Series of Hydrated Heterometallic Uranyl-Cobalt(II) Coordination

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Series of Hydrated Heterometallic Uranyl-Cobalt(II) Coordination Polymers with Aromatic Polycarboxylate Ligands: Formation of UOCo Bonding upon Dehydration Process Clément Falaise,† Jason Delille,† Christophe Volkringer,*,†,‡ Hervé Vezin,§ Pierre Rabu,∥ and Thierry Loiseau† †

Unité de Catalyse et Chimie du Solide (UCCS)−UMR CNRS 8181, Université de Lille, ENSCL, Bat C7, BP 90108, 59652 Villeneuve d’Ascq, France ‡ Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris Cedex 05, France § Laboratoire de Spectrochimie Infrarouge et Raman (LASIR)−UMR CNRS 8516, Université de Lille, ENSCL, Bat C7, BP 90108, 59652 Villeneuve d’Ascq, France ∥ Département de Chimie des Matériaux Inorganiques, IPCMS and NIE, UMR 7504 CNRS-UdS, 23, rue du Loess, BP 43, 67034 Strasbourg cedex 2, France S Supporting Information *

ABSTRACT: Five new heterometallic UO22+−Co2+ coordination polymers have been obtained by hydrothermal reactions of uranyl nitrate and metallic cobalt with aromatic polycarboxylic acids. Single-crystal X-ray diffraction reveals the formation of four 3D frameworks with the mellitate (noted mel) ligand and one 2D network with the isophthalate (noted iso) ligand. The compounds [(UO 2 (H 2 O)) 2 Co (H 2 O) 4 (m el)]·4H 2 O (1 ), [U O 2 Co (H2O)4(H2mel)]·2H2O (2), and [(UO2(H2O))2Co(H2O)4(mel)] (4) consist of 3D frameworks built up from the connection of mellitate ligands and mononuclear metallic centers. These three compounds exhibit two types of geometry for the uranyl cation: pentagonal bipyramidal environment for 1 and 4, and hexagonal bipyramidal environment for 2. Using the mellitate ligand, the uranyl dinuclear unit is isolated in the compound [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3). Due to their 2D framework and the presence of uncoordinated cobalt(II) cations, the compound [(UO2)(iso)3][Co(H2O)6]·3(H2O) (5) is drastically different than the previous one. The thermal behavior of compounds 1, 2, and 3 has been studied by thermogravimetric analysis, X-ray thermodiffraction, and in situ infrared. By heating, the dehydration of compounds 1 and 2 promotes two structural transitions (1 → 1′ and 2 → 2′). The crystal structures of [(UO2(H2O))2Co(H2O)2(mel)] (1′) and [(UO2)Co(H2mel)] (2′) were determined by single-crystal X-ray diffraction; each of them presents a heterometallic interaction between uranyl bond and the Co(II) center. Due to the rarely reported coordination environment for the cobalt center in compound 2′ (square pyramidal configuration), the magnetic properties and EPR characterizations of the compounds 2 and 2′ were also investigated.

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INTRODUCTION

the complexation of uranium. In fact, the carboxylate functions are present in humic/fulvic acids.5 Some smallest carboxylate ligands occur in nature, since mellitate species are found in aluminum salts,6 for instance. Uranium carboxylate chemistry has had rapid expansion since the past decade. This renewed interest is correlated with the development of hybrid inorganic−organic compounds also called porous coordination polymers or metal−organic frameworks (also known as MOF) which offer a wide variety of applications such as gas storage, drug delivery, catalysis, etc.7 Currently, uranyl carboxylates are sometimes called a uranyl-

The understanding of behavior of the actinides in the geosphere involves the fundamental studies of the chemical interactions of the actinides with the environment component. Currently, the chemical interaction of uranium hexavalent (uranyl; UO22+) with many types of inorganic (phosphates, vanadates, etc.) or organic (O-donor, N-donor, etc.) ligands has been particularly well-investigated. The great interest for the uranyl cations is due to the predominance of its hexavalent state under air atmosphere. The uranium interactions with the environment are very complex involving the sorption on mineral surface,1 the hydrolysis/condensation,2,3 bioreduction process,4 and also the complexation. Among the complexing groups in the soil, the carboxylate functions play a key role in © XXXX American Chemical Society

Received: July 15, 2016

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DOI: 10.1021/acs.inorgchem.6b01697 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

The compounds have been hydrothermally synthesized under autogenous pressure using a 23 mL Teflon-lined stainless steel Parr autoclave and using the following chemical reactants: uranyl nitrate hexahydrate (UO2(NO3)2·6H2O), isophthalic acid (noted H2iso, C8H6O4, Aldrich 99%), mellitic acid (noted H6mel, C12H6O12, Aldrich, 99%), powder of metallic cobalt (noted Co0, Alfa Aesar, 99.8%), and distilled water. The reactant mixtures have been manipulated and weighted under air atmosphere. [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1). A mixture of 250 mg (0.5 mmol) of UO2(NO3)2·6H2O, 34 mg (0.58 mmol) of Co0, 100 mg (0.29 mmol) of H6mel, and 5 mL (278 mmol) of H2O was placed in a Parr autoclave and then heated statically at 150 °C for 24 h. The pH value of the solution was 1.25 before the hydrothermal treatment. The resulting orange powder was then filtered off, washed with water, and dried at room temperature in air atmosphere. It gave crystallites with a specific block shape of 120−300 μm as can be observed by scanning electron microscope (Hitachi S-3400N) (Figure S1). Yield (based on uranium): 67% (282 mg). [UO2Co(H2O)4(H2mel)]·2H2O (2). A mixture of 250 mg (0.5 mmol) of UO2(NO3)2·6H2O, 26 mg (0.44 mmol) of Co0, 100 mg (0.29 mmol) of H6mel, and 5 mL (278 mmol) of H2O was placed in a Parr autoclave and then heated statically at 150 °C for 24 h. The pH value of the solution was 1.26 before the hydrothermal treatment. The resulting orange powder was then filtered off, washed with water, and dried at room temperature in air atmosphere. It gave an agglomerate of crystallites with a specific block shape of 40−100 μm as can be observed by scanning electron microscope (Hitachi S-3400N) (Figure S2). Yield (based on uranium): 50% (192 mg). [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3). A mixture of 250 mg (0.5 mmol) of UO2(NO3)2·6H2O, 30 mg (0.51 mmol) of Co0, 100 mg (0.29 mmol) of H6mel, and 5 mL (278 mmol) of H2O was placed in a Parr autoclave and then heated statically at 200 °C for 24 h. The pH value of the solution was 1.20 before the hydrothermal treatment. The resulting orange powder was then filtered off, washed with water, and dried at room temperature in air atmosphere. Different attempts were made to isolate and obtain pure phase 3, but were unsuccessful. Mixture of phases 3 and 4 are always observed. [(UO2(H2O))2Co(H2O)4(mel)] (4). A mixture of 250 mg (0.5 mmol) of UO2(NO3)2·6H2O, 31 mg (0.53 mmol) of Co0, 100 mg (0.29 mmol) of H6mel, and 5 mL (278 mmol) of H2O was placed in a Parr autoclave and then heated statically at 200 °C for 48 h. The pH value of the solution was 1.03 before the hydrothermal treatment. The resulting orange powder was then filtered off, washed with water, and dried at room temperature in air atmosphere. It gave crystallites with a specific block shape of 100−250 μm as it can be observed by scanning electron microscope (Hitachi S-3400N) (Figure S3). Yield (based on uranium): 60% (227 mg). [(UO2)(iso)3][Co(H2O)6]·3(H2O) (5). A mixture of 250 mg (0.5 mmol) of UO2(NO3)2·6H2O, 30 mg (0.51 mmol) of Co0, 80 mg (0.48 mmol) of H2iso, and 5 mL (278 mmol) of H2O was placed in a Parr autoclave and then heated statically at 150 °C for 24 h. The pH value of the solution was 2.2 before the hydrothermal treatment. The resulting orange powder was then filtered off, washed with water, and dried at room temperature in air atmosphere. The analysis of powder X-ray diffraction reveals that the final product is composed of phase 5 and crystallized isophthalic acid. We tried to isolate compound 5 by washing the final product with DMF (N,N-dimethylformamide), but unfortunately, the DMF washing decomposed phase 5. Single-Crystal X-ray Diffraction. Crystals of compounds 1−5 were selected under polarizing optical microscope and glued on a glass fiber for a single-crystal X-ray diffraction experiment. X-ray intensity data were collected on a Bruker DUO-APEX2 CCD area detector diffractometer using Mo Kα radiation (λ = 0.71073 Å) with an optical fiber as collimator. Several sets of narrow data frames (20 s per frame) were collected with ω scans. Data reduction was accomplished using SAINT V7.53a.54 The substantial redundancy in data allowed a semiempirical absorption correction (SADABS V2.1055) to be applied, on the basis of multiple measurements of equivalent reflections. The structure was solved by direct methods, developed by successive difference Fourier syntheses, and refined by full-matrix least-squares on

