A Ru(II)-Strained Complex with 2,9-Diphenyl-1,10-phenanthroline Ligand Induces Selective Photoactivatable Chemotherapeutic Activity on Human Alveolar Carcinoma Cells via Apoptosis.

[Ru(bipy)2(dpphen)]Cl2 (where bipy = 2,2'-bipyridine and dpphen = 2,9-diphenyl-1,10-phenanthroline) (complex 1) is a sterically strained compound that exhibits promising in vitro photocytotoxicity on an array of cell lines. Since lung adenocarcinoma cancer remains the most common lung cancer and the leading cause of cancer deaths, the current study aims to evaluate the plausible effect and uptake of complex 1 on human alveolar carcinoma cells (A549) and mesenchymal stem cells (MSC), and assess its cytotoxicity in vitro while considering its effect on cell morphology, membrane integrity and DNA damage. MSC and A549 cells showed similar rates of complex 1 uptake with a plateau at 12 h. Upon photoactivation, complex 1 exhibited selective, potent anticancer activity against A549 cells with phototoxicity index (PI) values of 16, 25 and 39 at 24, 48 and 72 h, respectively. This effect was accompanied by a significant increase in A549-cell rounding and detachment, loss of membrane integrity and DNA damage. Flow cytometry experiments confirmed that A549 cells undergo apoptosis when treated with complex 1 followed by photoactivation. In conclusion, this present study suggests that complex 1 might be a promising candidate for photochemotherapy with photoproducts that possess selective anticancer effects in vitro. These results are encouraging to probe the potential activity of this complex in vivo.

Risk Assessment of Phthalates and Their Metabolites in Hospitalized Patients: A Focus on Di- and Mono-(2-ethylhexyl) Phthalates Exposure from Intravenous Plastic Bags.

Phthalate esters (PAEs) are plasticizers associated with multiple toxicities; however, no strict regulations have been implemented to restrict their use in medical applications in Lebanon. Our study aimed at assessing the potential risks correlated with phthalate exposure from IV bags manufactured in Lebanon. GC-MS analysis showed that di-(2-ethylhexyl) phthalate (DEHP) is the predominant phthalate found in almost all samples tested with values ranging from 32.8 to 39.7% w/w of plastic. DEHP concentrations in the IV solutions reached up to 148 µg/L, as measured by SPME-GC-MS/MS, thus resulting in hazard quotients greater than 1, specifically in neonates. The toxicity of DEHP is mainly attributed to its metabolites, most importantly mono-(2-ethylhexyl) phthalate (MEHP). The IV bag solution with the highest content in DEHP was therefore used to extrapolate the amounts of urinary MEHP. The highest concentrations were found in neonates having the lowest body weight, which is concerning, knowing the adverse effects of MEHP in infants. Our study suggests that the use of IV bags manufactured in Lebanon could pose a significant risk in hospitalized patients, especially infants in neonatal care. Therefore, Lebanon, as well as other countries, should start imposing laws that restrict the use of phthalates in medical IV bags and substitute them with less toxic plasticizers.

Acute cytotoxicity, genotoxicity, and apoptosis induced by petroleum VOC emissions in A549 cell line.

Gasoline is an essential petroleum-derived product powering the automotive economy worldwide. This research focused on the Volatile Organic Component (VOC) cocktail resulting from gasoline evaporation. Petroleum fugitive VOC inhalation by petrol station attendants have been widely associated with toxicological and health risks concerns. Another unusual practice in poor nations is gasoline sniffing to get high which can lead to intoxication and organ damages. In this study, a static air/liquid interface methodology was designed to emulate acute human lung-derived cell exposure to all the gasoline-derived generated VOCs. The research investigated the cytotoxic and genotoxic end points resulting from whole gasoline fumes in vitro exposure using A549 cells. Petroleum-derived VOCs were identified and characterized by GC-MS. VOCs exposure was emulated in a controlled environment by evaporating spiked crude gasoline (1 to 100 µl) in a closed exposure chamber. In the chamber, A549 cultured cells on snapwell inserts were exposed on their apical side to various concentrations of generated vapors for one hour at 37 °C to mimic lung exposure. The results indicated that acute gasoline whole VOCs exposure reduced cell viability (IC50 = 485 ppm immediately and IC50 = 516 ppm 24 h post-exposure), disrupted cell membrane integrity though LDH leakage and induced DNA damages. Furthermore, VOC exposure triggered caspase-independent apoptosis in exposed cells through upregulation of apoptotic pathways. Overall, the presented findings generated by the static exposure technique showed a practical and reproducible model that can be used to assess acute crude VOCs mixture toxicity endpoints and cell death pathways.

