A molecular dysprosium(iii) complex [Dy(DClQ)3(H2O)2] (1) was used as a building unit for the construction of lanthanide SMMs, leading to the isolation of two dinuclear Dy(iii) complexes, namely [Dy2(DClQ)6(MeOH)2] (2) and [Dy2(DClQ)6(bpmo)2]·6MeCN (3) (DClQ = 5,7-dichloro-8-hydroxyquinoline, bpmo = 4,4′-dipyridine-oxide). Structural analyses revealed the same N3O5 coordination environment of the Dy(iii) centers with a distorted biaugmented trigonal prism (C2V symmetry) and triangular dodecahedron (D2d symmetry) for 2 and 3, respectively. Magnetic studies revealed the presence of ferromagnetic and weak antiferromagnetic exchange interactions between the Dy3+ centers in 2 and 3, respectively. Interestingly, slow relaxation of magnetization at zero fields was evidenced with an Ueff of 51.4 K and 159.0 K for complexes 2 and 3, respectively. The detailed analysis of relaxation dynamics discloses that the Orbach process is dominant for 2 whereas Raman and QTM play an important role in 3. Theoretical calculations were carried out to provide insight into the magnetic exchange interactions and relaxation dynamics for the complexes. Due to a single-ion magnet (SIM) of 1, the foregoing results demonstrate a SIM modular synthetic route for the preparation of dinuclear lanthanide SMMs. © 2022 The Royal Society of Chemistry.