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)center dot 4CH(3)CN (1) and [(UO2)(2)(tdc)Ni(tpyc)(2)(NO3)(2)](2) (2), where c-1,2-chdc2- 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)(3)Ni-2(tpyc)(4)(NO3)(2)]center dot 2CH(3)CN center dot 2H(2)O (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)]center dot 2CH(3)CN center dot 2H(2)O (4), where tca(3-) is tricarballylate. [(UO2)(2)(1,2-pda) (1,2-pdaH)Ni(tpyc)(2)(NO3)]center dot 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)(2)Ni(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 center dot 2H(2)O (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)(4)Ni-2(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)(4)Ni-2(tpyc)(4)]center dot CH3CN center dot 2H(2)O (13). A triperiodic framework is formed with nitrilotriacetate (nta3-) in [(UO2)(2)(nta)(2)Ni-2(tpyc)(2)] (14), where NiII is found in Ni(tpyc)(2) units as well as in Ni(nta)(2)(4-) moieties which both act as 4-coordinated nodes.

Automated summary

In this study, a zwitterionic complex Ni(tpyc)(2) was used as a coligand with polycarboxylates to synthesize 14 mixed ligand, heterometallic compounds. These compounds exhibit various dinickelatetrauranacycles, coordination polymers, and nanotubular polymers.