A charge-transfer salt composed of methyl viologen and hexa­cyanidoferrate(II)

The methyl viologen dication, used under the name Paraquat as an agricultural reagent, is a well-known electron-acceptor species that can participate in charge-transfer (CT) inter­actions. The determination of the crystal structure of this species is important for accessing the CT inter­action and CT-based pro­perties. The title hydrated salt, bis­(1,1′-dimethyl-4,4′-bipyridine-1,1′-diium) hexa­cyanidoferrate(II) octa­hydrate, (C₁₂H₁₄N₂)₂[Fe(CN)₆]·8H₂O or (MV)₂[Fe(CN)₆]·8H₂O [MV²⁺ is the 1,1′-dimethyl-4,4′-bipyridine-1,1′-diium (methyl viologen) dication], crystallizes in the space group P2₁/c with one MV²⁺ cation, half of an [Fe(CN)₆]⁴⁻ anion and four water mol­ecules in the asymmetric unit. The Fe^II atom of the [Fe(CN)₆]⁴⁻ anion lies on an inversion centre and has an octa­hedral coordination sphere defined by six cyanide ligands. The MV²⁺ cation is located on a general position and adopts a noncoplanar structure, with a dihedral angle of 40.32 (7)° between the planes of the pyridine rings. In the crystal, layers of electron-donor [Fe(CN)₆]⁴⁻ anions and layers of electron-acceptor MV²⁺ cations are formed and are stacked in an alternating manner parallel to the direction of the −2a + c axis, resulting in an alternate layered structure.

Computing details

Data collection: RAPID-AUTO (Rigaku, 2006); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2017); software used to prepare material for publication: SHELXL2014/7 & publCIF (Westrip, 2010).

Bis(1,1'-dimethyl-4,4'-bipyridine-1,1'-diium) hexacyanidoferrate(II) octahydrate

Crystal data

(C12H14N2)2[Fe(CN)6]·8H2O	F(000) = 768
Mr = 728.60	Dx = 1.371 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71075 Å
a = 8.73056 (18) Å	Cell parameters from 10573 reflections
b = 11.7379 (3) Å	θ = 3.4–32.0°
c = 17.6190 (7) Å	µ = 0.49 mm^−1
β = 102.1424 (8)°	T = 173 K
V = 1765.16 (9) Å^3	Block, deep blue
Z = 2	0.25 × 0.23 × 0.10 mm

Data collection

Rigaku R-AXIS RAPID imaging-plate diffractometer	6086 independent reflections
Radiation source: X-ray sealed tube	5223 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
Detector resolution: 10.00 pixels mm^-1	θmax = 32.0°, θmin = 3.4°
ω scans	h = −13→13
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −17→17
Tmin = 0.742, Tmax = 0.952	l = −26→26
37788 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)] = 0.042	Hydrogen site location: mixed
wR(F^2) = 0.130	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0725P)^2 + 0.7422P] where P = (Fo^2 + 2Fc^2)/3
6086 reflections	(Δ/σ)max < 0.001
249 parameters	Δρmax = 0.96 e Å^−3
0 restraints	Δρmin = −0.48 e Å^−3

