A three-dimensional chiral crystal structure constructed from a chiral triazolate ligand showing an SrSi₂ topology: poly[bis­([mu]₃-3,5-diethyl-1,2,4-triazolato-[kappa]³N¹:N²:N⁴)tris­ilver nitrate]

In the title metal-organic framework (MOF), {[Ag₃(C₆H₁₀N₃)₂]NO₃}_n, the Ag^I cation is coordinated by two N atoms from two different 3,5-diethyl-1,2,4-triazolate (detz) ligands in a linear configuration. Each Ag^I cation is then connected to two adjacent Ag^I cations via a [mu]₃-N¹:N²:N⁴-detrz ligand, resulting in a three-dimensional chiral silver-triazolate structure showing an SrSi₂ (srs) net with 10³ topology.

S1. Introduction

Metal–organic frameworks (MOFs), which consist of metal ions and organic struts connected via coordination bonds, have drawn considerable inter­est during the past decades because of their fascinating architectures as well as their promising applications, relating to their structure such as gas storage and separation, catalysis, sensors, and so on (Kitagawa et al., 2004; Biradha et al., 2011; Sumida et al., 2012; Jiang et al., 2011; Cui et al., 2012). Compared with other artificially synthesized crystalline materials, one of the unique properties of MOFs is the infinite structural possibilities based on the variety of nodes and linkers that can be derived from combining the various inorganic and organic fragments, respectively (Bonneau et al., 2004; Ockwig et al., 2005). A variety of structural networks in MOFs have been observed. Not only well known networks, such as dia, pcu, pts, rho and rlt (O'Keeffe, et al., 2008), but also unprecedented novel frameworks, such as xmz (Zhang et al., 2007), zxc (Chen et al., 2010) and fly (Yang et al. 2013), that are based on carefully designed multidentate ligands have been isolated. Due to the importance of the topologies in the synthesis of functional crystalline materials, more and more inter­est therefore has been paid to the pursuit of novel structures and topologies in the self-assembled systems.

3,5-Disubstituted-1,2,4-triazolates are rigid conjugated ligands with simple coordination geometry, generally showing exodentate µ₃-N¹:N²:N⁴-coordi­antion (Zhang et al., 2012). The silver(I) ion is one of the metal ions that shows simple coordination geometries, such as linear, T- or Y-shaped and square-planar or tetra­hedral coordinations for 2-, 3- and 4-coordinated Ag^I atoms. Although the Ag^I and 3,5-disubstituted-1,2,4-triazolates are very simple in their coordination geometries, a diverse range of structures based on them have been successfully isolated previously, including dia, CdSO₄ and nbo (Zhang et al., 2012; Yang et al., 2009; Ling et al., 2011). It has been shown that alongside the reaction conditions (such as temperature, solvent etc.), the 3,5-disubstituted groups also play a significant role in determining the resulting coordination configuration of the silver–triazolates (Zhang et al., 2012), thus leading to differences in their topologies. However, to the best of our knowledge, chiral structures built of silver ions and achiral triazolates are not known. Herein we report the synthesis and structure of a novel three-dimensional chiral structure built of silver and 3,5-di­ethyl-4H-1,2,4-triazole (Hdetz), the title compound, poly[bis­(µ₃-3,5-di­ethyl-1,2,4-triazolato-κ³N¹:N²:N⁴)tris­ilver nitrate], (I), which forms a 3-connected SrSi₂ net with 10³ topology.

S2. Experimental

S2.1. Synthesis and crystallization

3,5-Di­ethyl-4H-1,2,4-triazole (Hdetz) was prepared according to previously reported methods (Yang et al., 2009). Hdetz (0.0252 g, 0.2 mmol) was dissolved in the aceto­nitrile (5 ml), then the solution was added to the aqueous soultion (5 ml) containing silver nitrate (0.052 g, 0.3 mmol). The mixture was stirred at room temperature for 30 min. Then toluene (1 ml) was added. The mixture was then transferred into a 15 ml Teflon-lined Parr bomb and heated at 433 K for 3 d. The reaction mixture was allowed to cool to room temperature. Needle-like colourless crystals of (I) were obtained by filtration (yield: 45%, based on Hdetz). Analysis calculated (found) for C₁₂H₂₀Ag₃N₇O₃ (%): C 22.74 (22.67), H 3.18 (3.23), N 15.47 (15.53). IR spectrum for (I) (KBr, cm^-1): 2960 (m), 2920 (w), 2860 (w), 1580 (m), 1500 (m), 1470 (s), 1440 (m), 1360(m), 1311 (m), 1287 (m), 1240 (m), 1050 (m), 970 (w), 864 (w), 787 (w), 742 (w).