organic framework (also known as UOF), and represent the major contribution of uranium carboxylate chemistry.8 These hybrid uranyl-organic architectures have been reported with different dimensionalities (0D to 3D), exhibiting various coordination polyhedra for uranyl cations (bipyramidal environment with equatorial plane tetragonal, pentagonal, or hexagonal).8−10 The uranyl cations can promote diverse building units from isolated mononuclear species up to infinite chain-like nets. In addition to the complexation with carboxylate ligand, uranium could interact with transition metals present in the soil, involving various chemical behaviors such as the reduction of UO22+ to U4+ or the formation of polymetallic minerals. So far, the knowledge about uranium coordination chemistry in nature remains relatively low, due to the difficulty to provide the exact atomic organization of biomolecules combining uranium and other cations. The crystallization of molecular species from aqueous solution using carboxylate ligand can help to fill this lack of information, especially if the selected organic linker occurs naturally. Regarding the literature, the association of uranyl and heterometal (M) such as a divalent transition metal or rare earth is particularly studied with heterofunctional linker molecules (carboxyphosphinates,11 phosphonate−carboxylates,12−19 pyridine-carboxylates20−26) or the addition of N-donor molecules.27−30 The isolation of bimetallic UO22+−M coordination polymers with carboxylate ligands is also reported (M = Ni 2+ , 11,31−33 Co 2+ , 11,31 Cu 2+ , 31−41 Zn 2+ , 11,42,43 Ln3+32,44−49). Following our investigation into the formation of UO22+-3d coordination polymers where 3d = Cu2+,37 Zn2+,43 we continue our studies on the investigation of the uranyl-cobalt system under mild hydrothermal conditions. Some heterometallic UO22+−Co2+ compounds containing carboxylate functions were previously isolated with carboxyphosphonate,15,16 acetate,50 or derived malonatate51,52 ligands. In the geosphere, uranium is known to form minerals with cobalt like the metakirchheimerite Co(UO2)2(AsO4)2·8(H2O), cobalt zippeite Co2(UO2)6(SO4)3(OH)10·16(H2O), or oursinite (Co,Mg)(H3O)2[(UO2)SiO4]2·3(H2O).53 In this paper, we present the hydrothermal synthesis of five new heterometallic UO22+−Co2+ coordination polymers obtained from the reaction of uranyl nitrate, metallic cobalt, and multidentate carboxylic acid. Among the five compounds, four of them were isolated with the mellitate (mel) ligand ([(UO2(H2O))2Co(H2O)4(mel)]· 4H2O (1), [UO2Co(H2O)4(H2mel)]·2H2O (2), [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3), [(UO2(H2O))2Co(H2O)4(mel)] (4), and one with the isophthalate (iso) ligand ([(UO2)(iso)3](Co(H2O)6) (5)). The thermal decomposition of 1, 2, and 3 was then analyzed by X-ray diffraction, thermogravimetric analysis, and in situ infrared. Upon heating, compounds 1 and 2 are transformed through dehydration processes (1 → 1′ and 2 → 2′). The crystal structures of the dehydrated phases 1′ and 2′ have been determined by single-crystal X-ray diffraction. Compound 2′ reveals a rarely reported coordination sphere for the cobalt(II) cations (distorted square pyramidal environment). The magnetism behavior and EPR characterizations of compounds 2 and 2′ have been studied.

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EXPERIMENTAL SECTION

Synthesis. Caution! Uranyl nitrate is a radioactive and chemically toxic reactant, so precautions with suitable care and protection for handling such substances have been followed. B


Article

Inorganic Chemistry Table 1. Crystal Data and Structure Refinement for Heterometallic Uranyl-Cobalt(II) Coordination Polymers 1 formula fw T/K cryst type cryst size/mm3 cryst syst space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z, ρcalcd/g cm−3 μ/mm−1 Θ range/deg limiting indices

collected reflns unique reflns params GOF on F final R indices [I > 2σ(I)] R indices (all data) largest diff peak and hole/e Å−3

1′

2

2′

3

4

5

U2CoC12O26 1095.11 293(2) yellow block 0.13 × 0.09 × 0.06 triclinic P1̅ 6.8850(3) 8.5229(4) 11.3840(5) 95.411(2) 90.800(2) 108.870(2) 628.59(5) 1, 2.893 13.617 1.80−30.51 −9 ≤ h ≤ 9 −12 ≤ k ≤ 12 −16 ≤ l ≤ 14 16 305 3827 [Rint = 0.0261] 181 1.01 R1 = 0.0174

U2CoC12O20 999.11 293(2) orange block 0.15 × 0.07 × 0.06 triclinic P1̅ 6.8061(6) 8.2468(7) 9.0956(8) 103.824(4) 94.823(4) 102.719(4) 478.51(7) 1, 3.467 17.847 2.33−30.54 −9 ≤ h ≤ 9 −11 ≤ k ≤ 11 −12 ≤ l ≤ 11 13 410 2845 [Rint = 0.0237] 160 1.067 R1 = 0.0175

UCoC12O20 761.08 293(2) yellow block 0.12 × 0.10 × 0.07 triclinic P1̅ 6.30370(10) 8.3564(2) 9.1115(2) 97.9190(10) 91.4380(10) 103.2040(10) 462.018(17) 1, 2.735 9.761 2.26−28.33 −8 ≤ h ≤ 8 −10 ≤ k ≤ 11 −12 ≤ l ≤ 12 12 902 2291 [Rint = 0.0240] 152 1.090 R1 = 0.0170

UCoC12O14 UCoC6O14 665.08 593.02 293(2) 293(2) blue block yellow block 0.10 × 0.08 × 0.05 0.09 × 0.05 × 0.05 monoclinic triclinic P1̅ P21 5.8725(5) 8.2965(2) 17.3346(18) 8.5833(2) 6.9668(8) 9.8760(2) 90 96.5640(10) 94.346(6) 102.9380(10) 90 94.1990(10) 707.16(12) 677.38(3) 2, 3.124 2, 2.907 12.7 13.237 3.16−27.34 2.14−28.31 −7≤ h ≤ 7 −10 ≤ h ≤ 11 −19 ≤ k ≤ 18 −11 ≤ k ≤ 11 −8 ≤ l ≤ 8 −13 ≤ l ≤ 13 1795 12 285 1606 3356 [Rint = 0.0235] [Rint = 0.0274] 123 197 1.258 0.999 R1 = 0.0681 R1 = 0.0305

U2CoC12O22 1031.11 293(2) orange block 0.12 × 0.10 × 0.09 triclinic P1̅ 8.870(2) 11.134(3) 11.215(3) 86.203(14) 87.314(14) 87.076(14) 1102.7(5) 2, 3.105 15.501 1.92−28.39 −11 ≤ h ≤ 10 −14 ≤ k ≤ 14 −14 ≤ l ≤ 14 21 639 5484 [Rint = 0.0376] 337 1.090 R1 = 0.0266

orthorhombic C2221 8.3900(2) 18.0142(3) 21.9051(4) 90 90 90 3310.72(11) 4, 2.478 10.355 1.86−30.56 −11 ≤ h ≤ 10 −25 ≤ k ≤ 25 −31 ≤ l ≤ 31 36 597 5062 [Rint = 0.0292] 237 1.082 R1 = 0.0188

wR2 = 0.0445 R1 = 0.0201 wR2 = 0.0457 1.67 and −0.87

wR2 = 0.0374 R1 = 0.0205 wR2 = 0.0382 1.11 and −0.68

wR2 = 0.0443 R1 = 0.0171 wR2 = 0.0444 1.33 and −0.52

wR2 = 0.1802 R1 = 0.0830 wR2 = 0.2065 4.44 and −3.66

wR2 = 0.0670 R1 = 0.0339 wR2 = 0.0709 1.08 and −1.71

wR2 = 0.0383 R1 = 0.0203 wR2 = 0.0386 0.81 and −1.10

all F2 data using SHELX56 program suite with the WINGX interface.57 For compound 5, hydrogen atoms of the benzene ring of phthalate ligand were included in calculated positions and allowed to ride on their parent atoms. The final refinements include anisotropic thermal parameters of all non-hydrogen atoms except for compound 2′. Due to the low quality of data (very high mosaicity), the final refinement of 2′ includes only anisotropic thermal parameters for metallic centers. The crystal data are given in Table 1. Supporting Information is available in CIF format. Thermogravimetric Analysis. The thermogravimetric experiments have been carried out on a thermoanalyzer TGA 92 SETARAM under air atmosphere with a heating rate of 10 °C.min−1 from room temperature up to 800 °C. X-ray thermodiffractometry was performed under 5 L h−1 air flow in an Anton Paar HTK1200N of a D8 Advance Bruker diffractometer (θ−θ mode, Cu Kα radiation) equipped with a Vantec1 linear position sensitive detector (PSD). Each powder pattern was recorded in the range 7−60° (2θ) (at intervals of 20 °C between RT and 800 °C) with a 1 s step−1 scan, corresponding to an approximate duration of 27 min. The temperature ramps between two patterns were 5 °C min−1. Infrared Spectroscopy. Infrared spectra of powdered compounds 1, 2, and 4 were measured on a Perkin-Elmer Spectrum Two spectrometer, equipped with a diamond attenuated total reflectance (ATR) accessory between 4000 and 400 cm−1 (see the Supporting Information). Phase transformation of compounds 1 and 2 was characterized by in situ IR spectroscopy in air with a heating rate of 10 °C min−1 from RT (room temperature) up to 210 °C. During this period, 195 spectra were recorded in the range 4000−400 cm−1, with a resolution of 4 cm−1, on a Perkin−Elmer Spectrum Two spectrometer, equipped with a Pike Special-IR GladiATR accessory.

