The solution reaction of AgNO
3 and 2-aminopyrazine (apyz) in a 1:1 ratio gives rise to the title compound, [Ag
2(NO
3)
2(C
4H
5N
3)
2]
n, (I), which possesses a chiral crystal structure. In (I), both of the crystallographically independent Ag
I cations are coordinated in tetrahedral geometries by two N atoms from two apyz ligands and two O atoms from nitrate anions; however, the Ag
I centers show two different coordination environments in which one is coordinated by two O atoms from two different symmetry-related nitrate anions and the second is coordinated by two O atoms from a single nitrate anion. The crystal structure consists of one-dimensional Ag
I–apyz chains, which are further extended by μ
2-κ
2O:
O nitrate anions into a two-dimensional (4,4) sheet. N—H
O and C
apyz—H
O hydrogen bonds connect neighboring sheets to form a three-dimensional supramolecular framework.
Supporting information
CCDC reference: 763589
All reagents and solvents were used as obtained commercially without further
purification. To an aqueous solution (14 ml) of AgNO3 (170 mg, 1.0 mmol),
aminopyrazine (95 mg, 1.0 mmol) in ethanol (12 ml) was added dropwise under
continuous stirring. The resulting gray precipitate was filtered off, and the
clear filtrate was left undisturbed for two weeks. Yellow block crystals
suitable for X-ray measurements were formed, collected by filtration and dried
in air with a yield of 62% with respect to the ligand. Analysis calculated for
C8H10Ag2N8O6: C 18.13, H 1.90, N 21.14%; found: C 18.18, H. 1.81, N
21.21%. IR (KBr, cm-1): 3332 (s, br), 3142 (s,
br), 1643 (vs), 1582 (vs), 1530 (s), 1475
(sh), 1207 (m), 1038 (w), 1001 (m), 828
(m), 619 (w), 431 (w).
All H atoms were fixed geometrically and treated as riding [C—H = 0.95 Å
and N—H = 0.88 Å, with Uiso(H) = 1.2Ueq(C,N)].
Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2009).
Poly[bis(µ
2-2-aminopyrazine-
κ2N1:
N4)(µ
2-nitrato-
κ2O:
O)(nitrato-
κ2O,
O')disilver(I)]
top
Crystal data top
[Ag2(NO3)2(C4H5N3)2] | F(000) = 512 |
Mr = 529.98 | Dx = 2.504 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 3225 reflections |
a = 3.6087 (1) Å | θ = 2.6–30.7° |
b = 15.4328 (5) Å | µ = 2.84 mm−1 |
c = 12.7326 (3) Å | T = 123 K |
β = 97.566 (2)° | Block, yellow |
V = 702.93 (3) Å3 | 0.18 × 0.15 × 0.12 mm |
Z = 2 | |
Data collection top
Oxford Diffraction Gemini S Ultra diffractometer | 2573 independent reflections |
Radiation source: sealed tube | 2436 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.034 |
Detector resolution: 16.1903 pixels mm-1 | θmax = 28.0°, θmin = 2.6° |
ω scans | h = −4→4 |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008) | k = −19→20 |
Tmin = 0.629, Tmax = 0.727 | l = −16→9 |
