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In recent years, application of calculated density functional theory Kohn–Sham (DFT-KS) orbitals and eigenvalues have gained increased popularity due to their ability to display and predict physico-chemical properties of large systems. Our interest in this area has been to employ the exchange-correlation hybrid functional B3LYP with a small 3-21G (*) basis to determine the geometry of large donor–acceptor assemblies followed by comparison of the computed KS orbital energies with measured electrochemical and spectral properties. The surprisingly localized orbitals allow prediction of the site of electron transfer during electrochemical oxidation and reduction of covalently bonded or self assembled porphyrin–fullerene donor–acceptor systems. The highest occupied orbitals (HOMOs) track oxidation potentials while the lowest unoccupied orbitals (LUMOs) track the reduction potentials of these compounds. Such studies are important to determine the position of energy levels of these donor–acceptor systems for understanding the pathways of photo initiated electron or energy transfer processes. The geometry and association energy of supramolecular assemblies (including loosely bound complexes self-assembled by H-bonding, electrostatics, or by π–π porphyrin–fullerene interactions) are also well represented, but the association energy must be scaled to agree with experimental values. The unusual success of the B3LYP/3-21G (*) method may be attributable, in part, to fortuitous shadowing of the interaction energy by significant basis set superposition effects. Results of several molecular and supramolecular systems at this computational level, comprised of porphyrin–fullerene donor–acceptor entities, developed in our laboratory, are reviewed. To cite this article: M.E. Zandler, F. D'Souza, C. R. Chimie 9 (2006) .

Supramolecular triads composed of fullerene (C60) as primary electron acceptor, zinc porphyrin (ZnP) as primary electron donor, and either a ferrocene (Fc), or N,N-dimethylaminophenyl (DMA), or N,N-diphenylaminophenyl (DPA) entity as a second electron donor were constructed via a ‘two-point’ binding motif involving axial coordination and hydrogen bonding. The B3LYP/3-21G(*) optimized structures revealed disposition of the three entities of the triads in a triangular fashion. The redox behavior of the different components was studied using cyclic voltammetry in o-dichlorobenzene containing 0.1 M (n-C4H9)4NClO4. The oxidation potentials of the second electron donor followed the trend: Fc

A one-step synthesis of bis-pyrrolidine functionalized fullerene-dibenzo[18]crown-6 conjugate and its metal cation complexation to the crown ether entity dependent redox behavior is reported.

Synthesis and physicochemical characterization of a series of molecular triads composed of ferrocene, C60, and nitroaromatic entities are reported. Electrochemical studies revealed multiple redox processes involving all three redox active ferrocene, C60, and nitrobenzene entities. Up to eight redox couples within the accessible potential window of o-dichlorobenzene containing 0.1 M (TBA)ClO4 are observed. A comparison between the measured redox potentials with those of the starting compounds revealed absence of any significant electronic interactions between the different redox entities. The geometric and electronic structure of the triads are elucidated by using ab initio B3LYP/3-21G(*) methods. In the energy-optimized structures, as predicted by electrochemical studies, the first HOMO orbitals are found to be located on the ferrocene entity, while the first LUMO orbitals are mainly on the C60 entity. The coefficients of the subsequent LUMO orbitals track the observed site of electrochemical reductions o...