1-(4-Chloro-2-nitro­phenyl)-4,4'-bipyridinium triiodide

The title compound, C₁₆H₁₁ClN₃O₂⁺·I₃^-, consists of a bipyridinium cation and a triiodide anion. The two pyridine rings of the cation are not coplanar, with a dihedral angle of 28.83 (4)°. The benzene ring is also twisted out of the mean plane of the adjoining pyridine ring by 64.27 (5)°. The I₃^- anions are slightly bent and asymmetric, with an I-I-I angle of 178.24 (5)° and I-I bond distances of 2.937 (2) and 2.957 (2) Å. The packing shows a columnar arrangement, with parallel stacks of bipyridinium and I₃^- ions along the b axis.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.018 Å
• R factor = 0.069
• wR factor = 0.179
• Data-to-parameter ratio = 15.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Owing to their potential as prototypical electron-transfer regents (Willner et al., 1990), herbicides (Summers, 1980) and materials for electrochromic displays (ECD) (Bruinink et al., 1977; Yasuda et al., 1987), viologens (N,N'-disubstituted 4,4'-bipyridinium dications) have been extensively studied in the past decade. In order to incorporate the viologen-specific function into a coordination polymer, there have been several viologen derivative ligands prepared by nucleophilic substitution reactions (Ashton et al., 1994). In particular, viologen derivatives which are π-conjugated exhibit photoelectrochemical activity and a change of spin multiplicity upon external stimuli (Iyoda et al., 1999). Their fascinating functions are attracting considerable attention from chemists. We report here the synthesis and structure of a new π-conjugated viologen derivative made up of a bipyridinium cation and a triiodide anion.

There is one crystallographically independent bipyridinium cation and one crystallographically independent triiodide anion, lying in general positions (Fig. 1). In the crystal structure, the bipyridinium cation is twisted, with an interplanar angle of 28.83 (4)° between the two pyridine rings, and a larger dihedral angle of 64.27 (5)° between the benzene ring and the adjacent pyridine ring. Because of the 2-nitro-4-chlorophenyl substituent on one side of the bipyridine core, the two pyridine rings within the bipyridine nucleus are asymmetric, there are great differences between the corresponding C—N and C—C bond lengths. The N1—C7 [1.366 (2) Å] and N1—C11 [1.371 (2) Å] distances of the substituted pyridine ring are typically longer than N2—C14 [1.333 (18) Å] and N2—C15 [1.357 (17) Å] of the unsubstituent one, due to the electron delocalization with the nitrophenyl moiety.

The counter-ions appear in the structure in the form of slightly asymmetrical I₃⁻ ions, which can be described as a donor-acceptor or hypervalent I⁻—I₂ interaction. The I—I bond distances in I₃⁻ are 2.937 (2) and 2.957 (2) Å. The shorter I—I bond distance in this asymmetrical I₃⁻ ion is longer than in pure iodine [2.666 (2) Å in the gas phase (Karle, 1955) and 2.715 (6) Å in the solid state at 110 K (van Bolhuis et al., 1967)]. This elongation is attributable to the donation of electron density from I⁻ to the σ*-antibonding LUMO of the I₂ molecule (Blake et al., 1998; Purcell & Kotz, 1977). I₃⁻ is not exactly linear, the angle I1—I2—I3 being 178.24 (5)°. The packing diagram (Fig. 2) shows a columnar arrangement, with parallel stacks of bipyridinium and I₃⁻ ions along the b axis.

S2. Experimental

2 ml DMF was added to a mixture of 4,4'-bipyridine (1.56 g, 10 mmol) and 2,5-dichloronitrobenzene (0.96 g, 5 mmol), and the solution was refluxed at 403 K under nitrogen for 8 h. The solvent was reduced to a small volume in vacuum, benzene was added, and the precipitate was filtered off and washed with benzene, then dried to afford a brown solid. The brown solid (0.0348 g, 0.1 mmol) was added to a solution of KI (0.066 g, 1 mmol) in water. The resulting yellow solution was allowed to stand at room temperature for several days to form brown block crystals.

S3. Refinement

All H atoms were positioned geometrically and included as riding atoms, with C—H = 0.93 Å.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1994); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The cation and anion in the structure of the title compound, with the atom-numbering scheme. Displacement ellipsoids are shown at the 30% probability level.
	Fig. 2. Packing diagram, viewed along the b axis. H atoms have been omitted for clarity.

