Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113006768/sf3194sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270113006768/sf3194Isup2.hkl |
CCDC reference: 950346
For related literature, see: Allendorf et al. (2009); Fan et al. (2012); Fang & Zhang (2006); Gao et al. (2011); Gu et al. (2011); Jing et al. (2010); Li et al. (2011); Li, Guo, Wang & Wang (2009); Li, Luo, Gao, Lu & Li (2012); Li, Wu, Niu, Niu & Zhang (2009); Li, Zheng, Yuan, Ablet & Jin (2012); Lu et al. (2012); Song et al. (2010); Sun et al. (2010); Wang et al. (2008, 2010, 2011); Yuan et al. (2012); Zeng et al. (2011); Zhang et al. (2006, 2008, 2011); Zhao et al. (2007).
A mixture of AgNO3 (24.0 mg, 0.2 mmol), H3PyIDC (46.6 mg, 0.2 mmol) and H2O (8 ml) was placed in a 25 ml Teflon reactor and heated at 443 K for 96 h under autogenous pressure. After cooling to room temperature, yellow block-shaped crystals of (I) were obtained in a yield of 35% based on Ag. Elemental analysis, calculated for C10H5Ag2N3O4: C 26.88, H 1.13, N 9.40%; found: C 26.93, H 1.09, N 9.46%. FT–IR (KBr pellet, ν, cm-1): 3425 (s), 2974 (w), 1635 (m), 1600 (w), 1568 (w), 1524 (s), 1490 (w), 1468 (w), 1402 (s), 1345 (w), 1260 (w), 1244 (w), 1187 (w), 1108 (m), 1047 (w), 980 (w), 852 (m), 814 (m), 782 (w), 735 (w), 638 (w), 546 (w).
H atoms bonded to C atoms were placed in calculated positions, with C—H = 0.93 Å, and refined as riding atoms, with Uiso(H) = 1.2Ueq(C). The carboxy H atom was located in the idealized position, with O—H = 0.82 Å, and refined as a riding atom, with Uiso(H) = 1.5Ueq(O).
Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 (Bruker, 2004); data reduction: APEX2 (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
[Ag2(C10H5N3O4)] | F(000) = 848 |
Mr = 446.91 | Dx = 2.734 Mg m−3 |
Monoclinic, Cc | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: C -2yc | Cell parameters from 2374 reflections |
a = 5.2180 (13) Å | θ = 2.8–27.9° |
b = 20.188 (5) Å | µ = 3.62 mm−1 |
c = 10.503 (3) Å | T = 298 K |
β = 101.139 (3)° | Block, yellow |
V = 1085.6 (5) Å3 | 0.28 × 0.25 × 0.22 mm |
Z = 4 |
Bruker APEXII CCD area-detector diffractometer | 1856 independent reflections |
Radiation source: fine-focus sealed tube | 1780 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.034 |
ϕ and ω scans | θmax = 26.0°, θmin = 2.0° |
Absorption correction: multi-scan (APEX2; Bruker, 2004) | h = −5→6 |
Tmin = 0.431, Tmax = 0.503 | k = −19→24 |
2835 measured reflections | l = −12→12 |
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)] = 0.038 | H-atom parameters constrained |
wR(F2) = 0.097 | w = 1/[σ2(Fo2) + (0.0421P)2 + 4.9899P] where P = (Fo2 + 2Fc2)/3 |
S = 1.11 | (Δ/σ)max = 0.001 |
