Host-guest interaction of 12-MC-4, 15-MC-5, and fused 12-MC-4 metallacrowns with mononuclear and binuclear carboxylato complexes: structure and magnetic behavior.

Interaction of manganese with salicylhydroxamic ligands leads to the formation of the 12-membered metallacrown [Mn(II)(2(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(II)(mcpa)]2-[12-MC(Ni(II)N(shi)2(pko)2-4][12-MC(Ni(II)N(shi)3(pko)-4]-(CH3OH)3(H2O) (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.