3805 measured reflections | |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.023 | H-atom parameters constrained |
wR(F2) = 0.050 | w = 1/[σ2(Fo2) + (0.029P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.99 | (Δ/σ)max = 0.001 |
2573 reflections | Δρmax = 0.61 e Å−3 |
217 parameters | Δρmin = −0.72 e Å−3 |
1 restraint | Absolute structure: Flack (1983), 812 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.01 (3) |
Crystal data top
[Ag2(NO3)2(C4H5N3)2] | V = 702.93 (3) Å3 |
Mr = 529.98 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 3.6087 (1) Å | µ = 2.84 mm−1 |
b = 15.4328 (5) Å | T = 123 K |
c = 12.7326 (3) Å | 0.18 × 0.15 × 0.12 mm |
β = 97.566 (2)° | |
Data collection top
Oxford Diffraction Gemini S Ultra diffractometer | 2573 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008) | 2436 reflections with I > 2σ(I) |
Tmin = 0.629, Tmax = 0.727 | Rint = 0.034 |
3805 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.023 | H-atom parameters constrained |
wR(F2) = 0.050 | Δρmax = 0.61 e Å−3 |
S = 0.99 | Δρmin = −0.72 e Å−3 |
2573 reflections | Absolute structure: Flack (1983), 812 Friedel pairs |
217 parameters | Absolute structure parameter: 0.01 (3) |
1 restraint | |
Special details top
Geometry. All s.u.s (except the s.u. in the dihedral angle between two l.s. planes) are
estimated using the full covariance matrix. The cell s.u.s are taken into
account individually in the estimation of s.u. in distances, angles and
torsion angles; correlations between s.u.s in cell parameters are only used
when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell s.u.s is used for estimating s.u.s involving l.s. planes. |
Refinement. Refinement of |F|2 against ALL reflections. The weighted R-factor wR and
goodness of fit S are based on |F|2, conventional R-factors R are based on
F, with F set to zero for negative |F|2. The threshold expression of |F|2
> 2sigma(|F|2) is used only for calculating R-factors(gt) etc. and is not
relevant to the choice of reflections for refinement. R-factors based on
|F|2 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 (Å2) top | x | y | z | Uiso*/Ueq | |
Ag1 | 0.42010 (9) | 0.37067 (2) | 0.49062 (2) | 0.02087 (9) | |
Ag2 | 0.01504 (12) | 0.501571 (17) | 1.00046 (3) | 0.01569 (8) | |
C1 | 0.2950 (10) | 0.4925 (3) | 0.6729 (3) | 0.0153 (8) | |
H1A | 0.2594 | 0.5314 | 0.6146 | 0.018* | |
C2 | 0.2157 (11) | 0.5209 (3) | 0.7694 (3) | 0.0159 (9) | |
H2A | 0.1304 | 0.5785 | 0.7770 | 0.019* | |
C3 | 0.3948 (10) | 0.3882 (3) | 0.8413 (3) | 0.0128 (9) | |
H3A | 0.4349 | 0.3502 | 0.9003 | 0.015* | |
C4 | 0.4818 (9) | 0.3594 (3) | 0.7417 (3) | 0.0133 (9) | |
C5 | 0.6313 (10) | 0.4911 (3) | 0.3184 (3) | 0.0151 (8) | |
