Selective Formation of Unsymmetric Multidentate Azine-Based Ligands in Nickel(II) Complexes

A mixture of 2-pyridine carboxaldehyde, 4-formylimidazole (or 2-methyl-4-formylimidazole), and NiCl2 center dot 6H(2)O in a molar ratio of 2:2:1 was reacted with two equivalents of hydrazine monohydrate in methanol, followed by the addition of aqueous NH4PF6 solution, afforded a Ni-II complex with two unsymmetric azine-based ligands, [Ni(HLH)(2)](PF6)(2) (1) or [Ni(HLMe)(2)](PF6)(2) (2), in a high yield, where HLH denotes 2-pyridylmethylidenehydrazono-(4-imidazolyl)methane and HLMe is its 2-methyl-4-imidazolyl derivative. The spectroscopic measurements and elemental analysis confirmed the phase purity of the bulk products, and the single-crystal X-ray analysis revealed the molecular and crystal structures of the Ni-II complexes bearing an unsymmetric HLH or HLMe azines in a tridentate kappa(3) N, N', N" coordination mode. The HLH complex with a methanol solvent, 1 center dot MeOH, crystallizes in the orthorhombic non-centrosymmetric space group P2(1)2(1)2(1) with Z = 4, affording conglomerate crystals, while the HLMe complex, 2 center dot H2O center dot Et2O, crystallizes in the monoclinic and centrosymmetric space group P2(1)/n with Z = 4. In the crystal of 2 center dot H2O center dot Et2O, there is intermolecular hydrogen-bonding interaction between the imidazole N-H and the neighboring uncoordinated azine-N atom, forming a one-dimensional polymeric structure, but there is no obvious magnetic interaction among the intra- and interchain paramagnetic Ni-II ions

Transition-metal(ii) complexes with a tripodal hexadentate ligand, 1,1,1-tris[2-aza-3-(imidazol-4-yl)prop-2-enyl]ethane, exhibiting incomplete total or absolute spontaneous resolution

Crystal structures and crystallisation behaviours of a series of first-row transition-metal(II) complexes bearing 1,1,1-tris[2-aza-3-(imidazol-4-yl)prop-2-enyl]ethane (H3L), [MII(H3L)]Cl(ClO4) (M = Mn, Fe, Co, Ni and Zn) were examined. These compounds crystallise in an orthorhombic crystal system with a non-enantiogenic (Sohncke) space group P212121, resulting in spontaneous resolution of the chiral complex cations. Hydrogen bonds between the imidazole N–H atoms in the tripodal ligand and chloride anions give enantiomorphic crystals with a homochiral three-dimensional network structure. In order to verify the spontaneous resolution of these compounds, solid-state circular dichroism spectra of the resulting single crystals were measured (KBr disk method). Unexpectedly, the observed spectra indicated that imbalanced formation of the enantiomorphic crystals (i.e., left-handed Λ-form vs. right-handed Δ-form complex cations) in all cases. Moreover, in the cases of NiII and ZnII compounds, predominant enantiomorphic crystals formed by spontaneous resolution were always the same (in at least ten of our recrystallisation experiments). These observations suggest that there is a certain (but as yet unknown) factor that affects the predominant deposition of either enantiomorphic crystal when spontaneous resolution takes place from a solution of a racemic mixture in which rapid racemisation occurs

Defining the latent phase of labour: is it important?

Background and rationale. The latent phase of labour is recognised as a period of uncertainty for women and midwives. There is evidence from the literature of considerable variation in labour definitions and practice. Stimulated by discussion at an international maternity research conference, the authors set out to explore opinions regarding the need for labour-stage definitions.  Aim. To identify health professionals’ views on the need for a definition of the onset and the end of the latent phase of labour.  Methods. This was an opportunistic, semi-structured, online survey of attendees at a maternity care research conference, which included midwives, other clinicians, academics, advocates and user representatives. Attendees (approximately 100) were invited to participate through a single email invitation sent by the conference committee and containing a link to the survey. Consent was sought on the landing page. Ethical approval was obtained from Bournemouth University’s research ethics committee. Quantitative questions were analysed using simple descriptive statistics using IBM SPSS Statistics Version 24. Open questions were analysed using content analysis and where participants gave a more detailed answer, these were analysed using a thematic approach.  Findings. Participants in the survey (n=21) came from 12 countries. Most of the participants thought that there was a need to define the onset of the latent phase (n=15, 71%). Common characteristics were cited, but the main theme in the open comments referred to the importance of women’s perceptions of labour onset. Most participants (n = 18, 86%) thought that there was a need to define the end of the latent phase. This was felt necessary because current practice within facilities is usually dictated by a definition. The characteristics suggested were also not unexpected and there was some consensus; but the degree of cervical dilatation that signified the end of the latent phase varied among participants. There was significant debate about whether a prolonged latent phase was important; for example, was it associated with adverse consequences. Most participants thought it was important (n=15, 71%), but comments indicated that the reasons for this were complex. Themes included the value that women attached to knowing the duration of labour and the need to support women in the latent phase.  Implications for practice. The findings from this small, opportunistic survey reflect the current debate within the maternal health community regarding the latent phase of labour. There is a need for more clarity around latent phase labour (in terms of both the definition and the support offered) if midwives are to provide care that is both woman centred and evidence-based. The findings will inform the development of a larger survey to explore attitudes towards labour definitions

trans-Dichloridotetrakis(pyridine-κN)rhodium(III) chloride methanol tetrasolvate

In the solvated title salt, [RhCl2(C5H5N)4]Cl·4CH3OH, the RhIII atom lies on a special position of 2.22 site symmetry. Consequently, the cationic complex has molecular D2 symmetry with a trans disposition for two equivalent Cl− and four equivalent pyridine ligands. The Rh—Cl and Rh—N bond lengths are 2.3452 (7) and 2.064 (2) Å, respectively. The planes of the coordinating pyridine ligands are tilted synchronously, with a dihedral angle of 40.76 (9)° between the least-squares pyridine plane and the coordination plane defined by the RhIII and four pyridine N atoms. The chloride counter-anion is located on a crystallographic \overline{4}.. site, and is surrounded by four methanol molecules to which it is bound in a pseudo-tetrahedral arrangement by O—H...Cl hydrogen bonds

