Search results for "Hydrogen"
showing 10 items of 4254 documents
Molecular recognition of naphthalene diimide ligands by telomeric quadruplex-DNA: the importance of the protonation state and mediated hydrogen bonds.
2016
In depth Monte Carlo conformational scans in combination with molecular dynamics (MD) simulations and electronic structure calculations were applied in order to study the molecular recognition process between tetrasubstituted naphthalene diimide (ND) guests and G-quadruplex (G4) DNA receptors. ND guests are a promising class of telomere stabilizers due to which they are used in novel anticancer therapeutics. Though several ND guests have been studied experimentally in the past, the protonation state under physiological conditions is still unclear. Based on chemical intuition, in the case of N-methyl-piperazine substitution, different protonation states are possible and might play a crucial …
Straightforward Regio- and Diastereoselective Synthesis, Molecular Structure, Intermolecular Interactions and Mechanistic Study of Spirooxindole-Engr…
2021
Straightforward regio- and diastereoselective synthesis of bi-spirooxindole-engrafted rhodanine analogs 5a–d were achieved by one-pot multicomponent [3 + 2] cycloaddition (32CA) reaction of stabilized azomethine ylide (AYs 3a–d) generated in situ by condensation of L-thioproline and 6-chloro-isatin with (E)-2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(2-morpholinoethyl)acetamide. The bi-spirooxindole-engrafted rhodanine analogs were constructed with excellent diastereo- and regioselectivity along with high chemical yield. X-ray crystallographic investigations for hybrid 5a revealed the presence of four contiguous stereocenters related to C11, C12, C19 and C22 of the spiro struct…
Synthesis and characterization of triphenyltin(IV) 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates. Crystal and molecular structures of Ph3Sn{O2CC6H3-…
2005
Abstract Triphenyltin 5-[(E)-2-(4-methylphenyl)-1-diazenyl]-2-hydroxybenzoate, Ph3SnL2H, has been prepared and characterized, its structure determined by X-ray crystallography, and the structure compared with those of its homologues. Two polymorphs were isolated from the same crystallization attempt. The reactivity of tetrahedral Ph3SnL1H (L1H = 5-[(E)-2-(2-methylphenyl)-1-diazenyl]-2-hydroxybenzoate) towards 2,2′-bipyridine (bipy) has been investigated to ascertain the ability of bipy to coordinate to the Sn-complex and the resultant changes in the molecular architecture. The crystal structure of the product revealed that the bipy moiety does not coordinate to the Sn atom, but forms a cycl…
Folding Patterns in a Family of Oligoamide Foldamers
2015
A series of small, unsymmetrical pyridine-2,6-dicarboxylamide oligoamide foldamers with varying lengths and substituents at the end groups were synthetized to study their conformational properties and folding patterns. The @-type folding pattern resembled the oxyanion-hole motifs of enzymes, but several alternative folding patterns could also be characterized. Computational studies revealed several alternative conformers of nearly equal stability. These folding patterns differed from each other in their intramolecular hydrogen-bonding patterns and aryl-aryl interactions. In the solid state, the foldamers adopted either the globular @-type fold or the more extended S-type conformers, which w…
3-formylphenylboronic acid.
2004
The molecule of the title compound, C(7)H(7)BO(3), is planar, and the bond lengths and angles are typical. The formyl group is essentially coplanar with the benzene ring but does not influence significantly the distortion of the ring, although the formyl group does have a strong influence on the crystal packing. The geometry of the boronic acid group is typical. In the crystal structure, the molecules are linked by O-H...O hydrogen bonds.
Structure and properties of hydroxyl radical modified nucleic acid components II. 8-Oxo-adenine and 8-oxo-2′-deoxy-adenosine
1997
Abstract The tautomerism of the 8-oxo-adenine (8-oxo-A) and 8-oxo-2′-deoxy-adenosine (8-oxo-dA) was analysed on the basis of semiempirical, SCF ab initio and DFT density functional quantum chemistry calculations. The results of full gradient geometry optimisation of all possible 8-oxo-A and 8-oxo-dA structures lead to the conclusion that the most stable form is 8-keto-6-amino-tautomer. The second stable tautomer corresponds to 8-hydroxy-isomer. Such an order was unchanged after solvating process. In all studied solvents: water, methanol, acetone, cyclohexane the keto-tautomer proceeds the enol one. The preferred N-glycoside torsion angle corresponds to syn rotamer of 8-oxo-dA in all studied…
Long-range substituent and temperature effect on prototropic tautomerism in 2-(acylmethyl)quinolines
2001
Tautomeric equilibria between 2-(cinnamoylmethyl)quinoline, (Z)-1,2-dihydro-2-(cinnamoylmethylene)quinoline and (Z)-4-phenyl-1-(2-quinolyl)-1,3-butadien-2-ol were studied by 1H, 13C and 15N NMR methods. The —CHCH— fragment conjugated with phenyl and a strong electron donor p-(1-pyrrolidine) substituent were found to favour the enolimine tautomer. This undergoes fast exchange (on the NMR time-scale) with the enaminone form. The amount of the latter tautomer was found to increase at low temperatures. Copyright © 2001 John Wiley & Sons, Ltd.
A Hydrogen-Bonded Supramolecular meso-Helix
2003
[EN] A new one-dimensional hydrogen-bonded polymer with a unique meso-helical structure has been prepared from the spontaneous self-assembly in the solid-state of meta-substituted phenylene dioxamic acid diethyl ester monomers. The helical nature of this molecule and its self-complementary character, through intermolecular hydrogen bonding between oxamic acid ester functions, are the two main factors responsible for the crystalline aggregation process, as confirmed by both experimental X-ray crystallographic data and theoretical ab initio calculations.
Two (E)-2-({[4-(dialkylamino)phenyl]imino}methyl)-4-nitrophenols.
2012
The slow evaporation of analytical NMR samples resulted in the formation of crystals of (E)-2-({[4-(dimethylamino)phenyl]imino}methyl)-4-nitrophenol, C15H15N3O3, (I), and (E)-2-({[4-(diethylamino)phenyl]imino}methyl)-4-nitrophenol, C17H19N3O3, (II). Despite the small structural difference between these twoN-salicylideneaniline derivatives, they show different space groups and diverse molecular packing. The molecules of both compounds are close to being planar due to an intramolecular O—H...N hydrogen bond. The 4-alkylamino-substituted benzene ring is inclined at an angle of 13.44 (19)° in (I) and 2.57 (8)° in (II) with respect to the 4-nitro-substituted phenol ring. Only very weak intermole…
Synthesis and characterization of mononuclear complexes containing 3-acetylamino-1,2,4-triazole (aat). X-ray structure of [Co(aat)2(H2O)2]Br2
1993
Abstract The spectroscopic characteristics of the isostructural compounds [M(aat) 2 (H 2 O) 2 ]X 2 (aat = 3-acetylamino-1,2,4-triazole; M = Co, Cu, X = Br, CI; M = Ni, X = Cl) are described. The structure of [Co(aat) 2 (H 2 O) 2 ]Br 2 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P 2 1 / a with a = 9.686(3), b = 14.433(4), c = 6.169(2) A, β = 92.84(2)° and Z = 2. The structure was refined to final R and R ′ values of 0.033 and 0.039 for 1066 observed reflections. In the mononuclear cationic complex, having an imposed crystallographic C i symmetry, the cobalt atom is surrounded in a slightly distorted octahedral arrangement by two axial water molecule…