Spontaneous magnetization below 7.7 K based on an extended 3-D H-bonding network material: Synthesis, crystal structure and magnetic properties

The structure of the complex [4-aminopyridinium][Ni(mnt)₂], as determined by X-ray single crystal analysis, consists of 4-aminopyridinium cations and [Ni(mnt)₂])^- anions. The interactions between anions and cations via the bifurcated N(Py)-H⋯NC H-bonds give rise to a 1-D zigzag chain of alternating cations and anions, and a 3-D H-bonding network through further N(NH₂)-H⋯NC interactions. _χdc and _χac have been measured down to 1.8 K and analysed, indicating the existence of a spin canting phenomenon. Below the critical temperature (around 7.7 K), the sample spontaneously magnetizes, and the hysteresis loop was observed at 1.85 K, corresponding parameters are as follows: H_c = 150 Oe and M_r = 7.9 emu mol^-1. The pathway of the exchange interaction in this complex via H-bonding is discussed in light of the crystal structure analysis.