Optical Electron Transfer Research Articles

Effect of fluorescence color of carbon quantum dots on the optical properties of LaFe0.5Cu0.5O3 nanocomposite and quinoline photocatalytic degradation

The environmentally friendly semiconductor photocatalyst has tremendous potential for resolving wastewater pollution issues. This study describes the successful fabrication of a novel (LaFe0.5Cu0.5O3) LFC0.5/CQDs nanocomposite using a simple cryogenic-calcination method. The LFC0.5/G-CQDs composite displayed the greatest light absorption range and photogenerated carrier separation ability based on their various optical characteristics and electron transfer capabilities. Moreover, its quinoline degradation kinetics were 14 times greater than those of pure LFC0.5. According to the findings of a thorough investigation, this excellent photocatalytic performance may be ascribed to the synergistic effects of the up-converted fluorescent properties of G-CQDs, tuned band structure, and effective charge separation caused by the formation of heterojunction. Based on the findings of the experimental quenching, it was clear that the LFC0.5/G-CQDs photocatalytic process was dominated by the radicals ∙OH and ∙O2−. A potential Z-scheme heterojunction mechanism for quinoline degradation by LFC0.5/G-CQDs was elucidated using band structure analysis and EPR data. In addition, the composite photocatalyst LFC0.5/G-CQDs demonstrated excellent reusability over five cycles. In addition to developing highly efficient visible-light-driven photocatalysts for degrading Quinoline, this study suggests that implementing carbon quantum dots at the center of the main catalyst's luminescence will maximize light utilization and enhance photocatalytic performance.

Rational design of π bridge to forecast photoelectric performance of dye

The conjugate bridge plays an important role in the D–π–A sensitizers, which affects the optical properties, energy levels and electron transfer from donor to acceptor unit. The transfer and securing abilities of conjugate bridge is a necessary conditions to raise the red-shift absorption band, light harvesting ability. In this paper, the effect of conjugate bridge in the D–π–A sensitizers, such as benzene, thiophene, bithiophene, 4-(thiophen-2-yl)benzo[c] [1,2,5]thiadiazole, 4-(thiophen-2-yl)benzo[c] [1,2,5]thiadiazole, terthiophene and so on, which were studied to predict the photoelectric properties of molecules. The ground-state structure and excited-state properties of the dyes and dyes/TiO2 were calculated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The short circuit density (J sc), open-circuit voltage (V oc), fill factor (FF), and photo-to-electric conversion efficiency (η) are critical factors for dye-sensitized solar cells (DSSCs). Then, this method not only considered the relationship between macroscopic phenomena and macroscopic properties but also reasonably selected the dye molecules suitable for dye batteries.

In-situ self-assembly construction of hollow tubular g-C3N4 isotype heterojunction for enhanced visible-light photocatalysis: Experiments and theories

A highly reactive hollow tubular g-C3N4 isotype heterojunction (SCN-CN) was designed to enhance visible light absorption and manipulate the directed transfer of electrons and holes. The results of UV–vis DRS, XPS valence band and DFT theoretical calculations indicated S doping increases the visible-light absorption capacity and changed the ba nd gap structure of g-C3N4 (CN), resulting in the transfer of electrons from the CN to the SCN and holes from the SCN to the CN under visible light. In addition, the tubular structure of the SCN-CN facilitated the transfer of electrons in the longitudinal direction, which reduced charge carrier recombination. Furthermore, the optical properties, electronic structure, and electron transfer of SCN-CN were also studied by experiments and theoretical calculations. The antibiotic tetracycline hydrochloride (TCH) and dye Rhodamine B (RHB) were subjected to evaluate the photocatalytic performance of SCN-CN. The scavenger tests and ESR data showed that the h+, ·O2− and ·OH worked together in the photocatalytic process. Moreover, the photocatalytic degradation pathway was analyzed by LC-MS. This study synthesized a hollow tubular CN isotype heterojunction with high visible-light photocatalytic performance and provided a theoretical basis for CN isotype heterojunction.

