Boron Clusters in Liquid Crystals

Four Decades of Organic Chemistry of closo-Boranes: A Synthetic Toolbox for Constructing Liquid Crystal Materials. A Review

“…Formation of esters from carboranecarboxylic acids is typically accomplished in high yield by using carboxylic acid chlorides and an alcohol or phenol in the presence of pyridine or Et 3 N (Scheme 8) 17,19,20 . The chlorides of either C-or 157,162 .…”

“…Exploration of boron clusters as structural elements for liquid crystals is the most recent chapter in the chemistry and application of closo-boranes 15 . So far only several of the ten clusters, decaborate 7 (refs 16,17 ), monocarbaborate 2 (ref. 18 ), and para-carboranes 6 and 10 (refs 17,[19][20][21][22][23] ), have been used in the synthesis of liquid crystals.…”

“…So far only several of the ten clusters, decaborate 7 (refs 16,17 ), monocarbaborate 2 (ref. 18 ), and para-carboranes 6 and 10 (refs 17,[19][20][21][22][23] ), have been used in the synthesis of liquid crystals. The results obtained to date 15 demonstrate the structural versatility of these compounds and their enormous potential in the study of the phenomenon and applications of liquid crystals.…”

“…Therefore the substitution reactions give good and very good yields only for small nucleophiles, but as the hydrocarbon substituents become dominant in the nucleophile molecule (e.g. 4-heptyloxypyridine) 16,17 , the yield diminishes.…”

“…136 ) provide unique access to a variety of electrically neutral diapical homo-and heterodisubstituted [1-LB 10 H 8 -10-L′] (Scheme 11). Thermal decomposition of the dinitrogen derivatives at temperatures above 100°C in neat Lewis bases such as substituted pyridine 16,17 , ammonia 16,131 , and N,N-dimethylthioformamide 16,152 , among others [131][132][133] yields the substitution product. The reaction presumably proceeds through heterolytic cleavage of the B-N bond and the resulting highly energetic intermediate reacts with the available nucleophile, even with benzene and cyclohexane 131 .…”