04 (4)	O11—Cu—Sr1	47.21 (4)
O4—Sr1—O2ⁱⁱ	81.21 (4)	O11—Cu—Sr1ⁱ	37.52 (4)
O11—Sr1—Cuⁱ	84.18 (3)	O11—Cu—Sr2	132.08 (4)
O11ⁱ—Sr1—Cuⁱ	27.81 (3)	O11—Cu—Sr2^iv	140.44 (4)
O11—Sr1—Cu	33.96 (3)	O11—Cu—O9	179.26 (4)
O11ⁱ—Sr1—Cu	92.07 (3)	O11—Cu—O10	91.44 (6)
O11ⁱ—Sr1—B1ⁱⁱ	165.57 (5)	O11—Cu—O12	87.07 (6)
O11ⁱ—Sr1—B1	92.05 (5)	O12—Cu—Sr1	46.70 (4)
O11—Sr1—B1ⁱⁱ	99.45 (5)	O12—Cu—Sr1ⁱ	84.30 (4)
O11—Sr1—B1	160.81 (5)	O12—Cu—Sr2	133.81 (4)
O11—Sr1—O1ⁱⁱⁱ	81.18 (4)	O12—Cu—Sr2^iv	97.93 (4)
O11ⁱ—Sr1—O1ⁱⁱⁱ	80.19 (4)	O12—Cu—O10	178.50 (5)
O11ⁱ—Sr1—O2ⁱⁱ	147.20 (4)	Sr1—B1—Sr1ⁱⁱ	83.30 (5)
O11—Sr1—O2ⁱⁱ	120.24 (4)	O1—B1—Sr1ⁱⁱ	144.15 (11)
O11ⁱ—Sr1—O2	111.00 (4)	O1—B1—Sr1	119.69 (11)
O11—Sr1—O3ⁱⁱ	73.88 (4)	O1—B1—O2	112.02 (15)
O11ⁱ—Sr1—O3ⁱⁱ	147.00 (4)	O2—B1—Sr1	50.65 (8)
O11—Sr1—O4	149.93 (4)	O2—B1—Sr1ⁱⁱ	59.44 (8)
O11ⁱ—Sr1—O4	76.79 (4)	O3—B1—Sr1	130.66 (11)
O11ⁱ—Sr1—O11	74.40 (5)	O3—B1—Sr1ⁱⁱ	50.85 (8)
O12—Sr1—Cuⁱ	115.42 (3)	O3—B1—O1	109.14 (13)
O12—Sr1—Cu	34.22 (3)	O3—B1—O2	105.54 (14)
O12—Sr1—B1ⁱⁱ	101.14 (5)	O3—B1—O4	113.91 (15)
O12—Sr1—B1	102.96 (5)	O4—B1—Sr1	55.55 (8)
O12—Sr1—O1ⁱⁱⁱ	144.89 (4)	O4—B1—Sr1ⁱⁱ	105.08 (11)
O12—Sr1—O2ⁱⁱ	124.65 (4)	O4—B1—O1	110.63 (14)
O12—Sr1—O2	84.31 (4)	O4—B1—O2	105.51 (14)
O12—Sr1—O3ⁱⁱ	86.10 (4)	Sr2—B2—Sr2^v	83.90 (5)
O12—Sr1—O4	123.75 (4)	O5—B2—Sr2	118.97 (11)
O12—Sr1—O11ⁱ	87.98 (5)	O5—B2—Sr2^v	145.53 (12)
O12—Sr1—O11	63.78 (4)	O5—B2—O6	113.74 (15)
Cu—Sr2—Cu^iv	111.519 (5)	O5—B2—O8	112.96 (15)
Cu^iv—Sr2—H10	127.6 (6)	O6—B2—Sr2^v	59.15 (8)
Cu—Sr2—H10	41.1 (5)	O6—B2—Sr2	50.63 (8)
B2—Sr2—Cu^iv	87.47 (4)	O7—B2—Sr2	131.87 (11)
B2^v—Sr2—Cu	90.14 (4)	O7—B2—Sr2^v	51.02 (8)
B2^v—Sr2—Cu^iv	144.03 (4)	O7—B2—O5	108.75 (14)
B2—Sr2—Cu	136.64 (4)	O7—B2—O6	105.14 (14)
B2—Sr2—B2^v	96.10 (5)	O7—B2—O8	111.98 (15)
B2—Sr2—H10	96.2 (5)	O8—B2—Sr2	55.04 (8)
B2^v—Sr2—H10	87.7 (6)	O8—B2—Sr2^v	101.23 (10)
O5^vi—Sr2—Cu^iv	55.81 (3)	O8—B2—O6	104.01 (14)
O5^vi—Sr2—Cu	111.74 (3)	Sr1^vi—O1—H1	98 (2)
O5^vi—Sr2—B2	111.12 (5)	B1—O1—Sr1^vi	126.32 (10)
O5^vi—Sr2—B2^v	90.05 (4)	B1—O1—H1	113 (2)