1856 reflections | Δρmax = 0.64 e Å−3 |
173 parameters | Δρmin = −1.11 e Å−3 |
2 restraints | Absolute structure: Flack (1983), 786 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.26 (7) |
[Ag2(C10H5N3O4)] | V = 1085.6 (5) Å3 |
Mr = 446.91 | Z = 4 |
Monoclinic, Cc | Mo Kα radiation |
a = 5.2180 (13) Å | µ = 3.62 mm−1 |
b = 20.188 (5) Å | T = 298 K |
c = 10.503 (3) Å | 0.28 × 0.25 × 0.22 mm |
β = 101.139 (3)° |
Bruker APEXII CCD area-detector diffractometer | 1856 independent reflections |
Absorption correction: multi-scan (APEX2; Bruker, 2004) | 1780 reflections with I > 2σ(I) |
Tmin = 0.431, Tmax = 0.503 | Rint = 0.034 |
2835 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | H-atom parameters constrained |
wR(F2) = 0.097 | Δρmax = 0.64 e Å−3 |
S = 1.11 | Δρmin = −1.11 e Å−3 |
1856 reflections | Absolute structure: Flack (1983), 786 Friedel pairs |
173 parameters | Absolute structure parameter: 0.26 (7) |
2 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
Ag2 | 0.42402 (8) | 0.58992 (2) | 0.24408 (5) | 0.03294 (11) | |
Ag1 | 1.30921 (5) | 0.77225 (2) | 0.59249 (4) | 0.03079 (11) | |
O4 | 0.1812 (8) | 0.69932 (19) | 0.2062 (4) | 0.0263 (10) | |
C1 | 0.8059 (12) | 0.8409 (3) | 0.4286 (6) | 0.0250 (14) | |
C2 | 0.7763 (10) | 0.7680 (2) | 0.4103 (5) | 0.0155 (12) | |
C5 | 0.8799 (10) | 0.6657 (2) | 0.4466 (5) | 0.0172 (12) | |
N2 | 0.6480 (8) | 0.6642 (2) | 0.3631 (4) | 0.0179 (10) | |
N1 | 0.9629 (9) | 0.7273 (2) | 0.4773 (4) | 0.0187 (11) | |
C3 | 0.5790 (11) | 0.7291 (2) | 0.3406 (5) | 0.0206 (13) | |
C9 | 1.2615 (12) | 0.6092 (3) | 0.5837 (7) | 0.0352 (17) | |
H9 | 1.3574 | 0.6482 | 0.5884 | 0.042* | |
C6 | 1.0114 (10) | 0.6054 (2) | 0.5081 (5) | 0.0179 (12) | |
O3 | 0.2580 (8) | 0.8066 (2) | 0.2463 (4) | 0.0297 (11) | |
C4 | 0.3248 (11) | 0.7469 (3) | 0.2582 (6) | 0.0221 (13) | |
N3 | 1.2451 (10) | 0.4951 (2) | 0.6445 (5) | 0.0322 (14) | |
C8 | 1.0093 (13) | 0.4920 (3) | 0.5679 (6) | 0.0341 (17) | |
H8 | 0.9218 | 0.4516 | 0.5602 | 0.041* | |
C10 | 1.3637 (13) | 0.5534 (4) | 0.6515 (7) | 0.0398 (19) | |
H10 | 1.5266 | 0.5570 | 0.7057 | 0.048* | |
C7 | 0.8893 (13) | 0.5451 (3) | 0.4997 (6) | 0.0338 (16) | |
H7 | 0.7246 | 0.5402 | 0.4478 | 0.041* | |
O2 | 0.6059 (9) | 0.8779 (2) | 0.3724 (5) | 0.0389 (13) | |
H2 | 0.4798 | 0.8540 | 0.3456 | 0.058* | |
O1 | 0.9996 (9) | 0.8660 (2) | 0.4926 (5) | 0.0342 (12) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ag2 | 0.0348 (2) | 0.01957 (18) | 0.0365 (2) | −0.00696 (19) | −0.01300 (18) | −0.00411 (19) |
Ag1 | 0.01864 (18) | 0.0351 (2) | 0.0321 (2) | −0.00503 (19) | −0.01132 (16) | −0.0035 (2) |
O4 | 0.0182 (18) | 0.0218 (18) | 0.033 (2) | 0.0066 (16) | −0.0092 (17) | 0.0027 (17) |
