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One-dimensional uranium(VI) coordination polymers with pyridinecarboxylate ligands
Polyhedron 113 (2016) 88–95
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One-dimensional uranium(VI) coordination polymers with pyridinecarboxylate ligands Nicholas D. Shepherd a, Yingjie Zhang a,⇑, Inna Karatchevtseva a, Jason R. Price b, Linggen Kong a, Nicholas Scales a, Gregory R. Lumpkin a a b
Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia
a r t i c l e
i n f o
Article history: Received 3 March 2016 Accepted 18 April 2016 Available online 22 April 2016 Keywords: Uranium(VI) Coordination polymer Picolinate Isonicotinate Hydrolysis
a b s t r a c t A method to produce picolinate ligand in situ under hydrothermal conditions has been used to synthesize four uranyl hydroxyl, oxo- and oxohydroxyl picolinato complexes. (UO2)(OH)(Pic) (1) (HPic = picolinic acid) contains 7-fold coordinated uranyl hydroxyl dimers linked through l2-bridging Pic ligands forming a one-dimensional (1D) polymer. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2) consists of 7-fold coordinated uranyl oxohydroxyl trinuclear units linked through both l2- and l3-Pic ligands forming a 1D polymer. (NH4)[(UO2)2(O)2(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked through oxo- and l3-Pic ligands forming a 1D polymer. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]H2O (4) (HINT = isonicotinic acid) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands forming a 1D polymer. All four polymers are thermal robust to 350 °C. Raman spectroscopy confirmed the presence of uranyl ion and Pic ligand. In addition, red enhanced fluorescence emissions have been observed for both 1 and 4. The synthesis method, with the advantage of controlling uranyl hydrolysis and generating ligand in situ, provides a more reliable way to make new coordination polymers of carboxylate ligands with various uranyl hydrolysis species. Crown Copyright Ó 2016 Published by Elsevier Ltd. All rights reserved.
1. Introduction The knowledge on the formation of actinide oxo-, hydroxyl and oxohydroxyl complexes is important as they play a key role in governing the migration of actinides in the geological environment [1]. In specific, uranyl complexes are generally soluble and are the major species involved in the migration processes and the formation of uranyl oxohydroxyl complexes is likely to have a high impact on uranium mobility in the natural environment [2]. It is well understood that uranyl ions encounter hydrolysis reactions even in acidic solutions with pH 3 [3]. Oligometric species become more prevalent at solution pH over 4.5 [4]. Several hydrolyzed solution species, such as dimers linked through two hydroxyl groups and trimers sharing one oxo-group, have been identified by means of spectroscopic techniques, e.g. UV–Vis, IR, EXAFS as well as DFT simulations [5,6]. It has also been revealed that several uranyl species can be present at a given set of conditions, which presents a challenge in the preparation of uranyl hydrolysis phases in a more reproducible way [7]. However, it does provide a unique ⇑ Corresponding author. E-mail address: [email protected] (Y. Zhang). URL: http://www.ansto.gov.au (Y. Zhang). http://dx.doi.org/10.1016/j.poly.2016.04.028 0277-5387/Crown Copyright Ó 2016 Published by Elsevier Ltd. All rights reserved.
opportunity to access and systematically study a variety of extended solid state structures if a more reliable method can be developed. In the solid state, various small hydroxyl and oxohydroxyl uranyl clusters stabilized by various organic ligands have been reported [8]. In addition, several polymeric structures of carboxylate ligands with uranyl hydroxyl or oxohydroxyl species have been structurally characterized [9,10]. These polymers are mainly polycarboxylato or pyridine-based carboxylato complexes containing uranyl hydrolysis species prepared hydrothermally in aqueous solutions with low pHs (<4). More details on solution and solid state chemistry of actinide hydrates and their hydrolysis and condensation products can be found in a recent review article [11]. As a simple pyridine-based carboxylate ligand, picolinic acid (HPic) has long been used in nuclear waste processing as an organic agent for complexing, degreasing, flocculating, purification and decontamination at nuclear sites [12]. Consequently, it has been co-disposed in nuclear waste and is commonly found in radioactive contaminated land [13]. Thus, it is vital to have a good understanding of its species and compounds with uranyl ion at various pH conditions. Several structural types have been identified in the literature for uranyl picolinate (Pic) complexes, including monomers [14], a trinuclear complex [15], a two
N.D. Shepherd et al. / Polyhedron 113 (2016) 88–95
dimensional (2D) structure [16], a 3D structure [17a] and a 1D polymer with the uranyl hydroxyl dimer as the building unit [17b]. In this work, we aim to further study the possible structures of Pic ligand with uranyl hydroxyl and oxohydroxyl species, explore their photoluminescent properties and develop a reliable method to prepare such phases. Consequently, a different approach has been adopted: the uranyl ion was first coordinated with picolinamide (PA) to avoid severe uranyl ion hydrolysis at pH 5.6 and the designed Pic ligand was then generated in situ under hydrothermal conditions. Such a hydrothermal approach enables us to prepare successfully four different types of uranyl Pic complexes with uranyl hydroxyl, oxo- and oxohydroxyl species. Herein we report the synthesis, spectroscopic characterizations, thermal and photoluminescent properties, and crystal structures of (UO2)(OH)(Pic) (1), (NH4)[(UO2)3(O)2(OH)(Pic)2] (2), (NH4)[(UO2)2(O)2(Pic)] (3) and (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)] H2O (4) (INT = isonicotinate), all with 1D polymeric structures. The preparation of the four complexes is summarized in Scheme 1. The successful preparation of four different types of 1D uranyl hydrolysis polymers with the same organic ligand also provides a good opportunity to further examine and rationalize their formation mechanism by analyzing their uranyl connection topologies as well as comparing their properties, e.g. thermal stability and photoluminescence. 2. Results and discussion 2.1. Structure description and discussion The crystal data and structural refinement details for 1–4 are summarized in Table 1. Selected bond lengths and angles at U polyhedra are listed in Table 2, and the calculated bond valence sum (BVS) [18] at both U and coordinated O atoms are summarized in Table 3. 2.1.1. (UO2)(OH)(Pic) (1) Complex 1 contains uranyl hydroxyl dimers bridged by two hydroxyl groups (Fig. 1a and b) and each coordinated by a l2-(N, O; O0 ) bridging ligand at each side forming a 1D polymeric chain along the a-axis (Fig. 1c). The two hydroxyl groups are 2.589 Å apart from each other with calculated BVS of 1.19 [18]. In the literature, only a few polymeric structures containing multi-uranyl hydroxyl dimers are available [10d,17b]. As the structure of 1 was previously described [17b], its structure has been included purely for comparison whist additional characterizations (SEM/EDS, Raman, TG/DTA and photoluminescence) will be presented in detail. 2.1.2. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2) The structure of 2 is constructed from 7-fold coordinated uranium oxohydroxyl trimers with two oxo- and one hydroxyl groups
Scheme 1. Preparation of complexes 1–4 under hydrothermal conditions.
89
and Pic ligands. There are three crystallographically distinct uranium centers (Fig. 2a and b) in the form of pentagonal bipyramids with uranyl bonds [1.775(10)–1.777(11) Å for U1A@O, 1.785(11)– 1.799(11) Å for U1B@O and 1.790(10)–1.830(10) Å for U1C@O] in apical positions. In the equatorial plane of U1A, there are two oxo-oxygen (OOXO) atoms, one hydroxyl (OOH), one carboxylate oxygen (OCOO) and one nitrogen atoms from a ligand [2.197(10)– 2.277(11) Å for U-OOXO, 2.322(10) Å for U-OOH, 2.582(10) Å for U-OL and 2.571(13) Å for U-NL]. U1C has a similar coordination environment in the equatorial plane as U1A, with two OOXO atoms, two OCOO and one nitrogen atoms from the coordinated ligands [2.215(10)–2.219(11) Å for U-OOXO, 2.489(10)–2.519(10) Å for U-OL and 2.609(13) Å for U-NL]. U1B has a different coordination environment in its equatorial plane with two OOXO atoms, one OOH and two OCOO atoms from the bridging ligands [2.247(11)– 2.261(11) Å for U1B-OOXO, 2.329(10) Å for U1B-OOH and 2.547 (11)–2.601(11) Å for U1B-OL]. The U-U distances are ranging from 3.7057(11)–3.9000(10) Å for U1A-U1B, 3.9658(11) Å for U1B-U1C and 3.6297(11) Å for U1C-U1A, respectively. Both O3 and O4 are l3-oxo-atoms linking three uranium centers with calculated BVS of 2.17 (O3) and 1.98 (O4) while O5 is a l2-hydroxyl group linking two uranium centers with calculated BVS of 1.22 [18]. The trinuclear uranyl units connect together through sharing oxo-, hydroxyl groups and l2-bridging Pic ligands forming a 1D infinite ribbon-style structure (Fig. 2c). 2.1.3. (NH4)[(UO2)2(O)2(Pic)] (3) The structure of 3 is constructed from 7-fold coordinated uranium oxo-dimers with two OOXO and Pic ligands. Two crystallographically distinct uranium centers (Fig. 3a and b) are in the form of pentagonal bipyramids with uranyl bonds [1.833(7) Å for U1@O and 1.802(7) Å for U2@O] in apical positions. In the equatorial plane of U1, there are four OOXO atoms and one OCOO from a ligand [2.195(8)–2.446(9) Å for U-OOXO and 2.535(8) Å for U-OCOO]. U2 has a different coordination environment in the equatorial plane with two OOXO, two OCOO and one nitrogen from the coordinated ligands [2.159(8)–2.193(9) Å for U-OOXO, 2.511(8)–2.718(8) Å for U-OCOO and 2.630(9) Å for U-NL]. The U1–U2 distance is 3.991 (9) Å. Both O3 and O6 are l3-oxo-atoms linking three uranium centers with calculated BVS [18] of 2.24 (O3) and 1.96 (O6). The dinuclear uranyl units connect together through sharing oxo groups and l3-bridging Pic ligands forming a 1D infinite ribbon-style structure (Fig. 3c). 2.1.4. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]H2O (4) The structure of 4 is constructed from 7-fold coordinated uranium oxohydroxyl tetranuclear unit with two OOXO, two OOH, two Pic and one INT ligands. The four crystallographically distinct uranium centers (Fig. 4a and b) are all in the form of pentagonal bipyramids with uranyl bonds [1.788(14)–1.827(14) Å for U1@O, 1.800(14) Å for U2@O, 1.771(13)–1.793(14) Å for U3@O and 1.814(13)–1.821(13) Å for U4@O] in apical positions. In the equatorial plane of U1, there are one OOXO, one OOH, two OCOO and one nitrogen atoms [2.207(11) Å for U-OOXO, 2.423(11) Å for UOOH, 2.342(11)–2.458(11) Å for U-OCOO and 2.643(14) Å for U-NL]. In the equatorial plane of U2, there are two OOXO, two OOH and one OCOO atoms [2.226(11)–2.381(11) Å for U2-OOXO, 2.363(11)– 2.496(10) Å for U2-OOH and 2.376(12) Å for U2-OL]. In the equatorial plane of U3, there are one OOXO, two OOH and two OCOO atoms [2.222(11) Å for U3-OOXO, 2.336(11)–2.452(11) Å for U3-OOH, and 2.513(11)–2.586(12) Å for U3-OCOO]. In the equatorial plane of U4, there are two OOXO, two OCOO and one nitrogen atoms [2.183 (11)–2.226(11) Å for U4-OOXO, 2.408(12)–2.538(12) Å for for U4OCOO and 2.612(14) Å for U4-NL]. The U–U distances are ranging from 3.8068(11) Å for U1–U2, 3.9850(10) Å for U1–U3, 3.7814 (11) Å for U2–U3, 3.9719(11) Å for U3–U4, 3.6999(10) Å for
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Table 1 Crystal data and refinement details for complexes 1–4.
