Evaporative Cooling Does Not Prevent Vertical Dispersion of Effervescent Seawater Aerosol for Brightening Clouds.

Marine cloud brightening (MCB) is a potential intervention to mitigate the effects of climate change by increasing the reflectance of low-level maritime clouds, including those over the Great Barrier Reef. The technique involves dispersing a plume of submicrometer seawater droplets over the ocean, which evaporate, generating nanosized sea-salt aerosols (SSAs) that disperse through the atmosphere with some fraction incorporated into clouds. Droplet evaporation, which occurs in the immediate vicinity (meters to tens of meters) of the source, has been theorized to produce a negatively buoyant plume hindering the mixing of the sea-salt aerosol to cloud height and compromising the effectiveness of MCB. We characterized in situ for the first time the nearfield aerosol dispersion from a point source of atomized seawater produced using the effervescent technique. We observed consistent vertical mixing of the plume up to 150 ± 5 m height at 1 km downwind. The extent of vertical dispersion was influenced by wind velocity and atmospheric stability. We found no evidence that negative buoyancy due to the evaporation of the 0.068 kg/s water fraction significantly suppressed vertical mixing. Our results can be attributed to the small droplet sizes generated by the effervescent spray technology and associated low flow rates required to generate around 1014 droplets s-1. We estimate that, for a hypothetical implementation producing up to 1016 s-1 similarly sized SSAs, evaporative cooling is unlikely to significantly suppress the vertical dispersion of aerosol for MCB.

Sterically attenuated electronic communication in cobalt complexes of meridional isoquinoline-derived ligands for applications in electrocatalysis.

The ability to synthetically tune the ligand frameworks of redox-active molecules is of critical importance to the economy of solar fuels because manipulating their redox properties can afford control over the operating potentials of sustained electrocatalytic or photoelectrocatalytic processes. The electronic and steric properties of 2,2':6',2″-terpyridine (Terpy) ligand frameworks can be tuned by functional group substitution on ligand backbones, and these correlate strongly to their Hammett parameters. The synthesis of a new series of tridentate meridional ligands of 2,4,6-trisubstituted pyridines that engineers the ability to finely tune the redox potentials of cobalt complexes to more positive potentials than that of their Terpy analogs is achieved by aryl-functionalizing at the four-position and by including isoquinoline at the two- and six-positions of pyridine (Aryl-DiQ). Their cobalt complex syntheses, their electronic properties, and their catalytic activity for carbon dioxide (CO2) reduction are reported and compared to their Terpy analogs. The cobalt derivatives generally experience a positive shift in their redox features relative to the Terpy-based analogs, covering a complementary potential range. Although those evaluated fail to produce any quantifiable products for the reduction of CO2 and suffer from long-term instability, these results suggest possible alternate strategies for stabilizing these compounds during catalysis. We speculate that lower equilibrium association constants to the cobalt center are intrinsic to these ligands, which originate from a steric interaction between protons on the pyridine and isoquinoline moieties. Nevertheless, the new Aryl-DiQ ligand framework has been engineered to selectively tune homoleptic cobalt complexes' redox potentials.

Quantum Interference in Mixed-Valence Complexes: Tuning Electronic Coupling Through Substituent Effects.

Whilst 2- or 5-OMe groups on the bridging phenylene ring in [{Cp*(dppe)RuC≡C}2 (µ-1,3-C6 H4 )]+ have little influence on the electronic structure of this weakly coupled mixed-valence complex, a 4-OMe substituent enhances ground state electron delocalization, and increases the intensity of the IVCT transition. Vibrational frequency and TDDFT calculations (LH20t-D3(BJ), def2-SVP, COSMO (CH2 Cl2 )) on ([{Cp*(dppe)RuC≡C}2 (µ-1,3-C6 H3 -n-OMe)]+ (n=2, 4, 5) models are in excellent agreement with the experimental results. The stronger ground state coupling is attributed to the change in composition of the ß-HOSO brought about by the 4-OMe group, which is ortho or para to each of the metal fragments. The intensity of the IVCT transition increases with the greater overlap of the ß-HOSO and ß-LUSO, whilst the relative phases of the ß-HOSO and ß-LUSO in the 4-OMe substituted complex are consistent with predictions of constructive quantum interference from molecular circuit rules.

Unravelling the role of [Ru(bpy)2(OH2)2]2+ complexes in photo-activated chemotherapy.

