Effects of substituent groups on the crystal structures and luminescence properties of zero-/two-dimensional Zn(II) complexes

The 3-position substituted imidazo[1,2-a]pyridine ligands L1 and HL2 were facilely synthesized, and used for construction of two novel luminescent Zn(II) complexes, namely [ZnCl2(L1)2] (1) and [Zn(L2)2]n (2). Single-crystal X-ray diffraction analysis shows that 1 is zero-dimensional structure, whereas, 2 possesses two-dimensional polymeric network with rhombic grid motifs. The structural differences between 1 and 2 should be determined by the different substituent groups adjacent to carbonyl groups of the 3-position substituted imidazo[1,2-a]pyridine ligands. Complex 1 reveals the red-shifted emission band, compared to free L1 ligand, whereas, 2 displays similar emission spectrum to free HL2 ligand. Such results are also ascribed to substituent group effects and corresponding structural differences.