Metallomesogens—Supramolecular

Brace, Duncan, W., Metallomesogens — Supramolecular Organization of Metal Complexes in Fluid Phases,... 

Metallomesogens— Supramolecular Organization of Metal Complexes in Fluid Phases... 

S. R. Collinson and D. W. Bruce Metallomesogens-Supramolecular Organisation of Metal Complexes in Fluid Phases, in Perspectives in Supramolecular Chemistry Transition Metals in Supramolecular Chemistry, vol. 5 (ed. J. P. Sauvage), Wiley, Inc., New York, 1999, pp. 285-369. 

Metallomesogens—Supramolecular Organization of Me Complexes in Fluid Phase Collison and Bruce) 5 285 Metal Template Control of Self-Assembly in Supramolecular Chemistry Fredericks and Hamilton) 3 1... 

Trzaska and co-workers showed a similar propeller mechanism for the formation of helical columns from disclike metallomesogens (29-31).34 These metallomesogens also have C3 symmetry and 30 and 31 are provided with chiral side chains. In the hexagonal columnar mesophase these chiral side chains induce a Cotton effect in the chromophore of the helically arranged core. Heating the mesophase to the isotropic liquid results in the disappearance of the Cotton effect because of the loss of helical order. This effect illustrates the need for the molecules to be positionally ordered in order for the side-chain chirality to be transferred to the supramolecular column. 

Keywords Crown compounds Liquid crystals Mesophases Metallomesogens Polymers Salt effects Self-assembly Substituent effects Supramolecular chemistry Phthalocyanines Cyclophanes... 

Barbera J, Cavero E, Lehmann M, Serrano J-L, Sierra T, Vazquez JT (2003) Supramolecular helical stacking of metallomesogens derived from enantiopure and racemic polycatenar oxazolines. J Am Chem Soc 125 4527-4533... 

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... 

There is debate in the literature as to whether, in general terms, such (supramolecular) intermolecular interactions are important in determining the mesomorphism in metallomesogens where the metal centres are coordinatively unsaturated. In this palladium system, this was investigated using EXAFS [32], which showed that the intermolecular Pd-S contacts could not be observed in the smectic C phase. 

Ferrocene (Fc) possesses a rich synthetic chemistry, a three-dimensional structure which allows the preparation of many derivatives, high thermal stability, and good solubility in common organic solvents. These characteristics allow the synthesis of a great variety of liquid-crystalline materials. Furthermore, its unique electrochemical properties (fast and reversible one-electron transfer process) make Fc a valuable building block for the elaboration of redox-active supramolecular switches. In 30 years (1976-2006), liquid-crystalline ferrocenes have been established as a versatile class of metallomesogens. The aim of this chapter is to highlight the main results obtained for... 

There are many metal complexes, metallomesogens, which deomonstrate liquid crystal or mesomorphic properties, and the organization of metal complexes in fluid phases is definitely supramolecular behaviour. These compounds were well reviewed in 1991 [20a], 1992 [20b] and 1993 [20c] the strength of this research in Europe and Japan is evident. 

Twin-like, bis-linear di-palladium meso-gens of type 47 which thermotropically exhibit smectic phases [159] form lyotrop-ically different variants of supramolecular packings depending on the length and type of their four substituents as well as on the chain length of the organic solvent [154, 155], In contrast to 45 such //-shaped metallomesogens are lyotropic liquid crystalline only without TNF. 

N.V. Usol tseva [ Lyotropic Liquid Crystals Chemical and Supramolecular Structure (IvGU, Ivanovo, Russia, 1994, ISBN 5-230-02212-4) ] T. Sierra [ in Metallomesogens - Synthesis, Properties and Applications Ed. J.L. Sorano (VCH, Weinheim, 19%, ISBN 3-527-29296-9) ch.2 p.29 J M.R. Kuzina, A. Saupe [ in Handbook of Liquid Crystal Research Eds. P.J. Collings, J.S. Patel (Oxford University Press, 1997, ISBN 0-19-508442-X) ch.7 p.237 ] J. Lydon [ in Handbook of Liquid Crystals Eds. D. Demus, J. Goodby, G.W. Gray, H.-J. Spiess, V. Vill (Wiley-VCH, Weinheim, 1998, ISBN 3-527-29491-0) voI.2B ch.XVIII p.981 ] D. 

---