A pentanuclear dysprosium cluster, [Dy-5(mu(3)-OH)(6)(Acc)(6)(H2O)(10)]center dot Cl-9 center dot 24H(2)O (1), has been synthesized through the reaction of 1-amino-cyclohexanel-carboxylic acid (Acc) and DyCl3 center dot 5H(2)O. Crystal structural analysis reveals that the metal core of cluster 1 shows an unprecedented trigonal bipyramidal (TBP) geometry. Magnetic studies indicate that the Dy-5 cluster exhibits slow magnetic relaxation.