Uranyl Ion Complexes with Long-Chain Aliphatic α,ω-Dicarboxylates and 3d-Block Metal Counterions

Zwitterionic and Anionic Polycarboxylates as Coligands in Uranyl Ion Complexes, and Their Influence on Periodicity and Topology

The three zwitterionic di- and tricarboxylate ligands 1,1'-[(2,3,5,6-tetramethylbenzene-1,4-diyl)bis(methylene)]bis(pyridin-1-ium-4-carboxylate) (pL1), 1,1'-[(2,3,5,6-tetramethylbenzene-1,4-diyl)bis(methylene)]bis(pyridin-1-ium-3-carboxylate) (mL1), and 1,1',1″-[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(pyridin-1-ium-4-carboxylate) (L2) have been used as ligands to synthesize a series of 15 uranyl ion complexes involving various anionic coligands, in most cases polycarboxylates. [(UO₂)₂(pL1)₂(cbtc)(H₂O)₂]·10H₂O (1, cbtc^4- = cis,trans,cis-1,2,3,4-cyclobutanetetracarboxylate) is a discrete, dinuclear ring-shaped complex with a central cbtc^4- pillar. While [UO₂(pL1)(NO₃)₂] (2), [UO₂(pL1)(OAc)₂] (3), and [UO₂(pL1)(HCOO)₂] (4) are simple chains, [(UO₂)₂(mL1)(1,3-pda)₂] (5, 1,3-pda^2- = 1,3-phenylenediacetate) is a daisy chain and [UO₂(pL1)(pdda)]₃·10H₂O (6, pdda^2- = 1,2-phenylenedioxydiacetate) is a double-stranded, ribbon-like chain. Both [UO₂(pL1)(pht)]·5H₂O (7, pht^2- = phthalate) and [(UO₂)₃(mL1)(pht)₂(OH)₂] (8) crystallize as diperiodic networks with the sql topology, the latter involving hydroxo-bridged trinuclear nodes. [(UO₂)₂(pL1)(c/t-1,3-chdc)₂] (9, c/t-1,3-chdc^2- = cis/trans-1,3-cyclohexanedicarboxylate) and [UO₂(pL1)(t-1,4-chdc)]·1.5H₂O (10, t-1,4-chdc^2- = trans-1,4-cyclohexanedicarboxylate) are also diperiodic, with the V₂O₅ and sql topologies, respectively. Both [(UO₂)₂(mL1)(c/t-1,4-chdc)₂] (11) and [(UO₂)₂(pL1)(1,2-pda)₂] (12, 1,2-pda^2- = 1,2-phenylenediacetate) crystallize as diperiodic networks with hcb topology, and they display threefold parallel interpenetration. [HL2][(UO₂)₃(L2)(adc)₃]Br (13, adc^2- = 1,3-adamantanedicarboxylate) contains a very corrugated hcb network with two different kinds of cells, and the uncoordinated HL2⁺ molecule associates with the coordinated L2 to form a capsule containing the bromide anion. [(UO₂)₂(pL1)(kpim)₂] (14, kpim^2- = 4-ketopimelate) is a three-periodic framework with pL1 molecules pillaring fes diperiodic subunits, whereas [(UO₂)₂(L2)₂(t-1,4-chdc)](NO₃)_1.7Br_0.3·6H₂O (15), the only cationic complex in the series, is a triperiodic framework with dmc topology and t-1,4-chdc^2- anions pillaring fes diperiodic subunits. Solid-state emission spectra and photoluminescence quantum yields are reported for all complexes.

Ni(2,2':6',2″-Terpyridine-4'-carboxylate)2 Zwitterions and Carboxylate Polyanions in Mixed-Ligand Uranyl Ion Complexes with a Wide Range of Topologies

