1,10-Phenanthroline, a commonly employed chelate in supramolecular chemistry,108 develops a facility through p-sulfonatocalix<4>arene as a face-to-face dimer, where each of the π⋯π stacked 1,10-phenanthroline molecules are bound slantwise in a calixarene cavity as component of a molecular capsule (Fig. 22A and also B). These are assembled into columns or tapes in the extfinished 3D structure.109,110 Other variation of binding settings for the two components include the formation of an open up inclusion facility quite than forming a capsule in the visibility of the hexa-aqua aluminum ion.111 For the open inclusion complex, the overall arrangement is a chain-favor motif through the had 1,10-phenanthroline cations π-stacked via exo walls of neighboring calixarenes. A equivalent framework was formed through 5,6-dihydropyrazion<1,2,3,4-lmn><1,10>-phenanthroline-4,7-diium (Fig. 22C and also D).112 1H NMR data is constant with the setup of the solid state crystal structures.109,110



Figure 22. Molecular capsule containing 2 molecules of π-stacked 1,10-phenanthroline (A) and matching extended framework (B). Inclusion complicated of 5,6-dihydropyrazion<1,2,3,4-lmn><1,10>-phenanthroline-4,7-diium (C), and also corresponding extended structure (D).109,110 H atoms omitted for clarity.

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Copper(II) or lanthanide(III) ions (Gd3 +, Tb3 +, Nd3 +, Ce3 +) in a mixture of 1,10-phenanthroline and p-sulfonatocalix<4>arene result in assemblies in which a steel chelate complex is likewise coordinated to the calix<4>arene via a sulfonate team (Fig. 23).117–120 Interestingly, the 2:2 bis-molecular capsule confining two 1,10-phenanthroline molecules persists together with steel coordicountry close to the capsule seam. For the Cu2 + complicated, the capsules are arranged through water networks current in the extfinished structure, while for the Ln3 + complexes, the in its entirety framework has wave-choose layers of chains and grid-choose chains.117–119 A 1:1 inclusion facility of 1,10-phenanthroline and calix<4>arene additionally forms for Zn2 + coordinated to 1,10-phenanthroline in an as a whole bilayer arrangement.121



Figure 23. Variation in host–guest interactions and the in its entirety self-assembly for 1,10-phenanthroline coordinated by transition-steel (Cu2 +) and also lanthanides (Gd3 +, Nd3 +).113–116 H atoms omitted for clarity.


Other supramolecular arrangements based on 1,10-phenanthroline and also p-sulfonatocalix<4>arene encompass coordination of the calixarene in between two binuclear oxo-connected Fe3 + phenanthroline complexes (Fig. 24A).122 In an additional finding, a tris-1,10-phenanthroline Ni2 + facility is formed and one of these ligands inserts into the calixarene cavity as displayed in Fig. 24B.



Figure 24. (A) Ball and stick depiction of p-sulfonatocalix<4>arene molecules in between two dinuclear oxo-bridged iron(III) phenanthroline complexes. (B) Tris(1,10-phenanthroline) Ni(II) complex partly included in the calixarene cavity.122 H atoms omitted for clarity.


Binding of Nd3 + and also Eu3 + by two 1,10-phenanthroline molecules in the visibility of p-sulfonatocalix<4>arene outcomes in 3D metal-organic-frameworks (Fig. 25).119 Each calix<4>arene is rotated by 90 degrees, offering climb to parallel packing in a tetrameric cyclic array. The coordination spbelow of each octa-coordinate lanthanide center is completed by oxygen atoms from four calixarene sulfonato groups. Each calixarene connects four various lanthanide centers in the extended framework.



Figure 25. Three-dimensional lanthanide/p-sulfonatocalix<4>arene/1,10-phenanthroline metal-organic-framework.119 H atoms omitted for clarity.


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Separation, Preconcentration and also Spectrophotomeattempt in Inorganic Analysis


Zygmunt Marczenko, Maria Balcerzak, in Analytical Spectroscopy Library, 2000

26.2.2.1,10-Phenanthroline method

1,10-Phenanthroline (phen, formula 26.1 ) and 2,2'-bipyridyl (formula 26.2) are organic bases through exceptionally similar chemical properties.


(26.1)
(26.2)

Both reagents react promptly through Fe2 + ions in weakly acid media to offer orange-red or pink complexes, respectively, which are a basis for determining Fe(II) <27,28>. The absorption spectra of both complexes are displayed in Fig. 26.1.



