Orthophenanthrolines

REDOX POTENTIALS OF RELATIVELY WEAK ONE-EQUIVALENT OXIDANTS (phen) = 1,10-orthophenanthroline. 

Note phen is 1, 10 orthophenanthroline. Note the change to low-spin, paired d electron, states gains tr-acceptor and /r-donoi strength offsetting spin-pairing energy. 

Certain orthophenanthrolines may be used instead of 1,10-phenanthroline. These include 5-nitro-l,10-phenanthroline, Erioglaucin A, and p-ethoxychiysoidine which form iron-II complexes of violet-red, yellow-green, and red colors, respectively. 

Assay With the aid of about 25 mL of water, transfer about 125 mg of sample, accurately weighed, into a 300-mL Erlen-meyer flask. Add 50.0 mL of 0.5 N potassium dichromate, mix, then carefully add 100 mL of sulfuric acid, and heat to boiling. Remove the mixture from the heat, allow it to stand at room temperature for 15 min, cool it in a water bath, and transfer it into a 250-mL volumetric flask. Dilute almost to volume with water, cool to 25°, then dilute to volume with water, and mix. Titrate a 50.0-mL aliquot with 0.1 iV ferrous ammonium sulfate, using 2 or 3 drops of orthophenanthroline TS as the indicator, and record the volume required, in milliliters, as S. Perform a blank determination (see General Provisions), and record the volume of 0.1 N ferrous ammonium sulfate required, in milliliters, as B. Calculate the percent cellulose in the sample by the formula... 

Assay Dissolve about 0.4 g of sample, accurately weighed, in 20 mL of 16 100 sulfuric acid, add 5 mL of 85% phosphoric acid, dilute with approximately 50 mL of water, and immediately titrate with 0.1 N ceric sulfate, using orthophenanthroline TS as the indicator. Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1 N ceric sulfate is equivalent to 5.585 mg of Fe. Chloride Heat 100 mg of sample, accurately weighed, with 25 mL of water and 2 mL of nitric acid until the sample dissolves. Cool, dilute to 100 mL with water, and mix. Take 10 mL of this solution, and dilute to 30 to 40 mL with water. Proceed as directed in the Chloride Limit Test under Chloride and Sulfate Limit Tests, Appendix IIIB, beginning with add 1 mL of silver nitrate TS... . Any turbidity produced does not exceed that shown in a control containing 20 pig of chloride (Cl). 

Assay Transfer about 500 mg of sample, accurately weighed, into a 500-mL Erlenmeyer flask, add 25 mL of 2 5 hydrochloric acid, and heat to boiling. Add, dropwise, a solution of 5.6 g of stannous chloride in 50 mL of 3 10 hydrochloric acid until the yellow color disappears, and then add 2 drops in excess. Cool the solution in an ice bath to room temperature, add 8 mL of mercuric chloride TS, and allow to stand for 5 min. Add 200 mL of water, 25 mL of 1 2 sulfuric acid, and 4 mL of phosphoric acid then add orthophenanthroline TS and titrate with 0.1 A ceric sulfate. Each milliliter of 0.1 A ceric sulfate is equivalent to 16.99 mg of C4H2Fe04. 

Assay Dissolve about 1.5 g of sample, accurately weighed, in a mixture of 75 mL of water and 15 mL of 2 IV sulfuric acid in a 300-mL Erlenmeyer flask, and add 250 mg of zinc dust. Close the flask with a stopper containing a Bunsen valve, allow to stand at room temperature for 20 min, then filter through a sintered-glass filter crucible containing a thin layer of zinc dust, and wash the crucible and contents with 10 mL of 2 N sulfuric acid, followed by 10 mL of water. Add orthophenanthroline TS, and titrate the filtrate in the suction flask immediately with 0.1 A ceric sulfate. Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1IV ceric sulfate is equivalent to 44.62 mg of C E FeO. ... 

Assay Dissolve about 100 mg of sample, accurately weighed, in 20 mL of water add 40.0 mL of 0.1 N ceric sulfate prepared as directed for Volumetric Solutions under Solutions and Indicators (or use a commercially available solution) mix well and add 2 mL of silver sulfate solution (5 g of Ag2S04 dissolved in 95 mL of concentrated sulfuric acid). Cover, heat nearly to boiling, and continue heating for 30 min. Cool to room temperature, and titrate with 0.1 A ferrous ammonium sulfate to a pale yellow color. Add 2 drops of orthophenanthroline TS, and continue the titration to a salmon-colored endpoint, recording the volume required, in milliliters, as S. Perform a residual blank titration (see General Provisions), and record the volume required as B. Each milliliter of the volume B - S is equivalent to 2.650 mg of NaH2P02H20. 

