A pillared framework coordination polymer based on the Cd₃([mu]₃-OH) unit: poly[[([mu]₄-5-amino­tetra­zolato-[kappa]⁴N¹:N²:N³:N⁴)chlorido-[mu]₃-hydrox­ido-([mu]₃-isonicotinato-[kappa]³N:O:O')­dicadmium(II)] 0.14-hydrate]

The title coordination polymer, {[Cd₂(CH₂N₅)(C₆H₄NO₂)Cl(OH)]·0.14H₂O}_n, (I), was synthesized by the reaction of cadmium acetate and N-(1H-tetra­zol-5-­yl)isonicotinamide in aqueous ammonia, using hydro­chloric acid to adjust the pH. Under hydro­thermal conditions, N-(1H-tetra­zol-5-­yl)iso­nico­tinamide slowly hydrolyzes to form isonicotinic acid (Hisonic) and 5-aminotetra­zole (Hatz). The deprotonated form of isonicotinic acid (denoted isonic) acts as a bridging ligand in the structure. The polymer crystallizes in the monoclinic space group C2/m. In the structure, there is one Cd₃([mu]₃-OH) unit of C_s symmetry, with one of the Cd^II atoms and the O and H atoms located on a mirror plane. The other crystallographically independent Cd^II cation is located on an inversion centre. Each edge of the Cd₃([mu]₃-OH) isosceles triangle is bridged by an atz ligand in a [mu]_1,2 or [mu]_2,3/[mu]_3,4 mode. The Cd₃([mu]₃-OH) units are laced around with a belt of chloride ligands. The belts are further connected into undulating layers via weak inter-belt Cd-Cl bonds. The two organic ligands reside across mirror planes. The construction of a three-dimensional framework is completed by the pillaring isonic ligand. Water mol­ecules partially occupy the voids of the framework.

S1. Introduction

The current inter­est in the crystal engineering of coordination polymer frameworks, more commonly known as metal–organic frameworks (MOFs), not only stems from their intriguing variety of architectures and topologies, but also from their potential applications in the areas of nonlinear optics, catalysis, magnetism, luminescence, gas storage and biological recognition (Rao et al., 2004; Wang, Qin, Wang, Li et al., 2004; Wang, Qin, Wang, Xu et al., 2004; Wang, Zhang et al., 2004; Dybtsev et al., 2006; He et al., 2005; Koh et al., 2009). Despite significant progress in the synthesis of numerous polymeric metal–organic coordination networks in recent years, it is still a challenging task to explore a generally successful approach to predict and control the structures of coordination networks assembled from a particular combination of metal centres and bridging ligands (Evans & Lin; 2000; Yao et al., 2009; Fang et al., 2008). MOFs are primarily constructed from mononuclear metal centres and organic ligands, known as node and spacer, respectively, and this has resulted in a tremendous number of intriguing network topologies and a variety of packing motifs (Kitagawa et al., 2004; Bradshaw et al., 2005).

Recently, more attention has been paid to expanding the classical `Aufbau principles' to include polynuclear coordination clusters as building units, with the intention of utilizing them as nodes in the design of coordination polymers (Marin et al., 2004; Perry et al., 2007). This represents an extension of the classical `node-and-spacer' approach (Robson, 2000), giving rise to a family of cluster-based polymers with an enhanced variety of coordination geometries compared with single metal ions.

Poly-aza heterocyclic compounds have attracted considerable attention as useful ligands to produce coordination polymers with useful functional properties, such as gas storage (Zhang & Chen, 2008), magnetism (Ma et al., 2010; Wang et al., 2010) and catalysis (Wu et al., 2005). Among these poly-aza heterocyclic compounds, 5-amino-tetra­zole (Hatz) is a rigid multidentate organic ligand that potentially possesses the capability to bridge metal atoms in various coordination modes via the N atoms of the tetra­zole ring.

During our recent work on MOFs containing 5-amino-tetra­zole, we found that Cd₃(µ₃-OH) is a stable and easy-to-make polynuclear unit (Liu, Huang, Huang, Huang, Chen & You, 2009 OR Liu, Huang, Huang, Huang & Chen, 2009 ?; Su et al., 2009; Yao et al., 2009; Liang et al., 2011). In continuation of our inter­est in the design of coordination polymer frameworks utilizing polynuclear coordination clusters as building units, we present herein a new pillared framework coordination polymer, the title compound, (I), [Cd₂(OH)Cl(atz)(isonic)]_n.nxH₂O, where atz is 5-amino-tetra­zolate and isonic is isonicotinate. To the best of our knowledge, (I) represents the first example of three-dimensional coordination polymer framework constructed of Cd₂(µ₃-OH) belts, i.e. one-dimensional infinitely condensated [Concatenated?] Cd₃(µ₃-OH) units.

