Distortional isomerism in copper(II) nitrato complexes of N,N',N"-tris{[(para-nitrobenzyl)phenyl]aminoethyl}amine

The tris(aminoethyl)amine derivative tris [(para-nitrobenzyl) phenyl]aminoethyl amine [(p-NO2BP)(3)tren] was reacted with copper(II) nitrate in thf to yield three different solvates of [Cu(p-NO2BP)(3)trenNO(3)]NO3 (C1) in the solid state, namely alpha-C1 center dot 2thf (C2), beta-C1 center dot 2.5thf (C3) and alpha-C1 center dot(thf)(1.5)center dot(iPr(2)O)(0.25) (C4). The light green-yellow coloured complexes, C2 and C4, are different solvates of the one distortion isomer, while the dark-green C3 is a different distortion isomer. The spectral properties of these distortion isomers were examined, and the structures of C3 and C4 were determined by Xray crystallography. The difference in the physical properties (EPR and reflectance electronic spectra) of the light and dark green solids of C1 (alpha-C1 center dot 2thf and beta-C1 center dot 2.5thf) can be attributed to a change in the coordination mode of the ligand to the CuII centre. While the coordination sphere and orientation of the donor atoms in C3 and C4 are similar and the axial Cu-N and Cu-O distances identical, their equatorial bond lengths [Cu(1)-N-eq] differ significantly. Compound C4 was found to have a more uniform distribution of Cu(1)-N-eq bond lengths [2.166(3)-2.232(3) angstrom] than C3 [2.077(3)-2.352(3) angstrom], one Cu-N-eq distance being unusually long, when compared with similar bonds in a range of copper(II) complexes of tren derivatives.