H5A | 0.6321 | 0.5309 | 0.3753 | 0.018* | |
C6 | 0.7421 (10) | 0.5198 (3) | 0.2250 (3) | 0.0150 (9) | |
H6A | 0.8115 | 0.5786 | 0.2179 | 0.018* | |
C7 | 0.6375 (9) | 0.3836 (3) | 0.1542 (3) | 0.0149 (9) | |
H7A | 0.6355 | 0.3445 | 0.0965 | 0.018* | |
C8 | 0.5167 (10) | 0.3538 (3) | 0.2498 (3) | 0.0118 (9) | |
N1 | 0.4209 (9) | 0.4123 (2) | 0.6570 (3) | 0.0137 (7) | |
N2 | 0.2587 (8) | 0.4669 (2) | 0.8544 (2) | 0.0115 (7) | |
N3 | 0.6217 (9) | 0.2797 (2) | 0.7322 (3) | 0.0160 (7) | |
H3B | 0.6744 | 0.2616 | 0.6704 | 0.019* | |
H3C | 0.6607 | 0.2455 | 0.7879 | 0.019* | |
N4 | −0.0182 (10) | 0.6935 (3) | 1.0047 (3) | 0.0161 (8) | |
N5 | −0.0232 (9) | 0.1835 (2) | 0.4993 (3) | 0.0161 (7) | |
N6 | 0.7521 (9) | 0.4637 (2) | 0.1430 (3) | 0.0128 (7) | |
N7 | 0.3984 (9) | 0.2723 (2) | 0.2570 (3) | 0.0176 (7) | |
H7B | 0.3227 | 0.2539 | 0.3160 | 0.021* | |
H7C | 0.3962 | 0.2369 | 0.2027 | 0.021* | |
N8 | 0.5220 (9) | 0.4091 (2) | 0.3325 (3) | 0.0128 (7) | |
O1 | −0.1876 (8) | 0.6512 (2) | 0.9287 (2) | 0.0212 (7) | |
O2 | 0.1627 (8) | 0.6533 (2) | 1.0806 (2) | 0.0202 (7) | |
O3 | −0.0296 (11) | 0.7741 (2) | 1.0040 (3) | 0.0200 (7) | |
O4 | −0.0391 (8) | 0.2616 (2) | 0.5307 (3) | 0.0253 (7) | |
O5 | 0.1130 (9) | 0.1669 (2) | 0.4183 (3) | 0.0259 (7) | |
O6 | −0.1440 (12) | 0.1262 (2) | 0.5528 (4) | 0.0288 (10) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ag1 | 0.03101 (16) | 0.0228 (2) | 0.01016 (13) | 0.00459 (17) | 0.00788 (10) | 0.00217 (18) |
Ag2 | 0.02284 (14) | 0.01539 (17) | 0.01002 (13) | 0.0004 (2) | 0.00649 (9) | 0.00007 (19) |
C1 | 0.0193 (18) | 0.014 (2) | 0.0127 (18) | −0.0002 (18) | 0.0019 (13) | 0.0025 (18) |
C2 | 0.0182 (18) | 0.011 (2) | 0.019 (2) | 0.0020 (15) | 0.0030 (14) | −0.0002 (16) |
C3 | 0.0138 (16) | 0.011 (3) | 0.0134 (17) | −0.0023 (15) | 0.0016 (13) | 0.0029 (16) |
C4 | 0.0087 (15) | 0.018 (3) | 0.0134 (17) | −0.0035 (17) | 0.0030 (12) | 0.0008 (19) |
C5 | 0.0163 (17) | 0.013 (2) | 0.0166 (18) | 0.0007 (17) | 0.0029 (13) | −0.0022 (18) |
C6 | 0.0143 (17) | 0.013 (2) | 0.0173 (19) | 0.0013 (15) | 0.0021 (14) | −0.0005 (16) |
C7 | 0.0149 (16) | 0.019 (3) | 0.0111 (16) | 0.0012 (18) | 0.0028 (12) | −0.0003 (19) |
C8 | 0.0109 (15) | 0.013 (3) | 0.0117 (17) | 0.0022 (14) | 0.0025 (12) | −0.0002 (16) |
N1 | 0.0170 (16) | 0.0140 (18) | 0.0110 (16) | −0.0002 (13) | 0.0047 (13) | −0.0001 (14) |
N2 | 0.0132 (15) | 0.0139 (17) | 0.0077 (15) | −0.0012 (13) | 0.0027 (12) | −0.0022 (13) |
N3 | 0.0219 (17) | 0.0136 (18) | 0.0128 (16) | 0.0017 (14) | 0.0034 (13) | 0.0003 (15) |
N4 | 0.0208 (19) | 0.0121 (18) | 0.0168 (19) | −0.0009 (16) | 0.0074 (14) | −0.0014 (18) |
N5 | 0.0151 (17) | 0.0166 (19) | 0.0165 (18) | −0.0002 (13) | 0.0016 (13) | 0.0010 (15) |
