Linear bis-Coordinate Silver(I) and Iodine(I) Complexes with R3 R2 R1 N Tertiary Amines

Homoleptic [L-I-L]+ iodine(I) complexes (where L is a R3 R2 R1 N tertiary amine) were synthesized via the [L-Ag-L]+ → [L-I-L]+ cation exchange reaction. In solution, the amines form [R3 R2 R1 N-Ag-NR1 R2 R3 ]+ silver(I) complexes, which crystallize out from solution as the meso-[L-Ag-L]+ complexes, as characterized by X-ray crystallography. The subsequent [L-I-L]+ iodine(I) analogues were extremely reactive and could not be isolated in the solid state. Density functional theory (DFT) calculations were performed to study the Ag+ -N and I+ -N interaction energies in silver(I) and iodine(I) complexes, with the former ranging from -80 to -100 kJ mol-1 and latter from -260 to -279 kJ mol-1 . The X-ray crystal structures revealed Ag+ ⋅⋅⋅Cπ and Ag+ ⋅⋅⋅H-C short contacts between the silver(I) cation and flexible N-alkyl/N-aryl groups, which are the first of their kind in such precursor complexes.

Flexible Aliphatic Diammonioacetates as Zwitterionic Ligands in UO22+ Complexes: Diverse Topologies and Interpenetrated Structures

N,N,N',N'-Tetramethylethane-1,2-diammonioacetate (L1) and N,N,N',N'-tetramethylpropane-1,3-diammonioacetate (L2) are two flexible zwitterionic dicarboxylates which have been used as ligands for the uranyl ion, 12 complexes having been obtained from their coupling to diverse anions, mostly anionic polycarboxylates, or oxo, hydroxo and chlorido donors. The protonated zwitterion is a simple counterion in [H₂L1][UO₂(2,6-pydc)₂] (1), where 2,6-pydc^2- is 2,6-pyridinedicarboxylate, but it is deprotonated and coordinated in all the other complexes. [(UO₂)₂(L2)(2,4-pydcH)₄] (2), where 2,4-pydc^2- is 2,4-pyridinedicarboxylate, is a discrete, binuclear complex due to the terminal nature of the partially deprotonated anionic ligands. [(UO₂)₂(L1)(ipht)₂]·4H₂O (3) and [(UO₂)₂(L1)(pda)₂] (4), where ipht^2- and pda^2- are isophthalate and 1,4-phenylenediacetate, are monoperiodic coordination polymers in which central L1 bridges connect two lateral strands. Oxalate anions (ox^2-) generated in situ give [(UO₂)₂(L1)(ox)₂] (5) a diperiodic network with the hcb topology. [(UO₂)₂(L2)(ipht)₂]·H₂O (6) differs from 3 in being a diperiodic network with the V₂O₅ topological type. [(UO₂)₂(L1)(2,5-pydc)₂]·4H₂O (7), where 2,5-pydc^2- is 2,5-pyridinedicarboxylate, is a hcb network with a square-wave profile, while [(UO₂)₂(L1)(dnhpa)₂] (8), where dnhpa^2- is 3,5-dinitro-2-hydroxyphenoxyacetate, formed in situ from 1,2-phenylenedioxydiacetic acid, has the same topology but a strongly corrugated shape leading to interdigitation of layers. (2R,3R,4S,5S)-Tetrahydrofurantetracarboxylic acid (thftcH₄) is only partially deprotonated in [(UO₂)₃(L1)(thftcH)₂(H₂O)] (9), which crystallizes as a diperiodic polymer with the fes topology. [(UO₂)₂Cl₂(L1)₃][(UO₂Cl₃)₂(L1)] (10) is an ionic compound in which discrete, binuclear anions cross the cells of the cationic hcb network. 2,5-Thiophenediacetate (tdc^2-) is peculiar in promoting self-sorting of the ligands in the ionic complex [(UO₂)₅(L1)₇(tdc)(H₂O)][(UO₂)₂(tdc)₃]₄·CH₃CN·12H₂O (11), which is the first example of heterointerpenetration in uranyl chemistry, involving a triperiodic, cationic framework and diperiodic, anionic hcb networks. Finally, [(UO₂)₇(O)₃(OH)_4.3Cl_2.7(L2)₂]Cl·7H₂O (12) crystallizes as a 2-fold interpenetrated, triperiodic framework in which chlorouranate undulating monoperiodic subunits are bridged by the L2 ligands. Complexes 1, 2, 3, and 7 are emissive with photoluminescence quantum yields in the range of 8-24%, and their solid-state emission spectra show the usual dependence on number and nature of donor atoms.

