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We report new ruthenium complexes bearing the lipophilic bathophenanthroline (BPhen) ligand and dihydroxybipyridine (dhbp) ligands which differ in the placement of the OH groups ([(BPhen)(2)Ru(n,n′-dhbp)]Cl(2) with n = 6 and 4 in 1(A) and 2(A), respectively). Full characterization data are reported for 1(A) and 2(A) and single crystal X-ray diffraction for 1(A). Both 1(A) and 2(A) are diprotic acids. We have studied 1(A), 1(B), 2(A), and 2(B) (B = deprotonated forms) by UV-vis spectroscopy and 1 photodissociates but 2 is light stable. Luminescence studies reveal that the basic forms have lower energy (3)MLCT states relative to the acidic forms. Complexes 1(A) and 2(A) produce singlet oxygen with quantum yields of 0.05 and 0.68, respectively, in acetonitrile. Complexes 1 and 2 are both photocytotoxic towards breast cancer cells, with complex 2 showing EC(50) light values as low as 0.50 μM with PI values as high as >200 vs. MCF7. Computational studies were used to predict the energies of the (3)MLCT and (3)MC states. An inaccessible (3)MC state for 2(B) suggests a rationale for why photodissociation does not occur with the 4,4′-dhbp ligand. Low dark toxicity combined with an accessible (3)MLCT state for (1)O(2) generation explains the excellent photocytotoxicity of 2.

Ruthenium complexes bearing protic diimine ligands are cytotoxic to certain cancer cells upon irradiation with blue light. Previously reported complexes of the type [(N,N)(2)Ru(6,6’-dhbp)]Cl(2) with 6,6’-dhbp = 6,6’-dihydroxybipyridine and N,N = 2,2’-bipyridine (bipy) (1(A)), 1,10-phenanthroline (phen) (2(A)), and 2,3-dihydro-[1,4]dioxino[2,3-f][1,10]phenanthroline (dop) (3(A)) show EC(50) values as low as 4 μM (for 3(A)) vs. breast cancer cells upon blue light irradiation (Inorg. Chem. 2017, 56, 7519). Herein, subscript A denotes the acidic form of the complex bearing OH groups, and B denotes the basic form bearing O(−) groups. This photocytotoxicity was originally attributed to photodissociation, but recent results suggest that singlet oxygen formation is a more plausible cause of photocytotoxicity. In particular, bulky methoxy substituents enhance photodissociation but these complexes are non-toxic (Dalton Trans. 2018, 47, 15685). Cellular studies are presented herein that show the formation of reactive oxygen species (ROS) and apoptosis indicators upon treatment of cells with complex 3(A) and blue light. Singlet oxygen sensor green (SOSG) shows the formation of (1)O(2) in cell culture for cells treated with 3(A) and blue light. At physiological pH, complexes 1(A)-3(A) are deprotonated to form 1(B)-3(B) in situ. Quantum yields for (1)O(2) (ɸ(Δ) ) are 0.87 and 0.48 for 2(B) and 3(B) respectively, and these are an order of magnitude higher than the quantum yields for 2(A) and 3(A). The values for ɸ(Δ) show an increase with 6,6’-dhbp derived substituents as follows: OMe < OH < O(−). TD-DFT studies show that the presence of a low lying triplet metal-centered ((3)MC) state favors photodissociation and disfavors (1)O(2) formation for 2(A) and 3(A) (OH groups). However, upon deprotonation (O(−) groups), the (3)MLCT state is accessible and can readily lead to (1)O(2) formation, but the dissociative (3)MC state is energetically inaccessible. The changes to the energy of the (3)MLCT state upon deprotonation have been confirmed by steady state luminescence experiments on 1(A)-3(A) and their basic analogs, 1(B)-3(B). This energy landscape favors (1)O(2) formation for 2(B) and 3(B) and leads to enhanced toxicity for these complexes under physiological conditions. The ability to convert readily from OH to O(−) groups allowed us to investigate an electronic change that is not accompanied by steric changes in this fundamental study.