Photoactivated chemotherapy (PACT) has emerged as a promising strategy to selectively target cancer cells by using light irradiation to generate cytotoxic complexes in situ through a mechanism involving ligand-loss. Due to their rich optical properties and excited state chemistry, Ru polypyridyl complexes have attracted significant attention for PACT. However, studying PACT is complicated by the fact that many of these Ru complexes can also undergo excited-state electron transfer to generate 1O2 species. In order to deconvolute the biological roles of possible photo-decomposition products without the added complication of excited-state electron transfer chemistry, we have developed a methodology to systematically investigate each product individually, and assess the structure-function relationship. Here, we synthesized a series of eight distinct Ru polypyridyl complexes: Ru-Xa ([Ru(NN)3]2+), Ru-Xb ([Ru(NN)2py2]2+), and Ru-Xc ([Ru(NN)(OH2)2]2+) where NN = 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, or dimethyl 2,2'-bipyridine-4,4'-dicarboxylate and py = pyridine. The cytotoxicity of these complexes was investigated in two cell lines amenable to PACT: H23 (breast cancer) and T47D (lung cancer). We confirmed that light irradiation of Ru-Xa and Ru-Xb complexes generate Ru-Xc complexes through UV-visible spectroscopy, and observed that the Ru-Xc complexes are the most toxic against the cancer cell lines. In addition, we have shown that ligand release and biological activity including bovine serum albumin (BSA) binding, lipophilicity, and DNA interaction are altered when different groups are appended to the bipyridine ligands. We believe that the methodology presented here will enhance the development of more potent and selective PACT agents moving forward.

Deoxybuzonamine Isomers from the Millipede Brachycybe lecontii (Platydesmida: Andrognathidae).

Millipedes (Diplopoda) are well known for their toxic or repellent defensive secretions. Here, we describe (6aR,10aS,10bR)-8,8-dimethyldodecahydropyrrolo[2,1-a]isoquinoline [trans-anti-trans-deoxybuzonamine (1a)] and (rel-6aR,10aR,10bR)-8,8-dimethyldodecahydropyrrolo[2,1-a]isoquinoline [trans-syn-cis-deoxybuzonamine (1b)], two isomers of deoxybuzonamine found in the chemical defense secretions of the millipede Brachycybe lecontii Wood (Colobognatha, Platydesmida, Andrognathidae). The carbon-nitrogen skeleton of these compounds was determined from their MS and GC-FTIR spectra obtained from the MeOH extract of whole millipedes, along with a subsequent selective synthesis. Their structures were established from their 1D (1H, 13C) and 2D NMR (COSY, NOESY, multiplicity-edited HSQC, HSQC-TOCSY, HMBC) spectra. Additionally, computational chemistry (DFT and DP4) was used to identify the relative configurations of 1a and 1b by comparing predicted 13C data to their experimental values, and the absolute configuration of 1a was determined by comparing its experimental specific rotation with that of the computationally calculated value. This is the first report of dodecahydropyrrolo[2,1-a]isoquinoline alkaloids from a platydesmidan millipede.

Fine-Tuning Metal and Ligand-Centered Redox Potentials of Homoleptic Bis-Terpyridine Complexes with 4'-Aryl Substituents.

Homoleptic transition-metal complexes of 2,2':6',2″-terpyridine (terpy) and substituted derivatives of the form [M(R-terpy)2]2+ display a wide range of redox potentials that correlate well to the Hammett parameter of the terpy substituents. Less is known about the impact of incorporating a phenyl spacer between the functional group responsible for controlling the electron density of terpy and how that translates to metal complexes of the form [M(4'-aryl-terpy)2]2+, where M = Mn, Fe, Co, Ni, and Zn. Herein, we report our studies on these complexes revealed a good correlation of redox potentials of both metal- and ligand-centered events with the Hammett parameters of the aryl substituents, regardless of aryl-substitution pattern (i.e., the presence of multiple functional groups, combinations of withdrawing and donating functional groups). The phenyl spacer results in 60-80% attenuation of electron density as compared to the 4'-substituted terpy analogue, depending on the metal and redox couple analyzed. Density functional theory calculations performed on a simple model system revealed a strong correlation between the Hammett parameters and lowest unoccupied molecular orbital energies of the corresponding substituted pyridine models, thus serving as an inexpensive predictive tool when coupled with electrochemical data. Overall, these data suggest that such ligand modifications may be used in combination with previous approaches to further fine-tune the redox potentials of homoleptic transition-metal complexes, which may have applications in photochemical and electrochemical catalytic processes.