Gasoline fume inhalation induces apoptosis, inflammation, and favors Th2 polarization in C57BL/6 mice.

Gasoline exposure has been widely reported in the literature as being toxic to human health. However, the exact underlying molecular mechanisms triggered by its inhalation have not been thoroughly investigated. We herein present a model of sub-chronic, static gasoline vapor inhalation in adult female C57BL/6 mice. Animals were exposed daily to either gasoline vapors (0.86 g/animal/90 min) or ambient air for 5 days/week over 7 consecutive weeks. At the end of the study period, toxic and molecular mechanisms underlying the inflammatory, oxidative, and apoptotic effects triggered by gasoline vapors, were examined in the lungs and liver of gasoline-exposed (GE) mice. Static gasoline exposure induced a significant increase (+21%) in lungs/body weight (BW) ratio in GE versus control (CON) mice along with a pulmonary inflammation attested by histological staining. The latter was consistent with increases in the transcript levels of proinflammatory cytokines [Interleukins (ILs) 4 and 6], respectively by ~ 6- and 4-fold in the lungs of GE mice compared to CON. Interestingly, IL-10 expression was also increased by ~ 10-fold in the lungs of GE mice suggesting an attempt to counterbalance the established inflammation. Moreover, the pulmonary expression of IL-12 and TNF-α was downregulated by 2- and 4-fold, respectively, suggesting the skewing toward Th2 phenotype. Additionally, GE mice showed a significant upregulation in Bax/Bcl-2 ratio, caspases 3, 8, and 9 with no change in JNK expression in the lungs, suggesting the activation of both intrinsic and extrinsic apoptotic pathways. Static gasoline exposure over seven consecutive weeks had a minor hepatic portal inflammation attested by H&E staining along with an increase in the hepatic expression of the mitochondrial complexes in GE mice. Therefore, tissue damage biomarkers highlight the health risks associated with vapor exposure and may present potential therapeutic targets for recovery from gasoline intoxication.

Drug-free phototherapy of superficial tumors: White light at the end of the tunnel.

Visible light has long been recognized as a treatment for many diseases and an essential component of photo-induced chemotherapy. While previous data proved its inherent cytotoxicity, this study is the first to explore the use of a commercially available, high-intensity white LED light (24.5 mW.cm-2) as a treatment for skin tumors. After a 9-h exposure in vitro, the viability of Human Malignant Melanoma cells (A375) decreased by around 70%. Western blot analysis suggested an apoptotic cell death confirmed by the upregulation of Bax, cleaved PARP/caspase-3/8, cytochrome c, and t-bid. Additionally, cellular ROS accumulation and DNA damage were induced upon irradiation with blue light. When tested on a DMBA/TPA skin carcinogenesis model, a 90-min exposure to white light thrice weekly resulted in a significant decrease in tumor volumes/incidence compared to control and cisplatin groups, and restored normal morphological features, as confirmed by histopathology. Toxicological evaluation of ight-treated animals indicated a 100% survival rate, no skin irritation, no signs of discomfort or changes in body weight/behavior, and no toxicities to vital organs. Although these results must be confirmed by further studies, this research showed that short-exposure by commercially available high-intensity white LED light irradiation may be a promising approach for the treatment of superficial malignancies.

