“…Based on an invariant N 2 O 2 2À planar ligating platform (Scheme 1), the derived polymers {[Fe8(py∪py)]} n show remarkably variable SCO in the solid state, when the axial bridging bipyridine ligand py∪py is varied. [3] While 4,4'-bipyridine as a bridge supports a LS polymer up to 400 K, the equally linear bridge 1,2-bis(4-pyridyl)ethyne traps the HS state even at lowest temperatures. Clearly, such massive differences cannot be associated with the very minor (if any) variations in the ligand-field imposed by the axial ligands; they are governed by packing effects, which are currently beyond control, not to say rational design.…”