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Spectroscopic Titrations (spectroscopic + titration)
Selected AbstractsStudies on the Novel Calix [4] pyrrole and Its High Selectivity for p -NitrophenolCHINESE JOURNAL OF CHEMISTRY, Issue 7 2001Xun-Cheng Su Abstract Synthesis of novel neutral molecule receptor calix [4] pyrrole (2) from pyrrole and tropinone has been described and its ability of binding neutral molecules was tested. Spectroscopic titrations indicate that receptor 2 shows the highest selectivity for p -nitrophenol among m,o,p -nitrophenols due to the coincidence between the host's binding sites and the guest's geometry. [source] Flavonoids in plant nuclei: detection by laser microdissection and pressure catapulting (LMPC), in vivo staining, and uv,visible spectroscopic titrationPHYSIOLOGIA PLANTARUM, Issue 1 2006Jürgen Polster Previous studies in our laboratory have indicated that the nuclei of a number of trees are associated with flavonoids, especially flavan-3-ols. In the present study, three techniques were applied to verify that flavonoids are naturally incorporated into nuclei. These were histochemistry, UV,visible (UV-VIS) titration and laser microdissection. Nuclei from intact seed wings of Tsuga canadensis were isolated from their cells using laser microdissection and pressure catapulting (LMPC). Thereafter, the excised nuclei were stained with p -dimethylamino-cinnamaldehyde (DMACA), which resulted in a blue coloration due to the presence of flavanols. Thus, there is no doubt that the nuclei were, prior to staining, associated with flavanols. The nuclei of the coniferous species Abies lasiocarpa, Cedrus deodara, Cedrus libani, Juniperus communis, Picea abies, Picea orientalis and Pseudotsuga menziessii(Douglas fir) showed a yellow fluorescence typical for flavonols from the beginning of bud break over the entire growing season. However, after the bud-breaking period, the nuclei of all species, except for Cedrus deodara, showed additionally a blue reaction for flavanols. Rather late, in midsummer, blue-stained flavanols in nuclei were found in Picea orientalis. Generally, zeatin intensified the flavanol association with the nuclei. The main components of nucleosomes are DNA and the histone proteins. The nature of their association with the flavonols quercetin and rutin was investigated by UV-VIS spectroscopic titration. The data were evaluated by means of the Mauser (A and AD) diagrams. The results indicate that DNA shows largely no spectroscopically detectable association equilibria under the experimental conditions chosen. However, association (aggregation) equilibria can be observed with rutin or quercetin and histone sulphate in Tris buffer (pH 8.0, 7.4 and 7.0). In phosphate buffer, rutin shows spectroscopically no or only weak association with histone sulphate, in contrast to its behaviour towards quercetin. [source] Mono- and Dinuclear CuII and ZnII Complexes of Cyclen-Based Bis(macrocycles) Containing Two Aminoalkyl Pendant Arms of Different LengthsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005Carmen Anda Abstract The basicity and coordination properties towards CuII and ZnII of the bis(macrocycles) L1, L2 and L3 have been investigated by means of potentiometric, 1H NMR and UV/Vis spectroscopic titrations in aqueous solutions. The synthesis of L1 and L3 is also described. The three ligands are composed of two [12]aneN4 units separated by a p- phenylene spacer and differ in the length of the aminoalkyl pendant arms linked to each macrocyclic unit. L1,L3 form mono- and dinuclear complexes in aqueous solutions; in the dinuclear species each metal ion is coordinated by one of the two identical [12]aneN4 ligand moieties, as shown by the crystal structures of the complexes [Cu2L1]Cl4·8H2O, [Zn2L2](ClO4)4 and [Zn2L3](ClO4)4·H2O. In all structures the metal ion is pentacoordinate, and is bound to the four nitrogen donors of the cyclic unit and to the amine group of the side arm. The stability of both the [ML]2+ and [M2L]4+ complexes in aqueous solution decreases in the order L1 > L2 > L3. At the same time, both the [Cu2L]4+ and [Zn2L]4+ complexes show a different ability in proton binding among the three ligands, with the [M2L1]4+ complexes displaying the highest basicity. These results are explained in terms of the decreasing number of nitrogen donors involved in CuII or ZnII binding on passing from L1 to L3; in other words, while in the L1 dinuclear complexes each metal ion is coordinated to the four amine groups of a [12]aneN4 moiety and to the amine group of the side arm, in the L3 ones the metal cations are bound only to the four donor atoms of a cyclic moiety, the aminobutyl group not being coordinated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Dipyrrolyl-Functionalized