The structure of an isomeric pair of a (tetraamine)copper(II) compound in the solid state and in solution

The template condensation of [Cu(3,2,3-tet)](2+) (3,2,3-tet = N,N ''-(ethane-1,2-diyl)propane-1,3-diamine with CH2O and en (en = ethane-1,2-diamine) affords the copper(II) compounds of two isomeric tricyclic ligands in high yield. The strikingly different UV/VIS and EPR spectroscopic behavior of these two compounds, [Cu('syn'-L)](ClO4)(2) and [Cu('anti'-L)](ClO4)(2) . 1/2H(2)O (L = 1,4,8,10,13,15-hexaazatricyclo [13.3.1.1(4,8)]icosane), is analyzed by angular overlap model (AOM) calculations based on the experimentally determined solid-state structures (powder spectral and a combination of molecular mechanics and AOM calculations (MM-AOM) for the solution-structure behavior.