Term: Weller correlation
https://doi.org/10.1351/goldbook.W06671

Definition:
Empirical correlation for the energy of full charge-transfer exciplex relative to the ground state in n-hexane as a function of the electrochemical one electron standard reduction potential of the cation radical produced upon electron donation and standard reduction potential of the acceptor measured in a polar solvent for the donor (D) and the acceptor (A) involved \[\Delta H(\text{D}^{+}\text{A}^{-},\text{hexane}) = e\left [ E^{0}(\text{D}^{+\bullet }/\text{D}) - E^{0}(\text{A}/\text{A}^{-\bullet }) \right ]+e\Delta E\] with E0(D+•/D) and E0(A/A-•) the standard electrode potentials of the donor and acceptor, respectively.

Notes:
0) In the case diethylaniline as donor and aromatic @H02889@ as acceptors, the last term on the right, i.e., eΔE = 0.15 ± 0.10 eV. This equation assumes a constant @C01365@ term and a constant @E02149@ change within a particular series of partners. e is the @E02032@.
1) The IUPAC recommendations for the sign and symbols of standard potentials are used in the equation as written above.
2) Although not complying with the IUPAC recommended nomenclature for the standard electrode potentials, traditionally the equation has been written as: \[\Delta H(\text{D}^{+}\text{A}^{-},\text{hexane}) = e\left [ E_{\text{ox}}^{0} - E_{\text{red}}^{0} \right ]+(0.15 \pm 0.10)\ \text{eV}\] with E(0)ox the @S05912@ at which the @O04362@ occurs, and E(0)red the @S05912@ at which the reduction occurs. This writing of the first term within the square brackets is misleading and not recommended.

Related Terms:
1) hydrocarbons (http://doi.org/10.1351/goldbook.H02889).
2) coulomb (http://doi.org/10.1351/goldbook.C01365).
3) entropy (http://doi.org/10.1351/goldbook.E02149).
4) elementary charge (http://doi.org/10.1351/goldbook.E02032).
5) standard electrode potential (http://doi.org/10.1351/goldbook.S05912).
6) oxidation (http://doi.org/10.1351/goldbook.O04362).
7) exciplex (http://doi.org/10.1351/goldbook.E02246).
8) ground state (http://doi.org/10.1351/goldbook.G02704).
9) cation radical (http://doi.org/10.1351/goldbook.R05073).
10) polar solvent (http://doi.org/10.1351/goldbook.P04717).

Source: PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 439 (https://doi.org/10.1351/pac200779030293)

Citation: 'Weller correlation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.W06671

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