a b
Complex
1
2
3
4
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z/dcalcd (g cm3) l (mm1)/F(0 0 0) Reflections/Independent reflections Rint/parameters refined Goodness-of-fit (GOF) Final R1 [I > 2r(I)]a Final wR2 [I > 2r(I)]b
C6H4NO5U 408.13 triclinic P1
C12H8N3O13U3 1120.34 monoclinic P21/c 7.1900(14) 20.007(4) 13.807(3) 90 93.28(3) 90 1982.9(7) 4/3.753 11.264/1940 18642/2496 0.0541/268 1.051 0.0400 0.0987
C6H4N2O8U2 708.17 orthorhombic Pnma 6.7910(14) 6.9550(14) 24.201(5) 90 90 90 1143.0(4) 4/4.115 13.009/1208 20665/1653 0.0380/66 1.180 0.0339 0.0748
C18H12N4O19U4 1540.44 monoclinic P21/n 7.3200(15) 16.272(3) 23.960(5) 90 95.84(3) 90 2839.1(10) 4/3.604 10.500/2672 35699/5396 0.0985/395 1.036 0.0802 0.2111
6.2810(13) 7.9570(16) 8.3540(17) 79.54(3) 87.77(3) 79.08(3) 403.14(15) 2/3.362 9.257/358 7495/1940 0.0905/95 1.133 0.0260 0.0702
R1 = RkFo| |Fck/|Fo|. wR2 = {R[w(F2o F2c )2]/R[w(F2o)2]}1/2.
Table 2 Selected bond lengths and angles for 1–4. 1 U1
2 U1A
U1B
U1C
3 U1
U2
4 U1
U2
U3
U4
Table 3 Calculated Bond Valence Sums (BVS) for 1–4.
U1–O1 O@U@O U1–O4 U1–O50
1.771(5) 174.5(2)° 2.393(3) 2.340(4)
U1–O2 U1–O3 U1–O5 U1–N1
1.789(5) 2.439(3) 2.298(4) 2.604(5)
U1A–O1A U1A–O2 U1A–O4 U1A–N1A U1B–O1B U1B–O2 U1B–O4 U1B–O7 U1C–O1C U1C–O1 U1C–O4 U1C–N1C
1.775(10) 2.582(10) 2.322(10) 2.571(13) 1.799(11) 2.601(11) 2.261(11) 2.547(11) 1.830(10) 2.489(10) 2.219(11) 2.609(13)
U1A–O2A U1A–O3 U1A–O5 O@U@O U1B–O2B U1B–O3 U1B–O5 O@U@O U1C–O2C U1C–O3 U1C–O7 O@U@O
1.777(11) 2.197(10) 2.277(11) 173.7(5)° 1.785(11) 2.247(11) 2.329(10) 178.7(5)° 1.790(10) 2.215(10) 2.519(10) 175.7(5)°
U1–O1 U1–O30 U–O6 O@U@O U2–O2 U2–O4 U2–O6 O@U@O
1.833(7) 2.257(8) 2.210(9) 175.2(4)° 1.802(7) 2.511(8) 2.193(9) 171.6(4)°
U1–O3 U1–O5 U–O60
2.195(8) 2.535(8) 2.446(9)
U2–O3 U2–O5 U2–N1
2.159(8) 2.718(8) 2.630(9)
U1–O1 U1–O9 U1–O14 U1–N1 U2–O3 U2–O11 U2–O15 U2–O18 U3–O5 U3–O9 U3–O13 U3–O18 U4–O7 U4–O12 U4–O17 U4–N2
1.827(14) 2.458(11) 2.342(11) 2.643(14) 1.800(14) 2.376(12) 2.381(11) 2.226(11) 1.793(14) 2.513(11) 2.452(11) 2.222(11) 1.814(13) 2.538(12) 2.408(12) 2.612(14)
U1–O2 U1–O13 U1–O15 O@U@O U2–O4 U2–O13 U2–O16 O@U@O U3–O6 U3–O12 U3–O16 O@U@O U4–O8 U4–O15 U4–O18 O@U@O
1.788(14) 2.423(11) 2.207(11) 176.6(6)° 1.800(14) 2.496(10) 2.363(11) 175.6(5)° 1.771(13) 2.586(12) 2.336(11) 177.3(5)° 1.821(13) 2.226(11) 2.183(11) 175.1(5)°
U2–U4, respectively. Both O15 and O18 are l3-oxo-atoms linking three uranium centers with calculated BVS of 1.98 for O15 and 2.21 for O18 while O13 (l3-) and O16 (l2-) are hydroxyl groups
1 U1
5.89
O1
1.69
O2
1.66
O5
1.19
2 U1A O2A O2C O5
6.04 1.71 1.62 1.22
U1B O1B O2 O7
5.98 1.63 0.72 0.80
U1C O2B O3
5.96 1.69 2.17
O1A O1C O4
1.61 1.70 1.98
3 U1 O3
6.07 2.24
U2 O6
6.03 1.96
O1
1.53
O2
1.62
4 U1 O1 O5 O13
5.78 1.55 1.64 1.37
U2 O2 O6 O15
5.96 1.65 1.73 1.98
U3 O3 O7 O16
5.89 1.61 1.57 1.12
U4 O4 O8 O18
5.86 1.61 1.56 2.21
linking uranium centers with calculated BVS of 1.37 (O13) and 1.12 (O16) [18]. The tetranuclear uranyl units connect together through sharing oxo-, hydroxyl groups with l2- and l3-Pic, and l2-INT ligands forming a 1D infinite structure (Fig. 4c). 2.1.5. Polymer formation and ribbon topologies Complex 2 is a uranyl oxohydroxyl Pic complex constructed with the uranyl oxohydroxyl trimers and both l2- and l3-Pic ligands forming a 1D ribbon-style polymeric structure. Contrary to 1 which can be prepared by several synthesis routes in a much wider solution pHs [17b], the formation of 2 requires relatively higher stabilized solution pH. The measured higher pHf (5.40) for 2 compared to pHf (4.01) for 1 would be the main reason for favoring the formation of 2. In the literature, two main types of 1D ribbons based on trinuclear uranyl units have been reported with mono-/poly-carboxylate ligands as well as pyridine dicarboxylate ligands [7,10,19,20]. However, these complexes are mainly hydroxyl-rich with more hydroxyl groups than oxo-groups. In contrast, 2 has more oxo-groups than hydroxyl groups. It is also of interest to compare their ribbon topologies. Fig. 5 shows the two ribbon topologies published together with the ribbon topology of 2. Clearly, the ribbon in 2 has a distinct connection topology as a result of in-turn coordination by l2- and l3-Pic ligands on both sides of the ribbon. Both 3 (a uranyl oxo-Pic complex) and 4 (a uranyl oxohydroxyl complex) have 1D uranyl polymeric structures. To our knowledge, they possess unique uranyl ribbon topologies (Fig. 6) which have not been identified before.
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Fig. 3. Structure of 3: ball-stick (a) and polyhedral (b) views of the dinuclear uranyl oxo-building unit and the 1D uranyl oxohydroxyl polymer (c) with l3-Pic ligands.
Fig. 1. Structure of 1: ball-stick (a) and polyhedral (b) views of the uranyl hydroxyl dimer building unit and a 1D polymeric chain (c) formed by linking the dimers through l2-bridging ligands.
Fig. 4. Structure of 4: ball-stick (a) and polyhedral (b) views of the tetranuclear uranyl oxohydroxyl building unit and the 1D uranyl oxohydroxyl polymer (c) with both Pic and INT bridging ligands.
Fig. 2. Structure of 2: ball-stick (a) and polyhedral (b) views of the trinuclear uranyl oxohydroxyl building unit and the 1D ribbon-type uranyl oxohydroxyl polymer (c) with both l2- and l3-Pic ligands.
2.1.6. Ligand coordination modes Several ligand coordination modes have been identified in complexes 1–4 including a l2-(N, O; O’) mode of Pic in 1 (Fig. 7a), a l3(N, O; O; O0 ) mode of Pic in 2, 3 and 4 (Fig. 7b), a l2-(N, O; O) mode of Pic in 2 and 4 (Fig. 7c) and a l2-(O; O0 ) mode of INT in 4 (Fig. 7d). 2.1.7. Hydrogen bonding and uranyl-cation interactions Complexes 2–4 all have (NH4)+ cations in the crystal lattice for charge balancing. Extensive uranyl-cation interactions via hydrogen bonding between (NH4)+ cations and O-yl atoms in 2–4 link the ribbons into closely packed 2D stacking structures (Fig. S3). The uranyl-cation interactions also influence the linearity of the uranyl unit with uranyl unit bending from 175.2(4) for O@U1@O
to 171.6(4)° for O@U2@O in 3, significantly deviated from the ideal 180°. 2.2. Vibrational modes Raman spectroscopy has long been used to study and fingerprint some uranium natural minerals and has the potential to differentiate various uranyl oxo- and hydroxyl mineral species [21]. Raman spectra of both 1 and 2 are shown in Fig. 8. The Raman assignments are based on some relevant literature data [22]. Both spectra look quite similar with the main dominating feature being the strong and sharp band at 845 cm1 for 1 and 820 cm1 for 2 due to the symmetric stretching vibration of (UO2)2+ with calculated U@O bond length of 1.767(9) Å for 1 and 1.791(9) Å for 2 [23], consistent with the values [1.771(5)–1.789(5) Å for U@O bonds in 1] and [1.775(10)–1.830(10) Å for U@O bonds in 2] obtained from the single crystal data. Other similar spectral features include: (1) the asymmetric and symmetric stretching vibrations of the carboxylate COO groups coordinated to U atoms are
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Fig. 5. A comparison of 1D ribbon-type structures built with pentagonal bipyramidal uranyl trinuclear units: (a) and (b) two ribbon topologies reported previously [7,10,19,20], and (c) a new ribbon connection topology found in 2.
