The influence of anion-pi interactions between multi-atomic anions and pi-acidic ring systems on the self-assembly of coordination compounds

Anion-π interactions, weak attractions between anions and π-acidic ring systems, have become an important topic in supramolecular chemistry within the past five years. Although a variety of computational studies have been undertaken by several groups to investigate the nature of these interactions, no comprehensive experimental investigations had been performed until the completion of the work described herein. The results presented in this dissertation indicate that anion-π interactions involving large complex anions are controlling elements in self-assembly reactions with cations that involve π-acidic ring systems. Syntheses performed with the ligand 3-6-bis(2’-pyridyl)-1,2,4,5-tetrazine, or bptz, with M(II) first row transition metal salts (M = Mn, Fe, Ni, Cu, and Zn), produced self-assembled complexes that varied in shape and M:ligand ratio based on the presence of particular anions. Through a series of solution and structural studies, it was determined that the cationic polygons are templated by the size and shape of the specific anions during self-assembly. A close inspection of the bptz complexes in the solid state indicated that the anions were participating in anion-π interactions with the π-acidic central tetrazine ring of the ligand. To show that these anion-π interactions were indeed important, reactions of bptz ligand as well with 3,6-bis(2’-pyridyl)-1,2-pyridazine (bppn) with Ag(I) salts were performed to compare the effect that specific anions had on self-assembly interactions between similar ligands with different π-acidities. The results indicate that the Ag(I) complexes that included the π-acidic tetrazine ring are strongly influenced by the anion presence, while those complexes that were synthesized with the similarly shaped, but electroneutral bppn ligand only relied on the anions for charge-balance. To better understand the anion-π interactions in the obtained bptz complexes, a computational study was performed on systems with the polyatomic anions [BF4]- and [PF6]- interacting with simple heteroaromatic rings of varying degrees of π-acidity. Based on the final optimized complex geometries and Atoms in Molecules (AIM) critical point analyses, it was determined that anion-π interactions involving multiatomic anions interact with π-systems in different orientations based on the symmetry of the ring system in the complex

Dynamics of biofilm re-growth in drinking water distributions systems

The majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics with findings demonstrating patterns of material accumulation, seasonality and influential factors. Rigorous flushing operations repeated over a one-year period on an operational, chlorinated system in the UK are presented. Intensive monitoring and sampling were undertaken including time series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. Results show bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to chlorine residual, this suggests that limiting inorganic nutrients, other than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, thus also a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimise asset performance. IMPORTANCE: This research provides with novel information regarding dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimise the performance of the distribution network and to guarantee safe and good quality drinking water to consumers

Bis(2,2′-bipyridine){ethyl 4′-[N-(4-carbamoylphen­yl)carbamo­yl]-2,2′-bi­pyridine-4-carboxyl­ate}ruthenium(II) bis­[hexa­fluorido­phosphate(V)]

In the title compound, [Ru(C10H8N2)2(C21H18N4O4)](PF6)2, the RuII complex cation reveals a slightly distorted octa­hedral coordination. The coordination bonds of the 4,4′-substituted bipyridyl donors [Ru—N = 2.038 (3) and 2.051 (3) Å] are shorter than those of the 2,2′-bipyridyl donors [Ru—N1 = 2.065 (3)–2.077 (3) Å], due to the electron-withdrawing effects of the substituents at the 4,4′-positions. The angles between the pyridyl planes of the three bipyridyl ligands are 1.5 (2), 6.3 (3) and 8.7 (2)°, respectively. The cations are connected by anions via N—H⋯F inter­actions

Abstrahlverhalten einer transienten Funkenstrecke - Ein grundlegender Versuch zur EMV-Abschätzung

Es wurde ein Versuchsaufbau vorgestellt, mit dem eine transiente Funkenstrecke reproduzierbar erzeugt und ihr Abstrahlverhalten gemessen werden kann. Wesentlicher Bestandteil der Vermessung des Magnetfeldes ist dabei die Kalibrierung einer geeigneten Magnetfeld-Schnüffelsonde mit Anwendung auf Transienten. Mit diesem grundlegenden Versuch konnte eine einfache rechnerische Abschätzung für Magnetfelder, die durch eine solche Funkenstrecke erzeugt werden, verifiziert werden. Die Abschätzungen sind dabei unterteilt in einen quasistationären und einen gestrahlten Term, welche je nach Frequenzbereich Anwendung finden sollten. Weiterhin zu untersuchen bleiben Variationen der Funkenstrecke, beispielswiese bezüglich der Anstiegszeiten des Stromes I(t) und dem Abstand der Elektroden. Denkbar wäre auch eine Erweiterung der rechnerischen Abschätzung mit dem Skalarpotenzial unter Berücksichtigung der gemessenen Elektrodenspannung. Interessant ist sicherlich auch eine Charakterisierung der raum- und zeitvarianten Funkenentladung selbst mit Hilfe von High-Speed-Kameras. Einige Arbeiten am Institut für Hochspannungstechnik und Elektrische Energieanlagen sind diesbezüglich durchaus vielversprechend und könnten zur Verfeinerung von rechnerischen Abschätzungen beitragen

A thorough anion-π interaction study in biomolecules:On the importance of cooperativity effects