Bipyridine-Based Anion Receptors for Emission-Based Selective Detection of Dihydrogen PhosphateCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2007Patrick Plitt Dr. Abstract New cationic anion receptors, based on the use of pyrrole-substituted bipyridine and coordinated to transition metals, are described. Specifically, polypyridine,ruthenium and ,rhodium cores have been functionalized to generate an anion binding site. The design was chosen to probe the influence of the pyrrole-to-pyrrole separation on anion-binding affinities and selectivities; this distance is greater in the new systems of this report (receptors 1 and 2) relative to that present in related dipyrrolyl quinoxaline based receptors 3 and 4. Solution-phase anion-binding studies, carried out by means of 1H,NMR spectroscopic titrations in [D6]DMSO and isothermal titration calorimetry (ITC) in DMSO, reveal that 1 and 2 bind most simple anions with substantially higher affinity than either 3 or 4. In the case of chloride anion, structural studies, carried out by means of single-crystal X-ray diffraction analyses, are consistent with the solution-phase results and reveal that receptors 1 and 2 are both able to stabilize complexes with this halide anion in the solid state. [source] A New Fluorescent Probe for Zinc(II): An 8-Hydroxy-5- N,N -dimethylaminosulfonylquinoline-Pendant 1,4,7,10-TetraazacyclododecaneCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2006Shin Aoki Prof. Abstract A new fluorescent probe for Zn2+, namely, 8-hydroxy-5- N,N -dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L8), was designed and synthesized (cyclen=1,4,7,10-tetraazacyclododecane). By potentiometric pH, 1H NMR, and UV spectroscopic titrations, the deprotonation constants pKa1,pKa6 of L8,4,HCl were determined to be <2, <2, <2 (for amino groups of the cyclen and quinoline moieties), 7.19±0.05 (for 8-OH of the quinoline moiety), 10.10±0.05, and 11.49±0.05, respectively, at 25,°C with I=0.1 (NaNO3). The results of 1H NMR, potentiometric pH, and UV titrations, as well as single-crystal X-ray diffraction analysis, showed that L8 and Zn2+ form a 1:1 complex [Zn(H,1L8)], in which the 8-OH group of the quinoline ring of L8 is deprotonated and coordinates to Zn2+, in aqueous solution at neutral pH. On addition of one equivalent of Zn2+ and Cd2+, the fluorescence emission of L8 (5 ,M) at 512 nm in aqueous solution at pH 7.4 [10 mM HEPES with I=0.1 (NaNO3)] and 25,°C increased by factors of 17 and 43, respectively. We found that the cyclen moiety has the unique property of quenching the fluorescence emission of the quinolinol moiety when not complexed with metal cations, but enhancing emission when complexed with Zn2+ or Cd2+. In addition, the Zn2+,L8 complex [Zn(H,1L8)] is much more thermodynamically and kinetically stable (Kd{Zn(H,1L8)}=[Zn2+]free[L8]free/[Zn(H,1L8)]=8 fM at pH 7.4) than the Zn2+ complexes of our previous Zn2+ fluorophores ([Zn(H,1L2)] and [Zn(L3)]). Furthermore, formation of [Zn(H,1L8)] is much faster than those of [Zn(H,1L2)] and [Zn(L3)]. The staining of early-stage apoptotic cells with L8 is also described. [source] Calix[n]bispyrrolylbenzenes: Synthesis, Characterization, and Preliminary Anion Binding StudiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2005Jonathan L. Sessler Prof. Abstract A series of novel calixpyrrole-like macrocycles, calix[n]bis(pyrrol-2-yl)benzene (calix[n]BPBs, n=2,4) 9,a,11,a, have been synthesized by means of the TFA-catalyzed condensation reaction of bis(pyrrol-2-yl)benzene 8,a with acetone. Calix[2]BPB 9,a represents an expanded version of calix[4]pyrrole in which two of the four meso bridges are replaced by benzene rings. By contrast, systems 10,a and 11,a, which bear great considerable to calixbipyrroles 2 and 3, represent higher homologues of the basic calix[n]BPB motif. Solution-phase anion binding studies, carried out by means of 1H NMR spectroscopic titrations in [D2]dichloromethane and isothermal titration calorimetry (ITC) in 1,2-dichloroethane, reveal that 9,a binds typical small anions with substantially higher affinities than 1, even though the same number of hydrogen bonding donor groups are found in both compounds. The basic building block for 9,a, benzene dipyrrole 8,a, also displays a higher affinity for anions than the building block for 1, dimethyldipyrromethane 16. Structural studies, carried out by single-crystal X-ray diffraction analyses, are consistent with the solution-phase results and reveal that 9,a is able to stabilize complexes with chloride and nitrate in the solid state. Structures of the PF6, and NO3, complexes of 10,a were also solved as were those of the acetone adduct of 9,a and the ethyl acetate adduct of 11,a. [source] | ||||||||||