With maleate, [Cu5(ahpha)4]2+ gives two complexes, [Cu5(ahpha)4(DMF)2](MalH)2·2DMF (1) and [Cu5(ahpha)4(MalH)2] (2) (ahpha2– is 3-amino-3-hydroximinopropane hydroxamate; MalH2 is maleic acid). Both 1 and 2 contain non-oligomerized [Cu5(ahpha)4]2+ metallacrown blocks; in 1, two MalH– are bound to [Cu5(ahpha)4]2+ only via H-bonds, while in 2, they coordinate to Cu2+. The X-band EPR of 1 was observed at 20 K, 100 K, and 295 K. The EPR at 20 K was of an S = 1/2 ground state, while at room temperature anisotropic |ΔMs| = 1 and |ΔMs| = 2 resonances around 3200 G (g ≈ 2.19) and 1600 G (g ≈ 4.25) were observed for the Cu5 system, due to partial occupation of an S = 3/2 state. The room temperature EPR of 1 was simulated as the weighted sum of the spectra of its various S = 1/2, 3/2, and 5/2 states. Its magnetic behavior was fitted with a χMT vs. T model using a spin Hamiltonian accounting for central–peripheral (J1), peripheral–peripheral (J2) Cu2+–Cu2+ and intercrown (zJ′) spin interactions, yielding J1 = –156(4) cm–1, J2 = –63(1) cm–1, and zJ′ = –4.5(3) cm–1. For sorption of methanol and ethanol vapors at 293 K by a desolvated polycrystalline sample of 1, the shape of the adsorption and desorption isotherms indicated a “gates opening” phenomenon.
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry