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

Abstract

trans-1,4-Cyclohexanedicarboxylic acid (t-1,4-chdcH) or the commercially available mixture of the cis and trans isomers (c,t-1,4-chdcH) 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 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 [UO(t-1,4-chdc)(HO)] (1) and [UO(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 [UO(c-1,4-chdc)(DMF)] (3) and [UO(c-1,4-chdc)(bipy)] (4) are 2D and 1D assemblies, respectively, while all the other complexes are anionic and include various counterions. [C(NH)][HNMe][(UO)(c-1,4-chdc)]·HO (5) crystallizes as a three-dimensional (3D) framework with {10} topology. While [HNMe][(UO)(c-1,4-chdc)(t-1,4-chdc)]·DMF·2HO (6) is a 1D ladderlike polymer, [HNMe][(UO)(c-1,4-chdc)(t-1,4-chdc)]·2HO (7), which differs in the cis/trans ratio, is a 3-fold 2D interpenetrated network with {6} honeycomb topology. The related [HNMe][(UO)(c,t-1,4-chdc)]·2.5HO (8), with one disordered ligand of uncertain geometry, is a 3-fold 3D interpenetrated system. The two isomorphous complexes [Co(bipy)][(UO)(c-1,4-chdc)]·1.5HO (9) and [Cd(bipy)][(UO)(c-1,4-chdc)]·1.5HO (10) form 3D frameworks with the {10} srs topological type. In contrast, [Ni(bipy)][(UO)(c-1,4-chdc)(t-1,4-chdc)(NO)]·2HO (11) is a molecular, tetranuclear complex due to the presence of terminal nitrate ligands. A 2-fold 3D interpenetration of frameworks with {10} ths topology is observed in [Cu(bipy)][(UO)(c-1,4-chdc)(t-1,4-chdc)]·2HO (12), while [Zn(bipy)][(UO)(c-1,4-chdc)]·4HO (13) crystallizes as a 2D net with the common {4.8} fes topological type. The additional Pb cation is an essential part of the 3D framework formed in [UOPb(c-1,4-chdc)(t-1,4-chdc)(bipy)] (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 O equatorial environments being blue-shifted with respect to those for complexes with O environments.

Crown Ethers and Their Alkali Metal Ion Complexes as Assembler Groups in Uranyl–Organic Coordination Polymers with cis-1,3-, cis-1,2-, and trans-1,2-Cyclohexanedicarboxylates

“…23,24,34 Another example is provided in the frequently observed presence of oxalate anion in complexes isolated from media where this anion was not initially present, 35 although here speculation as to its origin has encompassed a variety of pathways, full elucidation having only been performed in some specific cases. 36,37 In all six uranyl complexes reported here, obtained from media incorporating crown ethers, oxalate is found as a coligand, although not initially present.…”

“…In contrast, the spectra of 3 and 4, with the three main signals at 495/501, 517/523 and 541/548 nm, respectively, are typical of complexes with five equatorial carboxylate donors. 24 It is notable that the bands in the spectrum of 4 display clear evidence of additional shoulders, which may be unsurprising considering the number of inequivalent uranyl ions in this structure, but this is not observed in the other spectra.…”

“…The spectrum of 2 is particularly intense and well resolved, and the four main bands [S10 → S0ν (ν = 0-3)], at 480, 500, donors. 24 The bands in the much less intense spectrum of 1 are at the same positions, which is less surprising since two of the three independent uranyl ions in it have six equatorial donors. Although weak, the spectrum of 5 is very close to that of 2, being red-shifted by 2 nm only.…”

Three Different Modes of Association between Metal Cations in Heterometallic Uranyl–CoIII and Uranyl–MnII Species

“…We have recently been interested in the use of the bulky spherical cations [M(L) 3 ] 2+ , in which M is a 3d-block metal cation and L is either 2,2′-bipyridine or 1,10-phenanthroline, as structure-inducing species, and this has enabled isolation of several uranyl carboxylate compounds with original geometry, such as triple-stranded helicates [4] and entangled networks, [5] as well as three-dimensional (3D) frameworks. [6] Our work has been based on the use of solvothermal synthesis to obtain crystalline materials suitable for X-ray diffraction studies. While this is a procedure which has been used by many groups with great success, the lack of de-the third example only of a hydroxo-bridged heterometallic uranyl complex, and the first to involve Co III .…”

“…While this is a procedure which has been used by many groups with great success, the lack of de-the third example only of a hydroxo-bridged heterometallic uranyl complex, and the first to involve Co III . The complex [(UO 2 ) 6 Mn(O) 4 (OH) 6 (H 2 O) 4 ]·5H 2 O (3), synthesized in the absence of any added ligand, crystallizes as a three-dimensional framework in which anionic uranyl oxyhydroxide layers with the α-U 3 O 8 -type polyhedral arrangement are connected to one another by Mn(H 2 O) 4 2+ cations axially bound to two uranyl oxo atoms. These very simple systems thus display a large range of possible intermetallic associations, that involving bis-oxo-bonding to uranyl enabling formation of a framework through pillaring of sheets.…”