Structure and magnetic properties of a giant Cu44II aggregate which packs with a zeotypic superstructure

Reaction of Cu(II) and the aminopolycarboxylate nitrilotripropionic acid (H(3)ntp) in water leads to the formation of [Cu-44(mu(8)-Br)(2)(mu(3)-OH)(36)(mu-OH)(4)(ntp)(12)Br-8(OH2)(28)]Br-2.81H(2)O. The Cu-44 aggregates have a central inorganic core corresponding to [Cu-24(mu(8)-Br)(2)(mu(3)-OH)(24)(mu-OH)(8)](14+) anchored on two bromide anions, and this is encased in a shell of Cu(II)/ligand units. The aggregates pack into a distorted tetragonal array with a very open structure containing large amounts of water of crystallization. The magnetic properties have been studied and, while complicated by the presence of low-lying excited states, indicate that the individual clusters have nonzero spin ground states.