wR2 = 0.0624 R1 = 0.0371 wR2 = 0.0661 2.93 and −2.52

U2CoC24O25H12 1235.33 293(2) orange block 0.17 × 0.15 × 0.09

Magnetic Measurement. The magnetic studies were carried out using a SQUID magnetometer (Quantum Design Squid-VSM) covering the temperature and field ranges 2−400 K, ±7 T. Magnetization versus field measurements at room temperature confirm the absence of ferromagnetic impurities. Data were corrected for the sample holder, and diamagnetism of the compounds was estimated from Pascal constants. EPR Spectroscopy. EPR spectra were recorded on a Bruker ELEXSYS E580 spectrometer using continuous wave (CW) mode within X band. Spectra of both the native compound and the sample after heating at 180 °C were collected at 5 K using a Bruker Cryofree cryostat system. Microwave power and modulation amplitude were, respectively, set to 2 mW and 1 G. Converse time and time constant were set to be 40.96 and 20.48 ms, respectively.

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RESULTS Structure Description. The structure of the compound [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1) is composed of an asymmetric unit that contains one uranyl cation and one cobalt(II) cation located at the Wickoff position 1c (0, 1/2, 0) (Figure 1). The uranyl center is 7-fold coordinated with two uranyl bonds in apical positions [UOyl = 1.763(2)−1.766(2) Å] and five oxygen atoms in the pentagonal equatorial plane. Among the five oxygen atoms, four are carboxyl oxygen atoms [UOmel = 2.330(2)−2.439(2) Å], and one corresponds to the terminal aquo species [UOwater = 2.434(3) Å]. The cobalt(II) center is 6-fold coordinated with a typical octahedral environment defined by two carboxyl oxygen atoms in trans C


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Inorganic Chemistry

Figure 1. (Top) Representation of the asymmetric unit the compound [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1), showing the 7-fold coordinated uranyl cation and 6-fold coordinated cobalt(II) cation. (Bottom) View of the coordination mode of the mellitate ligand: yellow, uranium; pink, cobalt; red, carboxyl oxygen; blue, oxygen of water molecule; light orange, “yl” oxygen; gray, carbon from mellitate ligand.

position [Co−Omel = 2.100(2) Å] and by four water molecules [CoOwater = 2.085(3) Å]. Each carboxylate group of the mellitate ligand interacts with the cobalt cation following three types of connection mode (Figure 1). Two of the six carboxylate arms of the ligand adopt a heterometallic bidentate bridging mode involving the linkage between one uranyl cation and one cobalt(II) cation. The other carboxylate arms coordinate only the uranium centers. Among these carboxylate arms, two of them adopt a bidentate bridging mode, and two others adopt a monodentate bridging mode. The assembly of uranyl cations and mellitate ligands generates layers in plane (a, b) (Figure 2). The three-dimensional cohesion is ensured by the addition of cobalt(II) cations which connect the uranyl mellitate sheets (Figure 2). The hybrid heterometallic UO22+− Co2+ framework generates small cavities where water molecules are intercalated, presenting hydrogen bonding with water molecules connected to cobalt center [CoOw···Owfree = 3.3−3.9 Å] and uranyl oxo groups [UOyl···Owfree = 2.9−3.7 Å]. The single-crystal X-ray diffraction analysis reveals the presence of two free water molecules per uranyl cation. The compound [(UO2)Co(H2O)4(H2mel)]·2H2O (2) is an isotype of the heterometallic uranyl-zinc(II) coordination polymer.43 This structure is based on the assembly of mononuclear units of uranyl and cobalt(II) center, at the Wickoff position 1d (1/2, 0, 0) and 1b (0, 0, 1/2), respectively (Figure 3). The unique uranyl cation is 8-fold coordinated, with a typical hexagonal bipyramidal environment defined by two axial short uranyl bonds [UOyl = 1.760(2) Å] and six carboxyl oxygen atoms in the equatorial plane [UOmel = 2.437(2)−2.519(2) Å]. The cobalt(II) cation is octahedrally coordinated by two carboxyl oxygen atoms [CoOmel = 2.104(2) Å] located in trans positions and by four terminal aquo species [Co−Owater = 2.092(3)-2.106(3) Å]. The two metallic cations (UO22+ and Co2+) are linked to each other through one carboxylate arm of the mellitate ligand, which

Figure 2. (Top) View in the plane (a,b) of the uranyl mellitate layer in the structure of [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1). (Bottom) View of the structure of 1 in the plane (b, c) showing the connection between two uranyl mellitate layers through cobalt cations and the presence of water molecules inside the cavities.

adopts a heterometallic bidentate bridging mode. Four of the six carboxylate groups of the mellitate ligand interact with the uranyl centers; the remaining free carboxylic arms of the mellitate species interact through hydrogen bonds with water molecules trapped within the framework. This framework can be viewed as the connection of uranyl cations linked to each other via the mellitate ligands to generate layers in plane (a, b) (Figure 4). The three-dimensional cohesion is ensured by the addition of cobalt(II) cations which connect the mixed uranylmellitate sheets (Figure 4). This framework generates a small cavity where free water molecules are localized following a ratio of two free water molecules per uranyl cation. The free water molecules exhibit hydrogen bonding with water molecules coordinated to cobalt atoms [CoOw···Owfree = 3.50 Å], as well as with uranyl oxo groups [UOyl···Ow3 = 3.17 Å]. The structure of [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3) consists of a uranyl dinuclear unit and cobalt mononuclear unit (Figure 5). The uranium atom is 7-fold coordinated with a pentagonal bipyramidal environment defined by two axial uranyl bonds [UOyl = 1.754(5)−1.765(5) Å] and five oxygen atoms in the equatorial plane. Among the five atoms, two are hydroxyl groups [U−Ohydroxo = 2.299(4)−2.320(5) Å], and three are carboxyl oxygen atoms [U−Omel = 2.370(4)− D


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Inorganic Chemistry

Figure 3. (Top) Representation of the asymmetric unit in [(UO2)Co(H2O)4(H2mel)]·2H2O (2), showing the 8-fold coordinated uranyl cation and 6-fold coordinated cobalt cation. (Bottom) View of the coordination mode of the mellitate ligand: yellow, uranium; pink, cobalt; red, carboxyl oxygen; blue, oxygen of water molecule; light orange, “yl” oxygen; gray, carbon from mellitate ligand.

Figure 5. (Top) Representation of the asymmetric unit in [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3), showing the uranyl dimeric unit (7-fold coordinated) and 6-fold coordinated cobalt cation. (Bottom) View of the coordination mode of the mellitate ligand: yellow, uranium; pink, cobalt; red, carboxyl oxygen; blue, oxygen of water molecule; light orange, “yl” oxygen; orange, hydroxo group; gray, carbon from mellitate ligand.

