catena-Poly[[silver(I)-[mu]-[9,10-bis­(1H-benzimidazol-1-ylmethyl)anthracene]-[kappa]²N³:N^3'] bis­(nitrato-[kappa]O)silver(I)]

Yellow needle-shaped crystals of the title compound, {[Ag(C₃₀H₂₂N₄)][Ag(NO₃)₂]}_n, were obtained by the reaction of AgNO₃ and 9,10-bis­(benzimidazol-1-ylmethyl)anthracene (L) in a 2:1 ratio. The asymmetric unit consists of two Ag^I cations, one half L ligand and one nitrate anion. One Ag^I cation occupies a crystallographic inversion centre and links two N-atom donors of two distinct L ligands to form an infinite one-dimensional coordination polymer. The second Ag^I cation lies on a crystallographic twofold axis and is coordinated by two O-atom donors of two nitrate anions to form an [Ag(NO₃)₂]^- counter-ion. The polymeric chains are linked into a supra­molecular framework via weak Ag...O [3.124 (5) Å] and Ag...[pi] (2.982 Å) inter­actions ([pi] is the centroid of an outer anthracene benzene ring). The [pi] inter­actions contain two short Ag...C contacts [2.727 (6) and 2.765 (6) Å], which can be considered to define Ag-[eta]²-anthracene bonding inter­actions. In comparison with a previously reported binuclear Ag^I complex [Du, Hu, Zhang, Zeng & Bu (2008). CrystEngComm, 10, 1866-1874], this new one-dimensional coordination polymer was obtained by changing the metal-ligand ratio during the synthesis.

S1. Comment

The design and construction of novel metal–organic frameworks (MOFs) based on transition metals and organic spacers are currently attracting considerable attention, because MOFs have intriguing aesthetic structures with wide potential applications, such as molecular magnetism (Marino et al., 2011), heterogeneous catalysis (Malla et al., 2010), gas storage (Lin et al., 2010) and photoluminescence (Pandey et al., 2010). Generally, MOFs are constructed through coordination of metal ions and organic linkers. For the construction of metal complexes, many factors can affect the final crystal structure, such as the structure of the organic ligand, the coordination geometry of the metal ion, the metal–ligand ratio and so on. Secondary interactions such as hydrogen bonding, π–π stacking and host–guest interactions must also be considered.

Flexible ligands have drawn much attention in this area because the flexible spacers allow them to bend or rotate when coordinating to metal centres in order to conform to the coordination geometries of the metal ions. Several N-donor ligands, such as triazole (Klaus & Yassin, 2006), imidazole (Carlucci et al., 2004) and benzimidazole-containing ligands (Zhang et al., 2007), have been synthesized and their coordination polymers show interesting properties. In our previous work, flexible ligands were used to construct various complex structures, including discrete molecules and one-, two- and three-dimensional networks, and their coordination polymers showed interesting fluorescence properties (Du et al., 2008, 2012). In the present work, the title one-dimensional Ag^I coordination polymer, (I), has been synthesized and its structure is now reported.

The asymmetric unit of (I) contains two crystallographically independent Ag^I cations, one half of a 9,10-bis(1H-benzimidazol-1-ylmethyl)anthracene ligand (L) and one nitrate anion (Fig. 1). Atom Ag1 occupies a crystallographic inversion centre and is linked by two N-atom donors from two distinct ligands [Ag1—N2 = 2.134 (5) Å] in a bicoordinated linear fashion, creating a polymeric cationic one-dimensional chain (Fig. 2). Each L ligand coordinates to two Ag^I ions and all ligands are equivalent, adopting trans–gauche conformations. The dihedral angle between the planes of the benzimidazole and anthracene rings is 75.95 (11)°. The Ag—N bond length and the conformation of the ligand are similar to those in Ag^I complexes of related flexible ligands (Wang et al., 2007). The nearest nonbonding Ag···Ag distance along the polymer is 12.912 (2) Å. Atom Ag2 lies on a crystallographic twofold axis and is linked by two O-atom donors from two nitrate anions to form an [Ag(NO₃)₂]^- counter-ion [Ag2—O3 = 2.356 (5) Å; Fig. 1]. The coordination geometry of Ag2 is distorted from linear [O3—Ag2—O3ⁱⁱ = 146.1 (3)°; symmetry code: (ii) -x + 1, y, -z + 1/2].