Gosodesmine, a 7-Substituted Hexahydroindolizine from the Millipede Gosodesmus claremontus.

Millipedes (Diplopoda) are well known for their toxic or repellent defensive secretions. Here we describe gosodesmine (1), 7-(4-methylpent-3-en-1-yl)-1,2,3,5,8,8a-hexahydroindolizine, a unique alkaloid with some terpene character found in the chemical defense secretions of the millipede Gosodesmus claremontus Chamberlin (Colobognatha, Platydesmida, Andrognathidae). The structure of 1 was suggested by its mass spectra and GC-FTIR spectra and established from its 1H, 13C, and 2D NMR spectra and 1D NOE studies. The 7-substituted indolizidine carbon skeleton of 1 was confirmed by unambiguous synthesis. This is the first report of an alkaloid from a platydesmid millipede and the first report of a 7-substituted indolizidine from an arthropod.

Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces.

A series of 18 ruthenium(II) polypyridyl complexes were synthesized and evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions experienced during the kinetically limited regime that can occur in dye-sensitized solar cells (DSSCs) and dye-sensitized photo-electrosynthesis cells, to further develop fundamental insights into the factors governing molecular sensitizer surface stability in aqueous 0.1 M HClO4. Both desorption and oxidatively induced ligand substitution were observed on planar fluorine-doped tin oxide (FTO) electrodes, with a dependence on the E1/2 Ru(III/II) redox potential dictating the comparative ratios of the processes. Complexes such as RuP4OMe ( E1/2 = 0.91 vs Ag/AgCl) displayed virtually only desorption, while complexes such as RuPbpz ( E1/2 > 1.62 V vs Ag/AgCl) displayed only chemical decomposition. Comparing isomers of 4,4'- and 5,5'-disubstituted-2,2'-bipyridine ancillary ligands, a dramatic increase in the rate of desorption of the Ru(III) complexes was observed for the 5,5'-ligands. Nanoscopic indium-doped tin oxide thin films (nanoITO) were also sensitized and analyzed with cyclic voltammetry, UV-vis absorption spectroscopy, and X-ray photoelectron spectroscopy, allowing for further distinction of desorption versus ligand-substitution processes. Desorption loss to bulk solution associated with the planar surface of FTO is essentially non-existent on nanoITO, where both desorption and ligand substitution are shut down with RuP4OMe. These results revealed that minimizing time spent in the oxidized form, incorporating electron-donating groups, maximizing hydrophobicity, and minimizing molecular bulk near the adsorbed ligand are critical to optimizing the performance of ruthenium(II) polypyridyl complexes in dye-sensitized devices.

A database of chlorophyll a in Australian waters.

Chlorophyll a is the most commonly used indicator of phytoplankton biomass in the marine environment. It is relatively simple and cost effective to measure when compared to phytoplankton abundance and is thus routinely included in many surveys. Here we collate 173, 333 records of chlorophyll a collected since 1965 from Australian waters gathered from researchers on regular coastal monitoring surveys and ocean voyages into a single repository. This dataset includes the chlorophyll a values as measured from samples analysed using spectrophotometry, fluorometry and high performance liquid chromatography (HPLC). The Australian Chlorophyll a database is freely available through the Australian Ocean Data Network portal (https://portal.aodn.org.au/). These data can be used in isolation as an index of phytoplankton biomass or in combination with other data to provide insight into water quality, ecosystem state, and relationships with other trophic levels such as zooplankton or fish.

Partitioning of fungal assemblages across different marine habitats.

Fungi are a highly diverse group of microbes that fundamentally influence the biogeochemistry of the biosphere, but we currently know little about the diversity and distribution of fungi in aquatic habitats. Here we describe shifts in marine fungal community composition across different marine habitats, using targeted pyrosequencing of the fungal Internal Transcribed Spacer (ITS) region. Our results demonstrate strong partitioning of fungal community composition between estuarine, coastal and oceanic samples, with each habitat hosting discrete communities that are controlled by patterns in salinity, temperature, oxygen and nutrients. Whereas estuarine habitats comprised a significant proportion of fungal groups often found in terrestrial habitats, the open ocean sites were dominated by previously unidentified groups. The patterns observed here indicate that fungi are potentially a significant, although largely overlooked, feature of the ocean's microbiota, but greater efforts to characterize marine species are required before the full ecological and biogeochemical importance of marine fungi can be ascertained.

