catena-Poly[[dichloridomercury(II)]-μ-1-(2-pyridylmeth­yl)-1H-benzotri­azole]: the effect of different metal centers on the self-assembly of coordination complexes

To further investigate the relationship between the structures of benzotriazol-1-yl-based pyridyl ligands and their complexes, a new linear one-dimensional Hg^II coordination polymer, [HgCl₂(C₁₂H₁₀N₄)]_n, with the 1-(2-pyridylmeth­yl)-1H-benzotriazole (L) ligand was obtained through the reaction of L with HgCl₂. In this complex, each Hg^II center within the one-dimensional chain is coordinated by two chloride anions as well as by one pyridine and one benzotriazole N-atom donor of two distinct L ligands in a distorted tetra­hedral geometry, forming a linear one-dimensional chain running along the [010] direction. Weak C—H...π and π–π stacking inter­actions link the one-dimensional motifs to generate an overall two-dimensional network parallel to the (100) plane. Comparison of the structural differences with previous findings suggests that the presence of different metal centers may plays an important role in the construction of such supra­molecular frameworks.

S1. Comment

In recent years, increasing attention has been focused on the construction of coordination polymers, also known as metal-organic frameworks (Janiak, 2003; Robin & Fromm, 2006). The rational engineering and controlled preparation of such novel coordination polymers are currently of great interest in coordination and supramolecular chemistry because of their interesting topologies (Chen et al., 2006; Hill et al., 2005; Kitagawa et al., 2004; Liu, Chang et al., 2008; Steel, 2005; Wang et al., 2008; Yaghi et al., 2003) and potential uses as functional materials (Bu et al., 2004; Hou et al., 2005; Liu, Sañudo et al., 2008; Liu, Wang et al., 2007; Tao et al., 2008). One of the most successful strategies for constructing such complexes has been the assembly reaction of different metal ions (as nodes) with well designed organic ligands (as building blocks), which, so far, has been at an evolutionary stage with the current focus mainly laid on understanding the factors that determine the crystal packing, as well as on exploring relevant potential properties (Chen et al., 2006; Du et al., 2007; Liu, Shi et al., 2006; Zou et al., 2006). In addition, various intra- and/or inter-molecular weak interactions, such as π–π stacking (Janiak, 2000) and C—H···π (Sony & Ponnuswamy, 2006) and C—H···X (X = O, N, S, F, Cl, Br, I and so on) hydrogen-bonding (Desiraju & Steiner, 1999) interactions also affect the final structures of coordination complexes, especially in the aspect of linking the multi-nuclear discrete subunits or low-dimensional motifs into higher-dimensional frameworks.

Numerous related bis-heterocyclic chelating or bridging ligands have been synthesized and have been used extensively to construct functional coordination complexes that contain different hetero-aromatic ring systems, for example pyridine, pyrazine, quinoline, quinoxaline, pyrazole, imidazole, thiazoles and their benzo analogues (Constable, 1989; Constable & Steel, 1989; Steel, 2005). As such, we have found that Richardson & Steel (2003) have initially reported studies concerning five N-containing bis-heterocyclic ligands bearing 1-substituted benzotriazole subunits. In our previous work, we have also reported the preparation of a nonplanar flexible benzotriazol-1-yl-based pyridyl ligand, namely 1-(4-pyridylmethyl)-1H-benzotriazole (4pbt). Its reaction with AgNO₃ led to a one-dimensional double-helical coordination polymer, {[Ag(4pbt)](NO₃)}_n, formed by C–H···π supramolecular interactions between adjacent single-helical chains (Liu, Sun et al., 2008). The results therein indicated that the N-donor spatial position of the pendant pyridyl group in such benzotriazol-1-yl-based pyridyl ligands, as compared with the previous finding (Richardson & Steel, 2003), played an important role on the final structures of relevant coordination complexes. As part of a study on the coordination possibilities of benzotriazole-based ligands with different metal centers in the self-assembly process of coordination complexes, we have chosen sequentially the ligand 1-(2-pyridylmethyl)-1H-benzotriazole (L) to construct a new one-dimensional Hg^II complex though its reaction with HgCl₂ under a conventional solution method. We report here the crystal structure of [Hg(L)Cl₂]_n, (I), and briefly discuss the effect of the coordination geometry of different metal centers on the structures of the relevant coordination complexes.

