Heterometallic Uranyl Squarate Compounds with Transition Metal‐Bipyridine Bulky Cations as Structure Directing Components

Abstract

Heterometallic actinide compounds with tailored components functions have attracted much attention, but their controllable synthesis is still challenging. In this work, using bulky transition metal‐bipyridine cations as structure directing components, we have successfully synthesized six novel heterometallic uranyl squarate compounds, 1‐6, with different metal‐bipyridine units. A time‐dependent crystal transformation from 1 with triple interwoven structure to 2 with parallel stacked structure is observed within the observation period of one month and further characterized via single‐crystal X‐ray diffraction (SCXRD) and powder X‐ray diffraction (PXRD). Further evidences from a combination of several techniques including thermal analysis, variable‐temperature PXRD and variable‐temperature SCXRD demonstrate dehydration‐related lattice evolution of 1 on the basis of structural flexibility of 1, which could be the origin of above‐mentioned crystal transformation from 1 to 2. Furthermore, the effect of types of anions (NO3‐, Cl‐, and SO42‐) on structural diversity of 1‐6 is also discussed in detail, where the Cl‐ or NO3‐ ion coordinate to Cu2+ center in isostructural 3 and 4, while SO42‐ bonds to uranyl nodes in isostructural 5 and 6. This work provides a feasible method for the tailored synthesis of multicomponent actinide complexes by the involvement of bulky charge balance components.