Graphene quantum dots wrapped square-plate-like MnO2 nanocomposite as a fluorescent turn-on sensor for glutathione

Benefiting from their excellent optical absorption and electron transfer properties, manganese dioxide nanomaterials have been widely applied for fluorescence-based nanosensors. In this work, graphene quantum dots (GQDs) wrapped square-plate-like MnO2 nanocomposite was synthesized from potassium permanganate via an in situ redox procedure under ultrasonication with poly(allylamine hydrochloride) (PAH) being involved. Through an effective fluorescence resonance energy transfer (FRET) process and inner filter effect (IFE) between GQDs and MnO2, the fluorescence of GQDs was quenched. Furthermore, the introduction of glutathione (GSH) decomposed MnO2 and caused fluorescence recovery of GQDs. Therefore, a MnO2 mediated nanosensor was established for fluorescent turn-on sensing of GSH. A satisfactory linear range was found to be 0.07–70 μM and the detection limit was as low as 48 nM. Besides, the fluorescent recognition of cancer cells using GQDs-MnO2 nanocomposite was achieved because of the obviously higher GSH content in cancer microenvironment than normal cells. This nanosensor was constructed directly in GQDs solution in the presence of PAH without the complicated modifications or connections, making it a facile and novel nanosensor for GSH.

Modification of NFA-Conjugated Bridges with Symmetric Structures for High-Efficiency Non-Fullerene PSCs.

As electron acceptors, non-fullerene molecules can overcome the shortcomings of fullerenes and their derivatives (such as high cost, poor co-solubility, and weak light absorption). The photoelectric properties of two potential non-fullerene polymer solar cells (PSCs) PBDB-T:IF-TN (PB:IF) and PBDB-T:IDT-TN (PB:IDT) are studied by density functional theory (DFT) and time-dependent DFT (TD-DFT). Based on the optimized structure of the ground state, the effects of the electron donor (D) and electron acceptor (A) (D/A) interfaces PBDB-T/IF-TN (PB/IF) and PBDB-T/IDT-TN (PB/IDT) are studied by a quantum-chemical method (QM) and Marcus theory. Firstly, for two non-fullerene acceptors (NFAs) IF-TN and IDT-TN, the NFA IDT-TN has better optical absorption ability and better electron transport ability than IF-TN. Secondly, for the D/A interfaces PB/IF and PB/IDT, they both have high optical absorption and electron transfer abilities, and PB/IDT has better optical absorption and lower exciton binding energy. Finally, some important parameters (open-circuit voltage, voltage loss, fill factor, and power conversion efficiency) are calculated and simulated by establishing the theoretical model. From the above analysis, the results show that the non-fullerene PSC PB:IDT has better photoelectric characteristics than PB:IF.

Intermittent light and microbial action of mixed endogenous source DOM affects degradation of 17β-estradiol day after day in a relatively deep natural anaerobic aqueous environment.

All kinds of wastewaters containing steroid estrogens (SEs) and mixed endogenous source dissolved organic matter (DOM) enter natural water environments with intermittent illumination where microbial action occurs in a relatively deep natural aqueous environment. The role of mixed endogenous source DOM in SEs' biodegradation and photochemical degradation in such environments was studied using 17β-estradiol (E2) in laboratory experiments under anaerobic conditions. The experimental results show that microbial action can improve the optical properties and electron transfer capability of mixed endogenous source DOM, promoting photodegradation and biodegradation. Intermittent illumination attenuates DOM's electron transfer capacity and its chromophore groups, but it improves the bioavailability of low molecular weight dissolved organic matter which promotes microbial growth under anaerobic conditions. DOM-mediated co-degradation by light and microbial action over three days was better than either individually. The presence of Fe(III) promoted electron transfer, and Fe(III)-DOM complexes accelerated energy transfer under irradiation, enhancing photodegradation. Any remaining estrogens will continue to degrade, most effectively in well-aerated waters with sufficient illumination.

P-Carborane Conjugation in Radical Anions of Cage-Cage and Cage-Phenyl Compounds.

Optical electron transfer (intervalence) transitions in radical anions of p-carborane oligomers attest to delocalization of electrons between two p-carboranes cages or a p-carborane and a phenyl ring. Oligomers of the 12 vertex p-carborane (C2B10H12) cage, [12], with up to 3 cages were synthesized, as well as p-carboranes with one or two trimethylsilylphenyl groups, [6], attached to the carbon termini. Pulse radiolysis in tetrahydrofuran produced radical anions, determined redox potentials by equilibria and measured their absorption spectra. Density functional theory computations provided critical insight into the optical electron transfer bands and electron delocalization. One case, [6-12-6], showed both Robin-Day class II and III transitions. The class III transition resulted from a fully delocalized excess electron across both benzene rings and the central p-carborane, with an electronic coupling Hab = 0.46 eV between the cage and either benzene. This unprecedented finding shows that p-carborane bridges are not simply electron withdrawing insulators. In other cases with more than ∼1/2 of the excess electron localized on a [12], large cage distortions were triggered, producing a partially open cage with a nido-like structure. This resulted in class II transitions with similar Hab but massive reorganization energies. The computations also predicted delocalization in radical cations, but complexities in cation formation allowed only tentative experimental support of the predictions. The results with anions provide clear evidence for carborane conjugation that might be exploited in molecular wire materials, which are classically composed of all π-conjugated molecules.

Lattice-matched carbon dots induced the oriented self-assembly of Cu nanoparticles

Orientation-induced crystallization is a widely applied method of forming crystal with highly oriented structure. Here, we reported a promising matrix for orientation-induced crystallization–carbon dots (CDs), who exhibited high lattice-matching with Cu crystal. First, CDs induce self-assembly of Cu nanoparticles through organics-inorganics interface interaction, forming self-assembled mesocrystal and single crystal with large size. Second, the CDs selectively deposit on Cu {111} plane via lattice-matching, endowing Cu self-assemblies with tunable morphology including sphere, truncated octahedron, octahedron, concave octahedron and hexpods. Third, CDs also protect Cu self-assemblies from oxidation and act as efficient interface for optical conversion and electron transfer. So using as surface-enhanced Raman scattering (SERS) substrate for the first time, the CDs-coating hexpods Cu mesocrystal require no post processing and exhibit high stability and surface-enhanced Raman scattering (SERS) activity which ordinary Cu nanostructure cannot achieve.

A study of asymmetrical mixed-valent Mo2-Mo2 complexes in the class III regime.

Three novel asymmetrical dimolybdenum dimers, [Mo2(DAniF)3]2(μ-OOCCOS) (DAniF = N,N'-di(p-anisyl)formamidinate) ([OO-OS]), [Mo2(DAniF)3]2(μ-S2CCO2) ([SS-OO]), and [Mo2(DAniF)3]2(μ-SSCCOS) ([SS-OS]), have been synthesized and characterized by either single-crystal X-ray crystallography or 1H NMR spectroscopy. The structural asymmetry for these compounds gives rise to a redox asymmetry, which enlarges the potential separation (ΔE1/2) between the two [Mo2] units. The mixed-valance (MV) species [OO-OS]+, [SS-OO]+ and [SS-OS]+, prepared by one-electron chemical oxidation of the neutral precursors, exhibit an intense and symmetrical intervalence charge transfer (IVCT) absorption band in the near-IR region, along with the high energy metal (δ) to ligand (π*) (ML) and ligand (π) to metal (δ) charge transfer (LMCT) absorptions. The LMCT band, which is absent in the neutral precursors, is reflective of the cationic [Mo2]+ unit in the MV species; therefore, it is evidenced that in the MV complexes optical electron transfer from the electron donor to acceptor occurs, while the thermal process is energetically unfavorable. The C(1)-C(2) bonds (1.44-1.48 Å) that connect the two [Mo2] units are significantly shorter than a C-C single bond, showing that the two Mo2 centers are strongly coupled. For the series, TD-DFT calculations show that the molecular orbitals have an unsymmetrical charge density distribution over the two dimolybdenum sites. For each of the complex systems, the calculated orbital energy gaps, SOMO(δ - δ)-LUMO(bridging ligand π*), HOMO-8(bridging ligand π)-SOMO(δ - δ) and SOMO(δ - δ)-HOMO-1(δ + δ), are in good agreement with the observed MLCT, LMCT and IVCT absorption band energies, respectively. The consistency in energy between the IVCT band and the SOMO(δ - δ)-HOMO-1(δ + δ) gap permits assignment of the MV complexes to Class III in the Robin-Day scheme.

