SPECTROSCOPIC INVESTIGATION ON THE TRICHLORO-, TETRAHALO- AND MIXED-TETRAHALO-CUPRATES OF THE PIPERIDINIUM AND MORPHOLINIUM CATIONS

Abstract

Some halo- and mixed-halo-cuprates of the type CuCl₃ · L, CuCl₄ · L₂, CuCl₃Br · L₂, CuCl₂Br₂ · L₂ and CuBr₄ · L₂, were prepared and characterized by means of far-i.r., i.r. and n.i.r. spectroscopy, magnetic moments and conductivity measurements. A band at 19000 cm⁻¹, which appears only in the CuCl₃ · L complexes, is characteristic of Cu₂Cl^2- ₆ dimer or polymer species. For these complexes and for CuCl₄(Morph)₂ and CuCl₃Br(Morph)₂ (Morph = morpholinium cation) an approaching square-planar geometry, while for all the other complexes a distorted-tetrahedral geometry, may be suggested from their spectroscopic properties, compared to those of other tri- and tetra-halo-cuprates of known structure. An intermediate structure between these geometries may be proposed for the CuCl₃ · Pipd complex. The planar geometry is probably stabilized by extensive NH … Cl hydrogen bonding interactions greater with the morpholinium cation than with the piperidinium cation. No thermochromic behaviour in the solid state in the 290–370° K temperature range is observed. The room-temperature magnetic moments agree with the proposed configurations.