Interactions between a cation and the π system of a ligand represent a possible driving force for the building of novel molecular architectures. Several similar complexes have been reported in which Ag–η²-anthracene bonding interactions have been discussed. In anthracene tetrakis(silver perchlorate) monohydrate, for example, a silver–anthracene interaction was reported with Ag—C distances of 2.454 (8) and 2.560 (8) Å (Griffith & Amma, 1974). Discrete mononuclear complexes, [Ag(L¹)(ClO₄)(C₆H₆)₂] and [Ag₂(L²)_0.5(C₆H₆)_0.5(CF₃SO₃)₂] (L¹ = ???? [Please define] and L² = 9,10-diphenylanthracene), were synthesized by Munakata and co-workers with Ag—C distances ranging from 2.41 (1) to 2.68 (8) Å (Munakata et al., 1998, 2003). Only one previous example in a coordination polymer was found in the literature, namely {[Ag₈(L³)₃(l4-hmt)₂(H₂O)₆](ClO₄)₂}_∞ (L³ = anthracene-9,10-dicarboxylate and hmt = hexamethylenetetramine; l4-hmt is what?), with reported Ag—C distances of 2.631 (4) and 2.740 (4) Å (Liu et al., 2008). In (I), the Ag2—C1 and Ag2—C2 distances are 2.727 (6) and 2.765 (6) Å, respectively, similar to the previously reported results. The corresponding distance to the centroid of the C1–C6 aromatic ring is 2.982 Å. Considering these Ag···π interactions, the coordination geometry of Ag2 can be described as a flattened tetrahedron.

Weak Ag···O interactions also exist between the different units (Fig. 2), with the Ag1···O2ⁱ distance being 3.124 (5) Å [symmetry code: (i) -x + 1, -y + 1, -z]. Considering these interactions, the coordination geometry of Ag1 resembles a distorted square plane.

The reaction between this bi-benzimidazole ligand [9,10-bis(benzimidazol-1-ylmethyl)anthracene, L] and AgNO₃ has been studied previously (Du et al., 2008). It is interesting that the metal–ligand ratio affects the final structure of the complex. When the metal–ligand ratio is 1:1, a discrete binuclear Ag^I complex is obtained and the ligand adopts a cis conformation. A similar binuclear Ag^I complex based on a related flexible bi-benzimidizole ligand has also been reported by other researchers (Su et al., 2003). The one-dimensional chain coordination polymer in this present work was synthesized under similar reaction conditions, except that the metal–ligand ratio was changed to 2:1. In the polymer thus formed, the ligand adopts a trans conformation. An additional Ag^I cation is incorporated in the structure as [Ag(NO₃)₂]^- counter-ions.

In summary, a new polymer with a one-dimensional chain motif has been obtained based on a flexible bi-benzimidazole organic ligand, 9,10-bis(benzimidazol-1-ylmethyl)anthracene, and AgNO₃. The metal–ligand ratio during synthesis can affect the self-assembly process and the final structure. Weak Ag···O and Ag···π interactions link the different units into a three-dimensional supramolecular structure.

Related literature

For related literature, see: Carlucci et al. (2004); Du et al. (2008, 2012); Griffith & Amma (1974); Klaus & Yassin (2006); Lin et al. (2010); Liu et al. (2008); Malla Reddy, Rama Krishna & Soumyajit (2010); Marino et al. (2011); Munakata et al. (1998, 2003); Pandey et al. (2010); Su et al. (2003); Wang et al. (2007); Zhang et al. (2007).

S2. Experimental

9,10-Bis(benzimidazol-1-ylmethyl)anthracence (L) was prepared according to the literature method of Du et al. (2008). A buffer layer of a solution (5 ml) of methanol and chloroform (1:1 v/v) was carefully layered over a chloroform solution (5 ml) of L (0.05 mmol) and then a solution of AgNO₃ (0.10 mmol) in methanol (5 ml) was layered over the buffer layer. The container was left in the dark for about three weeks at room temperature, after which yellow needle-shaped crystals of (I) were obtained (yield ~30%, based on L). Analysis, calculated for C₃₀H₂₂Ag₂N₆O₆: C 46.30, H 2.85, N 10.80%; found: C 46.48, H 2.68, N 10.88%.

