A novel two-dimensional zinc(II) coordination polymer with 6-mer­captonicotinic acid

The novel title Zn^II coordination polymer, poly[bis­([mu]-6-thioxo-1,6-dihydropyridine-3-carboxylato-[kappa]²S:O)zinc(II)], [Zn(C₆H₄NO₂S)₂]_n, consists of two crystallographically independent zinc centers and two 6-mercaptonicotinate (Hmna^-) ligands. Each Zn^II atom is four-coordinated and lies at the center of a distorted tetra­hedral ZnS₂O₂ coordination polyhedron, bridged by four Hmna^- ligands to form a two-dimensional (4,4)-network. Each Hmna^- ion acts as a bridging bidentate ligand, coordinating to two Zn^II atoms through the S atom and a carboxyl O atom. The metal centers reside on twofold rotation axes. The coordination mode of the S atoms and N-H...O hydrogen-bonding inter­actions between the protonated N atoms and the uncoordinated carboxyl O atoms give the extended structure a wavelike form.

S1. Comment

In recent years, research on coordination polymers has expanded rapidly because of their fascinating structural diversity and potential applications as functional materials (Batten & Robson, 1998; Moulton & Zaworotko, 2001). Multifunctional carboxylates and related species provide an effective means of designing novel hybrid materials with porous structures and other interesting properties (Kitagawa et al., 2004; Yaghi et al., 2003). In contrast with the large amount of work on ligands containing O or N donors, there have been fewer reports of studies based on organothiolate ligands. Three kinds of organothiolate ligands, viz. thiolatopyridine (Han et al., 2004; Su et al., 2000), thiolatocarboxylate (Cave et al., 2002) and thiolatopyridinecarboxylate (Humphrey et al., 2005, 2006) have been explored to construct structures with luminescent or magnetic properties. 6-Mercaptonicotinic acid (H₂mna), which exists in solution as an equilibrium mixture of thiol and thione tautomeric forms, is an interesting ligand in the thiolatopyridinecarboxylate system because of its potential coordination possibilities, which include (a) an S,N-donor chelate and carboxyl uncoordinated mode (Nomiya et al., 2003), (b) an S,N-donor chelate and carboxyl multidentate mode (Humphrey et al., 2005, 2006), (c) an S,N-donor chelate and O,O-chelation bridging mode (Humphrey et al., 2005, 2006), (d) a single S-donor and carboxyl monodentate mode, and (e) an S,N-donor chelate and carboxyl monodentate mode. In addition, it can act not only as a hydrogen-bond donor but also as a hydrogen-bond acceptor, owing to the existence of deprotonated and/or protonated carboxyl groups and pyridine N atoms, as well as the thiol or thione group. These considerations prompted our interest in the structure patterns of the H₂mna ligand. In this paper, we report the preparation and crystal structure of a novel two-dimensional coordination polymer, (I), formulated [Zn(Hmna)₂]_n.

The asymmetric unit of (I) consists of two zinc centers and two Hmna^- ligands (Fig. 1). Each Zn^II atom sits on a twofold rotation axis and is coordinated by two O atoms and two S atoms from four different Hmna^- ligands in a typical distorted tetrahedral coordination geometry (Table 1). The bond lengths and angles involving Zn, O and S are similar to those in analogous zinc coordination polymers (Humphrey et al., 2004). The two Hmna^- ligands in the asymmetric unit adopt the same coordination mode, i.e. the thione coordinates to the Zn atoms and the carboxyl group links the Zn atoms in a monodentate coordination fashion [mode (d) above]. To the best of our knowledge, (I) is the first example with this coordination mode (d) of the H₂mna ligand. In the molecular structure, the C5—S1 and C11—S2 bond lengths [1.728 (3) and 1.723 (3) Å] are indicative of double bonds, similar to those in a number of structures reported previously (Chung et al., 2003; Lobana et al., 2005). The C5—S1—Zn1 and C11—S2—Zn2ⁱ [symmetry code: (i) -x + 1, -y + 1, -z + 1] bond angles are 100.44 (9) and 111.71 (9)°, respectively.

