Bis(2-ethyl-1H-imidazole-κN ³)bis­(nitrito-κ² O,O′)copper(II) dihydrate

Abstract

In the title compound, [Cu(NO₂)₂(C₅H₈N₂)]·2H₂O, the Cu²⁺ ion exhibits site symmetry 2 and is hexacoordinated by four O atoms from two nitrite ions and two N atoms from two 2-ethyl-1H-imidazole mol­ecules. A free water mol­ecule assists in forming a three-dimensional network holding together the complexes via O—H⋯N, O—H⋯O and N—H⋯O hydrogen bonds.

Related literature

For general background on ferroelectric compounds with metal–organic framework structures, see: Fu et al. (2009 ▶); Ye et al. (2006 ▶); Zhang et al. (2008 ▶, 2010 ▶). For graph-set motifs of hydrogen bonds, see: Bernstein et al. (1995 ▶).

Experimental

Crystal data

• [Cu(NO₂)₂(C₅H₈N₂)]·2H₂O

• M _r = 383.86

• Orthorhombic,

• a = 12.960 (6) Å

• b = 17.635 (7) Å

• c = 7.288 (3) Å

• V = 1665.7 (12) ų

• Z = 4

• Mo Kα radiation

• μ = 1.35 mm⁻¹

• T = 293 K

• 0.30 × 0.25 × 0.20 mm

Data collection

• Rigaku SCXmini diffractometer

• Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ▶) T _min = 0.674, T _max = 0.763

• 16649 measured reflections

• 1902 independent reflections

• 1712 reflections with I > 2σ(I)

• R _int = 0.032

Refinement

• R[F ² > 2σ(F ²)] = 0.031

• wR(F ²) = 0.079

• S = 1.10

• 1902 reflections

• 113 parameters

• 5 restraints

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

• Δρ_max = 0.33 e Å⁻³

• Δρ_min = −0.24 e Å⁻³

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.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Cu1—N1	1.9752 (17)
Cu1—O6	2.0255 (15)
Cu1—O5	2.4501 (18)

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2B⋯O7	0.86	1.99	2.830 (3)	167
O7—H1⋯O6ii	0.84 (1)	2.05 (2)	2.862 (2)	163 (3)
O7—H2⋯N3iii	0.83 (1)	2.18 (1)	3.004 (3)	167 (3)

Symmetry codes: (ii) ; (iii) .

supplementary crystallographic information

Comment

We synthesized the title compound with the aim to find new ferroelectric materials (Fu et al., 2009; Ye et al., 2006; Zhang et al., 2008; Zhang et al., 2010). For the title compound no dielectric anomalies were observed in the range from 190 K to near its melting point (m.p. >400 K). A view of the title compound is shown in Fig. 1. The structure is consolidated by multiple intermolecular and intramolecular hydrogen bonds between O and N. This hydrogen bonding (Table 1, Fig. 2) produces a three-dimensional network. Hydrogen bonding is the most reliable design element in the non-covalent assembly of neutral molecules with donor and acceptor functionalities, and as such it is the most important interaction in crystal engineering (Bernstein et al., 1995). The two contact distances between Cu and the oxygens of the nitrate ion are very different (Cu1–O5=2.4501 (18) Å and Cu1–O6=2.0255 (15) Å), showing thus only moderate bonding.

Experimental

An aqueous solution of 2-ethyl imidazole (2.4 g, 25 mmol) and H₂SO₄(12.5 mmol) was treated with CuSO₄ (250 g, 12.5 mmol). After the mixture was churned for a few minutes, Ba(NO₂)₂ (6.18 g, 25 mmol) was added to give a blue solution. Slow evaporation of the solution yielded blue crystals after a few days.

Refinement

Positional parameters of all H atoms except H1 and H2 were calculated geometrically and the H atoms were set to ride the C atoms and N atoms to which they are bonded, with U_iso(H)= 1.2 U_iso(C, N) and 1.5 U_iso(C) for methyl H atoms. The H atoms of the water molecule were restrained with O—H = 0.84 Å yielding O7—H1 = 0.835 (11) Å and O7—H2 = 0.834 (11) Å.

Figures

Fig. 1.

