Search results for "BOND"
showing 10 items of 3527 documents
Speciation of trialkyltin(IV) cations in natural fluids
2004
The hydrolysis of (CH(3))(3)Sn(+), (C(2)H(5))(3)Sn(+) and (C(3)H(7))(3)Sn(+) has been studied in a Synthetic Seawater (SSW) ionic medium simulating the major composition of natural seawater, at different salinities (5 less than or equal to S less than or equal to 45), and at t = 25 degreesC. Interactions with anionic components of SSW, considered as single sea salt, are determined by means of a complex formation model. By potentiometric measurements (ISE-H(+) and ISE-F(-) electrodes), the model has been extended to also consider interactions of organotins with carbonate and fluoride ions, which are other important components of seawater. Literature and new values of hydrolysis constants in …
Structural Investigation of Water/Lecithin/Cyclohexane Microemulsions by FT-IR Spectroscopy
1995
Abstract FT-IR spectra of water/lecithin/deuterated cyclohexane microemulsions as a function of water/lecithin molar ratio R ( R = [water]/[lecithin]) at various volume fractions ( O ) of the micellar phase have been recorded at 25°C. After elimination of the small spectral contributions due to deuterated cyclohexane and normalization, the shape of the C–H stretching band due to lecithin has been found dependent upon R and O whereas that of the O–H stretching band has been found dependent only upon R . The change in shape of the C–H band was interpreted in terms of a modification of the lecithin alkyl chain packing order. The analysis of the O–H band provides evidence that the hydroxylic gr…
Photocrosslinkable dextran hydrogel films as substrates for osteoblast and endothelial cell growth
2012
Functional hydrogel films on solid supports are versatile materials with large potential for cell growth and tissue engineering. Here, we report on a modular approach to generate functional hydrogel composite films for endothelial and osteoblast cell co-culture. The polymer network of the parent hydrogel was formed by a dextran derivative (BP-CMD), which contained carboxymethyl (CM) groups for further chemical functionalization and benzophenone (BP) moieties as a photocrosslinkable unit. BP-CMD could be synthesized by three different routes, first with the benzophenone unit attached via an amide bond, or second by an ether bond, or third as an ion pair between the benzophenone ammonium salt…
An Insight into Substrate-Dependent Fluorination of some Highly Substituted Alicyclic Scaffolds
2017
The substrate-dependent fluorination of some highly-functionalized cyclopentane derivatives with multiple chiral centers has been investigated. The key steps of the stereocontrolled syntheses are the oxidative cleavage of the ring carbon–carbon double bond of readily available diexo or diendo norbornene β-amino acid derivatives followed by transformation of the resulted dialdehyde stereoisomers by reduction. Finally, substrate-directable chemodifferentiation of different types of hydroxy groups under fluorination procedures gave various densely functionalized alicyclic derivatives or heterocycles.
Selective recognition of aromatic hydrocarbons by endo-functionalized molecular tubes via C/N-H⋅⋅⋅π interactions
2018
Abstract Molecular recognition of aromatic hydrocarbons by four endo -functionalized molecular tubes has been studied by 1 H NMR spectroscopy, computational methods, and single crystal X-ray crystallography. The binding selectivity is rationalized by invoking shape complementarity and dipole alignment. The non-covalent interactions are proved to predominantly be C/N-H⋅⋅⋅ π interactions.
Cu(II), Ni(II) and Zn(II) mononuclear building blocks based on new polynucleating azomethine ligand : Synthesis and characterization
2017
Five new mononuclear complexes formed by the polynucleating ligand 2-[1-(3,5-dimethyl)pyrazolyl]-2-hydroxyimino-N′-[1-(2-pyridyl)ethylidene]acetohydrazide (HL): [Ni(L)(HL)]ClO4·2CH3OH (1), [Ni(L)2]·CH3OH (2), [Zn(L)(HL)]ClO4·2CH3OH (3), [Zn(L)2]·CH3OH (4) and [Cu(L)2]·CH3OH (5) were synthesized and characterized by elemental analysis, mass-spectrometry, IR-spectroscopy and X-ray analysis. The complexes reveal distorted octahedral N4O2 coordination arrangement formed by both protonated and deprotonated (1, 3) or two deprotonated ligand molecules (2, 4, 5). The presence of non-coordinated oxime and pyrazole groups resulted in the formation of extensive systems of hydrogen bonds in the crystal…
The Influence of the Amide Linkage in the FeIII-Binding Properties of Catechol-Modified Rosamine Derivatives
2015
The two new fluorescent ligands RosCat1 and RosCat2 contain catechol receptors connected to rosamine platforms through an amide linkage and were synthesized by using microwave-assisted coupling reactions of carboxyl- or amine-substituted rosamines with the corresponding catechol units and subsequent deprotection. RosCat1 possesses a reverse amide, whereas RosCat2 has the usual oriented amide bond (HNCO vs. CONH, respectively). The ligands were characterized by means of NMR spectroscopy, mass-spectrometry, and DFT calculations and X-ray crystallography studies for RosCat1. The influence of the amide linkage on the photophysical properties of the fluorescent ligands was assessed in different …
Crystal structure of C-2-benzo-thia-zole-N-methyl-nitrone.
2015
The molecule of the title compound {systematic name:N-[(benzothiazol-2-yl)methylidene]methylamineN-oxide}, C9H8N2OS, is close to planar [maximum deviation from the mean plane = 0.081 (2) Å], its conformation being stabilized by a strong intramolecular attractive S...O interaction [2.6977 (16) Å]. In the crystal, molecules are linked into centrosymmetric dimers by pairs of weak C—H...O hydrogen bonds.
Michael additions to double bonds of esters of N-protected (s)-phenylalanyldehydroalanine (X-(s)-Phe-ΔAla-OMe) and its phosphonic acid counterpart (X…
2017
Electrophilic addition of amines, thiols and bromide to the double bonds of model dehydrodipeptides and dehydrophosphonodipeptide was studied. The double bond in these two classes of peptides reacted similarly and gave the same products. These results indicate that dehydropeptides are very good candidates as substrates for modifications of peptide side-chains.
Studies of Nature of Uncommon Bifurcated I–I···(I–M) Metal-Involving Noncovalent Interaction in Palladium(II) and Platinum(II) Isocyanide Cocrystals
2021
Two isostructural trans-[MI2(CNXyl)2]·I2 (M = Pd or Pt; CNXyl = 2,6-dimethylphenyl isocyanide) metallopolymeric cocrystals containing uncommon bifurcated iodine···(metal–iodide) contact were obtained. In addition to classical halogen bonding, single-crystal X-ray diffraction analysis revealed a rare type of metal-involved stabilizing contact in both cocrystals. The nature of the noncovalent contact was studied computationally (via DFT, electrostatic surface potential, electron localization function, quantum theory of atoms in molecules, and noncovalent interactions plot methods). Studies confirmed that the I···I halogen bond is the strongest noncovalent interaction in the systems, followed …