Relationship between the magnetic field induced orientation in the mesophases of metallomesogens derived from Schiff's bases and their mesophase structure

In this paper the orientation of the mesophase domains of metallomesogens derived from Schiff's bases by the effect of applied magnetic fields is analysed. Particular emphasis is put on the copper compounds; in this case, the orientation depends on the number of aromatic rings in the molecule (four or six) and, when four rings are present, it also depends on the type of molecular structure (2,4-versus 2,5-substitution). These differences are related to the order of the mesophase and can be explained by considering the additional ordering of the short axes. A strong indication of the existence of biaxial order in the mesophase is thus derived. This order is associated with the shape of the molecule which imposes geometrical constraints on the molecular packing.