Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807044121/nc2057sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807044121/nc2057Isup2.hkl |
CCDC reference: 663614
A mixture of Co(NO3)2.6 H2O(0.145 g, 0.5 mmol), NaN3(0.038 g, 0.5 mmol), pyridyl-2,6-dicarboxylic acid(0.085 g, 0.5 mmol) and H2O(18 g, 1 mol) in a ratio of 1:1:1:2000 was sealed in a Teflon-lined autoclave and heated at 413k for 72 h. On cooling to room temperature purple coloured crystals have grown. Yield, 30%, based on cobalt.
The H atoms were positioned with idealized geometry and were refined isotropic with Uiso(H) = 1.2 Ueq(C) using a riding model with C—H = 0.93 Å.
Poly[bis(pyridine-2,6-dicarboxylato) cobalt(II)disodium(I)] (I)is isostructural with the nickel(II) analogs, whose structures has been reported recently (Xiang et al., 2006). In the crystal structure the Co cation is coordinated by two nitrogen atoms and four oxygen atoms of two pyridine-2,6-dicarboxylato groups within an strongly distorted octahedra (Fig. 1). The Na cations are coordinated by six oxygen atoms of the pyridine-2,6-dicarboxylato anions in irregula geometry. The bis(pyridine-2,6-dicarboxylato cobalt complexes are connected by the sodium cations into a three-dimensional coordination network.
For the nickel(II) analog, see: Xiang et al. (2006).
Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT and SHELXTL (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXTL (Bruker, 1998).
Fig. 1. Crystal structure of compound (I) with labeling and displacement ellipsoids drawn at the 50% probability level. Symmetry codes: A = x,-y + 3/2,-z - 3/2. |
[Na2Co(C7H3NO4)2] | Dx = 1.922 Mg m−3 |
Mr = 435.12 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pnna | Cell parameters from 12804 reflections |
a = 14.476 (3) Å | θ = 3.2–27.6° |
b = 12.643 (3) Å | µ = 1.25 mm−1 |
c = 8.2179 (16) Å | T = 293 K |
V = 1504.0 (5) Å3 | Prism, purple |
Z = 4 | 0.5 × 0.4 × 0.4 mm |
F(000) = 868 |
Bruker SMART CCD area-detector diffractometer | 1401 independent reflections |
Radiation source: fine-focus sealed tube | 1288 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.045 |
φ and ω scan | θmax = 25.5°, θmin = 3.2° |
Absorption correction: multi-scan (SADABS; Bruker, 1998) | h = −17→17 |
Tmin = 0.560, Tmax = 0.611 | k = −15→15 |
12550 measured reflections | l = −9→9 |
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)] = 0.029 | H-atom parameters constrained |
wR(F2) = 0.069 | w = 1/[σ2(Fo2) + (0.0255P)2 + 1.1266P] where P = (Fo2 + 2Fc2)/3 |
S = 1.16 | (Δ/σ)max = 0.001 |
1401 reflections | Δρmax = 0.25 e Å−3 |
124 parameters | Δρmin = −0.28 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0131 (9) |
[Na2Co(C7H3NO4)2] | V = 1504.0 (5) Å3 |
