A helical coordination polymer of zinc(II), 4-hy­droxy­benzohydrazide and sulfate ions

In the structure of the novel zinc complex catena-poly[[diaqua­(4-hy­droxy­benzo­hydrazide)­zinc(II)]-[mu]-sulfato], [Zn(SO₄)(C₇H₈N₂O₂)(H₂O)₂]_n, the complex cations are linked by sulfate­ counter-ions into helical polymeric chains extending along the b axis. Each helix is stabilized by six intrachain hydrogen bonds involving stronger O-H...O (1.83-2.06 Å) and weaker N-H...O (2.20-2.49 Å) interactions. The Zn^II atom displays a distorted octahedral geometry formed by the 4-hy­droxy­benzo­hydrazide ligand, two water molecules and two SO₄^2- ions, which is very similar to the metal-atom environment in a previously reported Co^II complex [Zaslona, Drozdzewski & Kubiak (2010). J. Mol. Struct. 982, 1-8], especially the Zn-O and Zn-N bond lengths of 2.0453 (12)-2.1602 (9) and 2.1118 (12) Å, respectively.

S1. Comment

A novel zinc complex has been obtained during work attempting to enhance the biological activity of promising organic compounds through their binding with metal ions. 4-Hydroxybenzhydrazide (4hbah) is such a compound and exhibits moderate antimicrobial activity (Khan et al., 2003). Among many metals, those of biological importance were tested first and numerous syntheses with zinc were carried out. Of several zinc salts used, only in the case of sulfate were complex crystals obtained that were suitable for X-ray investigations. The important role of this anion in crystal formation is confirmed by the molecular structure of the title compound, (I).

As shown in Fig. 1, two coordination sites in the quasi-octahedral Zn^II environment of (I) are occupied by the O atoms of two sulfate groups. Since only one of these groups, Zn1—O6, may be attributed to the asymmetric unit, the second, Zn1—O3, is formed with a neighbouring sulfate anion. Thus, the sulfate anions act as bidentate bridging ligands linking the asymmetric units into a one-dimensional coordination polymer. The cis positions of the Zn1—O3 and Zn1—O6 bonds results in a nonlinear polymer chain conformation which has a helical structure, as shown in Fig. 2. Each helix extends along the b axis and winds around the 2₁ axis. As confirmed by the presence of inversion centres, right- and left-handed helices are present in the crystal structure in equal amounts. The shape and stability of the helices are also determined and additionally enhanced by six intrachain hydrogen bonds (Fig. 2 and Table 1). Five of these bonds have the sulfate O atoms as acceptors, which again confirms the important role of sulfate anions in the building up the crystal structure. A sixth hydrogen bond forms between a donor NH₂ group and an aqua group as acceptor. Four remaining hydrogen bonds link neighbouring helices. In these hydrogen bonds, the aqua and hydroxy groups act as donors and sulfate O atoms act as acceptors, except for one bond where the hydroxy group acts as an acceptor.

The presence of an aromatic ring in the organic ligand suggests the possibility of other interchain interactions. Inspection of the crystal packing (Fig. 3) reveals that the mutual orientation of aromatic rings belonging to different helices is suitable for π-stacking face-to-face interactions. The shortest distance between aromatic ring centroids [symmetry operator (-x + 1, -y + 1, -z + 1)] is 3.771 (2) Å with a displacement angle of 25.1°. Both values are similar to those most frequently found for this type of interaction (Janiak, 2000).

