Assembly of a two-dimensional layer structure with 1,4-bis­(1H-benzimid­azol-1-yl­methyl)­benzene dihydrate via hydrogen bonds and π–π inter­actions

In the title compound, C₂₂H₁₈N₄·2H₂O, the organic fragment lies across a centre of inversion in the P2₁/n space group. The water mol­ecules form C(2)-type hydrogen-bonded chains which are linked to the 1,4-bis­(1H-benzimidazol-1-yl­methyl)­benzene mol­ecules through O—H...N hydrogen bonds, forming sheets reinforced by π–π stacking inter­actions between the aromatic rings within the layers.

S1. Comment

Benzimidazole-based organic ligands have been widely used in supramolecular coordination chemistry to generate various discrete and one- to three-dimensional coordination architectures (Wahon et al., 1994; Berends & Stephan, 1984; Su et al., 2002, 2003; Zhang, Guo, Yang, Lu et al., 2007 [Reference was originally ambiguous - please confirm]; Zheng et al., 2007; Chen et al., 2007). Bis-benzimidazole ligands, with two benzimidazole groups connected by an organic spacer at the 1-positions, can take either trans or cis conformations (Liu et al., 2007; Lü, Pan et al., 2006 [Reference was originally ambiguous - please confirm]). Besides acting as coordination donors, the imino N atoms of the two benzimidazole groups can also act as hydrogen-bond acceptors (Zheng et al., 2005). Here, we describe the title dihydrated compound, (I), which forms a hydrogen-bonded layer structure in the crystal structure displaying π–π interactions between the aromatic groups.

The organic component (Fig. 1) lies across an inversion centre, so that the asymmetric unit consists of one-half of an organic component and one water molecule. The organic molecule adopts the trans conformation, with the two benzimidazole arms arranged up and down on the two sides of the central benzene ring, showing a dihedral angle of 75.5° [with each other?] (Fig. 1). The imino N atoms of the two benzimidazole arms form O—H···N hydrogen bonds with the water molecules (Table 1; Li et al., 2007). Furthermore, the three aromatic rings are stacked in a parallel fashion, displaying π–π interactions (Chen et al., 2003; Zhang, Guo, Yang, Wang et al., 2007). Therefore, the crystal packing of the organic molecules is directed by these intermolecular interactions (Su et al., 1998, 2001; Chen et al., 2005, 2006).

One H atom of the water component is disordered over two sites, due to the presence of inversion centres relating pairs of adjacent water molecules. The water molecules are linked through O—H···O hydrogen bonds (Table 1). Each water molecule is involved in three hydrogen bonds, one of which links the molecular components via an O—H···N hydrogen bond, while the other two, involving the disordered H atom, link pairs of the water molecules. The water molecules alone are hydrogen bonded into zigzag chains along [100]. Since every two water molecules form the unit cell repeat unit of the chain, the one-dimensional water chain can be described as a C(2) chain (Infantes & Motherwell, 2002). The zigzag arrangement of the water chain is directed by the intrinsic angles of the hydrogen bonds around the water molecule. The organic molecules are connected through the O—H···N hydrogen bonds to water chains on both sides to generate two-dimensional layers parallel to (010).

The C₂₂H₁₈N₄ molecule is composed of three aromatic rings and adopts the trans conformation. The whole molecule is non-planar. The organic molecules overlap each other in the a [direction? text missing] and π–π interactions are formed between adjacent aromatic rings (Fig. 2). The centroid-to-centroid distance between the phenyl ring and the imidazole ring of an adjacent benzimidazole ring system at (-1 + x, y, z) is 3.9796 (9) Å, with an interplanar angle of 0.4 (2)°, and this interaction reinforces the hydrogen-bonded sheet.

In the ac plane, the water chains and organic arrays are aligned alternately via O—H···N hydrogen bonds to give a two-dimensional layer (Fig. 2). The layers display a weaving feature due to the trans conformation of the organic molecules. Therefore, the overall crystal packing is sustained by offset stacking of the two-dimensional layers in the b direction.

The title compound crystallizes in a slightly different way to the previously reported compound 1,4-bis(1H-benzotriazole-1-ylmethyl)benzene (Cai et al., 2004). These two compounds have rather similar molecular structures but with a modest difference between their five-membered N-heterocyclic rings. In addition, the title compound is a dihydrate, while the previously reported one is a tetrahydrate. 1,4-Bis(1H-benzotriazole-1-ylmethyl)benzene has two free N atoms to act as potential hydrogen-bond donors, although only one N atom is involved in hydrogen bonding, quite similar to the present compound. Nevertheless, 1,4-bis(1H-benzotriazole-1-ylmethyl)benzene crystallizes as a tetrahydrate adduct with the water molecules forming a one-dimensional O—H···O hydrogen-bonded tape, while in (I) the dihydrate crystallizes with the water molecules forming a C(2)-type hydrogen-bonded chain. In both cases, the organic molecules are connected by the water chain or tape in essentially the same way through O—H···N hydrogen bonds to generate similar two-dimensional layers. These results indicate that similar organic molecules can display similar intermolecular interactions, which play important roles in directing molecular arrangement and crystal packing.

In summary, co-crystallization of the non-planar linear organic molecule, 1,4-bis(benzimidazol-1-ylmethyl)benzene, and water affords a layered structure which is consolidated by cooperative O—H···O and O—H···N hydrogen bonds and π–π interactions. This is an example of the synergistic effect of different supramolecular interactions in the direction of the crystal packing, which is of significance to crystal engineering (Su et al., 1998, 2001; Lü, Qiao et al., 2006).

Related literature

For related literature, see: Berends & Stephan (1984); Cai et al. (2004); Chen et al. (2003, 2005, 2006, 2007); Infantes & Motherwell (2002); Lü, Pan, He, Cai, Kang & Su (2006); Lü, Qiao, He, Pan, Kang & Su (2006); Li et al. (2007); Liu et al. (2007); Su et al. (1998, 2001, 2002, 2003); Wahon et al. (1994); Zhang, Guo, Yang, Lu, Tong & Su (2007); Zhang, Guo, Yang, Wang, Liu, Kang & Su (2007); Zheng et al. (2005, 2007).

S2. Experimental

The title compound was prepared according the literature method of Su et al. (2003). Single crystals were grown from an ethanol solution over several days at room temperature.

S3. Refinement

Water H atoms were located in the electronic map and refined isotropically, with O—H distances restrained to about 0.86 (s.u.?) Å. Because the crystallographically imposed inversion centre is located in the middle of two adjacent water molecules, the H atom which forms the O—H···O hydrogen bond is required by symmetry to be distributed over two positions with half occupancy. All other H atoms were placed in calculated positions and included in the refinement in the riding-model approximation, with C—H distances in the range 0.95–0.99 Å [Please check added text], and with U_iso(H) = 1.5U_eq(O) for water H atoms or 1.2U_eq(C) for all other H atoms.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SMART (Bruker, 1998); data reduction: SAINT (Bruker, 1998); 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: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure and crystallographic numbering scheme for (I). Displacement ellipsoids are shown at the 30% probability level. Solvent water molecules have been omitted for clarity. Unlabelled atoms are related to labelled atoms by the symmetry code (1 - x, -y, 1 - z).
	Fig. 2. A view of the two-dimensional layers, showing hydrogen bonds and π–π interactions as dashed lines.