C1 | 0.021 (3) | 0.025 (3) | 0.026 (3) | 0.000 (2) | −0.002 (2) | −0.003 (2) |
C2 | 0.020 (2) | 0.006 (2) | 0.019 (2) | 0.0022 (18) | 0.000 (2) | 0.0031 (18) |
C5 | 0.027 (3) | 0.007 (2) | 0.016 (2) | −0.004 (2) | 0.000 (2) | 0.0002 (18) |
N2 | 0.016 (2) | 0.0145 (19) | 0.019 (2) | 0.0030 (17) | −0.0074 (17) | −0.0015 (17) |
N1 | 0.018 (2) | 0.017 (2) | 0.019 (2) | 0.0006 (17) | 0.0003 (18) | −0.0026 (17) |
C3 | 0.019 (3) | 0.016 (2) | 0.024 (3) | 0.001 (2) | −0.001 (2) | 0.002 (2) |
C9 | 0.026 (3) | 0.019 (3) | 0.052 (4) | 0.002 (2) | −0.013 (3) | 0.009 (3) |
C6 | 0.018 (3) | 0.013 (2) | 0.019 (2) | 0.004 (2) | −0.004 (2) | −0.004 (2) |
O3 | 0.022 (2) | 0.023 (2) | 0.037 (2) | 0.0074 (17) | −0.0118 (18) | 0.0009 (17) |
C4 | 0.015 (3) | 0.025 (3) | 0.021 (2) | 0.002 (2) | −0.009 (2) | 0.006 (2) |
N3 | 0.030 (3) | 0.017 (2) | 0.042 (3) | 0.006 (2) | −0.013 (2) | 0.003 (2) |
C8 | 0.035 (3) | 0.022 (3) | 0.041 (3) | −0.003 (3) | −0.003 (3) | −0.002 (3) |
C10 | 0.023 (3) | 0.039 (4) | 0.047 (4) | 0.004 (3) | −0.018 (3) | 0.000 (3) |
C7 | 0.031 (3) | 0.026 (3) | 0.035 (3) | 0.003 (3) | −0.017 (3) | 0.000 (3) |
O2 | 0.031 (2) | 0.022 (2) | 0.054 (3) | 0.0051 (18) | −0.017 (2) | −0.006 (2) |
O1 | 0.033 (2) | 0.022 (2) | 0.043 (2) | −0.0031 (18) | −0.004 (2) | 0.0012 (19) |
Ag2—N3i | 2.130 (5) | N2—C3 | 1.367 (7) |
Ag2—N2 | 2.148 (4) | C3—C4 | 1.481 (7) |
Ag2—O4 | 2.539 (4) | C9—C10 | 1.384 (9) |
Ag1—O4ii | 2.151 (4) | C9—C6 | 1.392 (8) |
Ag1—N1 | 2.169 (4) | C9—H9 | 0.9300 |
Ag1—O1 | 2.577 (4) | C6—C7 | 1.368 (8) |
O4—C4 | 1.275 (7) | O3—C4 | 1.254 (7) |
O4—Ag1iii | 2.151 (4) | N3—C10 | 1.324 (9) |
C1—O1 | 1.212 (7) | N3—C8 | 1.336 (8) |
C1—O2 | 1.326 (7) | N3—Ag2iv | 2.130 (5) |
C1—C2 | 1.487 (7) | C8—C7 | 1.372 (9) |
C2—N1 | 1.362 (7) | C8—H8 | 0.9300 |
C2—C3 | 1.387 (7) | C10—H10 | 0.9300 |
C5—N1 | 1.337 (6) | C7—H7 | 0.9300 |
C5—N2 | 1.351 (6) | O2—H2 | 0.8200 |
C5—C6 | 1.482 (7) | ||
N3i—Ag2—N2 | 170.49 (18) | N2—C3—C4 | 120.7 (5) |
N3i—Ag2—O4 | 117.78 (17) | C2—C3—C4 | 131.3 (5) |
N2—Ag2—O4 | 71.52 (14) | C10—C9—C6 | 118.3 (6) |
O4ii—Ag1—N1 | 170.45 (16) | C10—C9—H9 | 120.9 |
O4ii—Ag1—O1 | 117.22 (14) | C6—C9—H9 | 120.9 |
N1—Ag1—O1 | 71.99 (15) | C7—C6—C9 | 117.4 (5) |
C4—O4—Ag1iii | 115.4 (3) | C7—C6—C5 | 122.1 (5) |
C4—O4—Ag2 | 110.7 (3) | C9—C6—C5 | 120.5 (5) |
Ag1iii—O4—Ag2 | 133.52 (18) | O3—C4—O4 | 123.5 (5) |
O1—C1—O2 | 120.7 (5) | O3—C4—C3 | 119.5 (5) |
O1—C1—C2 | 122.8 (5) | O4—C4—C3 | 116.9 (5) |
O2—C1—C2 | 116.5 (5) | C10—N3—C8 | 116.3 (5) |
N1—C2—C3 | 108.3 (4) | C10—N3—Ag2iv | 122.2 (4) |
N1—C2—C1 | 118.9 (5) | C8—N3—Ag2iv | 121.5 (4) |
C3—C2—C1 | 132.6 (5) | N3—C8—C7 | 123.5 (6) |
N1—C5—N2 | 112.6 (4) | N3—C8—H8 | 118.3 |