Fig. 7. Coordination modes of Pic and INT: l2-mode of Pic in 1 (a), l3-mode of Pic in 2, 3 and 4 (b), l2-mode of Pic in 2 and 4 (c) and l2-mode of INT in 4.
Fig. 6. The unique uranyl ribbon topologies for 3 (a) and 4 (b).
found, respectively, at 1605 and 1412 cm1 for 1, and at 1597 and 1378 cm1 for 2; (2) two weak-to-medium intensity bands located around 1575 and 1550 cm1 for both 1 and 2 have been assigned to ring stretching vibrations (m (CC)arom), while the region 1480– 1443 cm1 is a combination of C–H deformation modes, and CO and CNC stretching modes [22]; (3) several weak Raman bands in the region 1160–1156 cm1 are due to in-plane d (CHarom) deformation; (4) the bands at 1050–1048 cm1 have been assigned predominantly to d (UOH) deformation mode; (5) Raman bands at 1020–1017 cm1 are due to the ring stretching vibration, m (CC)arom; (6) the weak band at 850 cm1 for 2 is due to out-of-plane d (CHarom) deformation vibration; (7) carboxylate COO in-plane and out-of-plane deformation modes are observed at 699 and 424 cm1, respectively, and the weak peak at 640 cm1 is due to ring deformations; (8) m (UOequatorial) vibrations are found at 367–351 cm1; (9) d (UO2)2+ and d (UOeq) deformation vibrations are at 290 and 245 cm1. Finally, there are several weak and broad bands at 592, 546 and 489 cm1 for 2, which have been assigned to the m (U3O) bridge elongation [24,25]. Raman spectra of 3 and 4 (Fig. S4) are quite similar to those of 1 and 2. Their detailed Raman band assignments are summarized in Table S1 together with those for 1 and 2.
Fig. 8. Raman spectra (2000–100 cm1) of 1 (a) and 2 (b).
2.3. Thermal stabilities All 1D polymers are thermally stable up to 350 °C and have very similar thermal decomposition patterns. Uranium oxide phase transitions at high temperature in air have been well documented [26]. U3O8 is the main oxide phase present after heating uranyl organic complexes over 710 °C, which has been observed previously by both DSC/TG and powder X-ray diffraction studies [26]. The DTA curve of 1 (Fig. S5a) has a large exotherm at 420 °C corresponding to the decomposition of Pic ligands and hydroxyl groups associated with a weight loss of 32.5% (calc. 32.0%) and a small endotherm at 730 °C corresponding to the phase transition to U3O8, with residue 68.5% observed (calc. 68.6%). The DTA curve of 2 (Fig. S5b) has a large exotherm at 430 °C corresponding to the decomposition of Pic ligands and NH+4 cations with a weight loss of 23.6% (calc. 23.5%) and a small endotherm at 730 °C corresponding to the phase transition to U3O8, with residue 76.0% observed (calc. 75.1%). The DTA curve of 3 (Fig. S6a) has a small
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350 °C and then lose organic ligands followed by further decomposition to form U3O8. Ligand enhanced red fluorescence emissions have been observed for 1, 3 and 4. Raman spectroscopy confirmed the presence of both uranyl ion and Pic ligand in 1–4. The overall chemical reactions for the formation of these 1D polymers are proposed and discussed. The variety of uranyl hydrolysis building units identified in this work highlights the complexity of the system as well as the potential to further explore the area. The synthesis method, with both advantages of controlling uranyl hydrolysis and generating ligand in situ, opens a new way to make polymeric phases containing various uranyl hydrolysis species. 4. Experimental 4.1. Synthesis
Fig. 9. Fluorescence emission spectra of 1–4 measured using their maximum excitation wavelengths.
exotherm at 420 °C and a large exotherm at 480 °C corresponding to the decomposition of NH+4 cations and Pic ligands, with a weight loss of 20.0% (calc. 21.1%) and a further phase transition to U3O8. Similarly, the DTA curve of 4 (Fig. S6b) has a large exotherm at 450 °C corresponding to the decomposition of Pic ligands with a weight loss of 27.9% (calc. 27.5%) and further phase transition to U3O8. 2.4. Photoluminescence The fluorescence emission spectra for 1–4 were collected in powder form at ambient temperature using their maximum excitation wavelengths. The fluorescence emission spectra of 2 and 3 (Fig. 9) are similar and have up to six emission bands in the range of 480 to 585 nm, characteristic of uranyl compounds with typical bands corresponding to the electronic transitions S11 ? S00 and S10 ? S0m (m = 0–4) of the uranyl ion [27]. The most intense bands are located at 518 nm for 2 and 515 nm for 3, compared to 510 nm observed for uranyl nitrate hexahydrates (UNH) [27,28]. However, both emission bands of S10 ? S02 and S10 ? S03 are slightly enhanced in 3. The emission spectra of 1 and 4 (Fig. 9) are very similar in broad feature with the most intense bands at 545 nm for 1 and 548 nm for 4, respectively, corresponding to enhanced S10 ? S02 and S10 ? S03 bands. The slightly red-shift effect for some uranyl carboxylate compounds have been discussed and attributed to the presence of pentagonal bipyramidal uranium centers [27,28]. However, further red-shift and broad nature in the cases of 1 and 4 can be attributed to the combined result of the uranium local coordination environment and the ligand effect. 3. Conclusions The aim of this work was to further explore the structural domain of uranyl picolinato complexes containing various uranyl hydrolysis species. Consequently, four uranyl hydroxyl and oxohydroxyl 1D polymers with Pic ligand have been synthesised via a unique hydrothermal approach. (UO2)(OH)(Pic) (1) is built with uranyl hydroxyl dimer as the building unit and Pic ligands. (NH4) [(UO2)3(O)2(OH)(Pic)2] (2) is built with uranyl oxohydroxyl trinuclear units and both l2- and l3-bridging Pic ligands. (NH4) [(UO2)2(O)2(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked by l3-Pic ligands. (NH4)[(UO2)4(O)2 (OH)2(Pic)2 (INT)]H2O (4) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands. All four 1D polymers are thermal stable to at least
Caution! Depleted uranium (238U) is radioactive and its compounds should be handled with care within proper radiologically surveyed facilities. Strategy: A previous study [29] demonstrated that the uranyl ion can be coordinated with picolinamide (PA) to give a stable uranyl bis(PA) species with a solution pH 5.6. This solution was used in the current study, with various amounts of NaHCO3 added to generate the designed Pic ligand in situ under hydrothermal conditions. (UO2)(OH)(Pic) (1). Uranyl nitrate (1.0 mL, 0.5 M), picolinamide (2.0 mL, 0.5 M), NaHCO3 (0.5 mL, 0.25 M) solutions and 5.0 mL deionized (DI) water were added in a 120 mL Teflon container, sealed in a stainless steel pressure Parr vessel and left in a 190 °C oven for 48 h. A yellow crystalline product of 1 was formed after slow cooling (5 °C/h) to room temperature in a light yellow solution (pHf = 4.0) with 70% yield (72 mg) based on U content. C6H5NO5U (FW = 409.13): calc. C, 17.61; H, 1.23; N, 3.42; found: C, 17.58; H, 1.28; N, 3.35. Complex 1 was previously prepared with initial solution pH ranging from 1.60 to 4.14, and the structure was described [17b]. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2). Similarly to 1, complex 2 was synthesized with uranyl nitrate (1.0 mL, 0.5 M), picolinamide (2 mL, 0.5 M), NaHCO3 (1.0 mL, 0.25 M) solutions and 5.0 mL of DI water hydrothermally. A yellow crystalline product of 2 was formed in a light yellow solution (pHf = 5.4) with over 80% yield (151 mg). C12H13N3O13U3 (FW = 1121.32): calc. C, 12.85; H, 1.17; N, 3.75. Found: C, 12.76; H, 1.28; N, 3.82%. (NH4)[(UO2)2(O)2(Pic)] (3). Complex 3 was prepared in the similar way as for 2 but with double quantity of NaHCO3 and crystallized in a light yellow solution (pHf = 5.8) with 87% yield (155 mg). C6H8N2O8U2 (FW = 712.19): calc. C, 10.12; H, 1.13; N, 3.93. Found: C, 10.08; H, 1.22; N, 3.87%. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]H2O (4). Similar to the preparation of complex 3, complex 4 was prepared with further addition of 1.0 mmol isonicotinic acid and it was crystallized in a light yellow solution (pHf = 5.6) with over 70% yield (137 mg). C18H20N4O19U4 (FW = 1548.47): calc. C, 13.96; H, 1.30; N, 3.62. Found: C, 13.94; H, 1.28; N, 3.59%. The examination of the products using electron microscope reveals that they are all crystalline products. Elemental analysis, SEM-EDS, TG/DTA, photoluminescence, Raman spectroscopy and single crystal X-ray diffraction have been used to further study the four phases. SEM-EDS analysis confirmed the presence of C, N, O and U in 1–4 (Figs. S1 and S2). 4.2. Characterization 4.2.1. Elemental analyses Elemental analyses were carried out using a Perkin-Elmer 2400 CHN elemental analyzer.
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4.2.2. Scanning Electron Microscope and Electron Dispersive Spectroscopy (SEM-EDS) A Zeiss Ultra Plus SEM (Carl Zeiss NTS GmbH, Oberkochen, Germany) operating with an accelerating voltage of 20 kV was used to probe the key elements present. 4.2.3. Raman spectroscopy Raman spectra were recorded on a Perkin Elmer Raman station 400 with Micro300 Microscope and excitation laser 785 nm in the range 2000–100 cm1. 4.2.4. Photoluminescence Fluorescence emission spectra were measured using a Varian Cary Eclipse Fluorescence Spectrometer. 4.2.5. Thermogravimetric and differential thermal analysis (TG/DTA) TG/DTA was made on a SEIKO 6300 Thermal Analyzer from room temperature to 1000 °C with a heating rate of 10 °C min1 and an air flow rate of 300 cm3 min1. 4.3. Single crystal X-ray diffraction The Single-crystal X-ray data for 1–4 were collected at 100(2) K on the MX2 beamline at the Australian Synchrotron with Silicon Double Crystal radiation (k = 0.72930 Å). All data were collected using BlueIce software [30]. An empirical absorption correction was applied to the data using SADABS [31]. Cell refinements and data reductions were carried out using XDS software [32]. The structures were solved by direct methods using SHELXT [33] and the full-matrix least-squares refinements were carried out using SHELXL [34] via Olex2 interface [35]. Complex 2 has large solvent accessible voids in the crystal lattice. However no electron density could be located. The one circle goniometer geometry of data collections at MX2 beamline offers less opportunity for applying multi-scan absorption correction as is possible with the data collections on a four circle goniometer. Consequently, ripples around U atoms are often present due to ineffective absorption correction. In addition, the data completeness is relatively low for crystals in low symmetry space groups, especially for 1 in triclinic space group. Acknowledgements We would like to acknowledge Dr M. Bhadbhade for helpful discussion on crystal structure refinements. The crystallographic data for 1–4 were collected on the MX2 beamline at the Australian Synchrotron, Victoria, Australia. Appendix A. Supplementary data CCDC 998972 (1), 998973 (2), 1423618 (3) and 1423619 (4) contains the supplementary crystallographic data for . These data can be obtained free of charge via http://www.ccdc.cam.ac. uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2016.04.028. References [1] G.R. Choppin, J. Radioanal. Nucl. Chem. 273 (3) (2007) 695. [2] (a) P. Crançon, J. van der Lee, Radiochim. Acta 91 (2003) 673; ˇ ejka, G.R. Lumpkin, T.T. Tran, I. Aharonovich, J.R. Price, N. (b) Y. Zhang, J. C Scales, K. Lu, New J. Chem. (2016), http://dx.doi.org/10.1039/C5NJ03055B. [3] F. Quilès, C. Nguyen-Trung, C. Carteret, B. Humbert, Inorg. Chem. 50 (7) (2011) 2811.
[4] I. Grenthe, J. Fuger, R.J.M. Konings, R.J. Lemire, C. Nguyen-Trun, H. Wanner, in: H. Wanner, I. Forest (Eds.), Chemical Thermodynamics of Uranium, Organisation for Economic Corporation and Development, Issy-lesMoulineau, France, 2004. [5] S. Tsushima, A. Rossberg, A. Ikeda, K. Müller, A.C. Scheinost, Inorg. Chem. 46 (25) (2007) 10819. [6] F. Quilès, A. Burneau, Vib. Spectrosc. 23 (2) (2000) 231. [7] M.B. Andrews, C.L. Cahill, Chem. Rev. 113 (2) (2013) 1121. [8] (a) Z.L. Liao, G.D. Li, X.A. Wei, Y. Yu, J.S. Chen, Eur. J. Inorg. Chem. (2010) 3780; (b) Z.T. Yu, G.H. Li, Y.S. Jiang, J.J. Xu, J.S. Chen, Dalton Trans. (2003) 4219; (c) P. Thuéry, M. Nierlich, B. Souley, Z. Asfari, J. Vicens, J. Chem. Soc., Dalton Trans. (1999) 2589; (d) P. Thuéry, B. Masci, Supramol. Chem. 15 (2003) 95. [9] (a) S. Dalai, M. Bera, A. Rana, D.S. Chowdhuri, E. Zangrando, Inorg. Chim. Acta 363 (13) (2010) 3407; (b) P. Thuéry, Eur. J. Inorg. Chem. 26 (2013) 4563; c) W. Zhang, J. Zhao, J. Mol. Struct. 789 (2006) 177. [10] (a) A.T. Kerr, C.L. Cahill, Cryst. Growth Des. 11 (12) (2011) 5634; (b) I. Mihalcea, N. Henry, T. Loiseau, Cryst. Growth Des. 11 (2011) 1940; (c) I. Mihalcea, N. Henry, C. Volkringer, T. Loiseau, Cryst. Growth Des. 12 (2012) 526; (d) P. Thuéry, Cryst. Growth Des. 11 (2011) 3282; (e) Y.-S. Jiang, Z.-T. Yu, Z.-L. Liao, G.-H. Li, J.-S. Chen, Polyhedron 25 (6) (2006) 1359; (f) I.A. Charushnikova, N.N. Krot, Z.A. Starikova, Radiokhimiya (Russ.) 46 (2004) 396. [11] K.E. Knope, L. Soderholm, Chem. Rev. 113 (2013) 944. [12] (a) P.A. Baisden, G.R. Choppin, Nuclear Waste Managements and the Nuclear Fuel Cycle, Radiochemistry and Nuclear Chemistry, Encyclopedia of Life Support Systems, Oxford, 2007; (b) R.G. Riley, J.M. Zachara, Chemical Contaminants on DOE Lands and Selection of Contaminant Mixtures for Subsurface Science Research, Pacific Northwest Lab., Richland, WA (United States), 1992, p. 77. [13] C.V. McIsaac, D.W. Akers, J.W. McConnell, N. Morcos, Leach Studies on Cementsolidified Ion Exchange Resins from Decontamination Processes at Operating Nuclear Power Stations, Idaho National Engineering Laboratory, Idaho Falls, Idaho, USA, 1992, p. 17. [14] (a) E.V. Grechishnikova, E.V. Peresypkina, A.V. Virovets, Yu.N. Mikhailov, L.B. Serezhkina, Koord. Khim. (Russ.) 33 (2007) 468; (b) V.I. Mishkevich, M.S. Grigoriev, A.M. Fedosseev, P. Moisy, Acta Crystallogr., Sect. E 68 (2012) m1243; (c) W. Aas, M.H. Johansson, Acta Chem. Scand. 53 (1999) 581. [15] P.R. Silverwood, D. Collison, F.R. Livens, R.L. Beddoes, R.J. Taylor, J. Alloys Compd. 271 (1998) 180. [16] P. Thuéry, Inorg. Chem. Commun. 12 (2009) 800. [17] (a) R.C. Severance, S.A. Vaughn, M.D. Smith, H.-C. Zur Loye, Solid State Sci. 13 (2011) 1344; (b) M.B. Andrews, C.L. Cahill, CrystEngComm 13 (2011) 7068. [18] (a) I.D. Brown, Chem. Rev. 109 (2009) 6858; (b) F.C. Hawthorne, Phys. Chem. Miner. 39 (2012) 841; (c) P.C. Burns, R.C. Ewing, F.C. Hawthorne, Can. Mineral. 35 (1997) 1551. [19] P. Thuéry, CrystEngComm 14 (2012) 3363. [20] T. Loiseau, I. Mihalcea, N. Henry, C. Volkringer, Coord. Chem. Rev. 266–267 (2013) 69. [21] R.L. Frost, J. Cejka, M.L. Weier, J. Raman Spectrosc. 38 (2007) 460. [22] (a) G. Socrates, Infrared and Raman Characteristic Group Frequencies: Tables and Charts, third ed., John Wiley & Sons Hoboken, New York, 2004; (b) Y. Zhang, J.R. Price, I. Karatchevtseva, K. Lu, B. Yoon, F. Kadi, G.R. Lumpkin, F. Li, Polyhedron 91 (2015) 98; (c) Y. Zhang, M. Bhadbhade, I. Karatchevtseva, J. Gao, J.R. Price, G.R. Lumpkin, Eur. J. Inorg. Chem. (2013) 6170; (d) Y. Zhang, J. Cˇejka, I. Karatchevseva, M. Qin, L. Kong, K. Short, S.C. Middleburg, G.R. Lumpkin, J. Nucl. Mater. 446 (2014) 68; (e) Y. Zhang, I. Karatchevtseva, M. Qin, S.C. Middleburgh, G.R. Lumpkin, J. Nucl. Mater. 437 (2013) 149; (f) Y. Zhang, I. Karatchevtseva, M. Bhadbhade, T.T. Tran, I. Aharonovich, D.J. Fanna, N.D. Shepherd, K. Lu, F. Li, G.R. Lumpkin, J. Solid State Chem. 234 (2016) 22. [23] J.R. Bartlett, R.P. Cooney, J. Mol. Struct. 193 (1989) 295. [24] P.K. Sinha, M. Bolboaca, S. Schlücker, J. Popp, W. Kiefer, J. Raman Spectrosc. 34 (2003) 276. [25] A.T. Fiedler, X. Shan, M.P. Mehn, J. Kaizer, S. Torelli, J.R. Frisch, M. Kodera, L. Que Jr., J. Phys. Chem. A 112 (50) (2008) 13037. [26] (a) E. Gómez-Rebollo, P. Herrero, R.M. Rojas, J. Nucl. Mater. 245 (1997) 161; (b) K. Sudo, A. Okawa, Bull. Res. 16 (1) (1960) 85. Institute of Mineral Dressing and Metallurgy, Tohoku University; ˇ ejka, J. Sejkora, Z. Mrázek, Z. Urbanec, T. Jarchovsky´, Neues Jahrbuch für (c) J. C Mineralogie Abhandlungen 170 (1996) 155. [27] (a) Y. Zhang, M. Bhadbhade, I. Karatchevtseva, J.R. Price, H. Liu, Z. Zhang, ˇ ejka, L. Kong, K. Lu, G.R. Lumpkin, J. Solid State Chem. 226 (2015) J. C 42; (b) Y. Zhang, I. Karatchevtseva, J.R. Price, I. Aharonovich, F. Kadi, G.R. Lumpkin, F. Li, RSC Adv. 5 (2015) 33249. [28] (a) I. Mihalcea, N. Henry, T. Loiseau, Eur. J. Inorg. Chem. (2014) 1322; (b) Y. Zhang, J.K. Clegg, K. Lu, G.R. Lumpkin, T.T. Tran, I. Aharonovich, N. Scales, F. Li, Chem. Select 1 (1) (2016) 7.
N.D. Shepherd et al. / Polyhedron 113 (2016) 88–95 [29] Y. Zhang, M. Bhadbhade, J. Gao, I. Karatchevseva, J.R. Price, G.R. Lumpkin, Inorg. Chem. Commun. 37 (2013) 219. [30] T.M. McPhillips, S.E. McPhillips, H.J. Chiu, A.E. Cohen, A.M. Deacon, P.J. Ellis, E. Garman, A. Gonzalez, N.K. Sauter, R.P. Phizackerley, S.M. Soltis, P. Kuhn, J. Synchrotron Radiat. 9 (2002) 401. [31] W. Kabsch, J. Appl. Crystallogr. 26 (1993) 795. [32] SADABS: Empirical Absorption and Correction Software, University of Göttingen, 1996–2008.
95
[33] (a) G.M. Sheldrick, Acta Crystallogr., Sect. A 71 (2015) 3; (b) SHELXT-2014, G.M. Sheldrick, University of Göttingen, 2014. [34] (a) G.M. Sheldrick, Acta Crystallogr., Sect. C 71 (2015) 3; (b) SHELXL-2014, G.M. Sheldrick, University of Göttingen, 2014. [35] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl. Crystallogr. 42 (2009) 339.
