Correlation diagram (chemistry)

In physical chemistry, a correlation diagram plots the change in orbital energies for a system as a single property of that system varies. Examples include:

• Orgel diagrams, depicting energies of electronic terms in transition metal complexes
• Tanabe–Sugano diagrams, depicting energies of spectroscopic states
• Walsh diagrams, depicting energies as a function of bond angle

Because orbital energies do not cross in isolated systems, correlation diagrams constitute a homotopy, identifying orbitals at one system state with orbitals at another state. Correlation diagrams describing the variation in energies over a reaction coordinate can help rationalize selection rules, such as the Woodward–Hoffmann rules.

• The "Gold Book"
• Oxford Reference
• Albright, T. A.; Burdett, J. K.; Whangbo Myung-Hwan (1985). Orbital Interactions In Chemistry. Wiley. pp. 387–388. ISBN 0-471-87393-4. LCCN 84-15310.
• Review article
• Khushi Ganjir's presentation slides