Varying Structure‐Directing Anions in Uranyl Ion Complexes with Ni(2,2′ : 6′,2′′‐terpyridine‐4′‐carboxylate)₂

Abstract

2,2′ : 6′,2“‐Terpyridine‐4′‐carboxylic acid (tpycH) reacts with uranyl cations under solvo‐hydrothermal conditions to give [UO2(tpyc)2] ⋅ 2H2O (1), a monoperiodic polymer different from that previously reported. In the additional presence of NiII cations, the Ni(tpyc)2 “expanded ligand” is formed and the structure of its complexes with the uranyl cation depends on the additional anions present. [(UO2)2F4(H2O)2Ni(tpyc)2] ⋅ 2H2O (2) and [UO2(mds)(H2O)Ni(tpyc)2] (3), where mds2− is methanedisulfonate, are monoperiodic polymers in which the fluoride anions are bridging and the mds2− anions chelating. [(UO2)4(NO3)2(H2O)4Ni5(tpyc)10](CF3SO3)4(NO3)2 ⋅ 7H2O (4) crystallizes as a wide and nearly planar monoperiodic ribbon. [(UO2)2(NO3)2(chdc)Ni(tpyc)2] ⋅ chdcH2 ⋅ 2CH3CN (5), where chdc2− is trans‐1,4‐cyclohexanedicarboxylate, is a monoperiodic chain including both bridging Ni(tpyc)2 and chdc2− ligands, the chains being further assembled into layers through hydrogen bonding to bridging chdcH2 molecules. Finally, [UO2Ni2(tpyc)4](I3)2 (6) crystallizes as a diperiodic network with sql topology. These results point to the possibility of modulating the structure of cationic uranyl ion complexes with Ni(tpyc)2 through addition of a wide range of bonding or non‐bonding anions.

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 presence of the two oxalate chelate rings limits further coordination to that of a single donor from Ni(tpyc)2. This bis( 1 O) coordination mode of Ni(tpyc)2 has been frequently observed 32,33 (an analogous behaviour is known for the Ni(cptpy)2 species 34 ) but this is the first occurrence in the present series. The terpy moieties do not interact with one another within the polymer chain but the packing (KPI, Diperiodic coordination polymers.…”

“…, which include cis-1,2-cyclohexanedicarboxylate and 2,5-thiophenedicarboxylate, respectively. In the previously 33 involving trans-1,4-cyclohexanedicarboxylate, the positional isomer of c-1,2-chdc 2found in complex 1, the dicarboxylate and zwitterion units are present in perhaps the simplest form of coordination polymer that might be anticipated in that they act alternately as bridges between uranyl ions in a monoperiodic chain. Chelating nitrate ligands on each U VI centre appear to block dicarboxylate or zwitterion coordination which could produce extension into a second direction.…”

“…This network has the point symbol {4 4 .6 2 } and the common sql topological type, as previously found in the complex [UO2Ni2(tpyc)4](I3)2. 33 Due to the protruding terpyridine moieties, the size of the free space within the rings is however small, at 8  15 Å 2 , the elongated rings being arranged in herringbone fashion. The novelty of complex 8 is that it displays 1D + 2D semi-interpenetration (i.e.…”

“…25,26,31 As a charge-neutral species, any zwitterionic ligand must be accompanied by anions in its crystalline complexes with metal cations, giving rise to the possibility that polymerization due to binding of a multiple carboxylato-zwitterion could be reinforced or usefully modified by binding of a polycarboxylate anion. As part of our continuing exploration of the utility of tpyc  in uranyl ion coordination chemistry, 32,33 this has been found in the monoperiodic mixed ligand complex of uranyl ion formed with Ni(tpyc)2 and trans-1,4-cyclohexane dicarboxylate (t-1,4chdc 2 ), 33 a result complementing the preceding characterization of the uranyl ion complex of Ni(cptpy)2 (cptpy = 4ʹ-(4ʹ-carboxylatophenyl)-2,2ʹ;6ʹ,2-terpyridine) and 4,4ʹ-biphenyl dicarboxylate, 34 where the greater size of both the zwitterion and the dicarboxylate species leads to a diperiodic coordination polymer with hcb topology exhibiting 2D + 2D  3D polycatenation and remarkable catalytic properties. In the present work, we have focussed upon variation of the polycarboxylate accompanying the Ni(tpyc)2 zwitterion in their uranyl ion complexes, and we have isolated a series of 14 mixed-ligand complexes which have been crystallographically characterized.…”

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

“…In exploring the coordination chemistry of the zwitterionic dicarboxylate Ni­(tpyc) 2 (tpyc – = 2,2′;6′,2″-terpyridine-4′-carboxylate) as a reinforcing and modifying bridge within coordination polymers formed by anionic dicarboxylates with uranyl ion, , as an extension of the widespread use of polycarboxylates in uranyl chemistry, − we were drawn to conclude that the zwitterion does provide a versatile coligand and that its functions depend upon both its essentially linear form and the interactions induced by its terpyridine core. This form and these interactions appeared to result in the formation of discrete heterometallacyclic units as well as mono- or diperiodic polymers, many of the latter showing significant solvent-accessible free space and thus the potential for accommodation of reactive guests, but in no case was a fully enclosed cavity identified.…”