The molecules of (I) form an extended two-dimensional network involving coordination frameworks of (4,4)-topology (Fig. 2). In the grid, the adjacent Zn···Zn distances (linked by Hmna^- ligands) are 10.015 and 9.618 Å, so each 4 × 4 unit is an approximate rhombus. Considering the Zn^II atoms as three-connected nodes, the corrugated metal-organic framework can be represented as a two-dimensional distorted sheet of (4,4)-topology in the ac plane. These layers are then stacked on top of each other to give rise to the final structure (Fig. 3).

There are some significant hydrogen-bonding interactions between the protonated N atoms of the Hmna^- ligands (owing to the thiol–thione tautomerism) and the uncoordinated carboxyl O atoms (Table 2). The coordination mode of the S atoms and the hydrogen-bonding interactions lead the complex to form a wavelike extended structure along the (010) plane (Fig. 3).

Related literature

For related literature, see: Batten & Robson (1998); Cave et al. (2002); Han et al. (2004); Humphrey et al. (2004); Kitagawa et al. (2004); Moulton & Zaworotko (2001); Nomiya et al. (2003); Su et al. (2000); Yaghi et al. (2003).

S2. Experimental

A mixture of Zn(CH₃COO)₂·2H₂O (0.0658 g), H₂mna (0.0466 g), NaOH (0.012 g) and water (10 ml) was stirred for 20 min in air. The mixture was then transferred to a 23 ml Teflon reactor and kept at 438 K for 3 d under autogenous pressure, then cooled to room temperature at a rate of 5 K h^-1. Colorless block-like crystals of (I) were obtained; they were washed with distilled water and dried at room temperature (yield ca 50% based on Zn). Elemental analysis found: C 38.64, H 2.10, N 7.62%; calculated: C 38.57, H 2.16, N 7.50%.

S3. Refinement

All H atoms were generated geometrically and included as riding atoms, with C—H = 0.93 Å, N—H = 0.86 Å and U_iso(H)= 1.2U_eq(C,N).

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus (Sheldrick, 1990); software used to prepare material for publication: program (reference)?.

Figures

	Fig. 1. A view of the local coordination of Zn^II, with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry codes: (i) -x + 1, -y + 1, -z + 1; (ii) -x + 1, y, -z + 3/2; (iii) -x, y, -z + 1/2; (iv) x - 1, -y + 1, z - 1/2.]
	Fig. 2. The two-dimensional single-layer (4,4)-network in (I). The N—H···O hydrogen bonds are shown as dashed lines. H atoms bonded to C atoms have been omitted for clarity.
	Fig. 3. The view of the sine wave sheets in (I), along the (010) plane.

poly[bis(µ-6-mercaptonicotinato-κ²S:O)zinc(II)]

Crystal data

[Zn(C6H4NO2S)2]	F(000) = 752
Mr = 373.69	Dx = 1.828 Mg m^−3
Monoclinic, P2/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.4079 (8) Å	Cell parameters from 7030 reflections
b = 6.5765 (4) Å	θ = 1.6–28.3°
c = 16.0390 (9) Å	µ = 2.13 mm^−1
β = 106.283 (1)°	T = 293 K
V = 1357.54 (14) Å^3	Block, colorless
Z = 4	0.23 × 0.19 × 0.14 mm

