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The basic units in the structure of the title compound, {[UO2(C6H7NO6)(H2O)2]·3H2O}n, are ribbons in which every UO22+ cation is coordinated in a monodentate manner to three tridentate-bridging nitriliotriacetate dianions. Hydrogen bonds bind the ribbons into a three-dimensional structure.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106006949/fa3002sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106006949/fa3002Isup2.hkl
Contains datablock I

CCDC reference: 605670

Comment top

In the field of human toxicology, internal contamination with actinides under either acute or chronic conditions has the potential to induce both radiological and chemical toxicity. At the molecular level, general understanding of the interactions engaged in actinide adducts, i.e. physical chemical mechanisms that drive the affinity of possible coordination sites for actinide cations still needs to be deepened. As a result, the intramolecular interactions of actinide elements with either smart chelates designed for coordination and bioorganic chemistry or naturally occurring chelating agents are relatively unknown.

Nitrilotriacetic acid [H3nta, NH(CH2COO)(CH2COOH)2] is a derivative of glycine commonly used in biochemistry and medicine. It behaves as a tri- or tetradentate aminocarboxylate chelate that is well known in complex transition metal cations. Lanthanides(III) can also form three-dimensional structures with nta3− anions in various patterns (Wang et al., 2004). It can also be used as a protecting group for actinides(IV) (NpIV and PuIV against hydrolysis at physiological pH).

The present investigation of the complexation of uranium by nitrilotriacetic acid is aimed at a broader understanding of the interaction of actinides with biological ligands.

The U atom in the title compound, (I), is seven-coordinate, its coordination polyhedron being a distorted pentagonal bipyramid with equatorial positions occupied by three O atoms of three Hnta2− anions and two O atoms of coordinated water molecules (Fig. 1). Bond lengths in the U-atom environment are given in Table 1. The Hnta2− anions act as tridentate bridging ligands, forming infinite ribbons with uranyl cations in the [010] direction (Fig. 2).

The central N atom in the Hnta2− anion is protonated, preventing this atom from coordinating to U. This H atom forms three intramolecular hydrogen bonds, typical of nitrilotriacetate anions (Antsyshkina et al., 1997; Davidovich et al., 2002, Ilyukhin et al., 1998, 1999; Oliver et al., 1984), with the non-coordinated O atoms of the carboxylate groups acting as receptors (Fig. 1 and Table 2). This hydrogen bonding gives the anion nearly C3 symmetry, as can be seen from the torsion angles given in Table 1. For this symmetric conformation of the anion the distances between the unligated O atoms of different carboxylate groups are greater than 3.5 Å; the shortest is O4···O8 [3.539 (5) Å]. Comparing this with the O···O distances in the equatorial plane of the uranyl cation [range 2.769 (5)–2.889 (5) Å, average 2.81 (2) Å], we infer that intramolecular hydrogen bonding can be a factor preventing the Hnta2− anion from chelating U with the formation of an eight-membered ring. Nevertheless, single-carboxylate chelation with the formation of a four-membered ring still seems to be possible.

Coordinated and crystallization water molecules participate in a number of hydrogen bonds (Table 2). The O10—H10B···O6i hydorgen bonds link the ribbons into layers in the (002) planes. The hydrogen bonds in which the uncoordinated water molecules participate bind the layers into a three-dimensional structure. Only one hydrogen bond can be found in which the H2O13 water molecule acts as a donor. This may be the reason that only one H atom of this molecule was located.

Experimental top

For the preparation of (I), a 0.1 M solution of Na2Hnta (pH \sim 5, 0.125 ml) was added to a 0.025 M UO2(NO3)2 solution (pH ~2, 0.5 ml). After several days of storage at room temperature, agglomerates of yellow needles appeared.