N1—C5—C6 | 123.9 (4) | C7—C8—H8 | 118.3 |
N2—C5—C6 | 123.1 (4) | N3—C10—C9 | 124.4 (6) |
C5—N2—C3 | 105.3 (4) | N3—C10—H10 | 117.8 |
C5—N2—Ag2 | 135.4 (3) | C9—C10—H10 | 117.8 |
C3—N2—Ag2 | 118.2 (3) | C6—C7—C8 | 120.1 (6) |
C5—N1—C2 | 105.7 (4) | C6—C7—H7 | 119.9 |
C5—N1—Ag1 | 136.0 (4) | C8—C7—H7 | 119.9 |
C2—N1—Ag1 | 118.1 (3) | C1—O2—H2 | 109.5 |
N2—C3—C2 | 108.0 (4) | C1—O1—Ag1 | 107.9 (4) |
N3i—Ag2—O4—C4 | −171.7 (4) | C1—C2—C3—N2 | −176.9 (6) |
N2—Ag2—O4—C4 | 10.5 (4) | N1—C2—C3—C4 | 176.0 (6) |
N3i—Ag2—O4—Ag1iii | 1.5 (4) | C1—C2—C3—C4 | 0.3 (11) |
N2—Ag2—O4—Ag1iii | −176.3 (3) | C10—C9—C6—C7 | −4.0 (10) |
O1—C1—C2—N1 | 6.2 (9) | C10—C9—C6—C5 | 172.4 (6) |
O2—C1—C2—N1 | −172.8 (5) | N1—C5—C6—C7 | 162.9 (6) |
O1—C1—C2—C3 | −178.5 (6) | N2—C5—C6—C7 | −9.9 (9) |
O2—C1—C2—C3 | 2.5 (10) | N1—C5—C6—C9 | −13.3 (9) |
N1—C5—N2—C3 | −0.5 (6) | N2—C5—C6—C9 | 173.9 (6) |
C6—C5—N2—C3 | 173.0 (5) | Ag1iii—O4—C4—O3 | 0.5 (8) |
N1—C5—N2—Ag2 | 166.8 (4) | Ag2—O4—C4—O3 | 175.0 (5) |
C6—C5—N2—Ag2 | −19.6 (8) | Ag1iii—O4—C4—C3 | 178.1 (4) |
O4—Ag2—N2—C5 | −178.1 (6) | Ag2—O4—C4—C3 | −7.3 (6) |
O4—Ag2—N2—C3 | −12.0 (4) | N2—C3—C4—O3 | 175.0 (5) |
N2—C5—N1—C2 | −0.2 (6) | C2—C3—C4—O3 | −1.9 (10) |
C6—C5—N1—C2 | −173.7 (5) | N2—C3—C4—O4 | −2.7 (9) |
N2—C5—N1—Ag1 | −176.4 (4) | C2—C3—C4—O4 | −179.6 (6) |
C6—C5—N1—Ag1 | 10.0 (9) | C10—N3—C8—C7 | −0.6 (11) |
C3—C2—N1—C5 | 0.9 (6) | Ag2iv—N3—C8—C7 | −178.5 (5) |
C1—C2—N1—C5 | 177.2 (5) | C8—N3—C10—C9 | −1.3 (11) |
C3—C2—N1—Ag1 | 177.9 (4) | Ag2iv—N3—C10—C9 | 176.6 (6) |
C1—C2—N1—Ag1 | −5.7 (7) | C6—C9—C10—N3 | 3.6 (12) |
O1—Ag1—N1—C5 | 178.9 (6) | C9—C6—C7—C8 | 2.3 (10) |
O1—Ag1—N1—C2 | 2.9 (4) | C5—C6—C7—C8 | −174.0 (6) |
C5—N2—C3—C2 | 1.1 (6) | N3—C8—C7—C6 | 0.1 (11) |
Ag2—N2—C3—C2 | −168.9 (4) | O2—C1—O1—Ag1 | 175.8 (5) |
C5—N2—C3—C4 | −176.5 (5) | C2—C1—O1—Ag1 | −3.2 (7) |
Ag2—N2—C3—C4 | 13.6 (7) | O4ii—Ag1—O1—C1 | 177.5 (4) |
N1—C2—C3—N2 | −1.2 (7) | N1—Ag1—O1—C1 | 0.2 (4) |
Symmetry codes: (i) x−1, −y+1, z−1/2; (ii) x+3/2, −y+3/2, z+1/2; (iii) x−3/2, −y+3/2, z−1/2; (iv) x+1, −y+1, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | [Ag2(C10H5N3O4)] |
Mr | 446.91 |
Crystal system, space group | Monoclinic, Cc |
Temperature (K) | 298 |
a, b, c (Å) | 5.2180 (13), 20.188 (5), 10.503 (3) |
β (°) | 101.139 (3) |
V (Å3) | 1085.6 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 3.62 |
Crystal size (mm) | 0.28 × 0.25 × 0.22 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (APEX2; Bruker, 2004) |
Tmin, Tmax | 0.431, 0.503 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2835, 1856, 1780 |
Rint | 0.034 |
(sin θ/λ)max (Å−1) | 0.616 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.097, 1.11 |
