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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.

Supporting information


Crystallographic Information File (CIF)
Contains datablock I


Structure factor file (CIF format)
Contains datablock I


Portable Document Format (PDF) file
Supporting figures and tables

CCDC reference: 2008808

Computing details top

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) top
Crystal data top
C6D12N4Dx = 1.462 Mg m3
Mr = 152.27Mo Kα radiation, λ = 0.71073 Å
Cubic, I43mCell parameters from 1376 reflections
a = 7.0195 (1) Åθ = 4–29°
V = 345.88 (2) Å3µ = 0.09 mm1
Z = 2T = 297 K
F(000) = 1520.2 × 0.2 × 0.1 mm
Data collection top
80 reflections with I > 2σ(I)
φ & ω scansRint = 0.015
Absorption correction: multi-scan
SADABS (Siemens, 1996)
θmax = 26.2°, θmin = 5.8°
Tmin = 0.93, Tmax = 0.99h = 68
1374 measured reflectionsk = 88
83 independent reflectionsl = 88
Refinement top
Refinement on F20 restraints
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0436P)2 + 0.0602P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.031(Δ/σ)max < 0.001
wR(F2) = 0.093Δρmax = 0.09 e Å3
S = 1.33Δρmin = 0.15 e Å3
83 reflectionsAbsolute structure: Flack x determined using 30 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
8 parametersAbsolute structure parameter: 0.3 (7)
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
xyzUiso*/UeqOcc. (<1)
N10.6224 (2)0.6224 (2)0.6224 (2)0.0484 (11)
C20.7377 (4)0.5000000.5000000.0539 (11)
Atomic displacement parameters (Å2) top
N10.0484 (11)0.0484 (11)0.0484 (11)0.0094 (8)0.0094 (8)0.0094 (8)
C20.0301 (14)0.0659 (15)0.0659 (15)0.0000.0000.0020 (19)
Geometric parameters (Å, º) top
N1—C2i1.460 (2)C2—D2A0.9700
N1—C2ii1.460 (2)C2—D2B0.9700
N1—C21.460 (2)
C2i—N1—C2ii107.83 (16)N1iii—C2—D2A109.1
C2i—N1—C2107.83 (16)N1iii—C2—D2B109.1
C2ii—N1—C2107.83 (16)N1—C2—D2B109.1
N1iii—C2—N1112.7 (3)D2A—C2—D2B107.8
C2i—N1—C2—N1iii58.10 (17)C2ii—N1—C2—N1iii58.10 (17)
Symmetry codes: (i) z, x, y; (ii) y, z, x; (iii) y, x+1, z+1.

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