Electrochemical Instability of Phosphonate-Derivatized, Ruthenium(III) Polypyridyl Complexes on Metal Oxide Surfaces.

The oxidative stability of the molecular components of dye-sensitized photoelectrosynthesis cells for solar water splitting remains to be explored systematically. We report here the results of an electrochemical study on the oxidative stability of ruthenium(II) polypyridyl complexes surface-bound to fluorine-doped tin oxide electrodes in acidic solutions and, to a lesser extent, as a function of pH and solvent with electrochemical monitoring. Desorption occurs for the Ru(II) forms of the surface-bound complexes with oxidation to Ru(III) enhancing both desorption and decomposition. Based on the results of long-term potential hold experiments with cyclic voltammetry monitoring, electrochemical oxidation to Ru(III) results in slow decomposition of the complex by 2,2'-bipyridine ligand loss and aquation and/or anation. A similar pattern of ligand loss was also observed for a known chromophore-catalyst assembly for both electrochemical water oxidation and photoelectrochemical water splitting. Our results are significant in identifying the importance of enhancing chromophore stability, or at least transient stability, in oxidized forms in order to achieve stable performance in aqueous environments in photoelectrochemical devices.

Reductive electropolymerization of a vinyl-containing poly-pyridyl complex on glassy carbon and fluorine-doped tin oxide electrodes.

Controllable electrode surface modification is important in a number of fields, especially those with solar fuels applications. Electropolymerization is one surface modification technique that electrodeposits a polymeric film at the surface of an electrode by utilizing an applied potential to initiate the polymerization of substrates in the Helmholtz layer. This useful technique was first established by a Murray-Meyer collaboration at the University of North Carolina at Chapel Hill in the early 1980s and utilized to study numerous physical phenomena of films containing inorganic complexes as the monomeric substrate. Here, we highlight a procedure for coating electrodes with an inorganic complex by performing reductive electropolymerization of the vinyl-containing poly-pyridyl complex onto glassy carbon and fluorine doped tin oxide coated electrodes. Recommendations on electrochemical cell configurations and troubleshooting procedures are included. Although not explicitly described here, oxidative electropolymerization of pyrrole-containing compounds follows similar procedures to vinyl-based reductive electropolymerization but are far less sensitive to oxygen and water.

Enantioenrichment of a tungsten dearomatization agent utilizing chiral acids.

A method is described for the resolution of the versatile dearomatization reagent TpW(NO)(PMe3)(η(2)-benzene), in which the 1,3-dimethoxybenzene (DMB) analogue of this complex is synthesized. In turn, the coordinated arene of TpW(NO)(PMe3)(DMB) is protonated with either D or L dibenzoyl tartaric acid (DBTH2) in a butanone/water or 2-pentanone/water solution. Sustained stirring of this mixture results in the selective precipitation of a single form of the diastereomeric salt [TpW(NO)(PMe3)(DMBH)](DBTH). After isolation, the salt can be redissolved, and the DMB ligand can be deprotonated and exchanged for benzene to produce the desired product TpW(NO)(PMe3)(η(2)-benzene) in either its R or S form. The absolute configuration of the tungsten stereocenter in TpW(NO)(PMe3)(η(2)-benzene) can be determined in either case by substituting the naturally occurring terpene (S)-ß-pinene for benzene and evaluating the 2D NMR spectrum of the corresponding ß-pinene complex.

Bacterioplankton Dynamics within a Large Anthropogenically Impacted Urban Estuary.

