Room Temperature Operational Thermochromic Liquid Crystals

Abstract

Thermochromic liquid crystals operating in the room temperature region have been successfully designed and synthesized. The reaction of 3,5-dialkoxy- N- 4 H -1,2,4-triazol-4-ylbenzamide ligands with Fe(4-MeC 6 H 4 SO 3 ) 2 salt have afforded a family of complexes with the general formula [Fe(C n -trz) 3 ](4-MeC 6 H 4 SO 3 ) 2 ·H 2 O, 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 D hd . 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.