Solvothermal Synthesis, Crystal Structure, and Luminescent Properties of Three Heterometallic Lanthanide‐Transition‐Metal Frameworks Constructed from Three Types of CuBr Motifs

Three three‐dimensional (3D) heterometallic lanthanide‐transition‐metal (hetero‐ Ln ‐TM) compounds with the formula [ Ln 6 (Cu 4 Br 3 )(Cu 2 Br 2 ) 2 (Cu 2 Br)(IN) 20 (H 2 O) 12 ] · 2H 2 O [ Ln = Gd ( 1 ), Ln = Sm ( 2 ), Ln = Eu ( 3 )] based on the linkages of one‐dimensional Ln organic chain and Cu m Br n units were synthesized by mixing Ln 2 O 3 with isonicotinic acid (HIN = pyridine‐4‐carboxylic acid) under hydrothermal condition. During the synthesis, two ligands were used: the isonicotinate (IN – ) stabilizes the cluster and links the one‐dimensional Ln organic chains and Cu m Br n motif, whereas Br – anions play a very important role in the formation of the distinct Cu m Br n units. It is interesting that there are three different Cu‐Br motifs: a closed four‐membered ring [Cu 2 Br 2 ] subunit, a linear [Cu 2 Br] subunit, an S‐sharp [Cu 4 Br 3 ] subunit. Strong fluorescence of compounds 2 and 3 suggests an efficient energy transfer from the ligand to Eu 3+ ions. The luminescent investigation indicates that 2 and 3 are excellent candidates for fluorescent materials.