Mr = 435.12 | Z = 4 |
Orthorhombic, Pnna | Mo Kα radiation |
a = 14.476 (3) Å | µ = 1.25 mm−1 |
b = 12.643 (3) Å | T = 293 K |
c = 8.2179 (16) Å | 0.5 × 0.4 × 0.4 mm |
Bruker SMART CCD area-detector diffractometer | 1401 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 1998) | 1288 reflections with I > 2σ(I) |
Tmin = 0.560, Tmax = 0.611 | Rint = 0.045 |
12550 measured reflections |
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.069 | H-atom parameters constrained |
S = 1.16 | Δρmax = 0.25 e Å−3 |
1401 reflections | Δρmin = −0.28 e Å−3 |
124 parameters |
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 | ||
Co1 | 0.48472 (3) | 0.7500 | −0.7500 | 0.02158 (17) | |
Na1 | 0.26971 (6) | 0.64416 (7) | −0.10636 (11) | 0.0271 (2) | |
N1 | 0.46109 (12) | 0.59694 (13) | −0.6959 (2) | 0.0184 (4) | |
O3 | 0.38369 (11) | 0.75524 (11) | −0.5514 (2) | 0.0323 (4) | |
C5 | 0.39461 (13) | 0.57119 (16) | −0.5917 (2) | 0.0187 (4) | |
C2 | 0.48779 (15) | 0.41704 (17) | −0.7593 (3) | 0.0229 (5) | |
H2A | 0.5199 | 0.3657 | −0.8174 | 0.027* | |
C1 | 0.50857 (14) | 0.52354 (17) | −0.7765 (2) | 0.0186 (5) | |
C4 | 0.37083 (15) | 0.46689 (17) | −0.5658 (3) | 0.0242 (5) | |
H4A | 0.3247 | 0.4489 | −0.4920 | 0.029* | |
C3 | 0.41763 (16) | 0.38953 (17) | −0.6527 (3) | 0.0271 (5) | |
H3A | 0.4018 | 0.3188 | −0.6394 | 0.033* | |
O4 | 0.29805 (11) | 0.65269 (13) | −0.39208 (19) | 0.0290 (4) | |
C7 | 0.35443 (14) | 0.66626 (16) | −0.5038 (3) | 0.0219 (5) | |
O1 | 0.59125 (11) | 0.66942 (12) | −0.87976 (19) | 0.0272 (4) | |
C6 | 0.58828 (14) | 0.56926 (16) | −0.8724 (3) | 0.0204 (5) | |
O2 | 0.64704 (10) | 0.50923 (12) | −0.9290 (2) | 0.0307 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Co1 | 0.0246 (3) | 0.0128 (2) | 0.0274 (3) | 0.000 | 0.000 | −0.00046 (17) |
Na1 | 0.0257 (5) | 0.0220 (4) | 0.0336 (5) | −0.0015 (4) | 0.0005 (4) | −0.0036 (4) |
N1 | 0.0182 (9) | 0.0156 (9) | 0.0215 (9) | 0.0007 (7) | −0.0011 (7) | −0.0013 (7) |
O3 | 0.0372 (9) | 0.0189 (8) | 0.0408 (10) | −0.0002 (7) | 0.0139 (8) | −0.0046 (7) |
C5 | 0.0165 (10) | 0.0207 (11) | 0.0190 (10) | −0.0004 (8) | −0.0016 (8) | −0.0009 (9) |
C2 | 0.0242 (11) | 0.0176 (11) | 0.0269 (12) | 0.0026 (9) | −0.0038 (9) | −0.0047 (9) |
C1 | 0.0186 (10) | 0.0172 (11) | 0.0200 (11) | 0.0021 (8) | −0.0041 (8) | −0.0013 (8) |
C4 | 0.0225 (11) | 0.0221 (11) | 0.0280 (12) | −0.0035 (9) | 0.0009 (9) | 0.0028 (9) |
C3 | 0.0306 (12) | 0.0150 (10) | 0.0357 (13) | −0.0049 (9) | −0.0031 (10) | 0.0010 (9) |
O4 | 0.0253 (8) | 0.0332 (9) | 0.0284 (9) | −0.0032 (7) | 0.0080 (7) | −0.0075 (7) |
C7 | 0.0172 (10) | 0.0234 (11) | 0.0250 (11) | 0.0003 (9) | −0.0015 (9) | −0.0046 (10) |
O1 | 0.0262 (8) | 0.0189 (8) | 0.0365 (9) | −0.0022 (6) | 0.0074 (7) | −0.0010 (7) |
