Spectroscopic investigation on the trichloro-, tetrahalo- and mixed-tetrahalocuprates of the piperidinium and morpholinium cations.

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 Cu2Cl2- 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.