A photoactivatable chemotherapeutic Ru(II) complex bearing bathocuproine ligand efficiently induces cell death in human malignant melanoma cells through a multi-mechanistic pathway.

Photoactivated chemotherapy (PACT) is an emerging strategy for targeted cancer therapy. Strained Ru complexes with pseudo-octahedral geometry may undergo photo-induced ligand dissociation, forming aquated photoproducts that are significantly more cytotoxic compared to the precursor complex. The complexes investigated were the strained complex [Ru(bpy)2BC]Cl2 (where bpy = 2,2'-bipyridine and BC = bathocuproine) and its unstrained control [Ru(bpy)2phen]Cl2 (where phen = 1,10-phenanthroline). The uptake of [Ru(bpy)2BC]Cl2, assessed by ICP/MS, started immediately post-incubation and plateaued after 24 h. Active transport was found as the main mode of intracellular transport. Cell viability assays on A375 cells indicated a mean phototoxicity index of 340-fold, and the effect was shown to be primarily mediated by the aquated photoproducts rather than the dissociating ligands. A significant increase in ROS production and DNA damage was also observed. Flow cytometry confirmed the induction of early apoptosis at 48 h that proceeds to late apoptosis/necrosis by 72 h post-treatment. Western blot analysis of pro- and anti-apoptotic proteins revealed that apoptosis was mediated through an interplay between the intrinsic and extrinsic pathways, as well as autophagy and via inhibition of the MAPK and PI3K pathways. In conclusion, this study demonstrates that [Ru(bpy)2BC]Cl2 is a multi-mechanistic PACT drug which exhibits promising anticancer potential.

E-cigarette aerosol induced cytotoxicity, DNA damages and late apoptosis in dynamically exposed A549 cells.

In this study, the acute toxicological impacts associated with electronic cigarettes consumption were determined using a novel dynamic exposure methodology. The methodology was deployed to test various e-cigarette generated aerosols in A549 cell cultures. The e-liquid chemical profiling was achieved using GC-MS analysis while toxicity of diluted e-liquids aerosols was reported using numerous cytotoxicity assays. The presented findings pointed to acute aerosol exposure (thirty puffs at 40 W of power and higher) inducing significant cytotoxic, genotoxic, and apoptotic induction in exposed cells. These findings highlighted the significant risks posed by e-cigarette usage. The proposed methodology proved to be a useful tool for future screening of e-liquids generated aerosols toxicity. Future research is needed to establish the chronic toxicity resulting from long-term e-cigarette consumption.

The anti-cancer effect of series of strained photoactivatable Ru(II) polypyridyl complexes on non-small-cell lung cancer and triple negative breast cancer cells.

Ruthenium complexes have been recently reported as potential chemotherapeutic agents that offer tumor selectivity and low tumor resistance. This study investigates the photochemistry and the effect of four strained photoactivatable polypyridyl ruthenium(II) complexes on non-small-cell lung cancer (A549) and triple negative breast cancer (MDA-MB-231) cells. All four ruthenium(II) complexes, [Ru(bpy)2dmbpy]Cl2 (C1) where (bpy = 2,2'-bipyridine and dmbpy = 6,6'-dimethyl-2,2'-bipyridine), [Ru(phen)2dmbpy]Cl2 (C2) where (phen = 1,10-phenanthroline), [Ru(dpphen)2dmbpy]Cl2 (C3) (where dpphen = 4,7-diphenyl-1,10-phenanthroline) and [Ru(BPS)2dmbpy]Na2 (C4) where (BPS = bathophenanthroline disulfonate) eject the dmbpy ligand upon activation by blue light. Determination of the octanol-water partition coefficient (log P) revealed that C3 was the only lipophilic complex (log P = 0.42). LC-MS/MS studies showed that C3 presented the highest cellular uptake. The cytotoxic effect of the complexes was evaluated with and without blue light activation using WST-1 kit. Data indicated that C3 exhibited the highest cytotoxicity after 72 h (MDA-MB-231, IC50 = 0.73 µM; A549, IC50 = 1.26 µM) of treatment. The phototoxicity indices of C3 were 6.56 and 4.64 for MDA-MB-230 and A549, respectively. Upon light activation, C3 caused significant ROS production and induced apoptosis in MDA-MB-231 cells as shown by flow cytometry. It also significantly increased Bax/Bcl2 ratio and PERK levels without affecting caspase-3 expression. C3 exhibited poor dark toxicity (IC50 = 74 µM) on rat mesenchymal stem cells (MSCs). In conclusion, the physical property of the complexes dictated by the variable ancillary ligands influenced cellular uptake and cytotoxicity. C3 may be considered a promising selective photoactivatable chemotherapeutic agent that induces ROS production and apoptosis.