S2. Experimental

S2.1. Synthesis and crystallization

A mixture of Cd(CH₃COO)₂.3H₂O (0.026 g, 0.1 mmol), N-(1H-tetra­zol-5yl)isonicotinamide (0.038 g, 0.2 mmol), 0.5 M aqueous ammonia (1 ml) and hydro­chloric acid and H₂O (6 ml) was stirred for 30 min, sealed in a 23 ml Teflon-lined autoclave and heated in an oven to 393 K for 3 d. After the sample had been cooled to room temperature at a rate of 5 K h^-1, colourless block-shaped crystals of (I) were obtained in 34% yield based on Cd.

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. The hy­droxy H atom was located in a difference Fourier map and its position and U_iso were refined. The H atoms of the water molecule could not be found in a difference Fourier map due to its low occupancy. The remaining H atoms were refined in idealized positions using the riding-model approximation, with C—H = 0.93 Å and N—H = 0.86 Å, and with U_iso(H) = 1.2U_eq(C,N).

S3. Results and discussion

Single-crystal X-ray diffraction study of (I) reveals a three-dimensional coordination framework structure in the monoclinic space group C2/m. The asymmetric unit contains two crystallographically independent Cd^II cations, Cd1 and Cd2, located on a mirror plane and an inversion centre, respectively. The atz ligand and the isonic anion both reside on the mirror plane and possess Cs symmetry, in spite of their ideal C_2v point group symmetry. The Cl^- anion, the O atom of the hydroxyl anion and the partly occupied water molecule sit on a mirror plane.

As shown in Fig. 1, the hydroxyl anion in the structure bridges three Cd^II cations, Cd1 on a mirror plane and two mirror-related Cd2 and Cd2^iv [symmetry code: (iv) 1/2 - x, 1/2 + y, 1 - z], to form an OH-centred isosceles triangular Cd₃(µ₃-OH), with atom O2 deviating by 0.547 (3) Å from the plane of the three Cd^II cations. In the Cd₃(µ₃-OH) unit, the Cd1···Cd2 separation is 3.8764 (9) Å and the Cd2···Cd2^iv separation is 3.4986 (8) Å. Each edge of the isosceles triangular Cd₃(µ₃-OH) group is bridged by an atz ligand via a pair N atoms, to form a Cd₃(µ₃-OH)(atz)₃ unit. Since the Cd2 sites are exactly on an inversion centre, the inversion operation brings the Cd₃(µ₃-OH)(atz)₃ unit into a [Cd₂(OH)(atz)]_n belt extending along a direction (Fig. 2). In the backbone of the belt, the Cd2 atoms are bridged by OH groups to form a zigzag chain, while along both edges of the belt, Cd1 atoms are connected to each other by atz ligands. Every atz ligand bridges two Cd1 and two Cd2 atoms, using all N atoms of its tetra­zole ring. The belt is laced with Cl^- anions, with a Cd1—Cl1 bond length of 2.5086 (14) Å. The belts are further connected into undulating layers via weak inter-belt Cd—Cl bonds (Fig. 3), with Cd1—Cl1^viii = 2.9960 (15) Å.