The crystal structure of (I) consists of one-dimensional linear neutral chains, [Hg(L)Cl₂]_n(Fig. 1). In each one-dimensional chain, there exist only one kind of crystallographically independent Hg^II center, which is four-coordinated by two Cl^- anions and two N-atom donors, one from the benzotriazole ring of one L ligand and the other from the pyridine ring of another distinct L ligand. The Hg—N and Hg—Cl bond distances as well as the bond angles around each Hg^II center (Table 1) are within the expected range for such complexes (Orpen et al., 1989; Wang et al., 2007). The coordination geometry around the Hg^II center can be described as a distorted tetrahedron. Each L ligand takes a µ₂-bridging coordination mode to connect the Hg^II centers, generating a perfect linear chain along the [010] direction, with adjacent Hg atoms separated by a b-axis translation [Hg···Hg = b = 8.8723 (18) Å]. Moreover, adjacent one-dimensional chains are linked together to form an overall two-dimensional sheet running parallel to the (100) plane (Fig. 2) by the co-effects of inter-chain π–π stacking interactions between completely parallel benzotriazole rings of adjacent L ligands [the centroid–centroid separation is 3.706 (5) Å and the average interplanar separation 3.4494 Å] (Janiak, 2000)] and C—H···π supramolecular interactions involving the C7–C12 phenyl rings of the L ligand (centroid Cg1, see Table 2) (Sony & Ponnuswamy, 2006). Thus, the various intra- or intermolecular weak interactions mentioned above play an important role in the formation of (I), especially in the aspect of linking the low-dimensional motifs into higher-dimensional supramolecular networks.

To explore the coordination possibilities of relevant benzotriazol-1-yl-based pyridyl bis-heterocyclic ligands, Richardson & Steel (2003) synthesized L and selected four different types of metal centers with different coordination geometries as representative subjects for coordination with it. A mononuclear complex, [Ru(L)(bpy)₂Cl]PF₆ (bpy is 2,2'-bipyridine), and a dinuclear complex, [Pd₂(L)₂Cl₄], with an intramolecular Pd—Pd separation of 6.739 (1) Å, were obtained, while Ru^II and Pd^II were chosen as examples of stereoregular octahedral and square-planar metals to react with L. In addition, Cu^II (Melnik et al., 2000) and Ag^I (Munakata, et al., 1998) centers have also been proved very popular in recent years and been widely employed as the components for the construction of diverse coordination architectures with various N-containing heterocyclic ligands. For example, the previously reported metal–organic coordination architectures constructed from ligand L also include two centrosymmetric dinuclear complexes, [Cu(L)]₂Cl₄ and [Ag(L)]₂(NO₃)₂, where Cu^II and Ag^I were selected as examples of metals that have more flexible coordination numbers and geometries (Richardson & Steel, 2003). In this contribution, when we used HgCl₂ to react with L under the conventional solution conditions, a perfect one-dimensional linear coordination polymer, [Hg(L)Cl₂]_n, (I), was produced, in which the coordination geometry around the Hg^II center can be described as a distorted tetrahedron. Thus, in comparision with the previous finding, the present work reveals that the coordination geometry of different metal centers could play an important role on the final structures of relevant coordination complexes. This fact may offer the means to construct coordination architectures with potentially useful properties just by variation of the metal center.

Related literature

For related literature, see: Bu et al. (2004); Chen et al. (2006); Constable & Steel (1989); Desiraju & Steiner (1999); Du et al. (2007); Hill et al. (2005); Hou et al. (2005); Janiak (2000, 2003); Kitagawa et al. (2004); Liu et al. (2006, 2007); Liu, Chang, Wang, Yan, Bu & Batten (2008); Liu, Sañudo, Wang, Chang, Yan & Bu (2008); Liu, Sun, Li, Guo, Zhou & Fang (2008); Melnik et al. (2000); Munakata et al. (1998); Orpen et al. (1989); Richardson & Steel (2003); Robin & Fromm,(2006). Sony & Ponnuswamy (2006); Steel (2005); Tao et al. (2008); Wang et al. (2007, 2008); Yaghi et al. (2003); Zou et al. (2006).

S2. Experimental

The ligand L was synthesized according to the method reported by Liu, Sun et al. (2008). A solution of HgCl₂ (0.1 mmol) in a mixture of CH₃OH (15 ml) and CH₃CN (5 ml) was added to L (0.1 mmol). The yellow solid that formed was filtered off, and the resulting solution was kept at room temperature. Yellow single crystals of complex (I) suitable for X-ray analysis were obtained by slow evaporation of the solvent after several days (yield ~40%). Elemental analysis calculated for C₁₂H₁₀Cl₂HgN₄: C 29.92, H 2.09, N 11.63%; found: C 29.81, H 2.17, N 11.51%.