2.390(4) Å]. The presence of the hydroxyl groups is confirmed by the bond valence calculation58 (1.21). Two uranyl cations share two hydroxyl groups to generate a usual configuration of a uranyl dinuclear unit (two 7-fold coordinated uranyl cations).8 The two cobalt(II) centers are located at the Wyckoff position 1g (0, 1/2, 1/2) and 1a (0, 1, 0). Each cobalt(II) atom is octahedrally coordinated by two carboxyl oxygen atoms [CoOmel = 2.112(4)−2.103(4) Å] located in trans positions and four terminal aquo species [CoOwater = 2.084(7)−2.115(5) Å]. Each uranyl dinuclear unit is linked to four cobalt(II) cations through four carboxylate arms of mellitate ligands, which adopts a heterometallic bidentate bridging mode. Another coordination mode is observed and corresponds to the monodentate mode. As for compounds 1 and 2, the structure is three-dimensional. Its 3D cohesion is ensured by the addition of cobalt cations, which connect the mixed uranyl-mellitate layers (Figure 6). This arrangement generates small cavities where water molecules (1H2O/ 1[UO2]) are intercalated. The compound [(UO2(H2O))2Co(H2O)4(mel)] (4) exhibits two crystallographically independent uranium atoms and two cobalt(II) atoms at the Wyckoff position 1a (0, 1, 0) and 1g (0, 1/2, 1/2) (Figure 7). The two independent uranium atoms adopt the same environment and are 7-fold coordinated, with a pentagonal bipyramidal environment defined by two axial short uranyl bonds [UOyl = 1.733(4)−1.762(4) Å] and

Figure 4. (Top) View in the plane (a, b) of the uranyl mellitate layer in the structure of [(UO2)Co(H2O)4(H2mel)]·2H2O (2). (Bottom) View of the structure of 2 in the plane (b, c) showing the connection between two uranyl mellitate layer through cobalt cations and the presence of water molecules inside the cavities. E


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Inorganic Chemistry

Figure 7. (Top) Representation of the asymmetric unit in [(UO2(H2O))2Co(H2O)4(mel)] (4), showing the metallic centers (uranyl, 7-fold coordinated; cobalt(II), 6-fold coordinated). (Bottom) View of the coordination mode of the mellitate ligand: yellow, uranium; pink, cobalt; red, carboxyl oxygen; blue, oxygen of water molecule; light orange, “yl” oxygen; gray, carbon from mellitate ligand.

ligands and uranyl cations, without any direct linkages with the cobalt centers. The hybrid network consists of the unique uranyl atom, which is 8-fold coordinated (Figure 9), with a typical hexagonal bipyramidal environment defined by two axial short uranyl bonds [UOyl = 1.759(2)−1.765(2) Å] and six carboxyl oxygen atoms in the equatorial plane [UOpht = 2.4381(19)−2.519(2) Å]. Two isophthalate ligands are crystallographically independent; each carboxylic arm of these two isophthalate ligands adopts a chelating mode. Previously, O’Hare et al. isolated a one-dimensional chain containing hexagonal bipyramidal UO8 units linked by isophthalate ligands, adopting a chelating mode.59 In our case, the hybrid uranyl-isophthaltate network [(UO2)(iso)3]2− is two-dimensional and generated small cavities where the cobalt atom is located at the Wyckoff position 4b (0, y, 1/4). This cobalt(II) center is 6-fold coordinated with a distorted octahedral environment defined with six water molecules [CoOwater = 2.066(2)−2.150(2) Å] (Figure 9). It promotes compensation of the negative charge of [(UO2)(iso)3]2−. Recently, Burns and Krivovichev published the structure of [Co(H2O)6][(UO2)5(SO4)8(H2O)](H2O)5 where the cobalt(II) cation plays also the role of countercation in the presence of uranyl sulfate sheets.60 The layers [(UO2)(iso)3][Co(H2O)6] are perpendicular to the c axis and are alternated by a rotation of 180° along the c axis between two adjacent layers (Figure 9). Water molecules are localized between the layers and ensure 3D dimensional cohesion by hydrogen bond interactions. Thermal Behavior. The thermogravimetric curve of [(UO 2 (H 2 O)) 2 Co(H 2 O) 4 (mel)]·4H 2 O (1) shows three weight-loss steps (Figure S10). Between room temperature and 200 °C, a first weight loss of 8.9% is observed and attributed to the evacuation of free water molecules (−4H2O) and two coordinated waters (−2H2O) (calcd 9.7% for 6H2O).

Figure 6. (Top) View in the plane (b, c) of the uranyl mellitate layer in the structure of [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3). (Bottom) View of the structure of 3 in the plane (a, c) showing the connection between two uranyl mellitate layer through cobalt(II) cations and the presence of water molecules inside the cavities.

four carboxyl oxygen atoms in the equatorial plane [UOmel = 2.324(4)−2.433(3) Å] and one terminal aqua group [U Owater = 2.443(4)−2.452(4) Å]. The two independent cobalt(II) atoms adopt a typical octahedral environment defined by four water molecules [CoOwater = 2.057(4)− 2.119(4) Å] and two carboxyl oxygen atoms in trans position [CoOmel = 2.062(4)−2.078(4) Å]. The connection mode observed for the mellitate ligand in compound 4 is similar to that observed in compound 1 (Figure 8). Contrary to the previous compounds (1, 2, and 3), the assembly of uranyl cations and mellitate ligands in phase 4 generates a 3D framework (for compounds 1, 2, and 3, it is a 2D framework). The cobalt cations are located within the cavity of the 3D framework, and no free hydration water is observed. The assembly of uranyl cations and cobalt(II) cations in the compound [(UO2)(iso)3][Co(H2O)6]·3(H2O) (5) differs from the four structures previously described. In fact, the infinite network of 5 is based on the assembly of isophthalate F


Article

Inorganic Chemistry

(−6H2O), associated with a weight loss of 13.8% (calcd 13.9%) between 100 and 190 °C. It is followed by a plateau up to 330 °C, which is assigned to the anhydrous form of as-synthesized compound “[(UO2)Co(H2mel)]”. The second weight loss starts from 330 °C and corresponds to the decomposition of the organic part. The remaining weight value is constant between 410 and 800 °C, and it is 47.3% of the original value. It fits well with the theoretical value (46.6%) based on a stoichiometric mixture of 1/3CoU3O10 + 2/3CoO. A similar thermal decomposition was previously reported with the (UO2)Zn(H2O)4(H2mel)·2H2O.35 The thermodiffractogram of [(UO2)Co(H2O)4(H2mel)]· 2H2O (2) indicated the disappearance of the Bragg peaks of 2 when the sample was heated up to 120 °C (Figure S8). Between 140 and 340 °C, a new set of Bragg peaks is observed. Subsequently, the sample transforms into a cobalt oxide Co3O4 (PDF number 42-1467). The formation of oxides α-CoU3O10 (PDF number 46-0929) was observed at 560 °C, followed by the formation of CoUO4 (PDF number 16-0833) from 640 °C. The thermogravimetric curve of [(UO 2 (H 2 O)) 2 Co(H2O)4(mel)] (4) shows four weight-loss steps (Figure S12). The first event is a continuous weight loss between room temperature and 130 °C. It is assigned to the evacuation of one water molecule (obsd 2.1%; calcd 1.7%). Between 130 and 190 °C, a second weight loss is observed and is attributed to the departure of two water molecules (obsd 3.6%; calcd 3.4%). The third thermal event is a weight loss between 220 and 300 °C. It corresponds to the completed dehydration of the compound (−3H2O) (obsd 4.8%; calcd 5.1%). The last weight loss starts from 330 °C and corresponds to the decomposition of the mellitate ligand. The remaining weight value is 61.5% of the original value, and it fits well with the theoretical value (62.0%) based on a stoichiometric mixture of 2/3CoU3O10 + 1/3CoO. The thermodiffractogram of [(UO 2 (H 2 O)) 2 Co(H2O)4(mel)] (4) showed that the phase is stable up to 120 °C (Figure S9). Beyond 140 °C, a new set of Bragg peaks is observed up to 220 °C. Then, the thermal evolution of the powder XRD patterns indicated a structural transformation into the amorphous phase between 240 and 500 °C. From 500 °C, we note the appearance of two unassigned peaks at 25.3 and 25.8 which remain until 800 °C. At the same time, the crystallization of α-CoU3O10 (PDF number 46-0929) occurs, and precedes the formation of CoUO4 (PDF number 16-0833) at 700 °C. Structure Description of the Dehydrated Phases 1′ and 2′. Crystal structures of the dehydrated phases 1 and 2 have been determined by single-crystal XRD analyses from samples heated at 180 °C in an oven. The collection of the XRD intensities has been carried out at room temperature since dehydration process is irreversible. A partially hydrated form of compound 1 has been isolated after heating crystals at 180 °C in air for 30 min. It is correlated to the loss of 6H2O/(UO2)2 as observed from the first plateau in the thermogravimetric curve (Figure S10). The resulting phase [(UO2(H2O))2Co(H2O)2(mel)] (1′) exhibits a trinuclear motif “U2Co” in which one central cobalt(II)-centered unit is linked to two peripheral uranyl units (Figure 10). The asymmetric building unit consists of one crystallographic uranyl center and one crystallographic cobalt(II) center. The unique uranium atom is 7-fold coordinated with a pentagonal bipyramidal environment defined by two axial uranyl bond [UOyl = 1.754(2) Å and 1.796(2) Å]. The equatorial plane is composed of four carboxyl oxygen atoms [UOmel =

Figure 8. (Top) View in the plane (b, c) of the uranyl mellitate layer in the structure of [(UO2(H2O))2Co(H2O)4(mel)] (4). (Bottom) View of the structure of 4 in the plane (b, c) showing the intercalation of cobalt(II) cations inside the cavities of the uranyl-mellitate framework.