Molecules on Semiconductors: From Chromogenic Interactions to Information Processing Devices

Rapid development of electronic technologies requires new semiconducting and dielectric materials of superior quality. Recently new applications (like LCD and OLED displays) initiated the employment of various organic materials (pentacene, oligothiophenes) as semiconductors for thin layer field effect transistors. Micro- and nanoelectronics also search for new materials of unusual properties. One of the recent examples is a memristor - a memory resistor. This fourth fundamental passive element (like resistor, capacitor and inductor) was predicted theoretically in early seventies and demonstrated experimentally 37 years later. Memristors have opened new fields of electronics and enabled fabrication of circuits with synaptic properties and learning abilities. Not surprisingly the prototype of this amazing device was based on very popular wide band gap semiconductor: titanium dioxide. This material is widely used as photocatalyst and in dye-sensitized solar cells, but its applications in electronic elements are relatively rare. However, TiO2 is the first material for which the photoelectrochemical photocurrent switching effect was described, which further resulted in new materials for unconventional logic devices. Other metal oxides, especially binary ones (e.g. PbMoO4, BiVO4) exhibit similar semiconducting properties (the same n-type conductivity, similar band gap values), but their properties as active materials in micro/nanoelectronic devices are almost not recognized. The role of these oxide semiconductors may be two-fold. Firstly, they can provide a solid substrate and a scaffold for self-assembly of molecular layers. Transition metal oxides should provide self-assembly template for organic molecules. Secondly, due to their non-innocent interactions with organic ligands may substantially modify properties of organic materials. These interactions may be strong enough to generate new (emergent) optical and electronic features which are not present in parent compounds. Photoinduced electron transfer (PET), optical electron transfer (OET) and photoelectrochemical photocurrent switching effect (PEPS) are such phenomena. This contribution presents the nature of chromogenic interactions from the quantum-chemical point of view on the example of aromatic hydrocarbons anchored to various d 0 ions in the coordination environment present in semiconducting oxide phases. The consequences of these interactions are related to the functional properties which are shown from experimental perspective in the second part. Optoelectronic switches, logic gates, binary computing circuits and artificial synaptic devices will be discussed in detail.

Water Reduction with Visible Light: Synergy between Optical Transitions and Electron Transfer in Au‐TiO2 Catalysts Visualized by In situ EPR Spectroscopy

Golden electrons: Visible light excites conduction electron transfer from gold particles to support vacancies where they are taken up by protons to produce hydrogen. This transfer process was visualized by in situ EPR spectroscopy.

Proton-Coupled Electron Transfer in Ferrocenium–Phenolate Radicals

Electron and proton transfer (ET, PT) can be intimately coupled, provided suitable redox and acid/base sites are available. The amide-linked ferrocene–phenol H-1 is deprotonated to the phenolate [1]– by phosphazene bases and oxidized to the ferrocenium ion [H-1]+ by silver hexafluoroantimonate. Concomitant oxidation and deprotonation yields the radical [1]•, featuring a characteristic near-IR absorption band. The ground state of [1]• is best described as the ferrocenium–phenolate zwitterion [1b]• with a dynamic dissymmetric N···H···O hydrogen bond (PT). The ferrocenium–iminolate N···H–O tautomer [1b]•-NHO′ can undergo a thermal structural rearrangement to the high-energy OH···O tautomer [1b]•-OHO, while the amide–phenolate N–H···O tautomer [1b]•-NHO is poised to optical electron transfer to yield the ferrocene–phenoxyl valence isomer [1a]•-NHO (Eop = 1.18–1.19 eV).

An analysis of the optimal band gaps of light absorbers in integrated tandem photoelectrochemical water-splitting systems

The solar-to-hydrogen (STH) efficiency limits, along with the maximum efficiency values and the corresponding optimal band gap combinations, have been evaluated for various combinations of light absorbers arranged in a tandem configuration in realistic, operational water-splitting prototypes. To perform the evaluation, a current–voltage model was employed, with the light absorbers, electrocatalysts, solution electrolyte, and membranes coupled in series, and with the directions of optical absorption, carrier transport, electron transfer and ionic transport in parallel. The current density vs. voltage characteristics of the light absorbers were determined by detailed-balance calculations that accounted for the Shockley–Queisser limit on the photovoltage of each absorber. The maximum STH efficiency for an integrated photoelectrochemical system was found to be ∼31.1% at 1 Sun (=1 kW m−2, air mass 1.5), fundamentally limited by a matching photocurrent density of 25.3 mA cm−2 produced by the light absorbers. Choices of electrocatalysts, as well as the fill factors of the light absorbers and the Ohmic resistance of the solution electrolyte also play key roles in determining the maximum STH efficiency and the corresponding optimal tandem band gap combination. Pairing 1.6–1.8 eV band gap semiconductors with Si in a tandem structure produces promising light absorbers for water splitting, with theoretical STH efficiency limits of >25%.

