Effects of axial coordination on the Ru−Ru single bond in diruthenium paddlewheel complexes

The 1,8-naphthyridine-based (NP-based) ligands with furyl, thiazolyl, pyridyl, and pyrrolyl attachments at the 2-position have been synthesized. Reactions of 3-MeNP (3-methyl-1,8-naphthyridine), fuNP (2-(2-furyl)-1,8-naphthyridine), tzNP (2-(2-thiazolyl)-1,8-naphthyridine), pyNP (2-(2-pyridyl)-1,8-naphthyridine), and prNP- (2-(2-pyrrolyl)-1,8-naphthyridine) with [Ru2(CO)4(CH3CN)6]2+ lead to [Ru2(3-MeNP)2(CO)4(OTf)2] (1), [Ru2(fuNP)2(CO)4]2[BF4]2 (2), [Ru2(tzNP)2(CO)4][ClO4]2 (3), [Ru2(pyNP)2(CO)4][OTf]2 (4), and [Ru2(prNP)2(CO)4] (5). The molecular structures of complexes 1−5 have been established by X-ray crystallographic studies. The modulation of the Ru−Ru single-bond distances with axial donors triflates, furyls, thiazolyls, pyridyls, and pyrrolyls has been examined. A small and gradual increase in the Ru−Ru distance is measured with various donors of increasing strengths. The shortest Ru−Ru distance of 2.6071(9) Å is observed for the axially coordinated triflates in complex 1, and the longest Ru−Ru distance of 2.6969(10) Å is measured for axial pyrrolyls in complex 5. The Ru−Ru distances in complexes 3 (2.6734(7) Å) and 4 (2.6792(9) Å), having thiazolyls and pyridyls at axial sites respectively, are similar. The Ru−Ru distance for axial furyls in complex 2 (2.6261(9) Å) is significantly shorter than the corresponding distances in 3, 4, and 5. DFT calculations provide insight into the interaction of the Ru−Ru σ orbital with axial donors. The Ru−Ru σ orbital is elevated to a higher energy because of the interaction with axial lone pairs. The degree of destabilization depends on the nature of axial ligands:  the stronger the ligand, higher the elevation of Ru−Ru σ orbital. The lengthening of Ru−Ru distances with respect to the axial donors in compounds 1−5 follows along the direction pyrrolyl > pyridyl ≈ thiazolyl > furyl > triflate, and the trend correlates well with the computed destabilization of the Ru−Ru σ orbitals

Novel heterobimetallic metallamacrocycles based on the 1,1‘-bis(1,8-naphthyrid-2-yl)ferrocene (FcNP2) ligand: structural characterization of the complexes [{M(FcNP<SUB>2</SUB>)}<SUB>2</SUB>]<SUP>2+</SUP>(M = Cu<SUP>I</SUP>, Ag<SUP>I</SUP>) and {MCl<SUB>2</SUB>(FcNP<SUB>2</SUB>)}<SUB>4</SUB>(M = Zn<SUP>II</SUP>, Co<SUP>II</SUP>)

Self-assembly reactions of 1,1'-bis(1,8-naphthyrid-2-yl)ferrocene (FcNP2) with CuI/AgI afford dimeric [{CuI/AgI(FcNP2)}2]2+ and with ZnCl2/CoCl2 yield tetrameric metallamacrocycles {ZnII/CoIICl2(FcNP2)}4

Microbial Diversity of Source and Point-of-Use Water in Rural Haiti – A Pyrosequencing-Based Metagenomic Survey

<div><p>Haiti endures the poorest water and sanitation infrastructure in the Western Hemisphere, where waterborne diseases cause significant morbidity and mortality. Most of these diseases are reported to be caused by waterborne pathogens. In this study, we examined the overall bacterial diversity of selected source and point-of-use water from rural areas in Central Plateau, Haiti using pyrosequencing of 16s rRNA genes. Taxonomic composition of water samples revealed an abundance of Firmicutes phyla, followed by Proteobacteria and Bacteroidetes. A total of 38 bacterial families and 60 genera were identified. The presence of several <i>Klebsiella</i> spp. (tentatively, <i>K</i>. <i>pneumoniae</i>, <i>K</i>. <i>variicola</i> and other <i>Klebsiella</i> spp.) was detected in most water samples. Several other human pathogens such as <i>Aeromonas</i>, <i>Bacillus</i>, <i>Clostridium</i>, and <i>Yersinia</i> constituted significantly higher proportion of bacterial communities in the point-of-use water samples compared to source water. Bacterial genera traditionally associated with biofilm formation, such as <i>Chryseobacterium</i>, <i>Fusobacterium</i>, <i>Prevotella</i>, <i>Pseudomonas</i> were found in the point-of-use waters obtained from water filters or domestic water storage containers. Although the pyrosequencing method utilized in this study did not reveal the viability status of these pathogens, the abundance of genetic footprints of the pathogens in water samples indicate the probable risk of bacterial transmission to humans. Therefore, the importance of appropriate handling, purification, and treatment of the source water needed to be clearly communicated to the communities in rural Haiti to ensure the water is safe for their daily use and intake.</p></div

Genera listed are significantly different between the groups.

<p>Genera listed are significantly different between the groups.</p

Taxa depleted or introduced in point-of-use water with respect to corresponding source water.

<p>Taxa depleted or introduced in point-of-use water with respect to corresponding source water.</p

Relative abundance of bacterial diversity in source and point-of-use water samples at phylum level as determined by bTEFAP^®.

<p>Relative abundance of bacterial diversity in source and point-of-use water samples at phylum level as determined by bTEFAP^®.</p

Rarefaction curves showing observed taxonomic units of bacterial species diversity in the source and point-of-use water samples.

<p>Rarefaction curves showing observed taxonomic units of bacterial species diversity in the source and point-of-use water samples.</p

Relative abundance of bacterial families residing in source and point-of-use water samples as determined by bTEFAP^®.

<p>Multi-colored stack bar graphs represent the relative abundance of bacterial family in each sample.</p

Dual Hierarchal dendrogram evaluation of the taxonomic classification of source and point-of-use water samples.

<p>Samples are clustered on the X-axis and labeled based upon the water source types. Samples with more similar microbial populations are mathematically clustered closer together. The genera (consortium) are used for clustering. Thus the samples with more similar consortium of bacterial genera cluster closer together with the length of connecting lines (top of heatmap) related to the similarity, shorter lines between two samples indicate closely matched bacterial consortium. The heatmap represents the relative percentages of each bacterial genus. The predominant genera are represented along the right Y-axis. The legend for the heatmap is provided in the upper left corner.</p

PCoA analysis of the microbiome of each water sample based upon UniFrac method.

<p>Different colored symbols are indicative of the different major source and point-of-use water samples. Symbols that are closer together represent similar bacterial community compositions.</p