The zwitterionic complex formed by Ni^II and 2,2':6',2″-terpyridine-4'-carboxylate, Ni(tpyc)₂, has been used as a coligand with a diverse group of polycarboxylates in uranyl ion complexes synthesized under solvo-hydrothermal conditions, thus giving a series of 14 mixed ligand, heterometallic compounds. Both [(UO₂)₂(c-1,2-chdc)Ni(tpyc)₂(NO₃)₂]₂·4CH₃CN (1) and [(UO₂)₂(tdc)Ni(tpyc)₂(NO₃)₂]₂ (2), where c-1,2-chdc^2- is cis-1,2-cyclohexanedicarboxylate and tdc^2- is 2,5-thiophenedicarboxylate, display discrete U₄Ni₂ dinickelatetrauranacycles, a motif which is also found as part of a daisychain coordination polymer in [(UO₂)₄(bdc)₃Ni₂(tpyc)₄(NO₃)₂]·2CH₃CN·2H₂O (3), where bdc^2- is 1,4-benzenedicarboxylate. Similar U₄Ni₂ rings associate to form a nanotubular polymer in [(UO₂)₂(tca)Ni(tpyc)₂(NO₃)]·2CH₃CN·2H₂O (4), where tca^3- is tricarballylate. [(UO₂)₂(1,2-pda) (1,2-pdaH)Ni(tpyc)₂(NO₃)]·CH₃CN (5), where 1,2-pda^2- is 1,2-phenylenediacetate, crystallizes as a meander-like chain in which each bent section can be seen as an open, semi-U₄Ni₂ ring. Oxalate (ox^2-) gives [(UO₂)₂(ox)₂Ni(tpyc)₂] (6), a monoperiodic polymer containing smaller U₄Ni rings, while 1,2,3-benzenetricarboxylate (1,2,3-btc^3-) and citrate (citH^3-) give [Ni(tpycH)(H₂O)₃][UO₂(1,2,3-btc)]₂·2H₂O (7) and [UO₂Ni₂(tpyc)₄][UO₂(citH)]₂ (8), two complexes with charge separation, the latter displaying one-periodic + two-periodic semi-interpenetration. [(UO₂)₂(btcH)Ni(tpyc)₂(NO₃)] (9) and [(UO₂)₂(cbtcH)Ni(tpyc)₂(NO₃)] (10), where btc^4- and cbtc^4- are 1,2,3,4-butanetetracarboxylate and cis,trans,cis-1,2,3,4-cyclobutanetetracarboxylate, respectively, are diperiodic networks with hcb topology, and [(UO₂)₂(ndc)Ni(tpyc)₂(OH)(NO₃)] (11), where ndc^2- is 2,6-naphthalenedicarboxylate, is a sql network containing dinuclear nodes and involving 100-membered U₁₀Ni₄ metallacyclic units. U₄Ni₂ rings are found in the diperiodic polymer formed in [(UO₂)₄(t-R-1,2-chdc)₄Ni₂(tpyc)₄] (12), where t-R-1,2-chdc^2- is trans-R,R-1,2-cyclohexanedicarboxylate, the heavily puckered sheets being interlocked. 1,3-Phenylenediacetate (1,3-pda^2-) gives a very thick diperiodic polymer with KIa topology, [(UO₂)₄(1,3-pda)₄Ni₂(tpyc)₄]·CH₃CN·2H₂O (13). A triperiodic framework is formed with nitrilotriacetate (nta^3-) in [(UO₂)₂(nta)₂Ni₂(tpyc)₂] (14), where Ni^II is found in Ni(tpyc)₂ units as well as in Ni(nta)₂^4- moieties which both act as 4-coordinated nodes.

Contrasting Networks and Entanglements in Uranyl Ion Complexes with Adipic and trans,trans-Muconic Acids

Adipic (hexane-1,6-dicarboxylic, adpH₂) and trans,trans-muconic (trans,trans-hexa-2,4-diene-1,6-dicarboxylic, mucH₂) acids have been reacted with uranyl cations under solvo-hydrothermal conditions, yielding nine homo- or heterometallic complexes displaying in their crystal structure the effects of the different flexibility of the ligands. The complexes [PPh₄]₂[(UO₂)₂(adp)₃] (1) and [Ni(bipy)₃][(UO₂)₂(muc)₃]·5H₂O (2), where bipy is 2,2'-bipyridine, crystallize as diperiodic networks with the hcb topology, the layers being strongly puckered or quasiplanar, respectively. Whereas [(UO₂)₂(adp)₃Ni(cyclam)]·2H₂O (3), where cyclam is 1,4,8,11-tetraazacyclotetradecane, crystallizes as a diperiodic network, [(UO₂)₂(muc)₃Ni(cyclam)]·2H₂O (4) is a triperiodic framework in which the Ni^II cations are introduced as pillars within a uranyl-muc^2- framework with the mog topology. [UO₂(adp)(HCOO)₂Cu(R,S-Me₆cyclam)]·2H₂O (5), where R,S-Me₆cyclam is 7(R),14(S)-5,5,7,12,12,14-hexamethylcyclam, is a diperiodic assembly with the sql topology, and it crystallizes together with [H₂NMe₂]₂[(UO₂)₂(adp)₃] (6), a highly corrugated hcb network with a square-wave profile, which displays 3-fold parallel interpenetration. In contrast, [(UO₂)₃(muc)₂(O)₂Cu(R,S-Me₆cyclam)] (7) is a diperiodic assembly containing hexanuclear, μ₃-oxido-bridged secondary building units which are the nodes of a network with the hxl topology. The two related complexes [PPh₃Me]₂[(UO₂)₂(adp)₃]·4H₂O (8) and [PPh₃Me]₂[(UO₂)₂(muc)₃]·H₂O (9) crystallize as hcb networks, but their different shapes, undulated or quasiplanar, respectively, result in different entanglements, 2-fold parallel interpenetration in 8 and 2-fold inclined 2D → 3D polycatenation in 9.

Plumbing the uncertainties of solvothermal synthesis involving uranyl ion carboxylate complexes

Uranyl ion complexes with long-chain, saturated or unsaturated aliphatic dicarboxylate ligands illustrate how solvo-hydrothermal synthetic conditions sometimes result in the formation of species different from those hoped for.

