Uranyl ion complexes with 2,2′:6′,2′′-terpyridine-4′-carboxylate. Interpenetration of networks involving “expanded ligands”?

CrystEngComm Pub Date: 2021-09-28 DOI: 10.1039/D1CE01215K

Abstract

2,2′:6′,2′′-Terpyridine-4′-carboxylic acid (tpycH) has been used as a ligand in the synthesis of four uranyl ion complexes under solvo-hydrothermal conditions. The homometallic complex [(UO2)2(tpyc)(HCOO)(OH)2] (1) contains additional hydroxide and formate anions generated in situ and it crystallizes as a monoperiodic coordination polymer in which uranyl cations are bound to both the carboxylate group and the terpyridine N3 site. Addition of PbII gives the heterometallic complex [UO2Pb(tpyc)(HCOO)2(OH)(H2O)2] (2), in which uranyl is bound to the carboxylate group while lead(II) occupies the N3 site, further hydroxide- and formate-bridging resulting in a diperiodic arrangement. Both complexes [UO2Ni(tpyc)2(OH)(H2O)]·NO3·1.5H2O (3) and [(UO2)2Ni2(tpyc)4(O)(H2O)4]·(NO3)2·6H2O (4) contain the neutral, octahedral Ni(tpyc)2 “expanded ligand” unit, the uranyl cations being bound to the divergent carboxylate groups and to bridging hydroxo or oxo groups. Complex 3 crystallizes as a heavily corrugated diperiodic assembly in which hydroxo-bridged dinuclear secondary building units are the nodes of a network of sql topology. Chiral, diperiodic polymers with the same topology but a different shape and which are involved in twofold parallel interpenetration, are formed in 4.

Graphical abstract: Uranyl ion complexes with 2,2′:6′,2′′-terpyridine-4′-carboxylate. Interpenetration of networks involving “expanded ligands”
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