Data collection

Bruker SMART APEXII CCD diffractometer	3222 independent reflections
Radiation source: fine-focus sealed tube	2531 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
ϕ and ω scans	θmax = 28.4°, θmin = 1.6°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −15→17
Tmin = 0.640, Tmax = 0.755	k = −7→8
8024 measured reflections	l = −21→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)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.094	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0499P)^2] where P = (Fo^2 + 2Fc^2)/3
3222 reflections	(Δ/σ)max = 0.001
191 parameters	Δρmax = 0.37 e Å^−3
0 restraints	Δρmin = −0.42 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
Zn1	0.5000	−0.34394 (6)	0.7500	0.02530 (13)
Zn2	0.0000	0.21258 (6)	0.2500	0.02685 (13)
S1	0.43938 (6)	−0.52761 (10)	0.62292 (4)	0.03456 (19)
S2	0.96122 (6)	0.60438 (12)	0.86184 (5)	0.0372 (2)
O1	0.09182 (14)	0.0180 (3)	0.32820 (12)	0.0341 (5)
O2	0.22106 (16)	0.2440 (3)	0.36875 (13)	0.0369 (5)
O3	0.62239 (15)	−0.1658 (3)	0.76481 (13)	0.0344 (5)
O4	0.56008 (15)	0.0335 (3)	0.64862 (13)	0.0381 (5)
N1	0.38953 (17)	−0.1566 (3)	0.55170 (14)	0.0265 (5)
H1	0.4491	−0.1199	0.5847	0.032*
N2	0.79097 (16)	0.4525 (3)	0.74755 (14)	0.0274 (5)
H2	0.7918	0.5632	0.7193	0.033*
C1	0.1796 (2)	0.0782 (4)	0.37571 (16)	0.0274 (6)
C2	0.23661 (19)	−0.0677 (4)	0.44346 (15)	0.0236 (5)
C3	0.1986 (2)	−0.2630 (4)	0.45163 (18)	0.0302 (6)
H3	0.1323	−0.2988	0.4184	0.036*
C4	0.2577 (2)	−0.4014 (4)	0.50771 (17)	0.0313 (6)
H4	0.2314	−0.5305	0.5123	0.038*
C5	0.3580 (2)	−0.3503 (4)	0.55854 (16)	0.0264 (6)
C6	0.3333 (2)	−0.0187 (4)	0.49645 (15)	0.0261 (5)
H6	0.3600	0.1110	0.4940	0.031*
C7	0.6236 (2)	−0.0083 (4)	0.71967 (17)	0.0266 (6)
C8	0.7101 (2)	0.1385 (4)	0.75667 (17)	0.0243 (5)
C9	0.7883 (2)	0.0983 (4)	0.83314 (17)	0.0308 (6)
H9	0.7878	−0.0236	0.8624	0.037*
C10	0.8657 (2)	0.2366 (4)	0.86529 (19)	0.0328 (6)
H10	0.9173	0.2080	0.9162	0.039*
C11	0.8679 (2)	0.4216 (4)	0.82207 (16)	0.0269 (6)
C12	0.7140 (2)	0.3202 (4)	0.71574 (17)	0.0258 (6)
H12	0.6624	0.3518	0.6652	0.031*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0258 (2)	0.0236 (2)	0.0238 (2)	0.000	0.00250 (18)	0.000
Zn2	0.0208 (2)	0.0254 (2)	0.0292 (2)	0.000	−0.00152 (18)	0.000
S1	0.0449 (4)	0.0236 (4)	0.0269 (3)	0.0092 (3)	−0.0036 (3)	−0.0022 (3)
S2	0.0365 (4)	0.0373 (4)	0.0313 (4)	−0.0139 (3)	−0.0014 (3)	0.0040 (3)
O1	0.0256 (10)	0.0308 (10)	0.0363 (10)	0.0035 (8)	−0.0072 (8)	0.0020 (9)
O2	0.0400 (12)	0.0268 (10)	0.0350 (11)	−0.0014 (9)	−0.0042 (9)	0.0072 (9)
O3	0.0322 (11)	0.0321 (11)	0.0358 (11)	−0.0077 (8)	0.0046 (9)	0.0092 (9)
O4	0.0295 (10)	0.0336 (11)	0.0419 (11)	−0.0067 (9)	−0.0054 (9)	0.0101 (9)
N1	0.0210 (11)	0.0274 (12)	0.0258 (11)	−0.0004 (9)	−0.0022 (9)	0.0013 (9)
N2	0.0283 (12)	0.0208 (11)	0.0310 (11)	−0.0008 (9)	0.0050 (10)	0.0037 (9)
C1	0.0288 (14)	0.0272 (14)	0.0232 (12)	0.0076 (11)	0.0025 (11)	−0.0022 (11)
C2	0.0222 (12)	0.0240 (13)	0.0218 (12)	0.0011 (10)	0.0017 (10)	0.0001 (10)
C3	0.0239 (14)	0.0324 (15)	0.0289 (14)	−0.0054 (11)	−0.0016 (11)	−0.0003 (12)
C4	0.0357 (15)	0.0233 (13)	0.0314 (14)	−0.0068 (12)	0.0037 (12)	0.0013 (12)
C5	0.0309 (14)	0.0236 (13)	0.0209 (12)	0.0021 (11)	0.0011 (11)	−0.0010 (10)
C6	0.0293 (13)	0.0227 (13)	0.0232 (12)	0.0000 (11)	0.0024 (11)	0.0030 (11)
C7	0.0219 (13)	0.0261 (14)	0.0322 (14)	−0.0002 (10)	0.0079 (11)	−0.0015 (11)
C8	0.0227 (13)	0.0231 (13)	0.0276 (13)	0.0000 (10)	0.0082 (11)	0.0013 (11)
C9	0.0309 (15)	0.0290 (14)	0.0307 (14)	−0.0004 (11)	0.0058 (12)	0.0080 (12)
C10	0.0262 (14)	0.0359 (16)	0.0306 (14)	−0.0024 (12)	−0.0012 (12)	0.0059 (12)
C11	0.0231 (13)	0.0281 (14)	0.0274 (13)	−0.0014 (11)	0.0036 (11)	0.0011 (11)
C12	0.0221 (13)	0.0260 (14)	0.0267 (13)	0.0005 (10)	0.0023 (11)	0.0014 (11)

