Halogen bonding, chalcogen bonding, pnictogen bonding, tetrel bonding: origins, current status and discussion

The role of the closing lecture in a Faraday Discussion is to summarise the contributions made to the Discussion over the course of the meeting and in so doing capture the main themes that have arisen. This article is based upon my Closing Remarks Lecture at the 203(rd) Faraday Discussion meeting on Halogen Bonding in Supramolecular and Solid State Chemistry, held in Ottawa, Canada, on 10-12(th) July, 2017. The Discussion included papers on fundamentals and applications of halogen bonding in the solid state and solution phase. Analogous interactions involving main group elements outside group 17 were also examined. In the closing lecture and in this article these contributions have been grouped into the four themes: (a) fundamentals, (b) beyond the halogen bond, (c) characterisation, and (d) applications. The lecture and paper also include a short reflection on past work that has a bearing on the Discussion

In Their Own Words: Healing from Traumatic Childbirth

Trauma related to childbirth is seldom addressed despite the incidence of women who experience traumatic births. Birth trauma, like other traumatic events, can have a lasting impact on women and can effect their attachment to their infants. This study gives voice to women\u27s birth trauma and describes what women find helpful in their healing processes from traumatic birth. This study is based on the narratives of 14 women who graciously shared their birth stories and healing journeys in semi-structured qualitative interviews. Their traumatic birth experiences occurred 3 ½ to 26 years ago. A post-positivist approach and narrative theory informed this study. This research found that participants experienced a discordance of expectations and realities of childbirth, a juxtaposition of emotions and experiences, identified specific aspects that were healing/helpful and other aspects that were hurtful/unhelpful during pregnancy, labor, birth, delivery, and beyond. In the healing process from traumatic childbirth, the specific aspects women identified as being healing and helpful were being heard/listened to, having supportive people in their lives, taking action, having reparative experiences, relying on their faith and spirituality, and creating and telling their birth stories. This research study also found that women who developed a coherent narrative of their traumatic childbirth experiences were more likely to divide their narrative episodically, tell their narrative with a continuous and smooth flow, and had more developed self-evaluations and meanings with regards to their experiences. Implications include care providers across disciplines being knowledgeable of birth trauma and its effects and providing appropriate support and referrals to women who experience birth trauma. It is recommended that care providers assist women with understanding their birth experiences and for social workers and counselors to support women in creating their coherent narratives of their traumatic childbirth experiences as part of their healing processes

Highly selective detection of Hg2+ and MeHgI by di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine and its zinc coordination polymer

©2016 the Partner Organisations. Solvothermal reaction of Zn(NO3)2·6H2O with di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine (ppvppa) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) in H2O and MeCN at 150 °C yielded a two-dimensional (2D) coordination Zn(ii) polymer [Zn(ppvppa)(1,4-NDC)]n (1). Compound 1 was characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 consists of dimeric [Zn2(ppvppa)2] units linked by 1,4-NDC bridges to generate a 2D honeycomb network. Either compound 1 or ppvppa alone can detect Hg2+ or MeHgI selectively and with good sensitivity. Upon addition of Hg2+ ions to a MeCN solution of ppvppa, marked changes in the UV-vis and fluorescence spectra are observed, associated with colour changes, which are easily identified by the naked eye. The pyridinyl rings of ppvppa are coordinated to the Hg2+ ion. This motif in the presence of NO3- ions forms a binuclear complex [Hg2(ppvppa)2(NO3)4] (2), which has been characterized as the solvate [Hg2(ppvppa)2(NO3)4]·H2O·4MeCN (2·H2O·4MeCN) by single-crystal X-ray diffraction studies. In aqueous solution, compound 1 emits pale orange light at ambient temperature and the addition of Hg2+ or MeHgI induces an change of fluorescence color from pale orange to blue. Compound 1 is a promising candidate as a sensitive naked-eye indicator for Hg2+ or MeHgI in water under a UV lamp. Introduction to the international collaboration Prof. Lang and Prof. Brammer met with each other in Nanjing, China when Prof. Brammer taught lectures at Nanjing Tech University last November. Prof. Lang's research involves metal sulfide cluster chemistry, design and development of new coordination complex-based catalysts, bioinorganic chemistry related to mimicking metal sites of enzymes and proteins, and so on. Prof. Brammer's research interest covers supramolecular chemistry and crystal engineering, in particular host-guest chemistry and catalysis in metal-organic frameworks, reactions in molecular solids and fundamentals of intermolecular interactions. Both professors recognised their many mutual research interests and decided to initiate an international collaborative project in the area of coordination polymers. Both will visit the partner's lab in China and UK in the near future and expand this project to a higher level