1,4-bis(benzimidazol-1-ylmethyl)benzene dihydrate

Crystal data

C22H18N4·2H2O	F(000) = 396
Mr = 374.44	Dx = 1.305 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 7740 reflections
a = 5.4040 (2) Å	θ = 3.1–28°
b = 10.7114 (4) Å	µ = 0.09 mm^−1
c = 16.5003 (5) Å	T = 150 K
β = 94.079 (3)°	Block, colourless
V = 952.69 (6) Å^3	0.25 × 0.20 × 0.18 mm
Z = 2

Data collection

Bruker SMART 1K CCD area-detector diffractometer	2275 independent reflections
Radiation source: fine-focus sealed tube	1412 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.027
ϕ and ω scans	θmax = 28.0°, θmin = 3.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −7→7
Tmin = 0.964, Tmax = 0.985	k = −14→14
7740 measured reflections	l = −21→17

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)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.120	Only H-atom coordinates refined
S = 1.03	w = 1/[σ^2(Fo^2) + (0.068P)^2] where P = (Fo^2 + 2Fc^2)/3
2275 reflections	(Δ/σ)max = 0.001
127 parameters	Δρmax = 0.53 e Å^−3
6 restraints	Δρmin = −0.31 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	Occ. (<1)
N1	0.2344 (2)	0.68189 (11)	0.67908 (7)	0.0291 (3)
N2	0.2076 (2)	0.63342 (11)	0.81060 (7)	0.0353 (3)
C1	0.3129 (3)	0.67456 (14)	0.59626 (8)	0.0342 (4)
H1A	0.4877	0.6465	0.5979	0.041*
H1B	0.3033	0.7586	0.5713	0.041*
C2	0.3247 (3)	0.61432 (14)	0.74455 (8)	0.0344 (4)
H2	0.4604	0.5583	0.7427	0.041*
C3	0.0251 (3)	0.71987 (13)	0.78666 (8)	0.0301 (3)
C4	−0.1576 (3)	0.77382 (15)	0.83115 (9)	0.0379 (4)
H4	−0.1707	0.7537	0.8868	0.046*
C5	−0.3181 (3)	0.85728 (15)	0.79147 (10)	0.0429 (4)
H5	−0.4438	0.8954	0.8204	0.052*
C6	−0.3005 (3)	0.88723 (14)	0.70959 (10)	0.0397 (4)
H6	−0.4144	0.9453	0.6844	0.048*
C7	−0.1221 (3)	0.83471 (13)	0.66454 (9)	0.0326 (4)
H7	−0.1098	0.8552	0.6089	0.039*
C8	0.0380 (3)	0.75078 (12)	0.70446 (8)	0.0277 (3)
C9	0.1527 (3)	0.58523 (13)	0.54475 (8)	0.0284 (3)
C10	−0.0533 (3)	0.62584 (14)	0.49686 (8)	0.0331 (4)
H10	−0.0913	0.7124	0.4942	0.040*
C11	0.2037 (3)	0.45811 (14)	0.54686 (8)	0.0330 (4)
H11	0.3444	0.4284	0.5789	0.040*
O1	0.2470 (3)	0.52830 (15)	0.97150 (7)	0.0822 (5)
H1E	0.2471	0.5561	0.9219	0.123*
H1D	0.1149	0.5211	0.9955	0.123*	0.50
H1C	0.3922	0.5109	0.9937	0.123*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0278 (7)	0.0323 (7)	0.0271 (6)	−0.0028 (5)	0.0012 (5)	−0.0040 (5)
N2	0.0386 (8)	0.0354 (7)	0.0310 (7)	−0.0074 (6)	−0.0028 (6)	0.0014 (5)
C1	0.0332 (8)	0.0407 (9)	0.0294 (8)	−0.0068 (7)	0.0082 (6)	−0.0043 (6)
C2	0.0325 (9)	0.0342 (8)	0.0357 (9)	−0.0022 (7)	−0.0039 (7)	−0.0012 (6)
C3	0.0319 (8)	0.0305 (7)	0.0276 (7)	−0.0093 (7)	−0.0004 (6)	−0.0028 (6)
C4	0.0406 (10)	0.0430 (9)	0.0311 (8)	−0.0143 (8)	0.0093 (7)	−0.0091 (7)
C5	0.0365 (9)	0.0419 (10)	0.0516 (10)	−0.0062 (8)	0.0114 (8)	−0.0184 (8)
C6	0.0361 (9)	0.0312 (8)	0.0515 (10)	−0.0004 (7)	0.0005 (7)	−0.0099 (7)
C7	0.0371 (9)	0.0286 (8)	0.0315 (8)	−0.0053 (7)	−0.0016 (6)	−0.0013 (6)
C8	0.0287 (8)	0.0274 (7)	0.0273 (7)	−0.0071 (7)	0.0032 (6)	−0.0051 (6)
C9	0.0302 (8)	0.0330 (8)	0.0229 (7)	−0.0021 (6)	0.0085 (6)	−0.0020 (6)
C10	0.0416 (9)	0.0299 (8)	0.0280 (7)	0.0034 (7)	0.0042 (7)	−0.0006 (6)
C11	0.0323 (9)	0.0388 (9)	0.0277 (7)	0.0076 (7)	−0.0003 (6)	−0.0023 (6)
O1	0.1175 (13)	0.0926 (11)	0.0346 (7)	0.0164 (9)	−0.0081 (7)	0.0086 (7)

