Evaluating Chromotropismwith a Spectrophotometer: Solvatochromism and Thermochromism

User Benefits

- Observe changes in absorbance while varying sample temperatures. - The TCC-100, a thermoelectrically temperature-controlled cell holder controls sample temperatures in the range of 7 to 60 °C without the need for cooling water. - The CPS-100, a six-cell thermoelectrically temperature-controlled cell positioner controls the temperatures of up to six samples concurrently.

Introduction

Reversible changes in optical properties due to external stimuli are referred to collectively as chromotropism. For example, the changing of a color from exposure to light is called photochromism, from heat is called thermochromism, and from a change in solvent polarity is called solvatochromism. These chromotropic phenomena have everyday applications, such as checking moisture absorption with silica gel and the printing of receipts. While UV-Vis spectrophotometers are used to measure these phenomena quantitatively, they require additional equipment depending on the type of external stimulus causing the color change. So while, solvatochromism can be measured without additional equipment, measuring thermochromism requires a device to heat the sample. (Application News 01- 00016 describes using a UV-Vis spectrophotometer to measure thermochromism in a solid sample.) Measuring photochromism requires irradiating the sample with light, which can be performed using Shimadzu’s dedicated photoreaction evaluation system called Lightway. More detailed information about Lightway can be found in Application News No. A625. This Application News describes an evaluation of the solvatochromism and thermochromism of a metal complex solution. To measure the thermochromism, a thermoelectrically temperature-controlled cell holder (TCC-100) and a six-cell thermoelectrically temperature-controlled cell positioner (CPS- 100) were used.

23 de enero de 2024 GMT