Mesomorphic complexes, group 8 metals

C. Mesomorphic Stilbazole Complexes of Groups 10 and 11 Metals Hydrogen-Bonded Stilbazole Mesogens... 

Takahashi previously reported some structurally related gold systems, 12a and 12b [21]. Complexes 12a showed Sa phases at elevated temperatures (170-270 °C), while the metal-free ligand showed nematic and Sa phases, depending on the chain length. Addition of an alkoxy chain in the ortho position, relatively to the isonitrile group, 12b, depressed considerably the transition temperatures (90-190 °C), and a nematic phase was observed in addition to the Sa phase. Here, complexation induced mesomorphism since the ligand itself was not liquid crystal. 

Several research groups concurrently prepared the same series of metal-free and copper complexes " of octaalkoxy substituted phthalocyanines ((1) M = 2H, Cu, R = OC H2 +i, = 5-14, 18 thermal data collected in Table 3). They observed mesomorphism for all the free-base... 

A series of related metallaazaporphyrins has been studied which differ from the previous examples by the structure of the peripheral chains, which are alkenylsulfanyl groups ((31) M = 2H, Ni, Co, Cu, R = C H2 i, n = 4-6, 7, 8). Thus, the presence of a terminal double bond in the peripheral chains did not preclude mesophase formation, as all the metal complexes exhibited mesomorphism, in addition to the free-base compounds with n = 4 and 5 (Figure 31). Overall, the presence of the terminal double bond reduced the thermal range of the mesophase. 

The second series of related materials was based on the (3,4-didodecyloxyphenyl)diaminodi-oxime derivative (73). Vicinal dioximes are capable of coordinating through N,N or N,0 sites of the oxime groups. Upon the complexation, the ligands fold back, and the transition metal complexes are V,V-coordinated with a square-planar structure. Both isomeric forms were selectively isolated for the nickel complexes, but only the anii-isomer for the palladium complex. The two uwti-complexes complexes exhibited a Colh phase ((73) M = Ni Cr 78 Colh H7 I M = Pd Cr 80 Colh 131 I). Most astonishing, however, was the observation of a Colh phase for the isomeric amphi-mckel complex ( , Z-isomer), between 66 °C and 145 °C. Not only was the existence of mesomorphism surprising and unexpected, but the mesophase stability also increased with respect to the anti-complex. 

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