A chiral inter­digitated supra­molecular network assembled from single-stranded helical tubes

The amino-functionalized helical chiral one-dimensional coordination polymer catena-poly[[bis­(pyridine-κN)zinc(II)]-μ-2-amino­benzene-1,4-dicarboxyl­ato-κ⁴O¹,O^1′:O⁴,O^4′], [Zn(C₈H₅NO₄)(C₅H₅N)₂]_n, has an extended structure that is assembled from 2-amino­benzene-1,4-dicarboxyl­ate anions and Zn²⁺ cations and which presents a left-handed 4₃ helix with a pitch of 25.6975 (9) Å. All the pyridine rings and all the amino groups point away from the helix to generate a hollow tube with a cross-section of approximately 8 × 8 Å running parallel to the crystallographic c direction. Each single-stranded helix is inter­digitated with four neighbouring helices via N—H...O hydrogen bonds, which gives rise to a dense homochiral three-dimensional supra­molecular network.

S1. Comment

Considerable effort has been devoted to the synthesis and characterization of metal–organic coordination polymers because of their fascinating topologies and potential applications. One-dimensional coordination polymers, being the simplest topological type of coordination network, are commonly encountered in a number of forms such as helices, ladders, ribbons and zigzag chains (Leong & Vittal, 2011). Infinite helical coordination polymers have attracted growing interest because of their similarities to biological systems and because of their potential utility in enantioselective catalysis (Han & Hong, 2005; Zheng & Lu, 2010). Argueably the most important feature of a helix is its chirality, and to investigate this a number of helical chiral coordination polymers have been assembled using flexible chiral or achiral organic linkers (Anokhina & Jacobson, 2004; Cui et al., 2003; Reger et al., 2011; Yuan et al., 2009). When achiral organic ligands are used, many successful examples of spontaneous chiral induction have also been reported in the literature (Balamurugan & Mukherjee, 2005; Ezuhara et al., 1999; Han et al., 2007; He et al., 2007; Wang et al., 2005).

For the lower-dimensional helical chiral coordination polymers, it is easy and desirable to incorporate functional properties at the metal centres or in the backbone of the organic linkers. Furthermore, it is possible to develop strategies for engineering higher-dimensional materials through supramolecular entanglement (Cui et al., 2003; Han & Zhou, 2008; Leong & Vittal, 2011; Wang et al., 2004). These entangled porous frameworks usually display tuneable flexibility, which is useful for various applications and often associated with weak interactions, including hydrogen bonds, π-electron stacking and van der Waals interactions. In this study, we have synthesized a one-dimensional amino-functionalized helical chiral coordination polymer from achiral ligands, [Zn(NH₂-BDC)(py)₂]_n (NH₂-BDC is 2-aminobenzene-1,4-dicarboxylate and py is pyridine), (I), which forms a three-dimensional interdigitated supramolecular network via N—H···O hydrogen bonds.

The colourless crystals of (I) were synthesized hydrothermally by reacting Zn(NO₃)₂.6H₂O, 2-aminobenzene-1,4-dicarboxylic acid and pyridine at 423 K for 3 d. Compound (I) crystallizes in the chiral space group P4₃ with one Zn²⁺ cation, one NH₂-BDC anion and two pyridine molecules per asymmetric unit, as shown in Fig. 1. The Zn²⁺ centre is coordinated by four O atoms from the carboxylate groups of two different NH₂-BDC ligands and two mutually cis N atoms from the pyridine groups, giving a distorted octahedral geometry. The bond angles around the Zn²⁺ centre are given in Table 1. The Zn—O bond lengths range from 2.011 (3) to 2.480 (3) Å, a large spread, which is due to the highly asymmetric coordination mode adopted by the carboxylate groups. Introducing the amino group into the backbone of the ligand results in an intramolecular hydrogen bond, N3—H3B···O3, with a donor-to-acceptor distance of 2.715 (8) Å. It should be pointed out that amino-functionalized porous coordination frameworks have recently gained much attention because of an enhanced capacity for CO₂ adsorption (Couck et al., 2009; Vaidhyanathan et al., 2009).

