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Abstract
Three coordination architectures, {[Ag4(pbmb)4·(BF4)4](CH3OH)2·H2O}n (1), {[Cd2(pbmb)4](ClO4)4·(CH3OH)5}n (2), and [Cd4(pbmb)4·I8(CH3OH)2]n (3) (pbmb = 1-((2-(pyridin-2-yl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole), are built up from Ag(I)/Cd(II) salts and a flexible pyridyl-benzimidazole-based organic spacer. Single-crystal analysis shows that 1 and 2 have 1-D chains, while 3 displays a tetranuclear structure. All complexes exhibit different coordination geometries and properties, which can be attributed to the difference between the metal centers or anions. In the case of 1 in particular, the Ag⋯Ag interactions play a crucial role in the formation of a supramolecular architecture. The binuclear-based complex consists of a pair of Ag⋯Ag contacts (ca. 2.953 Å), and it exhibits intense triplet emission with large Stokes shift and high thermal stability. Compared to pbmb, 2 has excellent high-energy fluorescence properties, while 1 and 3 exhibit mainly low-energy emission. Therefore, it can be concluded that the heavy atom effect has a causative influence in enhancing the triplet state radiative rate, resulting in large Stokes’ shift of the complex.
