In the current study, two salenSchiff base ligands derived from the condensation of ethylendiamine on salicylaldehyde and 5-chlorosalicylaldehyde, namely, N,N’-bis( salicylidene)ethylene-diamine(L1) and N,N’-bis(5-chlorosalicylidene)ethylene-diamine (L2)as well as two of their iron(III) and nickel(II) complexes were prepared, and then used as doping agents of two thermotropic liquid crystals of cyanobiphenyle type, namely, 4-cyano-4’-n-pentyl (5CB) and 4′-n-octyl-4-cyano-biphenyl (8CB). The study of the mesophase of pure and doped liquid crystals was carried out by UV-visible spectroscopy equipped with a heating compartment for precise temperature control, differential scanning calorimetry and polarized optical microscopy. The characteristic transition temperatures, nematic-isotropic, TNI, and/or smectic-nematic, TSN, of liquid crystals based systems were measured and then compared to those of the literature concerning pure 5CB and 8CB. Optical microscopy has shown the existence of Schlieren and focal conic textures of the nematic and smectic states respectively, both of pure and doped liquid crystals. The homogeneity of the obtained guest-host systems was proven by the linear evolution of their transition temperatures as function of the concentration in solute, with correlation factors near to unity.