Discotic Liquid Crystals of Transition Metal Complexes, 2: The Effect of Alkyl Chain Length on Discotic Mesomorphism in Bis[1,3-di(p-n-alkylphenyl)propane-1,3-dionato]copper(II)

Abstract

A Series of disk-like complexes, bis[l,3-di(p-n-alkylphenyl)propane-l,3-dionatolcopper(II) (n-alkyl: R-C_nH_2m+1 n=o−12; C_n-Cu(II)), have been synthesized in fousing our interest on the effect of the alkyl chain lenght for the discotic mesomorphism. It was found that each of the cooper(II) complexes substituted by R[dbnd]C₄H₉-C₁₂H₂₅(C₄-Cu(II)-C₁₂-Cu(II)) is a discogen, and that each of teh complexes from C₇-Cu(II) to C₉-Cu(II) has plural discotic mesophases. C₉-Cu(II) has three discotic mesophases which is the first example in transition metal complexes. Each of the complexes, C_n-Cu(II) (n=5−7,9−11), has two solid polymorphs with different m.p.s. in monotropic relationship. Eaxh o the ligands substituted by R[dbnd]C₇H₁₅-C₁₂H₂₅(C₇-Ligand - C₁₂-Ligand) is a smetogen. It became to be clear that teh discotic mesogen complexes can be otained eve when the non-mesomorphic ligands (n=4-6) are used.

Key Words:

• discotic mesophase
• bis(β-diketonato)copper(II) complexes
• alkyl chain length effect