Synthesis and characterization of iron(II) complex with unsymmetrical heterocyclic (2-pyridyl)(4-imidazolyl)azine

A new iron(II) complex bearing unsymmetrical azine, [Fe(HLH)2](PF6)2·H2O·MeCN (HLH = 2-pyridylmethylidenehydrazono(4-imidazolyl)methane), was synthesized exclusively by a reaction of 2-pyridine carboxaldehyde, 1H-imidazole-4-carboxaldehyde, hydrazine monohydrate and FeCl2·4H2O (in a molar ratio of 2:2:2:1) in methanol, followed by the addition of an aqueous NH4PF6 solution. It was characterized using spectroscopic techniques, elemental analysis, magnetic measurement, and cyclic voltammetry. The molecular and crystal structure of the compound was revealed by X-ray analysis, where an iron(II) ion was surrounded by two HLH azines with a planar E(py),Z(im) conformation, and tridentate κ3N,N’,N” coordination mode, forming a monomeric six-coordinated and diamagnetic complex. The complex cations were linked by water molecules via intermolecular hydrogen-bonding interactions between the imidazole N−H and the neighboring uncoordinated azine-N atom, forming a 1D chain structure. The selective formation of this unsymmetrical azine (HLH) from a stoichiometric mixture of the components would result from the steric preference of the five- and six-membered chelate rings by the 2-pyridyl and 4-imidazolyl azine moieties, respectively, with the E(py),Z(im) configuration

Structural comparison of geometrical isomers of N'-(1H-imidazol-4-ylmethylene)picolinohydrazide and their mononuclear and dinuclear cobalt(III) complexes

The crystal structures and spectroscopic properties of both E- and Z-isomers of N'-(1H-imidazol-4-ylmethylene)-picolinohydrazide (H2Lim) were investigated. In addition, an aerobic reaction of H2Lim with Co(BF4)2 in methanol afforded a mononuclear cobalt(III) complex, [Co(Z-HLim)2]BF4 (1) bearing tridentate hydrazonate ligands, and a dinuclear complex of [Co2(μ-E-HLim)3](BF4)3 (2), where the hydrazonate bridged two CoIII centers in the μ-κ2N,N': κ2N'',N''' mode to form an C3-symmetry triple helicate complex

Four-Electron Oxidative Dehydrogenation Induced by Proton-Coupled Electron Transfer in Ruthenium(III) Complex with 2‑(1,4,5,6-Tetrahydropyrimidin-2-yl)phenolate

New ruthenium­(II or III) complexes with general formula [Ru­(O-N)­(bpy)₂]^<i>n</i>+ (O-N = unsymmetrical bidentate phenolate ligand; bpy = 2,2′-bipyridine) were synthesized, and their crystal structures and electrochemical properties were characterized. Ru^II complexes with 2-(2-imidazolinyl)­phenolate (Himn^–) or 2-(1,4,5,6-tetrahydropyrimidin-2-yl)­phenolate (Hthp^–) could be deprotonated by addition of excess KO^<i>t</i>Bu, although the deprotonated species were easily reprotonated by exposure to air. Unlike these Ru^II complexes, their Ru^III analogs showed interesting ligand oxidation reactions upon addition of bases. With [Ru^III(Himn)­(bpy)₂]²⁺, two-electron oxidation of Himn^– and reduction of the Ru^III center resulted in conversion of the 2-imidazolinyl group to a 2-imidazolyl group. On the other hand, the corresponding Hthp^– complex exhibited four-electron oxidation of the ligand to form 2-(2-pyrimidyl)­phenolate (pym^–). These aromatization reactions of imidazolinyl and 1,4,5,6-tetrahydropyrimidyl groups were also achieved by the electrochemically generated Ru^III complexes

Four-Electron Oxidative Dehydrogenation Induced by Proton-Coupled Electron Transfer in Ruthenium(III) Complex with 2‑(1,4,5,6-Tetrahydropyrimidin-2-yl)phenolate

New ruthenium­(II or III) complexes with general formula [Ru­(O-N)­(bpy)₂]^<i>n</i>+ (O-N = unsymmetrical bidentate phenolate ligand; bpy = 2,2′-bipyridine) were synthesized, and their crystal structures and electrochemical properties were characterized. Ru^II complexes with 2-(2-imidazolinyl)­phenolate (Himn^–) or 2-(1,4,5,6-tetrahydropyrimidin-2-yl)­phenolate (Hthp^–) could be deprotonated by addition of excess KO^<i>t</i>Bu, although the deprotonated species were easily reprotonated by exposure to air. Unlike these Ru^II complexes, their Ru^III analogs showed interesting ligand oxidation reactions upon addition of bases. With [Ru^III(Himn)­(bpy)₂]²⁺, two-electron oxidation of Himn^– and reduction of the Ru^III center resulted in conversion of the 2-imidazolinyl group to a 2-imidazolyl group. On the other hand, the corresponding Hthp^– complex exhibited four-electron oxidation of the ligand to form 2-(2-pyrimidyl)­phenolate (pym^–). These aromatization reactions of imidazolinyl and 1,4,5,6-tetrahydropyrimidyl groups were also achieved by the electrochemically generated Ru^III complexes