S3. Refinement

H atoms were included in calculated positions and treated in the subsequent refinement as riding atoms [C—H = 0.93 (aromatic) or 0.97 Å (methylene), with U_iso(H) = 1.2U_eq(C)]. The position of the highest peak is at (0.4051, 0.7210, 0.1189) (1.43 Å from H2). The position of the deepest hole is at (0.3568, 0.5704, 0.7213) (0.92 Å from Hg1).

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (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) and PLATON (Spek, 2003).

Figures

	Fig. 1. The one-dimensional molecular structure of (I) with the atom-numbering scheme, viewed along the b axis. Displacement ellipsoids are drawn at the 30% probability level and atoms labeled with the suffix A are generated by the symmetry operation (x, y + 1, z).
	Fig. 2. The two-dimensional network, running parallel to the (100) plane, formed by inter-chain π–π stacking (solid dashed lines) and C–H···π (open dashed lines) interactions. For clarity, only H atoms involved in the interactions are shown.

catena-Poly[[dichloridomercury(II)]-µ-1-(2-pyridylmethyl)- 1H-benzotriazole]

Crystal data

[HgCl2(C12H10N4)]	Z = 2
Mr = 481.73	F(000) = 448
Triclinic, P1	Dx = 2.307 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.8769 (16) Å	Cell parameters from 2303 reflections
b = 8.8723 (18) Å	θ = 1.9–28.0°
c = 11.130 (2) Å	µ = 11.47 mm^−1
α = 102.88 (3)°	T = 293 K
β = 98.22 (3)°	Block, yellow
γ = 109.70 (3)°	0.19 × 0.17 × 0.12 mm
V = 693.4 (3) Å^3

Data collection

Bruker P4 diffractometer	2444 independent reflections
Radiation source: fine-focus sealed tube	2190 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.081
ω scans	θmax = 25.0°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.131, Tmax = 0.257	k = −10→10
6923 measured reflections	l = −13→13

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.052	H-atom parameters constrained
wR(F^2) = 0.120	w = 1/[σ^2(Fo^2) + (0.0432P)^2 + 5.424P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.001
2444 reflections	Δρmax = 2.13 e Å^−3
173 parameters	Δρmin = −1.85 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0059 (9)