The molecular structure of the title compound, with the displacement ellipsoids drawn at the 30% probability level. The weak Cu—O interactions and the hydrogen bonds are shown as dashed lines. [Symmetry code: (A) - 1-x, y, 1/2-z]

Fig. 2.

A view of the N—H···O, O—H···N and O—H···O interactions (dotted lines) in the crystal structure of the title compound. [Symmetry codes: (i)-x + 3/2, y - 1/2, z (ii)-x + 3/2, -y + 1/2, z + 1/2]

Crystal data

[Cu(NO2)2(C5H8N2)]·2H2O	F(000) = 796
Mr = 383.86	Dx = 1.531 Mg m−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 3875 reflections
a = 12.960 (6) Å	θ = 2.8–27.5°
b = 17.635 (7) Å	µ = 1.35 mm−1
c = 7.288 (3) Å	T = 293 K
V = 1665.7 (12) Å3	Block, blue
Z = 4	0.30 × 0.25 × 0.20 mm

Data collection

Rigaku, SCXmini diffractometer	1902 independent reflections
Radiation source: fine-focus sealed tube	1712 reflections with I > 2σ(I)
graphite	Rint = 0.032
ω scans	θmax = 27.5°, θmin = 3.6°
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	h = −16→16
Tmin = 0.674, Tmax = 0.763	k = −22→22
16649 measured reflections	l = −9→9

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.079	H atoms treated by a mixture of independent and constrained refinement
S = 1.10	w = 1/[σ2(Fo2) + (0.0424P)2 + 0.3653P] where P = (Fo2 + 2Fc2)/3
1902 reflections	(Δ/σ)max = 0.001
113 parameters	Δρmax = 0.33 e Å−3
5 restraints	Δρmin = −0.24 e Å−3

Special details

Geometry. All e.s.d.'s 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 and angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry.

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
C1	0.65105 (15)	0.16593 (12)	0.2425 (3)	0.0354 (4)
C2	0.63010 (17)	0.21323 (12)	−0.0306 (3)	0.0429 (5)
H2A	0.6067	0.2436	−0.1262	0.051*
C3	0.69903 (18)	0.15687 (14)	−0.0455 (3)	0.0502 (6)
H3A	0.7321	0.1411	−0.1521	0.060*
C4	0.64560 (18)	0.15017 (13)	0.4424 (3)	0.0451 (5)
H4A	0.6091	0.1914	0.5021	0.054*
H4B	0.7151	0.1488	0.4917	0.054*
C5	0.5918 (2)	0.07583 (15)	0.4881 (4)	0.0637 (7)
H5A	0.5923	0.0683	0.6185	0.096*
H5B	0.6274	0.0347	0.4293	0.096*
H5C	0.5218	0.0776	0.4453	0.096*
N1	0.59959 (13)	0.21864 (9)	0.1508 (2)	0.0342 (4)
N2	0.71115 (13)	0.12722 (11)	0.1257 (3)	0.0465 (4)
H2B	0.7508	0.0899	0.1541	0.056*
Cu1	0.5000	0.292843 (17)	0.2500	0.02994 (13)
O6	0.57539 (11)	0.37719 (8)	0.1173 (2)	0.0460 (4)
O7	0.82902 (14)	0.00761 (11)	0.2776 (3)	0.0563 (5)
O5	0.44637 (13)	0.34927 (11)	−0.0420 (2)	0.0604 (5)
N3	0.52032 (17)	0.39184 (12)	−0.0252 (3)	0.0528 (5)
H1	0.848 (2)	−0.0289 (14)	0.213 (4)	0.088 (12)*
H2	0.8774 (18)	0.0299 (17)	0.330 (5)	0.104 (13)*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
C1	0.0307 (9)	0.0311 (10)	0.0443 (11)	−0.0003 (8)	−0.0020 (8)	−0.0012 (8)
C2	0.0446 (12)	0.0477 (12)	0.0364 (11)	0.0071 (9)	0.0052 (9)	0.0002 (9)
C3	0.0488 (12)	0.0564 (14)	0.0455 (13)	0.0086 (10)	0.0094 (10)	−0.0069 (11)
C4	0.0462 (11)	0.0459 (12)	0.0434 (12)	0.0009 (9)	−0.0055 (10)	0.0050 (10)
C5	0.0735 (17)	0.0546 (15)	0.0631 (16)	−0.0072 (13)	0.0031 (14)	0.0163 (12)
N1	0.0349 (8)	0.0324 (8)	0.0352 (9)	0.0022 (6)	0.0032 (7)	0.0002 (7)
N2	0.0405 (9)	0.0434 (10)	0.0557 (12)	0.0136 (8)	0.0012 (9)	−0.0035 (9)
Cu1	0.0318 (2)	0.0253 (2)	0.0327 (2)	0.000	0.00267 (12)	0.000
O6	0.0511 (8)	0.0358 (7)	0.0512 (9)	−0.0066 (6)	0.0063 (7)	0.0036 (7)
O7	0.0532 (10)	0.0438 (10)	0.0720 (12)	0.0097 (8)	−0.0056 (9)	−0.0079 (9)
O5	0.0549 (10)	0.0723 (12)	0.0541 (10)	−0.0012 (9)	−0.0072 (8)	0.0181 (9)
N3	0.0633 (13)	0.0455 (11)	0.0497 (12)	0.0011 (9)	0.0107 (10)	0.0131 (9)