C6 | 0.0194 (10) | 0.0218 (11) | 0.0201 (11) | 0.0018 (9) | −0.0031 (9) | −0.0012 (9) |
O2 | 0.0245 (8) | 0.0277 (8) | 0.0398 (10) | 0.0075 (7) | 0.0074 (7) | −0.0022 (7) |
Co1—N1i | 2.0149 (17) | O3—Na1iii | 2.4538 (17) |
Co1—N1 | 2.0149 (17) | C5—C4 | 1.379 (3) |
Co1—O1i | 2.1338 (16) | C5—C7 | 1.518 (3) |
Co1—O1 | 2.1338 (16) | C2—C3 | 1.386 (3) |
Co1—O3i | 2.1923 (16) | C2—C1 | 1.387 (3) |
Co1—O3 | 2.1923 (16) | C2—H2A | 0.9300 |
Na1—O2ii | 2.3017 (18) | C1—C6 | 1.512 (3) |
Na1—O4 | 2.3860 (19) | C4—C3 | 1.388 (3) |
Na1—O3iii | 2.4538 (17) | C4—H4A | 0.9300 |
Na1—O2iv | 2.4795 (18) | C3—H3A | 0.9300 |
Na1—O4iii | 2.6009 (19) | O4—C7 | 1.240 (3) |
Na1—O1iv | 2.6056 (18) | O4—Na1iii | 2.6009 (19) |
Na1—C6iv | 2.797 (2) | C7—Na1iii | 2.840 (2) |
Na1—C7iii | 2.840 (2) | O1—C6 | 1.268 (3) |
Na1—Na1iii | 3.5686 (18) | O1—Na1vi | 2.6056 (18) |
Na1—Na1v | 3.6896 (18) | C6—O2 | 1.231 (3) |
N1—C5 | 1.329 (3) | C6—Na1vi | 2.797 (2) |
N1—C1 | 1.331 (3) | O2—Na1ii | 2.3017 (18) |
O3—C7 | 1.264 (3) | O2—Na1vi | 2.4795 (18) |
N1i—Co1—N1 | 160.46 (10) | O2ii—Na1—Na1v | 41.28 (4) |
N1i—Co1—O1i | 76.97 (6) | O4—Na1—Na1v | 94.08 (4) |
N1—Co1—O1i | 118.09 (6) | O3iii—Na1—Na1v | 128.03 (5) |
N1i—Co1—O1 | 118.09 (6) | O2iv—Na1—Na1v | 37.77 (4) |
N1—Co1—O1 | 76.97 (6) | O4iii—Na1—Na1v | 179.67 (5) |
O1i—Co1—O1 | 87.44 (9) | O1iv—Na1—Na1v | 88.15 (5) |
N1i—Co1—O3i | 75.60 (6) | C6iv—Na1—Na1v | 61.34 (5) |
N1—Co1—O3i | 91.27 (6) | C7iii—Na1—Na1v | 154.22 (5) |
O1i—Co1—O3i | 150.29 (6) | Na1iii—Na1—Na1v | 137.81 (3) |
O1—Co1—O3i | 95.49 (6) | C5—N1—C1 | 121.60 (18) |
N1i—Co1—O3 | 91.27 (6) | C5—N1—Co1 | 120.04 (14) |
N1—Co1—O3 | 75.60 (6) | C1—N1—Co1 | 118.15 (14) |
O1i—Co1—O3 | 95.49 (6) | C7—O3—Co1 | 115.29 (13) |
O1—Co1—O3 | 150.29 (6) | C7—O3—Na1iii | 94.14 (13) |
O3i—Co1—O3 | 96.31 (10) | Co1—O3—Na1iii | 149.04 (8) |
O2ii—Na1—O4 | 94.15 (6) | N1—C5—C4 | 120.97 (19) |
O2ii—Na1—O3iii | 91.02 (6) | N1—C5—C7 | 112.96 (18) |
O4—Na1—O3iii | 112.39 (7) | C4—C5—C7 | 126.00 (19) |
O2ii—Na1—O2iv | 77.32 (6) | C3—C2—C1 | 117.9 (2) |
O4—Na1—O2iv | 105.64 (6) | C3—C2—H2A | 121.1 |
O3iii—Na1—O2iv | 140.91 (7) | C1—C2—H2A | 121.1 |
O2ii—Na1—O4iii | 138.59 (6) | N1—C1—C2 | 120.92 (19) |
O4—Na1—O4iii | 85.61 (6) | N1—C1—C6 | 112.77 (18) |
O3iii—Na1—O4iii | 52.03 (5) | C2—C1—C6 | 126.14 (19) |
O2iv—Na1—O4iii | 142.46 (6) | C5—C4—C3 | 118.2 (2) |
O2ii—Na1—O1iv | 128.90 (6) | C5—C4—H4A | 120.9 |
O4—Na1—O1iv | 97.00 (6) | C3—C4—H4A | 120.9 |
O3iii—Na1—O1iv | 128.78 (6) | C2—C3—C4 | 120.4 (2) |
O2iv—Na1—O1iv | 51.64 (5) | C2—C3—H3A | 119.8 |
O4iii—Na1—O1iv | 92.02 (5) | C4—C3—H3A | 119.8 |
O2ii—Na1—C6iv | 102.37 (7) | C7—O4—Na1 | 147.97 (14) |
O4—Na1—C6iv | 96.62 (6) | C7—O4—Na1iii | 87.91 (13) |
O3iii—Na1—C6iv | 147.12 (7) | Na1—O4—Na1iii | 91.28 (6) |
O2iv—Na1—C6iv | 26.11 (6) | O4—C7—O3 | 125.0 (2) |
O4iii—Na1—C6iv | 118.82 (6) | O4—C7—C5 | 119.65 (19) |
O1iv—Na1—C6iv | 26.86 (5) | O3—C7—C5 | 115.38 (18) |
O2ii—Na1—C7iii | 116.40 (7) | O4—C7—Na1iii | 66.22 (12) |
O4—Na1—C7iii | 101.61 (7) | O3—C7—Na1iii | 59.51 (11) |
O3iii—Na1—C7iii | 26.35 (6) | C5—C7—Na1iii | 170.10 (15) |
O2iv—Na1—C7iii | 148.47 (7) | C6—O1—Co1 | 115.36 (14) |
O4iii—Na1—C7iii | 25.87 (5) | C6—O1—Na1vi | 85.03 (12) |
O1iv—Na1—C7iii | 109.79 (6) | Co1—O1—Na1vi | 142.84 (8) |
C6iv—Na1—C7iii | 135.31 (7) | O2—C6—O1 | 125.0 (2) |
O2ii—Na1—Na1iii | 135.68 (5) | O2—C6—C1 | 119.25 (19) |
O4—Na1—Na1iii | 46.77 (4) | O1—C6—C1 | 115.61 (18) |
O3iii—Na1—Na1iii | 87.76 (5) | O2—C6—Na1vi | 62.38 (12) |
O2iv—Na1—Na1iii | 126.41 (5) | O1—C6—Na1vi | 68.12 (12) |
O4iii—Na1—Na1iii | 41.95 (4) | C1—C6—Na1vi | 151.45 (14) |
O1iv—Na1—Na1iii | 83.06 (4) | C6—O2—Na1ii | 146.43 (15) |
C6iv—Na1—Na1iii | 102.27 (5) | C6—O2—Na1vi | 91.51 (13) |
C7iii—Na1—Na1iii | 65.04 (5) | Na1ii—O2—Na1vi | 100.95 (6) |
N1i—Co1—N1—C5 | −41.45 (15) | O1iv—Na1—O4—Na1iii | 73.59 (6) |
O1i—Co1—N1—C5 | 96.22 (16) | C6iv—Na1—O4—Na1iii | 100.64 (6) |
O1—Co1—N1—C5 | 176.12 (16) | C7iii—Na1—O4—Na1iii | −38.34 (7) |
O3i—Co1—N1—C5 | −88.54 (16) | Na1v—Na1—O4—Na1iii | 162.22 (3) |
O3—Co1—N1—C5 | 7.66 (15) | Na1—O4—C7—O3 | −79.0 (4) |
N1i—Co1—N1—C1 | 133.33 (15) | Na1iii—O4—C7—O3 | 10.1 (2) |
O1i—Co1—N1—C1 | −88.99 (16) | Na1—O4—C7—C5 | 99.9 (3) |
O1—Co1—N1—C1 | −9.10 (15) | Na1iii—O4—C7—C5 | −171.07 (17) |
O3i—Co1—N1—C1 | 86.25 (16) | Na1—O4—C7—Na1iii | −89.1 (2) |
O3—Co1—N1—C1 | −177.56 (16) | Co1—O3—C7—O4 | 179.17 (17) |
N1i—Co1—O3—C7 | 161.39 (16) | Na1iii—O3—C7—O4 | −10.7 (2) |
N1—Co1—O3—C7 | −3.95 (16) | Co1—O3—C7—C5 | 0.3 (2) |
O1i—Co1—O3—C7 | −121.58 (16) | Na1iii—O3—C7—C5 | 170.39 (15) |
O1—Co1—O3—C7 | −27.1 (2) | Co1—O3—C7—Na1iii | −170.12 (15) |
O3i—Co1—O3—C7 | 85.74 (16) | N1—C5—C7—O4 | −173.18 (18) |
N1i—Co1—O3—Na1iii | 0.83 (17) | C4—C5—C7—O4 | 3.7 (3) |
N1—Co1—O3—Na1iii | −164.51 (18) | N1—C5—C7—O3 | 5.8 (3) |
O1i—Co1—O3—Na1iii | 77.86 (17) | C4—C5—C7—O3 | −177.3 (2) |
O1—Co1—O3—Na1iii | 172.34 (12) | N1—C5—C7—Na1iii | 62.5 (9) |
O3i—Co1—O3—Na1iii | −74.82 (16) | C4—C5—C7—Na1iii | −120.5 (8) |
C1—N1—C5—C4 | −1.4 (3) | N1i—Co1—O1—C6 | −162.89 (14) |
Co1—N1—C5—C4 | 173.17 (16) | N1—Co1—O1—C6 | 3.74 (15) |
C1—N1—C5—C7 | 175.65 (18) | O1i—Co1—O1—C6 | 123.35 (17) |
Co1—N1—C5—C7 | −9.7 (2) | O3i—Co1—O1—C6 | −86.29 (15) |
C5—N1—C1—C2 | 2.5 (3) | O3—Co1—O1—C6 | 26.7 (2) |
Co1—N1—C1—C2 | −172.17 (16) | N1i—Co1—O1—Na1vi | 79.30 (13) |
C5—N1—C1—C6 | −172.97 (17) | N1—Co1—O1—Na1vi | −114.07 (13) |
Co1—N1—C1—C6 | 12.3 (2) | O1i—Co1—O1—Na1vi | 5.54 (7) |
C3—C2—C1—N1 | −1.5 (3) | O3i—Co1—O1—Na1vi | 155.90 (12) |
C3—C2—C1—C6 | 173.37 (19) | O3—Co1—O1—Na1vi | −91.06 (16) |
N1—C5—C4—C3 | −0.6 (3) | Co1—O1—C6—O2 | −174.52 (17) |
C7—C5—C4—C3 | −177.3 (2) | Na1vi—O1—C6—O2 | −27.0 (2) |
C1—C2—C3—C4 | −0.6 (3) | Co1—O1—C6—C1 | 1.4 (2) |
C5—C4—C3—C2 | 1.6 (3) | Na1vi—O1—C6—C1 | 149.01 (16) |
O2ii—Na1—O4—C7 | −68.3 (3) | Co1—O1—C6—Na1vi | −147.57 (12) |
O3iii—Na1—O4—C7 | 24.6 (3) | N1—C1—C6—O2 | 167.43 (19) |
O2iv—Na1—O4—C7 | −146.3 (3) | C2—C1—C6—O2 | −7.8 (3) |
O4iii—Na1—O4—C7 | 70.2 (3) | N1—C1—C6—O1 | −8.8 (3) |
O1iv—Na1—O4—C7 | 161.7 (3) | C2—C1—C6—O1 | 176.0 (2) |
C6iv—Na1—O4—C7 | −171.3 (3) | N1—C1—C6—Na1vi | 82.2 (3) |
C7iii—Na1—O4—C7 | 49.8 (3) | C2—C1—C6—Na1vi | −93.1 (3) |
Na1iii—Na1—O4—C7 | 88.1 (3) | O1—C6—O2—Na1ii | 140.9 (2) |
Na1v—Na1—O4—C7 | −109.7 (3) | C1—C6—O2—Na1ii | −35.0 (4) |
O2ii—Na1—O4—Na1iii | −156.38 (5) | Na1vi—C6—O2—Na1ii | 112.5 (3) |
O3iii—Na1—O4—Na1iii | −63.55 (7) | O1—C6—O2—Na1vi | 28.3 (2) |
O2iv—Na1—O4—Na1iii | 125.64 (5) | C1—C6—O2—Na1vi | −147.49 (16) |
O4iii—Na1—O4—Na1iii | −17.91 (7) |
Symmetry codes: (i) x, −y+3/2, −z−3/2; (ii) −x+1, −y+1, −z−1; (iii) x, −y+3/2, −z−1/2; (iv) x−1/2, y, −z−1; (v) −x+1/2, −y+1, z; (vi) x+1/2, y, −z−1. |
Experimental details
Crystal data | |
Chemical formula | [Na2Co(C7H3NO4)2] |
Mr | 435.12 |
Crystal system, space group | Orthorhombic, Pnna |
Temperature (K) | 293 |
a, b, c (Å) | 14.476 (3), 12.643 (3), 8.2179 (16) |
V (Å3) | 1504.0 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.25 |
Crystal size (mm) | 0.5 × 0.4 × 0.4 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector |
Absorption correction | Multi-scan (SADABS; Bruker, 1998) |
Tmin, Tmax | 0.560, 0.611 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12550, 1401, 1288 |
Rint | 0.045 |
(sin θ/λ)max (Å−1) | 0.606 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.069, 1.16 |
No. of reflections | 1401 |
No. of parameters | 124 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.25, −0.28 |
Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1998), SAINT and SHELXTL (Bruker, 1998), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1998).
Poly[bis(pyridine-2,6-dicarboxylato) cobalt(II)disodium(I)] (I)is isostructural with the nickel(II) analogs, whose structures has been reported recently (Xiang et al., 2006). In the crystal structure the Co cation is coordinated by two nitrogen atoms and four oxygen atoms of two pyridine-2,6-dicarboxylato groups within an strongly distorted octahedra (Fig. 1). The Na cations are coordinated by six oxygen atoms of the pyridine-2,6-dicarboxylato anions in irregula geometry. The bis(pyridine-2,6-dicarboxylato cobalt complexes are connected by the sodium cations into a three-dimensional coordination network.