Comparison of DFT methods used in calculation of eledtrochemical parameters of ferrocene derivatives

Ferocen i njegovi derivati posjeduju korisna fizikalno-kemijska svojstva (npr. obojanost, termička stabilnost, jedno-elektronska redukcija), te se primjenjuju u znanosti o materijalima, a njihova primjena u biomedicini intenzivno se istražuje u posljednjim desetljećima. Znajući da su elektrokemijska svojstva ferocenskih derivata u korelaciji s njihovom biološkom aktivnosti, proučavanje ovih svojstava od iznimne je važnosti. Primjena računalne kemije u predviđanju elektrokemijskih svojstava ferocenskih derivata može usmjeriti složene eksperimentalne procedure, te ubrzati pronalazak odgovarajućeg derivata. Za izračun ferocenskih derivata često su korištene računalne metode koje se koriste teorijom funkcionala gustoće (DFT). U ovom se radu proučava uspješnost predviđanja elektrokemijskog potencijala korištenjem pojedinih DFT funkcionala i ispituje utjecaj Hartree-Fock (HF) izmjene u različitim funkcionalima usporedbom s literaturnim eksperimentalnim redoks potencijalima za 16 ferocenskih derivata određenih u tetrahidrofuranu kao otapalu. Becke funkcionali bez HF izmjene (B-LYP 0%) daju lošije procjene od funkcionala s većim udjelom HF izmjene (B3-LYP 25% i B-HandH-LYP 50%), ali za razliku od B3-LYP i B-HandH-LYP kod B-LYP nema velikih odstupanja (> 200 mV) kod određenih spojeva. Minnesotta funkcionali (M06-L, M06 i M06-2X) pokazuju sličan trend, pri čemu M06 i M06-2X imaju odličnu korelaciju, ali i nemogućnost izračuna nekih ferocenskih derivata.Ferrocene and its derivatives have useful physical and chemical properties (e.g. coloration, thermal stability, one-electron reduction) and are used in material science. Biomedical application of ferrocene derivatives has been investigated intensively over the past decades. Correlation of ferrocene derivatives electrochemical properties with their respective biological activity, became a strong reason to study those properties. Use of computational chemistry for the prediction of electrochemical properties of ferrocene derivatives can steer complex experimental procedures and accelerate the discovery of derivatives with desired properties. Computational methods employing Density Functional Theory (DFT) are often used in the calculation of ferrocene derivatives. In this work, the efficacy of the prediction of electrochemical potential using different DFT functionals is studied. Moreover, the influence of Hartree-Fock (HF) exchange in different functionals is examined. This is achieved by comparing literature experimental data of redox potentials for 16 ferrocene derivatives, whose potentials were obtained in tetrahydrofuran, with calculated potentials. Becke functionals that don’t contain HF exchange (B-LYP 0%) allow poorer estimates than functionals with a higher proportion of HF exchange (B3-LYP 25% and B-HandH-LYP 50%). The advantage is that B-LYP, unlike B3-LYP and B-HandH-LYP, doesn’t show large deviations (>200 mV) for certain compounds. Minnesotta functionals (M06-L, M06 and M06-2X) follow a similar trend, whereby M06 and M06-2X have a high correlation, but at the same time, for some of ferrocene derivatives calculations fail at those levels of theory