N6 | 0.0140 (15) | 0.0159 (18) | 0.0086 (16) | 0.0009 (13) | 0.0023 (12) | 0.0003 (14) |
N7 | 0.0253 (17) | 0.0153 (19) | 0.0129 (17) | −0.0020 (14) | 0.0052 (13) | −0.0001 (15) |
N8 | 0.0134 (15) | 0.0149 (17) | 0.0100 (16) | 0.0010 (13) | 0.0013 (12) | −0.0011 (14) |
O1 | 0.0275 (17) | 0.0197 (18) | 0.0148 (15) | −0.0019 (14) | −0.0029 (12) | −0.0020 (15) |
O2 | 0.0280 (17) | 0.0203 (18) | 0.0117 (14) | 0.0008 (13) | 0.0006 (12) | 0.0016 (14) |
O3 | 0.0297 (19) | 0.0073 (15) | 0.0244 (17) | 0.0017 (15) | 0.0084 (13) | 0.0018 (16) |
O4 | 0.0245 (14) | 0.0192 (18) | 0.0330 (17) | 0.0000 (13) | 0.0074 (12) | −0.0075 (16) |
O5 | 0.0316 (18) | 0.0248 (19) | 0.0241 (18) | −0.0042 (14) | 0.0138 (14) | −0.0045 (15) |
O6 | 0.028 (2) | 0.029 (2) | 0.031 (2) | −0.0020 (13) | 0.0081 (17) | 0.0152 (15) |
Geometric parameters (Å, º) top
Ag1—N1 | 2.214 (3) | C5—H5A | 0.9500 |
Ag1—N8 | 2.176 (3) | C6—N6 | 1.360 (5) |
Ag1—O4 | 2.463 (3) | C6—H6A | 0.9500 |
Ag1—O4i | 2.577 (3) | C7—N6 | 1.317 (6) |
Ag2—N2 | 2.224 (3) | C7—C8 | 1.422 (5) |
Ag2—N6ii | 2.234 (3) | C7—H7A | 0.9500 |
Ag2—O1 | 2.555 (3) | C8—N7 | 1.336 (6) |
Ag2—O2 | 2.581 (3) | C8—N8 | 1.353 (5) |
C1—N1 | 1.343 (6) | N3—H3B | 0.8800 |
C1—C2 | 1.370 (6) | N3—H3C | 0.8800 |
C1—H1A | 0.9500 | N4—O3 | 1.245 (5) |
C2—N2 | 1.358 (5) | N4—O1 | 1.256 (5) |
C2—H2A | 0.9500 | N4—O2 | 1.257 (5) |
C3—N2 | 1.329 (5) | N5—O5 | 1.227 (4) |
C3—C4 | 1.417 (5) | N5—O6 | 1.231 (5) |
C3—H3A | 0.9500 | N5—O4 | 1.273 (5) |
C4—N3 | 1.341 (6) | N6—Ag2iii | 2.234 (3) |
C4—N1 | 1.347 (5) | N7—H7B | 0.8800 |
C5—N8 | 1.345 (6) | N7—H7C | 0.8800 |
C5—C6 | 1.376 (6) | O4—Ag1iv | 2.577 (3) |
| | | |
N1—Ag1—N8 | 145.84 (14) | N7—C8—N8 | 120.8 (4) |
N1—Ag1—O4 | 85.20 (12) | N7—C8—C7 | 120.0 (4) |
N1—Ag1—O4i | 95.44 (11) | N8—C8—C7 | 119.2 (4) |
N8—Ag1—O4 | 125.32 (12) | C1—N1—C4 | 117.4 (4) |
N8—Ag1—O4i | 98.35 (12) | C1—N1—Ag1 | 117.0 (3) |
N2—Ag2—N6ii | 150.84 (14) | C4—N1—Ag1 | 124.7 (3) |
N2—Ag2—O1 | 92.56 (12) | C3—N2—C2 | 117.7 (3) |
N2—Ag2—O2 | 117.70 (12) | C3—N2—Ag2 | 121.2 (3) |
N6ii—Ag2—O1 | 113.25 (12) | C2—N2—Ag2 | 120.1 (3) |
N6ii—Ag2—O2 | 90.22 (12) | C4—N3—H3B | 120.0 |
O1—Ag2—O2 | 49.89 (9) | C4—N3—H3C | 120.0 |
O4—Ag1—O4i | 91.43 (12) | H3B—N3—H3C | 120.0 |
N1—C1—C2 | 123.0 (4) | O3—N4—O1 | 120.1 (4) |
N1—C1—H1A | 118.5 | O3—N4—O2 | 120.8 (4) |
C2—C1—H1A | 118.5 | O1—N4—O2 | 119.1 (4) |
N2—C2—C1 | 120.2 (4) | O5—N5—O6 | 121.7 (4) |
N2—C2—H2A | 119.9 | O5—N5—O4 | 120.0 (4) |
C1—C2—H2A | 119.9 | O6—N5—O4 | 118.2 (4) |
N2—C3—C4 | 121.9 (4) | C7—N6—C6 | 118.3 (3) |
N2—C3—H3A | 119.1 | N5—O4—Ag1iv | 128.4 (2) |
C4—C3—H3A | 119.1 | C7—N6—Ag2iii | 120.4 (3) |
N3—C4—N1 | 120.5 (4) | C6—N6—Ag2iii | 121.0 (3) |