Luminescent Uranium-Thiophene Dicarboxylate Frameworks Supported by Transition-Metal-Organic Cations: Dimensionality and Luminescence Control in Uranyl Speciation

The study about the resourcfulization of uranium such as the usage as new materials can promote the harmless treatments of nuclear waste. In this work, with the direction of transition-metal...

Varied role of organic carboxylate dizwitterions and anionic donors in mixed-ligand uranyl ion coordination polymers

Two organic dizwitterions were combined with various anionic donors to generate a series of five uranyl ion complexes crystallizing as mono- or diperiodic coordination polymers, with separation into two distinct networks in one case.

1,2,4-Triazolyl-4-acetate: a ditopic ligand combining soft and hard donor sites in homometallic (AgI) and heterometallic (AgI/UVI) coordination polymers

A 1,2,4-triazol-4-yl-acetic acid (trGly-H) was used for the synthesis of AgI and AgI/UVI coordination polymers. The composition space diagram was built for the AgNO3/trGly-H/UO2(NO3)2·6H2O system shows the crystallization fields of two AgI/UVI-compounds were found.

2,5-Thiophenedicarboxylate: An Interpenetration-Inducing Ligand in Uranyl Chemistry

Seven uranyl ion complexes have been crystallized under solvo-hydrothermal conditions from 2,5-thiophenedicarboxylic acid (tdcH₂) and diverse additional, structure-directing species. [UO₂(tdc)(DMF)] (1) is a two-stranded monoperiodic coordination polymer, while [PPh₃Me][UO₂(tdc)(HCOO)] (2) is a simple chain with terminal formate coligands. Although it is also monoperiodic, [C(NH₂)₃][H₂NMe₂]₂[(UO₂)₃(tdc)₄(HCOO)] (3) displays an alternation of tetra- and hexanuclear rings. Two-stranded subunits are bridged by oxo-coordinated Ni^II cations to form a diperiodic network in [UO₂(tdc)₂Ni(cyclam)] (4), but a homometallic sql diperiodic assembly is built in [Cu(R,S-Me₆cyclam)(H₂O)][UO₂(tdc)₂]·H₂O (5), to which the counterion is hydrogen bonded only. Diperiodic networks with the hcb topology are formed in both [Zn(phen)₃][(UO₂)₂(tdc)₃]·2H₂O·3CH₃CN (6) and [PPh₄]₂[(UO₂)₂(tdc)₃]·2H₂O (7). The slightly undulating layers in 6 are crossed by oblique columns of weakly interacting counterions in polythreading-like fashion. In contrast, the larger curvature in 7 allows for three-fold, parallel 2D interpenetration to occur. These results are compared with previously reported cases of interpenetration and polycatenation in the uranyl-tdc^2- system.

Variability of structural motifs in the crystal structure of U(vi) complexes with p-methoxybenzoic acid

An unexpected crystal structure based on the simultaneous presence of 0D and 1D uranyl-containing building units was obtained.

