Synthesis and mesomorphic properties of 5-(p-n-alkoxy)phenyl-2-(p-n-octyloxy)benzylideneamino-1,3,4-thiadiazoles

Abstract

A relatively large number of mesomorphic compounds containing heterocyclic units have been synthesized and interest in such structures constantly grows [l, 21. This is not only because of the greater possibilities with heterocyclic rings for the design of new mesogenic molecules, but also because the introduction of heteroatoms can cause considerable changes in polarity, polarizability and sometimes the geometry of a molecule in relation to the geometry with phenyl rings [3, 41. These can greatly influence the types of mesophases which occur, the phase transition temperatures, and the dielectric and other properties of the mesogens [5, 61. Continuing our investigations of compounds with heterocyclic rings [7, 81 we have synthesized new Schiff's bases mesogenic derivatives of 5-(p-n-alkoxy)phenyl-2-amino-l,3,4-thiadiazole. SynthesisSchiff's bases 5a-5f were synthesized according to Scheme I. 1-4 were synthesized through the detailed procedures described in reference [9].The structures for all these compounds were confirmed by IR (Perkin-Elmer 577), 'H NMR, 13C NMR (Bruker AC-250 MHz), using tetramethylsilane as the standard, and elementary analyses ( Table 1).

New Schiff's bases containing 1,3,4-thiadiazole and 1,3,4-oxadiazole units: a study of the effect of the heterocyclic ring and the position of the lateral alkoxy group on liquid crystalline properties

“…This compound was synthesized according to For the oxadiazole derivatives the 's-cis' and 's-trans' reference [8]. conformers have similar stability and co-exist.…”

“…Compound 1 was synthesized starting with the alkylation of methyl 4-hydroxybenzoat e and proceeding with condensation with 80% hydrazine hydrate, yielding 4-n-decyloxyphenylhydrazide ; this was reacted with 996 M Parra et al to the formation of the 4-n-decyloxybenzoylthiosemicarbazide 1 [8].…”

Preliminary communication: The synthesis of new mesogenic 1,3,4‐thiadiazole‐2‐carboxylate esters via a novel ring‐closure

“…Substituents that have been incorporated at the 2-and 5-positions of the 1,3,4-thiadiazole ring include: (a) two aryl units, (b) an alkyl (or cycloalkyl) and an aryl unit, (c) two cycloalkyl units, (d) an alkyl and an amino-based unit (azo, amide or Schiff's base), (e) a perfluoroalkyl and an aryl unit and (f) an aryl and an amino unit (azo, amide or Schiff's base). Examples of such mesogens [1][2][3][4][5][6][7][8][9][10] are shown in figure 1 (I-V).…”

“…1,3,4-Thiadiazoles with nitrogen-based linkers (amides, Schiff's bases or azo groups) at the 2-position have been recently synthesized by Parra and co-workers [6][7][8][9][10]. These materials are derived from 2-amino-1,3,4-thiadiazoles that are obtained via cyclization of the requisite thiosemicarbazides using either sulphuric acid or acetyl chloride in combination with HCl.…”

Symmetric esters derived from 1,3,4-oxadiazole: synthesis, mesomorphic properties and structural study by semi-empirical calculations

“…The homothiadiazole or thiophene rings can be incorporated into logues series of diesters were synthesized by using the principal structure of calamitic mesogens [7][8][9][10][11][12]. In 4-hydroxy-phenylhydrazide as precursor.…”