A fivefold inter­penetrating diamond-like three-dimensional metal–organic framework: poly[(μ₂-benzene-1,4-di­acetato)[μ₂-1,6-bis­(1,2,4-triazol-1-yl)hexa­ne]zinc(II)]

In the mixed-ligand metal–organic title polymeric compound, [Zn(C₁₀H₈O₄)(C₁₀H₁₆N₆)]_n or [Zn(PBEA)(BTH)]_n [H₂PBEA is benzene-1,4-diacetic acid and BTH is 1,6-bis­(1,2,4-triazol-1-yl)hexane], the asymmetric unit contains a Zn^II atom, one half of a BTH ligand and one half of a doubly deprotonated H₂PBEA ligand. Each Zn^II centre lies on a crystallographic twofold rotation axis and is four-coordinated by two O atoms from two distinct PBEA²⁻ ligands and two N atoms from two different BTH ligands in a {ZnO₂N₂} coordination environment. The three-dimensional topology of the title compound corresponds to that of a fivefold inter­penetrating diamond-like metal–organic framework.

S1. Comment

In the past decades, metal–organic frameworks (MOFs) have been [become?] highly attractive [to researchers?] not only because of their intriguing topology matrices but also because of their potential applications in gas storage, chemical separations, molecular magnetism, nonlinear optics and heterogeneous catalysis (Kitagawa et al., 2004; Ferey et al., 2005; Roy et al., 2009; Li et al., 2012). It is known that the construction of metal–organic compounds is usually influenced by many factors in the self-assembly process, such as metal ions, flexibility or rigidity of the ligands, counterions, solvents, temperature and reaction conditions (Kan et al., 2012; Liu et al., 2012). Among these parameters, the nature of the organic ligands is a key factor in determining the network structure of a compound. In this regard, flexible ligands coordinating to metal centers may bend or rotate to adopt the appropriate [different?] conformations and often form novel metal–organic frameworks.

The flexible dicarboxylate derived from benzene-1,4-diacetic acid (H₂PBEA) is a very versatile ligand for the construction of novel metal–organic frameworks (Pan et al.., 2003; Braverman & LaDuca, 2007; Wang et al., 2008). Additionally, because of the presence of a flexible –(CH₂)₆– group in the molecule, 1,6-bis(1,2,4-triazol-1-yl)hexane (BTH) can adopt different conformations compared with the corresponding 1,2,4-triazole ligand (Liang et al., 2009; Zhou et al., 2009; Pang et al., 2011; Liu et al., 2012). In our previous work, we have synthesized two compounds based on H₂PBEA and BTB [BTB= 1,4-bis(1,2,4-triazol-1-yl)butane] (Wang, Tao et al., 2011; Wang, Xu et al., 2011). In order to further investigate the coordination chemistry of flexible bis(triazole) ligands, we have selected H₂PBEA and BTH as organic ligands, generating the new Zn^II coordination polymer, [Zn(C₁₀H₁₆N₆)(C₁₀H₈O₄)]_n, (I), the crystal structure of which we now report.

Compound (I) crystallizes in the monoclinic space group C2/c, and the asymmetric unit consists of a Zn^II atom, one half of a BTH ligand and one half of a fully deprotonated H₂PBEA ligand. Each Zn^II center on a crystallographic twofold axis possesses a {ZnO₂N₂} coordination environment, with two triazole nitrogen donor atoms from two BTH ligands and two oxygen donor atoms from monodentate carboxylate groups belonging to two different PBEA^2- ligands [Zn1—O1=1.960 (2), Zn1—N1=2.031 (2) Å] (Fig. 1). A possible distortion of tetrahedral geometry may be quantified by the ι₄ parameter; this indicator adopts values of 0 for perfect square-planar coordination and 1 for tetrahedral geometry (Yang et al., 2007). In (I), ι₄ for Zn1 equals 0 and indicates undistorted tetrahedral coordination. The average Zn—O and Zn—N distances in compound (I) are comparable to those in reported Zn-based compounds (Blake et al., 2011; Luo et al., 2012). In compound (I), BTH exhibits a trans–trans–trans–trans–trans conformation with a dihedral angle of 0° between the triazole rings for symmetry reasons. The torsion angles N2—N3—C8—C9 and N2ⁱⁱ—N3ⁱⁱ—C8ⁱⁱ—C9ⁱⁱ are -75.8 (4) and -75.8 (4)°, respectively [symmetry code: (ii) 1.5 - x, 2.5 - y, 1 - z.]. In the PBEA^2- ligand, the dihedral angles between the carboxylate groups and their corresponding phenyl rings are 67.1 (2) and 67.1 (2)°. Each Zn^II cation is connected by four linear ligands (including two PBEA^2- and two BTH) extending into a three-dimensional diamondoid framework (Fig. 2). Distances between next-neighbor cations bridged by PBEA^2- and BTH amount to 11.899 (1) and 16.481 (1) Å, respectively. The long spacers between the coordination sites of PBEA^2- and BTH result in large cavities within the diamondoid cages. In the absence of large guest molecules to fill the void space, the potential voids are filled via mutual interpenetration with four additional independent equivalent frameworks, generating a fivefold interpenetrating three-dimensional architecture (Fig. 3). Worthy of mention is that the interpenetration mode belongs to a class Ia fivefold interpenetration and the translational degree of interpenetration (Z_t) of the structure is 5 as revealed with the program TOPOS (Blatov et al., 2000). This means that the overall network structure can be categorized into five topologically equivalent three-dimensional subsets, which are related by the translation vector [0, 1, 0]. The separated distance from one subset to another interpenetrating one is 5.970 (3) Å. Furthermore, there are two types of non-classical hydrogen-bond interactions (C4—H4···O2^iv, C6—H6···N2^v) in compound (I) (Table 1) [symmetry codes: (iv) x, y - 1, z; (v) 1.5 - x, -0.5 + y, 1.5 - z].