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. All H atoms were positioned geometrically and refined using a riding model, with C—H = 0.96 Å and U_iso(H) = 1.2U_eq(C) for methyl H atoms, and C—H = 0.97 Å and U_iso(H) = 1.2U_eq(C) for methyl­ene H atoms.

S3. Results and discussion

Compound (I) crystallizes in the tetra­gonal crystal system, in the chiral P4₃2₁2 space group. The asymmetric unit contains one and a half crystallographically unique Ag^I atoms, one detz ligand and a half an NO₃^- anion. The structural motif of (I) with the coordination environment of the Ag^I cations is shown in Fig. 1. Ag1 is coordinated by two N atoms from two detz ligands. The Ag1—N1 and Ag1—N2ⁱ [symmetry code: (i) y+1/2, -x+1/2, z+1/4] bond lengths are 2.137 (4) and 2.124 (4) Å, respectively. The N1—Ag1—N2ⁱ angle of 157.09 (15)° indicates that the coordination mode of Ag1 deviates from the ideal linear environment. The distance of Ag2—N3 is 2.118 (3) Å and the N3—Ag2—N3ⁱⁱ [symmetry code: (ii) y, x, -z] angle is 161.4 (2)°. All the Ag—N bond lengths are in agreement with those observed previously in silver–triazolate compounds (Ling et al.,2011; Yang et al., 2009). The distance between Ag atoms connected by detz ligands in a µ_1,4-mode is 6.2455 (23) Å and the Ag···Ag distance between Ag^I ions bridged by detz in a µ_1,2-mode is 3.600 (3) Å. The connections of Ag1—N by detz in a µ_1,4-mode generate an one dimensional chain (Fig. 2). These chains are further connected to each other by Ag2—N bonds, resulting in the generation of a three-dimensional cationic framework. It is inter­esting to note that the NO₃^- anion is weakly chelated to the neighbouring three Ag^I ions, with the average Ag···O distance of ca. 2.84 Å, thus forming a trinuclear silver–nitrate motif. The 3,5-disubsitituted ethyl groups on the triazolate stretch into the channel running along the [110] direction. The Flack parameter is -0.02 (4), confirming the chirality of the crystal structure of (I). To structurally analyze the network of (I), the infinite three-dimensional framework is best described as a 3-connected network with point symbol of 10³. The TOPOS program (Blatov, 2006) regards this network as SrSi₂ net, considering detz ligands as 3-connected nodes and Ag^I ions as linear linkers (Fig. 3). This structure is different from a previously reported Ag–detz compound, (II), which is crystallizes in the C2/c space group and has a (4,6)-connected net (Yang et al., 2009). The difference can be ascribed to different coordination geometry of Ag^I ions, which is almost linear in (I) and Y-shaped in (II).

Thus, the title compound is a new example of a silver–triazolate compound showing a chiral structure consisting of achiral ligand and featuring the SrSi₂ net with point symbol of 10³.

Related literature

For related literature, see: Biradha et al. (2011); Blatov (2006); Bonneau et al. (2004); Brandenburg & Berndt (2005); Bruker (2003); Chen et al. (2010); Cui et al. (2012); Jiang & Xu (2011); Kitagawa et al. (2004); Ling et al. (2011); O'Keeffe et al. (2008); Ockwig et al. (2005); Sheldrick (2008, 2008); Sumida et al. (2012); Westrip (2010); Yang et al. (2009, 2013); Zhang et al. (2007, 2012).

Computing details

Data collection: SMART (Bruker, 2003); cell refinement: SMART (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg & Berndt, 2005); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Figures

	Fig. 1. The coordination environment of the Ag1 and Ag 2 cations in (I), showing the atomic labels. Displacement ellipsoids are drawn at the 30% probability level and H atoms have been omitted for clarity. [Symmetry codes: (i) x, y, -z; (ii) y+1/2, -x+1/4, z+1/4.]
	Fig. 2. (a) A view of the structure of (I) along the [110] direction, showing the three-dimensional framework. H atoms and ethyl groups have been omitted for clarity. (b) A view the one-dimensional chain linked by Ag1—N bonds, with only the triazolate groups shown for simplicity. (c) The trinuclear silver motif with the nitrate anion. [Symmetry codes: (iii) -y+1/2, x-1/2, z-1/4; (iv) x-1/2, -y+3/2, -z+1/4; (v) -y, -x+1, -z+1/2.]
	Fig. 3. A schematic representation of the typical for SrSi2 net topology of (I) showing along the c axis.