Tubelike Uranyl-Phenylenediacetate Assemblies from Screening of Ligand Isomers and Structure-Directing Counterions

Reaction of 1,2-, 1,3-, or 1,4-phenylenediacetic acids (1,2-, 1,3-, or 1,4-H₂PDA) with uranyl ions under solvo-hydrothermal conditions and in the presence of [M(L) _n] ^q+ cations, in which M = transition metal cation, L = 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen), n = 2 or 3, and q = 1 or 2, gave 10 complexes which have been crystallographically characterized. The diacetate ligands are bis-chelating and the uranyl cations are tris-chelated in all cases. [UO₂(1,2-PDA)₂Zn(phen)₂]·2H₂O (1) and [UO₂(1,4-PDA)₂Mn(bipy)₂]·H₂O (2) are heterometallic, neutral one-dimensional (1D) coordination polymers in which the carboxylate-coordinated 3d block metal cation is either decorating only (1) or participates in polymer building (2). [Zn(phen)₃][(UO₂)₂(1,3-PDA)₃] (3) and [Ni(phen)₃][(UO₂)₂(1,4-PDA)₃]·H₂O (4), with separate counterions, crystallize as anionic two-dimensional (2D) networks, as does [Cu(bipy)₂][H₂NMe₂][(UO₂)₂(1,4-PDA)₃] (5), which displays parallel 2D interpenetration. The complex [Zn(phen)₃][(UO₂)₂(1,2-PDA)₃]·7H₂O (6) crystallizes as a ladderlike, slightly inflated ribbon. The same topology is found in [Zn(bipy)₃][(UO₂)₂(1,3-PDA)₃] (7), but the larger separation between coordination sites and the coexistence of curved and divergent ligand conformations produce a tubelike assembly. An analogous but more regular and spacious tubular geometry is found in [M(bipy)₃][(UO₂)₂(1,4-PDA)₃], with M = Co (8) or Ni (9), and {Λ-[Ru(bipy)₃]}[(UO₂)₂(1,4-PDA)₃] (10). The disordered counterions in 8 and 9 are replaced by well-ordered, enantiomerically pure chiral counterions in 10. The tubular assemblies formed in 7-10 are characterized by an oblong section and the presence of gaps in the walls, which enable the inclusion of two rows of counterions in the cavity.

Structural Tuning and Sensitization of Uranyl Phosphonates by Incorporation of Countercations into the Framework

By the introduction of terephthalic acid, tetramethylammonium chloride, and Zn²⁺ ions, three new uranyl triphosphonates with varying crystal structures, namely, [H₃O][(UO₂)₂(HL)]·H₂O (1), [NMe₄][(UO₂)₂(HL)(H₂O)]·H₂O (2), and [(UO₂)₃Zn(H₂L)₂(H₂O)₂]·3H₂O (3), where H₆L = benzene-1,3,5-triyltris(methylene) triphosphonic acid, have been successfully synthesized and characterized by means of powder and single crystal XRD, IR, EA, TGA, UV-vis, and luminescence. These three compounds all possess three-dimensional framework structures with hydrium, tetramethylammonium, and Zn²⁺ as the respective countercations. The uranium(VI) center luminescence of compounds 1 and 2 is completely quenched. However, the incorporation of Zn²⁺ into the matrix of uranyl phosphonate in the case of compound 3 results in the emerging of the typical intense vibronic emissions of U(VI), demonstrating that zinc phosphonate can behave as sensitizer of uranyl phosphonates. The quenching and sensitization mechanism were also discussed.

Structural Consequences of 1,4-Cyclohexanedicarboxylate Cis/Trans Isomerism in Uranyl Ion Complexes: From Molecular Species to 2D and 3D Entangled Nets