S3. Refinement

All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H = 0.93 (CH) or 0.97 Å (CH₂), and with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) -x + 1, -y + 1, -z; (ii) -x + 1, y, -z + 1/2.]
	Fig. 2. The one-dimensional coordination network of (I), viewed along the b axis. H atoms have been omitted. Dashed lines indicate Ag···O interactions? [Symmetry codes: (i) -x + 1, -y + 1, -z; (ii) -x + 1, y, -z + 1/2; (iii) -x + 3/2, -y + 3/2, -z.]
	Fig. 3. A view of the Ag···O (dashed lines; purple in the electronic version of the paper) and Ag···π (dashed lines; red) interactions between the different units of (I). H atoms have been omitted.

catena-Poly[[silver(I)-µ-[9,10-bis(1H-benzimidazol-1- ylmethyl)anthracene]-κ²N³:N^3'] bis(nitrato-κO)silver(I)]

Crystal data

[Ag(C30H22N4)][Ag(NO3)2]	F(000) = 1544
Mr = 778.28	Dx = 1.885 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 10039 reflections
a = 24.980 (5) Å	θ = 3.2–27.5°
b = 6.5472 (13) Å	µ = 1.49 mm^−1
c = 17.278 (4) Å	T = 293 K
β = 103.96 (3)°	Needle, yellow
V = 2742.3 (10) Å^3	0.23 × 0.21 × 0.16 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	2415 independent reflections
Radiation source: fine-focus sealed tube	1697 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.088
ϕ and ω scans	θmax = 25.0°, θmin = 3.2°
Absorption correction: multi-scan (SADABS; Bruker, 2000)	h = −29→29
Tmin = 0.726, Tmax = 0.797	k = −7→7
10890 measured reflections	l = −20→20

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)] = 0.061	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.103	H-atom parameters constrained
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0306P)^2 + 4.9608P] where P = (Fo^2 + 2Fc^2)/3
2415 reflections	(Δ/σ)max < 0.001
201 parameters	Δρmax = 0.70 e Å^−3
0 restraints	Δρmin = −0.43 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
Ag1	0.7500	0.7500	0.0000	0.0507 (3)
Ag2	0.5000	0.48981 (13)	0.2500	0.0608 (3)
N2	0.71269 (19)	0.5045 (7)	0.0491 (3)	0.0391 (12)
N1	0.64601 (17)	0.3056 (7)	0.0731 (3)	0.0317 (12)
N3	0.4046 (2)	0.2521 (9)	0.1480 (4)	0.0459 (13)
C6	0.5346 (2)	0.5513 (8)	0.0761 (3)	0.0266 (13)
C9	0.6586 (2)	0.4756 (9)	0.0373 (3)	0.0372 (15)
H9	0.6322	0.5635	0.0076	0.045*
C5	0.4887 (2)	0.6818 (8)	0.0380 (3)	0.0263 (13)
C15	0.6954 (2)	0.2111 (8)	0.1094 (3)	0.0316 (14)
C10	0.7369 (2)	0.3386 (9)	0.0942 (3)	0.0365 (15)
C7	0.5443 (2)	0.3710 (8)	0.0366 (3)	0.0285 (13)