Fig. 26.1. Absorption spectra of the iron complexes: iron(II) – 1,10-phenanthroline (1), iron(III) – 1,10-phenanthroline (2), and also iron(II) – 2,2'-bipyridyl (3).


The molar absorptivity of the Fe(II) complicated via 1,10-phenanthroline is 1.10 · 104 (a = 0.20) at λmax 512 nm, and that of the facility with 2,2'-bipyridyl is 8.7-103 at λmax 522 nm. Solutions of the complexes with phenanthroline and bipyridyl are secure, and the Fe(II) bound in the complicated is resistant to oxidation.

Iron(II) and also total iron deserve to be established through phenanthroline or bipyridyl after reduction of Fe(in) to Fe(II). Hydroxylamine reduces Fe(III) within a couple of minutes in a weakly acidic tool (pH 3–4): ascorbic acid is a better reductant in a reasonably acidic solution (pH 0–1). Other reducing agents supplied are sulphite, dithionite, and also hypophosphite <28>.

The colour reactions are usually brought out in acetate or citprice buffers. The presence of citrate or tartprice is preferable as it stays clear of the precipitation of specific cations which hydrolyse in weak acid media (e.g., Ti, Al, and also Bi). In the determination of Fe(II) through phenanthroline, Fe(III) have the right to be masked with NTA <29> or fluoride <30>.

The complicated of 1,10-phenanthroline through Fe(II) is dubbed ferroin and has been widely supplied in titrimetric evaluation as a redox indicator .

1,10-Phenanthroline forms via Fe(III) a blue complicated (λmax 585 nm) which has actually been used for determining larger quantities of iron.

Phenanthroline and also 2,2'-bipyridyl create complexes, although not intensely coloured, through Ru, Os, and Cu(I). Many kind of metals (e.g., Zn and also Cd) deserve to create colourless complexes through phenanthroline and also bipyridyl, which are more secure than the equivalent Fe(II) complexes. When determining Fe in the presence of Zn or Cd, EDTA should be offered as a masking agent <31>. Copper can be masked with triethylenetetramine <32>.

Fe(II)– complexes via phenanthroline and 2,2'-bipyridyl form extractable ion-associates, e.g.,via nitroprusside <33>, tetraphenylborate <34>, or picprice <35>. Fe has actually been figured out by derivative spectrophotomeattempt, after extraction of the ferroin associate through perchloprice anion <36>.

The 1,10-phenanthroline method has actually been offered in the automatic FIA method <37–40>.

Reagents

1,10-Phenanthroline (phen), 0.2% solution of the hydrochloride or hydprice in -0.1 MHC1. Standard iron solution: 1 mg/ml. Preparation as in Section 26.2.1. Hydroxylamine hydrochloride, 10% solution, freshly prepared.

Procedure

To a slightly acid solution, containing not even more than 80 μg of Fe(III) or Fe(II), add 1 ml of the NH2OH solution and 10% sodium citrate solution, till the pH is 3-4. Transfer the solution to a 25-ml conventional flask, add 3 ml of the phen solution, dilute to the mark with water, and mix thoroughly. After 5 min, meacertain the absorbance of the solution at 512 nm versus water.


Procedure.

Accurately weigh about 10 mg of the carefully powdered silicate product into a dry polyethylene bottle and a similar amount of the referral sample right into a second bottle. Use a third bottle for the referral empty solution. Add around 20 mg of the 1,10-phenanthroline to each adhered to by 3 ml of 4 N sulphuric acid and also 0.5 ml of focused hydrofluoric acid. Transfer the bottles to a heavy steam bath in a fixed order, so that the first one on will certainly be the initially off, and leave for 30 minutes.

While the bottles are on the steam bath, transport 5 ml of the boric acid solution to each of a series of 100-ml volumetric flasks. Using the same order as previously, rerelocate the bottles from the vapor bath and also, as swiftly as feasible, add 20 ml of sodium citprice solution to each bottle. As far as feasible each bottle must be left on the steam bath for the very same size of time. Transfer the contents of each bottle to among the 100-ml volumetric flasks, using water to rinse the bottles. Cool to room temperature, dilute each solution to volume via water and also mix well.

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Using a spectrophotometer set at wavelengths of 555 nm and 640 nm, meacertain the optical densities of the solutions using the empty as the recommendation solution. For each solution, subtract the optical density at 640 nm from that obtained at 555 nm, and recognize the ferrous iron content of the sample by recommendation to the optical thickness difference obtained for the silicate rock of recognized ferrous iron content.