Stability Orders in Transition Metal-1,10-Phenanthroline Complexes<sup>1</sup>

Banks, Charles V.; Bystroff, R.I.

doi:10.1021/ja01532a013

Cited by 65 publications

(37 citation statements)

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“…A similar representation of log K1 plotted against pK, shows the same trend except that the relative positions of iron (11) and copper are different. As has been noted elsewhere (1,12) the large 03 of the iron (11) complexes resides mainly in the abnormally large K3. Copper (11), on the other hand, shows a large K 1 (see the Irving-Williams order of stability) but this is not carried over into the P3 owing to the reluctance on the part of copper to accept ligands beyond a coordination number of four.…”

Section: Resultssupporting

confidence: 56%

“…A number of studies t o determine the stability of metal complexes of the phenanthrolines have been published (1)(2)(3)(4)(5)(6)(7)(8), among the most complete of which are those of Irving and co-workers (2,4). In an extension of these studies the present investigation has sought formation curves, and hence formation constants, for the complexes formed by 5,6-and 4,7-dimethyl-1,lO-phenanthroline with a selected group of ions of the first transition series.…”

mentioning

confidence: 99%

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The Stability of Metallic Complexes of Two Dimethylphenanthrolines

Brisbin¹,

McBryde²

1963

Can. J. Chem.

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The stepwise formation constants for the complexes formed by 5,6-dimethyl-and 4,7-dimethyl-1,lO-phenanthroline with bivalent iron, cobalt, nickel, copper, and zinc were determined by a partition method. The measurements were made a t 25' C and in aqueous solutions having an ionic strength maintained a t 0.1. The enhanced basicity of the ligands compared to the parent phenanthroline is paralleled by increased stability of the metallic complexes. The abnormally, high formation constants of the cobalt complexes suggest oxidation to cobalt (111).A number of studies t o determine the stability of metal complexes of the phenanthrolines have been published (1-8), among the most complete of which are those of Irving and co-workers (2, 4). In an extension of these studies the present investigation has sought formation curves, and hence formation constants, for the complexes formed by 5,6-and 4,7-dimethyl-1,lO-phenanthroline with a selected group of ions of the first transition series.The inductive effect of substituent methyl groups in increasing the basic strength of phenanthroline is apparent from the data of the following table: From these data it is seen that the basic strength of these compounds is enhanced by the presence of each methyl group in the conjugated ring system, and that the extent of this enhancement is related to the propinquity of the methyl groups t o the nitrogen atoms. In agreement with expectations, the increased basicity of the compounds investigated is paralleled by an increase in stability of the complexes investigated except, as noted elsewhere, when steric hindrance t o coordination about the metal atom occurs (5). The experimental method used was based on partition of the ligand between an aqueous solution and a solvent immiscible with water. The principle of the method is old, but its extension to the study of formation of complexes involving stepwise equilibria was first suggested by Kolthoff et al. (9), and subsequently extended and refined by Irving and co-workers (2). A measured volume of a solution of the ligand of known concentration in a selected solvent was shaken with a measured volume of aqueous solution containing

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Section: Resultssupporting

confidence: 56%

mentioning

confidence: 99%

The Stability of Metallic Complexes of Two Dimethylphenanthrolines

Brisbin¹,

McBryde²

1963

Can. J. Chem.

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“…Phenanthroline was employed in preference to the commonly employed Fe(II) colorimetric agent ferrozine since, at low pH, ferrozine can induce the reduction of Fe(III) and therefore interfere with the reliable measurement of Fe(II) (Anastacio et al, 2008). Furthermore, phenanthroline can be used to quantify the concentration of Fe(II) in the presence of EDTA and citrate, with no interference due to complex formation (Wang et al, 2013) and forms an extremely stable Fe(II) complex with a stability constant of 10 21.3 (Banks & Bystroff, 1959); stronger than that of Fe(II)-EDTA (Morel & Hering, 1993). In the presence of SRFA, multiple background measurements were performed in the presence of phenanthroline and averaged to account for the absorbance of SRFA alone.…”

Section: Analysis Of Fe(ii)mentioning

confidence: 99%

Ferrous iron oxidation by molecular oxygen under acidic conditions: The effect of citrate, EDTA and fulvic acid

Jones

Griffin

Waite

2015

Geochimica et Cosmochimica Acta

112

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“…On the basis of a pK a of 1.12, at pH 5, g99.99% of the complex is present as Ru(bpy) 2 (dpp) 2+ , and the emission spectrum consists of only the 705 nm emission from the unprotonated complex. Taking the quantum efficiency of emission from room temperature, 22 ( 1°C, N 2 saturated, aqueous solutions of Ru(bpy) 3 2+ in water (6) to be 0.0429 (averaged from several references 18 ), the gradient method using a series of concentrations e0.10M 11 yields 1.98 ( 0.20 × 10 -3 as the quantum efficiency of the 705 nm emission from the unprotonated complex Ru(bpy) 2 (dpp) 2+ , designated Φ em u . The 735 nm emission from the protonated complex was then measured from a deaerated, aqueous solution containing the same concentration of Ru(bpy) 2 (dpp) 2+ but 1.0 M in HNO 3 .…”