A photoactivatable Ru (II) complex bearing 2,9-diphenyl-1,10-phenanthroline: A potent chemotherapeutic drug inducing apoptosis in triple negative human breast adenocarcinoma cells.

The photoactivatable Ru (II) complex 1 [Ru(bipy)2(dpphen)]Cl2 (where bipy = 2,2'-bipyridine and dpphen = 2,9-diphenyl-1,10-phenanthroline) has been shown to possess promising anticancer activity against triple negative adenocarcinoma MDA-MB-231 cells. The present study aims to elucidate the plausible mechanism of action of the photoactivatable complex 1 against MDA-MB-231 cells. Upon photoactivation, complex 1 exhibited time-dependent cytotoxic activity with a phototoxicity index (P Index) of >100 after 72 h. A significant increase in cell rounding and detachment, loss of membrane integrity, ROS accumulation and DNA damage was observed. Flow cytometry and a fluorescent apoptosis/necrosis assay showed an induction of cell apoptosis. Western blot analysis revealed the induction of intrinsic and extrinsic pathways and inhibition of the MAPK and PI3K pathways. The photoproduct of complex 1 showed similar effects on key apoptotic protein expression confirming that it is behind the observed cell death. In conclusion, the present study revealed that complex 1 is a potent multi-mechanistic photoactivatable chemotherapeutic drug that may serve as a potential lead molecule for targeted cancer chemotherapy.

Plasma and urine metabolomic analyses in aortic valve stenosis reveal shared and biofluid-specific changes in metabolite levels.

Aortic valve stenosis (AVS) is a prevalent condition among the elderly population that eventually requires aortic valve replacement. The lack of reliable biomarkers for AVS poses a challenge for its early diagnosis and the application of preventive measures. Untargeted gas chromatography mass spectrometry (GC-MS) metabolomics was applied in 46 AVS cases and 46 controls to identify plasma and urine metabolites underlying AVS risk. Multivariate data analyses were performed on pre-processed data (e.g. spectral peak alignment), in order to detect changes in metabolite levels in AVS patients and to evaluate their performance in group separation and sensitivity of AVS prediction, followed by regression analyses to test for their association with AVS. Through untargeted analysis of 190 urine and 130 plasma features that could be detected and quantified in the GC-MS spectra, we identified contrasting levels of 22 urine and 21 plasma features between AVS patients and control subjects. Following metabolite assignment, we observed significant changes in the concentration of known metabolites in urine (n = 14) and plasma (n = 15) that distinguish the metabolomic profiles of AVS patients from healthy controls. Associations with AVS were replicated in both plasma and urine for about half of these metabolites. Among these, 2-Oxovaleric acid, elaidic acid, myristic acid, palmitic acid, estrone, myo-inositol showed contrasting trends of regulation in the two biofluids. Only trans-Aconitic acid and 2,4-Di-tert-butylphenol showed consistent patterns of regulation in both plasma and urine. These results illustrate the power of metabolomics in identifying potential disease-associated biomarkers and provide a foundation for further studies towards early diagnostic applications in severe heart conditions that may prevent surgery in the elderly.

