Intermolecular interactions between imidazole derivatives intercalated in layered solids. Substituent group effect

This study sheds light on the intermolecular interactions between imidazole derive molecules (2-methyl-imidazole, 2-ethyl-imidazole and benzimidazole) intercalated in T[Ni(CN)₄] layers to form a solid of formula unit T(ImD)₂[Ni(CN)₄]. These hybrid inorganic-organic solids were prepared by soft chemical routes and their crystal structures solved and refined from X-ray powder diffraction data. The involved imidazole derivative molecules were found coordinated through the pyridinic N atom to the axial positions for the metal T in the T[Ni(CN)₄] layer. In the interlayers region ligand molecules from neighboring layers remain stacked in a face-to-face configuration through dipole-dipole and quadru-pole-quadrupole interactions. These intermolecular interactions show a pronounced dependence on the substituent group and are responsible for an ImD-pillaring concatenation of adjacent layers. This is supported by the structural information and the recorded magnetic data in the 2-300 K temperature range. The samples containing Co and Ni are characterized by presence of spin-orbit coupling and pronounced temperature dependence for the effective magnetic moment except for 2-ethyl-imidazole related to the local distortion for the metal coordination environment. For this last one ligand a weak ferromagnetic ordering ascribed to a super-exchange interaction between T metals from neighboring layers through the ligands π-π interaction was detected.