1-(4-Chloro-2-nitrophenyl)-4,4'-bipyridinium triiodide

Crystal data

C16H11ClN3O2^+·I3^−	F(000) = 1280
Mr = 693.43	Dx = 2.259 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 210 reflections
a = 13.658 (3) Å	θ = 1.5–25.1°
b = 7.5018 (15) Å	µ = 4.74 mm^−1
c = 19.936 (4) Å	T = 293 K
β = 93.37 (3)°	Block, brown
V = 2039.1 (7) Å^3	0.54 × 0.14 × 0.12 mm
Z = 4

Data collection

Siemems SMART CCD diffractometer	3492 independent reflections
Radiation source: fine-focus sealed tube	2394 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.046
ϕ and ω scans	θmax = 25.1°, θmin = 1.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −16→15
Tmin = 0.455, Tmax = 0.566	k = −8→8
5930 measured reflections	l = −23→10

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)] = 0.069	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.179	H-atom parameters constrained
S = 1.18	w = 1/[σ^2(Fo^2) + (0.0646P)^2 + 19.8577P] where P = (Fo^2 + 2Fc^2)/3
3492 reflections	(Δ/σ)max < 0.001
226 parameters	Δρmax = 1.02 e Å^−3
0 restraints	Δρmin = −1.06 e Å^−3

Special details

Geometry. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

2.6483 (0.0701) x + 6.6652 (0.0211) y − 8.5049 (0.1090) z = 4.5411 (0.0306)

* 0.0046 (0.0093) C12 * −0.0082 (0.0100) C13 * 0.0084 (0.0106) C14 * 0.0010 (0.0100) C15 * −0.0012 (0.0099) C16 * −0.0047 (0.0095) N2

Rms deviation of fitted atoms = 0.0055

2.0779 (0.0714) x + 7.3955 (0.0077) y + 1.2274 (0.1127) z = 2.6232 (0.0549)

Angle to previous plane (with approximate e.s.d.) = 28.83 (0.38)

* 0.0128 (0.0097) C7 * −0.0061 (0.0105) C8 * −0.0036 (0.0100) C9 * 0.0067 (0.0099) C10 * −0.0002 (0.0096) C11 * −0.0096 (0.0091) N1

Rms deviation of fitted atoms = 0.0076

0.6162 (0.0866) x − 2.8590 (0.0442) y − 18.4302 (0.0495) z = 2.9368 (0.0883)

Angle to previous plane (with approximate e.s.d.) = 64.27 (1/2)

* −0.0141 (0.0113) C1 * 0.0255 (0.0101) C2 * −0.0186 (0.0096) C3 * 0.0006 (0.0106) C4 * 0.0108 (0.0124) C5 * −0.0041 (0.0127) C6