Rapid quantification of ruthenium(ii) polypyridyl anti-cancer drugs using a selective ligand dissociation LC-MS/MS method.

Research on Ru anti-cancer drugs is on the rise with many complexes in clinical trials. Inductively coupled plasma-mass spectrometry (ICP-MS) has been the standard technique for bioanalytical studies on Ru and Pt complexes in biological media. Tedious ICP-MS methods rely on detecting and quantifying the element while lacking important structural information of the original complexes. Despite being equally sensitive, more accessible, and highly selective to the target species, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has not been validated for the analysis of Ru drugs. Using USFDA guidelines, we report here the optimization and validation of a facile LC-MS/MS method for the detection and quantification of three Ru(ii) polypyridyl complexes in cells, plasma, and urine matrices. Importantly, a fast (10 min), single-step procedure was efficient for both extraction and sample purification, and analytes were rapidly eluted over a 3 min simple isocratic run. Specific parent ions were differentially fragmented by tandem MS, thus forming a unique and rational ligand dissociation chemistry that exhibits high selectivity to the target species with no measurable interferences or matrix effects. The developed LC-MS/MS method was advantageous vis-à-vis the prototypical ICP-MS based techniques both in vitro and in vivo, paving the way for its utilization in elaborate cellular uptake, pharmacokinetics, and pharmacodynamics studies.

Curcumin encapsulated colloidal amphiphilic block co-polymeric nanocapsules: colloidal nanocapsules enhance photodynamic and anticancer activities of curcumin.

Curcumin-based novel colloidal nanocapsules were prepared from amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F108). These colloidal nanocapsules appeared as spherical particles with size ranging between 270 and 310 nm. Curcumin fluorescence spectra exhibited an aggregation-induced 23 nm red-shift of the emission maximum in addition to the enhancement of the fluorescence quantum yield in these nanocapsules. The cytotoxicity of curcumin and colloidal nanocapsules was assessed using human derived immortalized cell lines (A549 and A375 cells) in the presence and absence of light irradiation. The nanocapsules exhibited a >30-fold decrease in IC50, suggesting enhanced anticancer activity associated with curcumin encapsulation. Higher toxicity was also reported in the presence of light irradiation (as shown by the IC50 data), indicating their potential for future application in photodynamic therapy. Finally, A375 cells treated with curcumin and the nanocapsules showed a significant increase in single- and/or double-strand DNA breaks upon exposure to light, indicating promising biological effects.

Characterization and cytotoxicity assessment of nargile smoke using dynamic exposure.

Objectives: Nargile (waterpipe) smoking has gained popularity in the Middle East and throughout the world. In this research, a new dynamic methodology was conceived. This methodology was deployed for direct in vitro assessment of cytotoxicity, genotoxicity, and apoptotic potential of smoke generated from a single nargile session. Materials and methods: A549 cells were deployed in a designed system to assess the cytotoxicity of generated smoke. The smoke was characterized using Gas chromatography-mass spectrometry (GC-MS) profiling for major organic compounds, whereas the remaining chemical and physical parameters were tabulated from published data. The cytoxicity of smoke generated from five commercial flavored tobacco products was assessed using the (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2-H-tetrazolium) (MTS) assay. The genotoxicity was also measured using the comet assay, while apopoptosis was evaluated using Annexin V/propidium iodide staining.Results: The data indicated acute cytotoxicity emanating from smoke products in all tested tobacco flavors. Significant loss of viability and mitochondrial activity was observed 40 min post smoke exposure (Double-Apple flavored), while DNA damage onset was reported as early as 20 min of exposure. Microscopical analysis showed a systematic increase in cell rounding post exposure indicating cellular loss of adhesion and potential membrane damages. Finally, the Annexin V/propidium iodide cellular staining showed signs of late apoptosis or necrosis in exposed cells. Conclusions: The presented data clearly indicated significant in vitro cytotoxicity, genotoxicity and apoptosis/necrosis associated with a 60-min single session of nargile smoking.

