catena-Poly[[diiodo­zinc(II)]-[mu]-4,4'-bipyridine-[kappa]²N:N']

The title compound, [ZnI₂(bipy)]_n (bipy is 4,4'-bipyridine, C₁₀H₈N₂), has been prepared by the hydro­thermal reaction of ZnI₂ and bipy at 433 K. Each Zn atom is coordinated by two N atoms from two different bipy ligands and by two I atoms in a distorted tetra­hedral geometry, with Zn-N distances ranging from 2.068 (7) to 2.101 (8) Å and Zn-I distances ranging from 2.5471 (13) to 2.5673 (13) Å. The mol­ecular structure features a zigzag polymeric chain. Face-to-face [pi]-[pi] stacking inter­actions between adjacent bipy ligands stabilize the structure.

S1. Comment

Over the past few years considerable efforts have been devoted to the synthesis and structural characterization of coordination polymers. 4,4'-Bipyridine (bipy) as a bridging ligand has been used to construct supermolecular polymers (Hu & Englert, 2005; Nordell et al., 2004; Pedireddi & Varughese, 2004; Vittal et al., 2003; Yang et al., 2004). It is not unusual that the backbone of these polymers is subject to considerable modification due to the influence of the coligands and the difference in reaction parameters. For example, according to the literature, it is found that the structures of polymers of type [ZnX₂(bipy)] (X = Cl or Br) are influenced by the reaction conditions and coligands (Hu & Englert, 2001, 2005; Liang et al., 2001; Fu et al., 2001). Two isomorphic phases of the one-dimensional coordination polymer [ZnCl₂(bipy)] were prepared from hydrothermal reactions with different stoichiometry ratios of the reactants. It is interesting that when the temperature is decreased to 130 K both polymorphs can convert to a two-dimensional network and that the conversion is reversible (Hu & Englert, 2005). Polymeric [ZnBr₂(bipy)] has a one-dimensional zigzag chain structure (Hu & Englert, 2001). However, based on the results of a search in the Cambridge Structural Database (Version 5.27; Allen, 2002), the structure and properties of polymeric [ZnI₂(bipy)] have not been reported. We report here a new polymeric compound, [ZnI₂(bipy)]_n, (I), with a zigzag polymeric chain structure, obtained via hydrothermal synthesis.

In (I), there are two crystallographically independent Zn atoms in the asymmetric unit. Both are tetracoordinated in a distorted tetrahedral environment by two N atoms from two different bipy ligands and two I atoms. The differences are their Zn—N and Zn—I distances (Table 1). As a result of this coordination, the molecular structure shows a zigzag polymeric chain, which is similar to that in the polymers [ZnX₂(bipy)] (X = Cl or Br), as shown in Fig. 1. In (I), an interesting phenomenon is that the two pyridine rings of the same bipy ligand are not coplanar [the dihedral angles of between the two planes are 32.22 (13) and 38.42 (16)°]. In constrast, the two pyridine rings of the same bipy ligand in the polymers ZnX₂(bipy) (X = Cl or Br) are coplanar. Figs. 2 and 3 show that zigzag chains stack on top of each other. As shown in Fig. 2, there are two different π–π stacking interactions. One relates bipy ring R1 (N1/C1–C3/C9/C10) to bipy ring R2 (N2/C4–C8) of an adjacent bipy ligand, denoted R1ⁱ···R2 [symmetry code: (i) x, 3/2 − y, − 1/2 + z]. The second is formed between bipy ring R3 (N3/C11–C13/C19/C20) and bipy ring R4 (N4/C14–C18) of an adjacent bipy ligand, denoted R3···R4ⁱ [symmetry code: (i) x, −y + 3/2, z − 1/2]. The two bipy rings involved in each π–π stacking interaction are nearly parallel, with dihedral angles of 6.9 (3)° for R1ⁱ···R2 and 6.1 (4)° for R3···R4ⁱ, centroid-to-centroid distances of 4.282 (2) (R1ⁱ···R2) and 3.971 (2) Å (R3···R4ⁱ), and plane-to-plane distances of 3.61 (6) (R2···R1ⁱ) and 3.73 (6) Å (R3···R4ⁱ) which is smaller than that in both isomorphic polymers [ZnCl₂(bipy)] [3.85 (7) Å; Fu et al., 2001] and [ZnBr₂(bipy)] [4.17 (5) Å; Hu & Englert, 2001]. The face-to-face π–π stacking interactions between adjacent bipy ligands stabilize the structure.

