Double Melting Behavior of Disk-like Complexes Substituted by Long Chains, 1: the Substituent Effect

Abstract

The bis (β-diketonato) copper (II) complexes, 2c and 2d. exhibit double melting behavior; 2c (m.p. of K₁:122.4 - 122.8[ddot]C, m.p. of K₂:135.2 - 135.6[ddot]C), 2d (m.p. of K₁:168.8 - 169.2[ddot]C. m.p. of K₂:208.3 - 208.6[ddot]C). The corresponding β-diketone ligands, 1c and 1d, also exhibit double melting behavior; 1c (m.p. of K₁:83.4 - 83.9[ddot]C. m.p. of K₁:84.9 - 85.4[ddot]C). 1d (m.p. of K₁:103.5 - 103.6[ddot]C, m.p. of K₂:108.1 - 108.2[ddot]C). 2c and 2d are the first examples exhibiting double melting behavior in the disk-like transition metal complexes substituted by long chains. Because the previously reported complexes (2a and 2b) exhibit discotic mesomorphism, the double melting behavior of 2c and 2d is thought of as thermal behavior close to mesomorphism. The chief determining factors which lead to either mesomorphism or double melting behavior are the substituent effect and the effect of central metal.