Charge Transfer Properties in Cyclopenta[l]phenanthrene Ferrocenyl Complexes

Abstract

The new complexes (2-ferrocenyl)cyclopenta[l]-phenanthrene and (2-ferrocenyl)(eta(5)-cyclopenta[l]phenanthrenyl)FeCp have been prepared and the charge transfer properties of their monocationic derivatives investigated. The cations were generated by chemical oxidation using ferrocenium(BF4) or acetylferrocenium(BF4) as the oxidative agent and monitored in the visible, IR, and near-IR regions. The electrochemistry of the two complexes and, for comparison, of the previously reported (eta(5)-cyclopenta[l]phenanthrenyl)FeCp was analyzed. The charge transfer bands in the near-IR spectral region of the monocations are rationalized in the framework of Marcus-Hush theory. In particular, the monometallic (2-ferrocenyl)cyclopenta[l]phenanthrene displays a single oxidation wave at a potential very close to that of (eta(5)-cyclopenta[l]phenanthrenyl)FeCp and its monocations exhibits a ligand-to-metal charge transfer band in the visnear-IR region. The unsymmetrical diiron species (2-ferrocenyl)(eta(5)-cyclopenta[l]phenanthrenyl)FeCp undergoes two consecutive and well-resolved one-electron oxidations producing, at the first oxidation step, a mixed-valence monocation which displays an intervalence charge transfer band in the vis-near-IR region

Tuning Electron-Transfer Properties in 5,10,15,20-Tetra(1′-hexanoylferrocenyl)porphyrins as Prospective Systems for Quantum Cellular Automata and Platforms for Four-Bit Information Storage

“…The electrochemical comproportionation constants ( K c ) for the mixed-valence porphyrins [ 1 ] n + and [ 2 ] n + ( n = 1 or 2) can be calculated based on the following equilibrium eqs (Table ): …”

“…Calculated on the basis of the CV and DPV data, comproportionation constants for the formation of mixed-valence [ 1 or 2 ] + (343 and 824 000, respectively) and [ 1 or 2 ] 2+ (1 216 000 and 174 000, respectively) are quite high and indicative of the stability of these species under electrochemical and spectroelectrochemical conditions. It is well-recognized, however, that the electrochemical comproportionation constants should be treated with caution, as they will heavily depend on the solvent/electrolyte combination . Another complication in interpretation of the electrochemical results can come from the Columbic repulsion between ferrocene fragment in [ 1 or 2 ] n + species, as it clearly might affect stability of the different atropisomers in solution.…”

Unusual Low-Energy Near-Infrared Bands for Ferrocenyl–Naphthalimide Donor–Acceptor Dyads with Aromatic Spacer Groups: Prediction by Time-Dependent DFT and Observation by OTTLE Spectroscopy

“…While the calculated oscillator strengths of these transitions are undoubtedly very small, a value of 0.0000 in the Gaussian output file indicates an oscillator strength that is less than 0.0001, rather than a value that is strictly 0. The NIR region of the electronic spectrum is often overlooked, but medium to strong absorptions are not uncommon and are often associated with ligand metal charge transfer (LMCT), and particularly intervalence charge transfer (IVCT) in bi- and multimetallic complexes. ,− Weak bands in the NIR for ferrocenyl systems (ε = 50–200 L mol –1 cm –1 ) have also been directly observed or inferred from Gaussian deconvolution, particularly in contributions from the Lang research group. ,− These weak bands have not been comprehensively characterized but are generally thought to be due to forbidden interconfigurational (IC) transitions (dπ–dπ). Similar transitions are also observed in other group 8 metal and piano stool complexes. − To our knowledge TDDFT has not been used to predict these transitions before.…”

“…In these and similar simple D–A systems, oxidation of the ferrocenyl substituents results in significant changes to the electronic absorption bands, which are conveniently observed using spectroelectrochemical techniques. Generally a bleaching of any ferrocene-based charge-transfer (CT) features occurs and a new weak band with LMCT character appears in the near-IR (NIR), the acceptor reversing its role and acting as donor to the electron-poorer ferrocenium. − …”

Charge Transfer Properties of Benzo[b]thiophene Ferrocenyl Complexes

“…The classical electron transfer Hush model, developed for the interpretation of the intervalence charge transfer (IVCT) bands of bimetallic and organic molecules, has been also extended to the LMCT processes to get insight into the delocalization in monometallic metal-based conjugates. However, only in a few cases ,,,, have the results been interpreted in the framework of the classical two-state Hush theory.…”