Enantiotropic columnar discotic phase

The vast majority of discotic mesogens with cyclohexane cores and six substituent chains are based on ui- and s-IS. Pertinent to the discussion above concerning the relationship between the direction of projection of chains on 1,2,3,4,5,6-hexasubstituted cyclohexanes, the hexa(n-hexyl) ether of m-IS with one axial hexyloxy (6-O-m-IS) has been shown not to be liquid crystalline the corresponding s-IS hexaether with a more disk-like shape (6-O-s-IS) forms an enantiotropic columnar discotic phase... 

It has been shown that a j8-diketonate liquid crystal containing palladium(II) and oxo-vanadium(IV), analogous to known copper complexes (which display discotic lamellar and columnar mesophases), has been prepared and characterized palladium complexes are mesomorphic but their identification is difficult due to their decomposition in the isotropic phase the complex n = 10 seems to present a Nj phase on the basis of optical microscopy. The vanadium complexes are enantiotropic discotic [75], while the vanadium complex, 30, presented by Styring et al. [76] (n= 10), exhibited a short monotropic columnar discotic phase. 

New compounds containing two or even four palladium atoms and eight or twelve flexible side chains have been synthesized by Praefcke et al. [138]. The compound, 58, shows an enantiotropic discotic hexagonal columnar mesophase over a wide range of temperature and a lyotropic nematic phase in various organic solvents. X-ray diffraction studies reveal an oblique arrangement of disordered columns. 

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