Four single-phase isostructural mononuclear complexes (HNEt₃)[DyxYb1-x(bpyda)2]·3H₂O (x = 1 (1), 0 (2), 0.367 (3), 0.135 (4), bpyda = 2,2'-bipyridine-6,6'-dicarboxylate) show characteristics of controllable slow relaxation and photoluminescence. The molecular hybrids 3 and 4 exhibit the Orbach process for the DyIII component and a mixture of direct and Raman processes for the YbIII component. The presence of paramagnetic YbIII enhances the relaxation time of the DyIII component, originating from the suppression of the direct process/QTM. The correlation between photoluminescence, static susceptibilities and dynamic magnetic relaxation in the hybrid species was also analysed by comparing the energy gap between the ground and first excited states to the energy barrier.