Room Temperature Operational Thermochromic Liquid Crystals

Thermochromic liquid crystals operating in the room temperature region have been successfully designed and synthesized. The reaction of 3,5-dialkoxy-N-4H-1,2,4-triazol-4-ylbenzamide ligands with Fe(4-MeC6H4SO3)2 salt have afforded a family of complexes with the general formula [Fe(Cn-trz)3](4-MeC6H4SO3)2·H2O, n being the number of carbon atoms of the alkyl chain (8 (1), 10 (2), and 12 (3)). It appears that spin-crossover (SCO) behavior occurs in the temperature range at which the materials show a discotic columnar mesophase Dhd. As a result of the ability of liquid crystals to form thin layers, it is possible to obtain thermochromic SCO films. Understanding of possible interplay/synergy between the different phase transitions occurring in these materials is still a perspective study but certainly is exciting and attractive to chemists as well as physicists.