Syntheses, structural, and spectroscopic properties of copper(II) complexes of constrained macrocyclic ligands

The complexes [Cu(L-1)(H2O)(2)](BF4)(2)center dot 2H2O (1) [L-1 = 5, 16-dimethyl-2, 6, 13, 17-tetraazatricyclo(14, 4, 0(1.18),0(7.12))docosane] and 0.5[Cu(L-2)(NO3)(2)][Cu(L-2)](NO3)(2) (2) [L-2 = dibenzyl-5, 16-dimethyl-2, 6, 13, 17-tetraazatricyclo(14, 4, 0(1.18),0(7.12))docosane] were synthesized and characterized by single crystal X-ray analyses. In these constrained macrocycles, the central copper(II) atoms are in a tetragonally distorted octahedral environment with four nitrogen atoms of the macrocyclic ligands in equatorial positions and oxygen atoms from either water molecules or nitrato groups in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans-III conformation. The CuN distances [1.999(7)2.095(7) angstrom] are typical for such complexes, but the axial ligands are weakly coordinating CuOH2 bonds [2.693(3) angstrom] and CuONO2 bonds [2.873(7) angstrom] due to the combination of the pseudo JahnTeller effect and strong in-plane ligand field. The crystals are stabilized by a three-dimensional network by hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms, oxygen atoms of water molecules, fluorine atoms of BF4, and oxygen atoms of NO3. The electronic absorption and IR spectroscopic properties are also discussed.