Polycyclic aromatic azaborines have potential applications as luminophores, novel fluorescent materials, organic light-emitting diodes, and fluorescent sensors. Additionally, their relative structural simplicity should allow the use of computational techniques to design and screen novel compounds in a rapid manner. Herein, the absorption and emission maxima of twelve polycyclic aromatic BN-1,2-azaborine analogues containing the N-BOH moiety were examined to determine a methodology for reliably predicting both the energy and character (local excitation [LE] vs charge transfer [CT]) of the absorption and emission maxima for these compounds. The necessity of implicit solvation models was also investigated. The cam-QTP(01) functional with a small, double-ζ quality basis set provides reliable data compared to EOM-CCSD/cc-pVDZ single-point computations. Of note, commonly used functionals for these applications (B3LYP and ωB97xD) struggle to provide reliable results for both the energy and LE character of the transitions relative to EOM-CCSD computations.

Malathion is a commercially available insecticide that functions by acting as an acetylcholinesterase inhibitor. Of more significant concern, if left in the environment, some of the products observed from the degradation of malathion can function as more potent toxins than the parent compound. These compounds may threaten human life if they are present in high quantities during operation in contaminated or industrial areas. Several experimental studies have been performed to elucidate the possible degradation products of malathion under various conditions to probe both the application of potential remediation methods and the environmental fate of the degradation products. However, only limited computational studies have been reported to delineate the mechanism by which malathion degrades under environmental conditions and how these degradation mechanisms are intertwined with one another. Herein, M06-2X DFT computations were employed to develop comprehensive degradation pathways from the parent malathion compound to a multitude of experimentally observed degradation products. These data corroborate experimental observations that multiple degradation pathways (ester hydrolysis and elimination) are in competition with each other, and the end-products can therefore be influenced by environmental factors such as temperature. Furthermore, the products resulting from any of the initial degradation pathways (ester hydrolysis, elimination, or P-S hydrolysis) can continue to degrade under the same conditions into compounds that are also reported to be toxic.

Malathion is a commercially available insecticide that functions by acting as an acetylcholinesterase inhibitor. Of significant concern, if left in the environment, some of the products observed from the degradation of malathion can function as more potent toxins than the parent compound. Accordingly, there are numerous studies revolving around possible degradation strategies to remove malathion from various environmental media. One of the possible approaches is the degradation of malathion by OH˙ radicals which could be produced from both artificial and biological means in the environment. While there is plenty of evidence that OH˙ does in fact degrade malathion, there is little understanding of the underlying mechanism by which OH˙ reacts with malathion. Moreover, it is not known how competitive the radical degradation pathway is with analogous alkaline degradation pathways. Even less is known about the reaction of additional OH˙ radicals with the degradation byproducts themselves. Herein, we demonstrate that OH˙ induced degradation pathways have variable competitiveness with OH

Five ruthenium catalysts described herein facilitate self-sensitized carbon dioxide reduction to form carbon monoxide with a ruthenium catalytic center. These catalysts include four new and one previously reported CNC pincer complexes featuring a pyridinol derived N-donor and N-heterocyclic carbene (NHC) C-donors derived from imidazole or benzimidazole. The complexes have been characterized fully by spectroscopic and analytic methods, including X-ray crystallography. Introduction of a 2,2'-bipyridine (bipy) coligand and phenyl groups on the NHC ligand was necessary for rapid catalysis. [(CNC)Ru(bipy)(CH