The second step is observed between 230 and 390 °C, and assigned to complete dehydration of the solid (obsd 17.2%; calcd 16.1%). The third weight loss starts from 390 °C and corresponds to the evacuation of the organic part. The remaining weight value is 59.9% of the original value and agrees with the theoretical value (calcd 58.0%) based on a stoichiometric mixture of 2/3CoU3O10 + 1/3CoO. The t hermodiffractogram of [(UO 2 (H 2 O)) 2 Co(H2O)4(mel)]·4H2O (1) indicated the disappearance of the Bragg peaks of 1 when the sample was heated up to 60 °C (Figure S7). Between 80 and 240 °C, a new set of Bragg peaks is observed. Subsequently, the sample transforms into an amorphous phase, and recrystallization is observed from 460 °C, with the formation of oxides α-CoU3O10 (PDF number 460929), followed by the formation of CoUO4 (PDF number 160833) from 640 °C. The thermogravimetric curve of [(UO2)Co(H2O)4(H2mel)]· 2H2O (2) shows two weight-loss steps (Figure S2). The first event is assigned to the departure of free and coordinated water G


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Inorganic Chemistry

Figure 9. (Top) Representation of the asymmetric unit in the compound [(UO2)(iso)3][Co(H2O)6]·3(H2O) (5), showing the 8-fold coordinated uranyl cation and 6-fold coordinated cobalt cation: yellow, uranium; pink, cobalt; red, carboxyl oxygen; blue, oxygen of water molecule; light orange, “yl” oxygen; gray, carbon from mellitate ligand. (Bottom) View of the structure of 5 in the plane (b, c).

uranyl center, the environment cobalt(II) center is drastically modified after the departure of two water molecules. The cobalt(II) cation located at the Wyckoff position 1a (0, 1, 0) is octahedrally coordinated by two carboxyl oxygen atoms [Co1Omel = 2.059(2) Å], two terminal aquo species [Co Owater = 2.062(3) Å], and two “yl” oxygen atoms from two distinct uranyl cations [CoOyl = 2.192(2) Å]. The oxygen atoms of uranyl dioxo-cation (UO22+) are rarely engaged with other metallic cations. Nevertheless, some cases of heterometallic interactions (MOU) are reported in coordination polymers with divalent transition metals such as Mn2+,16,18 Co2+,15,16 Cu2+,14,20,26,36,37 Zn2+,61 and Cd2+.16 The distances CoO and UO observed in compound 1′ are close to the distances observed previously in the literature (UO; Co O).15,16 They have an impact on the uranyl UOyl bond length: the free uranyl UOyl bond distance is 1.754(2) Å since the second uranyl UOyl bond distance is 1.796(2) Å, but it is also involved in the CoOyl linkage. The structural transition 1 → 1′ was followed by in situ infrared spectroscopy. It showed the shifting of the asymmetric vibration of the U Oyl bond (Figure S16) confirming the variation of the UOyl bond length. From the vasym(UO) and the empirical formula

Figure 10. Representation of the trinuclear brick “U2Co” in [(UO2(H2O))2Co(H2O)2(mel)] (1′), showing cation−cation interactions type between metallic centers (uranyl, 7-fold coordinated; cobalt(II), 6-fold coordinated): yellow, uranium; pink, cobalt; red, carboxyl oxygen; blue, oxygen of water molecule; light orange, “yl” oxygen; gray, carbon from mellitate ligand.

2.336(2)−2.445(2) Å] and one water molecule [UOwater = 2.462(2) Å]. The coordination sphere of the uranyl cation in the phase 1′ is identical to that of compound 1 and is unchanged during the partial dehydration. Contrary to the H


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Inorganic Chemistry

Figure 11. (Top) Comparison of the coordination mode of mellitate ligand in [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1; left) and [(UO2(H2O))2Co(H2O)2(mel)] (1′; right). (Bottom) Comparison of the structure of 1 (left) and 1′ (right) in the plane (b,c).

Figure 12. (Top) Representation of the dinuclear building unit in [(UO2)Co(H2mel)] (2′), showing the cation−cation interactions between metallic centers (uranyl, 7-fold coordinated; cobalt(II), 5-fold coordinated): yellow, uranium; pink, cobalt; red, carboxyl oxygen; light orange, “yl” oxygen; gray, carbon from mellitate ligand. (Bottom) View of the structure of 2′ in the plane (a, b).

defined by Bartlett and Cooney,62 the calculated UOyl bond length through IR data (1.759 and 1.783 Å) is in agreement with that found in the crystallographic data (1.754(2) and

1.796(2) Å). The coordination mode of mellitate ligand is modified during the transition phase 1 → 1′ (Figure 11). In fact, after heating, the two monodentate carboxylate functions I


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Inorganic Chemistry

Figure 13. Comparison of the coordination mode of mellitate ligand in [(UO2)Co(H2O)4(H2mel)]·2H2O (2; left) and [(UO2)Co(H2mel)] (2′; right).

1.782 Å. These UOyl bond lengths are in agreement with the UOyl bond lengths observed in the XRD data. To our knowledge, the square pyramidal configuration for cobalt cation is rarely observed in the carboxylate crystal chemistry. This environment has been previously observed in the two coordination polymers [Co 6 (C 4 H 4 O 4 ) 5 ]·H 2 O 6 4 and [Co3(C8H4O4)2(OH)2(C12H8N2)2],65 for which two types of coordination are reported (octahedral and square bipyramidal configurations). However, to our knowledge, compound 2′ is the first example of a coordination polymer, in which cobalt(II) cations adopt only the square pyramidal geometry. As previously observed for the transition phase 1 → 1′, the coordination mode of mellitate ligand is changed during the dehydration of phase 2 (Figure 13). In the dehydrated compound 2′, four carboxylate arms adopt a heterometallic bidentate coordination mode against only two in the compound before heating (2). As the compound (2′), the assembly of uranyl and mellitate ligand promotes the formation of sheets in the plane (b, c), and the three-dimensional cohesion is ensured by the addition of cobalt(II) cations. The phase transition 2 → 2′ induces the volume shrinkage (−23.5%) and the increase of the density (+14.2%). We have also observed that the transition phase exists with a color change of the powdered sample from orange (hydrated form) to green (dehydrated form) (Figure S18). These different colors are probably due to the modification of cobalt environment (CoO6 → CoO5). EPR data displayed in Figure 14 show a high spin state S = 3 /2 for complex 2, with observed (effective) g values of gx = 6.37, gy = 3.92, and gz = 2.15, indicating the dipolar term of the ZFS tensor D is higher than hv. After the thermal treatment at 180 °C, no spin state change for the Co2+ moiety was observed, but with different g values gx= 5.93, gy= 3.15, and gz = 2.04. These changes in the g values indicate a modification of the coordination sphere in keeping with the geometry evolution from octahedral to distorted square pyramidal configurations, as deduced from the crystal structures.

of 1 adopt two heterometallic bidentate coordination modes in compound 1′. Moreover, the two carboxylate arms adopting a heterometallic bidentate coordination mode in phase 1 become monodendate in 1′. The assembly of uranyl cations and mellitate ligands in compound 1′ generates layers in the plane (a, b) identical to those reported in compound 1 before the dehydration (Figure 11). The three-dimensional cohesion is ensured by the cobalt(II) cations linking two layers. We observed a volume contraction (−23.9%) together with the increase of the density (+19.8%) during the dehydration of 1. The fully dehydrated form of compound 2 has been stabilized after heating the crystals in air at 180 °C for 30 min. It corresponds to the loss of 6H2O/(UO2), correlated to the observation of the plateau from 180 °C in the thermogravimetric curve (Figure S11). Its crystal structure ([(UO2)Co(H2mel)], 2′) shows heterometallic bridging oxo groups between the uranyl and cobalt(II) centers (Figure 12). It consists of two crystallographic metallic centers at a special position (2a). The uranium atom is 7-fold coordinated with a pentagonal bipyramidal environment defined by two axial short uranyl bonds [UOyl = 1.76(2) Å and 1.788(16) Å] and five carboxyl oxygen atoms in equatorial plane [UOmel = 2.21(2)−2.62(3) Å]. The cobalt(II) center is 5-fold coordinated with a distorted square pyramidal environment defined by four carboxyl atom in the distorted square plane [CoOmel = 1.90(3)−2.14(2) Å] and one “yl” oxygen in the apical position [Co−Oyl = 2.134(18) Å]. The bond valence calculation63 confirms the divalent oxidation state for the cobalt cations (1.99). As for 1 → 1′, the structural transformation is correlated to the formation of heterometallic interaction between uranyl bond and the cobalt center, with the occurrence of a UOCo bond. The bond length of the uranyl bond UOyl involved in the CoOyl linkage is 1.788(16) Å, while the free uranyl UOyl bond distance is 1.76(2) Å. The variation of asymmetric vibration of the UOyl bond during the structural transition 2 → 2′ was followed by in situ infrared (Figure S17). Using the formula of Bartlett and Cooney,62 the calculated UOyl bond distances are 1.750 and J


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Inorganic Chemistry

with a saturation value of 2.5 NμB, in the lower range of values observed in the literature for 6-coodinated Co2+ ions.70−74

Figure 14. CW EPR spectra of compound 2 and 2′ recorded at 5 K.