trans-1,4-Cyclohexanedicarboxylic acid (t-1,4-chdcH₂) or the commercially available mixture of the cis and trans isomers (c,t-1,4-chdcH₂) has been used in the synthesis of a series of 14 uranyl ion complexes, all obtained under solvohydrothermal conditions, some in the presence of additional metal cations and/or 2,2'-bipyridine (bipy). With its two isomeric forms having very different shapes and its great sensitivity to the experimental conditions, 1,4-chdc^2- appears to be suitable for the synthesis of uranyl ion complexes displaying a wide range of architectures. Under the conditions used, the pure trans isomer gives only the complexes [UO₂(t-1,4-chdc)(H₂O)₂] (1) and [UO₂(t-1,4-chdc)] (2), which crystallize as one- and two-dimensional (1D and 2D) species, respectively. Complexes containing either the cis isomer alone or mixtures of the two isomers in varying proportion were obtained from the isomer mixture. The neutral complexes [UO₂(c-1,4-chdc)(DMF)] (3) and [UO₂(c-1,4-chdc)(bipy)] (4) are 2D and 1D assemblies, respectively, while all the other complexes are anionic and include various counterions. [C(NH₂)₃]₃[H₂NMe₂][(UO₂)₄(c-1,4-chdc)₆]·H₂O (5) crystallizes as a three-dimensional (3D) framework with {10³} topology. While [H₂NMe₂]₂[(UO₂)₂(c-1,4-chdc)₂(t-1,4-chdc)]·DMF·2H₂O (6) is a 1D ladderlike polymer, [H₂NMe₂]₂[(UO₂)₂(c-1,4-chdc)(t-1,4-chdc)₂]·2H₂O (7), which differs in the cis/trans ratio, is a 3-fold 2D interpenetrated network with {6³} honeycomb topology. The related [H₂NMe₂]₂[(UO₂)₂(c,t-1,4-chdc)₃]·2.5H₂O (8), with one disordered ligand of uncertain geometry, is a 3-fold 3D interpenetrated system. The two isomorphous complexes [Co(bipy)₃][(UO₂)₂(c-1,4-chdc)₃]·1.5H₂O (9) and [Cd(bipy)₃][(UO₂)₂(c-1,4-chdc)₃]·1.5H₂O (10) form 3D frameworks with the {10³} srs topological type. In contrast, [Ni(bipy)₃]₂[(UO₂)₄(c-1,4-chdc)₂(t-1,4-chdc)(NO₃)₆]·2H₂O (11) is a molecular, tetranuclear complex due to the presence of terminal nitrate ligands. A 2-fold 3D interpenetration of frameworks with {10³} ths topology is observed in [Cu(bipy)₂]₂[(UO₂)₂(c-1,4-chdc)₂(t-1,4-chdc)]·2H₂O (12), while [Zn(bipy)₃][(UO₂)₂(c-1,4-chdc)₃]·4H₂O (13) crystallizes as a 2D net with the common {4.8²} fes topological type. The additional Pb^II cation is an essential part of the 3D framework formed in [UO₂Pb₂(c-1,4-chdc)(t-1,4-chdc)₂(bipy)₂] (14), in which uranyl and its ligands alone form 1D subunits. Together with previous results, the solid-state uranyl emission properties of seven of the present complexes evidence a general trend, with the maxima for the complexes with O₆ equatorial environments being blue-shifted with respect to those for complexes with O₅ environments.

Coordination Polymers and Cage-Containing Frameworks in Uranyl Ion Complexes with rac- and (1R,2R)-trans-1,2-Cyclohexanedicarboxylates: Consequences of Chirality

Racemic and enantiopure (1R,2R) forms of trans-1,2-cyclohexanedicarboxylic acid (H₂chdc and R-H₂chdc, respectively) have been used in the synthesis of a series of 13 uranyl ion complexes, all obtained under solvo-hydrothermal conditions and in the presence of additional metal cations and/or N-donor ligands. While the homometallic complex [UO₂(R-chdc)] (1) was only obtained with the enantiopure ligand, complexes [UO₂(chdc)(THF)] (2), [UO₂(chdc)(DMF)] (3), and [UO₂(chdc)(NMP)] (4), with a coordinated solvent molecule, were obtained from the racemic form only; all crystallize as two-dimensional (2D) assemblies. The two complexes [UO₂(chdc)(bipy)](5) and [UO₂(R-chdc)(bipy)] (6), where bipy is 2,2'-bipyridine, are isomorphous since 5 crystallizes as a racemic conglomerate; they are both one-dimensional (1D) homochiral, helical polymers. The heterometallic complexes [UO₂Cu(chdc)₂(bipy)(H₂O)]·H₂O (7) and [UO₂Cu(R-chdc)₂(bipy)]·3H₂O (8) crystallize as a 1D or a 2D species, respectively, while [UO₂Cd(R-chdc)₂(H₂O)₂]·H₂O (9) displays a 2D arrangement with the unusual Cairo pentagonal tiling topology. The four complexes [(UO₂)₂Na₂(chdc)₃(H₂O)₂] (10), [(UO₂)₂Ag₂(chdc)₃(H₂O)₂] (11), [(UO₂)₂Na₂(R-chdc)₃(H₂O)₂] (12), and [(UO₂)₂Pb(R-chdc)₃(H₂O)₄] (13) are closely related, all of them containing tetranuclear, pseudotetrahedral [(UO₂)₄(chdc/R-chdc)₆]^4- cage motifs, that are assembled into a three-dimensional (3D) framework by bridging counterions (Na⁺, Ag⁺, or Pb²⁺). These cages define a new pathway to assembly of such species based on the unique coordination geometry of uranyl ion, differing from the widely exploited use of octahedral metal ions.