Refinement top

The H atoms were located from difference Fourier syntheses, except for one H atom of one of the three solvent water molecules. The H atoms of CH2 groups were refined as riding in idealized positions (C—H = 0.99 Å), with displacement parameters equal to 1.2 times those of the attached C atoms. The H atoms of water molecules were refined with restraints on the O—H distances and H—O—H angles, the displacement parameters being equal to 1.2 times those of the attached O atoms. For the H atom attached to the N atom, only its orientation was fixed during refinement. The largest electron density peaks in the final difference Fourier synthesis are 2.02 e Å−3 (1.06 Å from atom O5 and 1.73 Å from atom U) and 1.69 e Å−3 (1.59 Å from H3B), and the deepest hole is 0.87 Å from atom U.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: HKL Package (Otwinowski & Minor, 1997); data reduction: HKL Package; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. A view of [UO2(Hnta)(H2O)2]·3H2O, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are represented by circles of arbitrary size. Dashed lines indicate the hydrogen-bonding interactions. [Symmetry code: (i) −x + 1/2, y + 1/2, −z + 1/2; (ii) −x + 1/2, y − 1/2, −z + 1/2.]
[Figure 2] Fig. 2. A [UO2(Hnta)(H2O)2]n ribbon in the structure of [UO2(Hnta)(H2O)2]·3H2O.
Poly[[[diaquadioxouranium(VI)]-µ3-nitriliotriacetato-κ3O:O':O''] trihydrate] top
Crystal data top
[U(C6H7O6)O2(H2O)2]·3H2OF(000) = 1024
Mr = 549.24Dx = 2.536 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 16104 reflections
a = 10.8858 (3) Åθ = 2.5–27.4°
b = 9.9530 (2) ŵ = 11.35 mm1
c = 13.3275 (3) ÅT = 120 K
β = 95.0178 (15)°Parallelepiped, yellow
V = 1438.45 (6) Å30.10 × 0.06 × 0.04 mm
Z = 4
Data collection top
Nonius KappaCCD area-detector
diffractometer
3240 independent reflections
Radiation source: fine-focus sealed tube2599 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.065
ϕ– and ω scansθmax = 27.4°, θmin = 2.5°
Absorption correction: multi-scan
(MULABS in PLATON; Spek, 2003)
h = 1413
Tmin = 0.487, Tmax = 0.635k = 1212
16104 measured reflectionsl = 1617
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.029Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.061H atoms treated by a mixture of independent and constrained refinement
S = 1.03 w = 1/[σ2(Fo2) + (0.0254P)2]
where P = (Fo2 + 2Fc2)/3
3240 reflections(Δ/σ)max = 0.061
221 parametersΔρmax = 2.02 e Å3
16 restraintsΔρmin = 1.71 e Å3
Crystal data top
[U(C6H7O6)O2(H2O)2]·3H2OV = 1438.45 (6) Å3
Mr = 549.24Z = 4
Monoclinic, P21/nMo Kα radiation
a = 10.8858 (3) ŵ = 11.35 mm1
b = 9.9530 (2) ÅT = 120 K
c = 13.3275 (3) Å0.10 × 0.06 × 0.04 mm
β = 95.0178 (15)°
Data collection top
Nonius KappaCCD area-detector
diffractometer
3240 independent reflections
Absorption correction: multi-scan
(MULABS in PLATON; Spek, 2003)
2599 reflections with I > 2σ(I)
Tmin = 0.487, Tmax = 0.635Rint = 0.065
16104 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.02916 restraints
wR(F2) = 0.061H atoms treated by a mixture of independent and constrained refinement
S = 1.03Δρmax = 2.02 e Å3
3240 reflectionsΔρmin = 1.71 e Å3
221 parameters
Special details top

