Theoretical study of electrical and electrochemical properties of cyclopentanepentaone and its dicyanomethylene derivatives

Theoretical studies on anions of 1,2‐dihydroxycyclopentenetrione (croconic acid, H₂C₅O₅) and the whole series of dicyanomethylene derivatives in gas phase and in dimethyl formamide (DMF) solution are carried out using density functional theory (DFT) and self‐consistent reaction field (SCRF)‐DFT method at the B3LYP theory level for the first time. Natural bond orbital (NBO) analyses indicate that π‐electron delocalization in the series is quite strong. Based on the most stable conformations, linear correlations are observed between the oxidation potential measured by cyclic voltammetry and the highest occupied molecular orbital (HOMO) energy as well as ionization potential (Ip), which supports experimental results that systematic substitution of the oxygen atoms in the C₅O structure with C(CN)₂ groups causes a shift of both the oxidation potentials E and E toward more positive values. The correlations are also observed between experimental diffusion coefficient D and E_bind calculated in gas phase and DMF solution, the experimental electrochemical reducing potentials (E_R) and the electron affinity (Ea). © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007