No. of reflections | 1856 |
No. of parameters | 173 |
No. of restraints | 2 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.64, −1.11 |
Absolute structure | Flack (1983), 786 Friedel pairs |
Absolute structure parameter | 0.26 (7) |
Computer programs: APEX2 (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEPIII (Burnett & Johnson, 1996) and PLATON (Spek, 2009).
Ag2—N3i | 2.130 (5) | Ag1—O4ii | 2.151 (4) |
Ag2—N2 | 2.148 (4) | Ag1—N1 | 2.169 (4) |
Ag2—O4 | 2.539 (4) | Ag1—O1 | 2.577 (4) |
N3i—Ag2—N2 | 170.49 (18) | O4ii—Ag1—N1 | 170.45 (16) |
N3i—Ag2—O4 | 117.78 (17) | O4ii—Ag1—O1 | 117.22 (14) |
N2—Ag2—O4 | 71.52 (14) | N1—Ag1—O1 | 71.99 (15) |
Symmetry codes: (i) x−1, −y+1, z−1/2; (ii) x+3/2, −y+3/2, z+1/2. |
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Recently, 1H-imidazole-4,5-dicarboxylic acid (H3IDC), an N-heterocyclic carboxylic acid ligand, has attracted significant attention in the construction of interesting metal–organic frameworks (MOFs) due to its versatile coordination modes under hydro(solvo)thermal conditions (Fang & Zhang, 2006; Li, Zheng et al., 2012; Lu et al., 2012; Wang et al., 2010; Zhang et al., 2006; Zhao et al., 2007). Most recently, a series of functionalized H3IDC ligands have been prepared by introducing diverse substituent groups, such as methyl (Gao et al., 2011; Li, Luo et al., 2012; Song et al., 2010), ethyl (Gu et al., 2011; Li, Guo et al., 2009; Wang et al., 2008; Zhang et al., 2011) and propyl (Fan et al., 2012; Li et al., 2011; Wang et al., 2011; Zeng et al., 2011) groups, on the 2-position of the imidazole ring. Many novel MOFs with intriguing structural topologies and useful properties based on these ligands have been successfully synthesized, and it has been discovered that the different substituent groups may have different spatial effects on neighbouring carboxylate groups, which give rise to their various coordination modes.
Compared with the well studied H3IDC ligand and its 2-position aliphatic hydrocarbon-substituted derivatives, the ligand 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid (H3PyIDC), an imidazole-4,5-dicarboxylate ligand bearing an aromatic pyridinyl group on the 2-position, remains largely unexplored (Jing et al., 2010; Li, Wu et al., 2009; Yuan et al., 2012). H3PyIDC contains the H3IDC building block and can be successively deprotonated to produce the H2PyIDC-, HPyIDC2- and PyIDC3- species under certain conditions. The additional pyridinyl group in the backbone of H3PyIDC can rotate freely about the C—C bond to meet the different coordination requirements of metal atoms, thus increasing the dimensionality of the final structures.