Orthophenanthroline TS Dissolve 150 mg of orthophen-anthroline (C12H8N2-H20) in 10 mL of a solution of ferrous sulfate, prepared by dissolving 700 mg of clear crystals of ferrous sulfate (FeS04-7H20) in 100 mL of water. The ferrous sulfate solution must be prepared immediately before dissolving the orthophenanthroline. Store the solution in well-closed containers. 

Ferrous Ammonium Sulfate, 0.1 N [39.21 g Fe(NH4)2-(S04)2-6H20 per 1000 mL] Dissolve 40 g of ferrous ammonium sulfate hexahydrate in a previously cooled mixture of 40 mL of sulfuric acid and 200 mL of water, dilute to 1000 mL with water, and mix. On the day of use, standardize the solution as follows Transfer from 25 to 30 mL of the solution, accurately measured, into a flask, add 2 drops of Orthophenanthroline TS, and titrate with 0.1 N Ceric Sulfate until the red color is changed to pale blue. From the volume of 0.1 N Ceric Sulfate consumed, calculate the normality. 

Dipyridyl and orthophenanthroline form particularly stable complexes with iron. The octahedral [Fe(phcn)3] + ion (Fig. 2C4) is blood-red but is oxidised to pale blue [Fe(phen)3] without any structural change. for the system = 1.14 V, making the compound, also known as ferroin, a most useful redox indicator for the oxidation of Fe + ion Fe +/Fe + = 0.77 V) by cerium(IV) ion (E Ce +/Ce + = 1.45 V). 

This paper reports the results of investigations of the complex formation between actinide or lanthanide ions and azide or orthophenanthroline. The aim of this work was first to confirm whether these relatively soft ligands give complexes of different stabilities with the trivalent lanthanide and actinide ions, as a consequence of the broader extension of 5f orbitals as compared with 4f. Secondly, we attempted to use the results in actinide chemical separation processes. 

Orthophenanthroline complexes. As azides exhibit greater chemical affinity for trivalent actinide ions, we tried to check this behavior with a bidentate ligand. We chose 1-10 ghenantro-line which has two nitrogen donors at 2.75 A from each... 

We studied the complexes of lanthanides and Am (III] by potentiometry. This method is based on pH variations due to the competition between H+ and the metal ions for the coordination site of orthophenanthroline (pka - 5.2], as shown by equation (4]. 

The calculation results are shown in table II. We also report formation constants determined from spectrophotometry for Ho and Nd, and by solvent extraction for Er. Without going into detail for these two methods, it may be noted that the results show fair agreement. That fact points out the inner sphere character of orthophenanthrolinium lanthanous complexes. The main absorption band of Am (III] is modified by the presence of orthophenanthroline. We used these spectral variations to calculate the formation constants of Am (III], as described in the previous paragraph. As for azide complexes, we observed that Am monoorthophe-nanthroline is more stable than the equivalent lanthanide complex, and for the bis orthophenanthroline species, the difference... 

For this purpose it was necessary to have, in the organic phase, a reagent able to neutralize the tripositive charge of the orthophenanthroline metallic species. We chose nonanoic acid which has poor solubility in aqueous phases. Nitrobenzene is suitable as a diluent because it solubilizes orthophenanthroline. The results of Eu [III] and Am (III) extraction in the nitrobenzene/ortho-phenanthroline/nonaoic acid mixture are given in Table III. 

At the working pH orthophenanthroline is present mostly in the organic phase and its higher affinity for Am (III)ions is shown by the higher distribution coefficients. Without orthophenanthroline Am (III) and Eu(III) ions are not extracted in the mixture nonaoic acid, nitrobenzene. 

A class of organic compounds known as 1,10-phenanthrolines, or orthophenanthrolines, form stable complexes with iron(II) and certain other ions. The parent compound has a pair of nitrogen atoms located in such positions that each can form a covalent bond with the iron(II) ion. 

Three orthophenanthroline molecules combine with each iron ion to yield a complex with the structure shown in the margin. 

Using a titrimetric iron determination with titanous chloride, Remmer (R3) obtained for e N a value of 11.09 as an average of 11 determinations. Minkowski (M7) found t N = 11.15, using a spectrophotometric method involving the use of orthophenanthroline. These values are in fair agreement with our results (see Section 2.1.5 and Table 2). An indirect proof of cn =... 

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