Synthesis, characterization and thermal properties of copper (II) complex as potential metallomesogen compound / Mashyitah Johari

Metallomesogens are metal-containing liquid crystals. The metallomesogens produced from alkoxy groups and short-chain Schiff base ligands are poorly understood. This research aims to learn more by creating a new potential metalomesogen with a short chain spacer and a substituent with a long alkoxy group that may be utilized to create inexpensive electronic device. The main objectives of this research are to synthesize and elucidate the structure of Schiff base ligand(H2L1) and its Copper (II) complexes(CuL1 and CuL1C16) and to study the thermal stability behaviour for the Cu(II) complex. In this study, H2L1 wassuccessfully synthesized by refluxing 2,5-dihydroxybenzaldehyde and ethylenediamine in ethanol as a solvent for 1 hour. Next, CuL1 also successfully synthesized by refluxing H2L1 with copper (II) acetate monohydrate in ethanol as solvent for 3 hours. Furthermore, a new potential metallomesogen derivedfrom the salen-typeSchiff base with two carbon chain substituent with the long terminal end alkoxy group (hexadecane) coordinated with Cu(II) metal (CuL1C16) was also synthesized by refluxing CuL1 with 1-bromohexadecane in DMF as solvent for 4 hours. All the structures were characterized by FTIR and 1HNMR spectroscopies, and the geometry of the metal centre was established by UV-Vis spectroscopy. It has been observed from FTIR spectroscopy that an acetate ion CH3COO is present in the chelating binding mode in both Cu(II) complexes CuL1 and CuL1C16 (Δ = νasym - νsym = 92 cm-1 & 93 cm-1, respectively). Square planar geometry at the metal centre has been inferred from the UV-Vis data of the two complexes. On the other hand, TGA was conducted to study the effects of the Cu(II) complex on the thermal properties of CuL1 and CuL1C16. The Cu(II) complex of CuL1 was expected to have high thermal stability. However, the TGA of the CuL1C16 complex could not be carried out because the instrument malfunctioned. The CuL1C16 complex consists of two Cu(II) metal centres, each bonded to two acetate ions in a chelating binding and coordinated with the long alkyl chain (alkoxy group) of hexadecane (C16), evidenced by FTIR. This suggests that the Cu(II) complex may have potential as a metallomesogen,exhibiting mesomorphic behaviour.