S2. Experimental

A mixture of ZnI₂ (0.16 g, 0.5 mmol), bipy (0.78 g, 0.5 mmol) and water (13 ml) was sealed in a 25 ml Teflon-lined stainless-steel reactor, heated to 443 K for 72 h, and then slowly cooled to room temperature. Block-shaped lightyellow crystals of (I), suitable for X-ray analysis, were obtained by filtration (yield 23.2%).

S3. Refinement

All H atoms were located theoretically and refined as riding atoms, with C—H distances in the range 0.93—0.97 Å and with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SMART & SAINT (Siemens, 1996); data reduction: XPREP in SHELXTL (Siemens, 1996); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL and ASP (Chen, 2002); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. A view of the repeat unit of (I). Displacement ellipsoids are plotted at the 30% probability level and H atoms have been omitted for clarity. [Symmetry codes: (A)-1 + x, −y + 3/2, z − 1/2.]
	Fig. 2. The π–π interactions between pairs of adjacent bipy ligands. [Symmetry codes: (i) x, −y + 3/2, z − 1/2.]
	Fig. 3. The packing diagram of (I), viewed down the c axis. H atoms have been omitted for clarity.

catena-Poly[diiodozinc(II)-µ-4,4'-bipyridine-k² N:N']

Crystal data

[ZnI2(C10H8N2)]	F(000) = 1744
Mr = 950.71	Dx = 2.341 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 9437 reflections
a = 17.140 (3) Å	θ = 1.3–25.7°
b = 13.930 (3) Å	µ = 6.37 mm^−1
c = 11.950 (2) Å	T = 293 K
β = 109.00 (3)°	Block, light yellow
V = 2697.7 (10) Å^3	0.5 × 0.45 × 0.2 mm
Z = 4

Data collection

Siemens SMART CCD area-detector diffractometer	5080 independent reflections
Radiation source: fine-focus sealed tube	3979 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.030
ϕ and ω scans	θmax = 25.7°, θmin = 1.3°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −17→20
Tmin = 0.632, Tmax = 1.000	k = −16→16
14426 measured reflections	l = −14→11

