Syntheses, Structures, and Electronic and Optical Properties of Platinum(II) Complexes of 1,3-Bis(imino)benzene-Derived Pincer Ligands

Six new Pt^II complexes of 5-substituted 1,3-bis­(<i>N</i>-methylimino)­benzene (bIBH)-derived ligands have been synthesized by direct reactions with K₂Pt^IICl₄ in glacial acetic acid. The ethenylene groups in the two styryl-substituted complexes undergo <i>E</i>–<i>Z</i> photoisomerization, as revealed by ¹H NMR spectroscopy. The UV–vis spectra of the styryl-/aryl-substituted complexes show intense high-energy bands due to ligand-based π → π* transitions and a number of weaker bands at lower energies in the 300–500 nm region. Time-dependent density functional theory (TD-DFT) calculations indicate that the latter absorptions have mixed intraligand π → π* and Pt­(d) → π* metal-to-ligand charge-transfer (MLCT) character. Four of the new complexes give vibronically structured emission profiles in fluid solution at room temperature. The luminescence quantum yields and lifetimes in nondegassed dichloromethane are in the ranges 0.1–0.2% and 159–170 ns, respectively. In contrast, the styryl-substituted complexes are nonemissive, due to excited-state quenching by <i>E</i> → <i>Z</i> isomerization. DFT indicates that the emissive triplet state has mixed ligand-to-ligand charge-transfer and MLCT character, with a geometry distorted with respect to the symmetric ground state. Single-crystal X-ray structures have been determined for two of the complexes, showing N–Pt–N angles of ca. 159°. The complex of an unsubstituted bIB^– ligand is deep red and forms columns with short Pt···Pt distances of ca. 3.55 Å, indicating weak intermetallic interactions

Syntheses, Structures, and Electronic and Optical Properties of Platinum(II) Complexes of 1,3-Bis(imino)benzene-Derived Pincer Ligands

Six new Pt^II complexes of 5-substituted 1,3-bis­(<i>N</i>-methylimino)­benzene (bIBH)-derived ligands have been synthesized by direct reactions with K₂Pt^IICl₄ in glacial acetic acid. The ethenylene groups in the two styryl-substituted complexes undergo <i>E</i>–<i>Z</i> photoisomerization, as revealed by ¹H NMR spectroscopy. The UV–vis spectra of the styryl-/aryl-substituted complexes show intense high-energy bands due to ligand-based π → π* transitions and a number of weaker bands at lower energies in the 300–500 nm region. Time-dependent density functional theory (TD-DFT) calculations indicate that the latter absorptions have mixed intraligand π → π* and Pt­(d) → π* metal-to-ligand charge-transfer (MLCT) character. Four of the new complexes give vibronically structured emission profiles in fluid solution at room temperature. The luminescence quantum yields and lifetimes in nondegassed dichloromethane are in the ranges 0.1–0.2% and 159–170 ns, respectively. In contrast, the styryl-substituted complexes are nonemissive, due to excited-state quenching by <i>E</i> → <i>Z</i> isomerization. DFT indicates that the emissive triplet state has mixed ligand-to-ligand charge-transfer and MLCT character, with a geometry distorted with respect to the symmetric ground state. Single-crystal X-ray structures have been determined for two of the complexes, showing N–Pt–N angles of ca. 159°. The complex of an unsubstituted bIB^– ligand is deep red and forms columns with short Pt···Pt distances of ca. 3.55 Å, indicating weak intermetallic interactions

A Single-Source Precursor Route to Unusual PbSe Nanostructures by a Solution–Liquid–Solid Method

PbSe nanowires (NWs) have been synthesized by using a single-source precursor route. Carefully controlling the conditions of individual reactions leads to PbSe NWs with well-defined diameters (8–25 nm) and lengths (100 nm–1 μm). The as-grown PbSe NWs are highly crystalline, defect free, and readily dispersible in organic solvents. The NWs have been characterized by X-ray diffraction and high-resolution transmission electron microscopy

Additional file 1: of The impact on healthcare, policy and practice from 36 multi-project research programmes: findings from two reviews

Literature search strategies for the two reviews. (PDF 242 kb

A Single-Source Precursor Route to Unusual PbSe Nanostructures by a Solution–Liquid–Solid Method

PbSe nanowires (NWs) have been synthesized by using a single-source precursor route. Carefully controlling the conditions of individual reactions leads to PbSe NWs with well-defined diameters (8–25 nm) and lengths (100 nm–1 μm). The as-grown PbSe NWs are highly crystalline, defect free, and readily dispersible in organic solvents. The NWs have been characterized by X-ray diffraction and high-resolution transmission electron microscopy

