High-pressure sapphire capillary cell for synchrotron single-crystal X-ray diffraction measurements to 1500 bar

A new sapphire capillary pressure cell for single-crystal X-ray diffraction measurements at moderate pressures (200−1500 bar; 1 bar = 100 kPa) has been developed and optimized for use on beamline I19 at Diamond Light Source. The three-component cell permits optical centring of the crystal and in situ pressure modification to a precision of 1 bar. Compression of hexa­methyl­enetetramine and its deuterated analogue to 1000 bar was performed, showcasing the accuracy and precision of the measurements, and highlighting evidence of a geometric isotope effect.

Computing details

Program(s) used to solve structure: SHELXT (Sheldrick, 2015); program(s) used to refine structure: SHELXL 2018/3 (Sheldrick, 2015); molecular graphics: Olex2 1.3 (Dolomanov et al., 2009); software used to prepare material for publication: Olex2 1.3 (Dolomanov et al., 2009).

(I)

Crystal data

C6D12N4	Dx = 1.462 Mg m^−3
Mr = 152.27	Mo Kα radiation, λ = 0.71073 Å
Cubic, I43m	Cell parameters from 1376 reflections
a = 7.0195 (1) Å	θ = 4–29°
V = 345.88 (2) Å^3	µ = 0.09 mm^−1
Z = 2	T = 297 K
F(000) = 152	0.2 × 0.2 × 0.1 mm

Data collection

Area diffractometer	80 reflections with I > 2σ(I)
φ & ω scans	Rint = 0.015
Absorption correction: multi-scan SADABS (Siemens, 1996)	θmax = 26.2°, θmin = 5.8°
Tmin = 0.93, Tmax = 0.99	h = −6→8
1374 measured reflections	k = −8→8
83 independent reflections	l = −8→8

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0436P)^2 + 0.0602P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.031	(Δ/σ)max < 0.001
wR(F^2) = 0.093	Δρmax = 0.09 e Å^−3
S = 1.33	Δρmin = −0.15 e Å^−3
83 reflections	Absolute structure: Flack x determined using 30 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
8 parameters	Absolute structure parameter: 0.3 (7)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
N1	0.6224 (2)	0.6224 (2)	0.6224 (2)	0.0484 (11)
C2	0.7377 (4)	0.500000	0.500000	0.0539 (11)
D2A	0.819142	0.578960	0.421038	0.065*	0.5
D2B	0.819142	0.421038	0.578960	0.065*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0484 (11)	0.0484 (11)	0.0484 (11)	−0.0094 (8)	−0.0094 (8)	−0.0094 (8)
C2	0.0301 (14)	0.0659 (15)	0.0659 (15)	0.000	0.000	0.0020 (19)

Geometric parameters (Å, º)

N1—C2^i	1.460 (2)	C2—D2A	0.9700
N1—C2^ii	1.460 (2)	C2—D2B	0.9700
N1—C2	1.460 (2)
C2^i—N1—C2^ii	107.83 (16)	N1^iii—C2—D2A	109.1
C2^i—N1—C2	107.83 (16)	N1^iii—C2—D2B	109.1
C2^ii—N1—C2	107.83 (16)	N1—C2—D2B	109.1
N1^iii—C2—N1	112.7 (3)	D2A—C2—D2B	107.8
N1—C2—D2A	109.1
C2^i—N1—C2—N1^iii	−58.10 (17)	C2^ii—N1—C2—N1^iii	58.10 (17)

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