N3—C4—C3 | 119.9 (4) | C8—N7—H7B | 120.0 |
N1—C4—C3 | 119.6 (4) | C8—N7—H7C | 120.0 |
N8—C5—C6 | 122.8 (4) | H7B—N7—H7C | 120.0 |
N8—C5—H5A | 118.6 | C5—N8—C8 | 117.7 (4) |
C6—C5—H5A | 118.6 | C5—N8—Ag1 | 117.9 (3) |
N6—C6—C5 | 119.9 (4) | C8—N8—Ag1 | 124.2 (3) |
N6—C6—H6A | 120.0 | N4—O1—Ag2 | 96.1 (2) |
C5—C6—H6A | 120.0 | N4—O2—Ag2 | 94.9 (2) |
N6—C7—C8 | 122.1 (4) | N5—O4—Ag1 | 121.5 (2) |
N6—C7—H7A | 118.9 | Ag1—O4—Ag1iv | 91.43 (12) |
C8—C7—H7A | 118.9 | | |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z+1; (iii) x+1, y, z−1; (iv) x−1, y, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7B···O5 | 0.88 | 2.08 | 2.912 (5) | 157 |
N3—H3B···O4i | 0.88 | 2.17 | 2.998 (5) | 156 |
N3—H3C···O2v | 0.88 | 2.23 | 3.099 (5) | 172 |
N7—H7C···O1vi | 0.88 | 2.19 | 3.031 (5) | 161 |
C1—H1A···O5vii | 0.95 | 2.49 | 3.211 (5) | 133 |
C1—H1A···O6vii | 0.95 | 2.57 | 3.521 (6) | 175 |
C5—H5A···O6viii | 0.95 | 2.44 | 3.108 (6) | 127 |
C5—H5A···O6vii | 0.95 | 2.55 | 3.299 (6) | 136 |
C3—H3A···O3ix | 0.95 | 2.34 | 3.066 (5) | 133 |
C6—H6A···O2iii | 0.95 | 2.56 | 3.266 (5) | 131 |
C7—H7A···O3x | 0.95 | 2.31 | 3.109 (5) | 142 |
Symmetry codes: (i) x+1, y, z; (iii) x+1, y, z−1; (v) −x+1, y−1/2, −z+2; (vi) −x, y−1/2, −z+1; (vii) −x, y+1/2, −z+1; (viii) −x+1, y+1/2, −z+1; (ix) −x, y−1/2, −z+2; (x) −x+1, y−1/2, −z+1. |
Experimental details
Crystal data |
Chemical formula | [Ag2(NO3)2(C4H5N3)2] |
Mr | 529.98 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 123 |
a, b, c (Å) | 3.6087 (1), 15.4328 (5), 12.7326 (3) |
β (°) | 97.566 (2) |
V (Å3) | 702.93 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 2.84 |
Crystal size (mm) | 0.18 × 0.15 × 0.12 |
|
Data collection |
Diffractometer | Oxford Diffraction Gemini S Ultra diffractometer |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2008) |
Tmin, Tmax | 0.629, 0.727 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3805, 2573, 2436 |
Rint | 0.034 |
(sin θ/λ)max (Å−1) | 0.661 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.023, 0.050, 0.99 |
No. of reflections | 2573 |
No. of parameters | 217 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.61, −0.72 |
Absolute structure | Flack (1983), 812 Friedel pairs |
Absolute structure parameter | 0.01 (3) |
Selected geometric parameters (Å, º) topAg1—N1 | 2.214 (3) | Ag2—N2 | 2.224 (3) |
Ag1—N8 | 2.176 (3) | Ag2—N6ii | 2.234 (3) |
Ag1—O4 | 2.463 (3) | Ag2—O1 | 2.555 (3) |
Ag1—O4i | 2.577 (3) | Ag2—O2 | 2.581 (3) |
| | | |
N1—Ag1—N8 | 145.84 (14) | N2—Ag2—O2 | 117.70 (12) |
N1—Ag1—O4 | 85.20 (12) | N6ii—Ag2—O1 | 113.25 (12) |
N1—Ag1—O4i | 95.44 (11) | N6ii—Ag2—O2 | 90.22 (12) |
N8—Ag1—O4 | 125.32 (12) | O1—Ag2—O2 | 49.89 (9) |
N8—Ag1—O4i | 98.35 (12) | O4—Ag1—O4i | 91.43 (12) |