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 (Å2) top
xyzUiso*/Ueq
U0.617473 (17)0.705417 (17)0.327790 (14)0.01074 (7)
O10.5419 (3)0.6416 (3)0.4305 (3)0.0161 (8)
O20.6979 (3)0.7639 (3)0.2268 (3)0.0160 (8)
O30.4276 (3)0.7658 (3)0.2330 (3)0.0151 (8)
O40.2905 (3)0.6285 (3)0.2961 (3)0.0173 (8)
O50.0625 (3)0.4240 (3)0.1211 (3)0.0160 (8)
O60.0431 (3)0.5496 (3)0.2622 (3)0.0182 (8)
O70.0575 (3)1.0253 (3)0.2809 (3)0.0163 (8)
O80.0676 (4)0.8691 (4)0.3533 (3)0.0231 (9)
O90.7827 (3)0.7945 (4)0.4450 (3)0.0170 (8)
H9A0.798 (5)0.877 (2)0.454 (4)0.020*
H9B0.848 (3)0.751 (4)0.460 (4)0.020*
O100.7652 (3)0.5354 (3)0.3694 (3)0.0157 (8)
H10A0.767 (5)0.466 (3)0.404 (3)0.019*
H10B0.818 (4)0.529 (5)0.328 (3)0.019*
O120.7413 (5)0.3297 (4)0.4932 (3)0.0393 (13)
H12A0.774 (7)0.252 (4)0.495 (5)0.047*
H12B0.726 (7)0.345 (6)0.554 (2)0.047*
O130.9759 (4)0.6448 (5)0.5289 (3)0.0317 (10)
H13A0.991 (6)0.642 (7)0.5909 (16)0.038*
N0.0961 (4)0.7338 (4)0.1901 (3)0.0102 (9)
H10.1005 (15)0.705 (3)0.250 (5)0.03 (2)*
C10.2203 (5)0.7937 (5)0.1763 (4)0.0126 (11)
H1A0.22060.88990.19520.015*
H1B0.23680.78730.10460.015*
C20.3204 (5)0.7204 (5)0.2409 (4)0.0142 (11)
C30.0655 (5)0.6148 (5)0.1245 (4)0.0140 (11)
H3A0.14190.56530.11300.017*
H3B0.02650.64480.05840.017*
C40.0223 (5)0.5230 (5)0.1752 (4)0.0136 (11)
C50.0031 (5)0.8380 (5)0.1815 (4)0.0131 (11)
H5A0.08490.79480.16950.016*
H5B0.00860.89910.12450.016*
C60.0050 (5)0.9166 (5)0.2802 (4)0.0132 (11)
O110.8345 (4)1.0573 (4)0.4641 (3)0.0208 (9)
H11A0.876 (4)1.067 (6)0.5206 (19)0.025*
H11B0.884 (4)1.073 (6)0.420 (3)0.025*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
U0.00950 (11)0.00953 (10)0.01327 (11)0.00028 (8)0.00147 (7)0.00067 (8)
O10.015 (2)0.0121 (18)0.022 (2)0.0000 (16)0.0055 (16)0.0017 (15)
O20.013 (2)0.0127 (18)0.022 (2)0.0014 (15)0.0025 (16)0.0004 (15)
O30.0096 (19)0.0140 (18)0.021 (2)0.0009 (15)0.0043 (15)0.0027 (15)
O40.018 (2)0.0127 (18)0.021 (2)0.0013 (16)0.0013 (16)0.0045 (16)
O50.015 (2)0.0133 (18)0.019 (2)0.0065 (15)0.0010 (16)0.0025 (15)
O60.021 (2)0.0177 (19)0.017 (2)0.0059 (16)0.0061 (16)0.0031 (16)
O70.020 (2)0.0127 (18)0.0162 (19)0.0036 (16)0.0042 (16)0.0014 (15)
O80.029 (2)0.023 (2)0.017 (2)0.0111 (19)0.0040 (18)0.0025 (17)
O90.012 (2)0.0134 (18)0.024 (2)0.0029 (16)0.0075 (16)0.0002 (17)
O100.014 (2)0.0118 (18)0.021 (2)0.0037 (16)0.0039 (16)0.0043 (16)
O120.072 (4)0.024 (2)0.024 (2)0.012 (2)0.019 (3)0.0070 (19)
O130.027 (2)0.048 (3)0.019 (2)0.004 (2)0.003 (2)0.006 (2)
N0.010 (2)0.010 (2)0.011 (2)0.0016 (17)0.0024 (17)0.0003 (17)
C10.011 (3)0.010 (2)0.016 (3)0.004 (2)0.003 (2)0.001 (2)
C20.014 (3)0.013 (3)0.015 (3)0.001 (2)0.002 (2)0.002 (2)
C30.014 (3)0.010 (2)0.018 (3)0.003 (2)0.002 (2)0.002 (2)
C40.010 (3)0.012 (2)0.018 (3)0.001 (2)0.002 (2)0.003 (2)
C50.012 (3)0.015 (2)0.012 (3)0.001 (2)0.001 (2)0.002 (2)
C60.013 (3)0.013 (3)0.014 (3)0.002 (2)0.003 (2)0.001 (2)
O110.026 (2)0.024 (2)0.013 (2)0.0034 (18)0.0011 (18)0.0003 (17)
