Host-Guest Interaction of 12-MC-4, 15-MC-5, and Fused 12-MC-4 Metallacrowns with Mononucleart and Binuclear Carboxylato Complexes: Structure and Magnetic Behavior

摘要

Interaction of manganese with salicylhydroxamic ligands leads to the formation of the 12-membered metallacrown [Mn_2~(II)(2,4-DP)_2(HCOO)_2]-[12-MC_(Mn~(III)N(shi))-4](py)_6 (2) (H-2,4-DP=2-(2,4-dichlorophenoxy)propionic acid) and the 15-membered metallacrown [Mn~(II)(2,4-D)__2[15-MC(Mn~(III)N(shi))-5](py)_6 (1) (H-2,4-D=2,4-dichlorophenoxyacetic acid). The crystal structure analysis shows that mononuclear and dinuclear alkanoato complexes are accommodated in the cavity of the metallacrown ring. The magnetic behaviour of 1 and 2 and the magnetic behaviour of the fused 12-membered metallacrown [Ni~(III)(mcpa)]_2-[12-MC_(Ni~(III)N(shi)_2(pko)_2)-4][[12-MC_(Ni~(III)N(shi)_3(pko))-4]-(CH_3OH)_3(H_2O) (3) (Hmcpa=2-methyl-4-chlorophenoxyacetic acid) have shown that the zero field and/or the population of many energy levels at low temperatures is the reason for the divergence of the susceptibility data at high fields. For compound 3, the ground state is S=0, with S=1 and S=2 low-lying excited states. This leads to a non-Brillouin behaviour of the magnetisation, since the ground state is very close to the excited states.