In conclusion, we have synthesized a fivefold interpenetrating diamond-like three-dimensional metal–organic framework.

Related literature

For related literature, see: Blake et al. (2011); Blatov et al. (2000); Braverman & LaDuca (2007); Ferey et al. (2005); Kan et al. (2012); Kitagawa et al. (2004); Li et al. (2012); Liang et al. (2009); Liu et al. (2012); Luo et al. (2012); Pan et al. (2003); Pang et al. (2011); Roy et al. (2009); Wang et al. (2008); Wang, Tao & Xu (2011); Wang, Xu & Tao (2011); Yang et al. (2007); Zhou et al. (2009).

S2. Experimental

A mixture of Zn(NO₃)₂.6H₂O (29.7 mg, 0.1 mmol), H₂PBEA (19.5 mg, 0.1 mmol), BTH (44.1 mg, 0.2 mmol) and KOH (11.2 mg, 0.2 mmol) in H₂O (10 ml) was sealed in a 16 ml Teflon-lined stainless steel container and heated at 393 K for 72 h. After cooling to room temperature, colorless block-shaped crystals of (I) were collected by filtration and washed several times with water and ethanol (yield 33.8%, based on H₂PBEA). Elemental analysis for C₂₀H₂₄N₆O₄Zn (M_r = 477.84): C 50.27, H 5.06, N 17.59%; found: C 50.42, H 5.08, N 17.64%.

S3. Refinement

H atoms bonded to C atoms were placed in calculated positions and treated using a riding-model, with C—H = 0.93 (triazole and benzene), or 0.97 Å (methylene), 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: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A view of the local coordination of the Zn^II cations in compound (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry code: (iii) 2 - x, y, 1.5 - z.]
	Fig. 2. View of the three-dimensional framework of compound (I).
	Fig. 3. Schematic representation of the fivefold interpenetrating three-dimensional diamond net.

Poly[(µ₂-benzene-1,4-diacetato)[µ₂-1,6-bis(1,2,4-triazol-1-yl)hexane]zinc(II)]

Crystal data

[Zn(C10H8O4)(C10H16N6)]	F(000) = 992
Mr = 477.84	Dx = 1.500 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 2237 reflections
a = 16.203 (2) Å	θ = 2.1–22.3°
b = 5.9721 (9) Å	µ = 1.20 mm^−1
c = 22.156 (3) Å	T = 296 K
β = 99.223 (2)°	Block, colourless
V = 2116.2 (5) Å^3	0.21 × 0.19 × 0.18 mm
Z = 4

Data collection

CCD area-detector diffractometer	2080 independent reflections
Radiation source: fine-focus sealed tube	1713 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
ϕ and ω scans	θmax = 26.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 2000)	h = −17→19
Tmin = 0.777, Tmax = 0.806	k = −6→7
5464 measured reflections	l = −27→26