Geometric parameters (Å, º) top
U—O11.775 (3)O12—H12A0.852 (19)
U—O21.767 (3)O12—H12B0.851 (19)
U—O32.402 (4)O13—H13A0.83 (2)
U—O92.443 (4)N—C31.493 (6)
U—O102.367 (3)N—C51.493 (6)
U—O5i2.372 (3)N—C11.504 (6)
U—O7ii2.361 (3)N—H10.84 (7)
O3—C21.265 (6)C1—C21.515 (7)
O4—C21.236 (6)C1—H1A0.9900
O5—C41.275 (6)C1—H1B0.9900
O5—Uii2.372 (3)C3—C41.522 (7)
O6—C41.230 (6)C3—H3A0.9900
O7—C61.278 (6)C3—H3B0.9900
O7—Ui2.361 (3)C5—C61.526 (7)
O8—C61.233 (6)C5—H5A0.9900
O9—H9A0.842 (19)C5—H5B0.9900
O9—H9B0.836 (19)O11—H11A0.848 (19)
O10—H10A0.827 (19)O11—H11B0.849 (19)
O10—H10B0.841 (19)
O2—U—O1177.52 (16)C5—N—C1111.5 (4)
O2—U—O7ii84.96 (14)C3—N—H1106.1 (12)
O1—U—O7ii94.56 (14)C5—N—H1106.8 (12)
O2—U—O1092.41 (15)C1—N—H1105.7 (12)
O1—U—O1085.11 (14)N—C1—C2110.5 (4)
O7ii—U—O1075.33 (13)N—C1—H1A109.6
O2—U—O5i94.05 (14)C2—C1—H1A109.6
O1—U—O5i87.77 (14)N—C1—H1B109.6
O7ii—U—O5i144.04 (13)C2—C1—H1B109.6
O10—U—O5i140.51 (13)H1A—C1—H1B108.1
O2—U—O388.75 (15)O4—C2—O3127.4 (5)
O1—U—O393.41 (15)O4—C2—C1118.7 (5)
O7ii—U—O371.83 (12)O3—C2—C1113.9 (4)
O10—U—O3146.90 (12)N—C3—C4109.4 (4)
O5i—U—O372.22 (12)N—C3—H3A109.8
O2—U—O988.89 (15)C4—C3—H3A109.8
O1—U—O990.11 (15)N—C3—H3B109.8
O7ii—U—O9144.74 (12)C4—C3—H3B109.8
O10—U—O970.28 (12)H3A—C3—H3B108.2
O5i—U—O970.95 (12)O6—C4—O5128.1 (5)
O3—U—O9142.82 (12)O6—C4—C3117.7 (5)
C2—O3—U128.7 (3)O5—C4—C3114.3 (4)
C4—O5—Uii129.0 (3)N—C5—C6107.6 (4)
C6—O7—Ui139.2 (3)N—C5—H5A110.2
U—O9—H9A125 (3)C6—C5—H5A110.2
U—O9—H9B122 (4)N—C5—H5B110.2
H9A—O9—H9B108 (3)C6—C5—H5B110.2
U—O10—H10A135 (3)H5A—C5—H5B108.5
U—O10—H10B113 (3)O8—C6—O7125.2 (5)
H10A—O10—H10B109 (3)O8—C6—C5118.0 (4)
H12A—O12—H12B105 (3)O7—C6—C5116.7 (5)
C3—N—C5112.5 (4)H11A—O11—H11B106 (3)
C3—N—C1113.5 (4)
O2—U—O3—C2156.8 (4)C5—N—C1—C2146.7 (4)
O1—U—O3—C222.0 (4)C1—N—C5—C677.4 (5)
O7ii—U—O3—C271.7 (4)C3—N—C1—C284.9 (5)
O10—U—O3—C264.3 (5)C5—N—C3—C479.8 (5)
O5i—U—O3—C2108.6 (4)N—C1—C2—O3179.9 (4)
O9—U—O3—C2116.7 (4)N—C3—C4—O5174.2 (4)
U—O3—C2—O44.4 (8)N—C5—C6—O7167.7 (4)
U—O3—C2—C1173.4 (3)N—C1—C2—O42.0 (6)
C1—N—C3—C4152.3 (4)N—C3—C4—O67.8 (7)
Uii—O5—C4—O629.4 (8)N—C5—C6—O814.3 (6)
Uii—O5—C4—C3148.4 (3)Ui—O7—C6—O8146.2 (4)
C3—N—C5—C6153.7 (4)Ui—O7—C6—C536.0 (7)
Symmetry codes: (i) x+1/2, y+1/2, z+1/2; (ii) x+1/2, y1/2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O9—H9A···O110.84 (2)1.84 (2)2.683 (5)175 (6)
O9—H9B···O130.84 (2)1.92 (2)2.735 (6)164 (6)
O10—H10A···O120.83 (2)1.84 (2)2.656 (5)167 (5)
O10—H10B···O6iii0.84 (2)1.82 (2)2.634 (5)163 (6)
O11—H11A···O8iv0.85 (2)1.85 (2)2.673 (5)163 (6)
O11—H11B···O7iii0.85 (2)2.07 (3)2.819 (5)148 (5)
O12—H12A···O11v0.85 (2)2.10 (2)2.932 (6)166 (6)
O12—H12B···O4vi0.85 (2)2.04 (2)2.890 (5)173 (6)
O13—H13A···O3vii0.83 (2)2.27 (5)2.953 (5)140 (6)
N—H1···O40.84 (7)2.24 (3)2.655 (6)111 (2)
N—H1···O60.84 (7)2.22 (3)2.614 (5)109 (2)
N—H1···O80.84 (7)2.19 (3)2.599 (5)110 (2)
Symmetry codes: (iii) x+1, y, z; (iv) x+1, y+2, z+1; (v) x, y1, z; (vi) x+1, y+1, z+1; (vii) x+1/2, y+3/2, z+1/2.