O5^vi—Sr2—O6^v	78.53 (4)	Sr1—O2—Sr1ⁱⁱ	106.77 (5)
O5^vi—Sr2—O8	85.09 (4)	Sr1—O2—H2	130 (2)
O5^vi—Sr2—H10	152.7 (5)	Sr1ⁱⁱ—O2—H2	109 (2)
O6—Sr2—Cu^iv	112.65 (3)	B1—O2—Sr1ⁱⁱ	93.44 (10)
O6^v—Sr2—Cu	117.19 (3)	B1—O2—Sr1	102.31 (10)
O6^v—Sr2—Cu^iv	122.49 (3)	B1—O2—H2	109 (2)
O6—Sr2—Cu	114.91 (3)	Sr1ⁱⁱ—O3—H3	129.2 (18)
O6^v—Sr2—B2^v	27.13 (4)	B1—O3—Sr1ⁱⁱ	103.24 (10)
O6—Sr2—B2^v	80.59 (5)	B1—O3—H3	115.3 (18)
O6^v—Sr2—B2	77.68 (4)	Sr1—O4—H4	118.4 (13)
O6—Sr2—B2	26.66 (5)	B1—O4—Sr1	97.41 (10)
O6—Sr2—O5^vi	132.31 (4)	B1—O4—H4	111.2 (13)
O6—Sr2—O6^v	72.12 (4)	Sr2ⁱⁱⁱ—O5—H5	101 (2)
O6—Sr2—O7^v	100.74 (4)	B2—O5—Sr2ⁱⁱⁱ	121.20 (11)
O6—Sr2—O8	52.97 (4)	B2—O5—H5	116 (2)
O6—Sr2—O9	148.41 (4)	Sr2—O6—Sr2^v	107.88 (4)
O6^v—Sr2—H10	109.2 (6)	Sr2^v—O6—H6	104 (2)
O6—Sr2—H10	74.1 (5)	Sr2—O6—H6	130 (2)
O7^v—Sr2—Cu	66.56 (3)	B2—O6—Sr2^v	93.72 (10)
O7^v—Sr2—Cu^iv	142.15 (3)	B2—O6—Sr2	102.71 (10)
O7^v—Sr2—B2^v	26.14 (4)	B2—O6—H6	112 (2)
O7^v—Sr2—B2	120.76 (4)	Sr2^v—O7—H7	128.5 (18)
O7^v—Sr2—O5^vi	88.70 (4)	B2—O7—Sr2^v	102.84 (10)
O7^v—Sr2—O6^v	51.45 (4)	B2—O7—H7	114.7 (18)
O7^v—Sr2—O8	129.48 (4)	Sr2—O8—H8	110 (2)
O7^v—Sr2—H10	77.5 (5)	B2—O8—Sr2	98.00 (10)
O8—Sr2—Cu	158.47 (3)	B2—O8—H8	115.9 (19)
O8—Sr2—Cu^iv	66.01 (3)	Sr2^iv—O9—Sr2	104.36 (5)
O8—Sr2—B2	26.96 (4)	Sr2—O9—H9	118 (2)
O8—Sr2—B2^v	103.66 (5)	Sr2^iv—O9—H9	111.7 (19)
O8—Sr2—O6^v	78.24 (4)	Cu—O9—Sr2	97.21 (5)
O8—Sr2—H10	121.9 (5)	Cu—O9—Sr2^iv	112.35 (6)
O9^iv—Sr2—Cu^iv	28.81 (3)	Cu—O9—H9	112 (2)
O9^iv—Sr2—Cu	91.73 (3)	Sr2—O10—H10	106 (2)
O9—Sr2—Cu	34.46 (3)	Cu—O10—Sr2	97.68 (5)
O9—Sr2—Cu^iv	84.10 (3)	Cu—O10—H10	102.7 (19)
O9^iv—Sr2—B2	87.99 (5)	Sr1ⁱ—O11—Sr1	105.60 (5)
O9—Sr2—B2^v	101.76 (5)	Sr1—O11—H11	119.6 (19)
O9—Sr2—B2	159.41 (5)	Sr1ⁱ—O11—H11	107.9 (19)
O9^iv—Sr2—B2^v	171.84 (5)	Cu—O11—Sr1ⁱ	114.67 (6)
O9—Sr2—O5^vi	79.28 (4)	Cu—O11—Sr1	98.84 (5)
O9^iv—Sr2—O5^vi	81.88 (4)	Cu—O11—H11	110.3 (19)
O9^iv—Sr2—O6	105.75 (4)	Sr1—O12—H12	147 (2)
O9—Sr2—O6^v	122.57 (4)	Cu—O12—Sr1	99.08 (6)
O9^iv—Sr2—O6^v	149.49 (4)	Cu—O12—H12	112 (2)