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
Fe1	0.0000	0.5000	0.5000	0.01815 (8)
C1	0.16112 (15)	0.55824 (11)	0.58216 (7)	0.0219 (2)
C2	0.06284 (15)	0.34676 (11)	0.52770 (7)	0.0218 (2)
C3	−0.14104 (16)	0.48557 (12)	0.56983 (8)	0.0246 (2)
N1	0.25826 (15)	0.59657 (11)	0.63105 (7)	0.0294 (2)
N2	0.09604 (15)	0.25361 (11)	0.54721 (7)	0.0293 (2)
N3	−0.22612 (18)	0.47101 (14)	0.61156 (9)	0.0386 (3)
C11	0.22757 (15)	0.45265 (10)	0.86010 (7)	0.0206 (2)
C12	0.13606 (18)	0.37756 (12)	0.89267 (8)	0.0280 (3)
H12	0.136 (3)	0.379 (2)	0.9467 (13)	0.042*
C13	0.0396 (2)	0.30158 (13)	0.84563 (9)	0.0324 (3)
H13	−0.023 (3)	0.247 (2)	0.8658 (14)	0.049*
C21	−0.0818 (2)	0.22569 (17)	0.71762 (11)	0.0431 (4)
H21A	−0.1374	0.1793	0.7494	0.065*
H21B	−0.0252	0.1758	0.6884	0.065*
H21C	−0.1573	0.2719	0.6814	0.065*
C14	0.12202 (19)	0.36996 (13)	0.73576 (8)	0.0297 (3)
H14	0.109 (3)	0.360 (2)	0.6813 (14)	0.045*
C15	0.22295 (16)	0.44522 (11)	0.78073 (7)	0.0245 (2)
H15	0.284 (3)	0.4944 (17)	0.7567 (15)	0.037*
C16	0.31868 (15)	0.54442 (11)	0.90669 (7)	0.0210 (2)
C17	0.25621 (17)	0.60180 (12)	0.96263 (8)	0.0267 (3)
H17	0.162 (3)	0.584 (2)	0.9742 (13)	0.040*
C18	0.33364 (17)	0.69465 (13)	1.00029 (8)	0.0293 (3)
H18	0.295 (3)	0.744 (2)	1.0377 (14)	0.044*
C22	0.55005 (19)	0.83001 (14)	1.02528 (10)	0.0351 (3)
H22A	0.6416	0.8490	1.0037	0.053*
H22B	0.5837	0.8135	1.0808	0.053*
H22C	0.4773	0.8946	1.0180	0.053*
C19	0.53635 (17)	0.67296 (14)	0.93297 (10)	0.0313 (3)
H19	0.637 (3)	0.707 (2)	0.9256 (14)	0.047*
C20	0.46254 (16)	0.58053 (13)	0.89310 (9)	0.0290 (3)
H20	0.512 (3)	0.544 (2)	0.8603 (14)	0.043*
N11	0.03089 (16)	0.30139 (11)	0.76857 (7)	0.0301 (3)
N12	0.47067 (14)	0.72866 (11)	0.98484 (7)	0.0266 (2)
O1	0.4986 (2)	0.7498 (2)	0.70703 (13)	0.0883 (8)
H1A	0.4245	0.7028	0.6938	0.132*
H1B	0.4836	0.7839	0.7494	0.132*
O2	0.1495 (2)	0.02811 (13)	0.60196 (10)	0.0497 (3)
H2A	0.1806	0.0332	0.6492	0.074*
H2B	0.1280	0.1025	0.5848	0.074*
O3	−0.49972 (16)	0.39373 (13)	0.66445 (9)	0.0467 (3)
H3A	−0.4139	0.4214	0.6508	0.070*