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.094	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0465P)^2 + 0.7307P] where P = (Fo^2 + 2Fc^2)/3
2080 reflections	(Δ/σ)max < 0.001
141 parameters	Δρmax = 0.48 e Å^−3
0 restraints	Δρmin = −0.28 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
C1	0.92274 (17)	0.2330 (5)	0.84422 (12)	0.0391 (7)
C2	0.88466 (17)	0.0736 (5)	0.88584 (12)	0.0421 (7)
H2A	0.8326	0.1359	0.8946	0.050*
H2B	0.8722	−0.0682	0.8650	0.050*
C3	0.94374 (16)	0.0341 (5)	0.94545 (11)	0.0358 (6)
C4	0.98100 (18)	−0.1715 (5)	0.95890 (12)	0.0415 (7)
H4	0.9686	−0.2892	0.9314	0.050*
C5	1.03637 (18)	−0.2060 (5)	1.01237 (12)	0.0432 (7)
H5	1.0607	−0.3462	1.0203	0.052*
C6	0.83168 (17)	0.6196 (5)	0.72493 (13)	0.0442 (7)
H6	0.8062	0.5292	0.7508	0.053*
C7	0.92111 (17)	0.7476 (5)	0.67579 (12)	0.0385 (6)
H7	0.9697	0.7714	0.6593	0.046*
C8	0.8410 (2)	1.0791 (5)	0.62877 (14)	0.0528 (8)
H8A	0.8947	1.1321	0.6205	0.063*
H8B	0.8180	1.1938	0.6523	0.063*
C9	0.78353 (18)	1.0482 (5)	0.56910 (12)	0.0445 (7)
H9A	0.7282	1.0087	0.5770	0.053*
H9B	0.8038	0.9262	0.5466	0.053*
C10	0.77822 (18)	1.2613 (5)	0.53064 (12)	0.0456 (7)
H10A	0.7577	1.3822	0.5534	0.055*
H10B	0.8340	1.3014	0.5237	0.055*
N1	0.90964 (12)	0.5813 (4)	0.71275 (9)	0.0322 (5)
N2	0.79524 (15)	0.7956 (5)	0.69706 (11)	0.0501 (7)
N3	0.85408 (14)	0.8749 (4)	0.66562 (10)	0.0381 (5)
O1	0.95006 (13)	0.1461 (3)	0.79962 (9)	0.0516 (5)
O2	0.92629 (16)	0.4359 (4)	0.85545 (9)	0.0654 (7)
Zn1	1.0000	0.36383 (7)	0.7500	0.03159 (16)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0392 (15)	0.0449 (18)	0.0298 (15)	−0.0003 (13)	−0.0049 (12)	0.0108 (13)
C2	0.0415 (16)	0.0464 (18)	0.0380 (16)	−0.0070 (13)	0.0051 (12)	0.0064 (13)
C3	0.0420 (15)	0.0383 (16)	0.0285 (13)	−0.0033 (13)	0.0099 (11)	0.0071 (12)
C4	0.0629 (18)	0.0311 (16)	0.0310 (14)	−0.0028 (14)	0.0086 (13)	−0.0012 (11)
C5	0.0586 (19)	0.0327 (16)	0.0387 (16)	0.0053 (14)	0.0088 (14)	0.0044 (12)
C6	0.0366 (15)	0.053 (2)	0.0430 (16)	0.0031 (14)	0.0064 (12)	0.0148 (14)
C7	0.0369 (15)	0.0394 (17)	0.0391 (15)	0.0004 (13)	0.0061 (12)	0.0053 (13)
C8	0.063 (2)	0.0353 (18)	0.0536 (19)	0.0011 (15)	−0.0104 (15)	0.0097 (14)
C9	0.0480 (17)	0.0402 (17)	0.0428 (16)	0.0029 (14)	0.0002 (13)	0.0092 (13)
C10	0.0478 (17)	0.0448 (18)	0.0437 (17)	0.0065 (15)	0.0061 (13)	0.0141 (14)
N1	0.0306 (11)	0.0332 (13)	0.0314 (11)	−0.0002 (9)	0.0005 (9)	0.0039 (9)
N2	0.0405 (14)	0.0571 (18)	0.0522 (15)	0.0111 (12)	0.0062 (12)	0.0089 (13)
N3	0.0405 (13)	0.0338 (13)	0.0368 (12)	0.0013 (11)	−0.0038 (10)	0.0053 (10)
O1	0.0642 (14)	0.0406 (13)	0.0549 (13)	0.0055 (10)	0.0251 (11)	0.0085 (10)
O2	0.1079 (19)	0.0449 (14)	0.0427 (12)	−0.0208 (13)	0.0099 (12)	0.0002 (10)
Zn1	0.0347 (3)	0.0271 (3)	0.0311 (2)	0.000	−0.00019 (17)	0.000

Geometric parameters (Å, º)

