Effect of heavy-atom (Br) at the phenyl rings of Schiff-base ligands on the NIR luminescence of their bimetallic Zn-Nd complexes

Two heterobimetallic Zn-Nd phenylene-bridged Schiff-base ligands complexes [ZnNdL1(Py)(NO3)(3)] (1) and [(ZnLNd)-Nd-2(Py)(NO3)(3)] center dot MeCN (2) (Py = pyridine, H2L1 = N,N'-bis(3-methoxy-salicylidene)phenylene-1,2-diamine, H2L2 = N,N'-bis-5-bromo-3-methoxy-salicylidene)phenylene-1,2-diamine) were obtained. Both 1 and 2 were structurally characterized by X-ray crystallography, and their near-infrared (NIR) luminescent properties were determined. For the two complexes, the occupation of pyridine at the axial position of 3d Zn2+ ions could effectively prevent luminescent quenching arising from OH-, NH- or CH oscillators of the solvates around the 4f Nd3+ ions, and the heavy-atom (Br) effect of the Schiff-base ligands on their NIR luminescent properties is also discussed.