Polarized single-crystal spectrum of a high-spin trigonal-bipyramidal NiN5 chromophore

The high-spin pentacoordinate nickel(I1) complexes with the quadridentate ligand RIestren (tris(2-dimethylaminoethyl) amine) having general formula [Ni(hleatren) X] X (X = C1, Br, Ij2 are known to be trigonal bipyramidal with a C3v~ ymrne t ry.~D espite their high symmetry, the halo complexes are not suitable for anisotropic measurements because they crystallize in the cubic system. \Ye looked for Mestren derivatives which crystallize in a noncubic system. The thiocyanate derivative has been found to be crystallographically anisotropic, and its electronic spectrum is quite similar to those of the halo analogs. An X-ray structure determination has been undertaken in order to determine the exact geometry of the chromophore and the molecular orientation in the crystal. Such information has been used to discuss the single-crystal polarized spectra The aim of this research is (I) the circumstantiated assignment of the electronic transitions of a trigonal-bipyramidal high-spin nickel chromophore and (11) the study of the spectral and magnetic properties of a 3E ground state which is expected to experience a zerofield splitting.