C1	0.5677 (2)	0.6069 (9)	0.1527 (3)	0.0363 (15)
H1	0.5969	0.5233	0.1774	0.044*
C8	0.5912 (2)	0.2303 (9)	0.0784 (3)	0.0331 (14)
H8A	0.5906	0.2177	0.1341	0.040*
H8B	0.5853	0.0955	0.0546	0.040*
C3	0.5122 (3)	0.9063 (10)	0.1540 (4)	0.0421 (16)
H3	0.5049	1.0230	0.1803	0.050*
C4	0.4797 (2)	0.8590 (9)	0.0816 (4)	0.0368 (15)
H4	0.4504	0.9450	0.0593	0.044*
C14	0.7071 (3)	0.0326 (9)	0.1535 (4)	0.0464 (17)
H14	0.6792	−0.0495	0.1638	0.056*
O2	0.37198 (19)	0.1697 (7)	0.0922 (3)	0.0681 (14)
C13	0.7620 (3)	−0.0175 (10)	0.1815 (4)	0.0579 (19)
H13	0.7715	−0.1367	0.2109	0.070*
C12	0.8036 (3)	0.1082 (11)	0.1664 (4)	0.0523 (19)
H12	0.8402	0.0702	0.1864	0.063*
C2	0.5573 (2)	0.7799 (9)	0.1902 (4)	0.0404 (16)
H2A	0.5798	0.8151	0.2396	0.048*
C11	0.7924 (2)	0.2854 (10)	0.1232 (4)	0.0501 (18)
H11	0.8206	0.3669	0.1135	0.060*
O3	0.4363 (2)	0.3849 (8)	0.1328 (3)	0.0758 (16)
O1	0.4065 (3)	0.2081 (8)	0.2170 (3)	0.0878 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.0411 (4)	0.0478 (5)	0.0674 (6)	−0.0077 (4)	0.0213 (4)	0.0133 (4)
Ag2	0.0596 (5)	0.0719 (6)	0.0471 (5)	0.000	0.0055 (4)	0.000
N2	0.035 (3)	0.037 (3)	0.046 (3)	−0.002 (3)	0.011 (2)	0.011 (3)
N1	0.023 (3)	0.032 (3)	0.039 (3)	0.002 (2)	0.005 (2)	0.010 (2)
N3	0.040 (3)	0.047 (3)	0.047 (4)	0.009 (3)	0.003 (3)	0.006 (3)
C6	0.023 (3)	0.027 (3)	0.031 (3)	−0.003 (2)	0.009 (3)	−0.001 (3)
C9	0.027 (3)	0.043 (4)	0.040 (4)	0.002 (3)	0.004 (3)	0.010 (3)
C5	0.022 (3)	0.030 (3)	0.030 (3)	−0.004 (2)	0.012 (3)	0.000 (3)
C15	0.027 (3)	0.033 (4)	0.033 (3)	0.002 (3)	0.003 (3)	−0.002 (3)
C10	0.033 (4)	0.039 (4)	0.038 (4)	0.002 (3)	0.009 (3)	−0.004 (3)
C7	0.021 (3)	0.033 (3)	0.033 (3)	0.000 (3)	0.009 (3)	0.012 (3)
C1	0.028 (3)	0.042 (4)	0.034 (4)	−0.004 (3)	−0.002 (3)	0.003 (3)
C8	0.025 (3)	0.036 (3)	0.038 (3)	−0.003 (3)	0.006 (3)	−0.002 (3)
C3	0.051 (4)	0.042 (4)	0.038 (4)	−0.002 (3)	0.020 (3)	−0.011 (3)
C4	0.035 (4)	0.040 (4)	0.037 (4)	0.003 (3)	0.013 (3)	0.004 (3)
C14	0.041 (4)	0.039 (4)	0.057 (4)	0.005 (3)	0.007 (3)	0.014 (3)
O2	0.054 (3)	0.060 (3)	0.078 (4)	−0.005 (3)	−0.008 (3)	0.001 (3)
C13	0.063 (5)	0.045 (4)	0.057 (5)	0.016 (4)	−0.003 (4)	0.011 (4)
C12	0.030 (4)	0.058 (5)	0.061 (5)	0.014 (4)	−0.005 (3)	−0.001 (4)
C2	0.041 (4)	0.043 (4)	0.035 (4)	−0.013 (3)	0.004 (3)	−0.008 (3)
C11	0.027 (3)	0.060 (5)	0.061 (5)	−0.003 (3)	0.006 (3)	0.000 (4)
O3	0.065 (3)	0.091 (4)	0.068 (4)	−0.036 (3)	0.009 (3)	0.005 (3)
O1	0.135 (5)	0.080 (4)	0.050 (4)	0.020 (4)	0.027 (4)	0.020 (3)