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: inferred from neighbouring sites
wR(F^2) = 0.135	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0581P)^2 + 24.4231P] where P = (Fo^2 + 2Fc^2)/3
5080 reflections	(Δ/σ)max = 0.001
271 parameters	Δρmax = 1.08 e Å^−3
0 restraints	Δρmin = −0.76 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
Zn1	−0.38009 (6)	0.74595 (8)	0.54523 (10)	0.0431 (3)
Zn2	0.12596 (6)	0.71552 (7)	0.15077 (9)	0.0409 (2)
I1	−0.40061 (4)	0.58708 (5)	0.63828 (6)	0.0564 (2)
I2	−0.35877 (5)	0.91385 (5)	0.63893 (7)	0.0621 (2)
I3	0.13013 (4)	0.55375 (4)	0.05331 (6)	0.05166 (19)
I4	0.12093 (5)	0.87511 (5)	0.04460 (7)	0.0642 (2)
N1	−0.2812 (4)	0.7312 (6)	0.4830 (7)	0.0471 (18)
N2	0.0255 (4)	0.7154 (5)	0.2104 (7)	0.0423 (17)
N3	0.2259 (4)	0.7257 (5)	0.3070 (7)	0.0454 (18)
N4	0.5204 (4)	0.7473 (6)	0.8864 (7)	0.0452 (18)
C1	−0.2335 (7)	0.6530 (7)	0.4936 (11)	0.059 (3)
H1A	−0.2409	0.6014	0.5386	0.071*
C2	−0.1743 (6)	0.6471 (8)	0.4401 (11)	0.062 (3)
H2A	−0.1430	0.5915	0.4480	0.074*
C3	−0.1605 (5)	0.7221 (6)	0.3748 (8)	0.0410 (19)
C4	−0.0966 (5)	0.7185 (7)	0.3161 (9)	0.045 (2)
C5	−0.0811 (6)	0.6361 (7)	0.2631 (10)	0.054 (2)
H5A	−0.1116	0.5806	0.2615	0.065*
C6	−0.0199 (6)	0.6377 (7)	0.2130 (10)	0.055 (3)
H6A	−0.0091	0.5815	0.1787	0.067*
C7	0.0091 (6)	0.7952 (7)	0.2597 (10)	0.056 (3)
H7A	0.0389	0.8506	0.2578	0.068*
C8	−0.0500 (6)	0.7980 (7)	0.3127 (10)	0.053 (2)
H8A	−0.0591	0.8549	0.3474	0.063*
C9	−0.2093 (6)	0.8022 (7)	0.3652 (9)	0.049 (2)
H9A	−0.2024	0.8547	0.3213	0.059*
C10	−0.2679 (6)	0.8048 (7)	0.4199 (9)	0.053 (2)
H10A	−0.2998	0.8599	0.4130	0.063*
C11	0.2709 (6)	0.6501 (7)	0.3608 (9)	0.056 (3)
H11A	0.2620	0.5920	0.3201	0.067*
C12	0.3296 (6)	0.6519 (7)	0.4722 (9)	0.057 (3)
H12A	0.3594	0.5969	0.5039	0.069*
C13	0.3433 (5)	0.7374 (7)	0.5362 (8)	0.042 (2)
C14	0.4025 (5)	0.7436 (7)	0.6586 (8)	0.042 (2)
C15	0.4160 (6)	0.6631 (7)	0.7349 (9)	0.056 (2)
H15A	0.3857	0.6070	0.7108	0.067*
C16	0.4752 (6)	0.6690 (7)	0.8465 (9)	0.053 (2)
H16A	0.4836	0.6157	0.8958	0.063*
C17	0.5069 (6)	0.8237 (8)	0.8162 (9)	0.056 (2)
H17A	0.5370	0.8794	0.8434	0.068*
C18	0.4476 (6)	0.8229 (8)	0.7004 (9)	0.056 (3)
H18A	0.4400	0.8775	0.6533	0.067*
