Gated photochromism and acidity photomodulation of a diacid dithienylethene dye

The present study quantitatively analyses the gated photochromism and the acidity photomodulation properties of a diacid dithienylethene compound. Photoisomerisation between the open and closed isomers was investigated by UV/visible and (1)H NMR spectroscopy. It was found that the photocyclisation quantum yield of the diacid form was remarkably high (around 90%). Partial neutralisation of the open isomer revealed a gated photochromism as the photocyclisation quantum yield of the mono- and dianion were 50 and 67%, respectively. A considerable photomodulation of the acidity was observed: the closed isomer is more acid than the open one by more than one pK(a) unit. This effect has been shown to be exploitable for a reversible photo-acid generation. This is the first time that a complete quantitative investigation that allows for the determination of the main photochromic, spectral and thermodynamic parameters of a base-sensitive photochromic diarylethene has been carried out.     

Ruthenium complexes with non-innocent ligands: Electron distribution and implications for catalysis

Ruthenium complexes with the non-innocent ligands (NILs) benzoquinone, iminobenzoquinone and benzoquinonediimine and their redox derivatives exhibit intriguing electronic properties. With the proper ligand set the NIL π* orbitals mix extensively with the ruthenium dπ orbitals resulting in delocalized electron distributions and non-integer oxidation states, and in most of these systems a particular ruthenium oxidation state dominates. This review critically examines the electronic structure of Ru–NIL systems from both an experimental and computational (DFT) perspective. The electron distribution within these complexes can be modulated by altering both the ancillary ligands and the NIL, and in a few cases the resultant electron distributions are exploited for catalysis. The Ru–NIL systems that perform alcohol oxidation and water oxidation catalysis are discussed in detail. The Tanaka catalyst, an anthracene-bridged dinuclear Ru complex, is an intriguing example of a Ru–NIL framework in catalysis. Unlike other known ruthenium water oxidation catalysts, the two Ru atoms remain low valent during the catalytic cycle according to DFT calculations, some experimental evidence, and predictions based on the behavior of the related mononuclear species.     

Synthesis and Crystal Structure of a New Heterotrinuclear Schiff-Base Zn–Gd Complex

Abstract  

A heterotrinuclear Zn–Gd complex [GdZn₂L₂(OAc)₂](CF₃SO₃) (1) based on the salphen Schiff-base ligand bis(3-methoxysalicylidene)-1,2-phenylenediamine (H₂L) was synthesized and characterized by single crystal X-ray diffraction. The structure was solved in the triclinic space group P − 1 with a = 9.4743(19), b = 16.333(3), c = 19.291(4) ?, α = 88.89(3), β = 78.16(2), γ = 76.69(3)°, V = 2842.0(10) ?³, Z = 2, D _c  = 1.610 g/cm³, F (000) = 1,386, R ₁ = 0.0458, and wR ₂ = 0.1239. In the solid state short intermolecular O···H–C hydrogen bonding, π–π stacking, and H···π interactions between neighboring [GdZn₂L₂(OAc)₂]⁺ moieties generate a porous 3D-framework architecture with extended channels running along the a-axis.     

Transformation d'halphen

We give a modern version of the following result of Halphen: “degrees and classes of successive evolutes of a plane algebraic curve form two arithmetic progressions of the same ratio after a sufficient number of iterations”. The iteration of this transform provides a desingularisationprocess (branch by branch) of plane curves, different to the Nash transform and the Noether process. To prove these two points,we introduce systematically Puiseux's exponents, semi-groups of exponents and use elimination and duality formulae.     

Beginning Secondary Science Teachers' Conceptualization and Enactment of Inquiry‐Based Instruction

This study investigates the conceptions and use of inquiry during classroom instruction among beginning secondary science teachers. The 44 participants were beginning secondary science teachers in their first year of teaching. In order to capture the participants' conceptions of inquiry, the teachers were interviewed and observed during the school year. The interviews consisted of questions about inquiry instruction, while the observations documented the teachers' use of inquiry. All of the interviews were transcribed or coded in order to understand the conceptions of inquiry held by the teachers, and all of the observations were analyzed in order to determine the presence of inquiry during the lesson. The standard for assessing inquiry came from the National Science Education Standards. A quantitative analysis of the data indicated that the teachers frequently talked about implementing “scientific questions” and giving “priority to evidence.” This study found a consistency between the way new teachers talked about inquiry and the way they practiced it in their classrooms. Overall, our observations and interviews revealed that the beginning secondary science teachers tended to enact teacher‐centered forms of inquiry, and could benefit from induction programs focused on inquiry instruction.     