Cyanobacteria use limiting resources efficiently to take advantage of nutrient pulses, adapt to variable surroundings, and spread; this proliferation is often an indicator of ecosystem stress. We documented the sudden appearance of benthic cyanobacterial mats on a subtidal rocky reef (Roca Cousins, Galapagos Islands) during El Nino in January 2016. At this time, cyanobacteria covered 32.0% of horizontal rock surfaces and 2.6% of rock walls at 6–8 m depth. Monitored photo quadrats and observations indicated that these mats were previously absent from rock walls and horizontal-sloping substrata at this site for 16 years prior to their initial appearance. The cyanobacteria was also observed at 4 other sites in the central Galapagos Islands during 2016–2018. Laboratory experiments testing the effects of temperature (28–31 °C) on cyanobacterial growth and survival indicated that survival was higher at 28 than 31 °C, suggesting that 31 °C may be an upper thermal limit. Over two years in the field, cyanobacterial mats peaked during the warm El Nino (January 2016) and declined during two cold La Nina periods (June 2016, September 2017), ultimately declining to 6.0% cover in January 2018. Regression analysis of the temperature and cyanobacterial percent cover data indicated that temperature explained 56.9% of the variation in cyanobacteria cover in the field over the 2-year period. The cyanobacterial mats may be a consortium of several species as the closest genetic matches confirmed by Sanger sequencing (90–91.5%) were Oscillatoria spongeliae, Merismopedia glauca , and Synechococcus elongatus . Comparison of areas under the cyanobacterial mats to the adjacent uncovered rock substrata suggested that the cyanobacteria had a negative influence on underlying crustose coralline algae (CCA), as the cover of bleached CCA was 1.75 fold higher under the mats while the cover of “healthy” pink-pigmented CCA was 3 fold higher on the uncovered substrata. Short-term field experiments and feeding surveys performed to evaluate predation and to calculate electivity indices indicated that the cyanobacterial mats were avoided by dominant consumers ( Eucidaris galapagensis, Pentaceraster cumingi, Nidorellia armata , and Prionurus laticlavius ). Taken together, these results imply that the novel appearance of cyanobacterial mats in the Galapagos rocky subtidal zone was facilitated by unusually warm temperatures during the 2014–2017 El Nino (28–29 °C) and that the cyanobacteria were regulated by temperature, but not by consumers. Future outbreaks of mat-forming cyanobacteria during El Nino periods may negatively impact the abundance of CCA and have direct and indirect negative effects on other components of marine benthic communities that rely on CCA as either a settlement substratum or food source.

Sea stars (class Asteroidea) can play powerful and wide-ranging roles as consumers of algae and prey items in benthic ecosystems worldwide. In the Galápagos rocky subtidal zone, sea stars are abundant and diverse but their distribution, feeding habits and ecological impacts have received little attention. We compared diets and distributions across the six most abundant sea star species to examine functional roles of this important group. Bi-annual censuses carried out between 2006–2014 at two depths (6-8m, 12-15m) at 12 sites in Galápagos identified two abundance “hotspots” and revealed higher densities at locations with more heterogeneous benthic topographies. Field surveys revealed a high incidence of feeding (35–68% of individuals across species) and distinct diets were evident for each species in terms of food items and dietary breadth, suggesting niche partitioning. Most species can be classified as facultative herbivores, with diets dominated by crustose and turf algae supplemented by a small proportion of sessile invertebrates. The two most abundant species (Pentaceraster cumingi and Nidorellia armata) had the narrowest diets. Field prey selectivity experiments identified P. cumingi as a size-selective predator of the pencil urchin Eucidaris galapagensis. In field caging experiments, N. armata reduced biomass of unbleached crustose coralline algae and macroalgae by 72% and 52%, respectively. In the context of emerging threats such as disease, ocean acidification and climate change, a deeper understanding of distinct functional roles can inform ecological models and management plans.

Formation of Co(III) complexes was achieved via transmetallation with CoCl2 or Co(acac)3 of an isolated CCC–NHC pincer Zr complex. Four new crystal structures are reported, which expand upon the limited scope of first-row transition metal CCC–NHC pincer complexes. DFT computations were utilized to analyze the thermodynamics of cleaving a dimeric cobalt pincer complex with dimethylamine.