The coordination behaviour of the bridging NH₂-BDC ligand of (I) results in an infinite helical architecture running along the crystallographic c axis (Fig.2). The left-handed helix is generated around the crystallographic 4₃ axis with a pitch of 25.6975 (9) Å. Each `turn' of the helix consists of four Zn/NH₂-BDC units. All the pyridine rings and the amino groups point away from the helical axis to generate a hollow tube with an opening of approximately 8 × 8 Å. Each left-handed helix further interweaves with four similar helices and links to them via strong intermolecular N—H···O hydrogen bonds (see Table 2). This combines to give a dense three-dimensional interdigitated supramolecular network (Fig. 3). All helices have, of crystallographic necessity, the same left-handed chirality and run along the c direction. This leads to an enantiopure network, despite being formed solely from achiral molecular units. As other crystals from the sample were not analysed, we must assume that the bulk sample is a conglomerate containing both possible handed forms.

In conclusion, (I) is an interesting example of an amino-functionalized helical one-dimensional coordination polymer assembled from achiral ligands.

Related literature

For related literature, see: Anokhina & Jacobson (2004); Balamurugan & Mukherjee (2005); Couck et al. (2009); Cui et al. (2003); Ezuhara et al. (1999); Han & Hong (2005); Han & Zhou (2008); Han et al. (2007); He et al. (2007); Leong & Vittal (2011); Reger et al. (2011); Vaidhyanathan et al. (2009); Wang et al. (2004, 2005); Yuan et al. (2009); Zheng & Lu (2010).

S2. Experimental

A mixture of Zn(NO₃)₂.6H₂O (92.6 mg, 0.5 mmol), 2-aminobenzene-1,4-dicarboxylic acid (149.6 mg, 0.5 mmol) and pyridine (1.0 g) in H₂O (5 ml) was sealed in a 25 ml Teflon-lined stainless steel reactor and heated at 423 K for 3 d. A crop of colourless single crystals of the title compound was obtained after cooling the solution to room temperature. Block-shaped crystals of (I) were collected and washed with distilled water. The yield was approximately 40% based on Zn²⁺.

S3. Refinement

All H atoms were positioned geometrically and allowed to ride on their respective parent atoms at distances of C—H = 0.93 Å and N—H = 0.86 Å, and with U_iso(H) = 1.2 U_eq(C,N). Displacement ellipsoids indicate some considerable vibrational movement or disorder in the NH₂-BDC ligands, but we were unable to model this.

Computing details

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2004); 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: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The asymmetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 1 + x, 1 - y, z - 1/4; (ii) 1 - x, y - 1, z + 1/4.]
	Fig. 2. Views of (a) the one-dimensional helical tube and (b) and left-handed helix of (I). All H atoms have been omitted for clarity.
	Fig. 3. (a) A view of the three-dimensional supramolecular network assembled from helices by N—H···O hydrogen bonds. All pyridine molecules and some of the H atoms have been omitted for clarity. (b) Schematic representation of the chiral interdigitated network of (I).

catena-poly[[bis(pyridine-κN)zinc(II)]-µ-2-aminobenzene-1,4- dicarboxylato-κ⁴O¹,O^1':O⁴,O^4']

Crystal data

[Zn(C8H5NO4)(C5H5N)2]	Dx = 1.467 Mg m^−3
Mr = 402.70	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43	Cell parameters from 3397 reflections
Hall symbol: P 4cw	θ = 3.8–25.5°
a = 8.4243 (1) Å	µ = 1.37 mm^−1
c = 25.6975 (9) Å	T = 298 K
V = 1823.72 (7) Å^3	Block, colourless
Z = 4	0.26 × 0.24 × 0.20 mm
F(000) = 824

Data collection

Rigaku R-AXIS RAPID diffractometer	3172 independent reflections
Radiation source: fine-focus sealed tube	2082 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.057
Detector resolution: 0 pixels mm^-1	θmax = 25.0°, θmin = 3.8°
ω scans	h = −8→10
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −9→10
Tmin = 0.716, Tmax = 0.771	l = −30→30
11175 measured reflections