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
Hg1	0.53129 (6)	0.42782 (5)	0.29481 (4)	0.0414 (2)
C1	0.718 (2)	0.3400 (16)	0.0518 (11)	0.053 (3)
H1	0.7012	0.4385	0.0506	0.063*
C2	0.771 (2)	0.2638 (18)	−0.0485 (13)	0.062 (4)
H2	0.7853	0.3076	−0.1166	0.074*
C3	0.8018 (18)	0.1208 (17)	−0.0466 (11)	0.051 (3)
H3	0.8425	0.0680	−0.1117	0.061*
C4	0.7708 (16)	0.0572 (14)	0.0550 (10)	0.039 (3)
H4	0.7854	−0.0420	0.0571	0.047*
C5	0.7180 (13)	0.1428 (12)	0.1533 (9)	0.030 (2)
C6	0.687 (2)	0.0873 (15)	0.2679 (12)	0.052 (3)
H61	0.7502	0.1829	0.3426	0.063*
H62	0.5549	0.0495	0.2650	0.063*
C7	0.9273 (15)	−0.0380 (12)	0.3215 (9)	0.033 (2)
C8	1.0996 (16)	0.0931 (14)	0.3644 (11)	0.041 (3)
H8	1.1147	0.2030	0.3691	0.049*
C9	1.2472 (18)	0.0486 (16)	0.3997 (11)	0.049 (3)
H9	1.3655	0.1322	0.4295	0.059*
C10	1.2270 (17)	−0.1176 (15)	0.3929 (10)	0.044 (3)
H10	1.3308	−0.1406	0.4187	0.052*
C11	1.0565 (17)	−0.2445 (15)	0.3487 (10)	0.042 (3)
H11	1.0420	−0.3549	0.3412	0.050*
C12	0.9041 (15)	−0.2025 (12)	0.3151 (10)	0.033 (2)
N1	0.6897 (12)	0.2840 (10)	0.1506 (8)	0.034 (2)
N2	0.7492 (13)	−0.0457 (11)	0.2813 (8)	0.037 (2)
N3	0.6292 (13)	−0.2019 (11)	0.2552 (9)	0.041 (2)
N4	0.7158 (13)	−0.2982 (11)	0.2734 (9)	0.042 (2)
Cl1	0.7113 (4)	0.4535 (4)	0.4912 (3)	0.0465 (7)
Cl2	0.2573 (5)	0.3545 (4)	0.1442 (3)	0.0580 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Hg1	0.0473 (4)	0.0295 (3)	0.0469 (3)	0.0154 (2)	0.0012 (2)	0.0153 (2)
C1	0.082 (10)	0.045 (7)	0.044 (7)	0.033 (7)	0.023 (7)	0.019 (6)
C2	0.077 (10)	0.070 (10)	0.053 (8)	0.031 (8)	0.030 (7)	0.033 (7)
C3	0.057 (8)	0.072 (9)	0.030 (6)	0.037 (7)	0.004 (5)	0.010 (6)
C4	0.053 (7)	0.037 (6)	0.032 (5)	0.028 (6)	0.002 (5)	0.008 (5)
C5	0.025 (5)	0.026 (5)	0.037 (5)	0.012 (4)	−0.005 (4)	0.006 (4)
C6	0.083 (10)	0.040 (7)	0.059 (8)	0.039 (7)	0.033 (7)	0.029 (6)
C7	0.040 (6)	0.028 (5)	0.024 (5)	0.006 (5)	0.007 (4)	0.005 (4)
C8	0.041 (7)	0.026 (6)	0.049 (6)	0.006 (5)	0.008 (5)	0.014 (5)
C9	0.047 (7)	0.055 (8)	0.037 (6)	0.009 (6)	0.004 (5)	0.018 (6)
C10	0.050 (7)	0.052 (7)	0.028 (5)	0.017 (6)	0.004 (5)	0.016 (5)
C11	0.055 (8)	0.040 (6)	0.044 (6)	0.027 (6)	0.010 (6)	0.027 (5)
C12	0.045 (6)	0.027 (5)	0.036 (5)	0.019 (5)	0.008 (5)	0.018 (5)
N1	0.042 (5)	0.028 (5)	0.037 (5)	0.019 (4)	0.007 (4)	0.012 (4)
N2	0.046 (6)	0.030 (5)	0.043 (5)	0.018 (4)	0.014 (4)	0.018 (4)
N3	0.045 (6)	0.032 (5)	0.050 (6)	0.013 (5)	0.007 (5)	0.025 (4)
N4	0.045 (6)	0.026 (5)	0.054 (6)	0.014 (4)	−0.001 (5)	0.017 (4)
Cl1	0.0564 (19)	0.0404 (16)	0.0407 (15)	0.0247 (14)	−0.0058 (13)	0.0098 (12)
Cl2	0.0479 (19)	0.056 (2)	0.0594 (19)	0.0164 (16)	−0.0124 (15)	0.0174 (16)

Geometric parameters (Å, º)

