Related Experiment Video
Updated: Aug 9, 2026
An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation
Published on: February 27, 2019
A chromogenic macrocycle exhibiting cation-selective and anion-controlled color change: an approach to understanding
Soo Jin Lee1, Jong Hwa Jung, Joobeom Seo
1Department of Chemistry and Research Institute of Natural Sciences, Gyeongsang National University, Chinju 660-701, Korea.
Abstract:
[reaction: see text] A N-azo-coupled macrocycle (1) with a NO(2)S(2) donor set was synthesized as a chromoionophore and shown to exhibit Hg(2+) selectivity; anion control of the color of the Hg(2+) complex was observed. As a first approach, the nature of the color generation process was probed by determining the crystal structures of the two different colored species obtained with perchlorate and iodide anions. The results can be explained in terms of a "Push-n-Pull Process", which serves to illustrate how the coordinating ability of the anion controls the color change through formation of endo- or exo-metal complexes. The use of "simple" salts to induce color-switching of the above complex species was also reported.
Related Concept Videos
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
00:39Complexometric Titration: Overview
01:11Aryldiazonium Salts to Azo Dyes: Diazo Coupling
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
01:09Ion-Exchange Chromatography