Chromism of chemical compounds

Chromism, generally a reversible color change of substances, finds vital applications in the fields of switching, catalysis, molecule binding, drug delivery and energy storage applications. Chromism is caused by the change of electronic, conformational, crystal or physical structure of materials due to heat, light, solvent/vapour, applied electric potential, etc. There have been observed different types of chromism such as thermochromism, photochromism, solvetochromism, electrochromism and many others from different compounds. Here in we have discussed different types of chromisms but in brief as inherited by various types of materials. Reversible multicolor chromism by metal halide formamidinium perovskite attests solvetochromism and thermochromism due to the hydrogen bonding. Tetrathiazolylthiophene compound shows mechanochromism because of the structural deformation. Chain length of ligand influences the chromism in copper complex. Gold cluster complex, boron complex, Bi₂WO₆ also display specific chromic performance. Phosphomolybdate – malachite green dye moiety (PMMG) displays hydrochromism because of bridged water molecules. N₂ (or O₂) binding to PMMG has recently been shown as an extension of hydrochromism phenomonon. Thus, this account on chromism from various materials is expected to attract the attention of researchers.