Copper complexes metallomesogens

Another interesting family of square-planar metallomesogens is that constituted by complexes of enaminoketones. Several copper complexes of type (233a) and (233b), with various n and w, have been synthesized, and when R is an alkoxy (OC H2 +i), alkyl (C H2/j+i), or alkanoate (C02C H2j,+i) group, the complexes are not liquid crystals, or exceptionally showed a monotropic SniA phase. ... 

Carfagna [118] reported the first polymeric metallomesogen with a Schiff-base ligand. The polymer showed a monotropic phase presumably smectic. Later, Caruso et al. [119] showed that a copper complex could give a polymer with nematic behavior. Dif-... 

A series of aroylhydrazinato-nickel and -copper complexes, 62, was synthesized in high yield and shown to form metallomesogens with SmC and N phases around 150 °C. The nickel complexes were found to be highly stable while the copper complexes decompose soon after entering the isotropic phase [144]. 

Metallomesogens have been shown to form helical supramolecular organisations in their mesophases [95]. Chiral oxazoline complexes with various metal ions and six alkyl chains did not show LC behaviour, but when mixed with trinitrofluorenone form achiral smectic A phases [96]. Furthermore, when a branch was included in the structure of the ligands (Fig. 12) the corresponding complexes with copper(II) and palladium(II) form columnar mesophases which have a helical organisation [97]. The presence of the stereogenic centre near the central metal ion in these complexes (Fig. 12) is enough to cause the parallel molecules to stack in a tilted manner with... 

Phthalocyanines represent a class of inherently disc-like molecules and consequently were among some of the first examples of metallomesogens exhibiting columnar mesophases, being first reported by Simon and co-workers in 1982 [122]. Thus, they described an octasubstituted phthalocyanine copper(Il) complex (Figure 65) which exhibited a mesophase between 53°C and the start of decomposition at about 300°C X-ray diffraction studies showed lines with reciprocal spacing of 1 3 v 4 7,... 

Lattermann et al. reported the first metallomesogenic dendrimer when they described results on trigonal bipyramidal metal complexes of ethylene-imine dendrimers of the first and second generation, based on derivatives of tris(2-aminoethyl)amine. Complexes of cobalt, nickel, copper, and zinc were prepared and found to exhibit relatively low temperature mesophases, which generally possessed hexagonal columnar structures. These materials therefore provided the first examples of metallomesogenic dendrimers [72,73]. 

Some of these materials display the potentially chiral ferroelectric SmC phase in addition to a SmA or cholesteric mesophase. Pyzuk [108] found for copper and nickel complexes some blue phase or novel type of amorphous phase between a tightly twisted chiral nematic phase and the isotropic liquid. These ferroelectric metallomesogens are interesting as they can be aligned par-... 

---