A series of di- and triferrocenyl (hetero)aromatics including 2,5-diferrocenylpyridine (4), 2,6-diferrocenylpyridine (5), 1,3,5-triferrocenylbenzene (9), 2,4,6-triferrocenylpyridine (10), and 2,4,6-triferrocenyl-1,3,5-triazine (11) have been prepared using the Negishi C,C cross-coupling protocol. Characterization of the molecules was performed by spectroscopic means and single-crystal X-ray diffraction study (10). The electrochemical properties of these compounds were determined by cyclic voltammetry, square wave voltammetry, and in situ NIR spectroelectrochemistry. The cyclic voltammograms show well-defined, separated, and reversible one-electron processes for each ferrocenyl moiety with ΔE°′ values (= separation between two formal potentials) ranging from 140 to 185 mV. The UV–vis/NIR spectra of the partially oxidized mixed-valent complexes of 4, 5, 9, and 10 show weak intervalence charge transfer absorptions, while only electrostatic interactions exist between the different oxidized iron centers of 11. Supporting DFT calculations were carried out to establish a basic understanding of the electronic structure.

The Fermi-Löwdin orbital self-interaction correction (FLO-SIC) methodology is applied to atoms and molecules from the standard G2-1 test set. For the first time FLO-SIC results for the GGA-type PBE functional are presented. In addition, examples where FLO-SIC like any proper SIC provides qualitative improvements compared to standard DFT functionals are discussed in detail: the dissociation limit for H + 2 , the step-wise linearity behavior for fractional occupation, as well as the significant reduction of the error of static polarizabilities. Further, ionization potentials and enthalpies of formation obtained by means of the FLO-SIC DFT method are compared to other SIC variants and experimental values. The self-interaction correction gives significant improvements if used with the LDA functional but shows worse performance in case of enthalpies of formation if the PBE-GGA functional is used. The errors are analyzed and the importance of the overbinding of hydrogen is discussed.

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The correction of the self-interaction error (SIE) that is inherent to all standard density functional theory (DFT) calculations is an object of increasing interest. In this article we apply the very recently developed Fermi-orbital based approach for the self-interaction correction (FOSIC) [1,2] to a set of different molecular systems. Our study covers systems ranging from simple diatomic to large organic molecules. We focus our analysis on the direct estimation of the ionization potential from orbital eigenvalues.

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