Poly[bis(µ₃-3,5-diethyl-1,2,4-triazolato-κ³N¹:N²:N⁴)trisilver nitrate]

Crystal data

[Ag3(C6H10N3)2]NO3	Dx = 2.297 Mg m^−3
Mr = 633.96	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43212	Cell parameters from 907 reflections
a = 8.628 (3) Å	θ = 2.6–27.7°
c = 24.621 (10) Å	µ = 3.20 mm^−1
V = 1832.8 (15) Å^3	T = 293 K
Z = 4	Needle, colourless
F(000) = 1224	0.18 × 0.15 × 0.12 mm

Data collection

Bruker SMART CCD area-detector diffractometer	1606 reflections with I > 2σ(I)
phi and ω scans	Rint = 0.088
Absorption correction: multi-scan (SADABS; Bruker, 2003)	θmax = 25.2°, θmin = 2.5°
Tmin = 0.721, Tmax = 1.000	h = −10→10
9189 measured reflections	k = −7→10
1656 independent reflections	l = −28→29

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.029	w = 1/[σ^2(Fo^2) + (0.0301P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.063	(Δ/σ)max < 0.001
S = 1.06	Δρmax = 0.64 e Å^−3
1656 reflections	Δρmin = −0.72 e Å^−3
115 parameters	Absolute structure: Flack x determined using 577 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons and Flack (2004), Acta Cryst. A60, s61).
0 restraints	Absolute structure parameter: −0.02 (4)

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ag1	0.38813 (6)	0.04977 (6)	0.23870 (2)	0.04307 (17)
Ag2	0.25605 (6)	0.25605 (6)	0.0000	0.0473 (2)
C1	0.4257 (7)	−0.0585 (7)	0.11530 (19)	0.0365 (14)
C2	0.5055 (11)	−0.2094 (9)	0.1280 (3)	0.062 (2)
H2A	0.4325	−0.2924	0.1207	0.074*
H2B	0.5905	−0.2212	0.1026	0.074*
C3	0.5659 (12)	−0.2331 (10)	0.1814 (3)	0.090 (3)
H3A	0.6132	−0.3337	0.1835	0.135*
H3B	0.4832	−0.2265	0.2074	0.135*
H3C	0.6420	−0.1550	0.1892	0.135*
C4	0.3092 (7)	0.1567 (7)	0.1214 (2)	0.0361 (14)
C5	0.2365 (9)	0.2986 (9)	0.1433 (2)	0.0544 (19)
H5A	0.1569	0.2693	0.1692	0.065*
H5B	0.1866	0.3542	0.1139	0.065*
C6	0.3507 (11)	0.4053 (10)	0.1710 (4)	0.080 (3)
H6A	0.2973	0.4951	0.1844	0.121*
H6B	0.4286	0.4368	0.1454	0.121*
H6C	0.3989	0.3519	0.2007	0.121*
N1	0.3708 (6)	0.0431 (6)	0.15213 (17)	0.0344 (11)
N2	0.4020 (6)	−0.0100 (5)	0.06543 (16)	0.0343 (11)
N3	0.3278 (6)	0.1284 (6)	0.06898 (16)	0.0370 (11)
N4	0.0304 (7)	−0.0304 (7)	0.2500	0.0490 (19)
O1	−0.1082 (6)	−0.0668 (6)	0.2428 (2)	0.0726 (15)
O2	0.1319 (6)	−0.1319 (6)	0.2500	0.0586 (18)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.0604 (3)	0.0516 (3)	0.0172 (2)	0.0044 (2)	−0.0073 (2)	−0.00063 (18)
Ag2	0.0601 (3)	0.0601 (3)	0.0216 (3)	0.0142 (4)	−0.00787 (18)	0.00787 (18)
C1	0.048 (4)	0.039 (3)	0.023 (3)	−0.003 (3)	−0.006 (2)	−0.001 (2)
C2	0.105 (7)	0.040 (4)	0.041 (4)	0.012 (5)	−0.012 (4)	0.001 (3)
C3	0.120 (9)	0.069 (6)	0.082 (5)	0.033 (6)	−0.052 (6)	−0.010 (5)
C4	0.038 (3)	0.050 (4)	0.020 (2)	0.003 (3)	−0.002 (2)	0.002 (2)
C5	0.067 (5)	0.063 (5)	0.034 (3)	0.022 (4)	0.001 (3)	−0.003 (3)
C6	0.107 (8)	0.050 (5)	0.084 (6)	0.014 (5)	−0.007 (5)	−0.015 (5)
N1	0.045 (3)	0.041 (3)	0.0166 (19)	0.000 (2)	−0.002 (2)	0.0032 (19)
N2	0.051 (3)	0.037 (3)	0.0145 (19)	−0.001 (2)	−0.0023 (19)	−0.0022 (18)
N3	0.046 (3)	0.047 (3)	0.0182 (19)	0.008 (2)	−0.0062 (19)	0.002 (2)
N4	0.056 (3)	0.056 (3)	0.034 (4)	−0.007 (4)	0.000 (2)	0.000 (2)
O1	0.049 (3)	0.079 (4)	0.090 (4)	−0.015 (3)	0.000 (3)	−0.011 (3)
O2	0.055 (3)	0.055 (3)	0.065 (4)	−0.002 (4)	0.003 (2)	0.003 (2)

