Calamitic metallomesogens: metal-containing liquid crystals with rodlike shapes

Article Abstract:

A discussion on the properties, characteristics and structural geometries of various calamitic metallomesogens (CM's) is presented. The phase behavior of the CM's is found to be significantly influenced by the ligands. The structural analysis reveals that geometries about the metal center agrees with calamitic mesomorphisms. Various methodologies in reducing the increase in the transition temperature brought about by the incorporation of metals are also explored. The mesophase behavior of the CM's is justified by the dipole-dipole and van der Waals forces.

Polymers, Thermal properties, Liquid crystals

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Bond-stretch isomerism in transition metal complexes: a reevaluation of crytallographic data

Article Abstract:

The limitations of X-ray crytallography is demonstarted by analyzing the x-ray diffraction data of a cis-mer MoOCl2(Pme2Ph)3 for verification of bond- stretch isomerism. Results suggest that crystallographic disorder (CD) is difficult to detect and an undetected CD may result in both incorrect bond length and incorrect formulation of compunds. Therefore, the possibility of compositional disorder should always be considered when performing X-ray structure determinations especially when unusal bond lengths are obtained.

Evaluation, X-ray crystallography, Isomerism, Isomers (Chemistry)

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Stable carbenes

Article Abstract:

A discussion of developments in carbene chemistry is presented. Issues addressed include the impact of the substituents on the ground-state spin multiplicity and stability of carbenes. It is concluded that it cannot be claimed that carbenes only arise as reactive intermediates.

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