Complex (I) appears to be isostructural with a previously reported cobalt(II) complex with the same organic ligand (Zasłona et al., 2010). Since the main difference between these two compounds is the metal cation, it is interesting to compare the respective structural parameters of the metal coordination environment, where some differences are expected due to the different ionic radii of the coordinated metals. Literature data for Zn^II and Co^II ionic radii are not unambiguous, and according to some references both metals, as 2+ cations, have the same radius of 0.75 Å (Marcus, 1988, 1991). However, in a more recent report (Lide, 2002) different values are listed, namely 0.74 Å for Zn²⁺ and 0.65 Å for Co²⁺. In the complexes discussed here, the M—N1 bond length is 2.111 (1) [2.1118 (12) Å for Zn. Exact value for Co?] and is the same in both complexes, whereas the second coordination bond M—O2 of the organic ligand differs slightly from 2.0997 (12) for the Zn complex to 2.091 (1) Å for the Co complex, which supports the literature data where the ionic radii of Zn²⁺ and Co²⁺ are the same. The corresponding M—OH₂ and M—OSO₃ bond lengths differ more, as they additionally depend on the location of whole sulfate anions and water molecules in the crystal structure, which in turn results partially from the complicated system of hydrogen bonds and weak intra- and intermolecular interactions.

Related literature

For related literature, see: Janiak (2000); Khan et al. (2003); Lide (2002); Marcus (1988, 1991); Zasłona et al. (2010).

S2. Experimental

A solution of ZnSO₄ (0.10 mmol, 16 mg) in water (3 ml) was added to 4hbah (0.10 mmol, 15 mg) dissolved in a hot methanol–water mixture (5 ml, 3:2 v/v). The resulting warm colourless solution was filtered twice through soft filter paper and stored in a tightly closed flask at room temperature. Plate-shaped transparent crystals of (I) suitable for X-ray analysis were grown over the course of 2 d. The crystals were filtered off and washed with methanol. Elemental analysis, calculated for C₇H₁₂N₂O₈SZn: N 7.77, C 23.87, H 3.14, S 9.02%; found: N 8.01, C 23.90, H 3.46, S 9.17%.

S3. Refinement

All H atoms were found in difference Fourier maps. In the final refinement cycles, the hydroxy and N- and C-bonded H atoms were positioned geometrically and treated as riding atoms, with C—H = 0.95 Å, N—H = 0.88–0.92 Å and O—H = 0.84 Å, and with U_iso(H) = 1.2U_eq(N,C) or 1.5U_eq(O). Aqua H atoms were refined with O—H distance restraints of 0.840 (2) Å and then the AFIX3 instruction was used [Please rephrase in terms that are not software specific].

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. A view of the asymmetric unit of (I), showing the atom-numbering scheme and complete sulfate groups. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) -x, y + 1/2, -z + 1/2; (vii) -x, y - 1/2, -z + 1/2.]
	Fig. 2. The polymeric chain in (I), showing the helical arrangement of Zn1 and S1 atoms. For clarity, only one example of the intra-chain hydrogen bond has been shown in the upper part of the polymer helix. The hydrogen bonds are indicated by dashed lines and numbered according to the order of their appearance in Table 1.
	Fig. 3. The crystal packing in (I), viewed down the b axis. Interactions between the centroids (shown as small spheres) of the aromatic rings at the centre of the unit cell are represented by dashed lines.

catena-poly[[diaqua(4-hydroxybenzohydrazide)zinc(II)]-µ-sulfato]

Crystal data

[Zn(SO4)(C7H8N2O2)(H2O)2]	F(000) = 712
Mr = 349.62	Dx = 2.032 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.365 (5) Å	Cell parameters from 5510 reflections
b = 5.714 (3) Å	θ = 2.8–36.9°
c = 15.357 (3) Å	µ = 2.37 mm^−1
β = 102.98 (3)°	T = 100 K
V = 1142.8 (8) Å^3	Plates, colourless
Z = 4	0.22 × 0.18 × 0.14 mm

Data collection

Kuma KM-4 CCD area-detector diffractometer	5510 independent reflections
Radiation source: fine-focus sealed tube	4565 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.030
/w scans	θmax = 36.9°, θmin = 2.8°
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2007)	h = −22→22
Tmin = 0.615, Tmax = 0.715	k = −9→9
21561 measured reflections	l = −25→18

