Diverse Solid-State and Solution Structures within a Series of Hexaamine Dicopper(II) Complexes

Mono- and dicopper(II) complexes of a series of potentially bridging hexaamine ligands have been prepared and characterized in the solid state by X-ray crystallography. The crystal structures of the following Cu^II complexes are reported:  [Cu(HL³)](ClO₄)₃, C₁₁H₃₁Cl₃CuN₆O₁₂, monoclinic, P2₁/n, a = 8.294(2) Å, b = 18.364(3) Å, c = 15.674(3) Å, β = 94.73(2)°, Z = 4; {[Cu₂(L⁴)(CO₃)]₂}(ClO₄)₄·4H₂O, C₄₀H₁₀₀Cl₄Cu₄N₁₂O₂₆, triclinic, P1̄, a = 9.4888(8) Å, b = 13.353(1) Å, c = 15.329(1) Å, α = 111.250(7)°, β = 90.068(8)°, γ = 105.081(8)°, Z = 1; [Cu₂(L⁵)(OH₂)₂](ClO₄)₄, C₁₃H₃₆Cl₄Cu₂N₆O₁₈, monoclinic, P2₁/c, a = 7.225(2) Å, b = 8.5555(5) Å, c = 23.134(8) Å, β = 92.37(1)°, Z = 2; [Cu₂(L⁶)(OH₂)₂](ClO₄)₄·3H₂O, C₁₄H₄₄Cl₄Cu₂N₆O₂₁, monoclinic, P2₁/a, a = 15.204(5) Å, b = 7.6810(7) Å, c = 29.370(1) Å, β = 100.42(2)°, Z = 4. Solution spectroscopic properties of the bimetallic complexes indicate that significant conformational changes occur upon dissolution, and this has been probed with EPR spectroscopy and molecular mechanics calculations.