C1—O2	1.237 (4)	C7—H7	0.93
C1—O1	1.258 (3)	C8—N3	1.464 (3)
C1—C2	1.523 (4)	C8—C9	1.501 (4)
C2—C3	1.520 (3)	C8—H8A	0.97
C2—H2A	0.97	C8—H8B	0.97
C2—H2B	0.97	C9—C10	1.526 (4)
C3—C4	1.380 (4)	C9—H9A	0.97
C3—C5^i	1.391 (4)	C9—H9B	0.97
C4—C5	1.382 (4)	C10—C10^ii	1.516 (5)
C4—H4	0.93	C10—H10A	0.97
C5—C3^i	1.391 (4)	C10—H10B	0.97
C5—H5	0.93	N1—Zn1	2.031 (2)
C6—N2	1.311 (4)	N2—N3	1.353 (3)
C6—N1	1.353 (3)	O1—Zn1	1.960 (2)
C6—H6	0.93	Zn1—O1^iii	1.960 (2)
C7—N3	1.315 (3)	Zn1—N1^iii	2.031 (2)
C7—N1	1.319 (3)
O2—C1—O1	123.5 (3)	C9—C8—H8B	108.8
O2—C1—C2	120.1 (3)	H8A—C8—H8B	107.7
O1—C1—C2	116.4 (3)	C8—C9—C10	111.1 (3)
C3—C2—C1	111.3 (2)	C8—C9—H9A	109.4
C3—C2—H2A	109.4	C10—C9—H9A	109.4
C1—C2—H2A	109.4	C8—C9—H9B	109.4
C3—C2—H2B	109.4	C10—C9—H9B	109.4
C1—C2—H2B	109.4	H9A—C9—H9B	108.0
H2A—C2—H2B	108.0	C10^ii—C10—C9	113.4 (3)
C4—C3—C5^i	117.8 (2)	C10^ii—C10—H10A	108.9
C4—C3—C2	121.2 (3)	C9—C10—H10A	108.9
C5^i—C3—C2	121.0 (3)	C10^ii—C10—H10B	108.9
C3—C4—C5	121.3 (3)	C9—C10—H10B	108.9
C3—C4—H4	119.4	H10A—C10—H10B	107.7
C5—C4—H4	119.4	C7—N1—C6	103.0 (2)
C4—C5—C3^i	121.0 (3)	C7—N1—Zn1	124.73 (18)
C4—C5—H5	119.5	C6—N1—Zn1	131.49 (18)
C3^i—C5—H5	119.5	C6—N2—N3	102.8 (2)
N2—C6—N1	114.0 (3)	C7—N3—N2	109.9 (2)
N2—C6—H6	123.0	C7—N3—C8	128.2 (3)
N1—C6—H6	123.0	N2—N3—C8	121.8 (2)
N3—C7—N1	110.3 (2)	C1—O1—Zn1	113.31 (19)
N3—C7—H7	124.8	O1—Zn1—O1^iii	96.84 (12)
N1—C7—H7	124.8	O1—Zn1—N1^iii	122.15 (9)
N3—C8—C9	113.7 (2)	O1^iii—Zn1—N1^iii	108.47 (9)
N3—C8—H8A	108.8	O1—Zn1—N1	108.47 (9)
C9—C8—H8A	108.8	O1^iii—Zn1—N1	122.15 (9)
N3—C8—H8B	108.8	N1^iii—Zn1—N1	100.48 (12)
O2—C1—C2—C3	−75.1 (3)	C6—N2—N3—C7	−0.2 (3)
O1—C1—C2—C3	104.2 (3)	C6—N2—N3—C8	−177.9 (2)
C1—C2—C3—C4	−111.6 (3)	C9—C8—N3—C7	106.9 (3)
C1—C2—C3—C5^i	66.8 (3)	C9—C8—N3—N2	−75.8 (4)
C5^i—C3—C4—C5	−0.1 (5)	O2—C1—O1—Zn1	0.6 (4)
C2—C3—C4—C5	178.3 (2)	C2—C1—O1—Zn1	−178.69 (16)
C3—C4—C5—C3^i	0.1 (5)	C1—O1—Zn1—O1^iii	169.5 (2)
N3—C8—C9—C10	−175.3 (3)	C1—O1—Zn1—N1^iii	52.6 (2)
C8—C9—C10—C10^ii	179.2 (3)	C1—O1—Zn1—N1	−63.3 (2)
N3—C7—N1—C6	−1.0 (3)	C7—N1—Zn1—O1	−178.7 (2)
N3—C7—N1—Zn1	−172.05 (17)	C6—N1—Zn1—O1	13.0 (3)
N2—C6—N1—C7	1.0 (3)	C7—N1—Zn1—O1^iii	−67.7 (2)
N2—C6—N1—Zn1	171.10 (19)	C6—N1—Zn1—O1^iii	124.0 (2)
N1—C6—N2—N3	−0.5 (3)	C7—N1—Zn1—N1^iii	52.1 (2)
N1—C7—N3—N2	0.8 (3)	C6—N1—Zn1—N1^iii	−116.2 (3)
N1—C7—N3—C8	178.3 (2)

Symmetry codes: (i) −x+2, −y, −z+2; (ii) −x+3/2, −y+5/2, −z+1; (iii) −x+2, y, −z+3/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···O2^iv	0.93	2.37	3.299 (4)	174
C6—H6···N2^v	0.93	2.57	3.478 (4)	166

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