The structure of the cyclidene ligand in the corresponding iron(II)-centered dioxygen carrier has been altered by the addition of gem-dimethyl groups to increase the bulk on the saturated rings of the parent macrocycle. Dramatic responses are found in the dioxygen affinities of the resulting complexes. Placing the bulky group to the rear of the cavity, within which the O2 binds, enhances the O2 affinity, while placing the group at the entry greatly decreases the affinity. The presence of bulky groups at both positions essentially stops the binding of O2. Interpretations are based on the crystal structure data and molecular modeling. X-ray structure data for [DMNiDM(Me2Me2Mxylcyclidene)](PF6)2: NiC32H48N6O2F12, monoclinic, P21/c, a = 13.541 (4) Å, b = 15.408 (5) Å, c = 20.471 (7) Å, β = 106.10°, V = 4103 (2) Å3, Z = 4, R = 0.083, and Rw = 0.091 for 3302 reflections with I > 2.0σ.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry