Search results for "MATERIA"
showing 10 items of 33501 documents
Determining Factors for the Unfolding Pathway of Peptides, Peptoids, and Peptidic Foldamers.
2016
We present a study of the mechanical unfolding pathway of five different oligomers (α-peptide, β-peptide, δ-aromatic-peptides, α/γ-peptides, and β-peptoids), adopting stable helix conformations. Using force-probe molecular dynamics, we identify the determining structural factors for the unfolding pathways and reveal the interplay between the hydrogen bond strength and the backbone rigidity in the stabilization of their helix conformations. On the basis of their behavior, we classify the oligomers in four groups and deduce a set of rules for the prediction of the unfolding pathways of small foldamers.
Helical supramolecular polymerization of C3-symmetric amides and retroamides: on the origin of cooperativity and handedness.
2016
The cooperative supramolecular polymerization of 1 and 2 yields P- or M-type helical aggregates depending on the absolute configuration (S or R) of the stereogenic centres attached to the side chains. The connectivity of the amide group does not affect the handedness of the helical aggregates, but determines a larger cooperativity for retroamides 1.
Extending the halogen-bonded supramolecular synthon concept to 1,3,4-oxadiazole derivatives
2016
A series of five crystal structures of 1:1 halogen-bonded complexes were obtained from 4-[5-(4-alkoxyphenyl)-1,3,4-oxadiazole-2-yl]pyridine and 1,3,5-trifluorotriiodobenzene. Electronic structure calculations show that the N(oxadiazole)⋯I interaction in the new synthon is as strong as the classic N(pyridine)⋯I interaction. Oxygen to sulfur atom subsitution on the oxadiazole ring results in a different supramolecular packing where the N(pyridine)⋯I interaction is favored, which could be rationalized by the changes in the molecular electrostatic potential predicted from the theoretical calculations.
Synthesis and characterization of binuclear μ-oxalato nickel(II), copper(II) and zinc(II) complexes with 3,3′-diamino-N-methyl-dipropylamine or trans…
1999
Abstract New binuclear complexes of the type [(Ni(Medpt)NO3)2ox] (1) (Medpt=3,3′-diamino-N-methyl-dipropylamine, H2ox=oxalic acid), [(Ni(dach)2)2ox]NO3·2H2O (2) (dach=trans-1,2-diaminocyclohexane), [(Cu(Medpt))2ox]X2·yH2O (X=NO3, y=2 2/3 (3); X=ClO4, y=0 (4)) and [(Zn(dach)2)2ox](ClO4)2·2H2O (5) have been prepared and characterized by IR and UV–Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N3O3 or N4O2) Ni(II) (compounds 1 or 2), five-coordinated (N3O2) Cu(II) (compounds 3 and 4) or six-coordinated (N4O2) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))2ox](NO3)2·2 2/3 H2O (3) has been determined by single-crystal X-…
Microporous Triptycene‐Based Affinity Materials on Quartz Crystal Microbalances for Tracing of Illicit Compounds
2019
Triptycene-based organic molecules of intrinsic microporosity (OMIMs) with extended functionalized π-surfaces are excellent materials for gas sorption and separation. In this study, the affinities of triptycene-based OMIM affinity materials on 195 MHz high-fundamental-frequency quartz crystal microbalances (HFF-QCMs) for hazardous and illicit compounds such as piperonal and (-)-norephedrine were determined. Both new and existing porous triptycene-based affinity materials were investigated, resulting in very high sensitivities and selectivities that could be applied for sensing purposes. Remarkable results were found for safrole - a starting material for illicit compounds such as ecstasy. A …
Modulating the DNA cleavage ability of copper(II) Schiff bases through ternary complex formation
2018
Copper(II) complexes with the potentially tridentate Schiff bases N-[(3-ethoxy-2-hydroxyphenyl)methylidene]-N′-tosylbenzene-1,2-diamine (H2L1) and N-[(2-hydroxynaphthanyl)methylidene]-N′-tosylbenzene-1,2-diamine (H2L2) have been synthesized by electrochemical oxidation of the metal in an electrochemical cell containing a solution of the corresponding ligand in acetonitrile. Adducts of these compounds with 2,2′-bipyridine (2,2′-bpy), 4,4′-bipyridine (4,4′-bpy) or 1,10-phenanthroline (phen) were also obtained. The complexes have been characterized by microanalysis, mass spectrometry, EPR, IR and UV-Vis spectroscopies, as well as DFT calculations. The ligand H2L1 and the compounds [CuL1(H2O)]·…
Synthesis of new terpyridine-like ligands based on triazolopyridines and benzotriazoles
2017
Herein, terpyridine triazole-based analogs bearing benzotriazoles or/and triazolopyridines are prepared via copper catalysis, where the arrangement of the nitrogen atoms is proven to be crucial to the spectroscopic properties of these ligands.
Highly antiproliferative neutral Ru(ii)-arene phosphine complexes
2018
Six ruthenium(II)- and four gold(I)-phosphine based complexes were synthesized and fully characterized. Some of them displayed strong antiproliferative properties for several types of cancer including colon, breast, and lung. Notably, two of the Ru(II) complexes displayed an IC50 of around 2 μM, which is exceptional for these types of complexes. The dramatic impact of the nature of the arene coordinated on the ruthenium center was clearly evidenced.
Magneto-structural correlations in asymmetric oxalato-bridged dicopper(II) complexes with polymethyl-substituted pyrazole ligands
2018
Two oxalato-bridged dinuclear copper(II) complexes, [{Cu(Hdmpz)3}2(μ-ox)](ClO4)2·2H2O (1) and [{Cu(Htmpz)3}2(μ-ox)](ClO4)2·2H2O (2) (Hdmpz = 3,5-dimethyl-1H-pyrazole and Htmpz = 3,4,5-trimethyl-1H-pyrazole), have been synthesized and structurally and magnetically characterized. The crystal structures of 1 and 2 consist of asymmetric bis-bidentate μ-oxalatodicopper(II) complex cations with two short [Cu–O = 1.976(2) (1) and 1.973(2) Å (2)] and two long copper–oxygen bonds [Cu–O = 2.122(2) (1) and 2.110(2) Å (2)]. The environment at each CuII ion in 1 and 2 is closer to the trigonal bipyramidal geometry than to the square pyramidal [τ = 0.633 (1) and 0.711 (2)]. The magnetic properties of 1 a…
Synthesis, crystal structure and magnetic properties of the cyclic tetranuclear compound [Cu4(pz)4(hppa)2(H2O)4] [pz = pyrazolate; hppa = R,S-2-hydro…
2019
Abstract The synthesis, X-ray structure and magnetic properties of the neutral tetranuclear copper(II) complex of formula [Cu4(pz)4(hppa)2(H2O)4] (1) [Hpz = pyrazole and hppa = R,S-2-hydroxo-2-phenyl-2-(1-pyrazolyl)acetate] are reported. Remarkably, the structure of 1 reveals the presence of the S- and R-forms of the new hppa ligand which is formed in situ in the complex reaction between copper(II), pyrazole and phenylmalonate in water:methanol solvent mixture under ambient conditions. The two crystallographically independent copper(II) ions [Cu(1)/Cu(2)] are five-coordinate in square pyramidal surroundings. Three nitrogen atoms, from two pz groups and one hppa ligand and one oxygen atom of…