Sr1—B1—O1—Sr1^vi	94.45 (11)	O3—B1—O2—Sr1ⁱⁱ	−22.29 (12)
Sr1ⁱⁱ—B1—O1—Sr1^vi	−29.6 (2)	O3—B1—O4—Sr1	124.07 (13)
Sr1—B1—O2—Sr1ⁱⁱ	108.00 (6)	O4—B1—O1—Sr1^vi	155.69 (11)
Sr1ⁱⁱ—B1—O2—Sr1	−108.00 (6)	O4—B1—O2—Sr1ⁱⁱ	98.62 (12)
Sr1—B1—O3—Sr1ⁱⁱ	−26.13 (15)	O4—B1—O2—Sr1	−9.38 (14)
Sr1ⁱⁱ—B1—O4—Sr1	70.64 (8)	O4—B1—O3—Sr1ⁱⁱ	−90.35 (14)
Sr2^v—B2—O5—Sr2ⁱⁱⁱ	27.9 (3)	O5—B2—O6—Sr2	−108.88 (13)
Sr2—B2—O5—Sr2ⁱⁱⁱ	−98.41 (11)	O5—B2—O6—Sr2^v	141.85 (13)
Sr2^v—B2—O6—Sr2	109.27 (6)	O5—B2—O7—Sr2^v	−147.70 (11)
Sr2—B2—O6—Sr2^v	−109.27 (6)	O5—B2—O8—Sr2	110.23 (13)
Sr2—B2—O7—Sr2^v	24.67 (16)	O6—B2—O5—Sr2ⁱⁱⁱ	−41.68 (19)
Sr2^v—B2—O8—Sr2	−74.28 (7)	O6—B2—O7—Sr2^v	−25.54 (14)
O1—B1—O2—Sr1ⁱⁱ	−140.94 (12)	O6—B2—O8—Sr2	−13.57 (13)
O1—B1—O2—Sr1	111.06 (12)	O7—B2—O5—Sr2ⁱⁱⁱ	75.10 (16)
O1—B1—O3—Sr1ⁱⁱ	145.47 (11)	O7—B2—O6—Sr2	132.25 (11)
O1—B1—O4—Sr1	−112.56 (12)	O7—B2—O6—Sr2^v	22.98 (12)
O2—B1—O1—Sr1^vi	38.27 (18)	O7—B2—O8—Sr2	−126.59 (13)
O2—B1—O3—Sr1ⁱⁱ	24.91 (14)	O8—B2—O5—Sr2ⁱⁱⁱ	−159.94 (11)
O2—B1—O4—Sr1	8.79 (13)	O8—B2—O6—Sr2^v	−94.86 (12)
O3—B1—O1—Sr1^vi	−78.22 (16)	O8—B2—O6—Sr2	14.41 (14)
O3—B1—O2—Sr1	−130.29 (11)	O8—B2—O7—Sr2^v	86.77 (14)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O12^vii	0.81 (3)	2.10 (3)	2.886 (2)	164 (3)
O2—H2···O3^viii	0.77 (3)	2.07 (3)	2.8060 (18)	162 (3)
O3—H3···O5^ix	0.82 (2)	2.07 (2)	2.8563 (19)	163 (2)
O4—H4···O8^x	0.89 (2)	1.93 (2)	2.8125 (18)	176 (2)
O5—H5···O10^xi	0.81 (3)	2.01 (3)	2.7961 (19)	163 (3)
O6—H6···O7^xii	0.79 (3)	2.05 (3)	2.8129 (18)	162 (3)
O7—H7···O1^xiii	0.78 (2)	2.10 (2)	2.8592 (19)	166 (2)
O8—H8···O12^iv	0.74 (3)	2.35 (3)	3.073 (2)	166 (3)
O12—H12···O10^vi	0.72 (3)	2.39 (3)	3.1076 (19)	171 (3)

