Search results for "stereo"
showing 10 items of 6147 documents
Atom, atom-type and total molecular linear indices as a promising approach for bioorganic and medicinal chemistry: theoretical and experimental asses…
2004
Abstract Helminth infections are a medical problem in the world nowadays. In this paper a novel atom-level chemical descriptor has been applied to estimate the anthelmintic activity. Total and local linear indices and linear discriminant analysis were used to obtain a quantitative model that discriminates between anthelmintic and non-anthelmintic drug-like compounds. The discriminant model has an accuracy of 90.11% in the training set, with a high Matthews’ correlation coefficient (MCC = 0.80). To assess the robustness and predictive power of the obtained model, internal (leave-n-out) and external validation process was performed. The QSAR model correctly classified 88.55% of compounds in t…
New acridinium trifluoromethanesulfonate stacks induced in the presence of organotin(IV) complexes
2013
Abstract Three new crystalline architectures based on acridinium trifluoromethanesulfonate salts [C13H10N]+[CF3SO3]– have been isolated as single crystals from the reaction of the dimeric hydroxo di-n-butylstannane trifluoromethanesulfonato complex [n-Bu2Sn(OH)(H2O)(CF3SO3)]2 (1) with acridine (C13H9N, Acr), in dichloromethane at room temperature. When an equimolar mixture of anthracene (C14H10, Ant) and acridine is initially used, the crystallization of a sandwich-type arrangement occurs, leading to the intercalation of one molecule of anthracene between two acridium trifluoromethanesulfonate salt molecules. In the three X-ray structures reported, the crystal packing involves the contribut…
Organotin(IV) trifluoromethanesulfonates chemistry: Isolation and characterization of a new di-n-butyl derivative presenting a Sn3O3 core
2012
Abstract Reaction of the dimeric hydroxo di-n-butylstannane trifluoromethanesulfonato complex [n-Bu2Sn(OH)(H2O)(CF3SO3)]2 (1) with a mixture of anthracene (C14H10, Ant) and phenazine (C12H8N2, Phz) in dichloromethane at room temperature yielded the novel di-n-butyltin(IV) trifluoromethanesulfonate salt {[n-Bu2Sn(H2O)]2O·n-Bu2Sn(OH)2}(CF3SO3)2 (2), together with the co-crystallization of phenazinium trifluoromethanesulfonate salts ([C12H9N2][CF3SO3], PhzH) collected in the solid state in two distinct self-assembled architectures, 3 and 4, showing π–π stacking interactions, and involving the intercalation of free molecules of phenazine and anthracene, respectively. Complex 2 is a cationic tri…
Ion-Pairing Effects in the Self-Assembly of a Fluorescent Pseudorotaxane
2006
Herein we report on the self-assembly, in a low polarity solvent, of a pseudorotaxane species comprising binaphthyl-26-crown-8 (BN26C8) as the macrocyclic host and anthracenyl-benzylammonium as the threadlike positively charged guest (ABH+). Absorption and luminescence data reveal a very efficient energy transfer process occurring from the binaphthyl to the anthracene singlet excited states. The self-assembly is highly dependent on the nature of the counteranion confirming the crucial role played by it in the competition between the self-assembly process and the formation of ion pairs (ABH+X-). This behavior can be readily evidenced in dilute solutions from the analysis of the luminescence …
Potentiometric, NMR, and Fluorescence-Emission Studies on the Binding of Adenosine 5′-Triphosphate (ATP) by Open-Chain Polyamine Receptors Containing…
2003
The interaction in aqueous solution of adenosine 5′-triphosphate (ATP) with a series of open-chain polyamines linked at one or both ends to anthrylmethyl or naphthylmethyl fragments was followed by potentiometric titration, 1H-, 13C-, and 31P-NMR spectroscopy, and by steady-state fluorescence measurements. The results revealed greater stabilities for the compounds containing one anthracene moiety than for those with one naphthalene moiety, the stabilities of the compounds with both ends N-substituted with naphthylmethyl groups being close to those containing just one anthrylmethyl unit. The 1H-NMR spectra showed that in all systems, there is involvement of π-π stacking interactions in the s…
Self-assembly of 1- and 2-Dimensional Multicompartmental Arrays via the 2-Aminopyrimidine H-Bonding Motif and Selective Guest Inclusion
2000
Abstract The H-bond mediated self-assembly of aminopyrimidine substituted anthracene derivatives 4 and 5, respectively, generate 1- and 2-dimensional multicompartmental arrays in the solid state as revealed by X-ray crystallographic analysis. The derived ‘pigeon-hole’ lattice is defined by syn-coplanar positioning of anthracene moieties at a distance of ca. 7 A, allowing the formation of selective clathrate-type inclusion entities with guests of appropriate shape and size, in particular phenazine, which presents both structural and interactional complementarity. These data provide insight into the interplay of the different structural and interactional features of the molecular components t…
Synthesis of an anthracenyl bridged porphyrin–corrole bismacrocycle. Physicochemical and electrochemical characterisation of the biscobalt μ-superoxo…
2001
Abstract Dicobalt or heterobimetallic cofacial bisporphyrins are up till now amongst the very few molecular electrocatalysts able to promote the direct reduction of dioxygen to water via a four-electron process in acidic medium. Numerous studies have been devoted to elucidate the key steps of this catalytic reaction and an important result has revealed an unexpected high dioxygen affinity for a mixed valence Co(II)/Co(III) cofacial porphyrin, the key intermediate complex being a μ-superoxo derivative. At the same time, the great importance assumed by ‘Pacman’ porphyrins and the recent developments in corrole chemistry have provided the stimulation to synthesise porphyrin–corrole dyads which…
Electronic Interactions in a New π-Extended Tetrathiafulvalene Dimer
2006
The first pi-extended tetrathiafulvalene (exTTF) dimer in which the two exTTF units are covalently connected by 1,3-dithiole rings has been obtained in a multistep synthetic procedure involving the Ullmann cross-coupling reaction by using copper(I) thiophene-2-carboxylate (CuTC). The electronic spectrum reveals a significant electronic interaction between the exTTF units. The electrochemical study carried out by cyclic voltammetry in solution and in thin-layer conditions, and the electrochemical simulation and spectroelectrochemical (SEC) measurements confirm the electronic communication and show that the oxidation of dimer 14 occurs as two consecutive 2 e(-) processes D(0)-D(0)-->D(2+)-D(0…
Dendron to central core S1-S1 and S2-S(n) (n1) energy transfers in artificial special pairs containing dendrimers with limited numbers of conformatio…
2013
Two dendrimers consisting of a cofacial free-base bisporphyrin held by a biphenylene spacer and function- alized with 4-benzeneoxomethane (5-(4-benzene)tri-10,15,20-(4-n-octyl- benzene)zinc(II)porphyrin) using either five or six of the six available meso-positions, have been synthesized and characterized as models for the an- tenna effect in Photosystems I and II. The presence of the short linkers, -CH2O-, and long C8H17 soluble side chains substantially reduces the number of conformers (foldamers) compared with classic dendrimers built with longer flexible chains. This simpli- fication assists in their spectroscopic and photophysical analysis, notably with respect to fluorescence resonance…
Synthesis and anti-HIV activity of 2,3-diaryl-1,3-thiazolidin-4-ones
2002
Several 1,3-thiazolidin-4-ones bearing a 2,6-dihalophenyl group at C-2 and a variously substituted phenyl ring at N-3 have been synthesized and tested as anti-HIV agents. The results of the in vitro tests showed that some of them proved to be effective inhibitors of HIV-1 replication.