Diversity patterns are determined by biogeographic, energetic, and anthropogenic factors, yet few studies have combined them into a large‐scale framework in order to decouple and compare their relative effects on fish faunas. Using an empirical dataset derived from 1527 underwater visual censuses (UVC) at 18 oceanic islands (five different marine provinces), we determined the relative influence of such factors on reef fish species richness, functional dispersion, density and biomass estimated from each UVC unit. Species richness presented low variation but was high at large island sites. High functional dispersion, density, and biomass were found at islands with large local species pool and distance from nearest reef. Primary productivity positively affected fish richness, density and biomass confirming that more productive areas support larger populations, and higher biomass and richness on oceanic islands. Islands densely populated by humans had lower fish species richness and biomass reflecting anthropogenic effects. Species richness, functional dispersion, and biomass were positively related to distance from the mainland. Overall, species richness and fish density were mainly influenced by biogeographical and energetic factors, whereas functional dispersion and biomass were strongly influenced by anthropogenic factors. Our results extend previous hypotheses for different assemblage metrics estimated from empirical data and confirm the negative impact of humans on fish assemblages, highlighting the need for conservation of oceanic islands. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)

We report the crystallography, emission spectra, femtosecond pump-probe spectroscopy, and density functional theory computations for a series of ruthenium complexes that comprise a new class of chelating triphenylphosphine based ligands with an appended sulfoxide moiety. These ligands differ only in the presence of the para-substitutent (e.g., H, OCH3, CF3). The results show a dramatic range in photoisomerization reactivity that is ascribed to differences in the electron density of the phosphine ligand donated to the ruthenium and the nature of the excited state.

We report herein a mononuclear, homogeneous photocatalyst for H2 production with sunlight. The synthesis and characterization of a (pyridyl)-N-heterocyclic carbene tungsten tetracarbonyl complex W(pyNHC)(CO)4 is described, and its application as a precatalyst for photocatalytic generation of H2 is evaluated. Electrochemical and photophysical studies were used to characterize and evaluate the precatalyst and in situ generated catalyst [W(pyNHC)(CO)3] for the visible-light-driven production of H2 in the presence of triflic acid and decamethylferrocene without an additional photosensitizer. Under irradiation with a solar-simulated spectrum, a catalyst turnover number (TON) of >17 in 3 h of reaction time is observed for the production of H2 with this system, which compares favorably to a prior reported (multinuclear) homogeneous photocatalyst using visible light (4 TON). Photonic energy was found to be necessary to access the active catalysts from the precatalyst and in the catalytic cycle. A mechanism is det...

The first example of a CNC pincer ligand with a central pyridinol ligand is reported in a nickel(ii) complex. This metal complex can be protonated or deprotonated reversibly in situ to switch on or off the photocatalytic performance towards CO2 reduction. The O- substituent appears essential for catalysis.

Predators select prey so as to maximize energy and minimize manipulation time. In order to reduce prey detection and handling time, individuals must actively select their foraging space (microhabitat) and populations exhibit morphologies that are best suited for capturing locally available prey. We explored how variation in diet correlates with habitat type, and how these factors influence key morphological structures (mouth gape, eye diameter, fin length, fin area, and pectoral fin ratio) in a common microcarnivorous cryptic reef fish species, the triplefin Helcogrammoides cunninghami. In a mensurative experiment carried out at six kelp‐dominated sites, we observed considerable differences in diet along 400 km of the Chilean coast coincident with variation in habitat availability and prey distributions. Triplefins preferred a single prey type (bivalves or barnacles) at northern sites, coincident with a low diversity of foraging habitats. In contrast, southern sites presented varied and heterogeneous habitats, where triplefin diets were more diverse and included amphipods, decapods, and cumaceans. Allometry‐corrected results indicated that some morphological structures were consistently correlated with different prey items. Specifically, large mouth gape was associated with the capture of highly mobile prey such as decapods, while small mouth gape was more associated with cumaceans and copepods. In contrast, triplefins that capture sessile prey such as hydroids tend to have larger eyes. Therefore, morphological structures co‐vary with habitat selection and prey usage in this species. Our study shows how an abundant generalist reef fish exhibits variable feeding morphologies in response to the distribution of potential habitats and prey throughout its range.

The metallation/transmetallation strategy has been successfully applied to the preparation of CCC-NHC pincer nickel complexes. Manipulation of the coordination sphere lead to cationic CCC-NHC pincer nickel complexes. These were found to exhibit polymorphism in the solid state with significant differences in the intermolecular distances observed by X-ray crystallography. Three polymorphs were observed for the PF6− salt, and two were observed for the BF4− salt. When BPh4− was the counterion only one morphology was observed, and crystals grown of the triflate salt were too small for analysis. Details of the differences are documented for comparison. Additionally, during crystallization it was found that a rearrangement of the CCC-NHC ligand had occurred, involving coupling of an NHC from two different ligands, which were oxidized.

Environmental stress impedes predation and herbivory by limiting the ability of animals to search for and consume prey. We tested the contingency of this relationship on consumer traits and specifically hypothesized that herbivore mobility relative to the return time of limiting environmental stress would predict consumer effects. We examined how wave-induced water motion affects marine communities via herbivory by highly mobile (fish) vs. slow-moving (pencil urchin) consumers at two wave-sheltered and two wave-exposed rocky subtidal locations in the Galapagos Islands. The exposed locations experienced 99th percentile flow speeds that were 2-5 times greater than sheltered locations, with mean flow speeds >33 cm/s vs.

Climate change increases local climatic variation and unpredictability, which can alter ecological interactions and trigger wildlife disease outbreaks. Here we describe an unprecedented multi-species outbreak of wild fish disease driven by a climate perturbation. The 2015–16 El Niño generated a +2.5 °C sea surface temperature anomaly in the Galapagos Islands lasting six months. This coincided with a novel ulcerative skin disease affecting 18 teleost species from 13 different families. Disease signs included scale loss and hemorrhagic ulcerated patches of skin, fin deterioration, lethargy, and erratic behavior. A bacterial culture isolated from skin lesions of two of the affected fish species was identified by sequencing of the 16S rRNA gene as a Rahnella spp. Disease prevalence rates were linearly correlated with density in three fish species. In January 2016, disease prevalence reached 51.1% in the ring-tailed damselfish Stegastes beebei (n = 570) and 18.7% in the king angelfish Holacanthus passer (n = 318), corresponding to 78% and 86% decreases in their populations relative to a 4.5-year baseline, respectively. We hypothesize that this outbreak was precipitated by the persistent warm temperatures and lack of planktonic productivity that characterize extreme El Niño events, which are predicted to increase in frequency with global warming.

Manipulative field experiments provide a window into the complexity of nature. Yet there is concern that we lack resolution by conducting experiments on a scale that is too small and short to include the relevant complexity of the study system. We addressed this issue by asking how and why the scale (local and global spatial extent, spatial grain, duration) and complexity (number of species, factors, treatment combinations) of experiments performed on marine hard substrata (rocky intertidal, RI; coral reef, CR; rocky subtidal, RS; mangrove root, MR) has changed by assessing 311 total experiments published since 1961 in Ecology and Ecological Monographs and since 1967 in Journal of Experimental Marine Biology and Ecology. We show that the local spatial extent and all metrics of complexity increased as a positive, log-linear function of time. In contrast, the size of experimental units (spatial grain) decreased with time. Quantile regression analysis revealed that these trends are largely driven by changes ...

Nine new polycyclic aromatic BN-1,2-azaborine analogues containing the N-BOH moiety were synthesized using a convenient two-step, one-pot procedure. Characterization of the prepared compounds show the luminescence wavelength and the quantum yields of the azaborines were tunable by controlling the power and location of the donor and acceptor substituents on the chromophore. UV-visible spectroscopy and density functional theory (DFT) computations revealed that the addition of electron-donating moieties to the isoindolinone hemisphere raised the energy of the HOMO, resulting in the reduction of the HOMO–LUMO gap. The addition of an electron-accepting moiety to the isoindolinone hemisphere and an electron-donating group to the boronic acid hemisphere decreased the HOMO–LUMO gap considerably, leading to emission properties from partial intramolecular charge transfer (ICT) states. The combined effect of an acceptor on the isoindolinone side and a donor on the boronic acid side (strong acceptor–π-donor) gave the most red-shifted absorption. The polycyclic aromatic BN-1,2-azaborines emitted strong fluorescence in solution and in the solid-state with the largest red-shifted emission at 640 nm and a Stokes shift of Δλ = 218 nm, or Δν = 8070 cm−1.