The construction of the three-dimensional framework of (I) is completed by pillaring with the isonic ligand. The carboxyl­ate O atoms of the isonic ligand coordinate to two mirror-related Cd2 atoms of the Cd₃(µ₃-OH) core in a syn–syn mode, while the pyridine N atom of the isonic ligand connects to atoms Cd1 in neighbouring layers (Fig. 4). The coordination geometry around both Cd1 and Cd2 atoms can be described as a slightly distorted o­cta­hedron. Cd1 is coordinated by a µ₃-OH group, two N atoms from two atz units [N2 and N2ⁱⁱ; symmetry code: (ii) x, -y + 1, z], one Cl^- anion in the equatorial plane, and one pyridyl N atom [N1ⁱ; symmetry code: (i) x + 1/2, y + 1/2, z] of an isonic ligand and one Cl^- anion [Cl1^viii; symmetry code: (viii) -x, y, -z] in the axial positions. The Cd1—N1ⁱ/N2/N2ⁱⁱ distances range from 2.362 (3) to 2.3978 (18) Å, and the Cd1—O2 and Cd1—Cl1 distances are 2.256 (2) and 2.5086 (14) Å, respectively. All these values are in good agreement with those typically observed in related Cd^II polymeric structures (Yang et al., 2009; Ji et al., 2010). The Cd—Cl1^viii distance is 2.9960 (15) Å, which is longer than in the previously reported Cd^II complex (Liu, Huang, Huang, Huang, Chen & You, 2009 OR Liu, Huang, Huang, Huang & Chen, 2009 ?). The Cd2 cation is equatorially coordinated by two carboxyl­ate O atoms [O1 and O1ⁱⁱⁱ; symmetry code: (iii) -x + 1/2, -y + 1/2, -z + 1] from two isonic groups and two O atoms [O2 and O2^vii; symmetry code: (vii) -x + 1/2, y - 1/2, -z + 1] of two µ₃-OH groups. The axial positions are occupied by two N atoms (N3, N3ⁱⁱⁱ) from two atz units, with a Cd2—N3 distance of 2.3627 (18) Å, forming an o­cta­hedral coordination environment. The Cd2—O distances range from 2.2301 (14) to 2.2832 (17) Å.

The solid-state photoluminescent spectrum of (I) at room temperature is depicted in Fig. 6. The fluorescence spectrum shows that (I) exhibits a broad emission with a maximum wavelength of 447 nm upon excitation at 328 nm. The main chromophore of this compound is the aromatic five-membered ring and its photoluminescence is assigned as originating from π–π* transitions (Liang et al., 2010).

Related literature

For related literature, see: Bradshaw et al. (2005); Dybtsev et al. (2006); Evans & Lin (2000); Fang et al. (2008); He et al. (2005); Ji et al. (2010); Kitagawa et al. (2004); Liang et al. (2011); Liu, Huang, Huang, Huang & Chen (2009); Liu, Huang, Huang, Huang, Chen & You (2009); Ma et al. (2010); Marin et al. (2004); Perry IV, Kravtsov, McManus & Zaworotko (2007); Rao et al. (2004); Robson (2000); Su et al. (2009); Wang et al. (2010); Wang, Qin, Wang, Li, Hu & Xu (2004); Wang, Qin, Wang, Xu, Su & Hu (2004); Wang, Zhang, Fujiwara, Kobayashi & Kurmoo (2004); Wu et al. (2005); Yang et al. (2009); Yao et al. (2009); Zhang & Chen (2008).

Computing details

Data collection: CrystalClear (Rigaku, 2002); cell refinement: CrystalClear (Rigaku, 2002); data reduction: CrystalClear (Rigaku, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).

Figures

	Fig. 1. The coordination environment of the Cd cations in (I), showing the atom-labelling scheme and 50% probability displacement ellipsoids. The partionally occupied water molecule is not shown. [Symmetry codes: (i) x + 1/2, y + 1/2, z; (ii) x, -y + 1, z; (iii) -x + 1/2, -y + 1/2, -z + 1; (iv) -x + 1/2, y + 1/2, -z + 1; (v) x, -y, z; (vii) -x + 1/2, y - 1/2, -z + 1; (viii) -x, y, -z; (ix) x, y + 1, z.]
	Fig. 2. A view of the one-dimensional [Cd2(OH)(atz)]n belt, laced with Cl anions, of (I), along the a axis. H atoms have been omitted for clarity.
	Fig. 3. (Top) A view of the two-dimensional undulating layers of (I), formed via weak inter-belt Cd—Cl bonds (dashed lines?). H atoms have been omitted for clarity. (Bottom) [Please provide caption for bottom part of diagram]
	Fig. 4. (Left) A view of the two-dimensional undulating layers of (I), connected via the pillaring isonic ligand. H atoms have been omitted for clarity. (Right) [Please provide caption for right-hand side of diagram]
	Fig. 5. A view of the three-dimensional framework of (I), formed via weak Cd—Cl bonds and the pillaring isonic ligand. H atoms have been omitted for clarity.
	Fig. 6. The solid-state photoluminescent spectrum of (I).

