The manifestations of single ion anisotropy of the Dy-III ion in the key physical properties of the [L2Ni2Dy][ClO4] single molecule magnet have been examined. The crystal field acting on the Dy-III ion and the exchange interaction coupling the Dy-III and Ni-II ions are included in the model. It is shown that the role of the Ni-II ions is only to increase the total angular momentum of the cluster via coupling through superexchange with the Dy-III ion. The model describes well the observed temperature dependence of the magnetic susceptibility and the field dependence of magnetization. (C) 2012 Elsevier B.V. All rights reserved.