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Polyhedron journal homepage: www.elsevier.com/locate/poly
One-dimensional uranium(VI) coordination polymers with pyridinecarboxylate ligands Nicholas D. Shepherd a, Yingjie Zhang a,⇑, Inna Karatchevtseva a, Jason R. Price b, Linggen Kong a, Nicholas Scales a, Gregory R. Lumpkin a a b
Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia
a r t i c l e
i n f o
Article history: Received 3 March 2016 Accepted 18 April 2016 Available online 22 April 2016 Keywords: Uranium(VI) Coordination polymer Picolinate Isonicotinate Hydrolysis
a b s t r a c t A method to produce picolinate ligand in situ under hydrothermal conditions has been used to synthesize four uranyl hydroxyl, oxo- and oxohydroxyl picolinato complexes. (UO2)(OH)(Pic) (1) (HPic = picolinic acid) contains 7-fold coordinated uranyl hydroxyl dimers linked through l2-bridging Pic ligands forming a one-dimensional (1D) polymer. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2) consists of 7-fold coordinated uranyl oxohydroxyl trinuclear units linked through both l2- and l3-Pic ligands forming a 1D polymer. (NH4)[(UO2)2(O)2(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked through oxo- and l3-Pic ligands forming a 1D polymer. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]H2O (4) (HINT = isonicotinic acid) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands forming a 1D polymer. All four polymers are thermal robust to 350 °C. Raman spectroscopy confirmed the presence of uranyl ion and Pic ligand. In addition, red enhanced fluorescence emissions have been observed for both 1 and 4. The synthesis method, with the advantage of controlling uranyl hydrolysis and generating ligand in situ, provides a more reliable way to make new coordination polymers of carboxylate ligands with various uranyl hydrolysis species. Crown Copyright Ó 2016 Published by Elsevier Ltd. All rights reserved.
1. Introduction The knowledge on the formation of actinide oxo-, hydroxyl and oxohydroxyl complexes is important as they play a key role in governing the migration of actinides in the geological environment [1]. In specific, uranyl complexes are generally soluble and are the major species involved in the migration processes and the formation of uranyl oxohydroxyl complexes is likely to have a high impact on uranium mobility in the natural environment [2]. It is well understood that uranyl ions encounter hydrolysis reactions even in acidic solutions with pH 3 [3]. Oligometric species become more prevalent at solution pH over 4.5 [4]. Several hydrolyzed solution species, such as dimers linked through two hydroxyl groups and trimers sharing one oxo-group, have been identified by means of spectroscopic techniques, e.g. UV–Vis, IR, EXAFS as well as DFT simulations [5,6]. It has also been revealed that several uranyl species can be present at a given set of conditions, which presents a challenge in the preparation of uranyl hydrolysis phases in a more reproducible way [7]. However, it does provide a unique ⇑ Corresponding author. E-mail address: [email protected] (Y. Zhang). URL: http://www.ansto.gov.au (Y. Zhang). http://dx.doi.org/10.1016/j.poly.2016.04.028 0277-5387/Crown Copyright Ó 2016 Published by Elsevier Ltd. All rights reserved.
opportunity to access and systematically study a variety of extended solid state structures if a more reliable method can be developed. In the solid state, various small hydroxyl and oxohydroxyl uranyl clusters stabilized by various organic ligands have been reported [8]. In addition, several polymeric structures of carboxylate ligands with uranyl hydroxyl or oxohydroxyl species have been structurally characterized [9,10]. These polymers are mainly polycarboxylato or pyridine-based carboxylato complexes containing uranyl hydrolysis species prepared hydrothermally in aqueous solutions with low pHs (<4). More details on solution and solid state chemistry of actinide hydrates and their hydrolysis and condensation products can be found in a recent review article [11]. As a simple pyridine-based carboxylate ligand, picolinic acid (HPic) has long been used in nuclear waste processing as an organic agent for complexing, degreasing, flocculating, purification and decontamination at nuclear sites [12]. Consequently, it has been co-disposed in nuclear waste and is commonly found in radioactive contaminated land [13]. Thus, it is vital to have a good understanding of its species and compounds with uranyl ion at various pH conditions. Several structural types have been identified in the literature for uranyl picolinate (Pic) complexes, including monomers [14], a trinuclear complex [15], a two
N.D. Shepherd et al. / Polyhedron 113 (2016) 88–95
dimensional (2D) structure [16], a 3D structure [17a] and a 1D polymer with the uranyl hydroxyl dimer as the building unit [17b]. In this work, we aim to further study the possible structures of Pic ligand with uranyl hydroxyl and oxohydroxyl species, explore their photoluminescent properties and develop a reliable method to prepare such phases. Consequently, a different approach has been adopted: the uranyl ion was first coordinated with picolinamide (PA) to avoid severe uranyl ion hydrolysis at pH 5.6 and the designed Pic ligand was then generated in situ under hydrothermal conditions. Such a hydrothermal approach enables us to prepare successfully four different types of uranyl Pic complexes with uranyl hydroxyl, oxo- and oxohydroxyl species. Herein we report the synthesis, spectroscopic characterizations, thermal and photoluminescent properties, and crystal structures of (UO2)(OH)(Pic) (1), (NH4)[(UO2)3(O)2(OH)(Pic)2] (2), (NH4)[(UO2)2(O)2(Pic)] (3) and (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)] H2O (4) (INT = isonicotinate), all with 1D polymeric structures. The preparation of the four complexes is summarized in Scheme 1. The successful preparation of four different types of 1D uranyl hydrolysis polymers with the same organic ligand also provides a good opportunity to further examine and rationalize their formation mechanism by analyzing their uranyl connection topologies as well as comparing their properties, e.g. thermal stability and photoluminescence. 2. Results and discussion 2.1. Structure description and discussion The crystal data and structural refinement details for 1–4 are summarized in Table 1. Selected bond lengths and angles at U polyhedra are listed in Table 2, and the calculated bond valence sum (BVS) [18] at both U and coordinated O atoms are summarized in Table 3. 2.1.1. (UO2)(OH)(Pic) (1) Complex 1 contains uranyl hydroxyl dimers bridged by two hydroxyl groups (Fig. 1a and b) and each coordinated by a l2-(N, O; O0 ) bridging ligand at each side forming a 1D polymeric chain along the a-axis (Fig. 1c). The two hydroxyl groups are 2.589 Å apart from each other with calculated BVS of 1.19 [18]. In the literature, only a few polymeric structures containing multi-uranyl hydroxyl dimers are available [10d,17b]. As the structure of 1 was previously described [17b], its structure has been included purely for comparison whist additional characterizations (SEM/EDS, Raman, TG/DTA and photoluminescence) will be presented in detail. 2.1.2. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2) The structure of 2 is constructed from 7-fold coordinated uranium oxohydroxyl trimers with two oxo- and one hydroxyl groups
Scheme 1. Preparation of complexes 1–4 under hydrothermal conditions.
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and Pic ligands. There are three crystallographically distinct uranium centers (Fig. 2a and b) in the form of pentagonal bipyramids with uranyl bonds [1.775(10)–1.777(11) Å for U1A@O, 1.785(11)– 1.799(11) Å for U1B@O and 1.790(10)–1.830(10) Å for U1C@O] in apical positions. In the equatorial plane of U1A, there are two oxo-oxygen (OOXO) atoms, one hydroxyl (OOH), one carboxylate oxygen (OCOO) and one nitrogen atoms from a ligand [2.197(10)– 2.277(11) Å for U-OOXO, 2.322(10) Å for U-OOH, 2.582(10) Å for U-OL and 2.571(13) Å for U-NL]. U1C has a similar coordination environment in the equatorial plane as U1A, with two OOXO atoms, two OCOO and one nitrogen atoms from the coordinated ligands [2.215(10)–2.219(11) Å for U-OOXO, 2.489(10)–2.519(10) Å for U-OL and 2.609(13) Å for U-NL]. U1B has a different coordination environment in its equatorial plane with two OOXO atoms, one OOH and two OCOO atoms from the bridging ligands [2.247(11)– 2.261(11) Å for U1B-OOXO, 2.329(10) Å for U1B-OOH and 2.547 (11)–2.601(11) Å for U1B-OL]. The U-U distances are ranging from 3.7057(11)–3.9000(10) Å for U1A-U1B, 3.9658(11) Å for U1B-U1C and 3.6297(11) Å for U1C-U1A, respectively. Both O3 and O4 are l3-oxo-atoms linking three uranium centers with calculated BVS of 2.17 (O3) and 1.98 (O4) while O5 is a l2-hydroxyl group linking two uranium centers with calculated BVS of 1.22 [18]. The trinuclear uranyl units connect together through sharing oxo-, hydroxyl groups and l2-bridging Pic ligands forming a 1D infinite ribbon-style structure (Fig. 2c). 2.1.3. (NH4)[(UO2)2(O)2(Pic)] (3) The structure of 3 is constructed from 7-fold coordinated uranium oxo-dimers with two OOXO and Pic ligands. Two crystallographically distinct uranium centers (Fig. 3a and b) are in the form of pentagonal bipyramids with uranyl bonds [1.833(7) Å for U1@O and 1.802(7) Å for U2@O] in apical positions. In the equatorial plane of U1, there are four OOXO atoms and one OCOO from a ligand [2.195(8)–2.446(9) Å for U-OOXO and 2.535(8) Å for U-OCOO]. U2 has a different coordination environment in the equatorial plane with two OOXO, two OCOO and one nitrogen from the coordinated ligands [2.159(8)–2.193(9) Å for U-OOXO, 2.511(8)–2.718(8) Å for U-OCOO and 2.630(9) Å for U-NL]. The U1–U2 distance is 3.991 (9) Å. Both O3 and O6 are l3-oxo-atoms linking three uranium centers with calculated BVS [18] of 2.24 (O3) and 1.96 (O6). The dinuclear uranyl units connect together through sharing oxo groups and l3-bridging Pic ligands forming a 1D infinite ribbon-style structure (Fig. 3c). 2.1.4. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]H2O (4) The structure of 4 is constructed from 7-fold coordinated uranium oxohydroxyl tetranuclear unit with two OOXO, two OOH, two Pic and one INT ligands. The four crystallographically distinct uranium centers (Fig. 4a and b) are all in the form of pentagonal bipyramids with uranyl bonds [1.788(14)–1.827(14) Å for U1@O, 1.800(14) Å for U2@O, 1.771(13)–1.793(14) Å for U3@O and 1.814(13)–1.821(13) Å for U4@O] in apical positions. In the equatorial plane of U1, there are one OOXO, one OOH, two OCOO and one nitrogen atoms [2.207(11) Å for U-OOXO, 2.423(11) Å for UOOH, 2.342(11)–2.458(11) Å for U-OCOO and 2.643(14) Å for U-NL]. In the equatorial plane of U2, there are two OOXO, two OOH and one OCOO atoms [2.226(11)–2.381(11) Å for U2-OOXO, 2.363(11)– 2.496(10) Å for U2-OOH and 2.376(12) Å for U2-OL]. In the equatorial plane of U3, there are one OOXO, two OOH and two OCOO atoms [2.222(11) Å for U3-OOXO, 2.336(11)–2.452(11) Å for U3-OOH, and 2.513(11)–2.586(12) Å for U3-OCOO]. In the equatorial plane of U4, there are two OOXO, two OCOO and one nitrogen atoms [2.183 (11)–2.226(11) Å for U4-OOXO, 2.408(12)–2.538(12) Å for for U4OCOO and 2.612(14) Å for U4-NL]. The U–U distances are ranging from 3.8068(11) Å for U1–U2, 3.9850(10) Å for U1–U3, 3.7814 (11) Å for U2–U3, 3.9719(11) Å for U3–U4, 3.6999(10) Å for
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Table 1 Crystal data and refinement details for complexes 1–4.
