Bond distance, vibrational frequency and dissociation energy of Re-2, Os-2 and Ir-2 were studied by density functional methods B3LYP, BLYP, B3PW91, BHLYP, BP86, B3P86 and PBE1PBE. Spin multiplicity 7 is the ground state for Os-2, 5 for Ir-2. For Re-2, the ground state spin multiplicity is sensitive to the density functionals. Spin multiplicity 5 is the ground state for B3LYP, B3PW91, B3P86, and PBE1PBE, while triplet state is the ground state for BLYP, BP86, and BHLYP. The calculated bond distances are less sensitive to the methods used, while it is not true for vibrational frequencies and dissociation energies. (C) 2005 Elsevier B.V. All rights reserved.