Geometric parameters (Å, º)

Zn1—O3	1.9757 (19)	N2—C11	1.357 (3)
Zn1—O3^i	1.9757 (19)	N2—H2	0.8600
Zn1—S1	2.3119 (7)	C1—C2	1.490 (3)
Zn1—S1^i	2.3119 (7)	C2—C6	1.374 (3)
Zn2—O1^ii	1.9648 (18)	C2—C3	1.401 (4)
Zn2—O1	1.9648 (18)	C3—C4	1.366 (4)
Zn2—S2^iii	2.3367 (8)	C3—H3	0.9300
Zn2—S2^iv	2.3367 (8)	C4—C5	1.404 (4)
S1—C5	1.728 (3)	C4—H4	0.9300
S2—C11	1.723 (3)	C6—H6	0.9300
S2—Zn2^iv	2.3367 (8)	C7—C8	1.497 (3)
O1—C1	1.273 (3)	C8—C12	1.372 (3)
O2—C1	1.243 (3)	C8—C9	1.398 (4)
O3—C7	1.266 (3)	C9—C10	1.367 (4)
O4—C7	1.247 (3)	C9—H9	0.9300
N1—C6	1.342 (3)	C10—C11	1.404 (4)
N1—C5	1.356 (3)	C10—H10	0.9300
N1—H1	0.8600	C12—H12	0.9300
N2—C12	1.337 (3)
O3—Zn1—O3^i	107.26 (12)	C4—C3—H3	119.6
O3—Zn1—S1	119.38 (6)	C2—C3—H3	119.6
O3^i—Zn1—S1	97.41 (6)	C3—C4—C5	120.5 (2)
O3—Zn1—S1^i	97.41 (6)	C3—C4—H4	119.8
O3^i—Zn1—S1^i	119.38 (6)	C5—C4—H4	119.8
S1—Zn1—S1^i	117.00 (4)	N1—C5—C4	116.6 (2)
O1^ii—Zn2—O1	98.72 (11)	N1—C5—S1	121.6 (2)
O1^ii—Zn2—S2^iii	126.23 (6)	C4—C5—S1	121.8 (2)
O1—Zn2—S2^iii	94.59 (6)	N1—C6—C2	120.5 (2)
O1^ii—Zn2—S2^iv	94.59 (6)	N1—C6—H6	119.7
O1—Zn2—S2^iv	126.23 (6)	C2—C6—H6	119.7
S2^iii—Zn2—S2^iv	117.98 (4)	O4—C7—O3	126.0 (2)
C5—S1—Zn1	100.44 (9)	O4—C7—C8	118.3 (2)
C11—S2—Zn2^iv	111.71 (9)	O3—C7—C8	115.7 (2)
C1—O1—Zn2	119.22 (17)	C12—C8—C9	117.7 (2)
C7—O3—Zn1	124.05 (17)	C12—C8—C7	120.1 (2)
C6—N1—C5	123.9 (2)	C9—C8—C7	122.2 (2)
C6—N1—H1	118.0	C10—C9—C8	120.6 (2)
C5—N1—H1	118.0	C10—C9—H9	119.7
C12—N2—C11	123.6 (2)	C8—C9—H9	119.7
C12—N2—H2	118.2	C9—C10—C11	120.6 (2)
