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Stoichiometry Complex (stoichiometry + complex)
Selected AbstractsComplexation and chiral drug recognition of an amphiphilic phenothiazine derivative with , -cyclodextrinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2008Andrés Guerrero-Martínez Abstract Promethazine hydrochloride (PTZ) is an amphiphilic drug derived from the phenothiazine structure that possesses a charged aliphatic chain with a chiral carbon. In the presence of , -cyclodextrin (, -CD), this drug undergoes significant changes of its photophysical properties in aqueous solution. Fluorescence spectroscopy measurements show the formation of a 1:1 stoichiometry complex with quantum yield lower than that of the pure PTZ, and two fluorescence lifetimes, which can be assigned to the free and complexed forms of the drug. In addition, 1H NMR spectra, and 2D rotating-frame Overhauser enhancement spectroscopy (ROESY) were used to characterize the drug and the complex, and to determine the effects of the complexation on the aggregation. For the drug binary system, a noncooperative association process is observed, and in the presence of macrocycle, the chemical shifts reveal a chiral resolution of the drug enantiomers, with different stability constants of the complexes. , -CD modifies the aggregation of PTZ in an extension that confirms the formation of a 1:1 complex. ROE enhancements and molecular modeling strategies show the most likely structure of the complex in solution, in which one of the phenyl rings is buried into the CD cavity, with a slight inclusion of the aliphatic part. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1484,1498, 2008 [source] Calix[4]arene-Based Enantioselective Fluorescent Sensors for the Recognition of N-Acetyl-aspartateCHINESE JOURNAL OF CHEMISTRY, Issue 4 2008Guang-Yan QING Abstract Two-armed chiral anion receptors (1 and 2), calix[4]arenes bearing dansyl fluorophore and (1R,2R)- or (1S,2S)-1,2-diphenylethylenediamine binding sites, were prepared and examined for their chiral amino acid anion binding abilities by the fluorescence spectra in dimethylsulfoxide (DMSO). The results of non-linear curve fitting indicate that 1 or 2 forms a 1:1 stoichiometry complex with N -acetyl- L - or D -aspartate by multiple hydrogen bonding interactions, exhibiting good enantioselective fluorescent recognition for the enantiomers of N -acetyl-aspartate, [receptor 1:Kass(D)/Kass(L)=6.74; receptor 2:Kass(L)/Kass(D)=6.48]. The clear fluorescent response difference indicates that receptors 1 and 2 could be used as a fluorescent chemosensor for N -Acetyl-aspartate. [source] Thiourea Based Tweezer Anion Receptors for Selective Sensing of Fluoride IonsCHINESE JOURNAL OF CHEMISTRY, Issue 5 2007You-Ming Zhang Abstract Three 3,3,-di(4-substituted-phenyl)-1,1,-isophthaloylbis(thiourea) compounds were designed as novel neutral anion receptors, and synthesized by simple steps in good yields. The single crystal structure of receptor 1 shows that a solvent molecule was captured by the host molecule through intermolecular hydrogen bonding. Moreover, it was self-assembled as a supramolecular system for the presence of abundant inter- and intramolecular hydrogen bonding and ,-, interactions between phenyl groups. Their application as anion receptors has been examined by UV-Vis and 1H NMR spectroscopy, showing that they had a higher selectivity for fluoride than other halides. The host and guest formed a 1:1 stoichiometry complex through hydrogen bonding interactions in the first step, then following a process of deprotonation in presence of an excess of F, in the solvent of DMF. [source] Study on the Anion Recognition Properties of Synthesized Receptors (III): Convenient Synthesis and Anion Recognition Property of Bisthiosemicarbazone DerivativeCHINESE JOURNAL OF CHEMISTRY, Issue 10 2006You-Ming Zhang Abstract A new series of bisthiosemicarbazone derivative receptors (1, 2 and 3) have been synthesized by simple steps in good yields. Their anion recognition properties were studied by UV-Vis and 1H NMR spectroscopy. The result showed that the receptors 1, 2 and 3 all had a better selectivity to F,, CH3COO, and H2PO4,, but no evident binding with Cl,, Br,, I,, NO3, and HSO4,. Upon addition of the three anions to the receptors in DMSO, the solution acquired a color change from colorless to dark yellow that can be observed by the naked-eyes, thus the receptors can act as fluoride ion sensors even in the presence of other halide ions. The data showed that it was regular that the three receptors had different binding ability with the three anions. For the same anion, the association constants followed the trend: receptor 1>3>2. The UV-Vis data indicates that a 1:1 stoichiometry complex is formed through hydrogen bonding interactions between compound 1, 2 or 3 and anions. [source] Two Multi-armed Neutral Receptors for ,,, -Dicarboxylate AnionsCHINESE JOURNAL OF CHEMISTRY, Issue 4 2006Jin-Long Wu Abstract Two new multi-armed neutral receptors 1 and 2 containing thiourea and amide groups were synthesized by simple steps in good yields. Receptors 1 and 2 have a better selectivity and higher association constants for malonate anion than other anions examined by the present work. In particular, distinct color changes were observed upon addition of dicarboxylate anions to the solution of 1 in DMSO. The UV-Vis and fluorescence spectra data indicate that a 1:2 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of shorter carbon chain, and a 1:1 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of longer carbon chain through hydrogen bonding interactions. [source] | ||||||||||