The dimeric molecule [Dy-2(acac)(6)(MeOH)(2)(bpe)]center dot bpe center dot 2MeOH (1, acac = acetyl-acetonate, bpe = 1,2-bis(4-pyridyl)ethylene) undergoes a solidstate ligand substitution reaction upon heating, leading to the one-dimensional chain [Dy(acac)(3)(bpe)(n) (2). This structural transformation takes advantage of the potential coordination of the guest bpe molecules present in 1. In both complexes the Dy(III) ions adopt similar octatoordinated D-4d geometries, However, the different arrangement of the negatively charged and neutral ligands alters the direction of magnetic anisotropy axis and the energy states, thus resulting in largely distinct magnetization dynamics, as revealed by the CASSCF/RASSI calculations.