Geometric parameters (Å, °)

C1—N1	1.325 (3)	C5—H5B	0.9600
C1—N2	1.341 (3)	C5—H5C	0.9600
C1—C4	1.485 (3)	N1—Cu1	1.9752 (17)
C2—C3	1.341 (3)	N2—H2B	0.8600
C2—N1	1.383 (3)	Cu1—N1i	1.9752 (17)
C2—H2A	0.9300	Cu1—O6	2.0255 (15)
C3—N2	1.362 (3)	Cu1—O6i	2.0255 (15)
C3—H3A	0.9300	Cu1—O5	2.4501 (18)
C4—C5	1.522 (3)	O6—N3	1.287 (3)
C4—H4A	0.9700	O7—H1	0.835 (11)
C4—H4B	0.9700	O7—H2	0.834 (11)
C5—H5A	0.9600	O5—N3	1.223 (3)
N1—C1—N2	109.23 (18)	C1—N1—C2	106.86 (17)
N1—C1—C4	127.04 (19)	C1—N1—Cu1	127.51 (14)
N2—C1—C4	123.73 (19)	C2—N1—Cu1	125.63 (14)
C3—C2—N1	108.6 (2)	C1—N2—C3	108.61 (18)
C3—C2—H2A	125.7	C1—N2—H2B	125.7
N1—C2—H2A	125.7	C3—N2—H2B	125.7
C2—C3—N2	106.7 (2)	N1i—Cu1—N1	97.01 (10)
C2—C3—H3A	126.7	N1i—Cu1—O6	167.58 (7)
N2—C3—H3A	126.7	N1—Cu1—O6	89.80 (7)
C1—C4—C5	113.4 (2)	N1i—Cu1—O6i	89.80 (7)
C1—C4—H4A	108.9	N1—Cu1—O6i	167.58 (7)
C5—C4—H4A	108.9	O6—Cu1—O6i	85.48 (9)
C1—C4—H4B	108.9	N1i—Cu1—O5	113.70 (7)
C5—C4—H4B	108.9	N1—Cu1—O5	97.84 (7)
H4A—C4—H4B	107.7	O6—Cu1—O5	54.81 (6)
C4—C5—H5A	109.5	O6i—Cu1—O5	88.83 (7)
C4—C5—H5B	109.5	N3—O6—Cu1	105.39 (13)
H5A—C5—H5B	109.5	H1—O7—H2	113.6 (19)
C4—C5—H5C	109.5	N3—O5—Cu1	86.57 (13)
H5A—C5—H5C	109.5	O5—N3—O6	113.08 (18)
H5B—C5—H5C	109.5

Symmetry codes: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2B···O7	0.86	1.99	2.830 (3)	167.
O7—H1···O6ii	0.84 (1)	2.05 (2)	2.862 (2)	163 (3)
O7—H2···N3iii	0.83 (1)	2.18 (1)	3.004 (3)	167 (3)

Symmetry codes: (ii) −x+3/2, y−1/2, z; (iii) −x+3/2, −y+1/2, z+1/2.