Pratiques d'élevage et stratégies paysannes sur le front pionnier de la transamazonienne

Depuis la fin des années 60, la frontière pénètre les immenses espaces forestiers de l'Amazonie sur quasiment tout son pourtour. On peut parler de véritable construction de nouveaux territoires par une société pionnière qui aménage son espace au lieu et place des écosystèmes naturels préexistants. Le seul rythme de près de 1% par an de l'Amazonie annuellement transformé fait de ce processus un enjeu international. Aussi, un des grands défis est la mise en oeuvre d'une colonisation écologiquement et socialement acceptable qui passera, d'un point de vue agricole, par l'élaboration et la mise en place de systèmes de production durables. Le travail présenté dans ce mémoire s'inscrit dans le cadre d'un programme de Recherche-Développement coordonné par le CIRAD, l'EMBRAPA Amazônia Oriental et l'Université Fédérale du Parà. L'objectif scientifique et didactique de cette recherche est de tester l'analyse systémique des pratiques d'élevage dans le contexte particulier d'un front pionnier amazonien, c'est-à-dire dans une situation complexe, en particulier dans des conditions relativement extrêmes en termes de rapidité et de soudaineté des évolutions. L'analyse des pratiques d'élevage a ainsi permis de dégager les principales fonctions du troupeau dans les systèmes de production développés par l'agriculture familiale, elle ne permet cependant pas d'aboutir à l'élaboration de typologies satisfaisantes, chaque cas ou presque étant un cas particulier. Il ressort toutefois une caractéristique commune aux systèmes de production familiaux, à savoir leur caractère extrêmement adaptatif au contexte local et régional. Parallèlement, cette recherche contribue au montage du corps méthodologique d'un projet d'appui à la production laitière dans l'agriculture familiale amazonienne comportant des actions de formation, de développement et de recherche. (Résumé d'auteur

Additional file 3: of Using systematic reviews to inform NIHR HTA trial planning and design: a retrospective cohort

Justification for first-in-class trials. (PDF 19 kb

Left-Handed Helical Preference in an Achiral Peptide Chain Is Induced by an l‑Amino Acid in an N‑Terminal Type II β‑Turn

Oligomers of the achiral amino acid Aib adopt helical conformations in which the screw-sense may be controlled by a single N-terminal residue. Using crystallographic and NMR techniques, we show that the left- or right-handed sense of helical induction arises from the nature of the β-turn at the N terminus: the tertiary amino acid l-Val induces a left-handed type II β-turn in both the solid state and in solution, while the corresponding quaternary amino acid l-α-methylvaline induces a right-handed type III β-turn

Left-Handed Helical Preference in an Achiral Peptide Chain Is Induced by an l‑Amino Acid in an N‑Terminal Type II β‑Turn

Oligomers of the achiral amino acid Aib adopt helical conformations in which the screw-sense may be controlled by a single N-terminal residue. Using crystallographic and NMR techniques, we show that the left- or right-handed sense of helical induction arises from the nature of the β-turn at the N terminus: the tertiary amino acid l-Val induces a left-handed type II β-turn in both the solid state and in solution, while the corresponding quaternary amino acid l-α-methylvaline induces a right-handed type III β-turn

A role for DNA hypomethylation and histone acetylation in maintaining allele-specific expression of mouse NKG2A in developing and mature NK cells.

The repertoire of receptors that is expressed by NK cells is critical for their ability to kill virally infected or transformed cells. However, the molecular mechanisms that determine whether and when NK receptor genes are transcribed during hemopoiesis remain unclear. In this study, we show that hypomethylation of a CpG-rich region in the mouse NKG2A gene is associated with transcription of NKG2A in ex vivo NK cells and NK cell lines. This observation was extended to various developmental stages of NK cells sorted from bone marrow, in which we demonstrate that the CpGs are methylated in the NKG2A-negative stages (hemopoietic stem cells, NK progenitors, and NKG2A-negative NK cells), and hypomethylated specifically in the NKG2A-positive NK cells. Furthermore, we provide evidence that DNA methylation is important in maintaining the allele-specific expression of NKG2A. Finally, we show that acetylated histones are associated with the CpG-rich region in NKG2A positive, but not negative, cell lines, and that treatment with the histone deacetylase inhibitor trichostatin A alone is sufficient to induce NKG2A expression. Treatment with the methyltransferase inhibitor 5-azacytidine only is insufficient to induce transcription, but cotreatment with both drugs resulted in a significantly greater induction, suggesting a cooperative role for DNA methylation and histone acetylation status in regulating gene expression. These results enhance our understanding of the formation and maintenance of NK receptor repertoires in developing and mature NK cells