Search results for "yhdisteet"
showing 10 items of 326 documents
Transition path selection between ammonium nitrate solid phases IV, III and II
1994
Article dissertation. Contains an introduction and five articles. This study was made of factors affecting the transition paths between ammonium nitrate solid state phases IV, III and II. The effect of the sample preparation method was investigated by differential scanning calorimetry (DSC), transition mechanisms were explored with simultaneous DSC and Raman spectrometry developed for in situ investigation of the transitions, and the relationship between phase IV structure and the transition paths was studies by X-ray powder diffraction (XRD) and DSC. The results were analysed by partial least-squares regression (PLS) and principal component analysis (PCA). [Continues; please see the book]
Testing the effectiveness of pyrazine defences against spiders
2020
Insects live in a dangerous world and may fall prey to a wide variety of predators, encompassing multiple taxa. As a result, selection may favour defences that are effective against multiple predator types, or target-specific defences that can reduce predation risk from particular groups of predators. Given the variation in sensory systems and hunting tactics, in particular between vertebrate and invertebrate predators, it is not always clear whether defences, such as chemical defences, that are effective against one group will be so against another. Despite this, the majority of research to date has focused on the role of a single predator species when considering the evolution of defended…
Molecular and supramolecular structures of self-assembled Cu(II) and Co(II) complexes with 4,4’-[6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4-…
2020
The molecular and supramolecular structures of [Cu(PTM)Cl2]*0.75MeOH (1), [Co(PTM)Cl2]; (2A) and [Co(PTM)Cl2(EtOH)]; (2B) complexes, where PTM is 4,4’-[6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4-diyl]dimorpholine, were presented. In complexes 1 and 2A, the Cu(II) and Co(II) are tetra-coordinated with a distorted tetrahedral coordination environment. In case of complex 2B, an additional ethanol molecule is found coordinated with Co(II) leading to a highly distorted penta-coordinated Co(II) complex. In all cases, the PTM ligand is acting as a bidentate NN-chelate. Hirshfeld surface analysis indicated the importance of H⋯H (49.0–55.1%), Cl⋯H (18.8–20.5%) and O⋯H (8.3–9.9%) contacts in…
Titanocene Selenide Sulfides Revisited: Formation, Stabilities, and NMR Spectroscopic Properties
2019
[TiCp2S5] (phase A), [TiCp2Se5] (phase F), and five solid solutions of mixed titanocene selenide sulfides [TiCp2SexS5−x] (Cp = C5H5−) with the initial Se:S ranging from 1:4 to 4:1 (phases B–E) were prepared by reduction of elemental sulfur or selenium or their mixtures by lithium triethylhydridoborate in thf followed by the treatment with titanocene dichloride [TiCp2Cl2]. Their 77Se and 13C NMR spectra were recorded from the CS2 solution. The definite assignment of the 77Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the 77Se chemical shifts and is supported by 13C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS2 solutions of …
1,2,6-Thiadiazine 1-Oxides: Unsaturated Three-Dimensional S,N-Heterocycles from Sulfonimidamides.
2020
Unprecedented three-dimensional 1,2,6-thiadiazine 1-oxides have been prepared by an aza-Michael-addition/cyclization/condensation reaction sequence starting from sulfonimidamides and propargyl ketones. The products have been further functionalized by standard cross-coupling reactions, selective bromination of the heterocyclic ring, and conversion into a β-hydroxy substituted derivative. A representative product was characterized by single-crystal X-ray structure analysis. peerReviewed
Self-assembly of M4L4 tetrahedral cages incorporating pendant P=S and P=Se functionalised ligands
2019
Herein, the synthesis of metal–organic tetrahedral cages featuring flexible thio- and selenophosphate-based ligands is described. The cages were prepared by sub-component self-assembly of A=P(OC6H4NH2-4)3 (A = S, Se) or S=P(SC6H4NH2-4)3,2-pyridinecarboxaldehyde, and either Fe[BF4]2 or Co[BF4]2. Preliminary host–guest studies into the ability of the pendant PQS and PQSe groups to interact with suitable substrates will be discussed. peerReviewed
Organocatalytic Oxa-Michael/Michael/Michael/Aldol Condensation Quadruple Domino Sequence : Asymmetric Synthesis of Tricyclic Chromanes
2018
An efficient and highly stereoselective one-pot, four-component synthesis of functionalized tricyclic chromanes has been achieved through an organocatalyzed quadruple domino reaction. The reaction sequence involves an oxa-Michael/Michael/Michael/aldol condensation between alcohols, 2 equiv of acrolein, and nitrochromenes to generate the pharmaceutically important tricyclic chromanes bearing three contiguous stereogenic centers including a chiral tetrasubstituted carbon center in good domino yields (30–70%) and excellent diastereo- and enantioselectivities (>20:1 dr and >99% ee). peerReviewed
Thiazyl radicals and their derivatives
2017
Tiatsyylit ovat orgaanisia radikaaleja, joilla on samanlaisia fysikaalisia ominaisuuksia, joita tavallisesti esiintyy epäorgaanisilla yhdisteillä ja metallioksideilla. Tiatsyylien sähköä johtavat ja magneettiset ominaisuudet ovat kiinnittäneet huomiota niiden löytymisestä lähtien ja niitä on hyödynnetty molekulaaristen magneettien ja johteiden suunnittelussa. Tämän lisäksi tietyillä tiatsyyleillä esiintyy bistabiilisuutta, joka tarkoittaa, että radikaalilla on kaksi erilaista magneettista olomuotoa riippuen kiinteän tilan pakkautumisesta. Bistabiilisuutta voidaan hyödyntää esimerkiksi molekyylikytkimissä. Uusin tutkimuksen haara on tiatsyylien koordinoiminen siirtymämetalleihin, joka lisää …
Carboxylate catalyzed isomerization of β,γ‐unsaturated N-acetylcysteamine thioesters
2022
We demonstrate herein the capacity of simple carboxylate salts – tetrametylammonium and tetramethylguanidinium pivalate – to act as catalysts in the isomerization of β,γ-unsaturated thioesters to α,β-unsaturated thioesters. The carboxylate catalysts gave reaction rates comparable to those obtained with DBU, but with fewer side reactions. The reaction exhibits a normal secondary kinetic isotope effect ( k 1H / k 1D = 1.065±0.026) with a β,γ−deuterated substrate. Computational analysis of the mechanism provides a similar value ( k 1H / k 1D = 1.05) with a mechanism where γ-reprotonation of the enolate intermediate is rate determining. peerReviewed
The Synthesis of Quinoline‐based Tin Complexes with Pendant Schiff Bases
2019
Whilst pursuing the synthetic utility of quinoline‐based tin complexes, Me2Sn(Quin‐NO2)2 (1) and Ph2Sn(Quin‐NO2)2 (2) (Quin‐NO2 = 5‐nitroquinolino‐8‐oate) were synthesized bearing coordinatively inert nitro groups. Conventional reduction methodologies successfully converted 1 to Me2Sn(Quin‐NH2)2 (3) and 2 to Ph2Sn(Quin‐NH2)2 (4) (Quin‐NH2 = 5‐aminoquinolino‐8‐oate). The synthetically useful amine groups proved difficult to exploit in the presence of the central tin atom, however, a complete Schiff base functionalized Sn complex of the dimethyltin pro‐ligand Me2Sn(Quin‐py)2 (6) was successfully synthesized from 5‐[(pyridin‐2‐ylmethylene)amino]quinolin‐8‐ol (HQuin‐py; 5) in good yield via an …