EFFECTS OF LIGAND SUBSTITUENTS (F FOR H, OR FOR R) ON MESOGENIC PROPERTIES OF M(SALEN) DERIVATIVES (M=CU, NI, VO) - NEW FLUORO-SUBSTITUTED COMPLEXES AND CRYSTAL-STRUCTURE OF THE MESOGEN NI(S-HEXYLSALEN)

The preparation of new metallomesogens containing fluoro-substituted bis(salicylaldehyde) ethylenediimine (Salen) ligands is reported for the complexes of copper(II), nickel(II), and oxovanadium(IV), in which substitution for individual atoms is shown to have a dramatic effect on packing and mesogenic properties. In other mesogens, fluoro substitution reduces melting points or extends the mesogenic range, or both. By contrast, in the title compounds the melting points are lowered by up to 50 degrees C, while the mesogenicity is eliminated or drastically reduced in range by fluorination, presumed to exert its influence through the dipolar effect. When the allkoxy O atom in Ni(5-(hexyloxy)Salen) is replaced with CH2, the structure changes dramatically from roughly planar to an irregular S-shape, but mesogenic properties are retained. The crystal structure of (5-n-hexylSalen)Ni shows it to be an S-shaped molecule with especially dramatic bending at the n-hexyl chains from their phenyl rings (58, 85 degrees). Crystal data: C28H38N2O(2)Ni, space group P $($) over bar$$ 1, a = 12.640(2) Angstrom, b = 16.872(2) Angstrom, c = 6.650(2) Angstrom, alpha = 98.54(3)degrees, beta = 92.89(3)degrees), gamma = 71.43(1)degrees, Z = 2, R = 5.44%, R(w) = 5.96% for 1612 observed unique reflections. a a a 85''). 98.54(3)degrees, beta = 92.89(3)degrees, gamma = 71.43(1)degrees, Z = 2, R = 5.44%, R(w) = 5.96% for 1612 observed unique reflections.