Enhanced cellular uptake and photochemotherapeutic potential of a lipophilic strained Ru(ii) polypyridyl complex.

The use of ruthenium complexes as chemotherapeutic agents has been recently explored as one of the alternatives to conventional treatments. In the present study, two Ru(ii) polypyridyl complexes were synthesized and characterized: a strained [Ru(bipy)2(BC)]Cl2 (complex 1) where [bipy = 2,2'-bipyridine and BC = bathocuproine] along with the unstrained control [Ru(bipy)2(phen)]Cl2 (complex 2) where [phen = 1,10-phenanthroline]. The photophysical and photochemical analyses proved that unlike the photostable complex 2, complex 1 ejected both bipy and BC ligands at a ratio of 3 : 1 respectively. Results showed that the activity of complex 1 was significantly enhanced upon photoactivation. The response was however particularly significant in B16-F10 melanoma cells where phototoxicity index (PI = IC50 dark/IC50 light) was >900. When compared to cisplatin, the photoproducts were more potent against all tested cell lines, implying that the complex acquired significant chemotherapeutic potential upon irradiation. Cellular uptake of complex 1 and the free BC ligand were found to be significantly facilitated as evidenced by 400-600 fold increase in concentration of the compounds inside the cells relative to the extracellular culture medium. Complex 2 exhibited 35 times lower cellular concentration relative to complex 1. Flow cytometry and plasmid DNA gel electrophoresis measurements showed that complex 1 interacts with DNA inducing apoptosis in the dark and either late-apoptosis or necrosis upon irradiation. These findings corroborate the importance of lipophilic ligands such as BC to enhance uptake and subsequently improve the photochemotherapy potential of Ru(ii) polypyridyl complexes.

Municipal leachates health risks: Chemical and cytotoxicity assessment from regulated and unregulated municipal dumpsites in Lebanon.

The proper management of municipal waste is critical for resource recovery, sustainability and health. Lebanon main approach for managing its municipal waste consisted of landfill disposal with minimal recycling capacity. This approach contributed to exceeding the holding capacity of existing landfills leading eventually to their closures. The closure of a major landfill (Naameh landfill) servicing Beirut and Mount Lebanon areas led to municipal wastes piling in the streets and forests for more than a year in 2016. The main problem identified in the municipal wastes consisted of untreated leachates (from regulated and unregulated dumpsites) going straight into the Mediterranean Sea. Therefore leachate samples were collected and subjected to chemical characterization followed by biological assessment. The chemical characterization and profiling of the Lebanese leachates were compared to results reported in Lebanon, Europe and United States as well as to the toxicity reference values (TRV). The biological assessment was conducted in vitro using human derived immortalized cell cultures. This strategy revealed significant alarming cellular organelles and DNA damages using in vitro cytotoxicity assays (MTS and comet assay). The significant damages observed at the cellular level prompted further animal model investigations using BALB/c mice. The animal data pointed to significant upregulation of liver activity enzymes coupled with significant damage expression in liver spleen and bone marrow DNA. The presented research clearly indicated that there is an urgent need for development of national waste strategies for proper treatment and disposal of municipal waste leachates in Lebanon.

A long-lived cuprous bis-phenanthroline complex for the photodynamic therapy of cancer.

