Search results for "Stack"
showing 10 items of 392 documents
Porphyrin-Polymer Networks, Worms, and Nanorods: pH-triggerable Hierarchical Self-assembly
2011
In this study, we present a novel, multifaceted pH-triggerable system of self-organized hierarchical nanostructures. The system consists of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and poly(2-vinylpyridine) cylindrical brushes (PVP brushes) and can yield polymer-porphyrin networks, porphyrin loaded polymer brushes and pure porphyrin nanorods. In addition, the polymer influences the pK(a) and the mutual TPPS stacking geometry. Structures were characterized by AFM, dynamic light scattering using an IR laser, UV-Vis spectroscopy and small-angle neutron scattering (SANS). Supramolecular composite porphyrin structures that can be switched through external triggers have potential in photo…
7-Amino-2-methylsulfanyl-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxylic acid as the dimethylformamide and water monosolvates at 293 K.
2010
The molecular structure of 7-amino-2-methylsulfanyl-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxylic acid is reported in two crystal environments, viz. as the dimethylformamide (DMF) monosolvate, C(7)H(7)N(5)O(2)S·C(3)H(7)NO, (I), and as the monohydrate, C(7)H(7)N(5)O(2)S·H(2)O, (II), both at 293 (2) K. The triazolo[1,5-a]pyrimidine molecule is of interest with respect to the possible biological activity of its coordination compounds. While the DMF solvate exhibits a layered structural arrangement through N...O hydrogen-bonding interactions, the monohydrate displays a network of intermolecular O...O and N...O hydrogen bonds assisted by cocrystallized water molecules and weak π-π stacking intera…
B-DNA Structure and Stability as Function of Nucleic Acid Composition. Dispersion-Corrected DFT Study of Dinucleoside-Monophosphate Single and Double…
2013
actions of the sugar-phosphate skeleton with water; (6) hydrophobic interactions of the DNA cylindrical core, made up by the hydrogen-bonded and stacked nitrogen bases, with the water solvent. Recently, there has been increasing effort in developing and applying quantum chemical methods able to reproduce the structure of native B-DNA and to correctly describe the energy involved in the intrastrand and interstrand noncovalent interactions between the nucleotide monomers. This topic has been approached by both wave function methods and density functional theory. [2] Water solvent and sodium counterions also play an important role in the formation and relative stabilization of the double-helic…
Receptors for Nucleotides
2012
Recognition and activation of nucleotides by polyammonium receptors constitute an important target in supramolecular chemistry since the very beginning of this field. Nucleotides have three components: (i) the polyphosphate chain, (ii) the sugar moiety, and (iii) the nucleobase, which permit their multipoint binding through attractions between opposite charges, hydrogen bonding, π-stacking, CH–π interactions, and so on. In this chapter, different receptors for nucleotides, most but not all of them consisting polyamines, are examined, focusing on their molecular structure that enables different binding modes to be operated. Also, a number of examples of nucleotide binding through metal compl…
Controlling Multivalent Interactions in Triply-Threaded Two-Component Superbundles
2003
We have investigated the (1)H NMR spectra, the absorption spectra, the fluorescence spectra and decays, and the electrochemical properties of i). a tritopic receptor in which three benzo[24]crown-8 macrorings are fused onto a triphenylene core, ii). a trifurcated trication wherein three dibenzylammonium ions are linked 1,3,5 to a central benzenoid core, and iii). their 1:1 adduct which constitutes a triply-threaded, two-component supramolecular bundle. X-Ray crystallography has established the precise geometry of this paucivalent recognition motif in the solid state. In addition to [N(+)-H...O] hydrogen bonding and [C-H...O] interactions between the NH(2) (+) centers on the three dibenzylam…
Synthesis and characterization of a new spirooxindole grafted pyrrolidino/piperidine moiety
2021
In this text, we synthesized and characterized a new spirooxindole grafted pyrrolidino/piperidine moieties. The new hit obtained via one-pot reaction of the chalcone based cyclohexanone with the isatin and (R)-piperidine-2-carboxylic acid in MeOH under reflux for 48 h. The compound exclusively obtained in regio-selective and diastereo-selective manner. The chemical feature of the target compound is confirmed by 1H NMR and 13C NMR spectroscopy. In addition, we reported for the first time the X-ray single crystal structure of isatin. Its molecular packing depends mainly on strong O…H hydrogen bonds and π-π stacking interactions as well as weak H…H and H…C contacts. Using DFT calculations, is…
A real-space approach to the analysis of stacking faults in close-packed metals: Modelling and Q-space feedback Longo Alessandro
2020
An R-space approach to the simulation and fitting of a structural model to the experimental pair distribution function is described, to investigate the structural disorder (distance distribution and stacking faults) in close-packed metals. This is carried out by transferring the Debye function analysis into R space and simulating the low-angle and high-angle truncation for the evaluation of the relevant Fourier transform. The strengths and weaknesses of the R-space approach with respect to the usual Q-space approach are discussed.
Spatialization of the Semantic Web
2012
syntax for Horn-like rules. The SWRL as the form, antecedentconsequent, where both antecedent and consequent are conjunctions of atoms written a1^ ... ^ an. Atoms in rules can be of the form C(x), P(x,y), Q(x,z), sameAs(x,y), differentFrom(x,y), or builtIn(pred, z1, ..., zn), where C is an OWL description, P is an OWL individual-valued property, Q is an OWL data-valued property, pred is a datatype predicate URIref, x and y are either individual-valued variables or OWL individuals, and z, z1, ... zn are either data-valued variables or OWL data literals. An OWL data literal is either a typed literal or a plain literal. Variables are indicated by using the standard convention of prefixing the…
5-Methylbenzo[d][2,1,3]selenadiazole
2017
In the crystal of the title compound, C7H6N2Se, the molecules are arranged in rods along theb-axis direction and form dimeric units due to intermolecular Se...N contacts of 2.982 (2) Å. The molecules are further linked by weak π–π stacking interactions between the 2,1,3-selenadiazole and six-membered aromatic rings [centroid–centroid distance = 3.8509 (11) Å and ring slippage = 1.539 (3) Å].
catena-Poly[[diaquabis[1,4-bis(pyridin-4-yl)buta-1,3-diyne-κN]iron(II)]-μ-cyanido-κ2N:C-[dicyanido-κ2C-platinum(II)]-μ-cyanido-κ2C:N]
2017
The molecular structure of the title compound, [FePt(CN)4(C14H8N2)2(H2O)2]n, consists of one-dimensional polymeric [–Fe–NC–Pt(CN)2–CN–]∞chains. Two water molecules and two monodentate 1,4-bis(pyridin-4-yl)buta-1,3-diyne (bpb) ligand molecules complete the octahedral coordination sphere of the FeIIatoms. The Fe—N(py) bond length (py is pyridine) is 2.2700 (15) Å, Fe—N(cyanide) is 2.1185 (16) Å and the Fe—O distance is 2.1275 (14) Å. The water molecules are hydrogen bonded to either bpb ligands or cyanide groups of the planar [Pt(CN)4]2−anion of adjacent polymeric chains. These O—H...N hydrogen bonds, in conjunction with offset and tilted π–π stacking interactions between bpb ligands and cyan…