Poly[[(µ₄-5-aminotetrazolato-κ⁴N¹:N²:N³:N⁴:)chlorido-µ₃-hydroxido-(µ₃-isonicotinato-κ³N:O:O')dicadmium(II)] 0.14-hydrate]

Crystal data

[Cd2(CH2N5)Cl(OH)(C6H4NO2)]·0.14H2O	Z = 4
Mr = 485.73	F(000) = 916
Monoclinic, C2/m	Dx = 2.426 Mg m^−3
Hall symbol: -C 2y	Mo Kα radiation, λ = 0.71073 Å
a = 19.479 (4) Å	µ = 3.41 mm^−1
b = 6.9971 (14) Å	T = 293 K
c = 13.235 (3) Å	Block, colourless
β = 132.52 (3)°	0.38 × 0.25 × 0.20 mm
V = 1329.5 (5) Å^3

Data collection

Rigaku Saturn 724 CCD area-detector diffractometer	1648 independent reflections
Radiation source: fine-focus sealed tube	1560 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ω scans	θmax = 27.5°, θmin = 3.1°
Absorption correction: multi-scan (RAPID-AUTO; Rigaku, 1998)	h = −25→25
Tmin = 0.721, Tmax = 1.000	k = −8→9
6579 measured reflections	l = −17→17

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)] = 0.017	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.040	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0159P)^2 + 3.1028P] where P = (Fo^2 + 2Fc^2)/3
1648 reflections	(Δ/σ)max = 0.001
110 parameters	Δρmax = 0.50 e Å^−3
0 restraints	Δρmin = −0.71 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	Occ. (<1)
Cd1	0.142115 (14)	0.5000	0.15898 (2)	0.01735 (7)
Cd2	0.2500	0.2500	0.5000	0.01643 (6)
Cl1	0.03699 (6)	0.5000	−0.09699 (8)	0.03204 (18)
O2	0.17633 (15)	0.5000	0.3594 (2)	0.0174 (4)
H2O	0.129 (3)	0.5000	0.336 (4)	0.034 (12)*
O1	0.11061 (12)	0.1600 (3)	0.4294 (2)	0.0389 (4)
N1	−0.20907 (18)	0.0000	0.2310 (3)	0.0275 (6)
N2	0.14994 (12)	0.1579 (3)	0.17296 (17)	0.0198 (4)
N3	0.19917 (12)	0.0920 (2)	0.30163 (17)	0.0195 (3)
N4	0.0706 (2)	0.0000	−0.0400 (3)	0.0362 (7)
H4A	0.0552	0.1064	−0.0832	0.043*	0.50
H4B	0.0540	−0.1064	−0.0835	0.043*	0.50
C1	−0.16375 (19)	−0.1605 (4)	0.2569 (4)	0.0502 (8)
H1	−0.1944	−0.2756	0.2378	0.060*
C2	−0.07356 (19)	−0.1669 (4)	0.3106 (4)	0.0477 (8)
H2	−0.0450	−0.2838	0.3264	0.057*
C3	−0.0265 (2)	0.0000	0.3404 (3)	0.0231 (6)
C4	0.0739 (2)	0.0000	0.4051 (3)	0.0246 (6)
C5	0.1208 (2)	0.0000	0.0960 (3)	0.0184 (5)
OW1	0.0787 (14)	0.5000	0.524 (2)	0.039 (7)	0.142 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.01721 (11)	0.01260 (11)	0.01646 (11)	0.000	0.00906 (9)	0.000
Cd2	0.01664 (11)	0.01085 (10)	0.01597 (10)	−0.00122 (7)	0.00867 (9)	−0.00030 (7)
Cl1	0.0254 (4)	0.0358 (4)	0.0165 (3)	0.000	0.0068 (3)	0.000
O2	0.0149 (10)	0.0151 (10)	0.0160 (9)	0.000	0.0079 (8)	0.000
O1	0.0232 (8)	0.0355 (10)	0.0571 (12)	−0.0047 (7)	0.0268 (9)	−0.0016 (9)
N1	0.0183 (12)	0.0269 (14)	0.0360 (15)	0.000	0.0178 (12)	0.000
N2	0.0216 (8)	0.0155 (9)	0.0184 (8)	−0.0005 (7)	0.0119 (7)	0.0011 (7)
N3	0.0246 (9)	0.0127 (8)	0.0167 (8)	−0.0004 (7)	0.0122 (7)	0.0001 (7)
N4	0.056 (2)	0.0195 (14)	0.0204 (14)	0.000	0.0207 (14)	0.000
C1	0.0318 (14)	0.0247 (13)	0.095 (3)	−0.0053 (11)	0.0429 (17)	−0.0072 (14)
C2	0.0304 (13)	0.0265 (13)	0.089 (2)	0.0022 (11)	0.0417 (16)	−0.0002 (14)
C3	0.0160 (13)	0.0295 (16)	0.0253 (15)	0.000	0.0145 (12)	0.000
C4	0.0166 (14)	0.0336 (17)	0.0236 (15)	0.000	0.0136 (13)	0.000
C5	0.0200 (13)	0.0163 (13)	0.0164 (13)	0.000	0.0113 (12)	0.000
OW1	0.049 (13)	0.020 (9)	0.070 (15)	0.000	0.049 (12)	0.000