Geometric parameters (Å, º)

Ag1—N2	2.134 (5)	C10—C11	1.401 (8)
Ag1—N2^i	2.134 (5)	C7—C5^iii	1.396 (7)
Ag2—O3	2.356 (5)	C7—C8	1.528 (7)
Ag2—O3^ii	2.356 (5)	C1—C2	1.361 (8)
N2—C9	1.331 (7)	C1—H1	0.9300
N2—C10	1.387 (7)	C8—H8A	0.9700
N1—C9	1.347 (6)	C8—H8B	0.9700
N1—C15	1.387 (7)	C3—C4	1.354 (8)
N1—C8	1.478 (6)	C3—C2	1.415 (8)
N3—O1	1.216 (6)	C3—H3	0.9300
N3—O2	1.227 (6)	C4—H4	0.9300
N3—O3	1.245 (6)	C14—C13	1.380 (8)
C6—C7	1.413 (7)	C14—H14	0.9300
C6—C1	1.428 (7)	C13—C12	1.398 (9)
C6—C5	1.454 (7)	C13—H13	0.9300
C9—H9	0.9300	C12—C11	1.372 (8)
C5—C7^iii	1.396 (7)	C12—H12	0.9300
C5—C4	1.430 (7)	C2—H2A	0.9300
C15—C14	1.387 (7)	C11—H11	0.9300
C15—C10	1.405 (8)
N2—Ag1—N2^i	180.0 (2)	C2—C1—H1	119.3
O3—Ag2—O3^ii	146.1 (3)	C6—C1—H1	119.3
C9—N2—C10	105.2 (5)	N1—C8—C7	112.7 (4)
C9—N2—Ag1	124.8 (4)	N1—C8—H8A	109.1
C10—N2—Ag1	129.8 (4)	C7—C8—H8A	109.1
C9—N1—C15	107.2 (5)	N1—C8—H8B	109.1
C9—N1—C8	128.7 (5)	C7—C8—H8B	109.1
C15—N1—C8	124.0 (4)	H8A—C8—H8B	107.8
O1—N3—O2	121.8 (6)	C4—C3—C2	120.8 (6)
O1—N3—O3	119.7 (6)	C4—C3—H3	119.6
O2—N3—O3	118.5 (6)	C2—C3—H3	119.6
C7—C6—C1	122.2 (5)	C3—C4—C5	122.4 (6)
C7—C6—C5	118.7 (5)	C3—C4—H4	118.8
C1—C6—C5	119.1 (5)	C5—C4—H4	118.8
N2—C9—N1	112.8 (5)	C13—C14—C15	116.9 (6)
N2—C9—H9	123.6	C13—C14—H14	121.5
N1—C9—H9	123.6	C15—C14—H14	121.5
C7^iii—C5—C4	123.6 (5)	C14—C13—C12	121.0 (6)
C7^iii—C5—C6	119.9 (5)	C14—C13—H13	119.5
C4—C5—C6	116.5 (5)	C12—C13—H13	119.5
N1—C15—C14	132.1 (5)	C11—C12—C13	122.4 (6)
N1—C15—C10	105.4 (5)	C11—C12—H12	118.8
C14—C15—C10	122.4 (5)	C13—C12—H12	118.8
N2—C10—C11	131.0 (6)	C1—C2—C3	119.9 (6)
N2—C10—C15	109.3 (5)	C1—C2—H2A	120.0
C11—C10—C15	119.8 (6)	C3—C2—H2A	120.0
C5^iii—C7—C6	121.4 (5)	C12—C11—C10	117.4 (6)
C5^iii—C7—C8	120.1 (5)	C12—C11—H11	121.3
C6—C7—C8	118.4 (5)	C10—C11—H11	121.3
C2—C1—C6	121.3 (5)	N3—O3—Ag2	110.7 (4)
C10—N2—C9—N1	1.5 (7)	C5—C6—C7—C8	−177.6 (4)
Ag1—N2—C9—N1	178.1 (4)	C7—C6—C1—C2	−179.2 (5)
C15—N1—C9—N2	−1.9 (7)	C5—C6—C1—C2	−0.5 (8)
C8—N1—C9—N2	175.4 (5)	C9—N1—C8—C7	−0.1 (8)
C7—C6—C5—C7^iii	−0.8 (8)	C15—N1—C8—C7	176.8 (5)
C1—C6—C5—C7^iii	−179.6 (5)	C5^iii—C7—C8—N1	103.1 (6)
C7—C6—C5—C4	178.2 (4)	C6—C7—C8—N1	−78.4 (6)
C1—C6—C5—C4	−0.6 (7)	C2—C3—C4—C5	0.0 (9)
C9—N1—C15—C14	−179.5 (6)	C7^iii—C5—C4—C3	179.8 (5)
C8—N1—C15—C14	3.1 (9)	C6—C5—C4—C3	0.8 (8)
C9—N1—C15—C10	1.4 (6)	N1—C15—C14—C13	−179.9 (6)
C8—N1—C15—C10	−176.0 (5)	C10—C15—C14—C13	−0.9 (9)
C9—N2—C10—C11	178.8 (6)	C15—C14—C13—C12	0.6 (10)
Ag1—N2—C10—C11	2.4 (10)	C14—C13—C12—C11	−0.3 (11)
C9—N2—C10—C15	−0.5 (6)	C6—C1—C2—C3	1.4 (8)
Ag1—N2—C10—C15	−176.9 (4)	C4—C3—C2—C1	−1.1 (9)
N1—C15—C10—N2	−0.6 (6)	C13—C12—C11—C10	0.2 (10)
C14—C15—C10—N2	−179.8 (5)	N2—C10—C11—C12	−179.7 (6)
N1—C15—C10—C11	−180.0 (5)	C15—C10—C11—C12	−0.4 (9)
C14—C15—C10—C11	0.8 (9)	O1—N3—O3—Ag2	6.4 (7)
C1—C6—C7—C5^iii	179.5 (5)	O2—N3—O3—Ag2	−174.1 (4)
C5—C6—C7—C5^iii	0.8 (8)	O3^ii—Ag2—O3—N3	48.3 (4)
C1—C6—C7—C8	1.1 (7)

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