A series of seven isostructural homodinuclear lanthanide complexes are reported. The magnetic properties (ac and dc SQUID measurements) are discussed on the basis of the X-ray structural properties which show that the two lanthanide sites are structurally different. MCD spectroscopy of the dysprosium(III) and neodymium(III) complexes ([Dy-2(III)(L)(OAc)(4)](+) and [NdIII2(L)(OAc)(4)](+)) allowed us to thoroughly analyze the ligand field, and high-frequency EPR spectroscopy of the gadolinium(III) species ([Gd-2(III)(L)(OAc)(4)](+)) showed the importance of dipolar coupling in these systems. An extensive quantum-chemical analysis of the dysprosium(III) complex ([DyIII2(L)(OAc)4](+)), involving an ab initio (CASSCF) wave function, explicit spinorbit coupling (RASSI-SO), and a ligand field analysis (Lines model and Stevens operators), is in full agreement with all experimental data (SQUID, HF-EPR, MCD) and specifically allowed us to accurately simulate the experimental chi T versus T data, which therefore allowed us to establish a qualitative model for all relaxation pathways.