C19	0.2992 (6)	0.8169 (7)	0.4791 (9)	0.050 (2)
H19A	0.3086	0.8765	0.5162	0.060*
C20	0.2418 (6)	0.8085 (7)	0.3683 (9)	0.051 (2)
H20A	0.2124	0.8629	0.3337	0.061*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0403 (5)	0.0428 (6)	0.0477 (6)	0.0024 (4)	0.0163 (5)	−0.0036 (5)
Zn2	0.0401 (5)	0.0364 (5)	0.0475 (6)	−0.0006 (4)	0.0161 (4)	−0.0029 (4)
I1	0.0634 (4)	0.0467 (4)	0.0636 (4)	−0.0019 (3)	0.0268 (3)	0.0024 (3)
I2	0.0712 (5)	0.0476 (4)	0.0700 (5)	0.0013 (3)	0.0263 (4)	−0.0151 (3)
I3	0.0592 (4)	0.0376 (3)	0.0623 (4)	−0.0021 (3)	0.0255 (3)	−0.0079 (3)
I4	0.0890 (5)	0.0403 (4)	0.0651 (5)	−0.0033 (3)	0.0274 (4)	0.0059 (3)
N1	0.042 (4)	0.044 (4)	0.059 (5)	0.001 (3)	0.022 (4)	−0.003 (4)
N2	0.039 (4)	0.040 (4)	0.051 (4)	−0.003 (3)	0.019 (3)	−0.007 (3)
N3	0.040 (4)	0.043 (4)	0.053 (5)	0.003 (3)	0.015 (3)	−0.004 (4)
N4	0.041 (4)	0.047 (4)	0.049 (5)	−0.001 (3)	0.016 (4)	0.002 (4)
C1	0.066 (6)	0.044 (6)	0.084 (8)	0.009 (5)	0.046 (6)	0.015 (5)
C2	0.056 (6)	0.044 (6)	0.096 (8)	0.008 (5)	0.040 (6)	0.003 (6)
C3	0.035 (4)	0.038 (5)	0.052 (5)	−0.002 (4)	0.015 (4)	−0.004 (4)
C4	0.040 (5)	0.042 (5)	0.057 (6)	−0.007 (4)	0.022 (4)	−0.013 (4)
C5	0.056 (6)	0.043 (5)	0.075 (7)	−0.007 (4)	0.037 (5)	−0.010 (5)
C6	0.056 (6)	0.045 (6)	0.072 (7)	−0.004 (5)	0.031 (5)	−0.015 (5)
C7	0.051 (6)	0.045 (6)	0.077 (7)	−0.006 (4)	0.027 (5)	−0.011 (5)
C8	0.051 (5)	0.039 (5)	0.077 (7)	−0.006 (4)	0.032 (5)	−0.006 (5)
C9	0.051 (5)	0.035 (5)	0.067 (6)	0.000 (4)	0.028 (5)	0.005 (4)
C10	0.058 (6)	0.036 (5)	0.070 (7)	0.017 (4)	0.030 (5)	0.009 (5)
C11	0.062 (6)	0.042 (5)	0.056 (6)	0.002 (5)	0.009 (5)	−0.011 (5)
C12	0.062 (6)	0.043 (6)	0.059 (6)	0.016 (5)	0.008 (5)	0.001 (5)
C13	0.036 (4)	0.046 (5)	0.045 (5)	0.001 (4)	0.015 (4)	−0.001 (4)
C14	0.033 (4)	0.048 (5)	0.046 (5)	−0.003 (4)	0.015 (4)	−0.002 (4)
C15	0.051 (6)	0.048 (6)	0.067 (7)	−0.007 (4)	0.017 (5)	0.000 (5)
C16	0.056 (6)	0.049 (6)	0.053 (6)	−0.011 (5)	0.017 (5)	0.002 (5)
C17	0.058 (6)	0.050 (6)	0.057 (6)	−0.016 (5)	0.013 (5)	−0.001 (5)
C18	0.058 (6)	0.054 (6)	0.047 (6)	−0.001 (5)	0.004 (5)	0.006 (5)
C19	0.043 (5)	0.042 (5)	0.059 (6)	0.001 (4)	0.009 (4)	−0.014 (4)
C20	0.047 (5)	0.039 (5)	0.060 (6)	0.009 (4)	0.008 (5)	−0.002 (4)

Geometric parameters (Å, º)

Zn1—N1	2.071 (7)	C5—H5A	0.9300
Zn1—N4^i	2.101 (8)	C6—H6A	0.9300
Zn1—I1	2.5520 (13)	C7—C8	1.360 (14)
Zn1—I2	2.5673 (13)	C7—H7A	0.9300
Zn2—N2	2.068 (7)	C8—H8A	0.9300
Zn2—N3	2.088 (8)	C9—C10	1.365 (13)
Zn2—I4	2.5471 (13)	C9—H9A	0.9300
Zn2—I3	2.5483 (12)	C10—H10A	0.9300
N1—C10	1.335 (12)	C11—C12	1.383 (14)
N1—C1	1.343 (12)	C11—H11A	0.9300
N2—C7	1.329 (12)	C12—C13	1.393 (14)
N2—C6	1.338 (12)	C12—H12A	0.9300
N3—C11	1.340 (12)	C13—C19	1.389 (13)
N3—C20	1.344 (12)	C13—C14	1.486 (13)
N4—C17	1.328 (13)	C14—C18	1.348 (13)
N4—C16	1.333 (12)	C14—C15	1.416 (14)
N4—Zn1^ii	2.101 (8)	C15—C16	1.390 (14)
C1—C2	1.367 (14)	C15—H15A	0.9300
C1—H1A	0.9300	C16—H16A	0.9300
C2—C3	1.369 (14)	C17—C18	1.425 (14)
C2—H2A	0.9300	C17—H17A	0.9300
C3—C9	1.376 (12)	C18—H18A	0.9300
C3—C4	1.481 (12)	C19—C20	1.373 (13)
C4—C8	1.373 (13)	C19—H19A	0.9300
C4—C5	1.379 (13)	C20—H20A	0.9300
C5—C6	1.368 (13)
N1—Zn1—N4^i	101.5 (3)	N2—C7—C8	121.8 (9)
N1—Zn1—I1	108.4 (2)	N2—C7—H7A	119.1
N4^i—Zn1—I1	104.2 (2)	C8—C7—H7A	119.1
N1—Zn1—I2	103.3 (2)	C7—C8—C4	121.3 (9)
N4^i—Zn1—I2	108.2 (2)	C7—C8—H8A	119.4
I1—Zn1—I2	128.33 (5)	C4—C8—H8A	119.4
N2—Zn2—N3	103.0 (3)	C10—C9—C3	120.3 (9)
N2—Zn2—I4	106.0 (2)	C10—C9—H9A	119.9
N3—Zn2—I4	105.7 (2)	C3—C9—H9A	119.9
N2—Zn2—I3	107.9 (2)	N1—C10—C9	122.4 (8)
N3—Zn2—I3	109.4 (2)	N1—C10—H10A	118.8
I4—Zn2—I3	123.07 (5)	C9—C10—H10A	118.8
C10—N1—C1	117.8 (8)	N3—C11—C12	124.9 (9)
C10—N1—Zn1	115.9 (6)	N3—C11—H11A	117.6
C1—N1—Zn1	126.2 (7)	C12—C11—H11A	117.6
C7—N2—C6	117.3 (8)	C11—C12—C13	118.9 (9)
C7—N2—Zn2	118.1 (6)	C11—C12—H12A	120.5
C6—N2—Zn2	124.3 (6)	C13—C12—H12A	120.5
C11—N3—C20	115.5 (8)	C19—C13—C12	116.4 (8)
C11—N3—Zn2	123.5 (6)	C19—C13—C14	121.7 (8)
C20—N3—Zn2	120.5 (6)	C12—C13—C14	121.9 (8)
C17—N4—C16	117.9 (8)	C18—C14—C15	117.1 (9)
C17—N4—Zn1^ii	117.3 (6)	C18—C14—C13	122.5 (9)
C16—N4—Zn1^ii	124.5 (7)	C15—C14—C13	120.3 (8)
N1—C1—C2	121.7 (9)	C16—C15—C14	119.1 (9)
N1—C1—H1A	119.1	C16—C15—H15A	120.5
C2—C1—H1A	119.1	C14—C15—H15A	120.5
C1—C2—C3	120.9 (9)	N4—C16—C15	123.4 (9)
C1—C2—H2A	119.6	N4—C16—H16A	118.3
C3—C2—H2A	119.6	C15—C16—H16A	118.3
C2—C3—C9	116.9 (8)	N4—C17—C18	122.0 (9)
C2—C3—C4	122.3 (8)	N4—C17—H17A	119.0
C9—C3—C4	120.8 (8)	C18—C17—H17A	119.0
C8—C4—C5	117.2 (8)	C14—C18—C17	120.5 (10)
C8—C4—C3	120.9 (8)	C14—C18—H18A	119.7
C5—C4—C3	121.9 (8)	C17—C18—H18A	119.7
C6—C5—C4	118.5 (9)	C20—C19—C13	120.6 (9)
C6—C5—H5A	120.7	C20—C19—H19A	119.7
C4—C5—H5A	120.7	C13—C19—H19A	119.7
N2—C6—C5	123.9 (9)	N3—C20—C19	123.6 (9)
N2—C6—H6A	118.1	N3—C20—H20A	118.2
C5—C6—H6A	118.1	C19—C20—H20A	118.2

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