Optimization of Sample Preparation for Metabolomics Exploration of Urine,Feces, Blood and Saliva in Humans Using Combined NMR and UHPLC-HRMS Platforms

Currently, most clinical studies in metabolomics only consider a single type of sample such as urine, plasma, or feces and use a single analytical platform, either NMR or MS. Although some studies have already investigated metabolomics data from multiple fluids, the information is limited to a unique analytical platform. On the other hand, clinical studies investigating the human metabolome that combine multi-analytical platforms have focused on a single biofluid. Combining data from multiple sample types for one patient using a multimodal analytical approach (NMR and MS) should extend the metabolome coverage. Pre-analytical and analytical phases are time consuming. These steps need to be improved in order to move into clinical studies that deal with a large number of patient samples. Our study describes a standard operating procedure for biological specimens (urine, blood, saliva, and feces) using multiple platforms (¹H-NMR, RP-UHPLC-MS, and HILIC-UHPLC-MS). Each sample type follows a unique sample preparation procedure for analysis on a multi-platform basis. Our method was evaluated for its robustness and was able to generate a representative metabolic map.     

MATHSMAPS FOR DIAGNOSTIC ASSESSMENT WITH PRE-SERVICE TEACHERS: STORIES OF MATHEMATICAL KNOWLEDGE

This paper reports an innovative assessment feedback tool - the mathsmap - and describes how two pre-service teachers made sense of this personalised diagnostic map to reflect on their own subject knowledge in mathematics. The mathsmap provided both a summative and a diagnostic profile of their attainment and errors across the mathematics curriculum required for teacher training. The use of the mathsmap to reflect learning on a personal level is seen to also provoke 'accounts' or 'stories' that might inform pedagogical content knowledge: in making their mathsmap comprehensible to themselves, the teachers needed to account for their own knowledge-troubles, that is, to narrate their metacognition.     

Identification of isoenzymes using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The identification of isoforms is one of the great challenges in proteomics due to the large number of identical amino acids preventing their separations by two-dimensional electrophoresis. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has become a rapid and sensitive tool in proteomics, notably with the new instrumental improvements. In this study, we used several acquisition modes of MALDI-TOFMS to identify isoforms of porcine glutathiones S-transferase. The use of multiple proteases coupled to the different acquisition modes of MALDI-TOFMS (linear, reflectron, post-source decay (PSD) and in-source decay, positive and negative modes) allowed the identification of two sequences. Moreover, a third sequence is pointed out from a PSD study of a tryptic ion revealing the modification of the amino acid tyrosine 146 to phenylalanine.     

Interplay of p-sulfonatocalix[4]arene and crown ethers en route to molecular capsules and "Russian dolls"

Diffusion-ordered (1)H NMR spectroscopy techniques have been used to determine the binding strength of p-sulfonatocalix[4]arene (SO(3)[4]) towards a number of charged crown ether species in aqueous conditions. For several (doubly) charged (di)azacrown ethers, all were bound by SO(3)[4] either well or very well with binding constants between 5.1 x 10(2)-9.9 x 10(5) M(-1). These results correlate with, and thus explain the phenomenon of rapid capture of azacrown ethers in molecular capsules based on p-sulfonatocalix[4]arene and lanthanide metals. Similarly, the formation of "Russian doll" superanions in the solution phase is also elucidated. These superanions have been shown to selectively crystallise particular polynuclear aquated metal ions from mixtures in the aqueous phase. Neutral [18]crown-6 is not bound by p-sulfonatocalix[4]arene and displays a binding constant of 0 M(-1). When sodium [18]crown-6 is examined in a similar fashion, binding by SO(3)[4] is observed in solution with K(a) approximately 3.1 x 10(3) M(-1).