Magnetism. The temperature variations of the magnetic susceptibility of compounds 2 and 2′ are shown in Figure 15.

Figure 16. Magnetization versus field variation of compounds 2 and 2′ recorded at 1.8 K.

After heating above 180 °C, compound 2′ exhibits a quasiconstant value of χT(T) between room temperature and 100 K with the 1/χ versus T curve being linear in the whole temperature range (Figure S20). The fit to the Curie−Weiss law gives C = 2.8 K cm3 mol−1 and θ = −5 K. The thermal variation of the magnetic susceptibility is thus typical of isolated S = 3/2 Co2+ ions with a quenched orbital moment, due to lower symmetry. The Curie constant value is quite high, in agreement with the high g value deduced from the EPR spectroscopy spectra. The slight decrease at low temperature can be ascribed to the zero-field splitting effect arising for single ion anisotropy (D) as already reported for Co2+ ions in nonoctahedral sites.75,76 Such anisotropy agrees with the anisotropy of the g tensor found by EPR spectroscopy. Finally, the magnetization versus field curve at 1.8 K saturating at 2.85NμB is consistent with S = 3/2 spins moments (expected 3NμB).

Figure 15. Magnetic susceptibility variation of compounds 2 and 2′as χT vs T plots.

The susceptibility of compounds 2 and 2′ was measured from 1.8 to 300 K in low dc field (≤1000 Oe). In addition, we observed the magnetic susceptibility is similar before and after heating up to 400 K indicating that the compound is stable up this temperature. The magnetic susceptibility of both compounds exhibits a steady increase between room temperature and 1.8 K, consistent with paramagnetic behavior. The χT versus T plot curves of 2 shows a decrease between 3.15 K cm3 mol−1 at high temperature and 1.8 K cm3 mol−1 at 1.8 K. The uranyl species are known to be diamagnetic or exhibit weak temperature independent paramagnetism.66 Hence, the magnetic behavior is essentially due to the cobalt(II) ions present in 2. In the octahedral environment, the Co2+ ions behave as S = 3/2, L = 1 ions, exhibiting a spin−orbit coupling that splits the J = ±5/2, ±3/2, ±1/2 levels. Decreasing the temperature induces the depopulation of the excited states in favor of the doublet ground state, which results in the decrease of the effective moment.67−69 Actually, the χT versus T curve of 2 corresponds well to that predicted for Co2+ in an octahedral site.68,69 Indeed, we have fit the high temperature 1/χ versus T curve, which is linear above T = 120 K, to the Curie−Weiss law: χ = C/(T − θ). Here, C and θ are the Curie constant and the Weiss temperature, respectively. The best parameters for 2, C = 3.4 K cm3 mol−1 and θ = −19 K, are in the expected range from the literature68,70−72 (Figure S19). In addition, the low temperature value of χT = 1.8 K cm3 mol−1 is in keeping with a quite weak crystal field.67−69 Consistently, the magnetization versus field curve, shown in Figure 16, indicates a paramagnetic behavior

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CONCLUSION This contribution dealt with the hydrothermal synthesis and structural characterization of different heterometallic uranylcobalt(II) coordination complexes involving two distinct aromatic carboxylates (isophthalate and mellitate). In this series, their crystal structures are built up from uranyl-centered blocks (mononuclear or dinuclear unit), linked through the carboxylate molecules and isolated cobalt centers. The use of the mellitate ligand promotes the formation of three-dimensional frameworks rather than the isophthalate linker favoring the formation of a two-dimensional framework. This work underlines the ability to form the heterometallic uranyl−Co(II) coordination polymers with aromatic carboxylate ligand. This study and our previous papers on the formation of heterometallic uranyl−M2+ complex (M = Cu37 and Zn43) show that the hydrothermal reaction of uranyl nitrate and metallic transition metal (TM) with aromatic polycarboxylate ligands is an easy method for the isolation of heterometallic uranyl−TM2+ hybrid materials. The second aspect of this study concerned the thermal behavior of the heterometallic uranyl-Co(II) coordination polymers. The thermal behavior of the pure phases was investigated by thermogravimetric analysis, in situ infrared analysis, and X-ray thermodiffraction. At low temperature (between 80 to 140 °C) the dehydration process of K


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Inorganic Chemistry

(3) Knope, K. E.; Soderholm, L. Solution and Solid-State Structural Chemistry of Actinide Hydrates and Their Hydrolysis and Condensation Products. Chem. Rev. 2013, 113, 944−994. (4) Suzuki, Y.; Kelly, S. D.; Kemner, K. M.; Banfield, J. F. Radionuclide contamination: Nanometre-size products of uranium bioreduction. Nature 2002, 419, 134−134. (5) Buffle, J.; Greter, F. L.; Haerdi, W. Measurement of complexation properties of humic and fulvic acids in natural waters with lead and copper ion-selective electrodes. Anal. Chem. 1977, 49, 216−222. (6) Robl, C.; Kuhs, W. F. A neutron diffraction study on hydrogen bonding in the mineral mellite (Al2[C6(COO)6]•16H2O) at 15 K. J. Solid State Chem. 1991, 92, 101−109. (7) Zhou, H. C.; Long, J. R.; Yaghi, O. M. Chem. Rev. 2012, 112, 673−1268. (8) Loiseau, T.; Mihalcea, I.; Henry, N.; Volkringer, C. The crystal chemistry of uranium carboxylates. Coord. Chem. Rev. 2014, 266−267, 69−109. (9) Andrews, M. B.; Cahill, C. L. Uranyl Bearing Hybrid Materials: Synthesis, Speciation, and Solid-State Structures. Chem. Rev. 2013, 113, 1121−1136. (10) Wang, K.-X.; Chen, J.-S. Extended Structures and Physicochemical Properties of Uranyl−Organic Compounds. Acc. Chem. Res. 2011, 44, 531−540. (11) Yang, W.; Wu, D.; Liu, C.; Pan, Q.-J.; Sun, Z.-M. Structural Variations of the First Family of Heterometallic Uranyl Carboxyphosphinate Assemblies by Synergy between Carboxyphosphinate and Imidazole Ligands. Cryst. Growth Des. 2016, 16, 2011−2018. (12) Knope, K. E.; de Lill, D. T.; Rowland, C. E.; Cantos, P. M.; de Bettencourt-Dias, A.; Cahill, C. L. Uranyl Sensitization of Samarium(III) Luminescence in a Two-Dimensional Coordination Polymer. Inorg. Chem. 2012, 51, 201−206. (13) Knope, K. E.; Cahill, C. L. Synthesis and Characterization of 1-, 2-, and 3-Dimensional Bimetallic UO22+/Zn2+ Phosphonoacetates. Eur. J. Inorg. Chem. 2010, 2010, 1177−1185. (14) Alsobrook, A. N.; Zhan, W.; Albrecht-Schmitt, T. E. Use of Bifunctional Phosphonates for the Preparation of Heterobimetallic 5f− 3d Systems. Inorg. Chem. 2008, 47, 5177−5183. (15) Alsobrook, A. N.; Hauser, B. G.; Hupp, J. T.; Alekseev, E. V.; Depmeier, W.; Albrecht-Schmitt, T. E. From Layered Structures to Cubic Frameworks: Expanding the Structural Diversity of Uranyl Carboxyphosphonates via the Incorporation of Cobalt. Cryst. Growth Des. 2011, 11, 1385−1393. (16) Alsobrook, A. N.; Hauser, B. G.; Hupp, J. T.; Alekseev, E. V.; Depmeier, W.; Albrecht-Schmitt, T. E. Cubic and rhombohedral heterobimetallic networks constructed from uranium, transition metals, and phosphonoacetate: new methods for constructing porous materials. Chem. Commun. 2010, 46, 9167−9169. (17) Alsobrook, A. N.; Alekseev, E. V.; Depmeier, W.; AlbrechtSchmitt, T. E. Uranyl carboxyphosphonates that incorporate Cd(II). J. Solid State Chem. 2011, 184, 1195−1200. (18) Alsobrook, A. N.; Alekseev, E. V.; Depmeier, W.; AlbrechtSchmitt, T. E. ncorporation of Mn(II) and Fe(II) into Uranyl Carboxyphosphonates. Cryst. Growth Des. 2011, 11, 2358−2367. (19) Adelani, P. O.; Albrecht-Schmitt, T. E. Heterobimetallic Copper(II) Uranyl Carboxyphenylphosphonates. Cryst. Growth Des. 2011, 11, 4676−4683. (20) Cahill, C. L.; de Lill, D. T.; Frisch, M. Homo- and heterometallic coordination polymers from the f elements. CrystEngComm 2007, 9, 15−26. (21) Frisch, M.; Cahill, C. L. Synthesis, structure and fluorescent studies of novel uranium coordination polymers in the pyridinedicarboxylic acid system. Dalton Trans. 2006, 4679−4690. (22) Kerr, A. T.; Cahill, C. L. CuPYDC Metalloligands and Postsynthetic Rearrangement/Metalation as Routes to Bimetallic Uranyl Containing Hybrid Materials: Syntheses, Structures, and Fluorescence. Cryst. Growth Des. 2014, 14, 4094−4103. (23) Kerr, A. T.; Cahill, C. L. Postsynthetic Rearrangement/ Metalation as a Route to Bimetallic Uranyl Coordination Polymers:

heterometallic uranyl−Co(II) coordination polymers is observed and involves a structural transition. The crystal structures of two dehydrated phases have been determined by single-crystal X-ray diffraction and reveal the formation of CoOU interactions. This study gives another illustration of the reactivity of the “yl” oxygen atoms of the uranyl cation with the divalent cations. Moreover, during the study of the thermal behavior of phase 2, we have observed that the phase transition 2 → 2′ induces the modification of the cobalt environment (CoO6 → CoO5) and the formation of CoOU interactions. Due to this rare coordination sphere for the cobalt(II) cations (distorted square pyramidal environment), the magnetic properties of the compounds before (2) and after (2′) the dehydration process have been investigated. The magnetic data support the structural features. The EPR spectra are characteristic of S = 3 /2 ions. The change in the anisotropic g tensor between 2 and 2′ is in keeping with the structural modification observed above 180 °C (453 K), concerning the cobalt environment. The thermal variations of the magnetic susceptibility and the magnetization versus field curves of 2 and 2′ are fully consistent with the related modification of the crystal field geometry around the cobalt ions.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01697. Additional figures (PDF) Crystallographic data for 2 (CIF) Crystallographic data for 4 (CIF) Crystallographic data for 5 (CIF) Crystallographic data for 1 (CIF) Crystallographic data for 1′ (CIF) Crystallographic data for 2′ (CIF) Crystallographic data for 3 (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: (33) 3 20 434 973. Fax: (33) 3 20 43 48 95. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to acknowledge Mrs. Nora Djelal & Laurence Burylo for their technical assistance with the SEM images, TG measurements, and powder XRD (UCCS). The Chevreul Institute (FR 2638), Fonds Européen de Développement Régional (FEDER), CNRS, Région Nord Pas-de-Calais, and Ministère de l’Education Nationale de l’Enseignement Supérieur et de la Recherche are acknowledged for funding of the X-ray diffractometers. C.F. acknowledges Université Lille 1 and Région Nord Pas-de-Calais for his Ph.D. grant support.

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REFERENCES

(1) Geckeis, H.; Lützenkirchen, J.; Polly, R.; Rabung, T.; Schmidt, M. Mineral−Water Interface Reactions of Actinides. Chem. Rev. 2013, 113, 1016−1062. (2) Qiu, J.; Burns, P. C. Clusters of Actinides with Oxide, Peroxide, or Hydroxide Bridges. Chem. Rev. 2013, 113, 1097−1120. L


Article

Inorganic Chemistry Syntheses, Structures, and Luminescence. Cryst. Growth Des. 2014, 14, 1914−1921. (24) Mei, L.; Wu, Q.-y.; An, S.-w.; Gao, Z.-q.; Chai, Z.-f.; Shi, W.-q. Silver Ion-Mediated Heterometallic Three-Fold Interpenetrating Uranyl−Organic Framework. Inorg. Chem. 2015, 54, 10934−10945. (25) Serezhkina, L. B.; Vologzhanina, A. V.; Novikov, S. A.; Korlyukov, A. A.; Serezhkin, V. N. Synthesis and crystal structure of [UO2CrO4(C5NH5COO)2(H2O)]·2H2O. Crystallogr. Rep. 2011, 56, 233−237. (26) Thuéry, P. Two uranyl−organic frameworks with pyridinecarboxylate ligands. A novel heterometallic uranyl−copper(II) complex with a cation−cation interaction. Inorg. Chem. Commun. 2009, 12, 800−803. (27) Liao, Z.-L.; Li, G.-D.; Bi, M.-H.; Chen, J.-S. Preparation, Structures, and Photocatalytic Properties of Three New Uranyl− Organic Assembly Compounds. Inorg. Chem. 2008, 47, 4844−4853. (28) Yu, Z.-T.; Liao, Z.-L.; Jiang, Y.-S.; Li, G.-H.; Chen, J.-S. WaterInsoluble Ag−U−Organic Assemblies with Photocatalytic Activity. Chem. - Eur. J. 2005, 11, 2642−2650. (29) Thuery, P.; Harrowfield, J. Uranyl Ion Complexes with LongChain Aliphatic alpha,omega-Dicarboxylates and 3d-Block Metal Counterions. Inorg. Chem. 2016, 55, 2133−2145. (30) Thuery, P.; Harrowfield, J. Counter-ion control of structure in uranyl ion complexes with 2,5-thiophenedicarboxylate. CrystEngComm 2016, 18, 1550−1562. (31) Thuéry, P.; Rivière, E.; Harrowfield, J. Uranyl and Uranyl−3d Block Cation Complexes with 1,3-Adamantanedicarboxylate: Crystal Structures, Luminescence, and Magnetic Properties. Inorg. Chem. 2015, 54, 2838−2850. (32) Thuéry, P.; Harrowfield, J. Uranyl Ion Complexes with 1,1′Biphenyl-2,2′,6,6′-tetracarboxylic Acid: Structural and Spectroscopic Studies of One- to Three-Dimensional Assemblies. Inorg. Chem. 2015, 54, 6296−6305. (33) Thuery, P. Uranyl-3d block metal ion heterometallic carboxylate complexes including additional chelating nitrogen donors. CrystEngComm 2013, 15, 6533−6545. (34) Frisch, M.; Cahill, C. L. Syntheses, structures and fluorescent properties of two novel coordination polymers in the U-Cu-H3pdc system. Dalton Trans. 2005, 1518−1523. (35) Guan, Q. L.; Gao, X.; Liu, J.; Wei, W. J.; Xing, Y. H.; Bai, F. Y. UO22+-polycarboxylate heterometallic complexes: structure, spectra, and photocatalytic properties. J. Coord. Chem. 2016, 69, 1026−1038. (36) Liang, L.; Cai, Y.; Li, X.; Zhang, R.; Zhao, J.; Liu, C.; Seik Weng, N. Two Uranyl Complexes with Pyromellitic Acid. A Heterometallic Complex with UO−CuII Interaction. Z. Anorg. Allg. Chem. 2015, 641, 1744−1748. (37) Olchowka, J.; Falaise, C.; Volkringer, C.; Henry, N.; Loiseau, T. Structural Observations of Heterometallic Uranyl Copper(II) Carboxylates and Their Solid-State Topotactic Transformation upon Dehydration. Chem. - Eur. J. 2013, 19, 2012−2022. (38) Thuery, P. Uranyl citrate dimers as guests in a copper-bipyridine framework: a novel heterometallic inorganic-organic hybrid compound. CrystEngComm 2007, 9, 358−360. (39) Thuéry, P. Increasing Complexity in the Uranyl Ion−Kemp’s Triacid System: From One- and Two-Dimensional Polymers to Uranyl−Copper(II) Dodeca- and Hexadecanuclear Species. Cryst. Growth Des. 2014, 14, 2665−2676. (40) Thuéry, P.; Harrowfield, J. Uranyl Ion Complexes with trans-3(3-Pyridyl)acrylic Acid Including a Uranyl−Copper(II) Heterometallic Framework. Eur. J. Inorg. Chem. 2014, 2014, 4772−4778. (41) Weng, Z.; Zhang, Z.-h.; Olds, T.; Sterniczuk, M.; Burns, P. C. Copper(I) and Copper(II) Uranyl Heterometallic Hybrid Materials. Inorg. Chem. 2014, 53, 7993−7998. (42) Yang, W.; Dang, S.; Wang, H.; Tian, T.; Pan, Q.-J.; Sun, Z.-M. Synthesis, Structures, and Properties of Uranyl Hybrids Constructed by a Variety of Mono- and Polycarboxylic Acids. Inorg. Chem. 2013, 52, 12394−12402. (43) Olchowka, J.; Volkringer, C.; Henry, N.; Loiseau, T. Synthesis, Structural Characterization, and Dehydration Analysis of Uranyl Zinc