The abundant and diverse microorganisms that inhabit aquatic systems are both determinants and indicators of aquatic health, providing essential ecosystem services such as nutrient cycling but also causing harmful blooms and disease in impacted habitats. Estuaries are among the most urbanized coastal ecosystems and as a consequence experience substantial environmental pressures, providing ideal systems to study the influence of anthropogenic inputs on microbial ecology. Here we use the highly urbanized Sydney Harbor, Australia, as a model system to investigate shifts in microbial community composition and function along natural and anthopogenic physicochemical gradients, driven by stormwater inflows, tidal flushing and the input of contaminants and both naturally and anthropogenically derived nutrients. Using a combination of amplicon sequencing of the 16S rRNA gene and shotgun metagenomics, we observed strong patterns in microbial biogeography across the estuary during two periods: one of high and another of low rainfall. These patterns were driven by shifts in nutrient concentration and dissolved oxygen leading to a partitioning of microbial community composition in different areas of the harbor with different nutrient regimes. Patterns in bacterial composition were related to shifts in the abundance of Rhodobacteraceae, Flavobacteriaceae, Microbacteriaceae, Halomonadaceae, Acidomicrobiales, and Synechococcus, coupled to an enrichment of total microbial metabolic pathways including phosphorus and nitrogen metabolism, sulfate reduction, virulence, and the degradation of hydrocarbons. Additionally, community beta-diversity was partitioned between the two sampling periods. This potentially reflected the influence of shifting allochtonous nutrient inputs on microbial communities and highlighted the temporally dynamic nature of the system. Combined, our results provide insights into the simultaneous influence of natural and anthropogenic drivers on the structure and function of microbial communities within a highly urbanized aquatic ecosystem.

Water oxidation by an electropolymerized catalyst on derivatized mesoporous metal oxide electrodes.

A general electropolymerization/electro-oligomerization strategy is described for preparing spatially controlled, multicomponent films and surface assemblies having both light harvesting chromophores and water oxidation catalysts on metal oxide electrodes for applications in dye-sensitized photoelectrosynthesis cells (DSPECs). The chromophore/catalyst ratio is controlled by the number of reductive electrochemical cycles. Catalytic rate constants for water oxidation by the polymer films are similar to those for the phosphonated molecular catalyst on metal oxide electrodes, indicating that the physical properties of the catalysts are not significantly altered in the polymer films. Controlled potential electrolysis shows sustained water oxidation over multiple hours with no decrease in the catalytic current.

Probing the oxidation chemistry of half-sandwich iridium complexes with oxygen atom transfer reagents.

The new complexes [Ir(Cp*)(phpy)3,5-bis(trifluoromethyl)benzonitrile](+) (1-NCAr(+)) and [Ir(Cp*)(phpy)(styrene)](+) (1-Sty(+), Cp* = η(5)-pentamethylcyclopentadienyl, phpy = 2-phenylene-κC(1')-pyridine-κN) were prepared as analogues of reported iridium water oxidation catalysts, to study their reactions with oxygen atom transfer (OAT) reagents at low temperatures. In no case was the desired product, an Ir(V)oxo complex, observed by spectroscopy. Instead, ligand oxidation was implicated. Oxidation of 1-NCAr(+) with the OAT reagent dimethyldioxirane (DMDO) yielded dioxygen when analyzed by GC, but formation of a heterogeneous or paramagnetic species was simultaneously observed. This amplifies uncertainty over the actual identity of iridium catalysts in the harsh oxidizing conditions required for water oxidation. Catalyst stability was then assessed for a reported styrene epoxidation mediated by [Ir(Cp*)(phpy)(OH2)](+) (1-OH2(+)). It was found that the OAT reagent iodosobenzene (PhIO) extensively oxidized the organic ligands of 1-OH2(+). Acetic acid was detected as a decomposition product. In addition, both the molecular structure and the aqueous electrochemistry of 1-OH2(+) are described for the first time. Oxidative scans revealed rapid decomposition of the complex. All of the above experiments indicate that degradation of the organic ligands in catalysts built with the Ir(Cp*)(phpy) framework are facile under oxidizing conditions. In separate experiments designed to promote ligand substitution, an unexpected silver-bridged, dinuclear Ir(III) species with terminal hydrides, [{Ir(Cp*)(phpy)H}2Ag](+) (2), was discovered. The source of Ag(+) for complex 2 was identified as AgCl.

Strategies for stabilization of electrodeposited metal particles in electropolymerized films for H2O oxidation and H+ reduction.