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.

Chiral Discrete and Polymeric Uranyl Ion Complexes with (1 R,3 S)-(+)-Camphorate Ligands: Counterion-Dependent Formation of a Hexanuclear Cage

Reaction of (1 R,3 S)-(+)-camphoric acid (H₂cam) with uranyl ions under solvo-hydrothermal conditions and in the presence of bulky countercations gave five chiral complexes of varying dimensionality. [Cu( R,S-Me₆cyclam)][UO₂(Hcam)₂(HCOO)₂] (1) and [Ni( R,S-Me₆cyclam)][UO₂(cam)(HCOO)₂] (2), in which the formate coligand is formed in situ, involve very similar countercations, but 1 is a discrete, mononuclear complex, whereas 2 crystallizes as a one-dimensional (1D) coordination polymer, and NH-bond donation by the macrocyclic ligand of the countercation complexes is present in both. [Co(en)₃][(UO₂)₄(cam)( R,R-tart)₂(OH)]·3H₂O (3), in which en is ethylenediamine and H₄ R,R-tart is R,R-tartaric acid, contains three enantiomerically pure chiral species, and it displays a two-dimensional (2D) arrangement, with the countercation again involved in NH-bond donation. While [PPh₄][UO₂(cam)(NO₃)] (4) is a 1D polymer, [PPh₃Me]₃[NH₄]₃[(UO₂)₆(cam)₉] (5) is a discrete, homochiral, and homoleptic hexanuclear cage with C₃ point symmetry and a trigonal prismatic arrangement of the uranium atoms. This cage differs from the octanuclear, pseudocubic uranyl camphorate species previously described, thus providing an example of modulation of the cage size through variation of the structure-directing counterions. The cage in 5 is closely associated with three PPh₃Me⁺ cations, two of them outside and with their methyl group directed toward the prism basis center, and one inside the cage cavity. While complex 5 is nonluminescent, complexes 1 and 4 have emission spectra in the solid state typical of equatorially hexacoordinated uranyl complexes. Solid-state photoluminescence quantum yields of 2 and 23% have been measured for complexes 1 and 4, respectively.

Structure-Directing Effects of Counterions in Uranyl Ion Complexes with Long-Chain Aliphatic α,ω-Dicarboxylates: 1D to Polycatenated 3D Species

Nine uranyl ion complexes were synthesized under (solvo-)hydrothermal conditions using α,ω-dicarboxylic acids HOOC-(CH₂) _n-2-COOH (H₂C n, n = 6-9) and diverse counterions. Complexes [PPh₄][UO₂(C6)(NO₃)] (1) and [PPh₄][UO₂(C8)(NO₃)] (2) contain zigzag one-dimensional (1D) chains, with further polymerization being prevented by the terminal nitrate ligands. [PPh₃Me][UO₂(C7)(HC7)] (3) crystallizes as a 1D polymer with a curved section, with hydrogen bonding of the uncomplexed carboxylic groups giving rise to formation of 3-fold interpenetrated two-dimensional (2D) networks. [PPh₄][H₂NMe₂][(UO₂)₂(C7)₃] (4) and [PPh₃Me]₂[(UO₂)₂(C8)₃] (5) contain 1D chains, either ladder-like or containing doubly bridged dimers, while [PPh₃Me]₂[(UO₂)₂(C9)₃]·2H₂O (6) displays interdigitated, strongly corrugated honeycomb 2D nets. Ladder-like 1D polymers in [Cu( R,S-Me₆cyclam)][(UO₂)₂(C7)₂(C₂O₄)]·4H₂O (7) are associated into layers by the hydrogen bonded counterions, whereas the [Ni(cyclam)]²⁺ moieties are part of the 2D polymeric arrangement in [(UO₂)₂(C7)₂(HC7)₂Ni(cyclam)]·2H₂O (8) because of axial coordination of the nickel(II) center, with hydrogen bonding mediated by water molecules generating a three-dimensional (3D) net. [(UO₂)₂K₂(C7)₃(H₂O)]·0.5H₂O (9) contains convoluted uranyl dicarboxylate 2D subunits, which generate a 3D framework through 2D → 3D parallel polycatenation similar to that previously found in [NH₄]₂[(UO₂)₂(C7)₃]·2H₂O; further linking of these subunits is provided by bonding of the potassium cations to carboxylate and uranyl oxido groups. The solid-state emission spectra of complexes 1-6 and 9 display maxima positions typical of hexacoordinated uranyl carboxylate complexes, but uranyl luminescence is quenched in 7. A solid-state photoluminescence quantum yield of 11.5% has been measured for complex 1, while those for compounds 3-6 and 9 are in the range of 2.0-3.5%.

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.

The crystalline α,ω-dicarboxylate metal complex with the longest aliphatic chain to date: uranyl 1,15-pentadecanedioate

A bilayer 2D network is formed in uranyl 1,15-pentadecanedioate, different from the species obtained with related ligands and bulkier counterions.

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.