1,4-Di­methyl­piperazine-1,4-diium dibromide dihydrate

In the title hydrated mol­ecular salt, C₆H₁₆N₂²⁺·2Br⁻·2H₂O, the complete 1,4-dimethyl­piperazine-1,4-diium dication is generated by crystallographic inversion symmetry and both exocyclic C—N bonds are in equatorial orientations. In the crystal, the components are linked by N—H⋯O and O—H⋯Br hydrogen bonds, generating chains propagating in [110].

Related literature

For background to mol­ecular ferroelectrics, see: Fu et al. (2009).

Experimental

Crystal data

• C₆H₁₆N₂²⁺·2Br⁻·2H₂O

• M_r = 312.06

• Triclinic,

• a = 6.2975 (13) Å

• b = 7.0180 (14) Å

• c = 7.2143 (14) Å

• α = 71.54 (3)°

• β = 86.62 (3)°

• γ = 85.54 (3)°

• V = 301.32 (10) ų

• Z = 1

• Mo Kα radiation

• μ = 6.70 mm⁻¹

• T = 293 K

• 0.30 × 0.30 × 0.20 mm

Data collection

• Rigaku SCXmini CCD diffractometer

• Absorption correction: multi-scan (CrystalClear; Rigaku, 2005) T_min = 0.154, T_max = 0.262

• 3084 measured reflections

• 1370 independent reflections

• 1131 reflections with I > 2σ(I)

• R_int = 0.067

Refinement

• R[F² > 2σ(F²)] = 0.059

• wR(F²) = 0.169

• S = 1.02

• 1370 reflections

• 64 parameters

• 3 restraints

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.80 e Å⁻³

• Δρ_min = −1.12 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O1^i	0.91	1.83	2.737 (9)	174
O1—H1WA⋯Br1^ii	0.85 (6)	2.51 (9)	3.275 (7)	151 (11)
O1—H1WB⋯Br1	0.85 (3)	2.41 (4)	3.244 (7)	166 (7)
Symmetry codes: (i) x-1, y, z; (ii) -x+1, -y, -z+1.

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

Dielectric constant measurements of compounds as a function of temperature is the basic methods to find the materials which possess potential ferroelectric phase changes (Fu et al., 2009). The dielectric constant of the title compound has been measured,but showed no dielectric disuniformity in the range 113–353 K(mp.403–410 K).

The asymmetric unit of the title compound is shown in Fig. 1. crystallized in the monoclinic P-1 space group, The crystal packing Fig. 2 features weak intermolecular O—H···Br and N—H···O hydrogen bonds (Table 1).

Related literature

For background to molecular ferroelectrics, see: Fu et al. (2009).

S2. Experimental

1,4-Dimethyl-piperazine (0.57 g) and an excess of hydrobromic acid (0.95 g) were dissolved in methanol without any precipitation under stirring at room temperature. Colourless blocks of the title compound were obtained by slow evaporation of a methanol solution at room temperature over two days.

S3. Refinement

H atoms were placed in calculated positions (N—H = 0.89 Å; C—H = 0.96 Å and 0.97 Å for Csp³ atoms), assigned fixed U_iso values [1.5Ueq(Csp³,N)] and allowed to ride.The H1WA and H1WB on the O1 were restrained with O—H =0.85 Å yielding O1—H1 = 0.8448 Å and O1 —H2 = 0.8440 Å, with U_iso(H) = 1.2 U_iso(O).

Computing details

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of the title compound with 30% probability displacement ellipsoids.
	Fig. 2. A view of the packing of the title compound, stacking along the b axis. Dashed lines indicate hydrogen bonds.

1,4-Dimethylpiperazine-1,4-diium dibromide dihydrate

Crystal data

C6H16N2^2+·2Br^−·2H2O	V = 301.32 (10) Å^3
Mr = 312.06	Z = 1
Triclinic, P1	F(000) = 156
Hall symbol: -P 1	Dx = 1.720 Mg m^−3
a = 6.2975 (13) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.0180 (14) Å	θ = 3.1–27.5°
c = 7.2143 (14) Å	µ = 6.70 mm^−1
α = 71.54 (3)°	T = 293 K
β = 86.62 (3)°	Block, colorless
γ = 85.54 (3)°	0.30 × 0.30 × 0.20 mm

