Search results for "ta116"
showing 10 items of 942 documents
Synthesis of Globular Precursors
2015
o-Carborane (C2 B10 H12 ) was adapted to perform as the core of globular macromolecules, dendrons or dendrimers. To meet this objective, precisely defined substitution patterns of terminal olefin groups on the carborane framework were subjected to Heck cross-coupling reactions or hydroboration leading to hydroxyl terminated arms. These led to new terminal groups (chloro, bromo, and tosyl leaving groups, organic acid, and azide) that permitted ester production, click chemistry, and oxonium ring opening to be performed as examples of reactions that demonstrate the wide possibilities of the globular icosahedral carboranes to produce new dendritic or dendrimer-like structures. Polyanionic speci…
Dynamic Stabilization of the Ligand-Metal Interface in Atomically Precise Gold Nanoclusters Au68 and Au144 Protected by meta-Mercaptobenzoic Acid
2017
Ligand-stabilized, atomically precise gold nanoclusters with a metal core of a uniform size of just 1–3 nm constitute an interesting class of nanomaterials with versatile possibilities for applications due to their size-dependent properties and modifiable ligand layers. The key to extending the usability of the clusters in applications is to understand the chemical bonding in the ligand layer as a function of cluster size and ligand structure. Previously, it has been shown that monodispersed gold nanoclusters, stabilized by meta-mercaptobenzoic acid (m-MBA or 3-MBA) ligands and with sizes of 68–144 gold atoms, show ambient stability. Here we show that a combination of nuclear magnetic reson…
Building natural science learning through youth science camps
2018
This study focuses on a youth science camp for pupils in sixth to ninth grades that is organized annually by the University of Jyväskylä, Finland. The main idea of the science camp is to learn to do guided inquiry in nature. The study investigates the significance of science camp for encouraging young participants to learn science and how the camp supports their learning. The research method used was a survey. Altogether, 47 youth participated in the camp in 2012 and 2013. The results show that the participants wanted to learn more about science than secondary school could offer, and science camp had a positive impact on their interest in science. It was possible to introduce important conc…
Achieving Strong Positive Cooperativity through Activating Weak Non-Covalent Interactions
2018
Positive cooperativity achieved through activating weak non-covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new molecular tubes have been synthesized and the syn isomer binds DABCO-based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion-pairing interactions. The X-ray single-crystal structure revealed that the strong positive cooperativity likely originates from eight C-H⋅⋅⋅O hydrogen bonds between the two head-to-head-arranged syn tube molecules. Thes…
Concerted Halogen-Bonded Networks with N-Alkyl Ammonium Resorcinarene Bromides: From Dimeric Dumbbell to Capsular Architectures
2015
N-Alkyl ammonium resorcinarene bromides and 1,4-diiodooctafluorobutane via multiple intermolecular halogen bonds (XB) form different exotic supramolecular architectures through subtle changes of the upper rim substituents. Dimeric dumbbell-like assembly with encapsulated guest molecules is generated with N-benzyl substituents. The N-hexyl groups engender an XB-induced polymeric pseudocapsule and an XB-induced dimeric capsule with entrapped 1,4-dioxane guest molecules. The N-propyl and N-cyclohexyl groups generate deep cavity cavitands. The deep cavity cavitands possess cavities for self-inclusion leading to polymeric herringbone arrangement in one direction and that pack into 3D polymeric a…
Ion Pair Binding in the Solid-State with Ditopic Crown Ether Uranyl Salophen Receptors
2016
Two ditopic uranyl salophen receptors with benzo-15-crown-5 and benzo-18-crown-6 units (R(1) and R(2), respectively) have been synthesized from commercially available starting materials. Comprehensive studies on the solid-state ion pair complexation with various alkali and ammonium halides have been conducted. From the 19 obtained solid-state structures (6 structures with R(1), 13 structures with R(2)), three general interaction motifs I-III have been observed. Interaction motif I has a separated ion pair with the cation coordinated to the crown ether unit, and the anion or oxygen containing solvent molecule coordinated to the uranyl center. The interaction motif II manifests a polymeric st…
Assembly and dichroism of a four-component halogen-bonded metal-organic cocrystal salt solvate involving dicyanoaurate(I) acceptors
2017
We describe the use of dicyanoaurate ions as linear ditopic metal–organic acceptors for the halogen bond-driven assembly of a dichroic metal–organic cocrystal based on azobenzene chromophores. Structural analysis by single crystal X-ray diffraction revealed that the material is a four-component solid, consisting of anticipated anionic metal–organic halogen-bonded chains based on dicyanoaurate ions, as well as complex potassium-based cations and discrete molecules of the crown ether 15-crown-5. Importantly, the structural analysis revealed the parallel alignment of the halogen-bonded chains required for dichroic behaviour, confirming that crystal engineering principles developed for the desi…
Ion pair complexes and anion binding in the solution of a ditopic receptor.
2016
The synthesis and crystal structures with alkali halides of a ditopic benzo-15-crown-5 bis-urea receptor have been presented. In addition, the anion binding properties of and its alkali metal complexes in solution are presented. A comprehensive single-crystal X-ray crystallographic study of , all together 13 crystal structures, including the ion pair complexes with NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, and RbI, give a detailed view of how behaves in the solid-state with different alkali halides depending on the size of the cation and anion. In the solid-state forms a 1 : 1 complex with a sodium cation and the anion is complexed as a contact (NaCl) or a separate ion pair (NaBr, NaI).…
Zirconocene-Based Methods for the Preparation of BN-Indenes : Application to the Synthesis of 1,5-Dibora-4a,8a-diaza-1,2,3,5,6,7-hexaaryl-4,8-dimethy…
2017
A method for the preparation of 3-bora-9aza-indene heterocycles based on zirconocene mediated functionalization of the ortho-CH bonds of pyridines has been developed and used to make two such compounds. Unlike other methods, the boron center in these heterocycles remains functionalized with a chloride ligand and so the compounds can be further elaborated through halide abstraction and reduction. The utility of the method was further demonstrated by applying it towards the preparation of 1,5- dibora-4a,8a-diaza BN analogues of the intriguing hydrocarbon s-indacene starting from 2,5-dimethylpyrazine. Gram quantities of one such compound was prepared and fully characterized, and both experimen…
Synthesis and characterization of chiral phosphirane derivatives of [(μ-H)4Ru4(CO)12] and their application in the hydrogenation of an α,β-unsaturate…
2017
Abstract Ruthenium clusters containing the chiral binaphthyl-derived mono-phosphiranes [(S)-([1,1′-binaphthalen]-2-yl)phosphirane] (S)-1a, [(R)-(2′-methoxy-1,1′-binaphthyl-2-yl)phosphirane] (R)-1b, and the diphosphirane [2,2′-di(phosphiran-1-yl)-1,1′-binaphthalene] (S)-1c have been synthesized and characterized. The clusters are [(μ-H)4Ru4(CO)11((S)-1a)] (S)-2, [(μ-H)4Ru4(CO)11((R)-1b)] (R)-3, 1,1-[(μ-H)4Ru4(CO)10((S)-1c)] (S)-4, [(μ-H)4Ru4(CO)11((S)-binaphthyl-P(s)(H)Et)] (S,Sp)-5, [(μ-H)4Ru4(CO)11((S)-binaphthyl-P(R)(H)Et)] (S,Rp)-6, [(μ-H)4Ru4(CO)11((R)-binaphthyl-P(s)(H)Et)] (R,Sp)-7, [(μ-H)4Ru4(CO)11((R)-binaphthyl-P(R)(H)Et)] (R,Rp)-8 and the phosphinidene-capped triruthenium cluster …