Metal particles were electrodeposited on a variety of conducting substrates, and their electrocatalytic activity toward H2O oxidation to O2 and H(+) reduction to H2 was evaluated. Co, Ni, Cu, Pd, Ag, and Pt were all electrodeposited on fluorine-doped tin oxide (FTO) electrodes. Particularly active were Pd and Pt for H(+) reduction and Co and Ag for H2O oxidation. When cycled reductively in 0.1 M HClO4, FTO electrodes derivatized with Pt and Pd reached current densities for hydrogen evolution of 18.3 and 13.2 mA/cm(2), respectively, at -0.6 V vs normal hydrogen electrode (NHE). FTO electrodes with electrodeposited Co or Ag were cycled oxidatively in H2O buffered to pH 7 with phosphate buffer. Current densities of 10.5 and 8.70 mA/cm(2), respectively, were reached at +1.8 V vs NHE with H2O oxidation onsets at +1.3 and +1.4 V, respectively. The impacts on catalytic stability and performance of electrodeposited metals in/on an electrically conductive polymer support were also investigated. Films of poly-[Fe(vbpy)3](PF6)2 (vbpy is 4-methyl-4'-vinyl-2,2'-bipyridine) were generated on FTO by reductive electropolymerization. Significant improvements to the long-term stability of electrodeposited Ag and Pt particles were observed in the poly-[Fe(vbpy)3](PF6)2 support. Films of poly-[M(vbpy)3](PF6)2 with M = Co(II) or Cu(II) were also prepared and evaluated as electrocatalysts for H2O oxidation. Films containing Co(II) reached current densities of 6.0 mA/cm(2) at +1.8 V vs NHE in H2O.

Coordination chemistry of single-site catalyst precursors in reductively electropolymerized vinylbipyridine films.

Reductive electropolymerization of [Ru(II)(PhTpy)(5,5'-dvbpy)(Cl)](PF6) and [Ru(II)(PhTpy)(5,5'-dvbpy)(MeCN)](PF6)2 (PhTpy is 4'-phenyl-2,2':6',2″-terpyridine; 5,5'-dvbpy is 5,5'-divinyl-2,2'-bipyridine) on glassy carbon electrodes gives well-defined films of poly{[Ru(II)(PhTpy)(5,5'-dvbpy)(Cl)](PF6)} (poly-1) or poly{[Ru(II)(PhTpy)(5,5'-dvbpy)(MeCN)](PF6)2} (poly-2). Oxidative cycling of poly-2 with added NO3(-) results in the replacement of coordinated MeCN by NO3(-) to give poly{[Ru(II)(PhTpy)(5,5'-dvbpy)(NO3)](+)}, and with 0.1 M HClO4, replacement by H2O occurs to give poly{[Ru(II)(PhTpy)(5,5'-dvbpy)(OH2)](2+)} (poly-OH2). Although analogous aqua complexes (e.g., [Ru(tpy)(bpy)(OH2)](2+)) undergo rapid loss of H2O to MeCN in solution, poly-OH2 and poly-OH2(+) are substitutionally inert in MeCN. The substitution chemistry is reversible, with reductive scans of poly-1 or poly-OH2 in MeCN resulting in poly-2, although with some loss of Faradaic response.

Electron transfer dynamics of peptide-derivatized Ru(II) -polypyridyl complexes on nanocrystalline metal oxide films.

The performance of dye-sensitized solar and photoelectrochemical cells is strongly dependent on the electron transfer events at the electrode-sensitizer interface. Surface-bound peptides derivatized with chromophores have not been used in dye-sensitized solar and photoelectrochemical cells, but they have properties for these applications that could be advantageous by exploiting secondary structure and the attachment of multiple chromophores. In this manuscript, we have investigated structure-property relationships for three metallopeptide-based assemblies to solution and chemically bound to nanocrystalline MO(2) (M = Ti, Zr) films. A particular interest was exploring the influence of increasing separation distance between a common chromophore, [Ru(bpy)(2) (4-Me-4'-(NHCO)bpy)](2+) , and the underlying oxide substrate on excited and ground state electron transfer. Rates of Ru(II) oxidation to Ru(III) at the interface were measured by cyclic voltammetry on fluorine-doped tin oxide and cross-surface electron transfer on TiO(2) . Excited state injection by [Ru(III) (bpy)(2) (bpy(-) )](2+) was monitored by transient absorption and time-resolved emission. There are discernible trends in the electron transfer rate data with approximated, fully extended distances between the [Ru(bpy)(2) (4-Me-4'-(NHCO)bpy)](2+) sites and the interface. However, the distance dependences that are observed are smaller than anticipated, a result consistent with a lack of ordered secondary structure in the surface-bound peptide chains and a distribution of local orientations. For the surface-bound excited states, only a small fraction undergo quenching by electron transfer to TiO(2) , presumably from those oriented near the surface.