Synthesis, Mesomorphism, and Spectroscopic Characterization of Bis[4-(n-alkoxy)-5-(p-n-tetradecylphenylazo)]-Substituted(N,N’-Salicylidenediaminato)nickel(II) Complexes

The bis[4-(n-C(m)H(2m+1)O)-5-(p-C(14)H(29)C6H4N=N)]-substituted N,N'- salicylidenediamines H2[L(N)(m,14)] (N = 1: 1,2-diaminoethane; N = 2: 1,3- diaminopropane; N = 3: 1,3-diamino-2,2-dimethylpropane; m = 6 or 18) have been synthesized. Both the N = 2 and 3 series of compounds display a smectic C (SmC) mesophase, with clearing points well below 100 °C. By treating the H2[L(N)(m,14)] ligands with an Ni(II) salt, liquid crystalline mononuclear complexes with 'unconventional' (lateral-tailed) molecular shape form. These Ni[L(N)(m, 14)] complexes, showing nematic and smectic disordered phases, are stable over a quite large temperature range and have been characterized by different spectroscopic techniques. The newly synthesized mesogens exhibit lower transition temperatures and higher thermal stability than homologous complexes Ni[L(N)(14)] with a 'conventional' rod-like molecular geometry.