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)] = 0.026	Hydrogen site location: difference Fourier map
wR(F^2) = 0.068	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0411P)^2] where P = (Fo^2 + 2Fc^2)/3
5510 reflections	(Δ/σ)max < 0.001
177 parameters	Δρmax = 0.67 e Å^−3
0 restraints	Δρmin = −0.36 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	0.113838 (9)	0.48112 (2)	0.158170 (8)	0.00814 (4)
S1	−0.108659 (19)	0.74324 (4)	0.136258 (17)	0.00731 (5)
O1	0.70768 (7)	0.47548 (16)	0.47986 (6)	0.01559 (17)
H10	0.7231	0.5796	0.5192	0.023*
O2	0.27111 (6)	0.44257 (14)	0.21539 (5)	0.01074 (14)
O3	0.07779 (6)	0.28240 (15)	0.26682 (5)	0.01116 (14)
O4	0.14218 (7)	0.64414 (15)	0.04622 (5)	0.01467 (16)
O5	0.09255 (6)	0.16349 (14)	0.09531 (5)	0.01063 (14)
O6	−0.04719 (6)	0.54011 (14)	0.11485 (6)	0.01014 (14)
O7	−0.21859 (6)	0.68493 (14)	0.10719 (5)	0.01075 (14)
O8	−0.08717 (7)	0.95226 (14)	0.08698 (6)	0.01232 (15)
N1	0.14337 (7)	0.77635 (17)	0.24279 (6)	0.01091 (16)
H11	0.1369	0.9111	0.2092	0.013*
H12	0.0970	0.7823	0.2789	0.013*
N2	0.24424 (7)	0.75765 (17)	0.29552 (6)	0.01174 (17)
H20	0.2673	0.8568	0.3393	0.014*
C1	0.41014 (8)	0.56763 (19)	0.33133 (7)	0.00982 (17)
C22	0.30395 (8)	0.58408 (19)	0.27691 (7)	0.00911 (17)
C3	0.56597 (9)	0.3375 (2)	0.37178 (8)	0.01267 (19)
H3	0.6034	0.1993	0.3657	0.015*
C5	0.55699 (8)	0.7183 (2)	0.43891 (8)	0.01245 (19)
H5	0.5886	0.8397	0.4778	0.015*
C4	0.61088 (8)	0.51345 (19)	0.43101 (8)	0.01136 (19)
C2	0.46647 (8)	0.3659 (2)	0.32190 (7)	0.01150 (18)
H2A	0.4362	0.2475	0.2810	0.014*
C6	0.45688 (8)	0.74383 (19)	0.38963 (7)	0.01196 (19)
H6	0.4198	0.8825	0.3956	0.014*
H42W	0.1928	0.7324	0.0481	0.038 (6)*
H41W	0.1123	0.6070	−0.0061	0.026 (5)*
H51W	0.1067	0.1304	0.0462	0.028 (5)*
H52W	0.0369	0.0931	0.0933	0.031 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.00752 (6)	0.00799 (6)	0.00837 (6)	−0.00030 (4)	0.00065 (4)	−0.00067 (4)
S1	0.00647 (10)	0.00753 (10)	0.00758 (10)	−0.00006 (8)	0.00087 (8)	0.00017 (8)
O1	0.0081 (3)	0.0196 (4)	0.0164 (4)	0.0027 (3)	−0.0029 (3)	−0.0066 (3)
O2	0.0086 (3)	0.0114 (3)	0.0112 (3)	0.0003 (3)	0.0001 (3)	−0.0031 (3)
O3	0.0112 (3)	0.0141 (4)	0.0075 (3)	−0.0013 (3)	0.0008 (3)	0.0024 (3)
O4	0.0190 (4)	0.0154 (4)	0.0089 (3)	−0.0076 (3)	0.0017 (3)	−0.0005 (3)
O5	0.0117 (3)	0.0102 (3)	0.0105 (3)	−0.0022 (3)	0.0036 (3)	−0.0021 (3)
O6	0.0088 (3)	0.0104 (3)	0.0104 (3)	0.0024 (3)	0.0004 (3)	−0.0024 (3)
O7	0.0064 (3)	0.0123 (3)	0.0126 (3)	−0.0017 (3)	0.0000 (3)	0.0012 (3)
O8	0.0110 (4)	0.0106 (3)	0.0149 (4)	−0.0016 (3)	0.0020 (3)	0.0042 (3)
N1	0.0078 (4)	0.0114 (4)	0.0122 (4)	0.0016 (3)	−0.0005 (3)	−0.0016 (3)
N2	0.0080 (4)	0.0126 (4)	0.0129 (4)	0.0016 (3)	−0.0015 (3)	−0.0046 (3)
C1	0.0075 (4)	0.0109 (4)	0.0104 (4)	0.0003 (3)	0.0006 (3)	−0.0008 (3)
C22	0.0083 (4)	0.0096 (4)	0.0093 (4)	−0.0002 (3)	0.0019 (3)	0.0001 (3)
C3	0.0102 (4)	0.0131 (5)	0.0138 (5)	0.0022 (4)	0.0010 (4)	−0.0035 (4)
C5	0.0098 (4)	0.0127 (4)	0.0133 (5)	−0.0005 (4)	−0.0006 (4)	−0.0037 (4)
C4	0.0079 (4)	0.0141 (5)	0.0112 (5)	0.0005 (3)	0.0002 (3)	−0.0008 (4)
C2	0.0095 (4)	0.0123 (4)	0.0120 (5)	0.0005 (3)	0.0010 (4)	−0.0025 (4)
C6	0.0103 (4)	0.0110 (4)	0.0138 (5)	0.0013 (3)	0.0008 (4)	−0.0022 (4)