Mellitate, (UO2)Zn(H2O)4(H2mel)·2H2O. Eur. J. Inorg. Chem. 2013, 2013, 2109−2114. (44) Volkringer, C.; Henry, N.; Grandjean, S.; Loiseau, T. Uranyl and/or Rare-Earth Mellitates in Extended Organic−Inorganic Networks: A Unique Case of Heterometallic Cation−Cation Interaction with UVIO−LnIII Bonding (Ln = Ce, Nd). J. Am. Chem. Soc. 2012, 134, 1275−1283. (45) Thuéry, P.; Harrowfield, J. Two-dimensional assemblies in felement ion (UO22+, Yb3+) complexes with two cyclohexyl-based polycarboxylates. Polyhedron 2015, 98, 5−11. (46) Thuéry, P. A Lanthanide Ion-Decorated Uranyl−Organic TwoDimensional Assembly with all-cis 1,2,3,4,5,6-Cyclohexanehexacarboxylic Acid. Cryst. Growth Des. 2010, 10, 2061−2063. (47) Mihalcea, I.; Volkringer, C.; Henry, N.; Loiseau, T. Series of Mixed Uranyl−Lanthanide (Ce, Nd) Organic Coordination Polymers with Aromatic Polycarboxylates Linkers. Inorg. Chem. 2012, 51, 9610− 9618. (48) Hou, Y.-N.; Xu, X.-T.; Xing, N.; Bai, F.-Y.; Duan, S.-B.; Sun, Q.; Wei, S.-Y.; Shi, Z.; Zhang, H.-Z.; Xing, Y.-H. Photocatalytic Application of 4f−5f Inorganic−Organic Frameworks: Influence of Lanthanide Contraction on the Structure and Functional Properties of a Series of Uranyl−Lanthanide Complexes. ChemPlusChem 2014, 79, 1304−1315. (49) Cantos, P. M.; Pope, S. J. A.; Cahill, C. L. An exploration of homo- and heterometallic UO22+ hybrid materials containing chelidamic acid: synthesis, structure, and luminescence studies. CrystEngComm 2013, 15, 9039−9051. (50) Klepov, V. V.; Peresypkina, E. V.; Serezhkina, L. B.; Karasev, M. O.; Virovets, A. V.; Serezhkin, V. N. Crystal structure of [M(H2O)6][UO2(CH3COO)3]2 (M = Mg2+, Co2+ and Zn2+). Polyhedron 2013, 61, 137−142. (51) Zhang, Y.; Collison, D.; Livens, F. R.; Helliwell, M.; Heatley, F.; Powell, A. K.; Wocadlo, S.; Eccles, H. Synthesis and characterisation of uranyl substituted malonato complexes: Part II: 13C CPMAS NMR spectroscopy related to structural diversity. Polyhedron 2002, 21, 81− 96. (52) Zhang, Y.; Collison, D.; Livens, F. R.; Helliwell, M.; Eccles, H.; Tinker, N. Structural studies on monomeric and dimeric uranyl bis(dimethylmalonato)complexes. J. Alloys Compd. 1998, 271−273, 139−143. (53) Burns, P. C.; Finch, R. J. Uranium: Mineralogy, Geochemistry and the Environment; Mineralogical Society of America, 1999. (54) SAINT, SAINT Plus Version 7.53a; Bruker Analytical X-ray Systems: Madison, WI, 2008. (55) Heldrick, G. SADABS, Bruker-Siemens Area Detector Absorption and Other Correction, Version 2008/1; 2008. (56) Sheldrick, G. A short history of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112−122. (57) Farrugia, L. WinGX suite for small-molecule single-crystal crystallography. J. Appl. Crystallogr. 1999, 32, 837−838. (58) Burns, P. C.; Ewing, R. C.; Hawthorne, F. C. The crystal chemistry of hexavalent uranium: polyhedron geometries, bondvalence parameters, and polymerization of polyhedra. Can. Mineral. 1997, 35, 1551−1570. (59) Kim, J.-Y.; Norquist, A. J.; O’Hare, D. Incorporation of uranium(vi) into metal-organic framework solids, [UO2(C4H4O4)]· [UO2F(C5H6O4)]·2H2O, and H2O, [(UO2)1.5(C8H4O4)2]2[(CH3)2NCOH2]·H2O. Dalton Trans. 2003, 2813−2814. (60) Krivovichev, S. V.; Burns, P. C. The modular structure of the novel uranyl sulfate sheet in [Co(H2O)6]3[(UO2)5(SO4)8(H2O)](H2O)5. J. Geosci. 2014, 59, 135−143. (61) Chen, W.; Yuan, H.-M.; Wang, J.-Y.; Liu, Z.-Y.; Xu, J.-J.; Yang, M.; Chen, J.-S. Synthesis, Structure, and Photoelectronic Effects of a Uranium−Zinc−Organic Coordination Polymer Containing Infinite Metal Oxide Sheets. J. Am. Chem. Soc. 2003, 125, 9266−9267. (62) Bartlett, J. R.; Cooney, R. P. On the determination of uranium oxygen bond lengths in dioxouranium(VI) compounds by Raman spectroscopy. J. Mol. Struct. 1989, 193, 295−300. M


Article

Inorganic Chemistry (63) Brown, I. D.; Altermatt, D. Acta Crystallogr., Sect. B: Struct. Sci. 1985, B41, 244−247. (64) Long, L.-S.; Chen, X.-M.; Tong, M.-L.; Sun, Z.-G.; Ren, Y.-P.; Huang, R.-B.; Zheng, L.-S. A unique open inorganic-organic framework with alternate hexa- and penta-coordinate cobalt(ii) sites. Synthesis, crystal structure and magnetic properties of [Co3(C4H4O4)2.5(OH)]n·0.5nH2O. J. Chem. Soc., Dalton Trans. 2001, 2888−2890. (65) Zhang, L.-J.; Zhao, X.-L.; Cheng, P.; Xu, J.-Q.; Tang, X.; Cui, X.B.; Xu, W.; Wang, T.-G. A Unique Two-Dimensional TerephthalateBridged Structure with Alternate Tetra- and Penta-Coordinate Cobalt(II) Sites. Synthesis, Crystal Structure and Magnetic Properties of [{Co3(tp)2(OH)2(phen)2}n]. Bull. Chem. Soc. Jpn. 2003, 76, 1179− 1184. (66) Eisenstein, J. C.; Pryce, M. H. L. The Electronic Structure and Magnetic Properties of Uranyl-Like Ions. I. Uranyl and Neptunyl. Proc. R. Soc. London, Ser. A 1955, 229, 20−38. (67) Figgis, B. N.; Gerloch, M.; Lewis, J.; Mabbs, F. E.; Webb, G. A. The magnetic behaviour of cubic-field 4T1g terms in lower symmetry. J. Chem. Soc. A 1968, 2086. (68) Lloret, F.; Julve, M.; Cano, J.; Ruiz-García, R.; Pardo, E. Magnetic properties of six-coordinated high-spin cobalt(II) complexes: Theoretical background and its application. Inorg. Chim. Acta 2008, 361, 3432−3445. (69) Mabbs, F. E.; Machin, D. J. Magnetism and Transition Metal Complexes; Chapman and Hall Ltd., 1973. (70) Beghidja, A.; Rabu, P.; Rogez, G.; Welter, R. Synthesis, Structure and Magnetic properties of Chiral and Nonchiral Transition-Metal Malates. Chem. - Eur. J. 2006, 12, 7627−7638. (71) Carlin, R. L. Magnetochemistry; Springer-Verlag: Berlin, 1986; p 328. (72) Rabu, P.; Angelov, S.; Legoll, P.; Belaiche, M.; Drillon, M. Ferromagnetism in Triangular Cobalt(II) Layers: Comparison of Co(OH)2 and Co2(NO3) (OH)3. Inorg. Chem. 1993, 32, 2463−2468. (73) Beghidja, A.; Hallynck, S.; Welter, R.; Rabu, P. Synthesis, Strutures and Magnetic Properties of Layered Metal(II) Mandelates. Eur. J. Inorg. Chem. 2005, 2005, 662−669. (74) Demessence, A.; Rogez, G.; Welter, R.; Rabu, P. Structure and Magnetic Properties of a New Cobalt(II) Thiophenedicarboxylate Coordination Polymer Showing Unprecedented Coordination. Inorg. Chem. 2007, 46, 3423−3425. (75) Farger, P.; Guillot, R.; Leroux, F.; Parizel, N.; Gallart, M.; Gilliot, P.; Rogez, G.; Delahaye, E.; Rabu, P. Imidazolium Dicarboxylate Based Metal−Organic Frameworks Obtained by Solvo-Ionothermal Reaction. Eur. J. Inorg. Chem. 2015, 2015, 5342− 5350. (76) Massard, A.; Braunstein, P.; Danopoulos, A. A.; Choua, S.; Rabu, P. Studies on Three-Coordinate [Co{N(SiMe3)2}2L] Complexes, L = N-Heterocyclic Carbene. Organometallics 2015, 34, 2429−2438.

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Series of Hydrated Heterometallic Uranyl-Cobalt(II) Coordination

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