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 CH 2 O 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)](CIO 4 ) 2 and [Cu(‘ anti ’‐L)](ClO 4 ) 2 · 1/2 H 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 spectra) and a combination of molecular mechanics and AOM calculations (MM‐AOM) for the solution‐structure behavior.