Uranyl Ion Complexes with 1,1′-Biphenyl-2,2′,6,6′-tetracarboxylic Acid: Structural and Spectroscopic Studies of One- to Three-Dimensional Assemblies

Abstract

1,1'-Biphenyl-2,2',6,6'-tetracarboxylic acid (H4L) was reacted with uranyl nitrate, either alone or in the presence of additional metal cations (Ni(2+), Cu(2+), Dy(3+)) under (solvo)-hydrothermal conditions, giving six complexes which were characterized by their crystal structure and, in all but one case, their emission spectrum in the solid state. [Ni(bipy)3][UO2(H2L)(H2O)]2(NO3)2·3H2O (1) crystallizes as a one-dimensional (1D), ribbon-like coordination polymer, while the homometallic complex [(UO2)2(L)(H2O)3]·H2O·CH3CN (2) and the heterometallic complexes [UO2Cu(L)(H2O)2]·H2O (3), [UO2Cu(L)(H2O)]·H2O (4), and [(UO2)5Cu4(HL)6(bipy)4]·2H2O (5) display two-dimensional (2D) arrangements. Lastly, the uranyl-lanthanide heterometallic complex [(UO2)8Dy(HL)6(H2O)8](I)·8H2O (6) crystallizes as a three-dimensional (3D) framework. Although these assemblies adopt different topologies, the {4(2).6} linear motif found in 1 is discernible in the structures of 2, 5, and 6, in which the higher dimensionality arises from further bridging of these subunits by uranyl (2), copper (5), or both uranyl and dysprosium (6) cations. The tetracarboxylic/ate ligands have their two aromatic rings nearly perpendicular to one another. No two of them adopt the same coordination mode in this series (except in the similar complexes 3 and 4), but chelation involving one carboxylate group from each ring is nearly ubiquitous, and the ensuing position of the cation favors the formation of planar architectures. The emission spectra of complexes 2-5 measured in the solid state show the usual uranyl vibronic fine structure, although with significant differences in the emission intensity, while complete quenching of the luminescence is observed in 1.

Structure-Directing Effects of Coordinating Solvents, Ammonium and Phosphonium Counterions in Uranyl Ion Complexes with 1,2-, 1,3-, and 1,4-Phenylenediacetates

“…As previously noted, 10 of 1,2-pda 2the smallest chelate ring that could be formed if both carboxylates were to bind to one metal ion would be 9-membered, a situation which is unknown in uranyl carboxylate systems except for conformationally restricted ligands, 31 (6). It is notable that the majority of diperiodic arrangements have been found within this group of neutral complexes, with only one example in an anionic complex involving the guanidinium counterion (12).…”

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

“…4,5,12,35,37,73,81,82 So as to get a visual representation of the dependence of the peaks positions upon the geometry of the uranyl equatorial environment, the positions of the four main peaks [S10 → S0ν (ν = 0-3)] have been plotted in Figure 16 for a series of 46 complexes involving various polycarboxylate ligands (including also the present results). 4,5,12,32,35,37,49,51,64,67,72,[77][78][79][80][83][84][85] All these complexes are from our own work, so that all measures have been performed using the same apparatus and in exactly the same conditions, and only well resolved spectra of complexes having only one kind of equatorial environment have been considered; the precision of the measurements can be estimated at ±2 nm. The complexes are separated into four groups according to the number and nature of equatorial donors, O6, O4N2, O5 or O4, and the complexes are sorted within each group in the order of red-shift of the lowest wavelength emission peak, so that shifts in the positions of the three other peaks between different complexes reveal slight variations of the splitting energy.…”

Zero-, mono- and diperiodic uranyl ion complexes with the diphenate dianion: influences of transition metal ion coordination and differential UVI chelation

“…40,44 Aromatic groups protrude on the two sides of the layers in larger ligand denticity and more divergent nature result in overall higher periodicity, with diperiodic networks being dominant and one instance of a triperiodic framework. 13 In the present dicarboxylate complexes and whatever the coordination mode, limitation of the connectivity to one side of the ligand limits the periodicity of the assemblies formed.…”

“…Since these two chelation modes will be frequently found in this series of complexes, they will be denoted as modes 1 and 2 respectively, in keeping with former use. 13 The carboxylate oxygen atom not involved in formation of either of these chelate units forms a bridge to another uranium centre, the 3), and the dip 2ligands are now apparently unable to form 9-membered (mode 2) chelate rings.…”

“…12 These particular ligands generally retain a quasi-planar geometry of the diphenyl moiety, but this is no longer true when the carboxylate substituents are located closer to one another, as in 1,1ʹ-diphenyl-2,2ʹ,6,6ʹ-tetracarboxylate, in which steric crowding results in quasi-perpendicular positioning of the two aromatic rings expected to favour triperiodic arrays, and which has actually been shown to form mono-, di-, and triperiodic uranyl complexes. 13 Although 2,2ʹbipyridine-3,3ʹ-dicarboxylate and 1,1ʹ-diphenyl-6,6ʹ-dinitro-2,2ʹ-dicarboxylate, both with tilted aromatic rings, have also been used in this context, [14][15][16] no uranyl ion complex has yet been reported with the simpler ligand resulting from deprotonation of diphenic acid (1,1ʹ-diphenyl-2,2ʹ-dicarboxylic acid, H2dip). In order to expose the possible coordination modes of this ligand toward the uranyl ion and thus its potential for the creation of new coordination arrays, we have synthesized nine homo-or heterometallic complexes under solvo-hydrothermal conditions in the presence of various cosolvents, coligands and additional cations/counterions.…”