C11—N2—H2	118.2	C9—C10—H10	119.7
O2—C1—O1	125.5 (2)	C11—C10—H10	119.7
O2—C1—C2	118.7 (2)	N2—C11—C10	116.6 (2)
O1—C1—C2	115.8 (2)	N2—C11—S2	121.0 (2)
C6—C2—C3	117.5 (2)	C10—C11—S2	122.4 (2)
C6—C2—C1	120.1 (2)	N2—C12—C8	120.9 (2)
C3—C2—C1	122.2 (2)	N2—C12—H12	119.5
C4—C3—C2	120.9 (2)	C8—C12—H12	119.5
O3—Zn1—S1—C5	−86.43 (12)	Zn1—S1—C5—C4	−134.3 (2)
O3^i—Zn1—S1—C5	28.19 (12)	C5—N1—C6—C2	1.4 (4)
S1^i—Zn1—S1—C5	156.63 (10)	C3—C2—C6—N1	2.0 (4)
O1^ii—Zn2—O1—C1	161.8 (2)	C1—C2—C6—N1	−173.4 (2)
S2^iii—Zn2—O1—C1	−70.4 (2)	Zn1—O3—C7—O4	−17.5 (4)
S2^iv—Zn2—O1—C1	59.5 (2)	Zn1—O3—C7—C8	162.43 (17)
O3^i—Zn1—O3—C7	−43.26 (19)	O4—C7—C8—C12	4.5 (4)
S1—Zn1—O3—C7	66.0 (2)	O3—C7—C8—C12	−175.4 (2)
S1^i—Zn1—O3—C7	−167.2 (2)	O4—C7—C8—C9	−176.0 (3)
Zn2—O1—C1—O2	−11.3 (4)	O3—C7—C8—C9	4.1 (4)
Zn2—O1—C1—C2	170.07 (16)	C12—C8—C9—C10	0.0 (4)
O2—C1—C2—C6	−0.4 (4)	C7—C8—C9—C10	−179.6 (3)
O1—C1—C2—C6	178.3 (2)	C8—C9—C10—C11	0.0 (4)
O2—C1—C2—C3	−175.5 (3)	C12—N2—C11—C10	1.7 (4)
O1—C1—C2—C3	3.2 (4)	C12—N2—C11—S2	−176.9 (2)
C6—C2—C3—C4	−2.7 (4)	C9—C10—C11—N2	−0.8 (4)
C1—C2—C3—C4	172.6 (2)	C9—C10—C11—S2	177.8 (2)
C2—C3—C4—C5	0.1 (4)	Zn2^iv—S2—C11—N2	−33.3 (2)
C6—N1—C5—C4	−3.9 (4)	Zn2^iv—S2—C11—C10	148.2 (2)
C6—N1—C5—S1	173.3 (2)	C11—N2—C12—C8	−1.8 (4)
C3—C4—C5—N1	3.1 (4)	C9—C8—C12—N2	0.9 (4)
C3—C4—C5—S1	−174.2 (2)	C7—C8—C12—N2	−179.6 (2)
Zn1—S1—C5—N1	48.5 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O4	0.86	1.85	2.686 (3)	163
N2—H2···O2^iv	0.86	1.87	2.706 (3)	164

Symmetry code: (iv) −x+1, −y+1, −z+1.