Figure 4.

Schematic representation of group–subgroup relationships between the four phases of [Mn^III(3,5-diCl-sal₂(323))]BPh₄ (1). Pc, P1, and P1_(1/2) are each subgroups of Cc (blue lines) but do not have a group–subgroup relationship between them. Arrows on solid lines indicate the sequence of transitions with decreasing temperature. The Cc and Pc structures are related by the order parameter q_Y1, which belongs to the irrep Y₁, and the transition is allowed by symmetry to be second order. The Cc and P1 structures are related by the order parameter q_V1, which belongs to the irrep V₁. Cc and P1_(1/2) structures are related by the order parameter q_Γ2, which belongs to the irrep Γ₂. In the absence of group–subgroup relationships between the three lower temperature structures, transitions between them must necessarily be first order in character.