Noncovalent interactions have a constitutive role in the science of intermolecular relationships, particularly those involving aromatic rings such as π-π and cation-π. In recent years, anion-π contact has also been recognized as a noncovalent bonding interaction with important implications in chemical processes. Yet, its involvement in biological processes has been scarcely reported. Herein we present a large-scale PDB analysis of the occurrence of anion-π interactions in proteins and nucleic acids. In addition we have gone a step further by considering the existence of cooperativity effects through the inclusion of a second noncovalent interaction, i.e. π-stacking, T-shaped, or cation-π interactions to form anion-π-π and anion-π-cation triads. The statistical analysis of the thousands of identified interactions reveals striking selectivities and subtle cooperativity effects among the anions, π-systems, and cations in a biological context. The reported results stress the importance of anion-π interactions and the cooperativity that arises from ternary contacts in key biological processes, such as protein folding and function and nucleic acids-protein and protein-protein recognition. We include examples of anion-π interactions and triads putatively involved in enzymatic catalysis, epigenetic gene regulation, antigen-antibody recognition, and protein dimerization

What factors increase revision surgery risk when treating displaced femoral neck fractures with arthroplasty: a secondary analysis of the HEALTH trial

Objectives: HEALTH was a randomized controlled trial comparing total hip arthroplasty with hemiarthroplasty in low-energy displaced femoral neck fracture patients aged >= 50 years with unplanned revision surgery within 24 months of the initial procedure being the primary outcome. No significant short-term differences between treatment arms were observed. The primary objective of this secondary HEALTH trial analysis was to determine if any patient and surgical factors were associated with increased risk of revision surgery within 24 months after hip fracture. Methods: We analyzed 9 potential factors chosen a priori that could be associated with revision surgery. The factors included age, body mass index, major comorbidities, independent ambulation, type of surgical approach, length of operation, use of femoral cement, femoral head size, and degree of femoral stem offset. Our statistical analysis was a multivariable Cox regression using reoperation within 24 months of index surgery as the dependent variable. Results: Of the 1441 patients included in this analysis, 8.1% (117/1441) experienced reoperation within 24 months. None of the studied factors were found to be predictors of revision surgery (P > 0.05). Conclusion: Both total and partial hip replacements are successful procedures in low-energy displaced femoral neck fracture patients. We were unable to identify any patient or surgeon-controlled factors that significantly increased the need for revision surgery in our elderly and predominately female patient population. One should not generalize our findings to an active physiologically younger femoral neck fracture population.Orthopaedics, Trauma Surgery and Rehabilitatio

The FAITH and HEALTH Trials: Are We Studying Different Hip Fracture Patient Populations?

BACKGROUND: Over the past decade, 2 randomized controlled trials were performed to evaluate 2 surgical strategies (internal fixation and arthroplasty) for the treatment of low-energy femoral neck fractures in patients aged ≥50 years. We evaluated whether patient populations in both the FAITH and HEALTH trials had different baseline characteristics and compared the displaced femoral neck fracture cohort from the FAITH trial to HEALTH trial patients. METHODS: Patient demographics, medical comorbidities, and fracture characteristics from both trials were compared. FAITH trial patients with displaced fractures were then compared with HEALTH patients. T-tests and χ tests were performed to compare differences for sex, age, osteoporosis status, and ASA class. RESULTS: The mean age of the 1079 FAITH trial patients was 72 versus 79 years for the 1441 HEALTH trial patients. HEALTH patients were older, mostly White, used more medication, and had more comorbidities than FAITH patients. Of the 1079 FAITH trial patients, 32% (346/1079) had displaced fractures. Their mean age was significantly lower than that of HEALTH patients (66 vs. 79 years; P < 0.001). HEALTH trial patients were significantly more likely to be female, have ASA classification Class III/IV/V, and carry a diagnosis of osteoporosis, as compared with the subgroup of FAITH patients with displaced femoral neck fractures (P < 0.001). CONCLUSION: This study demonstrates significant differences between patients enrolled in the 2 trials. Although both studies focused on femoral neck fractures with similar enrollment criteria, patient

Observations of tetrel bonding between sp3-carbon and THF

We report the direct observation of tetrel bonding interactions between $sp^{3}$-carbons of the supramolecular synthon 3,3-dimethyl-tetracyanocyclopropane (1) and tetrahydrofuran in the gas and crystalline phase. The intermolecular contact is established via σ-holes and is driven mainly by electrostatic forces. The complex manifests distinct binding geometries when captured in the crystalline phase and in the gas phase. We elucidate these binding trends using complementary gas phase quantum chemical calculations and find a total binding energy of −11.2 kcal mol$^{−1}$ for the adduct. Our observations pave the way for novel strategies to engineer $sp^{3}$-C centred non-covalent bonding schemes for supramolecular chemistry

What Factors Increase Revision Surgery Risk When Treating Displaced Femoral Neck Fractures With Arthroplasty: A Secondary Analysis of the HEALTH Trial

OBJECTIVES: HEALTH was a randomized controlled trial comparing total hip arthroplasty with hemiarthroplasty in low-energy displaced femoral neck fracture patients aged ≥50 years with unplanned revision surgery within 24 months of the initial procedure being the primary outcome. No significant short-term differences between treatment arms were observed. The primary objective of this secondary HEALTH trial analysis was to determine if any patient and surgical factors were associated with increased risk of revision surgery within 24 months after hip fracture. METHODS: We analyzed 9 potential factors chosen a priori that could be associated with revision surgery. The factors included age, body mass index, major comorbidities, independent ambulation, type of surgical approach, length of operation, use of femoral cement, femoral head size, and degree of femoral stem offset. Our statistical analysis was a multivariable Cox regression using reoperation within 24 months of index surgery as the dependent variable. RESULTS: Of the 1441 patients included in this analysis, 8.1% (117/1441) experienced reoperation within 24 months. None of the studied factors were found to be predictors of revision surgery (P > 0.05). CONCLUSION: Both total and partial hip replacements are successful procedures in low-energy displaced femoral neck fracture patients. We were unable to identify any patient or surgeon-controlled factors that significantly increased the need for revision surgery in our elderly and predominately female patient population. One should not generalize our findings to an active physiologically younger femoral neck fracture population. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence