Naslov
CALCULATION OF REDOX POTENTIAL IN FERROCENE DERIVATIVES. WHY HYBRID DFT METHODS FAIL?

Autori
Toma, Mateja ; Kuvek, Tea ; Djaković, Senka ; Lapić, Jasmina ; Šakić, Davor ; Vrček, Valerije

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
European Symposium on Organic Reactivity / Vančik, Hrvoj ; Namjesnik, Danijel - Zagreb : Hrvatsko kemijsko društvo, 2019, 90-90

ISBN
9789535523291

Skup
17th European Symposium on Organic Reactivity (ESOR 2019)

Mjesto i datum
Dubrovnik, Hrvatska, 08.09.2019. - 13.09.2019

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
redox potential, ferrocene, DFT

Sažetak
A number of studies and library syntheses have been focused on the modulation of the ferrocene (FcH) reduction potential by changing substituents and linkers at the ferrocene core. The tuning of ferrocene redox potential can be assisted and supported by quantum chemical calculations. Different computational methodologies have appeared with the density functional theory (DFT) as the most promising platform for predictions of redox potential in ferrocene derivatives. We applied the selected benchmark method (SMD-B3LYP/6-31G(d)/LanL2TZf level of theory) for series of ferrocenyl derivatives (FcR, where R is Me, F, Br, COOH, OCOMe, CN…) and excellent agreement between calculated and experimental redox potential was obtained. However, for some cases (e.g. R is N3, Cl, NH2…) a significant discrepancy between experimental and calculated data was observed. The error (absolute difference from the experimental value) amounts to 1000 mV, which may be converted (by relation E° = –ΔGr/nF) to the Gibbs free energy equivalent of ca. 100 kJ/mol. This is an unacceptable deviation produced by the benchmarked DFT method. Three variables were assessed to detect a possible origin of the observed failure: functional, basis set, and solvation model. It comes out that the Hartree-Fock exchange fraction (χ) in hybrid DFT methods (e.g. PBE0, BHandH, M06…) is the main source of the error. The higher percentage of exact exchange, the larger is error for calculated redox potential of selected ferrocenes. Most of hybrid DFT methods overestimate the stability of oxidized ferrocene species. Therefore, the calculated value of redox potential for specific FcR(1+/0) couples is too low, and the ferrocene derivative appears as an extremely strong reducing agent.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Farmacija

POVEZANOST RADA