Synthesis, crystal structure and properties of two terbium complexes with 2,2′-bipyridine

Two new complexes {[Tb(2-IBA)3 · 2,2′-bipy]2 · C2H5OH} (1) and [Tb(2-ClBA)3 · 2,2′-bipy]2 (2) (2-IBA = 2-iodobenzoate; 2-ClBA = 2-chlorobenzoate; 2,2′-bipy = 2,2′-bipyridine) were prepared and their crystal structures determined by X-ray diffraction. Complex 1 is composed of two types of binuclear molecules, [Tb(2-IBA)3 · 2,2′-bipy]2 (a) and [Tb(2-IBA)3 · 2,2′-bipy]2 (b), and an uncoordinated ethanol molecule. In molecule (a), two Tb3+ ions are linked by four 2-IBA groups, all bidentate-bridging. In molecule (b), two Tb3+ ions are held together by four 2-IBA groups in two coordination modes, bidentate-bridging and chelating-bridging. In the two molecules, each Tb3+ ion is further bonded to one chelating 2-IBA group and one chelating 2,2′-bipy molecule, resulting in coordination numbers of eight for (a) and nine for (b). The structural characteristics of 2 are similar to that of molecule (b) in 1. The two complexes, 1 and 2, both emit strong green fluorescence under ultraviolet light with the 5D4 → 7F j (j...