Hydrothermal synthesis, structure and magnetism of square-grid cobalt(ii)-carboxylate layered compounds with and without pillars

Abstract

The hydrothermal synthesis, single crystal X-ray structures and magnetic properties of two layered cobalt(II)-carboxylate complexes, ²_∞[Co^II(H₂O)₂(O₂CCHCHC₆H₅)₂] (1) and ²_∞[Co^II(H₂O)₂(O₂CCHCHC₆H₄CO₂)_2/2] (2), are described. Pale red crystals of Co(H₂O)₂L₂, L = trans-cinnamate (C₉H₇O₂⁻) (1) or L₂ = 4-carboxycinnamate (C₁₀H₆O₄²⁻) (2), were obtained at 120 °C. The structures consist of square-grid 2D-coordination polymeric sheets, ⋯–OCO–Co(H₂O)₂–OCO–Co(H₂O)₂–⋯, separated by C₆H₅–CHCH– for (1) or pillared by –C₆H₄–CHCH– for (2). The magnetism was studied as a function of temperature and magnetic field. In both cases the magnetic moment decreases on lowering the temperature due to spin–orbit coupling and no interaction between cobalt ions. The data can alternatively be fitted to an unrealistic quadratic layer model for S = 3/2 without taking into account the effect of spin–orbit.