Geometric parameters (Å, º)

Zn1—O5	2.0453 (12)	O5—H52W	0.84
Zn1—O4	2.0638 (9)	N1—N2	1.4121 (14)
Zn1—O2	2.0997 (12)	N1—H11	0.9200
Zn1—N1	2.1118 (12)	N1—H12	0.9200
Zn1—O6	2.1319 (12)	N2—C22	1.3433 (15)
Zn1—O3	2.1602 (9)	N2—H20	0.8800
S1—O3^i	1.4697 (9)	C1—C6	1.3980 (16)
S1—O7	1.4746 (10)	C1—C2	1.4017 (16)
S1—O8	1.4763 (10)	C1—C22	1.4795 (16)
S1—O6	1.5005 (10)	C3—C2	1.3871 (16)
O1—C4	1.3594 (15)	C3—C4	1.3975 (16)
O1—H10	0.8400	C3—H3	0.9500
O2—C22	1.2461 (14)	C5—C6	1.3891 (16)
O3—S1^ii	1.4697 (9)	C5—C4	1.3936 (16)
O4—H42W	0.84	C5—H5	0.9500
O4—H41W	0.84	C2—H2A	0.9500
O5—H51W	0.84	C6—H6	0.9500
O5—Zn1—O4	92.26 (4)	N2—N1—Zn1	108.35 (7)
O5—Zn1—O2	97.15 (4)	N2—N1—H11	110.0
O4—Zn1—O2	92.42 (4)	Zn1—N1—H11	110.0
O5—Zn1—N1	170.47 (4)	N2—N1—H12	110.0
O4—Zn1—N1	96.21 (4)	Zn1—N1—H12	110.0
O2—Zn1—N1	78.18 (4)	H11—N1—H12	108.4
O5—Zn1—O6	88.24 (4)	C22—N2—N1	118.04 (9)
O4—Zn1—O6	91.72 (4)	C22—N2—H20	121.0
O2—Zn1—O6	173.06 (3)	N1—N2—H20	121.0
N1—Zn1—O6	95.84 (4)	C6—C1—C2	119.03 (10)
O5—Zn1—O3	82.33 (4)	C6—C1—C22	123.37 (10)
O4—Zn1—O3	174.36 (3)	C2—C1—C22	117.59 (10)
O2—Zn1—O3	89.86 (4)	O2—C22—N2	121.03 (10)
N1—Zn1—O3	89.31 (4)	O2—C22—C1	121.12 (10)
O6—Zn1—O3	86.53 (4)	N2—C22—C1	117.85 (10)
O3^i—S1—O7	112.02 (6)	C2—C3—C4	119.57 (11)
O3^i—S1—O8	110.69 (5)	C2—C3—H3	120.2
O7—S1—O8	108.84 (5)	C4—C3—H3	120.2
O3^i—S1—O6	107.26 (5)	C6—C5—C4	119.63 (10)
O7—S1—O6	108.43 (5)	C6—C5—H5	120.2
O8—S1—O6	109.54 (6)	C4—C5—H5	120.2
C4—O1—H10	109.5	O1—C4—C5	122.17 (10)
C22—O2—Zn1	113.47 (7)	O1—C4—C3	117.44 (10)
S1^ii—O3—Zn1	143.29 (5)	C5—C4—C3	120.40 (11)
Zn1—O4—H42W	122.7	C3—C2—C1	120.65 (10)
Zn1—O4—H41W	123.1	C3—C2—H2A	119.7