Copper is an earth-abundant and a biologically essential metal that offers a promising alternative to noble metals in photochemistry and photobiology. In this work, a series of sterically encumbered Cu(i) bis-phenanthroline complexes were investigated for their use in photochemotherapy (PCT). It was found that Cu(dsbtmp)2+ [dsbtmp = 2,9-disec-butyl-3,4,7,8-tetramethyl-1,10-phenanthroline] (compound 3), which possessed the longest excited state lifetime, exhibited significant in vitro photocytotoxicity on A375 (human malignant melanoma) and A549 (human lung carcinoma) cell lines. Fluorescence imaging demonstrated the significant uptake and localization of compound 3 in a perinuclear fashion. A comet assay indicated the induction of DNA damage in the dark. The DNA breaks were significantly amplified upon photoactivation. The light-induced enhancement of cytotoxicity was associated with the formation of reactive oxygen species (ROS), a known intermediate in photodynamic therapy (PDT). This successful demonstration of photocytotoxicity using long-lived cuprous phenanthroline paves the way to exploit this class of photosensitizers for PDT applications.

Phototoxicity of strained Ru(ii) complexes: is it the metal complex or the dissociating ligand?

A photochemically dissociating ligand in Ru(bpy)2(dmphen)Cl2 [bpy = 2,2'-bipyridine; dmphen = 2,9-dimethyl-1,10-phenanthroline] was found to be more cytotoxic on the ML-2 Acute Myeloid Leukemia cell line than Ru(bpy)2(H2O)22+ and prototypical cisplatin. Our findings illustrate the potential potency of diimine ligands in photoactivatable Ru(ii) complexes.

Enhanced photophysics from self-assembled cyclometalated Ir(iii) complexes in water.

Two water-soluble anionic cyclometalated Ir(iii) complexes, Ir(ppy)2BPS [] and Ir(F-mppy)2BPS [] have been synthesized and display clear evidence of self-assembly in water. Concentration-induced aggregation enhances the excited-state properties of both complexes, blue-shifting the photoluminescence emission energies as well as increasing the corresponding excited state lifetimes and quantum yields up to a factor of 5.

Homogeneous Photocatalytic H2 Production Using a RuII Bathophenanthroline Metal-to-Ligand Charge-Transfer Photosensitizer.

The prototypical [Ru(bpy)3 ]2+ (bpy=2,2'-bipyridine) photosensitizer has been previously demonstrated to be labile in aqueous photocatalytic solutions, especially in the presence of coordinating electron donors. Here, an alternative RuII molecular sensitizer, [Ru(dpp)3 ]2+ (dpp=4,7-diphenyl-1,10-phenanthroline or bathophenanthroline), is described, which is considerably more stable than its bpy congener, allowing enhanced photocatalysis metrics in conjunction with a cobalt glyoxime ([Co(dmgH)2 pyCl], dmgH=dimethylglyoxime, py=pyridine) water reduction catalyst and N,N-dimethyl-p-toluidine (DMT) as the sacrificial donor in a 1:1 mixture of CH3 CN/H2 O. Photoluminescence studies revealed that DMT reductively quenches the excited state of [Ru(dpp)3 ]2+ with a bimolecular rate constant of kq =4.9×109 m-1 s-1 . The rate constant measured for electron transfer from the reduced sensitizer to the [Co(dmgH)2 pyCl] was found to be near the diffusion limit, kCo =2.4×109 m-1 s-1 . H2 production by photocatalysis was independently monitored by using a high-throughput photochemical reactor equipped with pressure transducers, gas chromatogram, and a mass spectrometer for detection; this illustrated that the composition yields high turnover numbers (TONs), approaching 10 000 (H2 /Ru) with respect to the sensitizer and deuteration studies using D2 O confirmed that H2 is primarily produced from protons derived from water in these systems.

Homogeneous Photocatalytic H2 Production Using a RuII Bathophenanthroline Metal-to-Ligand Charge-Transfer Photosensitizer.

Invited for this month's cover are the research groups of Prof. Rony S. Khnayzer at Lebanese American University and Prof. Felix (Phil) N. Castellano at North Carolina State University. The cover picture illustrates the absorption of visible light by a ruthenium bathophenanthroline MLCT chromophore followed by a sequence of electron transfer steps that ultimately leads to the efficient production of hydrogen gas from water. Read the full text of the article at 10.1002/cplu.201600227.