Effect of axial ligands removal on the spin crossover in 2D iron tetracyanonickelates

The effect of axial ligands removal on the spin-transition phenomenon was investigated in iron(II) tetracyanonickelate with pyridine, 3-fluoropyridine and 3-chloropyridine as intercalated species. The samples were heated at 190 °C, 210 °C, 230 °C, 250 °C and analyzed in terms of structural stability and changes in spin-crossover phenomenon using infrared spectroscopy, powder X-ray diffraction and magnetometry of superconducting quantum interference device. The results showed that the partial removal of the axial ligands caused a decrease in transition temperatures and a significant reduction in transition hysteresis loops. The spin-transition phenomenon remained even after removing more than 0.8 ligand molecules in Fe(3-fluoropyridine) 2 [Ni(CN) 4 ] and Fe(3-chloropyridine) 2 Ni(CN) 4 ]. The structural stability of the materials depended on π - π type interactions between the aromatic rings and dispersive type forces between the halogen groups in the inter-layer region. The findings provide deeper insight into the post-synthetic modification of spin crossover materials with a view to their application in molecular sensing. • SCO modification by axial ligands removal with thermal treatment in 2D Hoffman type coordination polymers. • Effect of the non-covalent interactions in the structural stability of 2D solids. • Effect of the non-covalent interactions in the SCO phenomena. • Thermal stability in 2D Hoffman type coordination polymers.