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)] = 0.043	H-atom parameters constrained
wR(F^2) = 0.071	w = 1/[σ^2(Fo^2) + (0.0204P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max = 0.005
3172 reflections	Δρmax = 0.47 e Å^−3
235 parameters	Δρmin = −0.29 e Å^−3
1 restraint	Absolute structure: Flack (1983), 1546 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.030 (17)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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	0.13367 (7)	0.28865 (6)	0.22997 (3)	0.05215 (18)
O1	0.0108 (5)	0.3604 (4)	0.29281 (14)	0.0684 (10)
O2	−0.1383 (4)	0.4001 (4)	0.22471 (16)	0.0665 (10)
O3	−0.6869 (7)	0.7693 (6)	0.39686 (18)	0.1087 (16)
O4	−0.4988 (6)	0.7690 (5)	0.45486 (19)	0.0921 (16)
N1	0.0322 (5)	0.0729 (5)	0.21115 (18)	0.0555 (13)
N2	0.3322 (5)	0.1989 (6)	0.26715 (17)	0.0597 (12)
N3	−0.6359 (8)	0.6390 (7)	0.3017 (3)	0.139 (2)
H3B	−0.7069	0.6858	0.3202	0.166*
H3C	−0.6574	0.6106	0.2703	0.166*
C1	−0.1159 (7)	0.4141 (6)	0.2713 (2)	0.0518 (14)
C2	−0.2307 (7)	0.4956 (6)	0.3073 (2)	0.0497 (15)
C3	−0.1873 (7)	0.5372 (6)	0.3570 (2)	0.0640 (16)
H3A	−0.0863	0.5133	0.3693	0.077*
C4	−0.2944 (9)	0.6144 (7)	0.3883 (2)	0.0756 (19)
H4A	−0.2636	0.6425	0.4218	0.091*
C5	−0.4462 (8)	0.6519 (7)	0.3720 (3)	0.0607 (16)
C6	−0.4836 (6)	0.6087 (6)	0.3228 (3)	0.0583 (15)
C7	−0.3820 (6)	0.5343 (5)	0.2872 (3)	0.0622 (16)
H7A	−0.4118	0.5122	0.2531	0.075*
C8	−0.5454 (10)	0.7367 (8)	0.4115 (3)	0.078 (2)
C9	0.4413 (8)	0.1131 (8)	0.2414 (3)	0.092 (2)
H9A	0.4324	0.1058	0.2054	0.111*
C10	0.5621 (9)	0.0377 (9)	0.2644 (4)	0.113 (3)
H10A	0.6341	−0.0211	0.2449	0.136*
C11	0.5773 (9)	0.0489 (9)	0.3167 (4)	0.100 (2)
H11A	0.6596	−0.0033	0.3337	0.121*
C12	0.4739 (9)	0.1348 (9)	0.3435 (3)	0.087 (2)
H12A	0.4838	0.1441	0.3794	0.104*
C13	0.3527 (7)	0.2094 (8)	0.3182 (2)	0.0699 (15)
H13A	0.2817	0.2701	0.3374	0.084*
C14	−0.0490 (7)	0.0512 (8)	0.1669 (3)	0.0773 (18)
H14A	−0.0489	0.1324	0.1424	0.093*
C15	−0.1310 (8)	−0.0826 (10)	0.1560 (3)	0.096 (2)
H15A	−0.1881	−0.0925	0.1252	0.115*
C16	−0.1274 (10)	−0.2025 (9)	0.1915 (4)	0.101 (3)
H16A	−0.1851	−0.2950	0.1857	0.121*
C17	−0.0399 (8)	−0.1867 (7)	0.2351 (4)	0.101 (2)
H17A	−0.0323	−0.2709	0.2583	0.122*
C18	0.0372 (7)	−0.0488 (8)	0.2452 (3)	0.082 (2)
H18A	0.0941	−0.0380	0.2760	0.098*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0575 (4)	0.0499 (4)	0.0491 (3)	−0.0020 (4)	0.0135 (4)	0.0004 (4)
O1	0.067 (3)	0.076 (3)	0.062 (3)	0.011 (2)	0.017 (2)	−0.002 (2)
O2	0.081 (3)	0.070 (2)	0.049 (2)	0.0060 (19)	0.018 (2)	−0.002 (2)
O3	0.119 (4)	0.115 (4)	0.092 (4)	0.042 (3)	0.037 (3)	0.007 (3)
O4	0.111 (4)	0.084 (4)	0.082 (4)	0.010 (3)	0.028 (3)	−0.027 (3)
N1	0.061 (3)	0.049 (3)	0.056 (4)	−0.002 (2)	0.015 (2)	0.004 (3)
N2	0.053 (3)	0.073 (3)	0.052 (3)	−0.008 (3)	0.012 (2)	−0.008 (3)
N3	0.139 (6)	0.137 (6)	0.139 (6)	0.010 (5)	0.026 (5)	−0.031 (5)
C1	0.044 (4)	0.049 (3)	0.062 (4)	0.008 (3)	0.017 (3)	0.006 (3)
C2	0.058 (4)	0.035 (3)	0.056 (4)	0.000 (3)	0.018 (3)	−0.005 (3)
C3	0.058 (4)	0.076 (4)	0.058 (4)	0.015 (3)	0.006 (3)	−0.017 (3)
C4	0.101 (6)	0.057 (4)	0.070 (4)	0.005 (4)	0.026 (5)	−0.006 (3)
C5	0.065 (4)	0.054 (4)	0.063 (4)	0.009 (3)	0.019 (4)	−0.001 (3)
C6	0.035 (3)	0.053 (4)	0.087 (5)	0.003 (3)	0.002 (3)	0.007 (3)
C7	0.044 (4)	0.038 (3)	0.105 (5)	0.006 (3)	0.037 (3)	0.004 (3)
C8	0.080 (6)	0.055 (4)	0.099 (6)	0.018 (4)	0.040 (5)	0.023 (5)
C9	0.081 (5)	0.118 (6)	0.077 (6)	0.036 (4)	0.010 (4)	−0.027 (4)
C10	0.084 (6)	0.138 (7)	0.117 (8)	0.056 (5)	−0.007 (5)	−0.004 (6)
C11	0.071 (6)	0.101 (6)	0.129 (8)	−0.001 (5)	−0.022 (6)	0.026 (6)
C12	0.071 (5)	0.127 (6)	0.062 (5)	−0.008 (5)	−0.013 (4)	0.013 (4)
C13	0.061 (4)	0.087 (5)	0.062 (4)	−0.004 (4)	0.003 (4)	−0.008 (4)
C14	0.094 (5)	0.073 (5)	0.065 (4)	−0.008 (4)	−0.011 (4)	0.009 (4)
C15	0.112 (6)	0.096 (6)	0.078 (5)	−0.045 (5)	0.005 (4)	−0.042 (5)
C16	0.130 (8)	0.054 (5)	0.118 (8)	−0.031 (5)	0.038 (6)	−0.027 (5)
C17	0.118 (6)	0.060 (5)	0.126 (8)	−0.019 (4)	0.021 (6)	0.031 (5)
C18	0.087 (5)	0.064 (4)	0.094 (6)	−0.017 (4)	−0.002 (4)	0.032 (4)