a b
Complex
1
2
3
4
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z/dcalcd (g cm3) l (mm1)/F(0 0 0) Reflections/Independent reflections Rint/parameters refined Goodness-of-fit (GOF) Final R1 [I > 2r(I)]a Final wR2 [I > 2r(I)]b
C6H4NO5U 408.13 triclinic P1
C12H8N3O13U3 1120.34 monoclinic P21/c 7.1900(14) 20.007(4) 13.807(3) 90 93.28(3) 90 1982.9(7) 4/3.753 11.264/1940 18642/2496 0.0541/268 1.051 0.0400 0.0987
C6H4N2O8U2 708.17 orthorhombic Pnma 6.7910(14) 6.9550(14) 24.201(5) 90 90 90 1143.0(4) 4/4.115 13.009/1208 20665/1653 0.0380/66 1.180 0.0339 0.0748
C18H12N4O19U4 1540.44 monoclinic P21/n 7.3200(15) 16.272(3) 23.960(5) 90 95.84(3) 90 2839.1(10) 4/3.604 10.500/2672 35699/5396 0.0985/395 1.036 0.0802 0.2111
6.2810(13) 7.9570(16) 8.3540(17) 79.54(3) 87.77(3) 79.08(3) 403.14(15) 2/3.362 9.257/358 7495/1940 0.0905/95 1.133 0.0260 0.0702
R1 = RkFo| |Fck/|Fo|. wR2 = {R[w(F2o F2c )2]/R[w(F2o)2]}1/2.
Table 2 Selected bond lengths and angles for 1–4. 1 U1
2 U1A
U1B
U1C
3 U1
U2
4 U1
U2
U3
U4
Table 3 Calculated Bond Valence Sums (BVS) for 1–4.
U1–O1 O@U@O U1–O4 U1–O50
1.771(5) 174.5(2)° 2.393(3) 2.340(4)
U1–O2 U1–O3 U1–O5 U1–N1
1.789(5) 2.439(3) 2.298(4) 2.604(5)
U1A–O1A U1A–O2 U1A–O4 U1A–N1A U1B–O1B U1B–O2 U1B–O4 U1B–O7 U1C–O1C U1C–O1 U1C–O4 U1C–N1C
1.775(10) 2.582(10) 2.322(10) 2.571(13) 1.799(11) 2.601(11) 2.261(11) 2.547(11) 1.830(10) 2.489(10) 2.219(11) 2.609(13)
U1A–O2A U1A–O3 U1A–O5 O@U@O U1B–O2B U1B–O3 U1B–O5 O@U@O U1C–O2C U1C–O3 U1C–O7 O@U@O
1.777(11) 2.197(10) 2.277(11) 173.7(5)° 1.785(11) 2.247(11) 2.329(10) 178.7(5)° 1.790(10) 2.215(10) 2.519(10) 175.7(5)°
U1–O1 U1–O30 U–O6 O@U@O U2–O2 U2–O4 U2–O6 O@U@O
1.833(7) 2.257(8) 2.210(9) 175.2(4)° 1.802(7) 2.511(8) 2.193(9) 171.6(4)°
U1–O3 U1–O5 U–O60
2.195(8) 2.535(8) 2.446(9)
U2–O3 U2–O5 U2–N1
2.159(8) 2.718(8) 2.630(9)
U1–O1 U1–O9 U1–O14 U1–N1 U2–O3 U2–O11 U2–O15 U2–O18 U3–O5 U3–O9 U3–O13 U3–O18 U4–O7 U4–O12 U4–O17 U4–N2
1.827(14) 2.458(11) 2.342(11) 2.643(14) 1.800(14) 2.376(12) 2.381(11) 2.226(11) 1.793(14) 2.513(11) 2.452(11) 2.222(11) 1.814(13) 2.538(12) 2.408(12) 2.612(14)
U1–O2 U1–O13 U1–O15 O@U@O U2–O4 U2–O13 U2–O16 O@U@O U3–O6 U3–O12 U3–O16 O@U@O U4–O8 U4–O15 U4–O18 O@U@O
1.788(14) 2.423(11) 2.207(11) 176.6(6)° 1.800(14) 2.496(10) 2.363(11) 175.6(5)° 1.771(13) 2.586(12) 2.336(11) 177.3(5)° 1.821(13) 2.226(11) 2.183(11) 175.1(5)°
U2–U4, respectively. Both O15 and O18 are l3-oxo-atoms linking three uranium centers with calculated BVS of 1.98 for O15 and 2.21 for O18 while O13 (l3-) and O16 (l2-) are hydroxyl groups
1 U1
5.89
O1
1.69
O2
1.66
O5
1.19
2 U1A O2A O2C O5
6.04 1.71 1.62 1.22
U1B O1B O2 O7
5.98 1.63 0.72 0.80
U1C O2B O3
5.96 1.69 2.17
O1A O1C O4
1.61 1.70 1.98
3 U1 O3
6.07 2.24
U2 O6
6.03 1.96
O1
1.53
O2
1.62
4 U1 O1 O5 O13
5.78 1.55 1.64 1.37
U2 O2 O6 O15
5.96 1.65 1.73 1.98
U3 O3 O7 O16
5.89 1.61 1.57 1.12
U4 O4 O8 O18
5.86 1.61 1.56 2.21
linking uranium centers with calculated BVS of 1.37 (O13) and 1.12 (O16) [18]. The tetranuclear uranyl units connect together through sharing oxo-, hydroxyl groups with l2- and l3-Pic, and l2-INT ligands forming a 1D infinite structure (Fig. 4c). 2.1.5. Polymer formation and ribbon topologies Complex 2 is a uranyl oxohydroxyl Pic complex constructed with the uranyl oxohydroxyl trimers and both l2- and l3-Pic ligands forming a 1D ribbon-style polymeric structure. Contrary to 1 which can be prepared by several synthesis routes in a much wider solution pHs [17b], the formation of 2 requires relatively higher stabilized solution pH. The measured higher pHf (5.40) for 2 compared to pHf (4.01) for 1 would be the main reason for favoring the formation of 2. In the literature, two main types of 1D ribbons based on trinuclear uranyl units have been reported with mono-/poly-carboxylate ligands as well as pyridine dicarboxylate ligands [7,10,19,20]. However, these complexes are mainly hydroxyl-rich with more hydroxyl groups than oxo-groups. In contrast, 2 has more oxo-groups than hydroxyl groups. It is also of interest to compare their ribbon topologies. Fig. 5 shows the two ribbon topologies published together with the ribbon topology of 2. Clearly, the ribbon in 2 has a distinct connection topology as a result of in-turn coordination by l2- and l3-Pic ligands on both sides of the ribbon. Both 3 (a uranyl oxo-Pic complex) and 4 (a uranyl oxohydroxyl complex) have 1D uranyl polymeric structures. To our knowledge, they possess unique uranyl ribbon topologies (Fig. 6) which have not been identified before.
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Fig. 3. Structure of 3: ball-stick (a) and polyhedral (b) views of the dinuclear uranyl oxo-building unit and the 1D uranyl oxohydroxyl polymer (c) with l3-Pic ligands.
Fig. 1. Structure of 1: ball-stick (a) and polyhedral (b) views of the uranyl hydroxyl dimer building unit and a 1D polymeric chain (c) formed by linking the dimers through l2-bridging ligands.
Fig. 4. Structure of 4: ball-stick (a) and polyhedral (b) views of the tetranuclear uranyl oxohydroxyl building unit and the 1D uranyl oxohydroxyl polymer (c) with both Pic and INT bridging ligands.
Fig. 2. Structure of 2: ball-stick (a) and polyhedral (b) views of the trinuclear uranyl oxohydroxyl building unit and the 1D ribbon-type uranyl oxohydroxyl polymer (c) with both l2- and l3-Pic ligands.
2.1.6. Ligand coordination modes Several ligand coordination modes have been identified in complexes 1–4 including a l2-(N, O; O’) mode of Pic in 1 (Fig. 7a), a l3(N, O; O; O0 ) mode of Pic in 2, 3 and 4 (Fig. 7b), a l2-(N, O; O) mode of Pic in 2 and 4 (Fig. 7c) and a l2-(O; O0 ) mode of INT in 4 (Fig. 7d). 2.1.7. Hydrogen bonding and uranyl-cation interactions Complexes 2–4 all have (NH4)+ cations in the crystal lattice for charge balancing. Extensive uranyl-cation interactions via hydrogen bonding between (NH4)+ cations and O-yl atoms in 2–4 link the ribbons into closely packed 2D stacking structures (Fig. S3). The uranyl-cation interactions also influence the linearity of the uranyl unit with uranyl unit bending from 175.2(4) for O@U1@O
to 171.6(4)° for O@U2@O in 3, significantly deviated from the ideal 180°. 2.2. Vibrational modes Raman spectroscopy has long been used to study and fingerprint some uranium natural minerals and has the potential to differentiate various uranyl oxo- and hydroxyl mineral species [21]. Raman spectra of both 1 and 2 are shown in Fig. 8. The Raman assignments are based on some relevant literature data [22]. Both spectra look quite similar with the main dominating feature being the strong and sharp band at 845 cm1 for 1 and 820 cm1 for 2 due to the symmetric stretching vibration of (UO2)2+ with calculated U@O bond length of 1.767(9) Å for 1 and 1.791(9) Å for 2 [23], consistent with the values [1.771(5)–1.789(5) Å for U@O bonds in 1] and [1.775(10)–1.830(10) Å for U@O bonds in 2] obtained from the single crystal data. Other similar spectral features include: (1) the asymmetric and symmetric stretching vibrations of the carboxylate COO groups coordinated to U atoms are
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Fig. 5. A comparison of 1D ribbon-type structures built with pentagonal bipyramidal uranyl trinuclear units: (a) and (b) two ribbon topologies reported previously [7,10,19,20], and (c) a new ribbon connection topology found in 2.