Rms deviation of fitted atoms = 0.0149

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
I2	0.34154 (7)	0.32262 (13)	0.04415 (5)	0.0504 (3)
I3	0.54058 (7)	0.18600 (14)	0.07512 (5)	0.0544 (3)
I1	0.14284 (8)	0.46258 (16)	0.00871 (5)	0.0643 (4)
Cl	1.2060 (3)	−0.0665 (7)	−0.1076 (3)	0.0881 (16)
N1	0.7899 (7)	0.1578 (14)	−0.1588 (5)	0.039 (3)
N2	0.2776 (8)	0.3053 (16)	−0.2077 (6)	0.049 (3)
N3	0.9568 (9)	0.4131 (17)	−0.1877 (6)	0.051 (3)
O1	1.0300 (8)	0.5022 (16)	−0.1952 (7)	0.083 (4)
O2	0.8750 (8)	0.4686 (15)	−0.1980 (7)	0.076 (4)
C5	0.9118 (11)	−0.053 (2)	−0.1212 (9)	0.068 (5)
H5A	0.8602	−0.1286	−0.1121	0.082*
C6	1.0096 (11)	−0.109 (2)	−0.1084 (9)	0.065 (5)
H6A	1.0235	−0.2216	−0.0904	0.078*
C1	1.0838 (10)	0.004 (2)	−0.1229 (8)	0.053 (4)
C2	1.0664 (9)	0.170 (2)	−0.1515 (6)	0.049 (4)
H2A	1.1184	0.2406	−0.1637	0.058*
C3	0.9707 (9)	0.2305 (19)	−0.1616 (6)	0.041 (3)
C4	0.8935 (9)	0.1144 (19)	−0.1473 (7)	0.041 (3)
C7	0.7328 (9)	0.1680 (18)	−0.1050 (7)	0.044 (3)
H7A	0.7612	0.1566	−0.0616	0.053*
C11	0.7507 (9)	0.1808 (19)	−0.2232 (6)	0.043 (3)
H11A	0.7909	0.1757	−0.2592	0.052*
C8	0.6344 (9)	0.195 (2)	−0.1146 (7)	0.048 (4)
H8A	0.5959	0.1973	−0.0777	0.057*
C10	0.6506 (8)	0.2117 (19)	−0.2343 (7)	0.043 (3)
H10A	0.6235	0.2280	−0.2778	0.051*
C9	0.5903 (9)	0.2181 (18)	−0.1790 (6)	0.039 (3)
C12	0.4819 (9)	0.2482 (17)	−0.1899 (6)	0.034 (3)
C13	0.4296 (9)	0.3306 (19)	−0.1401 (6)	0.042 (3)
H13A	0.4613	0.3666	−0.0998	0.051*
C16	0.4290 (10)	0.1933 (19)	−0.2487 (7)	0.049 (4)
H16A	0.4607	0.1365	−0.2828	0.058*
C14	0.3286 (10)	0.358 (2)	−0.1522 (8)	0.057 (4)
H14A	0.2951	0.4163	−0.1194	0.069*
C15	0.3291 (9)	0.2248 (19)	−0.2554 (7)	0.046 (4)
H15A	0.2952	0.1887	−0.2950	0.055*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I2	0.0563 (6)	0.0531 (6)	0.0416 (5)	−0.0022 (5)	−0.0004 (4)	0.0049 (5)
I3	0.0522 (6)	0.0605 (7)	0.0495 (6)	0.0011 (5)	−0.0062 (4)	−0.0066 (5)
I1	0.0560 (6)	0.0727 (8)	0.0634 (7)	0.0056 (6)	−0.0031 (5)	0.0094 (6)
Cl	0.039 (2)	0.097 (4)	0.128 (4)	0.014 (2)	−0.006 (2)	0.036 (3)
N1	0.039 (6)	0.040 (7)	0.037 (6)	0.003 (5)	−0.001 (5)	−0.002 (5)
N2	0.047 (7)	0.048 (7)	0.053 (7)	0.001 (6)	0.008 (6)	−0.001 (6)
N3	0.046 (8)	0.056 (8)	0.050 (7)	−0.013 (7)	0.000 (6)	0.009 (6)
O1	0.050 (7)	0.072 (8)	0.126 (11)	−0.010 (6)	0.002 (7)	0.039 (8)
O2	0.051 (7)	0.053 (7)	0.122 (11)	0.005 (6)	−0.004 (6)	0.031 (7)
C5	0.039 (8)	0.054 (10)	0.111 (14)	0.001 (8)	0.001 (8)	0.035 (10)
C6	0.048 (9)	0.032 (8)	0.114 (14)	0.012 (7)	0.000 (9)	0.021 (9)
C1	0.035 (7)	0.062 (10)	0.058 (9)	0.014 (7)	−0.027 (7)	0.002 (8)
C2	0.033 (7)	0.074 (11)	0.038 (7)	0.004 (7)	−0.002 (6)	0.013 (8)
C3	0.042 (8)	0.043 (8)	0.038 (7)	−0.003 (6)	0.004 (6)	−0.006 (7)
C4	0.028 (7)	0.048 (8)	0.048 (8)	0.002 (6)	0.002 (6)	−0.002 (7)
C7	0.050 (8)	0.041 (8)	0.040 (7)	0.002 (7)	0.000 (6)	0.004 (7)
C11	0.041 (7)	0.050 (9)	0.040 (8)	−0.010 (7)	0.012 (6)	−0.004 (7)
C8	0.029 (7)	0.074 (11)	0.041 (8)	−0.002 (7)	0.004 (6)	0.001 (8)
C10	0.024 (6)	0.058 (10)	0.046 (8)	0.006 (6)	0.005 (5)	−0.009 (7)
C9	0.034 (7)	0.046 (8)	0.036 (7)	−0.002 (6)	−0.001 (5)	−0.002 (6)
C12	0.034 (6)	0.023 (6)	0.044 (7)	−0.005 (5)	0.001 (6)	0.001 (6)
C13	0.039 (7)	0.057 (9)	0.031 (7)	−0.007 (7)	0.007 (5)	−0.004 (7)
C16	0.051 (8)	0.050 (9)	0.045 (8)	−0.003 (7)	0.000 (6)	−0.007 (7)
C14	0.035 (8)	0.069 (11)	0.070 (11)	−0.006 (7)	0.015 (7)	−0.002 (9)
C15	0.029 (7)	0.052 (9)	0.055 (9)	−0.009 (6)	−0.012 (6)	−0.002 (7)

