Zinc Complexes with Mixed Ligands and the Effect on Excitation and Emission Spectra by Changing the Binding Sites

Abstract Fluorescence properties of mixed‐ligand zinc(II) complexes may be affected by the interactions between different ligands, resulting in more complex fluorescence behavior due to the discrepancy between energy levels. In this paper, three zinc(II) complexes: {[Zn 2 (L 1 ) 2 (CO 3 )](H 2 O)} n ( 1 ), [Zn(L 2 )(H 2 O) 3 ] n ( 2 ), and [Zn 8 (L 1 ) 8 (L 2 ) 4 (H 2 O) 4 ] n ( 3 ) were obtained by using 3‐amino‐1,2,4‐triazole (HL 1 ) and 5‐hydroxyisophthalic acid (H 2 L 2 ) as organic linkers. X‐ray single crystal diffraction shows that 1 can be described as the dinuclear zinc SBUs bridged through L 1 − and CO 3 2− to form a 2‐D structure. Complex 2 features the L 2 2− linkers connecting mononuclear Zn(II) in μ 2 ‐η 1 :η 1 fashion to generate an 1‐D structure, and the adjacent chains were packed through hydrogen bonds to assemble a 2‐D structure. However, 3 is characterized the eight‐core zinc units concatenated by L 1 − and L 2 2− to acquire a 3‐D structure. An obvious red‐shift of 73 nm, and 76 nm emerges in solid‐state fluorescence emission spectrum of 3 compared with HL 1 and H 2 L 2 , which is also stronger than that of 1 and 2 . Such phenomenon is mainly caused by the richer binding sites with Zn(II) in 3 deriving from mixed ligands, which is not only conducive to increase the stability of the complex but also to reduce the possibility of nonradiative transitions.