Recent advances in structural studies of heterometallic uranyl-containing coordination polymers and polynuclear closed species

A survey is given of recent original structural results on heterometallic species incorporating uranyl ions, particularly with carboxylate ligands.

Modulation of the Structure and Properties of Uranyl Ion Coordination Polymers Derived from 1,3,5-Benzenetriacetate by Incorporation of Ag(I) or Pb(II)

Reaction of uranyl nitrate with 1,3,5-benzenetriacetic acid (H3BTA) in the presence of additional species, either organic bases or their conjugate acids or metal cations, has provided 12 new crystalline complexes, all but one obtained under solvo-hydrothermal conditions. The complexes [C(NH2)3][UO2(BTA)]·H2O (1) and [H2NMe2][UO2(BTA)] (2) crystallize as one- or two-dimensional (1D or 2D) assemblies, respectively, both with uranyl tris-chelation by carboxylate groups and hydrogen-bonded counterions but different ligand conformations. One of the bound carboxylate units is replaced by chelating 1,10-phenanthroline (phen) or 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4phen) in the complexes [(UO2)3(BTA)2(phen)3]·4H2O (3) and [(UO2)3(BTA)2(Me4phen)3]·NMP·3H2O (4) (NMP = N-methyl-2-pyrrolidone), which are a 2D network with honeycomb topology and a 1D polymer, respectively. With silver(I) cations, [UO2Ag(BTA)] (5), a three-dimensional (3D) framework in which the ligand assumes various chelating/bridging coordination modes, and the aromatic ring is involved in Ag(I) bonding, is obtained. A series of seven heterometallic complexes results when lead(II) cations and N-chelating molecules are both present. The complexes [UO2Pb(BTA)(NO3)(bipy)] (6) and [UO2Pb2(BTA)2(bipy)2]·3H2O (7), where bipy is 2,2'-bipyridine, crystallize from the one solution, as 1D and 2D assemblies, respectively. The two 1D coordination polymers [UO2Pb(BTA)(HCOO)(phen)] (8 and 9), again obtained from the one synthesis, provide an example of coordination isomerism, with the formate anion bound either to lead(II) or to uranyl cations. Another 2D architecture is found in [(UO2)2Pb2(BTA)2(HBTA)(H2O)2(phen)2]·2H2O (10), which provides a possible example of a Pb-oxo(uranyl) "cation-cation" interaction. While [UO2Pb(BTA)(HCOO)0.5(NO3)0.5(Me2phen)] (11), where Me2phen is 5,6-dimethyl-1,10-phenanthroline, is a 1D assembly close to those in 6 and 8, [UO2Pb2(BTA)2(Me4phen)2] (12), obtained together with complex 4, crystallizes as a 2D network as a result of the high degree of connectivity provided by the chelating/bridging tricarboxylate ligand. Emission spectra measured in the solid state display vibronic fine structure attributable to uranyl luminescence (except for complex 5, in which emission is quenched), with variations in maxima positions associated with modifications of the uranyl ion environment.