Synthesis and characterisation of Acylhydrazinatometallomesogens

Abstract

Previous work at this institute involved the synthesis and characterisation of Ni2 complexes based on the N-alkylideneacylhydrazine ligand. The primary aims of this project were to synthesise and characterise a series of metallomesogens based on the N-allcylideneacylhydrazine ligand by studying the alternation of mesophase to mesophase and mesophase to isotropic phase transition temperatures whilst ascending a homologous series.
The N-alkylideneacylhydrazinato metallomesogens were synthesised and later characterised spectroscopically. The effects of structural change on mesophase character was deternthed by polarising microscopy and differential scanning calorimetry.
The structural alterations were, varying the alkoxy chain length of known acylhydrazinato-metallomesogens to give odd chain length homologues and the introduction of the 4-phenylazo moiety into acylhydrazinato-metallomesogens. The synthesis of bis[N-methylidene(4'-n-a1koxybenzoyl)hydrazinatonickel(ll) complexes proved successful, exhibiting nematic phases at short chain lengths and smectic C at longer chain lengths. The variation of chain length produced an odd-even effect in mesogen to mesogen and mesogen to isotropic transition temperatures, which decreased as the homolgous series was ascended.
bis[N-Methylidene(4-(4'-n-alkoxyphenylazo)benzoyl)hydrazinato]nickel(II) complexes were synthesised successfully, their transition temperatures were significantly higher than their alkoxy analogues and they only exhibited the nematic
mesophase, with significant decomposition and without reaching their clearing temperatures. The variation of chain length proved successful in exhibiting an oddeven effect in mesogen to mesogen and mesogen to isotropic transition temperatures
which was much more pronounced with the bis[N-methylidene(4-(4'-n-alkoxyphenylazo) benzoyl)hydrazinato]nickel(II) complexes than with the bis[N-methylidene(4'-n-alkoxybenzoyl)hydrazinato]nickel(ll) complexes.