Inorganic Chemistry, Vol.52, No.22, 12872-12874, 2013
Correlation of the Electronic and Geometric Structures in Mononuclear Copper(II) Superoxide Complexes
The geometry of mononuclear copper(II) superoxide complexes has been shown to determine their ground state where side-on bonding leads to a singlet ground state and end-on complexes have triplet ground states. In an apparent contrast to this trend, the recently synthesized (HIPT(3)tren)(CuO2 center dot-)-O-II (1) was proposed to have an end-on geometry and a singlet ground state. However, reexamination of 1 with resonance Raman, magnetic circular dichroism, and H-2 NMR spectroscopies indicate that 1 is, in fact, an end-on superoxide species with a triplet ground state that results from the single (CuO2 center dot-)-O-II bonding interaction being weaker than the spin-pairing energy.