H42W—O4—H41W	113.0	C1—C2—H2A	119.7
Zn1—O5—H51W	126.1	C5—C6—C1	120.68 (10)
Zn1—O5—H52W	118.1	C5—C6—H6	119.7
H51W—O5—H52W	103.6	C1—C6—H6	119.7
S1—O6—Zn1	128.17 (5)
O5—Zn1—O2—C22	−163.35 (8)	Zn1—N1—N2—C22	7.38 (12)
O4—Zn1—O2—C22	104.06 (8)	Zn1—O2—C22—N2	−6.90 (13)
N1—Zn1—O2—C22	8.22 (8)	Zn1—O2—C22—C1	173.60 (8)
O3—Zn1—O2—C22	−81.10 (8)	N1—N2—C22—O2	−0.54 (16)
O5—Zn1—O3—S1^ii	136.19 (9)	N1—N2—C22—C1	178.98 (10)
O2—Zn1—O3—S1^ii	38.96 (9)	C6—C1—C22—O2	167.98 (11)
N1—Zn1—O3—S1^ii	−39.22 (9)	C2—C1—C22—O2	−10.74 (16)
O6—Zn1—O3—S1^ii	−135.12 (9)	C6—C1—C22—N2	−11.54 (16)
O3^i—S1—O6—Zn1	−47.28 (8)	C2—C1—C22—N2	169.74 (10)
O7—S1—O6—Zn1	−168.44 (6)	C6—C5—C4—O1	−177.68 (11)
O8—S1—O6—Zn1	72.91 (7)	C6—C5—C4—C3	2.08 (18)
O5—Zn1—O6—S1	175.84 (7)	C2—C3—C4—O1	178.58 (11)
O4—Zn1—O6—S1	−91.95 (7)	C2—C3—C4—C5	−1.19 (18)
N1—Zn1—O6—S1	4.47 (7)	C4—C3—C2—C1	−0.93 (17)
O3—Zn1—O6—S1	93.41 (7)	C6—C1—C2—C3	2.12 (17)
O4—Zn1—N1—N2	−99.00 (8)	C22—C1—C2—C3	−179.11 (10)
O2—Zn1—N1—N2	−7.82 (7)	C4—C5—C6—C1	−0.87 (18)
O6—Zn1—N1—N2	168.62 (7)	C2—C1—C6—C5	−1.21 (17)
O3—Zn1—N1—N2	82.18 (8)	C22—C1—C6—C5	−179.91 (11)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O3^iii	0.92	2.49	3.0678 (19)	121
N1—H11···O5^iii	0.92	2.24	3.1294 (15)	162
N1—H12···O3^i	0.92	2.28	2.9264 (17)	127
N1—H12···O6^i	0.92	2.40	3.1569 (15)	139
N2—H20···O7^i	0.88	2.20	2.9225 (16)	139
O5—H52W···O8^iv	0.84	1.83	2.6653 (14)	177
O1—H10···O7^v	0.84	1.94	2.7739 (15)	171
O4—H42W···O1^vi	0.84	2.03	2.8517 (15)	165
O4—H41W···O6^vii	0.84	1.90	2.7254 (14)	168
O5—H51W···O8^vii	0.84	2.06	2.8617 (13)	160

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