H3B	−0.5868	0.4451	0.6508	0.070*
O4	−0.2470 (3)	0.6041 (2)	0.74506 (11)	0.0847 (7)
H4A	−0.2525	0.5641	0.7033	0.127*
H4B	−0.3225	0.6471	0.7338	0.127*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.01704 (12)	0.02161 (13)	0.01641 (12)	0.00133 (8)	0.00492 (8)	0.00039 (8)
C1	0.0225 (5)	0.0238 (5)	0.0204 (5)	0.0009 (4)	0.0067 (4)	0.0034 (4)
C2	0.0220 (5)	0.0265 (6)	0.0180 (5)	0.0015 (4)	0.0067 (4)	−0.0015 (4)
C3	0.0223 (6)	0.0284 (6)	0.0240 (6)	0.0048 (4)	0.0070 (5)	0.0034 (4)
N1	0.0292 (6)	0.0341 (6)	0.0242 (5)	−0.0070 (5)	0.0039 (4)	0.0016 (4)
N2	0.0337 (6)	0.0288 (5)	0.0268 (5)	0.0064 (5)	0.0098 (5)	0.0009 (4)
N3	0.0345 (7)	0.0473 (8)	0.0392 (7)	0.0112 (6)	0.0198 (6)	0.0132 (6)
C11	0.0232 (5)	0.0194 (5)	0.0192 (5)	0.0001 (4)	0.0047 (4)	0.0009 (4)
C12	0.0370 (7)	0.0277 (6)	0.0208 (5)	−0.0072 (5)	0.0095 (5)	0.0008 (5)
C13	0.0411 (8)	0.0296 (7)	0.0294 (6)	−0.0120 (6)	0.0142 (6)	−0.0015 (5)
C21	0.0457 (9)	0.0436 (9)	0.0389 (8)	−0.0191 (8)	0.0064 (7)	−0.0132 (7)
C14	0.0372 (7)	0.0309 (6)	0.0221 (6)	−0.0074 (5)	0.0087 (5)	−0.0036 (5)
C15	0.0294 (6)	0.0248 (6)	0.0205 (5)	−0.0046 (5)	0.0083 (5)	0.0003 (4)
C16	0.0215 (5)	0.0211 (5)	0.0197 (5)	0.0004 (4)	0.0030 (4)	−0.0001 (4)
C17	0.0261 (6)	0.0298 (6)	0.0258 (6)	−0.0041 (5)	0.0095 (5)	−0.0053 (5)
C18	0.0290 (6)	0.0321 (7)	0.0281 (6)	−0.0026 (5)	0.0093 (5)	−0.0093 (5)
C22	0.0322 (7)	0.0323 (7)	0.0405 (8)	−0.0067 (6)	0.0068 (6)	−0.0139 (6)
C19	0.0240 (6)	0.0327 (7)	0.0389 (7)	−0.0044 (5)	0.0103 (5)	−0.0107 (6)
C20	0.0238 (6)	0.0302 (6)	0.0349 (7)	−0.0027 (5)	0.0110 (5)	−0.0096 (5)
N11	0.0352 (6)	0.0281 (5)	0.0278 (6)	−0.0094 (5)	0.0081 (5)	−0.0060 (4)
N12	0.0238 (5)	0.0269 (5)	0.0286 (5)	−0.0019 (4)	0.0044 (4)	−0.0067 (4)
O1	0.0579 (10)	0.1224 (18)	0.0932 (14)	−0.0444 (11)	0.0356 (10)	−0.0718 (14)
O2	0.0620 (9)	0.0347 (6)	0.0565 (8)	−0.0018 (6)	0.0220 (7)	0.0026 (6)
O3	0.0389 (7)	0.0489 (7)	0.0550 (8)	0.0008 (6)	0.0160 (6)	0.0135 (6)
O4	0.1045 (17)	0.0897 (15)	0.0524 (10)	−0.0209 (13)	−0.0002 (10)	−0.0257 (10)

