Donor-Set-Induced Coordination Sphere and Oxidation-State Switching in the Copper Complexes of O2S2X (X = S, O and NH) Macrocycles

Reaction of the O2S2X-macrocycles (L 1 , X = S; L 2 , X = NH; and L 3 , X = O) with Cu(ClO4)2·6H2O affords 1:1 (M/L) square-pyramidal Cu(II) complexes when X = S and NH but yields a rare 1:2 sandwich-type tetrahedral Cu(I) complex when X = O; the X-ray structures of all three complexes are reported. Substitution of O for S or NH in the ligand structure thus results in a donor-set-induced II/I oxidation state change of the copper, and this is accompanied by a square-pyramidal to tetrahedral topological change in the solid state. Spectrophotometric titration data (including Job plots) indicate that similar behavior occurs in acetonitrile. In further experiments aimed at investigating the generality of the above redox behavior, it was shown that the 16- and 18-membered analogs of the 17-membered L 3 also induce a similar II/I redox change in acetonitrile. It was demonstrated for L 3 that the above-induced Cu(II/I) change is also maintained when the reaction solvent is changed from acetonitrile to methanol or ethanol.