Construction of Hybrid Bimetallic Uranyl Compounds Based on a Preassembled Terpyridine Metalloligand

Six hybrid uranyl–transition metal compounds [UO 2 Ni(cptpy) 2 (HCOO) 2 (DMF)(H 2 O)] ( 1 ), [UO 2 Ni(cptpy) 2 (BTPA) 2 ] ( 2 ), [UO 2 Fe(cptpy) 2 (HCOO) 2 (DMF)(H 2 O)] ( 3 ), [UO 2 Fe(cptpy) 2 (BTPA) 2 ] ( 4 ), [UO 2 Co(cptpy) 2 (HCOO) 2 (DMF)(H 2 O)] ( 5 ), and [UO 2 Co(cptpy) 2 (BTPA) 2 ] ( 6 ), based on bifunctional ligand 4′‐(4‐carboxyphenyl)‐2,2′:6′,2′′‐terpyridine (Hcptpy) are reported (H 2 BTPA = 4,4′‐biphenyldicarboxylic acid). Single‐crystal XRD revealed that all six compounds feature similar metalloligands, which consist of two cptpy − anions and one transition metal cation. The metalloligand M(cptpy) 2 can be considered to be an extended linear dicarboxylic ligand with length of 22.12 Å. Compounds  1 , 3 , and 5 are isomers, and all of them feature 1D chain structures. The adjacent 1D chains are connected together by hydrogen bonds and π–π interactions to form a 3D porous structure, which is filled with solvent molecules and can be exchanged with I 2 . Compounds  2 , 4 , and 6 are also isomers, and all of them feature 2D honeycomb (6,3) networks with hexagonal units of dimensions 41.91×26.89 Å, which are the largest among uranyl compounds with honeycomb networks. The large aperture allows two sets of equivalent networks to be entangled together to result in a 2D+2D→3D polycatenated framework. Remarkably, these uranyl compounds exhibit high catalytic activity for cycloaddition of carbon dioxide. Moreover, the geometric and electronic structures of compounds  1 and 2 are systematically discussed on the basis of DFT calculations.