Hydrothermal syntheses and characterization of a series of mixed-ligand luminescent CdII frameworks with novel 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate ligand and benzenedicarboxylate isomers

Under similar hydrothermal synthetic conditions using a novel flexible ligand 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetonitrile (PPAN), benzenedicarboxylate isomers (H2pa = phthalate, H2ip = isophthalate, and H2tp = terephthalate) and Cadmium(II) acetate, three novel mixed-ligand Cd(II) coordination polymers {[Cd2(PPAA)2(μ-pa)(H2O)]·2H2O}n (1), {[Cd4(PPAA)4 (μ4-ip)2]·2H2O}n (2) and {[Cd2(PPAA)2(μ-tp)]·2H2O}n (3) (PPAA− = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate) have been isolated, in 1–3 PPAN, and are also hydrolyzed into a novel PPAA− ligand. Complex 1 is a 1D coordination polymer in which the tetra-nuclear [Cd4(PPAA)4]4 + structural units are extended by tri-dentate μ-pa2 − ligands. Complex 2 contains binuclear [Cd2(PPAA)2]4 + structural units, which are extended by four tetra-dentate μ4-ip2 − ligands to link eight neighboring binuclear [Cd2(PPAA)2]4 + units ultimately forming a 2D layered framework, while complex 3 contains 1D double chain containing [Cd(PPAA)]n cation structural units, which are further extended by tetradentate μ-tp2 − ligands to form a new 2D layered framework. All the complexes have been investigated by elemental analysis, FT-IR, thermal analysis and fluorescence characterization. The flexible coordination modes of PPAA− are also briefly analyzed. The flexible coordination modes of PPAA− and benzenedicarboxylate isomers also reveal great potential in the construction of these novel mixed-ligand luminescent frameworks with diverse structural motifs and unique functional properties.