Section: Nm Emissionmentioning

confidence: 99%

“…Taking the quantum efficiency of emission from room temperature, 22 ( 1°C, N 2 saturated, aqueous solutions of Ru(bpy) 3 2+ in water (6) to be 0.0429 (averaged from several references 18 ), the gradient method using a series of concentrations e0.10M 11 yields 1.98 ( 0.20 × 10 -3 as the quantum efficiency of the 705 nm emission from the unprotonated complex Ru(bpy) 2 (dpp) 2+ , designated Φ em u . The 735 nm emission from the protonated complex was then measured from a deaerated, aqueous solution containing the same concentration of Ru(bpy) 2 (dpp) 2+ but 1.0 M in HNO 3 . With 1 M HNO 3 , g93% of the complex is present as the protonated complex, Ru(bpy) 2 (dppH) 3+ , and the emission spectrum consists of the 620 and 735 nm emissions from the protonated complex.…”

Section: Nm Emissionmentioning

confidence: 99%

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

2009

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The proton dependencies of the absorption and emission spectra of bis(2,2′-bipyridyl)(2,3-bis(2-pyridyl)pyrazine)ruthenium(II), (bpy) 2 Ru(dpp) 2+ indicate that population of the dpp-localized MLCT state increases the basicity of dpp peripheral nitrogens. NMR spectra reveal the protonation of the peripheral dpp pyridine in the ground state, pK a of 1.12 ( 0.03, occurs intermediate between the changes evident in the absorption and emission spectra. As a result, the emissivity of aqueous solutions of (bpy) 2 Ru(dpp) 2+ as a function of [H + ] derives from two emissive species: the unprotonated complex and the monoprotonated complex [(bpy) 2 Ru(dppH py )] 3+ with the proton attached to the peripheral dpp pyridine. Although protonation in the MLCT state generally quenches the emission, the emissivity of the monoprotonated complex, albeit weak, is attributed to the asymmetric distribution of the charge in the MLCT state. The majority of the transferred charge resides at the peripheral pyrazinyl nitrogen, and excited-state acid-base chemistry occurs predominantly at this site. Nonetheless, ground-state protonation of the peripheral dpp pyridine dramatically increases the nonradiative decay rate and significantly influences subsequent excited-state protonation processes. Protonation of the excited state changes from a bimolecular process to a combination of inter-and intramolecular processes where the proton transfers from the dpp pyridyl nitrogen to the dpp pyrazinyl nitrogen and from the surrounding aqueous solvent shell. Energetically, changes in the absorption spectra originally attributed to the first protonation of the complex and from which the ∆pK a of the excited state have been estimated, in fact, correspond to the second protonation of the complex. IntroductionThe hydrogen ion dependencies of the absorption and emission spectra of Ru(II) diimines reveal substantial differences in the acid-base properties of the ground and emissive MLCT states of the complexes. 1 Depending on the direction of the charge transfer relative to the acid-base site, and the location of the acceptor orbital in the MLCT state, excitation changes electron distribution, which in turn increases or decreases acid-base properties by as much as 5 to 6 orders of magnitude. 2 Brønsted basicity usually does not correlate with the coordinating ability of a ligand, but, with diimine ligands, the equilibrium constant for coordination increases linearly with the Brønsted basicity of the ligand's coordinating nitrogens. 3 Work in this laboratory focuses on whether these photoinduced changes in acid-base properties translate into an excited-state coordination chemistry where a Ru(II) diimine possessing one or more acid-base sites on the ligand periphery functions as a ligand and whether excitation enhances or reduces its ability to coordinate to another metal.Excited-state coordination chemistry arises from the observation that excitation of bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II), (bpy) 2 Ru(dpp) 2+ , in the presence of PtCl 6

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Stability Orders in Transition Metal-1,10-Phenanthroline Complexes¹

Cited by 65 publications

References 0 publications

The Stability of Metallic Complexes of Two Dimethylphenanthrolines

The Stability of Metallic Complexes of Two Dimethylphenanthrolines

Ferrous iron oxidation by molecular oxygen under acidic conditions: The effect of citrate, EDTA and fulvic acid

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

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Stability Orders in Transition Metal-1,10-Phenanthroline Complexes1

Cited by 65 publications

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The Stability of Metallic Complexes of Two Dimethylphenanthrolines

The Stability of Metallic Complexes of Two Dimethylphenanthrolines

Ferrous iron oxidation by molecular oxygen under acidic conditions: The effect of citrate, EDTA and fulvic acid

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

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Stability Orders in Transition Metal-1,10-Phenanthroline Complexes¹