N2—Ag2—N6ii | 150.84 (14) | N5—O4—Ag1iii | 128.4 (2) |
N2—Ag2—O1 | 92.56 (12) | C7—N6—Ag2iv | 120.4 (3) |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z+1; (iii) x−1, y, z; (iv) x+1, y, z−1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7B···O5 | 0.88 | 2.08 | 2.912 (5) | 157.2 |
N3—H3B···O4i | 0.88 | 2.17 | 2.998 (5) | 156.3 |
N3—H3C···O2v | 0.88 | 2.23 | 3.099 (5) | 171.5 |
N7—H7C···O1vi | 0.88 | 2.19 | 3.031 (5) | 160.5 |
C1—H1A···O5vii | 0.95 | 2.49 | 3.211 (5) | 133 |
C1—H1A···O6vii | 0.95 | 2.57 | 3.521 (6) | 175.4 |
C5—H5A···O6viii | 0.95 | 2.44 | 3.108 (6) | 127 |
C5—H5A···O6vii | 0.95 | 2.55 | 3.299 (6) | 135.5 |
C3—H3A···O3ix | 0.95 | 2.34 | 3.066 (5) | 133.0 |
C6—H6A···O2iv | 0.95 | 2.56 | 3.266 (5) | 131.0 |
C7—H7A···O3x | 0.95 | 2.31 | 3.109 (5) | 141.8 |
Symmetry codes: (i) x+1, y, z; (iv) x+1, y, z−1; (v) −x+1, y−1/2, −z+2; (vi) −x, y−1/2, −z+1; (vii) −x, y+1/2, −z+1; (viii) −x+1, y+1/2, −z+1; (ix) −x, y−1/2, −z+2; (x) −x+1, y−1/2, −z+1. |
Interest in crystal engineering and supramolecular chemistry is rapidly increasing becuase of the diverse and aesthetic structural topologies of the products of such studies and their potential use in optical, electrical, catalytic and gas storage applications and even in drug delivery as functional solid materials (Blake, Brooks et al., 1999; Blake, Champness et al., 1999; Blake et al., 1997; Evans & Lin, 2002; Kitagawa et al., 2004; Yaghi et al., 2003; Applegarth et al., 2005). Particularly, there is considerable interest in chiral solid-state materials, owing to their potential application in asymmetric catalysis and chiral separation (Kesanli & Lin, 2003; Pidcock, 2005). Although these chiral materials can be synthesized from single chiral organic spacers with metal ions (Dai et al., 2005; Wang et al., 2008; Zaworotko, 2001), compounds presenting chiral crystal structures self-assembled from the AgI cation and achiral 2-aminopyrazine (apyz) ligand have not been documented yet. Recently, we have undertaken a series of investigations into the self-assembly of the AgI cation with different angular and linear bipodal N-donor ligands, such as aminopyrimidine and aminopyrazine (Luo, Huang, Chen et al., 2008; Luo, Huang, Zhang et al., 2008; Luo, Sun, Xu et al., 2009; Luo, Sun, Zhang, Huang & Zheng, 2009; Luo, Sun, Zhang, Xu et al., 2009; Sun, Luo, Huang et al., 2009; Sun, Luo, Xu et al., 2009; Sun, Luo, Zhang et al., 2009), with the principal aim of obtaining supramolecular compounds or multifunctional coordination polymers. In an attempt to exploit the influence of anions on the AgI–apyz system, we surprisingly obtained the achiral coordination polymer (I), stacking to give a chiral crystal structure.