Data collection

Rigaku SCXmini CCD diffractometer	1370 independent reflections
Radiation source: fine-focus sealed tube	1131 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.067
Detector resolution: 13.6612 pixels mm^-1	θmax = 27.5°, θmin = 3.1°
CCD_Profile_fitting scans	h = −8→7
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −9→9
Tmin = 0.154, Tmax = 0.262	l = −9→9
3084 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.059	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.169	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0897P)^2 + 0.3362P] where P = (Fo^2 + 2Fc^2)/3
1370 reflections	(Δ/σ)max = 0.024
64 parameters	Δρmax = 0.80 e Å^−3
3 restraints	Δρmin = −1.12 e Å^−3

Special details

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.0403 (8)	0.3473 (7)	0.6882 (7)	0.0319 (11)
H1A	−0.0362	0.2477	0.6754	0.038*
C2	−0.1103 (10)	0.5311 (10)	0.6709 (9)	0.0355 (13)
H2A	−0.2225	0.4973	0.7717	0.043*
H2B	−0.0331	0.6371	0.6904	0.043*
C3	0.2067 (9)	0.3955 (10)	0.5259 (9)	0.0346 (13)
H3A	0.2991	0.2759	0.5350	0.042*
H3B	0.2934	0.4979	0.5406	0.042*
C1	0.1381 (11)	0.2748 (10)	0.8819 (10)	0.0428 (15)
H1B	0.2564	0.1808	0.8788	0.064*
H1C	0.0342	0.2098	0.9796	0.064*
H1D	0.1872	0.3869	0.9129	0.064*
Br1	0.61718 (10)	0.21220 (10)	0.19573 (10)	0.0445 (3)
O1	0.7864 (11)	0.0695 (11)	0.6378 (10)	0.0737 (19)
H1WA	0.675 (9)	0.027 (18)	0.707 (10)	0.11 (5)*
H1WB	0.757 (12)	0.090 (12)	0.519 (4)	0.05 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.035 (3)	0.031 (2)	0.028 (3)	−0.003 (2)	−0.002 (2)	−0.007 (2)
C2	0.037 (3)	0.043 (3)	0.027 (3)	0.001 (3)	0.002 (2)	−0.012 (3)
C3	0.031 (3)	0.041 (3)	0.031 (3)	0.003 (2)	−0.001 (2)	−0.013 (3)
C1	0.056 (4)	0.043 (4)	0.028 (3)	0.000 (3)	−0.010 (3)	−0.008 (3)
Br1	0.0393 (4)	0.0481 (5)	0.0451 (5)	−0.0090 (3)	−0.0021 (3)	−0.0116 (3)
O1	0.080 (4)	0.084 (4)	0.055 (4)	−0.048 (4)	−0.012 (3)	−0.007 (3)

Geometric parameters (Å, º)

N1—C1	1.482 (8)	C3—H3A	0.9700
N1—C3	1.498 (8)	C3—H3B	0.9700
N1—C2	1.516 (8)	C1—H1B	0.9600
N1—H1A	0.9100	C1—H1C	0.9600
C2—C3^i	1.497 (9)	C1—H1D	0.9600
C2—H2A	0.9700	O1—H1WA	0.853 (10)
C2—H2B	0.9700	O1—H1WB	0.854 (10)
C3—C2^i	1.497 (9)
C1—N1—C3	111.3 (5)	N1—C3—H3A	109.2
C1—N1—C2	111.1 (5)	C2^i—C3—H3A	109.2
C3—N1—C2	109.7 (5)	N1—C3—H3B	109.2
C1—N1—H1A	108.2	C2^i—C3—H3B	109.2
C3—N1—H1A	108.2	H3A—C3—H3B	107.9
C2—N1—H1A	108.2	N1—C1—H1B	109.5
C3^i—C2—N1	110.7 (5)	N1—C1—H1C	109.5
C3^i—C2—H2A	109.5	H1B—C1—H1C	109.5
N1—C2—H2A	109.5	N1—C1—H1D	109.5
C3^i—C2—H2B	109.5	H1B—C1—H1D	109.5
N1—C2—H2B	109.5	H1C—C1—H1D	109.5
H2A—C2—H2B	108.1	H1WA—O1—H1WB	107 (3)
N1—C3—C2^i	111.9 (5)
C1—N1—C2—C3^i	179.4 (5)	C1—N1—C3—C2^i	180.0 (5)
C3—N1—C2—C3^i	56.0 (7)	C2—N1—C3—C2^i	−56.7 (7)

Symmetry code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1^ii	0.91	1.83	2.737 (9)	174
O1—H1WA···Br1^iii	0.85 (6)	2.51 (9)	3.275 (7)	151 (11)
O1—H1WB···Br1	0.85 (3)	2.41 (4)	3.244 (7)	166 (7)

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