Substitution reactions of metallic complexes of .beta.,.beta.',.beta.''-triaminotriethylamine. 11. Kinetics of the stepwise hydrolysis and ligand field photolysis of the difluoro(.beta.,.beta.',.beta.''-triaminotriethylamine)chromium(III) cation

Saliby, Michael J.; Sheridan, Peter S.; Madan, Stanley K.

doi:10.1021/ic50207a036

Cited by 14 publications

(3 citation statements)

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“…The study of the Cr(tn) x (NH 3 ) 6 - 2 x 3+ series 82 also indicated that ligand loss from the plane of excitation is competitive, i.e., the presence of an ammonia ligand in the plane of labilization reduced photoaquation of tn from the same plane. An even worse leaving ligand is cyclam, and Table shows that that cis- Cr(cyclam)F 2 + also aquates fluoride efficiently as does an earlier example Cr(tren)F 2 + . In contrast, the trans- Cr(tet-a)F 2 + complex with its sterically rigid in-plane N 4 coordination is photoinert …”

Section: Photochemical Reaction Patternsmentioning

confidence: 94%

Photochemistry and Photophysics of Chromium(III) Complexes

1999

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Section: Photochemical Reaction Patternsmentioning

confidence: 94%

Photochemistry and Photophysics of Chromium(III) Complexes

1999

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“…(dppe), and Ni(COD)2 (COD is 1,5-cylooctadiene) were purchased from Strem Chemicals. The acetonitrile complexes of Fe, Co, and Ni were prepared as described in ref 9.…”

Section: Methodsmentioning

confidence: 99%

Synthesis, characterization, and electrochemical studies of iron, cobalt, and nickel complexes of polyphosphine ligands

DuBois

Miedaner

1986

Inorg. Chem.

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with the result that the C-Mo-OH2 angles are significantly smaller than 90°. On the other hand, this distortion in the [WO-(H20)(CN)4]1 2" ion together with the large trans effect of the oxo ligand, will promote dissociation of the aquo ligand and thus a dissociative reaction mode. This is in agreement with the positive value of isV*(k•^. The large trans influence of the oxo ligand is clearly observed in the Mo-N bond distances in [MoO(Phen)-(CN)3]~6 (the corresponding tungsten complex is isomorphous with the molybdenum complex): The Mo-N bond distance trans to the oxo ligand is 2.363 (7) Á, whereas the Mo-N bond distance trans to the cyanide ligand is only 2.174 (7) Á.Finally, the results of this investigation clearly demonstrate the close correlation between ground-state structure and transitionstate energetics as facilitated by the trans effect of the oxo ligand.Acknowledgment The authors gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft, Fonds der Chemischen Industrie, the S.A. Council for Scientific and Industrial Research, and the Research Fund of the University of the Orange Free State.Registry No. irons-[WO^CN^]4", 42720-52-5; irons-[W0(H20)-(CN)4]2", 105121-19-5; Nf, 14343-69-2.

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“…Early work by Kutal, , Kane-Maguire, , and co-workers showed that a number of Cr(III) trans -cyclam complexes were photoinert, and this was attributed to the effect of steric rigidity on access to the photochemical channels of excited-state decay. In other studies it has been found , that reaction pathways can be modified by steric factors associated with the presence of multidentate ligands. This area has advanced sufficiently to hold out promise that such effects of ligand constraints may be usefully employed to alter and control photochemical behavior including the ability to design photochemically inert, luminescent complexes.…”

Section: Introductionmentioning

confidence: 91%

Photochemistry and Photophysics of Cr(III) Macrocyclic Complexes

2002

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The phosphorescence and photochemical behavior of the macrocyclic complexes (1,4,7,10,13,16-hexaazacyclooctadecane)chromium(III) (Cr([18]-aneN(6))(3+); 1) and (4,4',4''-ethylidynetris(3-azabutan-1-amine)) chromium(III) (Cr(sen)(3+); 2) have been compared to each other and to the complex Cr(en)(3)(3+). For both macrocyclic complexes, phosphorescence from room temperature aqueous solutions is too weak to be observed, contrasting with Cr(en)(3)(3+), though both had somewhat longer 77 K lifetimes than Cr(en)(3)(3+). Phosphorescence lifetimes for these macrocyclics decreased with increasing temperature much faster than for Cr(en)(3)(3+) and a conventional extrapolation based on a fit of reciprocal lifetimes (corrected for the low-temperature contribution) to the Arrhenius equation gave estimated room temperature phosphorescence lifetimes of a few nanoseconds, consistent with the failure to observe room temperature emission. Fitting of the nonlinearity of the data seen in these plots suggested that two high-temperature processes were occurring with estimated activation parameters (E in kJ mol(-1) and A in s(-1)) for Cr([18]-aneN(6))(3+): E(1) = 40, A(1) = 1 x 10(16); E(2) = 24, A(2) = 1 x 10(14): Cr(sen)(3+); E(1) = 45, A(1) = 2 x 10(15); E(2) = 29, A(2) = 7 x 10(11). Cr([18]-aneN(6))(3+) was photochemically inert on irradiation. On irradiation into the lowest quartet ligand field absorption band, Cr(sen)(3+) photolyzes with a quantum yield of 0.098 +/- 0.001 at room temperature. Laser flash photolysis with conductivity detection showed that this photoreaction occurred faster than protonation of the liberated amine ligand at all practical proton concentrations. The quantum yield for irradiation directly into the doublet absorption band of Cr(sen)(3+) was 0.077 +/- 0.003. Photoaquation of Delta-Cr(sen)(3+) led to loss of optical activity and product analysis by capillary electrophoresis showed that both racemic and Delta-Cr(sen)(3+) photoaquate to a single main product, trans-Cr(sen-NH)(H(2)O)(4+). The product stereochemistry is shown to be consistent with predictions based on the angular overlap model for Cr(III) photochemistry, recognizing the additional constraints imposed by the ligand. The abnormally short room temperature solution lifetime of the doublet state is a result of a radiation-less process that competes with other processes depleting the doublet state. However, this doublet-state deactivation process does not lead to photoaquation but competes with BISC and photoaquation via the quartet state, resulting in an unprecedented reduction in photoaquation quantum yield on direct irradiation into the doublet state.

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Substitution reactions of metallic complexes of .beta.,.beta.',.beta.''-triaminotriethylamine. 11. Kinetics of the stepwise hydrolysis and ligand field photolysis of the difluoro(.beta.,.beta.',.beta.''-triaminotriethylamine)chromium(III) cation

Cited by 14 publications

References 4 publications

Photochemistry and Photophysics of Chromium(III) Complexes

Photochemistry and Photophysics of Chromium(III) Complexes

Synthesis, characterization, and electrochemical studies of iron, cobalt, and nickel complexes of polyphosphine ligands

Photochemistry and Photophysics of Cr(III) Macrocyclic Complexes

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