Geometric parameters (Å, º)

Cd1—O2	2.256 (2)	N1—Cd1^vi	2.362 (3)
Cd1—N1^i	2.362 (3)	N2—C5	1.341 (2)
Cd1—N2^ii	2.3978 (18)	N2—N3	1.351 (2)
Cd1—N2	2.3978 (18)	N3—N3^v	1.287 (3)
Cd1—Cl1	2.5086 (14)	N4—C5	1.348 (4)
Cd2—O2^iii	2.2301 (14)	N4—H4A	0.8600
Cd2—O2	2.2301 (14)	N4—H4B	0.8600
Cd2—O1	2.2832 (17)	C1—C2	1.380 (3)
Cd2—O1^iii	2.2832 (17)	C1—H1	0.9300
Cd2—N3^iii	2.3627 (18)	C2—C3	1.367 (3)
Cd2—N3	2.3627 (18)	C2—H2	0.9300
O2—Cd2^iv	2.2301 (14)	C3—C2^v	1.367 (3)
O2—H2O	0.75 (4)	C3—C4	1.515 (4)
O1—C4	1.248 (2)	C4—O1^v	1.248 (2)
N1—C1^v	1.322 (3)	C5—N2^v	1.341 (2)
N1—C1	1.322 (3)
O2—Cd1—N1^i	102.65 (10)	Cd1—O2—H2O	102 (3)
O2—Cd1—N2^ii	87.50 (4)	C4—O1—Cd2	131.97 (17)
N1^i—Cd1—N2^ii	88.41 (4)	C1^v—N1—C1	116.3 (3)
O2—Cd1—N2	87.50 (4)	C1^v—N1—Cd1^vi	121.79 (15)
N1^i—Cd1—N2	88.41 (4)	C1—N1—Cd1^vi	121.79 (15)
N2^ii—Cd1—N2	173.35 (8)	C5—N2—N3	104.56 (17)
O2—Cd1—Cl1	155.59 (6)	C5—N2—Cd1	142.34 (14)
N1^i—Cd1—Cl1	101.76 (8)	N3—N2—Cd1	113.09 (12)
N2^ii—Cd1—Cl1	93.18 (4)	N3^v—N3—N2	109.97 (11)
N2—Cd1—Cl1	93.18 (4)	N3^v—N3—Cd2	117.91 (4)
O2^iii—Cd2—O2	180.0	N2—N3—Cd2	130.41 (13)
O2^iii—Cd2—O1	92.39 (8)	C5—N4—H4A	120.0
O2—Cd2—O1	87.61 (8)	C5—N4—H4B	120.0
O2^iii—Cd2—O1^iii	87.61 (8)	H4A—N4—H4B	120.0
O2—Cd2—O1^iii	92.39 (8)	N1—C1—C2	123.7 (3)
O1—Cd2—O1^iii	180.00 (10)	N1—C1—H1	118.1
O2^iii—Cd2—N3^iii	83.66 (6)	C2—C1—H1	118.1
O2—Cd2—N3^iii	96.34 (6)	C3—C2—C1	119.5 (2)
O1—Cd2—N3^iii	94.18 (7)	C3—C2—H2	120.3
O1^iii—Cd2—N3^iii	85.82 (7)	C1—C2—H2	120.3
O2^iii—Cd2—N3	96.34 (6)	C2—C3—C2^v	117.3 (3)
O2—Cd2—N3	83.66 (6)	C2—C3—C4	121.35 (15)
O1—Cd2—N3	85.82 (7)	C2^v—C3—C4	121.35 (15)
O1^iii—Cd2—N3	94.18 (7)	O1—C4—O1^v	127.6 (3)
N3^iii—Cd2—N3	180.0	O1—C4—C3	116.22 (15)
Cd2^iv—O2—Cd2	103.33 (9)	O1^v—C4—C3	116.22 (15)
Cd2^iv—O2—Cd1	119.57 (6)	N2—C5—N2^v	110.9 (2)
Cd2—O2—Cd1	119.57 (6)	N2—C5—N4	124.53 (12)
Cd2^iv—O2—H2O	105.2 (19)	N2^v—C5—N4	124.53 (12)
Cd2—O2—H2O	105.2 (19)

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