Orgel diagrams are
correlation diagrams which show the relative energies of
electronic terms in
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
complexes, much like
Tanabe–Sugano diagram
In coordination chemistry, Tanabe–Sugano diagrams are used to predict absorptions in the ultraviolet (UV), visible and infrared (IR) electromagnetic spectrum of coordination compounds. The results from a Tanabe–Sugano diagram analysis of a ...
s. They are named after their creator,
Leslie Orgel. Orgel diagrams are restricted to only show weak field (i.e.
high spin Spin states when describing transition metal coordination complexes refers to the potential spin configurations of the central metal's d electrons. For several oxidation states, metals can adopt high-spin and low-spin configurations. The ambiguity o ...
) cases, and offer no information about strong field (low spin) cases. Because Orgel diagrams are
qualitative
Qualitative descriptions or distinctions are based on some quality or characteristic rather than on some quantity or measured value.
Qualitative may also refer to:
*Qualitative property, a property that can be observed but not measured numericall ...
, no energy calculations can be performed from these diagrams; also, Orgel diagrams only show the symmetry states of the highest
spin multiplicity instead of all possible terms, unlike a Tanabe–Sugano diagram.
[Housecroft, C. E.; Sharpe, A. G. (2008). Inorganic Chemistry (3rd ed.). Prentice Hall. .] Orgel diagrams will, however, show the number of spin allowed transitions, along with their respective symmetry designations. In an Orgel diagram, the parent term (P, D, or F) in the presence of no ligand field is located in the center of the diagram, with the terms due to that electronic configuration in a ligand field at each side. There are two Orgel diagrams, one for d
1, d
4, d
6, and d
9 configurations and the other with d
2, d
3, d
7, and d
8 configurations.
In an Orgel diagram, lines with the same Russell–Saunders terms will diverge due to the
non-crossing rule, but all other lines will be linear. Also, for the D Orgel diagram, the left side contains d
1 and d
6 tetrahedral and d
4 and d
9 octahedral complexes. The right side contains d
4 and d
9 tetrahedral and d
1 and d
6 octahedral complexes. For the F Orgel diagram, the left side contains d
2 and d
7 tetrahedral and d
3 and d
8 octahedral complexes. The right side contains d
3 and d
8 tetrahedral and d
2 and high spin d
7 octahedral complexes.
References
External links
Applying Electronic SpectraCalculations Using Tanabe-Sugano Diagrams
Coordination chemistry
Spectroscopy
Inorganic chemistry
Transition metals
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