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 NiII 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-chdc2- is cis-1,2-cyclohexanedicarboxylate and tdc2- 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 bdc2- 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 tca3- is tricarballylate. [(UO2)2(1,2-pda) (1,2-pdaH)Ni(tpyc)2(NO3)]·CH3CN (5), where 1,2-pda2- 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 (ox2-) gives [(UO2)2(ox)2Ni(tpyc)2] (6), a monoperiodic polymer containing smaller U4Ni rings, while 1,2,3-benzenetricarboxylate (1,2,3-btc3-) and citrate (citH3-) 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 btc4- and cbtc4- 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 ndc2- 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-chdc2- is trans-R,R-1,2-cyclohexanedicarboxylate, the heavily puckered sheets being interlocked. 1,3-Phenylenediacetate (1,3-pda2-) 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 (nta3-) in [(UO2)2(nta)2Ni2(tpyc)2] (14), where NiII is found in Ni(tpyc)2 units as well as in Ni(nta)24- moieties which both act as 4-coordinated nodes.