A solvent-resistant halogen bond

The effect of solvent on the stabilities of complexes involving a single H-bond or halogen-bond (X-bond) has been quantified. Association constants for binary complexes of 4-(phenylazo)phenol, molecular iodine, tetramethylurea and tetramethylthiourea have been measured in fifteen different solvents by UV/vis absorption and 1H NMR titration experiments. The stabilities of the H-bonded complexes decrease by more than three orders of magnitude with increasing solvent polarity. In contrast, the X-bonded complex of molecular iodine with tetramethylthiourea is remarkably insensitive to the nature of the solvent (association constants measured in alkanes and alcohols are similar). The results suggest that, in contrast to H-bonds, where electrostatics determine thermodynamic stability, charge-transfer interactions make a major contribution to the stability of these X-bonded complexes rendering them resistant to increases in solvent polarity

Similaridade genética em acessos de Aegilops tauschii, Triticum durum e híbridos interespecíficos.

bitstream/CNPT-2010/40330/1/p-bp57.pd

Análise citogenética quanto à viabilidade polínica em triticale.

Editores técnicos: Joseani Mesquita Antunes, Ana Lídia Variani Bonato, Márcia Barrocas Moreira Pimentel

The assembly of "normal" galaxies at z=7 probed by ALMA

We report new deep ALMA observations aimed at investigating the [CII]158um line and continuum emission in three spectroscopically confirmed Lyman Break Galaxies at 6.8<z<7.1, i.e. well within the re-ionization epoch. With Star Formation Rates of SFR ~ 5-15 Msun/yr these systems are much more representative of the high-z galaxy population than other systems targeted in the past by millimeter observations. For the galaxy with the deepest observation we detect [CII] emission at redshift z=7.107, fully consistent with the Lyalpha redshift, but spatially offset by 0.7" (4 kpc) from the optical emission. At the location of the optical emission, tracing both the Lyalpha line and the far-UV continuum, no [CII] emission is detected in any of the three galaxies, with 3sigma upper limits significantly lower than the [CII] emission observed in lower reshift galaxies. These results suggest that molecular clouds in the central parts of primordial galaxies are rapidly disrupted by stellar feedback. As a result, [CII] emission mostly arises from more external accreting/satellite clumps of neutral gas. These findings are in agreement with recent models of galaxy formation. Thermal far-infrared continuum is not detected in any of the three galaxies. However, the upper limits on the infrared-to-UV emission ratio do not exceed those derived in metal- and dust-poor galaxies.Comment: 15 pages, 9 figures, MNRAS in press, replaced with accepted versio

Solvent-switchable continuous-breathing behaviour in a diamondoid metal–organic framework and its influence on CO2 versus CH4 selectivity

Understanding the behaviour of flexible metal–organic frameworks (MOFs)—porous crystalline materials that undergo a structural change upon exposure to an external stimulus—underpins their design as responsive materials for specific applications, such as gas separation, molecular sensing, catalysis and drug delivery. Reversible transformations of a MOF between open- and closed-pore forms—a behaviour known as ‘breathing’—typically occur through well-defined crystallographic transitions. By contrast, continuous breathing is rare, and detailed characterization has remained very limited. Here we report a continuous-breathing mechanism that was studied by single-crystal diffraction in a MOF with a diamondoid network, (Me2NH2)[In(ABDC)2] (ABDC, 2-aminobenzene-1,4-dicarboxylate). Desolvation of the MOF in two different solvents leads to two polymorphic activated forms with very different pore openings, markedly different gas-adsorption capacities and different CO2 versus CH4 selectivities. Partial desolvation introduces a gating pressure associated with CO2 adsorption, which shows that the framework can also undergo a combination of stepped and continuous breathing

Tetra­kis[μ-N,N′-bis­(4-bromo­phen­yl)formamidinato-κ2 N:N′]dimolyb­denum(II) tetra­hydro­furan solvate

The title complex, [Mo2(C13H9N2Br2)4]·C4H8O, contains a quadruply bonded Mo2 4+ unit equatorially coordinated by four N,N′-bis­(4-bromo­phen­yl)formamidinate ligands, forming a dimetal paddlewheel complex. The centroid of the Mo—Mo bond is located on a special position with 2/m symmetry. In the crystal, complex mol­ecules are linked by Br⋯Br inter­actions [3.7049 (10) Å]. The disordered solvent mol­ecule could not be satisfactorily modelled and was therefore eliminated from the final refinement

Sustainable procurement practice in the public sector: An international comparative study

Public procurement is a significant and yet understudied phenomenon. In light of debates concerning the transparency of public procurement, growing interest in sustainable public procurement as a means to stimulate corporate social responsibility in the private sector, and concerns regarding the competitive impacts of public procurement policies, we explore sustainable procurement practice internationally. In particular, we report the findings of a survey of sustainable procurement practices within a sample of over 280 public procurement practitioners from 20 countries and with collective responsibility for expenditure totalling $45bn. Building upon a conceptual model that emphasises the importance of national policy environments regarding sustainable procurement mediated by a range of organisational contextual factors, our analysis shows that a wide range of sustainable procurement practices are embedded to some degree in public sector procurement practice around the world and that the extent and nature of sustainable procurement practices varies significantly across countries