Experimental details

Crystal data
Chemical formula[U(C6H7O6)O2(H2O)2]·3H2O
Mr549.24
Crystal system, space groupMonoclinic, P21/n
Temperature (K)120
a, b, c (Å)10.8858 (3), 9.9530 (2), 13.3275 (3)
β (°) 95.0178 (15)
V3)1438.45 (6)
Z4
Radiation typeMo Kα
µ (mm1)11.35
Crystal size (mm)0.10 × 0.06 × 0.04
Data collection
DiffractometerNonius KappaCCD area-detector
diffractometer
Absorption correctionMulti-scan
(MULABS in PLATON; Spek, 2003)
Tmin, Tmax0.487, 0.635
No. of measured, independent and
observed [I > 2σ(I)] reflections
16104, 3240, 2599
Rint0.065
(sin θ/λ)max1)0.648
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.029, 0.061, 1.03
No. of reflections3240
No. of parameters221
No. of restraints16
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)2.02, 1.71

Computer programs: COLLECT (Nonius, 1998), HKL Package (Otwinowski & Minor, 1997), HKL Package, SHELXS97 (Sheldrick, 1997a), SHELXL97 (Sheldrick, 1997a), SHELXTL (Sheldrick, 1997b), SHELXTL.

Selected geometric parameters (Å, º) top
U—O11.775 (3)U—O102.367 (3)
U—O21.767 (3)U—O5i2.372 (3)
U—O32.402 (4)U—O7ii2.361 (3)
U—O92.443 (4)
C1—N—C3—C4152.3 (4)N—C1—C2—O3179.9 (4)
C3—N—C5—C6153.7 (4)N—C3—C4—O5174.2 (4)
C5—N—C1—C2146.7 (4)N—C5—C6—O7167.7 (4)
C1—N—C5—C677.4 (5)N—C1—C2—O42.0 (6)
C3—N—C1—C284.9 (5)N—C3—C4—O67.8 (7)
C5—N—C3—C479.8 (5)N—C5—C6—O814.3 (6)
Symmetry codes: (i) x+1/2, y+1/2, z+1/2; (ii) x+1/2, y1/2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O9—H9A···O110.842 (19)1.84 (2)2.683 (5)175 (6)
O9—H9B···O130.836 (19)1.92 (2)2.735 (6)164 (6)
O10—H10A···O120.827 (19)1.84 (2)2.656 (5)167 (5)
O10—H10B···O6iii0.841 (19)1.82 (2)2.634 (5)163 (6)
O11—H11A···O8iv0.848 (19)1.85 (2)2.673 (5)163 (6)
O11—H11B···O7iii0.849 (19)2.07 (3)2.819 (5)148 (5)
O12—H12A···O11v0.852 (19)2.10 (2)2.932 (6)166 (6)
O12—H12B···O4vi0.851 (19)2.04 (2)2.890 (5)173 (6)
O13—H13A···O3vii0.83 (2)2.27 (5)2.953 (5)140 (6)
N—H1···O40.84 (7)2.24 (3)2.655 (6)111 (2)
N—H1···O60.84 (7)2.22 (3)2.614 (5)109 (2)
N—H1···O80.84 (7)2.19 (3)2.599 (5)110 (2)
Symmetry codes: (iii) x+1, y, z; (iv) x+1, y+2, z+1; (v) x, y1, z; (vi) x+1, y+1, z+1; (vii) x+1/2, y+3/2, z+1/2.
 

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