Geometric parameters (Å, º)

I2—I3	2.937 (2)	C3—C4	1.410 (18)
I2—I1	2.957 (2)	C7—C8	1.362 (18)
Cl—C1	1.760 (13)	C7—H7A	0.930
N1—C7	1.366 (16)	C11—C10	1.392 (17)
N1—C11	1.371 (16)	C11—H11A	0.930
N1—C4	1.457 (16)	C8—C9	1.397 (18)
N2—C14	1.333 (18)	C8—H8A	0.930
N2—C15	1.357 (17)	C10—C9	1.415 (17)
N3—O2	1.199 (14)	C10—H10A	0.930
N3—O1	1.218 (14)	C9—C12	1.501 (17)
N3—C3	1.474 (19)	C12—C13	1.401 (17)
C5—C4	1.38 (2)	C12—C16	1.402 (18)
C5—C6	1.41 (2)	C13—C14	1.401 (19)
C5—H5A	0.930	C13—H13A	0.930
C6—C1	1.37 (2)	C16—C15	1.384 (18)
C6—H6A	0.930	C16—H16A	0.930
C1—C2	1.39 (2)	C14—H14A	0.930
C2—C3	1.386 (18)	C15—H15A	0.930
C2—H2A	0.930
I3—I2—I1	178.24 (5)	N1—C7—H7A	119.9
C7—N1—C11	121.3 (11)	N1—C11—C10	119.7 (11)
C7—N1—C4	118.8 (11)	N1—C11—H11A	120.1
C11—N1—C4	119.9 (10)	C10—C11—H11A	120.1
C14—N2—C15	116.6 (12)	C7—C8—C9	121.1 (12)
O2—N3—O1	123.5 (13)	C7—C8—H8A	119.4
O2—N3—C3	118.8 (12)	C9—C8—H8A	119.4
O1—N3—C3	117.6 (12)	C11—C10—C9	119.5 (12)
C4—C5—C6	119.4 (14)	C11—C10—H10A	120.2
C4—C5—H5A	120.3	C9—C10—H10A	120.2
C6—C5—H5A	120.3	C8—C9—C10	118.2 (12)
C1—C6—C5	118.8 (14)	C8—C9—C12	121.4 (11)
C1—C6—H6A	120.6	C10—C9—C12	120.5 (11)
C5—C6—H6A	120.6	C13—C12—C16	117.6 (12)
C6—C1—C2	122.4 (12)	C13—C12—C9	120.2 (11)
C6—C1—Cl	118.9 (11)	C16—C12—C9	122.1 (12)
C2—C1—Cl	118.7 (12)	C12—C13—C14	118.7 (12)
C1—C2—C3	119.5 (13)	C12—C13—H13A	120.7
C1—C2—H2A	120.3	C14—C13—H13A	120.7
C3—C2—H2A	120.3	C15—C16—C12	119.2 (13)
C2—C3—C4	118.6 (13)	C15—C16—H16A	120.4
C2—C3—N3	117.1 (12)	C12—C16—H16A	120.4
C4—C3—N3	124.3 (12)	N2—C14—C13	124.1 (14)
C5—C4—C3	121.2 (12)	N2—C14—H14A	118.0
C5—C4—N1	114.6 (12)	C13—C14—H14A	118.0
C3—C4—N1	124.1 (12)	N2—C15—C16	123.8 (13)
C8—C7—N1	120.1 (12)	N2—C15—H15A	118.1
C8—C7—H7A	119.9	C16—C15—H15A	118.1