Symmetry codes: (iv) −x+1, −y+1, −z+1; (vi) x−1, y, z; (vii) −x, −y+1, −z; (viii) −x−1, −y+2, −z; (ix) x−2, y+1, z−1; (x) x−1, y+1, z−1; (xi) −x+2, −y+1, −z+1; (xii) −x+3, −y, −z+1; (xiii) x+2, y−1, z+1.

Acknowledgements

The XRD experiment was performed as joint research at the Institute for Solid State Physics, UTokyo (Project No. 202410-MCBXG-0002) and using the Rigaku XtaLAB Synergy-R at the Molecular Structure Analysis Section, Shizuoka Instrumental Analysis Center, Shizuoka University.

Funding information

Funding for this research was provided by: JSPS KAKENHI (Nos. JP23H04861 and JP24K06944).

References

Bourhis, L. J., Dolomanov, O. V., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2015). Acta Cryst. A71, 59–75. Web of Science CrossRef IUCr Journals Google Scholar
Frost, R. L. & Xi, Y. (2013). Spectrochim. Acta A Mol. Biomol. Spectrosc. 103, 356–360. CrossRef CAS PubMed Google Scholar
Hayashi, K., Ishikawa, Y., Asano, T., Yamamoto, H., Kimura, H., Sakakura, T., Noda, Y., Fujii, Y. & Mitsudo, S. (2023). JPS Conf. Proc. 38, 011144. Google Scholar
Kusachi, I. (1992). Koubutsugaku Zasshi 21, 127–130. CAS Google Scholar
Momma, K. & Izumi, F. (2011). J. Appl. Cryst. 44, 1272–1276. Web of Science CrossRef CAS IUCr Journals Google Scholar
Nakai, I. (1986). Am. Mineral. 71, 1236–1239. CAS Google Scholar
Nakai, I., Okada, H., Masutomi, K., Koyama, E. & Nagashima, K. (1986). Am. Mineral. 71, 1234–1236. CAS Google Scholar
Petrov, A. (2016). Rocks & Minerals 91, 54–58. CrossRef Google Scholar
Rigaku OD (2023). CrysAlis PRO. Rigaku Oxford Diffraction Ltd, Yarnton, England. Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Yamamoto, H., Sakakura, T., Jeschke, H. O., Kabeya, N., Hayashi, K., Ishikawa, Y., Fujii, Y., Kishimoto, S., Sagayama, H., Shigematsu, K., Azuma, M., Ochiai, A., Noda, Y. & Kimura, H. (2021). Phys. Rev. Mater. 5, 104405. CrossRef Google Scholar
Zagorac, D., Müller, H., Ruehl, S., Zagorac, J. & Rehme, S. (2019). J. Appl. Cryst. 52, 918–925. Web of Science CrossRef CAS IUCr Journals Google Scholar