Fig. 7. Coordination modes of Pic and INT: l2-mode of Pic in 1 (a), l3-mode of Pic in 2, 3 and 4 (b), l2-mode of Pic in 2 and 4 (c) and l2-mode of INT in 4.
Fig. 6. The unique uranyl ribbon topologies for 3 (a) and 4 (b).
found, respectively, at 1605 and 1412 cm1 for 1, and at 1597 and 1378 cm1 for 2; (2) two weak-to-medium intensity bands located around 1575 and 1550 cm1 for both 1 and 2 have been assigned to ring stretching vibrations (m (CC)arom), while the region 1480– 1443 cm1 is a combination of C–H deformation modes, and CO and CNC stretching modes [22]; (3) several weak Raman bands in the region 1160–1156 cm1 are due to in-plane d (CHarom) deformation; (4) the bands at 1050–1048 cm1 have been assigned predominantly to d (UOH) deformation mode; (5) Raman bands at 1020–1017 cm1 are due to the ring stretching vibration, m (CC)arom; (6) the weak band at 850 cm1 for 2 is due to out-of-plane d (CHarom) deformation vibration; (7) carboxylate COO in-plane and out-of-plane deformation modes are observed at 699 and 424 cm1, respectively, and the weak peak at 640 cm1 is due to ring deformations; (8) m (UOequatorial) vibrations are found at 367–351 cm1; (9) d (UO2)2+ and d (UOeq) deformation vibrations are at 290 and 245 cm1. Finally, there are several weak and broad bands at 592, 546 and 489 cm1 for 2, which have been assigned to the m (U3O) bridge elongation [24,25]. Raman spectra of 3 and 4 (Fig. S4) are quite similar to those of 1 and 2. Their detailed Raman band assignments are summarized in Table S1 together with those for 1 and 2.
Fig. 8. Raman spectra (2000–100 cm1) of 1 (a) and 2 (b).
2.3. Thermal stabilities All 1D polymers are thermally stable up to 350 °C and have very similar thermal decomposition patterns. Uranium oxide phase transitions at high temperature in air have been well documented [26]. U3O8 is the main oxide phase present after heating uranyl organic complexes over 710 °C, which has been observed previously by both DSC/TG and powder X-ray diffraction studies [26]. The DTA curve of 1 (Fig. S5a) has a large exotherm at 420 °C corresponding to the decomposition of Pic ligands and hydroxyl groups associated with a weight loss of 32.5% (calc. 32.0%) and a small endotherm at 730 °C corresponding to the phase transition to U3O8, with residue 68.5% observed (calc. 68.6%). The DTA curve of 2 (Fig. S5b) has a large exotherm at 430 °C corresponding to the decomposition of Pic ligands and NH+4 cations with a weight loss of 23.6% (calc. 23.5%) and a small endotherm at 730 °C corresponding to the phase transition to U3O8, with residue 76.0% observed (calc. 75.1%). The DTA curve of 3 (Fig. S6a) has a small
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350 °C and then lose organic ligands followed by further decomposition to form U3O8. Ligand enhanced red fluorescence emissions have been observed for 1, 3 and 4. Raman spectroscopy confirmed the presence of both uranyl ion and Pic ligand in 1–4. The overall chemical reactions for the formation of these 1D polymers are proposed and discussed. The variety of uranyl hydrolysis building units identified in this work highlights the complexity of the system as well as the potential to further explore the area. The synthesis method, with both advantages of controlling uranyl hydrolysis and generating ligand in situ, opens a new way to make polymeric phases containing various uranyl hydrolysis species. 4. Experimental 4.1. Synthesis
Fig. 9. Fluorescence emission spectra of 1–4 measured using their maximum excitation wavelengths.
exotherm at 420 °C and a large exotherm at 480 °C corresponding to the decomposition of NH+4 cations and Pic ligands, with a weight loss of 20.0% (calc. 21.1%) and a further phase transition to U3O8. Similarly, the DTA curve of 4 (Fig. S6b) has a large exotherm at 450 °C corresponding to the decomposition of Pic ligands with a weight loss of 27.9% (calc. 27.5%) and further phase transition to U3O8. 2.4. Photoluminescence The fluorescence emission spectra for 1–4 were collected in powder form at ambient temperature using their maximum excitation wavelengths. The fluorescence emission spectra of 2 and 3 (Fig. 9) are similar and have up to six emission bands in the range of 480 to 585 nm, characteristic of uranyl compounds with typical bands corresponding to the electronic transitions S11 ? S00 and S10 ? S0m (m = 0–4) of the uranyl ion [27]. The most intense bands are located at 518 nm for 2 and 515 nm for 3, compared to 510 nm observed for uranyl nitrate hexahydrates (UNH) [27,28]. However, both emission bands of S10 ? S02 and S10 ? S03 are slightly enhanced in 3. The emission spectra of 1 and 4 (Fig. 9) are very similar in broad feature with the most intense bands at 545 nm for 1 and 548 nm for 4, respectively, corresponding to enhanced S10 ? S02 and S10 ? S03 bands. The slightly red-shift effect for some uranyl carboxylate compounds have been discussed and attributed to the presence of pentagonal bipyramidal uranium centers [27,28]. However, further red-shift and broad nature in the cases of 1 and 4 can be attributed to the combined result of the uranium local coordination environment and the ligand effect. 3. Conclusions The aim of this work was to further explore the structural domain of uranyl picolinato complexes containing various uranyl hydrolysis species. Consequently, four uranyl hydroxyl and oxohydroxyl 1D polymers with Pic ligand have been synthesised via a unique hydrothermal approach. (UO2)(OH)(Pic) (1) is built with uranyl hydroxyl dimer as the building unit and Pic ligands. (NH4) [(UO2)3(O)2(OH)(Pic)2] (2) is built with uranyl oxohydroxyl trinuclear units and both l2- and l3-bridging Pic ligands. (NH4) [(UO2)2(O)2(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked by l3-Pic ligands. (NH4)[(UO2)4(O)2 (OH)2(Pic)2 (INT)]H2O (4) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands. All four 1D polymers are thermal stable to at least
Caution! Depleted uranium (238U) is radioactive and its compounds should be handled with care within proper radiologically surveyed facilities. Strategy: A previous study [29] demonstrated that the uranyl ion can be coordinated with picolinamide (PA) to give a stable uranyl bis(PA) species with a solution pH 5.6. This solution was used in the current study, with various amounts of NaHCO3 added to generate the designed Pic ligand in situ under hydrothermal conditions. (UO2)(OH)(Pic) (1). Uranyl nitrate (1.0 mL, 0.5 M), picolinamide (2.0 mL, 0.5 M), NaHCO3 (0.5 mL, 0.25 M) solutions and 5.0 mL deionized (DI) water were added in a 120 mL Teflon container, sealed in a stainless steel pressure Parr vessel and left in a 190 °C oven for 48 h. A yellow crystalline product of 1 was formed after slow cooling (5 °C/h) to room temperature in a light yellow solution (pHf = 4.0) with 70% yield (72 mg) based on U content. C6H5NO5U (FW = 409.13): calc. C, 17.61; H, 1.23; N, 3.42; found: C, 17.58; H, 1.28; N, 3.35. Complex 1 was previously prepared with initial solution pH ranging from 1.60 to 4.14, and the structure was described [17b]. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2). Similarly to 1, complex 2 was synthesized with uranyl nitrate (1.0 mL, 0.5 M), picolinamide (2 mL, 0.5 M), NaHCO3 (1.0 mL, 0.25 M) solutions and 5.0 mL of DI water hydrothermally. A yellow crystalline product of 2 was formed in a light yellow solution (pHf = 5.4) with over 80% yield (151 mg). C12H13N3O13U3 (FW = 1121.32): calc. C, 12.85; H, 1.17; N, 3.75. Found: C, 12.76; H, 1.28; N, 3.82%. (NH4)[(UO2)2(O)2(Pic)] (3). Complex 3 was prepared in the similar way as for 2 but with double quantity of NaHCO3 and crystallized in a light yellow solution (pHf = 5.8) with 87% yield (155 mg). C6H8N2O8U2 (FW = 712.19): calc. C, 10.12; H, 1.13; N, 3.93. Found: C, 10.08; H, 1.22; N, 3.87%. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]H2O (4). Similar to the preparation of complex 3, complex 4 was prepared with further addition of 1.0 mmol isonicotinic acid and it was crystallized in a light yellow solution (pHf = 5.6) with over 70% yield (137 mg). C18H20N4O19U4 (FW = 1548.47): calc. C, 13.96; H, 1.30; N, 3.62. Found: C, 13.94; H, 1.28; N, 3.59%. The examination of the products using electron microscope reveals that they are all crystalline products. Elemental analysis, SEM-EDS, TG/DTA, photoluminescence, Raman spectroscopy and single crystal X-ray diffraction have been used to further study the four phases. SEM-EDS analysis confirmed the presence of C, N, O and U in 1–4 (Figs. S1 and S2). 4.2. Characterization 4.2.1. Elemental analyses Elemental analyses were carried out using a Perkin-Elmer 2400 CHN elemental analyzer.