Synthesis and characterization of redox-active charge-transfer complexes with 2,3,5,6-tetracyanopyridine (TCNPy) for the photogeneration of pyridinium radicals.

The heteroaromatic polynitrile compound tetracyanopyridine (TCNPy) is introduced as a new electron acceptor for the formation of deeply colored charge-transfer complexes. In MeCN, TCNPy is characterized by a quasireversible one-electron-reduction process at −0.51 V (versus SCE). The tetracyanopyridine radical anion undergoes a secondary chemical reaction, which is assigned to a protonation step. TCNPy has been demonstrated to generate 1:1 complexes with various electron donors, including tetrathiafulvalene (TTF) and dihydroxybenzene derivatives, such as p-hydroquinone and catechol. Visible- or NIR-light-induced excitation of the intense charge-transfer bands of these compounds leads to a direct optical electron-transfer process for the formation of the corresponding radical-ion pairs. The presence of available electron donors that contain protic groups in close proximity to the TCNPy acceptor site opens up a new strategy for the photocontrolled generation of pyridinium radicals in a stepwise proton-coupled electron-transfer (PCET) sequence.

Energy Alignment, Molecular Packing, and Electronic Pathways: Zinc(II) Tetraphenylporphyrin Derivatives Adsorbed on TiO2(110) and ZnO(11–20) Surfaces

The relation between energy alignment, adsorption geometry, and electron transfer between a chromophore and an oxide surface has been explored for a series of Zn(II) tetraphenylporphyrin derivatives adsorbed on TiO2(110) and ZnO(112̅0) surfaces. The electronic occupied and unoccupied structure has been obtained using UV-photoemission and inverse photoemission spectroscopies. From these results, a full picture of the energetics at the chromophore–oxide interface was established. The alignment of the molecular levels relevant for optical transition was found independent of the functionalization of the meso-phenyl groups. However, to explain the observation of different optical properties and electron transfer efficiencies of these different dyes, the adsorption geometry of two of these dyes was determined using scanning tunnel microscopy and near edge absorption fine structure spectroscopy. Functionalization of the meso-phenyls with COOH groups in the meta-position results in the ZnP macrocycle adsorbed parallel to the surface. Functionalization of the meso-phenyl groups with COOH groups in the para position results in a bounding geometry where the ZnP macrocycle makes an angle of ∼50° from the surface normal. This geometry, which allows face-to-face stacking of the porphyrin rings, opens a new electronic channel for exciton delocalization that competes with direct electron injection into the substrate conduction band.

Theoretical Study of N749 Dyes Anchoring on the (TiO2)28 Surface in DSSCs and Their Electronic Absorption Properties

We have performed calculations on the panchromatic N749 dyes adsorbed on the (TiO2)28 surface. N749 is a prototypical form of Ru(II) complexes for dye sensitized solar cells (DSSCs), which possesses a terpyridine tridentate ligand bearing four different protonation states (0, 1, 2, or 3 carboxylic protons). Depending on the type of proton bonding interaction (protonated and deprotonated), seven N749/(TiO2)28 surface models (N749-0H/(TiO2)28, N749-1H-P/(TiO2)28, N749-1H-DP/(TiO2)28, N749-2H-P/(TiO2)28, N749-2H-DP/(TiO2)28, N749-3H-P/(TiO2)28, and N749-3H-DP/(TiO2)28) have been applied in this study for the geometry optimization, frontier molecular orbital level diagrams, and calculated absorption spectra. The moderate surface area of the (TiO2)28 cluster is suitable for N749 dyes adsorbing behaviors so that all calculations can be performed using the Gaussian 09 program package. We have carefully examined these seven N749/(TiO2)28 assemblies that could influence the DSSC device performance. The calculated absorption spectra of these seven various N749/(TiO2)28 models are in good agreement with the experimental results by Hagfeldt et al. (J. Phys. Chem. B2002, 106, 12693–12704) with onset ranging from the visible to near-IR region. The combination of the adsorption energy onto TiO2 and calculated absorption spectra (cf. the experimental results) concludes that the deprotonated dyes constitute the most favorable and dominant structure in the DSSC devices. The frontier molecular orbital graphs indicate that the electron charge distributions of all HOMOs are located at the N749 dyes, while LUMOs are localized at the (TiO2)28 surface or delocalized at the interfacial regions of N749/(TiO2)28. The corresponding transitions are thus more like a type of optical electron transfer, injecting the electron to the interfacial TiO2.

