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 b is(salicylaldehyde) ethylenediimine (Salen) ligands is reported for th e complexes of copper(II), nickel(II), and oxovanadium(IV), in which s ubstitution for individual atoms is shown to have a dramatic effect on packing and mesogenic properties. In other mesogens, fluoro substitut ion 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 thro ugh the dipolar effect. When the allkoxy O atom in Ni(5-(hexyloxy)Sale n) is replaced with CH2, the structure changes dramatically from rough ly planar to an irregular S-shape, but mesogenic properties are retain ed. The crystal structure of (5-n-hexylSalen)Ni shows it to be an S-sh aped molecule with especially dramatic bending at the n-hexyl chains f rom 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, b eta = 92.89(3)degrees, gamma = 71.43(1)degrees, Z = 2, R = 5.44%, R(w) = 5.96% for 1612 observed unique reflections.