The asymmetric unit of (I) contains two different AgI cations, two apyz ligands and two nitrate anions. The coordination geometry of the AgI cation is tetrahedral, and each AgI cation is coordinated by two N atoms from two different apyz ligands and two O atoms from nitrate anions (Fig. 1). The geometric parameters, especially the bond angles around atoms Ag1 and Ag2, are obviously different. The bond angles around Ag1 and Ag2 open up from the ideal tetrahedral angle to 145.84 (14) and 150.84 (14)°, respectively,, while the remaining angles around atoms Ag1 and Ag2 are in the ranges 85.20 (12)–125.32 (12)° and 49.89 (9)–113.25 (12)°, respectively. The Ag—N and Ag—O bond lengths (Table 1) are comparable to those in related compounds (Fan et al., 2007; Oxtoby et al., 2002; Turner et al., 2005; Massoud & Langer, 2009; Massoud et al., 2009; Withersby et al., 1997; Zartilas et al., 2007). There are also weak Ag···C interactions with Ag···C distances in the range 3.314 (4)–3.322 (4) Å, which fall in the secondary bonding range (the sum of the van der Waals radii of Ag and C is 3.42 Å; Mascal et al., 2000). Some polymeric silver(I) compounds of aromatic ligands have been reported to present similar Ag···C interactions, with Ag···C bond distances of ca 2.80–3.38 Å (Blake et al., 2000; Khlobystov et al., 2001). Therefore, these interactions in (I) are very important, in the present case, for the packing of (I) in the solid state. Between neighboring chains, the shortest Ag···Ag separation is 3.6087 (6) Å, which is longer than twice the van der Waals radius of AgI (1.72 Å; Bondi, 1964), indicating no direct metal–metal interaction.
The apyz ligand acts in a µ2-N,N'-bidentate fashion to link AgI cations to form a one-dimensional chain in which atoms Ag1 and Ag2 alternate. The nitrate anions show two different coordination modes, namely µ2-κ2O:O and κ2O:O', which are found in many other silver(I) compounds (Cui & He, 2003; Faure et al., 1985; Chen et al., 2004). The µ2-κ2O:O-nitrate anions play an important role in constructing the two-dimensional undulating sheet (Fig. 2) in which µ2-κ2O:O-nitrate anions bridge the neighboring chains. Fig. 3 shows a schematic depiction of the sheet, which has a (4,4) topology (Batten & Robson, 1998), with AgI cations as the four-connected nodes and with meshes of dimensions 3.61 × 7.13 Å. In addition, amino groups from apyz ligands act as hydrogen-bond donors with N···O distances in the range 2.912 (5)–3.099 (5)Å (Table 2) to form intra-sheet N—H···O hydrogen bonds. apyz–nitrate C—H···O hydrogen bonds with C···O distances in the range 3.066 (5)–3.521 (5)Å not only support the N—H···O hydrogen bonds within the sheets but also link the sheets to form a three-dimensional network (Fig. 4).