Habitat selection and predation are ecological processes that operate at small spatial scales. How these influence large-scale patterns in abundance and distribution of fauna remains to be resolved, especially in structurally complex systems such as kelp

Marine reserves can directly replenish heavily fished species. However, communitywide effects of reserves are less clear. Marine reserves directly reduce fishing mortality rates, but through the restoration of apex predators, reserves may have strong indirect effects on non-target species. We explored the effects of a large, fully protected marine reserve in the Bahamas on the community of coral-reef fishes. We examined the effect of the reserve on fish biomass by comparing the density and size of all fishes on similar reefs located inside and outside the reserve. Total biomass of fishes was approximately 7× higher in reserve sites, where biomass was strongly concentrated in species of higher trophic levels. Analysis based on the relative magnitude of individual species’ responses indicated that, on average, the largest species increased in biomass within the reserve, intermediate-sized species decreased, and the smallest species exhibited variable responses. Species’ responses to the reserve were also examined by pooling species into 9 trophic categories using consumptive relationships, which provided corroborating results. Large piscivores (e.g. sharks, large groupers) were on average larger and more abundant inside the reserve. Mid-trophic-level groups (e.g. small piscivores) had higher average biomass outside of the reserve, where the number of species and biomass of large predators was lower. Finally, some low-trophic-level groups (e.g. planktivores) had higher biomass within the reserve, while others (e.g. small herbivores) did not respond strongly. Overall, these results suggest that marine reserves can substantially alter the composition and structure of reef fish communities.

Kelp forests provide important ecosystem services, yet coastal kelp communities are increasingly altered by anthropogenic impacts. Kelp forests in remote, offshore locations may provide an informative contrast due to reduced impacts from local stressors. We tested the hypothesis that shallow kelp assemblages (12-15 m depth) and associated fish and benthic communities in the coastal southwest Gulf of Maine (GOM) differed significantly from sites on Cashes Ledge, 145 km offshore by sampling five coastal and three offshore sites at 43.0 +/- 0.07° N latitude. Offshore sites on Cashes Ledge supported the greatest density (47.8 plants m2) and standing crop biomass (5.5 kg m2 fresh weight) of the foundation species Saccharina latissima kelp at this depth in the Western North Atlantic. Offshore densities of S. latissima were over 150 times greater than at coastal sites, with similar but lower magnitude trends for congeneric S. digitata. Despite these differences, S. latissima underwent a significant 36.2% decrease between 1987 and 2015 on Cashes Ledge, concurrent with a rapid warming of the GOM and invasion by the kelp-encrusting bryozoan Membranipora membranacea. In contrast to kelp, the invasive red alga Dasysiphonia japonica was significantly more abundant at coastal sites, suggesting light or dispersal limitation offshore. Spatial differences in fish abundance mirrored those of kelp, as the average biomass of all fish on Cashes Ledge was 305 times greater than at the coastal sites. Remote video censuses of cod (Gadus morhua), cunner (Tautaogolabrus adspersus), and pollock (Pollachius virens) corroborated these findings. Understory benthic communities also differed between regions, with greater abundance of sessile invertebrates offshore. Populations of kelp-consuming sea urchins Stronglyocentrotus droebachiensis, were virtually absent from Cashes Ledge while small urchins were abundant onshore, suggesting recruitment limitation offshore. Despite widespread warming of the GOM since 1987, extraordinary spatial differences in the abundance of primary producers (kelp), consumers (cod) and benthic communities between coastal and offshore sites have persisted. The shallow kelp forest communities offshore on Cashes Ledge represent an oasis of unusually high kelp and fish abundance in the region, and as such, comprise a persistent abundance hotspot that is functionally significant for sustained biological productivity of offshore regions of the Gulf of Maine.

2,6-Dialkyl-phenols exhibit little steric hindrance on reaction with phosphoryl chloride unless the alkyl substituent is bulky (i.e. t-butyl). Where bulky substituents are present reaction with phosphoryl chloride occurs only in the presence of Friedel–Crafts type catalysts after either a dealkylation or a rearrangement of the ortho-placed alkyl groups, followed by O-phosphorylation, has occurred.