On the basis of the aforementioned points, we consider H3PyIDC to be an ideal multidentate organic ligand for constructing new three-dimensional MOFs. As expected, the title three-dimensional silver(I) coordination framework, poly[[µ4-5-carboxy-4-carboxylato-2-(pyridin-4-yl)-1H-imidazol-1-ido]disilver(I)], [Ag2(HPyIDC)]n, (I), was successfully synthesized by reacting silver nitrate with H3PyIDC under hydrothermal conditions. The as-synthesized sample was characterized by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy. The thermal stability and photoluminescent properties of (I) have also been investigated.
Compound (I) crystallizes in the noncentrosymmetric monoclinic space group Cc, and the asymmetric unit comprises two crystallographically independent AgI cations and one unique HPyIDC2- anion. As shown in Fig. 1, atoms Ag1 and Ag2 are both three-coordinated in distorted T-shaped coordination geometries. Atom Ag1 is coordinated by one imidazole N and two carboxylate O atoms from two different HPyIDC2- anions, while atom Ag2 is bonded to one carboxylate O atom and two imidazole N atoms from two individual HPyIDC2- anions. The Ag—N bond lengths are in the range 2.130 (5)–2.169 (4) Å and the Ag—O bond distances vary from 2.151 (4) to 2.577 (4) Å, all of which are comparable with those reported for other imidazole-based dicarboxyate AgI coordination polymers (Fang & Zhang, 2006; Zhao et al., 2007). In each HPyIDC2- ligand, the dihedral angles between the planes of the carboxy and carboxylate groups and the imidazole ring are 5.7 (4) and 5.9 (5)°, respectively, while the planes of the imidazole and pyridine rings form a dihedral angle of 15.19 (21)°. Interestingly, the doubly deprotonated HPyIDC2- anion adopts an unusual µ4-κ2N1,O5:κN2:κ2N3,O4:κ2O4 coordination mode, bridging four AgI cations in bis-N,O-chelating, O-bridging and monodentate fashions. The uncoordinated carboxy/carboxylate atoms O2 and O3 form an intramolecular hydrogen bond (Table 2).
In (I), the HPyIDC2- ligand links atoms Ag1 and Ag2 via a bis-N,O-chelating mode into a dinuclear [Ag2(HPyIDC)] unit with an Ag···Ag separation of 6.4609 (11) Å. These units are further connected by Ag—O coordination bonds (Ag1—O4ii; Table 1) to produce an infinite one-dimensional chain (Fig. 2a). In the chain, the shortest Ag···Ag distance is 4.3125 (9) Å. These one-dimensional chains are bridged by the pyridine N atom of the HPyIDC2- ligand in different orientations, giving rise to the formation of a three-dimensional framework (Fig. 3). It is worth noting that the Ag2···O1iii distance (Fig. 2b) between two neighbouring one-dimensional chains is 2.886 (5) Å, which is shorter than the sum of the corresponding van der Waals radii (3.1 Å; Standard reference?), indicative of a weak interaction between atoms Ag2 and O1 (Zhao et al., 2007). To better understand the structure of (I), topology analysis is employed to describe the architecture. Both atoms Ag1 and Ag2 are bound to two µ4-HPyIDC2- ligands and thus can be denoted as linkers, while the µ4-HPyIDC2- ligand, which connects four adjacent µ4-HPyIDC2- ligands through two Ag1 and two Ag2 centres, can be regarded as a 4-connected node. As a result, the overall framework of (I) can be described as an uninodal 4-connected network with a diamondoid topology (Zhang et al., 2008).
Thermogravimetric analysis (TGA) of (I) was carried out from 303 to 1073 K at a heating rate of 10 K min-1 in air (Fig. 4). It can be seen from the TGA curve that there is no noticeable weight loss below 573 K, indicating that the three-dimensional framework of (I) is stable up to 573 K. On heating, a large weight loss occurs in the range 573–1073 K, which can be attributed to the decomposition of the framework and loss of the organic component.
The solid-state emission spectrum of (I) was investigated at room temperature (Fig. 5). When excited at 468 nm, (I) displays a strong green photoluminescence with a maximum emission band at 550 nm. In contrast, the free H3PyIDC ligand exhibits a maximum emission at 470 nm upon excitation at 380 nm (Jing et al., 2010). The significant red shift in the emission of (I) from the free-ligand emission can probably be attributed to ligand-to-metal charge transfer (LMCT) (Allendorf et al.,2009; Sun et al., 2010).