Visible‐Light‐Induced Sulfoxidation of Alkanes in the Presence of Titania

AbstractThe first catalytic photosulfoxidation of alkanes is accomplished in the presence of titanium dioxide and visible light (λ≥400 nm) under an atmosphere of SO2/O2. For n‐heptane and cyclohexane the reaction is performed in the neat liquid, for adamantane in glacial acetic acid. Charge‐transfer (CT) complexation of sulfur dioxide by the titania surface generates a CT band at 400–420 nm responsible for the visible‐light activity of otherwise only UV light absorbing titania. The primary charges generated upon optical electron transfer produce alkyl radicals by dissociative electron transfer from the alkane and by hydrogen abstraction by OH radicals produced from oxygen reduction. Once formed, the alkyl radicals initiate a radical chain reaction as known from the classical UV‐induced sulfoxidation in the absence of a catalyst. The reaction exhibits features characteristic for product inhibition by strong adsorption. Accordingly, the initial photocatalytic activity is fully restored after washing the catalyst with methanol. Time‐resolved photovoltage measurements indicate that photocatalyst deactivation is connected with a change from n‐type to p‐type titanium dioxide. Small amounts of water and radical scavengers inhibit product formation. The reaction proceeds with high chemoselectivity because only traces of expected by‐products like sulfates, ketones, and alcohols are formed. Thus, in addition to its basic role in visible‐light‐induced charge generation, the surface of titania enables also a chemoselective CS bond formation.

Experimental Exploration of the Mulliken−Hush Relationship for Intramolecular Electron Transfer Reactions

The Mulliken-Hush (M-H) relationship provides the critical link between optical and thermal electron transfer processes, and yet very little direct experimental support for its applicability has been provided. Dicyanovinylazaadamantane (DCVA) represents a simple two-state (neutral/charge-transfer) intramolecular electron transfer system that exhibits charge-transfer absorption and emission spectra that are readily measurable in solvents with a wide range of polarities. In this regard it represents an ideal model system for studying the factors that control both optical charge separation (absorption) and recombination (emission) processes in solution. Here we explore the applicability of the M-H relation to quantitative descriptions of the optical charge-transfer processes in DCVA. For DCVA, the measured radiative rate constants exhibit a linear dependence on transition energy, and transition dipole moments exhibit an inverse dependence on transition energy, consistent with the M-H relationship.

Optical electron transfer through 2,7-diethynylfluorene spacers in mixed-valent complexes containing electron-rich “(η2-dppe)(η5-C5Me5)Fe” endgroups

We report in this communication the study of the intramolecular electron transfer through a 2,7-diethynylfluorenyl spacer in the Fe(II)/Fe(III) mixed-valent (MV) complex [(η(2)-dppe)(η(5)-C(5)Me(5))FeC≡C(2,7-C(21)H(24))C≡CFe(η(5)-C(5)Me(5))(η(2)-dppe)][PF(6)] (1[PF(6)]). The complex is generated in situ by comproportionation from its homovalent dinuclear Fe(II) and Fe(III) parents (1 and 1[PF(6)](2)). It is shown that electronic delocalization is much more effective through a 2,7-fluorenyl than through a 4,4'-biphenyl bridging unit.

Redox-responsive organometallic foldamers from ferrocene amino acid: Solid-phase synthesis, secondary structure and mixed-valence properties

Oligoferrocenes Fmoc-Fca(n)-OMe (n=3-5) are assembled in a stepwise precise manner from Fmoc-protected ferrocene amino acid Fmoc-Fca-OH (H-Fca-OH = 1-amino-1'-ferrocene carboxylic acid; Fmoc = 9-fluorenylmethyloxycarbonyl) via amide bonds on solid supports by sequential Fmoc deprotection, acid activation and coupling steps. The resulting well-defined oligomers form ordered zigzag structures in THF solution with characteristic hydrogen bonding patterns. Electrochemical experiments reveal sequential oxidations of the individual ferrocene units in these peptides giving mixed-valent cations. Optical intervalence electron transfer is detected by intervalence transitions in the near-IR.