What is the Difference Between Bathochromic Shift and Hypsochromic Shift?

The main difference between bathochromic shift and hypsochromic shift lies in the change in the wavelength of the absorption peak in a spectroscopic analysis.

• Bathochromic shift: This is a change in the absorption peak to a longer wavelength (lower energy), also known as a red shift. It occurs when the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) decreases, making the transition more possible. Factors that can cause bathochromic shifts include solvatochromism (the effect of solvent on the λmax) and structural changes, such as the addition of extra double bonds to a molecule.
• Hypsochromic shift: This is a change in the absorption peak to a shorter wavelength (higher energy), also known as a blue shift. It occurs when the energy gap between the HOMO and LUMO increases, making the transition less possible. Factors that can cause hypsochromic shifts include negative solvatochromism (a change in solvent polarity) and the presence of substituent groups that decrease the absorption of chromophores.

In summary, the key difference between bathochromic shift and hypsochromic shift is that bathochromic shift involves a change in the absorption peak to a longer wavelength (red shift), while hypsochromic shift involves a change in the absorption peak to a shorter wavelength (blue shift).

Comparative Table: Bathochromic Shift vs Hypsochromic Shift

The main difference between bathochromic shift and hypsochromic shift is the direction of the shift in the wavelength of the absorption peak. Here is a table summarizing the differences:

Bathochromic shift is responsible for the red shift, while hypsochromic shift is responsible for the blue shift. These shifts can be observed in various spectroscopic techniques, such as UV-visible spectroscopy.