Geometric parameters (Å, º)

Zn1—O1	2.011 (3)	C4—C5	1.382 (8)
Zn1—N1	2.066 (4)	C4—H4A	0.9300
Zn1—N2	2.069 (5)	C5—C6	1.353 (7)
Zn1—O4^i	2.072 (5)	C5—C8	1.496 (9)
Zn1—O3^i	2.296 (5)	C6—C7	1.401 (7)
Zn1—O2	2.480 (3)	C7—H7A	0.9300
Zn1—C8^i	2.498 (7)	C8—Zn1^ii	2.498 (7)
Zn1—C1	2.582 (5)	C9—C10	1.337 (8)
O1—C1	1.284 (6)	C9—H9A	0.9300
O2—C1	1.219 (6)	C10—C11	1.352 (8)
O3—C8	1.279 (8)	C10—H10A	0.9300
O3—Zn1^ii	2.296 (5)	C11—C12	1.326 (10)
O4—C8	1.212 (8)	C11—H11A	0.9300
O4—Zn1^ii	2.072 (4)	C12—C13	1.364 (8)
N1—C14	1.340 (7)	C12—H12A	0.9300
N1—C18	1.348 (6)	C13—H13A	0.9300
N2—C13	1.325 (6)	C14—C15	1.351 (8)
N2—C9	1.343 (6)	C14—H14A	0.9300
N3—C6	1.416 (8)	C15—C16	1.362 (9)
N3—H3B	0.8600	C15—H15A	0.9300
N3—H3C	0.8600	C16—C17	1.347 (10)
C1—C2	1.503 (7)	C16—H16A	0.9300
C2—C3	1.374 (7)	C17—C18	1.356 (8)
C2—C7	1.413 (7)	C17—H17A	0.9300
C3—C4	1.373 (7)	C18—H18A	0.9300
C3—H3A	0.9300
O1—Zn1—N1	103.86 (15)	C2—C3—H3A	120.3
O1—Zn1—N2	98.92 (17)	C4—C3—H3A	120.3
N1—Zn1—N2	96.93 (19)	C3—C4—C5	122.6 (6)
O1—Zn1—O4^i	101.20 (18)	C3—C4—H4A	118.7
N1—Zn1—O4^i	148.31 (19)	C5—C4—H4A	118.7
N2—Zn1—O4^i	98.03 (19)	C6—C5—C4	115.9 (6)
O1—Zn1—O3^i	154.57 (18)	C6—C5—C8	129.2 (7)
N1—Zn1—O3^i	90.48 (18)	C4—C5—C8	114.9 (7)
N2—Zn1—O3^i	100.06 (17)	C5—C6—C7	126.0 (5)
O4^i—Zn1—O3^i	59.46 (17)	C5—C6—N3	121.4 (6)
O1—Zn1—O2	56.93 (14)	C7—C6—N3	112.5 (6)
N1—Zn1—O2	86.47 (15)	C6—C7—C2	114.6 (6)
N2—Zn1—O2	155.54 (15)	C6—C7—H7A	122.7
O4^i—Zn1—O2	91.23 (15)	C2—C7—H7A	122.7
O3^i—Zn1—O2	104.13 (16)	O4—C8—O3	121.6 (7)
O1—Zn1—C8^i	128.5 (3)	O4—C8—C5	123.3 (8)
N1—Zn1—C8^i	120.5 (3)	O3—C8—C5	115.1 (8)
N2—Zn1—C8^i	100.16 (18)	O4—C8—Zn1^ii	55.7 (4)
O4^i—Zn1—C8^i	28.9 (2)	O3—C8—Zn1^ii	65.9 (4)
O3^i—Zn1—C8^i	30.6 (2)	C5—C8—Zn1^ii	177.2 (5)
O2—Zn1—C8^i	98.84 (18)	C10—C9—N2	123.9 (7)
O1—Zn1—C1	29.22 (15)	C10—C9—H9A	118.0
N1—Zn1—C1	96.88 (17)	N2—C9—H9A	118.0
N2—Zn1—C1	128.13 (19)	C9—C10—C11	118.6 (8)
O4^i—Zn1—C1	95.56 (18)	C9—C10—H10A	120.7
O3^i—Zn1—C1	129.50 (19)	C11—C10—H10A	120.7
O2—Zn1—C1	27.77 (14)	C12—C11—C10	119.5 (8)
C8^i—Zn1—C1	114.6 (2)	C12—C11—H11A	120.3
C1—O1—Zn1	100.9 (3)	C10—C11—H11A	120.3
C1—O2—Zn1	80.8 (3)	C11—C12—C13	119.7 (7)
C8—O3—Zn1^ii	83.5 (4)	C11—C12—H12A	120.2
C8—O4—Zn1^ii	95.5 (5)	C13—C12—H12A	120.2
C14—N1—C18	117.6 (5)	N2—C13—C12	122.6 (6)
C14—N1—Zn1	122.0 (4)	N2—C13—H13A	118.7
C18—N1—Zn1	120.3 (4)	C12—C13—H13A	118.7
C13—N2—C9	115.7 (5)	N1—C14—C15	123.4 (6)
C13—N2—Zn1	122.5 (4)	N1—C14—H14A	118.3
C9—N2—Zn1	121.5 (4)	C15—C14—H14A	118.3
C6—N3—H3B	120.0	C14—C15—C16	117.9 (7)
C6—N3—H3C	120.0	C14—C15—H15A	121.0
H3B—N3—H3C	120.0	C16—C15—H15A	121.0
O2—C1—O1	121.1 (5)	C17—C16—C15	119.7 (7)
O2—C1—C2	123.2 (5)	C17—C16—H16A	120.1
O1—C1—C2	115.6 (6)	C15—C16—H16A	120.1
O2—C1—Zn1	71.4 (3)	C16—C17—C18	120.4 (7)
O1—C1—Zn1	49.9 (2)	C16—C17—H17A	119.8
C2—C1—Zn1	164.6 (5)	C18—C17—H17A	119.8
C3—C2—C7	121.4 (5)	N1—C18—C17	120.8 (6)
C3—C2—C1	121.1 (5)	N1—C18—H18A	119.6
C7—C2—C1	117.5 (5)	C17—C18—H18A	119.6
C2—C3—C4	119.4 (6)

Symmetry codes: (i) −y+1, x+1, z−1/4; (ii) y−1, −x+1, z+1/4.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3B···O3	0.86	2.10	2.715 (8)	128
N3—H3C···O4^iii	0.86	2.14	2.966 (9)	162

Symmetry code: (iii) −y, x+1, z−1/4.