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4.2.2. Scanning Electron Microscope and Electron Dispersive Spectroscopy (SEM-EDS) A Zeiss Ultra Plus SEM (Carl Zeiss NTS GmbH, Oberkochen, Germany) operating with an accelerating voltage of 20 kV was used to probe the key elements present. 4.2.3. Raman spectroscopy Raman spectra were recorded on a Perkin Elmer Raman station 400 with Micro300 Microscope and excitation laser 785 nm in the range 2000–100 cm1. 4.2.4. Photoluminescence Fluorescence emission spectra were measured using a Varian Cary Eclipse Fluorescence Spectrometer. 4.2.5. Thermogravimetric and differential thermal analysis (TG/DTA) TG/DTA was made on a SEIKO 6300 Thermal Analyzer from room temperature to 1000 °C with a heating rate of 10 °C min1 and an air flow rate of 300 cm3 min1. 4.3. Single crystal X-ray diffraction The Single-crystal X-ray data for 1–4 were collected at 100(2) K on the MX2 beamline at the Australian Synchrotron with Silicon Double Crystal radiation (k = 0.72930 Å). All data were collected using BlueIce software [30]. An empirical absorption correction was applied to the data using SADABS [31]. Cell refinements and data reductions were carried out using XDS software [32]. The structures were solved by direct methods using SHELXT [33] and the full-matrix least-squares refinements were carried out using SHELXL [34] via Olex2 interface [35]. Complex 2 has large solvent accessible voids in the crystal lattice. However no electron density could be located. The one circle goniometer geometry of data collections at MX2 beamline offers less opportunity for applying multi-scan absorption correction as is possible with the data collections on a four circle goniometer. Consequently, ripples around U atoms are often present due to ineffective absorption correction. In addition, the data completeness is relatively low for crystals in low symmetry space groups, especially for 1 in triclinic space group. Acknowledgements We would like to acknowledge Dr M. Bhadbhade for helpful discussion on crystal structure refinements. The crystallographic data for 1–4 were collected on the MX2 beamline at the Australian Synchrotron, Victoria, Australia. Appendix A. Supplementary data CCDC 998972 (1), 998973 (2), 1423618 (3) and 1423619 (4) contains the supplementary crystallographic data for . These data can be obtained free of charge via http://www.ccdc.cam.ac. uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.poly.2016.04.028. References [1] G.R. Choppin, J. Radioanal. Nucl. Chem. 273 (3) (2007) 695. [2] (a) P. Crançon, J. van der Lee, Radiochim. Acta 91 (2003) 673; ˇ ejka, G.R. Lumpkin, T.T. Tran, I. Aharonovich, J.R. Price, N. (b) Y. Zhang, J. C Scales, K. Lu, New J. Chem. (2016), http://dx.doi.org/10.1039/C5NJ03055B. [3] F. Quilès, C. Nguyen-Trung, C. Carteret, B. Humbert, Inorg. Chem. 50 (7) (2011) 2811.
[4] I. Grenthe, J. Fuger, R.J.M. Konings, R.J. Lemire, C. Nguyen-Trun, H. Wanner, in: H. Wanner, I. Forest (Eds.), Chemical Thermodynamics of Uranium, Organisation for Economic Corporation and Development, Issy-lesMoulineau, France, 2004. [5] S. Tsushima, A. Rossberg, A. Ikeda, K. Müller, A.C. Scheinost, Inorg. Chem. 46 (25) (2007) 10819. [6] F. Quilès, A. Burneau, Vib. Spectrosc. 23 (2) (2000) 231. [7] M.B. Andrews, C.L. Cahill, Chem. Rev. 113 (2) (2013) 1121. [8] (a) Z.L. Liao, G.D. Li, X.A. Wei, Y. Yu, J.S. Chen, Eur. J. Inorg. Chem. (2010) 3780; (b) Z.T. Yu, G.H. Li, Y.S. Jiang, J.J. Xu, J.S. Chen, Dalton Trans. (2003) 4219; (c) P. Thuéry, M. Nierlich, B. Souley, Z. Asfari, J. Vicens, J. Chem. Soc., Dalton Trans. (1999) 2589; (d) P. Thuéry, B. Masci, Supramol. Chem. 15 (2003) 95. [9] (a) S. Dalai, M. Bera, A. Rana, D.S. Chowdhuri, E. Zangrando, Inorg. Chim. Acta 363 (13) (2010) 3407; (b) P. Thuéry, Eur. J. Inorg. Chem. 26 (2013) 4563; c) W. Zhang, J. Zhao, J. Mol. Struct. 789 (2006) 177. [10] (a) A.T. Kerr, C.L. Cahill, Cryst. Growth Des. 11 (12) (2011) 5634; (b) I. Mihalcea, N. Henry, T. Loiseau, Cryst. Growth Des. 11 (2011) 1940; (c) I. Mihalcea, N. Henry, C. Volkringer, T. Loiseau, Cryst. Growth Des. 12 (2012) 526; (d) P. Thuéry, Cryst. Growth Des. 11 (2011) 3282; (e) Y.-S. Jiang, Z.-T. Yu, Z.-L. Liao, G.-H. Li, J.-S. Chen, Polyhedron 25 (6) (2006) 1359; (f) I.A. Charushnikova, N.N. Krot, Z.A. Starikova, Radiokhimiya (Russ.) 46 (2004) 396. [11] K.E. Knope, L. Soderholm, Chem. Rev. 113 (2013) 944. [12] (a) P.A. Baisden, G.R. Choppin, Nuclear Waste Managements and the Nuclear Fuel Cycle, Radiochemistry and Nuclear Chemistry, Encyclopedia of Life Support Systems, Oxford, 2007; (b) R.G. Riley, J.M. Zachara, Chemical Contaminants on DOE Lands and Selection of Contaminant Mixtures for Subsurface Science Research, Pacific Northwest Lab., Richland, WA (United States), 1992, p. 77. [13] C.V. McIsaac, D.W. Akers, J.W. McConnell, N. Morcos, Leach Studies on Cementsolidified Ion Exchange Resins from Decontamination Processes at Operating Nuclear Power Stations, Idaho National Engineering Laboratory, Idaho Falls, Idaho, USA, 1992, p. 17. [14] (a) E.V. Grechishnikova, E.V. Peresypkina, A.V. Virovets, Yu.N. Mikhailov, L.B. Serezhkina, Koord. Khim. (Russ.) 33 (2007) 468; (b) V.I. Mishkevich, M.S. Grigoriev, A.M. Fedosseev, P. Moisy, Acta Crystallogr., Sect. E 68 (2012) m1243; (c) W. Aas, M.H. Johansson, Acta Chem. Scand. 53 (1999) 581. [15] P.R. Silverwood, D. Collison, F.R. Livens, R.L. Beddoes, R.J. Taylor, J. Alloys Compd. 271 (1998) 180. [16] P. Thuéry, Inorg. Chem. Commun. 12 (2009) 800. [17] (a) R.C. Severance, S.A. Vaughn, M.D. Smith, H.-C. Zur Loye, Solid State Sci. 13 (2011) 1344; (b) M.B. Andrews, C.L. Cahill, CrystEngComm 13 (2011) 7068. [18] (a) I.D. Brown, Chem. Rev. 109 (2009) 6858; (b) F.C. Hawthorne, Phys. Chem. Miner. 39 (2012) 841; (c) P.C. Burns, R.C. Ewing, F.C. Hawthorne, Can. Mineral. 35 (1997) 1551. [19] P. Thuéry, CrystEngComm 14 (2012) 3363. [20] T. Loiseau, I. Mihalcea, N. Henry, C. Volkringer, Coord. Chem. Rev. 266–267 (2013) 69. [21] R.L. Frost, J. Cejka, M.L. Weier, J. Raman Spectrosc. 38 (2007) 460. [22] (a) G. Socrates, Infrared and Raman Characteristic Group Frequencies: Tables and Charts, third ed., John Wiley & Sons Hoboken, New York, 2004; (b) Y. Zhang, J.R. Price, I. Karatchevtseva, K. Lu, B. Yoon, F. Kadi, G.R. Lumpkin, F. Li, Polyhedron 91 (2015) 98; (c) Y. Zhang, M. Bhadbhade, I. Karatchevtseva, J. Gao, J.R. Price, G.R. Lumpkin, Eur. J. Inorg. Chem. (2013) 6170; (d) Y. Zhang, J. Cˇejka, I. Karatchevseva, M. Qin, L. Kong, K. Short, S.C. Middleburg, G.R. Lumpkin, J. Nucl. Mater. 446 (2014) 68; (e) Y. Zhang, I. Karatchevtseva, M. Qin, S.C. Middleburgh, G.R. Lumpkin, J. Nucl. Mater. 437 (2013) 149; (f) Y. Zhang, I. Karatchevtseva, M. Bhadbhade, T.T. Tran, I. Aharonovich, D.J. Fanna, N.D. Shepherd, K. Lu, F. Li, G.R. Lumpkin, J. Solid State Chem. 234 (2016) 22. [23] J.R. Bartlett, R.P. Cooney, J. Mol. Struct. 193 (1989) 295. [24] P.K. Sinha, M. Bolboaca, S. Schlücker, J. Popp, W. Kiefer, J. Raman Spectrosc. 34 (2003) 276. [25] A.T. Fiedler, X. Shan, M.P. Mehn, J. Kaizer, S. Torelli, J.R. Frisch, M. Kodera, L. Que Jr., J. Phys. Chem. A 112 (50) (2008) 13037. [26] (a) E. Gómez-Rebollo, P. Herrero, R.M. Rojas, J. Nucl. Mater. 245 (1997) 161; (b) K. Sudo, A. Okawa, Bull. Res. 16 (1) (1960) 85. Institute of Mineral Dressing and Metallurgy, Tohoku University; ˇ ejka, J. Sejkora, Z. Mrázek, Z. Urbanec, T. Jarchovsky´, Neues Jahrbuch für (c) J. C Mineralogie Abhandlungen 170 (1996) 155. [27] (a) Y. Zhang, M. Bhadbhade, I. Karatchevtseva, J.R. Price, H. Liu, Z. Zhang, ˇ ejka, L. Kong, K. Lu, G.R. Lumpkin, J. Solid State Chem. 226 (2015) J. C 42; (b) Y. Zhang, I. Karatchevtseva, J.R. Price, I. Aharonovich, F. Kadi, G.R. Lumpkin, F. Li, RSC Adv. 5 (2015) 33249. [28] (a) I. Mihalcea, N. Henry, T. Loiseau, Eur. J. Inorg. Chem. (2014) 1322; (b) Y. Zhang, J.K. Clegg, K. Lu, G.R. Lumpkin, T.T. Tran, I. Aharonovich, N. Scales, F. Li, Chem. Select 1 (1) (2016) 7.
N.D. Shepherd et al. / Polyhedron 113 (2016) 88–95 [29] Y. Zhang, M. Bhadbhade, J. Gao, I. Karatchevseva, J.R. Price, G.R. Lumpkin, Inorg. Chem. Commun. 37 (2013) 219. [30] T.M. McPhillips, S.E. McPhillips, H.J. Chiu, A.E. Cohen, A.M. Deacon, P.J. Ellis, E. Garman, A. Gonzalez, N.K. Sauter, R.P. Phizackerley, S.M. Soltis, P. Kuhn, J. Synchrotron Radiat. 9 (2002) 401. [31] W. Kabsch, J. Appl. Crystallogr. 26 (1993) 795. [32] SADABS: Empirical Absorption and Correction Software, University of Göttingen, 1996–2008.
95
[33] (a) G.M. Sheldrick, Acta Crystallogr., Sect. A 71 (2015) 3; (b) SHELXT-2014, G.M. Sheldrick, University of Göttingen, 2014. [34] (a) G.M. Sheldrick, Acta Crystallogr., Sect. C 71 (2015) 3; (b) SHELXL-2014, G.M. Sheldrick, University of Göttingen, 2014. [35] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl. Crystallogr. 42 (2009) 339.