55834-84-9Relevant academic research and scientific papers
Steric hindrance influence of a diazo link upon mesogenic properties of some ligands and related copper complexes
Lesot,Perez,Judeinstein,Bayle,Allouchi,Cotrait
, p. 1695 - 1714 (2007/10/03)
Some new polymethylated compounds containing three rings and four rings have been synthetized. The crystalline structures of 2,3-dimethyl-4-ethoxy benzoyloxy-4'-(4-methoxysalicylaldimine)-azobenzene (DIM) and 2,3,6- trimethyl-4-methylben zoyloxy-4'-butylazobenzene (TRIM) are described. Due to larger steric interactions, the diazo linkage makes a larger dihedral angle in TRIM than in DIM. The effect of steric hindrance of the diazo linkage upon the mesophase stability is discussed by the use of isotropic Carbon-13 chemical shifts, molecular modelling and transition temperatures, T(NI). For the three rings core, the thermal stability of the mesophase decreases with substitution pattern dissymetry. The effect of the conjugation loss is evidenced by the decrease of T(NI) versus the carbon number within the chain. For the four rings core, the effect on the transition temperatures of polymethylated ligands is nearly independent of the length of the mesogenic core and depends only on the lateral substituent positions within the core. For the related copper complexes; the T(NI) transition temperatures exhibit a small dependence upon the methyl substitution.