Geometric parameters (Å, º)

N1—C2	1.3616 (18)	C5—H5	0.9500
N1—C8	1.3821 (17)	C6—C7	1.379 (2)
N1—C1	1.4614 (17)	C6—H6	0.9500
N2—C2	1.3144 (17)	C7—C8	1.382 (2)
N2—C3	1.3895 (19)	C7—H7	0.9500
C1—C9	1.5107 (19)	C9—C10	1.389 (2)
C1—H1A	0.9900	C9—C11	1.389 (2)
C1—H1B	0.9900	C10—C11^i	1.380 (2)
C2—H2	0.9500	C10—H10	0.9500
C3—C4	1.397 (2)	C11—C10^i	1.380 (2)
C3—C8	1.4028 (19)	C11—H11	0.9500
C4—C5	1.378 (2)	O1—H1E	0.8718
C4—H4	0.9500	O1—H1D	0.8436
C5—C6	1.398 (2)	O1—H1C	0.8625
C2—N1—C8	106.43 (11)	C7—C6—C5	121.71 (16)
C2—N1—C1	127.02 (12)	C7—C6—H6	119.1
C8—N1—C1	126.31 (12)	C5—C6—H6	119.1
C2—N2—C3	104.00 (12)	C6—C7—C8	116.53 (14)
N1—C1—C9	111.56 (11)	C6—C7—H7	121.7
N1—C1—H1A	109.3	C8—C7—H7	121.7
C9—C1—H1A	109.3	C7—C8—N1	132.16 (13)
N1—C1—H1B	109.3	C7—C8—C3	122.83 (13)
C9—C1—H1B	109.3	N1—C8—C3	105.01 (12)
H1A—C1—H1B	108.0	C10—C9—C11	118.09 (13)
N2—C2—N1	114.13 (14)	C10—C9—C1	121.73 (13)
N2—C2—H2	122.9	C11—C9—C1	120.13 (14)
N1—C2—H2	122.9	C11^i—C10—C9	120.77 (13)
N2—C3—C4	129.81 (13)	C11^i—C10—H10	119.6
N2—C3—C8	110.43 (12)	C9—C10—H10	119.6
C4—C3—C8	119.75 (14)	C10^i—C11—C9	121.13 (14)
C5—C4—C3	117.60 (14)	C10^i—C11—H11	119.4
C5—C4—H4	121.2	C9—C11—H11	119.4
C3—C4—H4	121.2	H1E—O1—H1D	121.9
C4—C5—C6	121.59 (15)	H1E—O1—H1C	114.3
C4—C5—H5	119.2	H1D—O1—H1C	123.8
C6—C5—H5	119.2

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—H1C···O1^ii	0.86	2.04	2.892 (3)	171.1
O1—H1D···O1^iii	0.84	2.13	2.955 (4)	164.5
O1—H1E···N2	0.87	2.01	2.8778 (17)	172.4

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