Geometric parameters (Å, º)

Ag1—N2^i	2.125 (4)	C4—N1	1.348 (7)
Ag1—N1	2.137 (4)	C4—C5	1.477 (9)
Ag2—N3	2.117 (4)	C5—C6	1.510 (11)
Ag2—N3^ii	2.117 (4)	C5—H5A	0.9700
C1—N2	1.313 (7)	C5—H5B	0.9700
C1—N1	1.347 (7)	C6—H6A	0.9600
C1—C2	1.506 (10)	C6—H6B	0.9600
C2—C3	1.429 (10)	C6—H6C	0.9600
C2—H2A	0.9700	N2—N3	1.358 (7)
C2—H2B	0.9700	N2—Ag1^iii	2.125 (4)
C3—H3A	0.9600	N4—O2	1.237 (11)
C3—H3B	0.9600	N4—O1	1.249 (6)
C3—H3C	0.9600	N4—O1^iv	1.249 (6)
C4—N3	1.324 (7)
N2^i—Ag1—N1	157.06 (19)	C6—C5—H5A	109.0
N3—Ag2—N3^ii	161.4 (3)	C4—C5—H5B	109.0
N2—C1—N1	111.6 (5)	C6—C5—H5B	109.0
N2—C1—C2	122.7 (5)	H5A—C5—H5B	107.8
N1—C1—C2	125.7 (5)	C5—C6—H6A	109.5
C3—C2—C1	118.8 (6)	C5—C6—H6B	109.5
C3—C2—H2A	107.6	H6A—C6—H6B	109.5
C1—C2—H2A	107.6	C5—C6—H6C	109.5
C3—C2—H2B	107.6	H6A—C6—H6C	109.5
C1—C2—H2B	107.6	H6B—C6—H6C	109.5
H2A—C2—H2B	107.0	C1—N1—C4	103.6 (5)
C2—C3—H3A	109.5	C1—N1—Ag1	131.6 (4)
C2—C3—H3B	109.5	C4—N1—Ag1	124.6 (4)
H3A—C3—H3B	109.5	C1—N2—N3	107.1 (4)
C2—C3—H3C	109.5	C1—N2—Ag1^iii	132.0 (4)
H3A—C3—H3C	109.5	N3—N2—Ag1^iii	120.9 (3)
H3B—C3—H3C	109.5	C4—N3—N2	106.4 (4)
N3—C4—N1	111.4 (5)	C4—N3—Ag2	130.6 (4)
N3—C4—C5	124.1 (5)	N2—N3—Ag2	123.0 (3)
N1—C4—C5	124.4 (5)	O2—N4—O1	120.0 (4)
C4—C5—C6	113.1 (6)	O2—N4—O1^iv	120.0 (4)
C4—C5—H5A	109.0	O1—N4—O1^iv	120.1 (9)

Symmetry codes: (i) y+1/2, −x+1/2, z+1/4; (ii) y, x, −z; (iii) −y+1/2, x−1/2, z−1/4; (iv) −y, −x, −z+1/2.