Construction of Isomorphous Coordination Polymers with 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate Ligand: Structures, Fluorescent Temperature Sensing, and Magnetic Properties

In this work, four isomorphous two-dimensional (2D) complexes, [M(PPA)(HCOO)]n (M=Zn (1), Co (2), Ni (3) and Cd (4)) have been synthesized under solvothermal conditions by mixed 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate (PPA) with transition metal ion (Zn2+, Co-2+, Ni2+ or Cd2+). Single-crystal and powder X-ray diffraction show that the four complexes are isomorphous. Due to different electronic configurations for Zn2+, Co2+, Ni2+, and Cd2+, the solid-state fluorescence properties of 1 and 4, and the temperature dependence of magnetic susceptibility of 2 and 3 were investigated, respectively. The results show that 1 and 4 have obvious blue light emission at the range of 310 to 430 nm with 1.37 % of the quantum yield and 3.80 ns of the lifetime for 1 and 1.67 % and 2.43 ns for 4, respectively. Notably, the intensity-based fluorescent temperature sensing reveals that both of them can be used as luminescent thermometers. Magnetic investigation of 2 and 3 reveals that strong antiferromagnetic interactions exist within the paramagnetic centers, Co(II) or Ni(II), with -29.09 K of Weiss constant for 2 and -64.02 K for 3, respectively.