Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Job’s plot

A graph (known as a Job s plot) is now made of the physical property (in effect, the concentration of the complex) as a function of the ratio [B]/([B] + [A]) (or sometimes [B]/[A]). A maximum or minimum (depending on the type of property measured) in the curve will be found when the ratio of the constituents in the solution is the same as it is in the formula for the complex. Figure 19.2 shows a graph constructed as just described. [Pg.674]

Job s plot, the following equation can be derived with the same notations as above ... [Pg.347]

In order to confirm formation of the oT15/oA15 duplex, additional techniques were used to characterize the complex. Stoichiometery analysis (Job s plot binding) supported the formation of a 1 1 complex. CD-assisted melting experiments performed on the... [Pg.169]

Fig. 4 Continuous variation plots for (a) ( )-CL//3-CD and (b) ( )-CL/HDAS-/3-CD complexes. The complexation-induced chemical shifts of aromatic protons were used for the construction of Job s plots in the case of ( )-CL//3-CD complex and the protons of ten-butyl moiety in the case of ( )-CL/HDAS-/3-CD complex. (Reproduced with permission from Ref. 65.)... [Pg.207]

Aprotic solvents mimic the hydrophobic protein interior. However, a functional artificial receptor for flavin binding under physiological conditions must be able to interact with the guest even in competitive solvents. As found by spectroscopic measurements with phenothiazene-labeled cyclene, the coordinative bond between flavin and Lewis-acidic macrocyclic zinc in methanol was strong enough for this function. Stiochiometry of the complex was proved by Job s plot analysis. Redox properties of the assemblies in methanol were studied by cyclic voltammetry which showed that the binding motif allowed interception of the ECE reduction mechanism and stabilisation of a flavosemiquinone radical anion in a polar solvent. As a consequence, the flavin chromophore switched from a two-electron-one-step process to a two-step-one-electron-each by coordination. [Pg.98]

Shao and coworkers [61] have demonstrated that a noncovalent charge-transfer complex of calix[4]pyrrole-chloranil can be used as a chromogenic sensor for F and H2POj. Upon addition of calix[4]pyrrole 75 to the solution of chloranil 76 in chloroform, the color changed from pale yellow to blue. This indicated the formation of a charge-transfer complex between calix[4] pyrrole and chloranil in chloroform. The Job s plot analysis showed a 1 1 complex with... [Pg.189]

El-Walily et al. [14] described a simple and sensitive spectrophotometric method for the determination of buclizine in bulk and tablets was based on the formation of charge-transfer complex between buclizine as n-donor and iodine as a-acceptor measurement of the absorbance at 295 and 355 nm. A Job s plot indicated a 1 1 complex between the drug and iodine. [Pg.17]

In contrast to 2, the above derivatives incorporate four hydrogen bond donors. As a consequence, a favourable bonding situation is present in which the four secondary amine protons of each host can interact with the two charged carboxylate groups of the guest - see 4a and 4b. The proposed structure of the complex of the bis-urea derivative was supported by the existence of large NMR downfield shifts for both the inner and outer urea NH resonances in deutero-dimethyl sulfoxide and the observation of intramolecular H NOEs between the receptor aryl and the guest CH2 resonances in this solvent. A Job s plot confirmed the 1 1 stoichiometry of the product. [Pg.22]

Using plastic disposable cells - those are adequate for work in the near-UV region/J. d.g. for Job s plot studies, as well ns the. visible Iange... [Pg.165]

Results Summary for the UV-Visible/Job s Plot Analysis of Pyridine Binding to A, V -disal icy I aldehyde-1,3-prop ancdiimincnickel (II)... [Pg.76]

Q3.9 What did your Job s plot reveal Draw a complex supported by your results. [Pg.77]

To obtain the formation constant, the number of metal-bound ligands, L or pyridine, must be independently determined. The Job s plot analysis in Experiment 3.6 revealed that a 1 1 Ni salpd-pyridine complex is formed we will assume this is the case. [Pg.78]

This procedure assumes bis complex formation. It is recommended that a Job s plot be performed with cysteine (A250 see Experiment 3.6). [Pg.183]

Fig. 2.2. Determination of stoichiometry from the x-coordinate at the maximum of the curve in Job s Plot. Fig. 2.2. Determination of stoichiometry from the x-coordinate at the maximum of the curve in Job s Plot.
The practically important point here is the follo ving Even if the concentration of complex ([C]) could not be measured directly, the [C] (y-axis) can be replaced vith a parameter proportional to [C]. Then the same x-coordinate and with it the same stoichiometry is obtained at the maximum as that in Job s plot. This means the stoichiometry can even then be determined even vhen [C] cannot be obtained... [Pg.21]

Depending on the selected experiment, a suitable observable property should be selected and the complex concentration [C] should be replaced by it in Job s plot. In the following, UV/vis spectroscopy is discussed as a representative example. [Pg.22]

Fig. 2.4. Modified Job s Plot for complexation of host and guest by UV/vis spectroscopy observed ----- calculated. Fig. 2.4. Modified Job s Plot for complexation of host and guest by UV/vis spectroscopy observed ----- calculated.
The stoichiometry is determined from the x-coordinate at the maximum in the modified Job s plot where [H]q (d - dj,) is plotted as y-coordinate instead of [C] for the following reason. [Pg.38]

These ligands are now well represented in complexes with the lanthanides, but were not investigated until 1962, when a study in aqueous solution using a Job s plot method, e.g. at 451 nm for Ho ", showed that a complex Ho(phen)2" was formed. Pr, Nd and Er tripositive ions were also studied, but no solid products were characterized. Indeed, stability constants in water are possibly too low for a solid complex to be isolated. A little later, there were several reports of the isolation of bipyridyl and 1,10-phenanthroline complexes from ethanolic solution. It is perhaps of interest that at this time, the lanthanides were believed not to form stable amine complexes and the role of higher coordination numbers in lanthanide complexes was not fully appreciated. Complexes isolated included the stoichiometries M(N03)s(bipy)2, where M = M(NCS)3(bipy)3, where M = La, Ce, Dy M(MeC02)3(bipy),... [Pg.2908]

Figure 10-3 Job s plots for ( ) chlorpheniramine(CHL)/p-CD complex (reproduced by permission from [19]). Figure 10-3 Job s plots for ( ) chlorpheniramine(CHL)/p-CD complex (reproduced by permission from [19]).

See other pages where Job’s plot is mentioned: [Pg.348]    [Pg.171]    [Pg.212]    [Pg.1069]    [Pg.1078]    [Pg.422]    [Pg.183]    [Pg.173]    [Pg.32]    [Pg.2085]    [Pg.2099]    [Pg.2108]    [Pg.76]    [Pg.77]    [Pg.200]    [Pg.20]    [Pg.21]    [Pg.23]    [Pg.23]    [Pg.38]    [Pg.47]    [Pg.451]    [Pg.2917]    [Pg.348]    [Pg.243]    [Pg.160]   
See also in sourсe #XX -- [ Pg.22 ]

See also in sourсe #XX -- [ Pg.20 , Pg.38 ]

See also in sourсe #XX -- [ Pg.127 ]




SEARCH



Job plots

© 2024 chempedia.info