Hg1—Cl2	2.329 (3)	C6—H62	0.9700
Hg1—Cl1	2.348 (3)	C7—N2	1.384 (14)
Hg1—N4^i	2.460 (9)	C7—C8	1.388 (15)
Hg1—N1	2.548 (9)	C7—C12	1.392 (14)
C1—N1	1.321 (15)	C8—C9	1.381 (17)
C1—C2	1.364 (18)	C8—H8	0.9300
C1—H1	0.9300	C9—C10	1.412 (17)
C2—C3	1.374 (18)	C9—H9	0.9300
C2—H2	0.9300	C10—C11	1.363 (16)
C3—C4	1.388 (17)	C10—H10	0.9300
C3—H3	0.9300	C11—C12	1.399 (15)
C4—C5	1.385 (14)	C11—H11	0.9300
C4—H4	0.9300	C12—N4	1.384 (14)
C5—N1	1.351 (12)	N2—N3	1.325 (12)
C5—C6	1.489 (15)	N3—N4	1.291 (12)
C6—N2	1.452 (13)	N4—Hg1^ii	2.460 (9)
C6—H61	0.9700
Cl2—Hg1—Cl1	155.58 (13)	N2—C7—C12	104.4 (9)
Cl2—Hg1—N4^i	100.9 (2)	C8—C7—C12	122.5 (11)
Cl1—Hg1—N4^i	97.6 (2)	C9—C8—C7	115.2 (11)
Cl2—Hg1—N1	97.1 (2)	C9—C8—H8	122.4
Cl1—Hg1—N1	98.4 (2)	C7—C8—H8	122.4
N4^i—Hg1—N1	91.1 (3)	C8—C9—C10	123.2 (11)
N1—C1—C2	124.7 (12)	C8—C9—H9	118.4
N1—C1—H1	117.7	C10—C9—H9	118.4
C2—C1—H1	117.7	C11—C10—C9	120.5 (12)
C1—C2—C3	118.5 (12)	C11—C10—H10	119.8
C1—C2—H2	120.8	C9—C10—H10	119.8
C3—C2—H2	120.8	C10—C11—C12	117.5 (11)
C2—C3—C4	118.3 (11)	C10—C11—H11	121.2
C2—C3—H3	120.8	C12—C11—H11	121.2
C4—C3—H3	120.8	N4—C12—C7	107.2 (9)
C5—C4—C3	119.4 (10)	N4—C12—C11	131.8 (10)
C5—C4—H4	120.3	C7—C12—C11	121.0 (10)
C3—C4—H4	120.3	C1—N1—C5	117.5 (10)
N1—C5—C4	121.5 (10)	C1—N1—Hg1	114.8 (7)
N1—C5—C6	115.1 (9)	C5—N1—Hg1	126.7 (7)
C4—C5—C6	123.5 (9)	N3—N2—C7	109.5 (8)
N2—C6—C5	114.6 (9)	N3—N2—C6	121.0 (10)
N2—C6—H61	108.6	C7—N2—C6	129.5 (9)
C5—C6—H61	108.6	N4—N3—N2	110.2 (9)
N2—C6—H62	108.6	N3—N4—C12	108.7 (8)
C5—C6—H62	108.6	N3—N4—Hg1^ii	117.1 (7)
H61—C6—H62	107.6	C12—N4—Hg1^ii	130.8 (6)
N2—C7—C8	133.1 (10)
N1—C1—C2—C3	−2 (2)	C4—C5—N1—Hg1	166.6 (8)
C1—C2—C3—C4	3 (2)	C6—C5—N1—Hg1	−12.9 (13)
C2—C3—C4—C5	−2.8 (18)	Cl2—Hg1—N1—C1	60.9 (8)
C3—C4—C5—N1	2.3 (16)	Cl1—Hg1—N1—C1	−138.0 (8)
C3—C4—C5—C6	−178.3 (12)	N4^i—Hg1—N1—C1	−40.2 (9)
N1—C5—C6—N2	−169.3 (10)	Cl2—Hg1—N1—C5	−107.4 (8)
C4—C5—C6—N2	11.2 (17)	Cl1—Hg1—N1—C5	53.7 (8)
N2—C7—C8—C9	178.1 (11)	N4^i—Hg1—N1—C5	151.5 (8)
C12—C7—C8—C9	0.5 (16)	C8—C7—N2—N3	−177.0 (11)
C7—C8—C9—C10	0.2 (17)	C12—C7—N2—N3	0.9 (11)
C8—C9—C10—C11	0.7 (18)	C8—C7—N2—C6	2.2 (19)
C9—C10—C11—C12	−2.1 (16)	C12—C7—N2—C6	−179.9 (10)
N2—C7—C12—N4	−0.6 (11)	C5—C6—N2—N3	−104.0 (12)
C8—C7—C12—N4	177.6 (10)	C5—C6—N2—C7	76.8 (15)
N2—C7—C12—C11	179.8 (10)	C7—N2—N3—N4	−1.0 (12)
C8—C7—C12—C11	−2.0 (16)	C6—N2—N3—N4	179.8 (10)
C10—C11—C12—N4	−176.8 (11)	N2—N3—N4—C12	0.6 (12)
C10—C11—C12—C7	2.7 (16)	N2—N3—N4—Hg1^ii	162.2 (7)
C2—C1—N1—C5	1.3 (19)	C7—C12—N4—N3	0.0 (12)
C2—C1—N1—Hg1	−168.2 (12)	C11—C12—N4—N3	179.6 (11)
C4—C5—N1—C1	−1.5 (15)	C7—C12—N4—Hg1^ii	−158.2 (7)
C6—C5—N1—C1	179.1 (11)	C11—C12—N4—Hg1^ii	21.3 (18)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···Cg1^iii	0.93	2.90	3.688 (3)	143

Symmetry code: (iii) −x+2, −y, −z.