Geometric parameters (Å, º)

Fe1—C2^i	1.9136 (13)	C15—H15	0.94 (2)
Fe1—C2	1.9136 (13)	C16—C20	1.3932 (18)
Fe1—C1^i	1.9195 (13)	C16—C17	1.3959 (18)
Fe1—C1	1.9196 (13)	C17—C18	1.3770 (19)
Fe1—C3^i	1.9224 (14)	C17—H17	0.92 (2)
Fe1—C3	1.9224 (14)	C18—N12	1.3423 (19)
C1—N1	1.1646 (18)	C18—H18	0.99 (2)
C2—N2	1.1644 (18)	C22—N12	1.4817 (19)
C3—N3	1.1626 (19)	C22—H22A	0.9800
C11—C12	1.3918 (18)	C22—H22B	0.9800
C11—C15	1.3932 (17)	C22—H22C	0.9800
C11—C16	1.4806 (17)	C19—N12	1.3460 (18)
C12—C13	1.378 (2)	C19—C20	1.377 (2)
C12—H12	0.95 (2)	C19—H19	0.99 (2)
C13—N11	1.3439 (19)	C20—H20	0.90 (3)
C13—H13	0.96 (2)	O1—H1A	0.8449
C21—N11	1.480 (2)	O1—H1B	0.8803
C21—H21A	0.9800	O2—H2A	0.8222
C21—H21B	0.9800	O2—H2B	0.9299
C21—H21C	0.9800	O3—H3A	0.8944
C14—N11	1.3448 (19)	O3—H3B	0.9603
C14—C15	1.3751 (19)	O4—H4A	0.8661
C14—H14	0.95 (2)	O4—H4B	0.8201
C2^i—Fe1—C2	180.0	C15—C14—H14	125.7 (14)
C2^i—Fe1—C1^i	90.98 (5)	C14—C15—C11	119.88 (12)
C2—Fe1—C1^i	89.02 (5)	C14—C15—H15	119.2 (15)
C2^i—Fe1—C1	89.02 (5)	C11—C15—H15	120.8 (15)
C2—Fe1—C1	90.98 (5)	C20—C16—C17	118.35 (12)
C1^i—Fe1—C1	180.0	C20—C16—C11	121.65 (11)
C2^i—Fe1—C3^i	86.67 (5)	C17—C16—C11	119.89 (11)
C2—Fe1—C3^i	93.33 (5)	C18—C17—C16	119.80 (13)
C1^i—Fe1—C3^i	90.88 (6)	C18—C17—H17	116.5 (15)
C1—Fe1—C3^i	89.13 (6)	C16—C17—H17	123.6 (15)
C2^i—Fe1—C3	93.33 (5)	N12—C18—C17	120.39 (13)
C2—Fe1—C3	86.67 (5)	N12—C18—H18	114.0 (14)
C1^i—Fe1—C3	89.13 (6)	C17—C18—H18	125.5 (14)
C1—Fe1—C3	90.87 (6)	N12—C22—H22A	109.5
C3^i—Fe1—C3	180.0	N12—C22—H22B	109.5
N1—C1—Fe1	178.10 (12)	H22A—C22—H22B	109.5
N2—C2—Fe1	176.52 (11)	N12—C22—H22C	109.5
N3—C3—Fe1	176.59 (14)	H22A—C22—H22C	109.5
C12—C11—C15	118.44 (12)	H22B—C22—H22C	109.5
C12—C11—C16	121.35 (11)	N12—C19—C20	120.58 (13)
C15—C11—C16	120.05 (11)	N12—C19—H19	114.1 (14)
C13—C12—C11	119.55 (12)	C20—C19—H19	125.3 (14)
C13—C12—H12	119.0 (14)	C19—C20—C16	119.61 (13)
C11—C12—H12	121.4 (15)	C19—C20—H20	117.8 (16)
N11—C13—C12	120.42 (13)	C16—C20—H20	122.5 (16)
N11—C13—H13	117.2 (14)	C13—N11—C14	121.36 (13)
C12—C13—H13	122.4 (14)	C13—N11—C21	120.19 (14)
N11—C21—H21A	109.5	C14—N11—C21	118.45 (13)
N11—C21—H21B	109.5	C18—N12—C19	121.22 (12)
H21A—C21—H21B	109.5	C18—N12—C22	119.21 (12)
N11—C21—H21C	109.5	C19—N12—C22	119.57 (12)
H21A—C21—H21C	109.5	H1A—O1—H1B	106.8
H21B—C21—H21C	109.5	H2A—O2—H2B	105.1
N11—C14—C15	120.15 (13)	H3A—O3—H3B	111.7
N11—C14—H14	114.2 (14)	H4A—O4—H4B	103.3
C12—C11—C16—C17	−37.41 (19)

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
O1—H1A···N1	0.84	2.05	2.872 (2)	164
O1—H1B···O3^ii	0.88	1.97	2.823 (2)	162
O2—H2A···O4^iii	0.82	2.01	2.797 (3)	160
O2—H2B···N2	0.93	1.89	2.822 (2)	176
O3—H3A···N3	0.89	2.00	2.887 (2)	174
O3—H3B···N1^iv	0.96	2.22	3.155 (2)	165
O4—H4A···N3	0.87	2.01	2.861 (3)	170
O4—H4B···O1^iv	0.82	1.95	2.771 (4)	180

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